From b419d8e8478acf39d5d2eff55364ee6d4e71074c Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:16:08 +0200 Subject: [PATCH 01/27] Add S7CommPlus protocol scaffolding for S7-1200/1500 support Adds the snap7.s7commplus package as a foundation for future S7CommPlus protocol support, targeting all S7-1200/1500 PLCs (V1/V2/V3/TLS). Includes: - Protocol constants (opcodes, function codes, data types, element IDs) - VLQ encoding/decoding (Variable-Length Quantity, the S7CommPlus wire format) - Codec for frame headers, request/response headers, and typed values - Connection skeleton with multi-version support (V1/V2/V3/TLS) - Client stub with symbolic variable access API - 86 passing tests for VLQ and codec modules The wire protocol (VLQ, data types, object model) is the same across all protocol versions -- only the session authentication layer differs. The protocol version is auto-detected from the PLC's CreateObject response. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/__init__.py | 36 ++++ snap7/s7commplus/client.py | 257 +++++++++++++++++++++++++ snap7/s7commplus/codec.py | 292 ++++++++++++++++++++++++++++ snap7/s7commplus/connection.py | 249 ++++++++++++++++++++++++ snap7/s7commplus/protocol.py | 176 +++++++++++++++++ snap7/s7commplus/vlq.py | 337 +++++++++++++++++++++++++++++++++ tests/test_s7commplus_codec.py | 173 +++++++++++++++++ tests/test_s7commplus_vlq.py | 161 ++++++++++++++++ 8 files changed, 1681 insertions(+) create mode 100644 snap7/s7commplus/__init__.py create mode 100644 snap7/s7commplus/client.py create mode 100644 snap7/s7commplus/codec.py create mode 100644 snap7/s7commplus/connection.py create mode 100644 snap7/s7commplus/protocol.py create mode 100644 snap7/s7commplus/vlq.py create mode 100644 tests/test_s7commplus_codec.py create mode 100644 tests/test_s7commplus_vlq.py diff --git a/snap7/s7commplus/__init__.py b/snap7/s7commplus/__init__.py new file mode 100644 index 00000000..3617a832 --- /dev/null +++ b/snap7/s7commplus/__init__.py @@ -0,0 +1,36 @@ +""" +S7CommPlus protocol implementation for S7-1200/1500 PLCs. + +S7CommPlus (protocol ID 0x72) is the successor to S7comm (protocol ID 0x32), +used by Siemens S7-1200 (firmware >= V4.0) and S7-1500 PLCs for full +engineering access (program download/upload, symbolic addressing, etc.). + +Supported PLC / firmware targets:: + + V1: S7-1200 FW V4.0+ (trivial anti-replay) + V2: S7-1200/1500 older FW (proprietary session auth) + V3: S7-1200/1500 pre-TIA V17 (ECC key exchange) + V3 + TLS: TIA Portal V17+ (TLS 1.3 with per-device certs) + +Protocol stack:: + + +-------------------------------+ + | S7CommPlus (Protocol ID 0x72)| + +-------------------------------+ + | TLS 1.3 (optional, V17+) | + +-------------------------------+ + | COTP (ISO 8073) | + +-------------------------------+ + | TPKT (RFC 1006) | + +-------------------------------+ + | TCP (port 102) | + +-------------------------------+ + +The wire protocol (VLQ encoding, data types, function codes, object model) +is the same across all versions -- only the session authentication differs. + +Status: experimental scaffolding -- not yet functional. + +Reference implementation: + https://github.com/thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) +""" diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py new file mode 100644 index 00000000..988bbd31 --- /dev/null +++ b/snap7/s7commplus/client.py @@ -0,0 +1,257 @@ +""" +S7CommPlus client for S7-1200/1500 PLCs. + +Provides high-level operations over the S7CommPlus protocol, similar to +the existing snap7.Client but targeting S7-1200/1500 PLCs with full +engineering access (symbolic addressing, optimized data blocks, etc.). + +Supports all S7CommPlus protocol versions (V1/V2/V3/TLS). The protocol +version is auto-detected from the PLC's CreateObject response during +connection setup. + +Status: experimental scaffolding -- not yet functional. +All methods raise NotImplementedError with guidance on what needs to be done. + +Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) +""" + +import logging +from typing import Any, Optional + +from .connection import S7CommPlusConnection + +logger = logging.getLogger(__name__) + + +class S7CommPlusClient: + """S7CommPlus client for S7-1200/1500 PLCs. + + Supports all S7CommPlus protocol versions: + - V1: S7-1200 FW V4.0+ + - V2: S7-1200/1500 with older firmware + - V3: S7-1200/1500 pre-TIA Portal V17 + - V3 + TLS: TIA Portal V17+ (recommended) + + The protocol version is auto-detected during connection. + + Example (future, once implemented):: + + client = S7CommPlusClient() + client.connect("192.168.1.10") + value = client.read_variable("DB1.myVariable") + client.disconnect() + """ + + def __init__(self) -> None: + self._connection: Optional[S7CommPlusConnection] = None + + @property + def connected(self) -> bool: + return self._connection is not None and self._connection.connected + + def connect( + self, + host: str, + port: int = 102, + rack: int = 0, + slot: int = 1, + tls_cert: Optional[str] = None, + tls_key: Optional[str] = None, + tls_ca: Optional[str] = None, + ) -> None: + """Connect to an S7-1200/1500 PLC using S7CommPlus. + + Args: + host: PLC IP address or hostname + port: TCP port (default 102) + rack: PLC rack number + slot: PLC slot number + tls_cert: Path to client TLS certificate (PEM) + tls_key: Path to client private key (PEM) + tls_ca: Path to CA certificate for PLC verification (PEM) + + Raises: + NotImplementedError: S7CommPlus connection is not yet implemented + """ + local_tsap = 0x0100 + remote_tsap = 0x0100 | (rack << 5) | slot + + self._connection = S7CommPlusConnection( + host=host, + port=port, + local_tsap=local_tsap, + remote_tsap=remote_tsap, + ) + + self._connection.connect( + tls_cert=tls_cert, + tls_key=tls_key, + tls_ca=tls_ca, + ) + + def disconnect(self) -> None: + """Disconnect from PLC.""" + if self._connection: + self._connection.disconnect() + self._connection = None + + # -- Explore (browse PLC object tree) -- + + def explore(self, object_id: int = 0) -> dict[str, Any]: + """Browse the PLC object tree. + + The Explore function is used to discover the structure of data + blocks, variable names, types, and addresses in the PLC. + + Args: + object_id: Root object ID to start exploring from. + 0 = root of the PLC object tree. + + Returns: + Dictionary describing the object tree structure. + + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build ExploreRequest, send, parse ExploreResponse + # This is the key operation for discovering symbolic addresses. + raise NotImplementedError("explore() is not yet implemented") + + # -- Variable read/write -- + + def read_variable(self, address: str) -> Any: + """Read a single PLC variable by symbolic address. + + S7CommPlus supports symbolic access to variables in optimized + data blocks, e.g. "DB1.myStruct.myField". + + Args: + address: Symbolic variable address + + Returns: + Variable value (type depends on PLC variable type) + + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Resolve symbolic address -> numeric address via Explore + # TODO: Build GetMultiVariables request + raise NotImplementedError("read_variable() is not yet implemented") + + def write_variable(self, address: str, value: Any) -> None: + """Write a single PLC variable by symbolic address. + + Args: + address: Symbolic variable address + value: Value to write + + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Resolve address, build SetMultiVariables request + raise NotImplementedError("write_variable() is not yet implemented") + + def read_variables(self, addresses: list[str]) -> dict[str, Any]: + """Read multiple PLC variables in a single request. + + Args: + addresses: List of symbolic variable addresses + + Returns: + Dictionary mapping address -> value + + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build GetMultiVariables with multiple items + raise NotImplementedError("read_variables() is not yet implemented") + + def write_variables(self, values: dict[str, Any]) -> None: + """Write multiple PLC variables in a single request. + + Args: + values: Dictionary mapping address -> value + + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build SetMultiVariables with multiple items + raise NotImplementedError("write_variables() is not yet implemented") + + # -- PLC control -- + + def get_cpu_state(self) -> str: + """Get the current CPU operational state. + + Returns: + CPU state string (e.g. "Run", "Stop") + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("get_cpu_state() is not yet implemented") + + def plc_start(self) -> None: + """Start PLC execution. + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("plc_start() is not yet implemented") + + def plc_stop(self) -> None: + """Stop PLC execution. + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("plc_stop() is not yet implemented") + + # -- Block operations -- + + def list_blocks(self) -> dict[str, list[int]]: + """List all blocks in the PLC. + + Returns: + Dictionary mapping block type -> list of block numbers + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("list_blocks() is not yet implemented") + + def upload_block(self, block_type: str, block_number: int) -> bytes: + """Upload (read) a block from the PLC. + + Args: + block_type: Block type ("OB", "FB", "FC", "DB") + block_number: Block number + + Returns: + Block data + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("upload_block() is not yet implemented") + + def download_block(self, block_type: str, block_number: int, data: bytes) -> None: + """Download (write) a block to the PLC. + + Args: + block_type: Block type ("OB", "FB", "FC", "DB") + block_number: Block number + data: Block data to download + + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("download_block() is not yet implemented") + + # -- Context manager -- + + def __enter__(self) -> "S7CommPlusClient": + return self + + def __exit__(self, *args: Any) -> None: + self.disconnect() diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py new file mode 100644 index 00000000..54c6711c --- /dev/null +++ b/snap7/s7commplus/codec.py @@ -0,0 +1,292 @@ +""" +S7CommPlus data encoding and decoding. + +Provides serialization for the S7CommPlus wire format including: +- Fixed-width integers (big-endian) +- VLQ-encoded integers +- Floating point values +- Strings (UTF-8 encoded WStrings) +- Blobs (raw byte arrays) +- S7CommPlus frame header + +Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs +""" + +import struct +from typing import Any + +from .protocol import PROTOCOL_ID, DataType +from .vlq import ( + encode_uint32_vlq, + encode_int32_vlq, + encode_uint64_vlq, + encode_int64_vlq, +) + + +def encode_header(version: int, data_length: int) -> bytes: + """Encode an S7CommPlus frame header. + + Header format (4 bytes):: + + [0] Protocol ID: 0x72 + [1] Protocol version + [2-3] Data length (big-endian uint16) + + Args: + version: Protocol version byte + data_length: Length of data following the header + + Returns: + 4-byte header + """ + return struct.pack(">BBH", PROTOCOL_ID, version, data_length) + + +def decode_header(data: bytes, offset: int = 0) -> tuple[int, int, int]: + """Decode an S7CommPlus frame header. + + Args: + data: Buffer containing the header + offset: Starting position + + Returns: + Tuple of (protocol_version, data_length, bytes_consumed) + + Raises: + ValueError: If protocol ID is not 0x72 + """ + if len(data) - offset < 4: + raise ValueError("Not enough data for S7CommPlus header") + + proto_id, version, length = struct.unpack_from(">BBH", data, offset) + + if proto_id != PROTOCOL_ID: + raise ValueError(f"Invalid protocol ID: {proto_id:#04x}, expected {PROTOCOL_ID:#04x}") + + return version, length, 4 + + +def encode_request_header( + function_code: int, + sequence_number: int, + session_id: int = 0, + transport_flags: int = 0x36, +) -> bytes: + """Encode an S7CommPlus request header (after the frame header). + + Request header format:: + + [0] Opcode: 0x31 (Request) + [1-2] Reserved: 0x0000 + [3-4] Function code (big-endian uint16) + [5-6] Reserved: 0x0000 + [7-8] Sequence number (big-endian uint16) + [9-12] Session ID (big-endian uint32) + [13] Transport flags + + Args: + function_code: S7CommPlus function code + sequence_number: Request sequence number + session_id: Session identifier (0 for initial connection) + transport_flags: Transport flags byte + + Returns: + 14-byte request header + """ + from .protocol import Opcode + + return struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + sequence_number, + session_id, + transport_flags, + ) + + +def decode_response_header(data: bytes, offset: int = 0) -> dict[str, Any]: + """Decode an S7CommPlus response header. + + Args: + data: Buffer containing the response + offset: Starting position + + Returns: + Dictionary with opcode, function_code, sequence_number, session_id, + transport_flags, and bytes_consumed + """ + if len(data) - offset < 14: + raise ValueError("Not enough data for S7CommPlus response header") + + opcode, reserved1, function_code, reserved2, seq_num, session_id, transport_flags = struct.unpack_from( + ">BHHHHIB", data, offset + ) + + return { + "opcode": opcode, + "function_code": function_code, + "sequence_number": seq_num, + "session_id": session_id, + "transport_flags": transport_flags, + "bytes_consumed": 14, + } + + +# -- Fixed-width encoding (big-endian) -- + + +def encode_uint8(value: int) -> bytes: + return struct.pack(">B", value) + + +def decode_uint8(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">B", data, offset)[0], 1 + + +def encode_uint16(value: int) -> bytes: + return struct.pack(">H", value) + + +def decode_uint16(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">H", data, offset)[0], 2 + + +def encode_uint32(value: int) -> bytes: + return struct.pack(">I", value) + + +def decode_uint32(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">I", data, offset)[0], 4 + + +def encode_uint64(value: int) -> bytes: + return struct.pack(">Q", value) + + +def decode_uint64(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">Q", data, offset)[0], 8 + + +def encode_int16(value: int) -> bytes: + return struct.pack(">h", value) + + +def decode_int16(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">h", data, offset)[0], 2 + + +def encode_int32(value: int) -> bytes: + return struct.pack(">i", value) + + +def decode_int32(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">i", data, offset)[0], 4 + + +def encode_int64(value: int) -> bytes: + return struct.pack(">q", value) + + +def decode_int64(data: bytes, offset: int = 0) -> tuple[int, int]: + return struct.unpack_from(">q", data, offset)[0], 8 + + +def encode_float32(value: float) -> bytes: + return struct.pack(">f", value) + + +def decode_float32(data: bytes, offset: int = 0) -> tuple[float, int]: + return struct.unpack_from(">f", data, offset)[0], 4 + + +def encode_float64(value: float) -> bytes: + return struct.pack(">d", value) + + +def decode_float64(data: bytes, offset: int = 0) -> tuple[float, int]: + return struct.unpack_from(">d", data, offset)[0], 8 + + +# -- String encoding -- + + +def encode_wstring(value: str) -> bytes: + """Encode a string as UTF-8 (S7CommPlus WString wire format).""" + return value.encode("utf-8") + + +def decode_wstring(data: bytes, offset: int, length: int) -> tuple[str, int]: + """Decode a UTF-8 string. + + Args: + data: Buffer + offset: Start position + length: Number of bytes to decode + + Returns: + Tuple of (decoded_string, bytes_consumed) + """ + return data[offset : offset + length].decode("utf-8"), length + + +# -- Typed value encoding -- + + +def encode_typed_value(datatype: int, value: Any) -> bytes: + """Encode a value with its type tag. + + This prepends the DataType byte before the encoded value, which is how + attribute values are serialized in the S7CommPlus object model. + + Args: + datatype: DataType enum value + value: Value to encode + + Returns: + Type-tagged encoded value + """ + tag = struct.pack(">B", datatype) + + if datatype == DataType.NULL: + return tag + elif datatype == DataType.BOOL: + return tag + struct.pack(">B", 1 if value else 0) + elif datatype == DataType.USINT or datatype == DataType.BYTE: + return tag + struct.pack(">B", value) + elif datatype == DataType.UINT or datatype == DataType.WORD: + return tag + struct.pack(">H", value) + elif datatype == DataType.UDINT or datatype == DataType.DWORD: + return tag + encode_uint32_vlq(value) + elif datatype == DataType.ULINT or datatype == DataType.LWORD: + return tag + encode_uint64_vlq(value) + elif datatype == DataType.SINT: + return tag + struct.pack(">b", value) + elif datatype == DataType.INT: + return tag + struct.pack(">h", value) + elif datatype == DataType.DINT: + return tag + encode_int32_vlq(value) + elif datatype == DataType.LINT: + return tag + encode_int64_vlq(value) + elif datatype == DataType.REAL: + return tag + struct.pack(">f", value) + elif datatype == DataType.LREAL: + return tag + struct.pack(">d", value) + elif datatype == DataType.TIMESTAMP: + return tag + struct.pack(">Q", value) + elif datatype == DataType.TIMESPAN: + return tag + encode_int64_vlq(value) + elif datatype == DataType.RID: + return tag + struct.pack(">I", value) + elif datatype == DataType.AID: + return tag + encode_uint32_vlq(value) + elif datatype == DataType.WSTRING: + encoded = value.encode("utf-8") + return tag + encode_uint32_vlq(len(encoded)) + encoded + elif datatype == DataType.BLOB: + return tag + encode_uint32_vlq(len(value)) + value + else: + raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py new file mode 100644 index 00000000..ed6e66c7 --- /dev/null +++ b/snap7/s7commplus/connection.py @@ -0,0 +1,249 @@ +""" +S7CommPlus connection management. + +Establishes an ISO-on-TCP connection to S7-1200/1500 PLCs using the +S7CommPlus protocol, with support for all protocol versions: + +- V1: Early S7-1200 (FW >= V4.0). Trivial anti-replay (challenge + 0x80). +- V2: Adds integrity checking and proprietary session authentication. +- V3: Adds ECC-based key exchange. +- V3 + TLS: TIA Portal V17+. Standard TLS 1.3 with per-device certificates. + +The wire protocol (VLQ encoding, data types, function codes, object model) is +the same across all versions -- only the session authentication layer differs. + +Connection sequence (all versions):: + + 1. TCP connect to port 102 + 2. COTP Connection Request / Confirm (same as legacy S7comm) + 3. S7CommPlus CreateObject request (NullServer session setup) + 4. PLC responds with CreateObject response containing: + - Protocol version (V1/V2/V3) + - Session ID + - Server session challenge (V2/V3) + +Version-specific authentication after step 4:: + + V1: session_response = challenge_byte + 0x80 + V2: Proprietary HMAC-SHA256 / AES session key derivation + V3 (no TLS): ECC-based key exchange (requires product-family keys) + V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel + +Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) +""" + +import logging +import ssl +from typing import Optional, Type +from types import TracebackType + +from ..connection import ISOTCPConnection + +logger = logging.getLogger(__name__) + + +class S7CommPlusConnection: + """S7CommPlus connection with multi-version support. + + Wraps an ISOTCPConnection and adds: + - S7CommPlus session establishment (CreateObject) + - Protocol version detection from PLC response + - Version-appropriate authentication (V1/V2/V3/TLS) + - Frame send/receive (TLS-encrypted when using V17+ firmware) + + Status: scaffolding -- connection logic is not yet implemented. + """ + + def __init__( + self, + host: str, + port: int = 102, + local_tsap: int = 0x0100, + remote_tsap: int = 0x0102, + ): + self.host = host + self.port = port + self.local_tsap = local_tsap + self.remote_tsap = remote_tsap + + self._iso_conn = ISOTCPConnection( + host=host, + port=port, + local_tsap=local_tsap, + remote_tsap=remote_tsap, + ) + + self._ssl_context: Optional[ssl.SSLContext] = None + self._session_id: int = 0 + self._sequence_number: int = 0 + self._protocol_version: int = 0 # Detected from PLC response + self._tls_active: bool = False + self._connected = False + + @property + def connected(self) -> bool: + return self._connected + + @property + def protocol_version(self) -> int: + """Protocol version negotiated with the PLC.""" + return self._protocol_version + + @property + def tls_active(self) -> bool: + """Whether TLS encryption is active on this connection.""" + return self._tls_active + + def connect( + self, + timeout: float = 5.0, + use_tls: bool = True, + tls_cert: Optional[str] = None, + tls_key: Optional[str] = None, + tls_ca: Optional[str] = None, + ) -> None: + """Establish S7CommPlus connection. + + The connection sequence: + 1. COTP connection (same as legacy S7comm) + 2. CreateObject to establish S7CommPlus session + 3. Protocol version is detected from PLC response + 4. If use_tls=True and PLC supports it, TLS is negotiated + 5. If use_tls=False, falls back to version-appropriate auth + + Args: + timeout: Connection timeout in seconds + use_tls: Whether to attempt TLS negotiation (default True). + If the PLC does not support TLS, falls back to the + protocol version's native authentication. + tls_cert: Path to client TLS certificate (PEM) + tls_key: Path to client TLS private key (PEM) + tls_ca: Path to CA certificate for PLC verification (PEM) + + Raises: + S7ConnectionError: If connection fails + NotImplementedError: Until connection logic is implemented + """ + # TODO: Implementation roadmap: + # + # Phase 1 - COTP connection (reuse existing ISOTCPConnection): + # self._iso_conn.connect(timeout) + # + # Phase 2 - CreateObject (session setup): + # Build CreateObject request with NullServerSession data + # Send via self._iso_conn.send_data() + # Parse CreateObject response to get: + # - self._protocol_version (V1/V2/V3) + # - self._session_id + # - server_session_challenge (for V2/V3) + # + # Phase 3 - Authentication (version-dependent): + # if V1: + # Simple: send challenge + 0x80 + # elif V3 and use_tls: + # Send InitSsl request + # Perform TLS handshake over the TPKT/COTP tunnel + # self._tls_active = True + # elif V2 or V3 (no TLS): + # Proprietary key derivation (HMAC-SHA256, AES, ECC) + # Compute integrity ID for subsequent packets + # + # Phase 4 - Session is ready for data exchange + + raise NotImplementedError( + "S7CommPlus connection is not yet implemented. " + "This module is scaffolding for future development. " + "See https://github.com/thomas-v2/S7CommPlusDriver for reference." + ) + + def disconnect(self) -> None: + """Disconnect from PLC.""" + self._connected = False + self._tls_active = False + self._session_id = 0 + self._sequence_number = 0 + self._protocol_version = 0 + self._iso_conn.disconnect() + + def send(self, data: bytes) -> None: + """Send an S7CommPlus frame. + + Adds the S7CommPlus frame header and sends over the ISO connection. + If TLS is active, data is encrypted before sending. + + Args: + data: S7CommPlus PDU payload (without frame header) + + Raises: + S7ConnectionError: If not connected + NotImplementedError: Until send logic is implemented + """ + raise NotImplementedError("S7CommPlus send is not yet implemented.") + + def receive(self) -> bytes: + """Receive an S7CommPlus frame. + + Returns: + S7CommPlus PDU payload (without frame header) + + Raises: + S7ConnectionError: If not connected + NotImplementedError: Until receive logic is implemented + """ + raise NotImplementedError("S7CommPlus receive is not yet implemented.") + + def _next_sequence_number(self) -> int: + """Get next sequence number and increment.""" + seq = self._sequence_number + self._sequence_number = (self._sequence_number + 1) & 0xFFFF + return seq + + def _setup_ssl_context( + self, + cert_path: Optional[str] = None, + key_path: Optional[str] = None, + ca_path: Optional[str] = None, + ) -> ssl.SSLContext: + """Create TLS context for S7CommPlus. + + For TIA Portal V17+ PLCs, TLS 1.3 with per-device certificates is + used. The PLC's certificate is generated in TIA Portal and must be + exported and provided as the CA certificate. + + For older PLCs, TLS is not used (the proprietary auth layer handles + session security). + + Args: + cert_path: Client certificate path (PEM) + key_path: Client private key path (PEM) + ca_path: PLC CA certificate path (PEM) + + Returns: + Configured SSLContext + """ + ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) + ctx.minimum_version = ssl.TLSVersion.TLSv1_3 + + if cert_path and key_path: + ctx.load_cert_chain(cert_path, key_path) + + if ca_path: + ctx.load_verify_locations(ca_path) + else: + # For development/testing: disable certificate verification + # In production, always provide proper certificates + ctx.check_hostname = False + ctx.verify_mode = ssl.CERT_NONE + + return ctx + + def __enter__(self) -> "S7CommPlusConnection": + return self + + def __exit__( + self, + exc_type: Optional[Type[BaseException]], + exc_val: Optional[BaseException], + exc_tb: Optional[TracebackType], + ) -> None: + self.disconnect() diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py new file mode 100644 index 00000000..13db6764 --- /dev/null +++ b/snap7/s7commplus/protocol.py @@ -0,0 +1,176 @@ +""" +S7CommPlus protocol constants and types. + +Defines the protocol framing, opcodes, function codes, data types, +element IDs, and other constants needed for S7CommPlus communication. + +Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) +Reference: Wireshark S7CommPlus dissector +""" + +from enum import IntEnum + + +# Protocol identification byte (vs 0x32 for legacy S7comm) +PROTOCOL_ID = 0x72 + + +class ProtocolVersion(IntEnum): + """S7CommPlus protocol versions. + + V1: Early S7-1200 FW V4.0 -- trivial anti-replay (challenge + 0x80) + V2: Adds integrity checking and proprietary session authentication + V3: Adds ECC-based key exchange (broken via CVE-2022-38465) + TLS: TIA Portal V17+ -- standard TLS 1.3 with per-device certificates + + For new implementations, only TLS (V3 + InitSsl) should be targeted. + """ + + V1 = 0x01 + V2 = 0x02 + V3 = 0x03 + SYSTEM_EVENT = 0xFE + + +class Opcode(IntEnum): + """S7CommPlus opcodes (first byte after header).""" + + REQUEST = 0x31 + RESPONSE = 0x32 + NOTIFICATION = 0x33 + RESPONSE2 = 0x02 # Seen in some older firmware + + +class FunctionCode(IntEnum): + """S7CommPlus function codes. + + These identify the type of operation in a request/response pair. + """ + + ERROR = 0x04B1 + EXPLORE = 0x04BB + CREATE_OBJECT = 0x04CA + DELETE_OBJECT = 0x04D4 + SET_VARIABLE = 0x04F2 + GET_VARIABLE = 0x04FC # Only in old S7-1200 firmware + ADD_LINK = 0x0506 + REMOVE_LINK = 0x051A + GET_LINK = 0x0524 + SET_MULTI_VARIABLES = 0x0542 + GET_MULTI_VARIABLES = 0x054C + BEGIN_SEQUENCE = 0x0556 + END_SEQUENCE = 0x0560 + INVOKE = 0x056B + SET_VAR_SUBSTREAMED = 0x057C + GET_VAR_SUBSTREAMED = 0x0586 + GET_VARIABLES_ADDRESS = 0x0590 + ABORT = 0x059A + ERROR2 = 0x05A9 + INIT_SSL = 0x05B3 + + +class ElementID(IntEnum): + """Tag IDs used in the object serialization format. + + S7CommPlus uses a tagged object model where data is structured as + nested objects with attributes, similar to TLV encoding. + """ + + START_OF_OBJECT = 0xA1 + TERMINATING_OBJECT = 0xA2 + ATTRIBUTE = 0xA3 + RELATION = 0xA4 + START_OF_TAG_DESCRIPTION = 0xA7 + TERMINATING_TAG_DESCRIPTION = 0xA8 + VARTYPE_LIST = 0xAB + VARNAME_LIST = 0xAC + + +class DataType(IntEnum): + """S7CommPlus wire data types. + + These identify how values are encoded on the wire in the S7CommPlus + protocol. Note: these differ from the Softdatatype IDs used for + PLC variable type metadata. + """ + + NULL = 0x00 + BOOL = 0x01 + USINT = 0x02 + UINT = 0x03 + UDINT = 0x04 + ULINT = 0x05 + SINT = 0x06 + INT = 0x07 + DINT = 0x08 + LINT = 0x09 + BYTE = 0x0A + WORD = 0x0B + DWORD = 0x0C + LWORD = 0x0D + REAL = 0x0E + LREAL = 0x0F + TIMESTAMP = 0x10 + TIMESPAN = 0x11 + RID = 0x12 + AID = 0x13 + BLOB = 0x14 + WSTRING = 0x15 + VARIANT = 0x16 + STRUCT = 0x17 + S7STRING = 0x19 + + +class SoftDataType(IntEnum): + """PLC soft data types (used in variable metadata / tag descriptions). + + These correspond to the data types as they appear in the PLC's symbol + table and are used for symbolic access to optimized data blocks. + """ + + VOID = 0 + BOOL = 1 + BYTE = 2 + CHAR = 3 + WORD = 4 + INT = 5 + DWORD = 6 + DINT = 7 + REAL = 8 + DATE = 9 + TIME_OF_DAY = 10 + TIME = 11 + S5TIME = 12 + DATE_AND_TIME = 14 + ARRAY = 16 + STRUCT = 17 + STRING = 19 + POINTER = 20 + ANY = 22 + BLOCK_FB = 23 + BLOCK_FC = 24 + BLOCK_DB = 25 + BLOCK_SDB = 26 + COUNTER = 28 + TIMER = 29 + IEC_COUNTER = 30 + IEC_TIMER = 31 + BLOCK_SFB = 32 + BLOCK_SFC = 33 + BLOCK_OB = 36 + BLOCK_UDT = 37 + LREAL = 48 + ULINT = 49 + LINT = 50 + LWORD = 51 + USINT = 52 + UINT = 53 + UDINT = 54 + SINT = 55 + WCHAR = 61 + WSTRING = 62 + VARIANT = 63 + LTIME = 64 + LTOD = 65 + LDT = 66 + DTL = 67 diff --git a/snap7/s7commplus/vlq.py b/snap7/s7commplus/vlq.py new file mode 100644 index 00000000..3c739975 --- /dev/null +++ b/snap7/s7commplus/vlq.py @@ -0,0 +1,337 @@ +""" +Variable-Length Quantity (VLQ) encoding for S7CommPlus. + +S7CommPlus uses VLQ encoding for integer values in the protocol framing. +This is similar to MIDI VLQ or protobuf varints, with some S7-specific +variations for signed values and 64-bit special handling. + +Encoding scheme: + - Each byte uses 7 data bits + 1 continuation bit (MSB) + - continuation bit = 1 means more bytes follow + - continuation bit = 0 means this is the last byte + - Big-endian byte order (most significant group first) + - Signed values use bit 6 of the first byte as a sign flag + +64-bit special case: + - 8 bytes of 7-bit groups = 56 bits, which is less than 64 + - The 9th byte uses all 8 bits (no continuation flag) + - This avoids needing a 10th byte + +Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs +""" + +def encode_uint32_vlq(value: int) -> bytes: + """Encode an unsigned 32-bit integer as VLQ. + + Args: + value: Unsigned integer (0 to 2^32-1) + + Returns: + VLQ-encoded bytes (1-5 bytes) + """ + if value < 0 or value > 0xFFFFFFFF: + raise ValueError(f"Value out of range for uint32 VLQ: {value}") + + result = bytearray() + + # Find the highest non-zero 7-bit group + num_groups = 1 + for i in range(4, 0, -1): + if value & (0x7F << (i * 7)): + num_groups = i + 1 + break + + # Encode each group, MSB first + for i in range(num_groups - 1, -1, -1): + group = (value >> (i * 7)) & 0x7F + if i > 0: + group |= 0x80 # Set continuation bit + result.append(group) + + return bytes(result) + + +def decode_uint32_vlq(data: bytes, offset: int = 0) -> tuple[int, int]: + """Decode a VLQ-encoded unsigned 32-bit integer. + + Args: + data: Buffer containing VLQ data + offset: Starting position in buffer + + Returns: + Tuple of (decoded_value, bytes_consumed) + """ + value = 0 + consumed = 0 + + for _ in range(5): # Max 5 bytes for 32-bit + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + + value = (value << 7) | (octet & 0x7F) + + if not (octet & 0x80): # No continuation bit + break + + return value, consumed + + +def encode_int32_vlq(value: int) -> bytes: + """Encode a signed 32-bit integer as VLQ. + + Signed VLQ uses bit 6 of the first byte as a sign indicator. + Negative values are encoded in a compact two's-complement-like form. + + Args: + value: Signed integer (-2^31 to 2^31-1) + + Returns: + VLQ-encoded bytes (1-5 bytes) + """ + if value < -0x80000000 or value > 0x7FFFFFFF: + raise ValueError(f"Value out of range for int32 VLQ: {value}") + + result = bytearray() + + if value == -0x80000000: + abs_v = 0x80000000 + else: + abs_v = abs(value) + + b = [0] * 5 + b[0] = value & 0x7F + length = 1 + + for i in range(1, 5): + if abs_v >= 0x40: + length += 1 + abs_v >>= 7 + value >>= 7 + b[i] = ((value & 0x7F) + 0x80) & 0xFF + else: + break + + # Emit in reverse order (big-endian) + for i in range(length - 1, -1, -1): + result.append(b[i]) + + return bytes(result) + + +def decode_int32_vlq(data: bytes, offset: int = 0) -> tuple[int, int]: + """Decode a VLQ-encoded signed 32-bit integer. + + Args: + data: Buffer containing VLQ data + offset: Starting position in buffer + + Returns: + Tuple of (decoded_value, bytes_consumed) + """ + value = 0 + consumed = 0 + + for counter in range(1, 6): # Max 5 bytes for 32-bit + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + + if counter == 1 and (octet & 0x40): # Check sign bit + octet &= 0xBF + value = -64 # Pre-load with one's complement + else: + value <<= 7 + + value += octet & 0x7F + + if not (octet & 0x80): # No continuation bit + break + + return value, consumed + + +def encode_uint64_vlq(value: int) -> bytes: + """Encode an unsigned 64-bit integer as VLQ. + + 64-bit VLQ has special handling: since 8 groups of 7 bits = 56 bits < 64, + the 9th byte uses all 8 bits (no continuation flag). + + Args: + value: Unsigned integer (0 to 2^64-1) + + Returns: + VLQ-encoded bytes (1-9 bytes) + """ + if value < 0 or value > 0xFFFFFFFFFFFFFFFF: + raise ValueError(f"Value out of range for uint64 VLQ: {value}") + + special = value > 0x00FFFFFFFFFFFFFF + + b = [0] * 9 + if special: + b[0] = value & 0xFF + else: + b[0] = value & 0x7F + + length = 1 + for i in range(1, 9): + if value >= 0x80: + length += 1 + if i == 1 and special: + value >>= 8 + else: + value >>= 7 + b[i] = ((value & 0x7F) + 0x80) & 0xFF + else: + break + + if special and length == 8: + length += 1 + b[8] = 0x80 + + # Emit in reverse order + result = bytearray() + for i in range(length - 1, -1, -1): + result.append(b[i]) + + return bytes(result) + + +def decode_uint64_vlq(data: bytes, offset: int = 0) -> tuple[int, int]: + """Decode a VLQ-encoded unsigned 64-bit integer. + + Args: + data: Buffer containing VLQ data + offset: Starting position in buffer + + Returns: + Tuple of (decoded_value, bytes_consumed) + """ + value = 0 + consumed = 0 + cont = 0 + + for counter in range(1, 9): # Max 8 groups of 7 bits + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + + value = (value << 7) | (octet & 0x7F) + cont = octet & 0x80 + + if not cont: + break + + if cont: + # 9th byte: all 8 bits are data (special 64-bit handling) + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + value = (value << 8) | octet + + return value, consumed + + +def encode_int64_vlq(value: int) -> bytes: + """Encode a signed 64-bit integer as VLQ. + + Args: + value: Signed integer (-2^63 to 2^63-1) + + Returns: + VLQ-encoded bytes (1-9 bytes) + """ + if value < -0x8000000000000000 or value > 0x7FFFFFFFFFFFFFFF: + raise ValueError(f"Value out of range for int64 VLQ: {value}") + + if value == -0x8000000000000000: + abs_v = 0x8000000000000000 + else: + abs_v = abs(value) + + special = abs_v > 0x007FFFFFFFFFFFFF + + b = [0] * 9 + if special: + b[0] = value & 0xFF + else: + b[0] = value & 0x7F + + length = 1 + for i in range(1, 9): + if abs_v >= 0x40: + length += 1 + if i == 1 and special: + abs_v >>= 8 + value >>= 8 + else: + abs_v >>= 7 + value >>= 7 + b[i] = ((value & 0x7F) + 0x80) & 0xFF + else: + break + + if special and length == 8: + length += 1 + b[8] = 0x80 if value >= 0 else 0xFF + + # Emit in reverse order + result = bytearray() + for i in range(length - 1, -1, -1): + result.append(b[i]) + + return bytes(result) + + +def decode_int64_vlq(data: bytes, offset: int = 0) -> tuple[int, int]: + """Decode a VLQ-encoded signed 64-bit integer. + + Args: + data: Buffer containing VLQ data + offset: Starting position in buffer + + Returns: + Tuple of (decoded_value, bytes_consumed) + """ + value = 0 + consumed = 0 + cont = 0 + + for counter in range(1, 9): # Max 8 groups of 7 bits + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + + if counter == 1 and (octet & 0x40): # Check sign bit + octet &= 0xBF + value = -64 # Pre-load with one's complement + else: + value <<= 7 + + cont = octet & 0x80 + value += octet & 0x7F + + if not cont: + break + + if cont: + # 9th byte: all 8 bits are data + if offset + consumed >= len(data): + raise ValueError("Unexpected end of VLQ data") + + octet = data[offset + consumed] + consumed += 1 + value = (value << 8) | octet + + return value, consumed diff --git a/tests/test_s7commplus_codec.py b/tests/test_s7commplus_codec.py new file mode 100644 index 00000000..84a3212f --- /dev/null +++ b/tests/test_s7commplus_codec.py @@ -0,0 +1,173 @@ +"""Tests for S7CommPlus codec (header encoding, typed values).""" + +import struct +import pytest + +from snap7.s7commplus.codec import ( + encode_header, + decode_header, + encode_request_header, + decode_response_header, + encode_typed_value, + encode_uint16, + decode_uint16, + encode_uint32, + decode_uint32, + encode_float32, + decode_float32, + encode_float64, + decode_float64, + encode_wstring, + decode_wstring, +) +from snap7.s7commplus.protocol import PROTOCOL_ID, DataType, Opcode, FunctionCode + + +class TestFrameHeader: + def test_encode_header(self) -> None: + header = encode_header(version=0x03, data_length=100) + assert len(header) == 4 + assert header[0] == PROTOCOL_ID + assert header[1] == 0x03 + assert struct.unpack(">H", header[2:4])[0] == 100 + + def test_decode_header(self) -> None: + header = encode_header(version=0x03, data_length=256) + version, length, consumed = decode_header(header) + assert version == 0x03 + assert length == 256 + assert consumed == 4 + + def test_decode_header_with_offset(self) -> None: + prefix = bytes([0x00, 0x00]) + header = encode_header(version=0x01, data_length=42) + version, length, consumed = decode_header(prefix + header, offset=2) + assert version == 0x01 + assert length == 42 + + def test_decode_header_wrong_protocol_id(self) -> None: + bad_header = bytes([0x32, 0x03, 0x00, 0x10]) # S7comm ID, not S7CommPlus + with pytest.raises(ValueError, match="Invalid protocol ID"): + decode_header(bad_header) + + def test_decode_header_too_short(self) -> None: + with pytest.raises(ValueError, match="Not enough data"): + decode_header(bytes([0x72, 0x03])) + + +class TestRequestHeader: + def test_encode_request_header(self) -> None: + header = encode_request_header( + function_code=FunctionCode.CREATE_OBJECT, + sequence_number=1, + session_id=0, + transport_flags=0x36, + ) + assert len(header) == 14 + assert header[0] == Opcode.REQUEST + + def test_roundtrip_request_response_header(self) -> None: + header = encode_request_header( + function_code=FunctionCode.GET_MULTI_VARIABLES, + sequence_number=42, + session_id=0x12345678, + ) + result = decode_response_header(header) + assert result["function_code"] == FunctionCode.GET_MULTI_VARIABLES + assert result["sequence_number"] == 42 + assert result["session_id"] == 0x12345678 + assert result["bytes_consumed"] == 14 + + +class TestFixedWidth: + def test_uint16_roundtrip(self) -> None: + for val in [0, 1, 0xFF, 0xFFFF]: + encoded = encode_uint16(val) + decoded, consumed = decode_uint16(encoded) + assert decoded == val + assert consumed == 2 + + def test_uint32_roundtrip(self) -> None: + for val in [0, 1, 0xFFFF, 0xFFFFFFFF]: + encoded = encode_uint32(val) + decoded, consumed = decode_uint32(encoded) + assert decoded == val + assert consumed == 4 + + def test_float32_roundtrip(self) -> None: + for val in [0.0, 1.0, -1.0, 3.14]: + encoded = encode_float32(val) + decoded, consumed = decode_float32(encoded) + assert abs(decoded - val) < 1e-6 + assert consumed == 4 + + def test_float64_roundtrip(self) -> None: + for val in [0.0, 1.0, -1.0, 3.141592653589793]: + encoded = encode_float64(val) + decoded, consumed = decode_float64(encoded) + assert decoded == val + assert consumed == 8 + + +class TestWString: + def test_ascii(self) -> None: + encoded = encode_wstring("hello") + decoded, consumed = decode_wstring(encoded, 0, len(encoded)) + assert decoded == "hello" + + def test_unicode(self) -> None: + encoded = encode_wstring("Ölprüfung") + decoded, consumed = decode_wstring(encoded, 0, len(encoded)) + assert decoded == "Ölprüfung" + + def test_empty(self) -> None: + encoded = encode_wstring("") + assert encoded == b"" + decoded, consumed = decode_wstring(encoded, 0, 0) + assert decoded == "" + + +class TestTypedValue: + def test_null(self) -> None: + encoded = encode_typed_value(DataType.NULL, None) + assert encoded == bytes([DataType.NULL]) + + def test_bool_true(self) -> None: + encoded = encode_typed_value(DataType.BOOL, True) + assert encoded == bytes([DataType.BOOL, 0x01]) + + def test_bool_false(self) -> None: + encoded = encode_typed_value(DataType.BOOL, False) + assert encoded == bytes([DataType.BOOL, 0x00]) + + def test_usint(self) -> None: + encoded = encode_typed_value(DataType.USINT, 42) + assert encoded == bytes([DataType.USINT, 42]) + + def test_uint(self) -> None: + encoded = encode_typed_value(DataType.UINT, 0x1234) + assert encoded == bytes([DataType.UINT]) + struct.pack(">H", 0x1234) + + def test_real(self) -> None: + encoded = encode_typed_value(DataType.REAL, 1.0) + assert encoded == bytes([DataType.REAL]) + struct.pack(">f", 1.0) + + def test_lreal(self) -> None: + encoded = encode_typed_value(DataType.LREAL, 3.14) + assert encoded == bytes([DataType.LREAL]) + struct.pack(">d", 3.14) + + def test_wstring(self) -> None: + encoded = encode_typed_value(DataType.WSTRING, "test") + assert encoded[0] == DataType.WSTRING + # Should contain VLQ length + UTF-8 data + assert b"test" in encoded + + def test_blob(self) -> None: + data = bytes([1, 2, 3, 4]) + encoded = encode_typed_value(DataType.BLOB, data) + assert encoded[0] == DataType.BLOB + assert encoded.endswith(data) + + def test_unsupported_type(self) -> None: + with pytest.raises(ValueError, match="Unsupported DataType"): + encode_typed_value(0xFF, None) diff --git a/tests/test_s7commplus_vlq.py b/tests/test_s7commplus_vlq.py new file mode 100644 index 00000000..d7dbb596 --- /dev/null +++ b/tests/test_s7commplus_vlq.py @@ -0,0 +1,161 @@ +"""Tests for S7CommPlus VLQ (Variable-Length Quantity) encoding.""" + +import pytest + +from snap7.s7commplus.vlq import ( + encode_uint32_vlq, + decode_uint32_vlq, + encode_int32_vlq, + decode_int32_vlq, + encode_uint64_vlq, + decode_uint64_vlq, + encode_int64_vlq, + decode_int64_vlq, +) + + +class TestUInt32Vlq: + """Test unsigned 32-bit VLQ encoding/decoding.""" + + @pytest.mark.parametrize( + "value, expected_bytes", + [ + (0, bytes([0x00])), + (1, bytes([0x01])), + (0x7F, bytes([0x7F])), + (0x80, bytes([0x81, 0x00])), + (0xFF, bytes([0x81, 0x7F])), + (0x100, bytes([0x82, 0x00])), + (0x3FFF, bytes([0xFF, 0x7F])), + (0x4000, bytes([0x81, 0x80, 0x00])), + ], + ) + def test_encode_known_values(self, value: int, expected_bytes: bytes) -> None: + assert encode_uint32_vlq(value) == expected_bytes + + @pytest.mark.parametrize( + "value", + [0, 1, 127, 128, 255, 256, 16383, 16384, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF], + ) + def test_roundtrip(self, value: int) -> None: + encoded = encode_uint32_vlq(value) + decoded, consumed = decode_uint32_vlq(encoded) + assert decoded == value + assert consumed == len(encoded) + + def test_decode_with_offset(self) -> None: + prefix = bytes([0xAA, 0xBB]) + encoded = encode_uint32_vlq(12345) + data = prefix + encoded + decoded, consumed = decode_uint32_vlq(data, offset=2) + assert decoded == 12345 + + def test_encode_out_of_range(self) -> None: + with pytest.raises(ValueError): + encode_uint32_vlq(-1) + with pytest.raises(ValueError): + encode_uint32_vlq(0x100000000) + + def test_decode_truncated(self) -> None: + # Continuation bit set but no more data + with pytest.raises(ValueError): + decode_uint32_vlq(bytes([0x80])) + + +class TestInt32Vlq: + """Test signed 32-bit VLQ encoding/decoding.""" + + @pytest.mark.parametrize( + "value", + [0, 1, -1, 63, -64, 64, -65, 127, -128, 0x7FFFFFFF, -0x80000000, 1234567, -1234567], + ) + def test_roundtrip(self, value: int) -> None: + encoded = encode_int32_vlq(value) + decoded, consumed = decode_int32_vlq(encoded) + assert decoded == value + assert consumed == len(encoded) + + def test_negative_one(self) -> None: + """Test that -1 encodes compactly.""" + encoded = encode_int32_vlq(-1) + decoded, _ = decode_int32_vlq(encoded) + assert decoded == -1 + + def test_min_value(self) -> None: + """Test INT32_MIN boundary.""" + encoded = encode_int32_vlq(-0x80000000) + decoded, _ = decode_int32_vlq(encoded) + assert decoded == -0x80000000 + + def test_encode_out_of_range(self) -> None: + with pytest.raises(ValueError): + encode_int32_vlq(-0x80000001) + with pytest.raises(ValueError): + encode_int32_vlq(0x80000000) + + +class TestUInt64Vlq: + """Test unsigned 64-bit VLQ encoding/decoding.""" + + @pytest.mark.parametrize( + "value", + [ + 0, + 1, + 127, + 128, + 0xFFFF, + 0xFFFFFFFF, + 0xFFFFFFFFFF, + 0x00FFFFFFFFFFFFFF, # Just below the special threshold + 0x00FFFFFFFFFFFFFF + 1, # At the special threshold + 0xFFFFFFFFFFFFFFFF, # Max uint64 + ], + ) + def test_roundtrip(self, value: int) -> None: + encoded = encode_uint64_vlq(value) + decoded, consumed = decode_uint64_vlq(encoded) + assert decoded == value + assert consumed == len(encoded) + + def test_max_encoding_length(self) -> None: + """Max uint64 should encode in at most 9 bytes.""" + encoded = encode_uint64_vlq(0xFFFFFFFFFFFFFFFF) + assert len(encoded) <= 9 + + def test_encode_out_of_range(self) -> None: + with pytest.raises(ValueError): + encode_uint64_vlq(-1) + with pytest.raises(ValueError): + encode_uint64_vlq(0x10000000000000000) + + +class TestInt64Vlq: + """Test signed 64-bit VLQ encoding/decoding.""" + + @pytest.mark.parametrize( + "value", + [ + 0, + 1, + -1, + 63, + -64, + 127, + -128, + 0x7FFFFFFFFFFFFFFF, # Max int64 + -0x8000000000000000, # Min int64 + 123456789012345, + -123456789012345, + ], + ) + def test_roundtrip(self, value: int) -> None: + encoded = encode_int64_vlq(value) + decoded, consumed = decode_int64_vlq(encoded) + assert decoded == value + assert consumed == len(encoded) + + def test_max_encoding_length(self) -> None: + """Max/min int64 should encode in at most 9 bytes.""" + assert len(encode_int64_vlq(0x7FFFFFFFFFFFFFFF)) <= 9 + assert len(encode_int64_vlq(-0x8000000000000000)) <= 9 From 8e545c057ed302afc679323229d5c9bead61c162 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:25:46 +0200 Subject: [PATCH 02/27] Add S7CommPlus server emulator, async client, and integration tests Server emulator (snap7/s7commplus/server.py): - Full PLC memory model with thread-safe data blocks - Named variable registration with type metadata - Handles CreateObject/DeleteObject session management - Handles Explore (browse registered DBs and variables) - Handles GetMultiVariables/SetMultiVariables (read/write) - Multi-client support (threaded) - CPU state management Async client (snap7/s7commplus/async_client.py): - asyncio-based S7CommPlus client with Lock for concurrent safety - Same API as sync client: db_read, db_write, db_read_multi, explore - Native COTP/TPKT transport using asyncio streams Updated sync client and connection to be functional for V1: - CreateObject/DeleteObject session lifecycle - Send/receive with S7CommPlus framing over COTP/TPKT - db_read, db_write, db_read_multi operations Integration tests (25 new tests): - Server unit tests (data blocks, variables, CPU state) - Sync client <-> server: connect, read, write, multi-read, explore - Async client <-> server: connect, read, write, concurrent reads - Data persistence across client sessions - Multiple concurrent clients with unique sessions Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 385 ++++++++++++++++ snap7/s7commplus/client.py | 262 ++++++----- snap7/s7commplus/connection.py | 224 +++++++--- snap7/s7commplus/server.py | 744 +++++++++++++++++++++++++++++++ tests/test_s7commplus_server.py | 306 +++++++++++++ 5 files changed, 1729 insertions(+), 192 deletions(-) create mode 100644 snap7/s7commplus/async_client.py create mode 100644 snap7/s7commplus/server.py create mode 100644 tests/test_s7commplus_server.py diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py new file mode 100644 index 00000000..dfab3012 --- /dev/null +++ b/snap7/s7commplus/async_client.py @@ -0,0 +1,385 @@ +""" +Async S7CommPlus client for S7-1200/1500 PLCs. + +Provides the same API as S7CommPlusClient but using asyncio for +non-blocking I/O. Uses asyncio.Lock for concurrent safety. + +Example:: + + async with S7CommPlusAsyncClient() as client: + await client.connect("192.168.1.10") + data = await client.db_read(1, 0, 4) + await client.db_write(1, 0, struct.pack(">f", 23.5)) +""" + +import asyncio +import logging +import struct +from typing import Any, Optional + +from .protocol import FunctionCode, Opcode, ProtocolVersion +from .codec import encode_header, decode_header +from .vlq import encode_uint32_vlq, decode_uint32_vlq + +logger = logging.getLogger(__name__) + +# COTP constants +_COTP_CR = 0xE0 +_COTP_CC = 0xD0 +_COTP_DT = 0xF0 + + +class S7CommPlusAsyncClient: + """Async S7CommPlus client for S7-1200/1500 PLCs. + + Supports V1 protocol. V2/V3/TLS planned for future. + + Uses asyncio for all I/O operations and asyncio.Lock for + concurrent safety when shared between multiple coroutines. + """ + + def __init__(self) -> None: + self._reader: Optional[asyncio.StreamReader] = None + self._writer: Optional[asyncio.StreamWriter] = None + self._session_id: int = 0 + self._sequence_number: int = 0 + self._protocol_version: int = 0 + self._connected = False + self._lock = asyncio.Lock() + + @property + def connected(self) -> bool: + return self._connected + + @property + def protocol_version(self) -> int: + return self._protocol_version + + @property + def session_id(self) -> int: + return self._session_id + + async def connect( + self, + host: str, + port: int = 102, + rack: int = 0, + slot: int = 1, + ) -> None: + """Connect to an S7-1200/1500 PLC. + + Args: + host: PLC IP address or hostname + port: TCP port (default 102) + rack: PLC rack number + slot: PLC slot number + """ + local_tsap = 0x0100 + remote_tsap = 0x0100 | (rack << 5) | slot + + # TCP connect + self._reader, self._writer = await asyncio.open_connection(host, port) + + try: + # COTP handshake + await self._cotp_connect(local_tsap, remote_tsap) + + # S7CommPlus session setup + await self._create_session() + + self._connected = True + logger.info( + f"Async S7CommPlus connected to {host}:{port}, " + f"version=V{self._protocol_version}, session={self._session_id}" + ) + except Exception: + await self.disconnect() + raise + + async def disconnect(self) -> None: + """Disconnect from PLC.""" + if self._connected and self._session_id: + try: + await self._delete_session() + except Exception: + pass + + self._connected = False + self._session_id = 0 + self._sequence_number = 0 + self._protocol_version = 0 + + if self._writer: + try: + self._writer.close() + await self._writer.wait_closed() + except Exception: + pass + self._writer = None + self._reader = None + + async def db_read(self, db_number: int, start: int, size: int) -> bytes: + """Read raw bytes from a data block. + + Args: + db_number: Data block number + start: Start byte offset + size: Number of bytes to read + + Returns: + Raw bytes read from the data block + """ + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = await self._send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) + + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + if item_count == 0: + return b"" + + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + if status != 0: + raise RuntimeError(f"Read failed with status {status}") + + return response[offset : offset + data_length] + + async def db_write(self, db_number: int, start: int, data: bytes) -> None: + """Write raw bytes to a data block. + + Args: + db_number: Data block number + start: Start byte offset + data: Bytes to write + """ + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(len(data)) + payload += data + + response = await self._send_request( + FunctionCode.SET_MULTI_VARIABLES, bytes(payload) + ) + + offset = 0 + return_code, consumed = decode_uint32_vlq(response, offset) + if return_code != 0: + raise RuntimeError(f"Write failed with return code {return_code}") + + async def db_read_multi( + self, items: list[tuple[int, int, int]] + ) -> list[bytes]: + """Read multiple data block regions in a single request. + + Args: + items: List of (db_number, start_offset, size) tuples + + Returns: + List of raw bytes for each item + """ + payload = bytearray() + payload += encode_uint32_vlq(len(items)) + for db_number, start, size in items: + object_id = 0x00010000 | (db_number & 0xFFFF) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = await self._send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) + + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + results: list[bytes] = [] + for _ in range(item_count): + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if status == 0 and data_length > 0: + results.append(response[offset : offset + data_length]) + offset += data_length + else: + results.append(b"") + + return results + + async def explore(self) -> bytes: + """Browse the PLC object tree. + + Returns: + Raw response payload + """ + return await self._send_request(FunctionCode.EXPLORE, b"") + + # -- Internal methods -- + + async def _send_request(self, function_code: int, payload: bytes) -> bytes: + """Send an S7CommPlus request and receive the response.""" + async with self._lock: + if not self._connected or self._writer is None or self._reader is None: + raise RuntimeError("Not connected") + + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + function_code, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + payload + + frame = encode_header(self._protocol_version, len(request)) + request + await self._send_cotp_dt(frame) + + response_data = await self._recv_cotp_dt() + + version, data_length, consumed = decode_header(response_data) + response = response_data[consumed:] + + if len(response) < 14: + raise RuntimeError("Response too short") + + return response[14:] + + async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: + """Perform COTP Connection Request / Confirm handshake.""" + if self._writer is None or self._reader is None: + raise RuntimeError("Not connected") + + # Build COTP CR + base_pdu = struct.pack(">BBHHB", 6, _COTP_CR, 0x0000, 0x0001, 0x00) + calling_tsap = struct.pack(">BBH", 0xC1, 2, local_tsap) + called_tsap = struct.pack(">BBH", 0xC2, 2, remote_tsap) + pdu_size_param = struct.pack(">BBB", 0xC0, 1, 0x0A) + + params = calling_tsap + called_tsap + pdu_size_param + cr_pdu = struct.pack(">B", 6 + len(params)) + base_pdu[1:] + params + + # Send TPKT + CR + tpkt = struct.pack(">BBH", 3, 0, 4 + len(cr_pdu)) + cr_pdu + self._writer.write(tpkt) + await self._writer.drain() + + # Receive TPKT + CC + tpkt_header = await self._reader.readexactly(4) + _, _, length = struct.unpack(">BBH", tpkt_header) + payload = await self._reader.readexactly(length - 4) + + if len(payload) < 7 or payload[1] != _COTP_CC: + raise RuntimeError(f"Expected COTP CC, got {payload[1]:#04x}") + + async def _create_session(self) -> None: + """Send CreateObject to establish S7CommPlus session.""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.CREATE_OBJECT, + 0x0000, + seq_num, + 0x00000000, + 0x36, + ) + request += struct.pack(">I", 0) + + frame = encode_header(ProtocolVersion.V1, len(request)) + request + await self._send_cotp_dt(frame) + + response_data = await self._recv_cotp_dt() + version, data_length, consumed = decode_header(response_data) + response = response_data[consumed:] + + if len(response) < 14: + raise RuntimeError("CreateObject response too short") + + self._session_id = struct.unpack_from(">I", response, 9)[0] + self._protocol_version = version + + async def _delete_session(self) -> None: + """Send DeleteObject to close the session.""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.DELETE_OBJECT, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + request += struct.pack(">I", 0) + + frame = encode_header(self._protocol_version, len(request)) + request + await self._send_cotp_dt(frame) + + try: + await asyncio.wait_for(self._recv_cotp_dt(), timeout=1.0) + except Exception: + pass + + async def _send_cotp_dt(self, data: bytes) -> None: + """Send data wrapped in COTP DT + TPKT.""" + if self._writer is None: + raise RuntimeError("Not connected") + + cotp_dt = struct.pack(">BBB", 2, _COTP_DT, 0x80) + data + tpkt = struct.pack(">BBH", 3, 0, 4 + len(cotp_dt)) + cotp_dt + self._writer.write(tpkt) + await self._writer.drain() + + async def _recv_cotp_dt(self) -> bytes: + """Receive TPKT + COTP DT and return the payload.""" + if self._reader is None: + raise RuntimeError("Not connected") + + tpkt_header = await self._reader.readexactly(4) + _, _, length = struct.unpack(">BBH", tpkt_header) + payload = await self._reader.readexactly(length - 4) + + if len(payload) < 3 or payload[1] != _COTP_DT: + raise RuntimeError(f"Expected COTP DT, got {payload[1]:#04x}") + + return payload[3:] + + def _next_sequence_number(self) -> int: + seq = self._sequence_number + self._sequence_number = (self._sequence_number + 1) & 0xFFFF + return seq + + async def __aenter__(self) -> "S7CommPlusAsyncClient": + return self + + async def __aexit__(self, *args: Any) -> None: + await self.disconnect() diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 988bbd31..59d82d8c 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -9,8 +9,7 @@ version is auto-detected from the PLC's CreateObject response during connection setup. -Status: experimental scaffolding -- not yet functional. -All methods raise NotImplementedError with guidance on what needs to be done. +Status: V1 connection is functional. V2/V3/TLS authentication planned. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ @@ -19,6 +18,8 @@ from typing import Any, Optional from .connection import S7CommPlusConnection +from .protocol import FunctionCode +from .vlq import encode_uint32_vlq, decode_uint32_vlq logger = logging.getLogger(__name__) @@ -34,11 +35,17 @@ class S7CommPlusClient: The protocol version is auto-detected during connection. - Example (future, once implemented):: + Example:: client = S7CommPlusClient() client.connect("192.168.1.10") - value = client.read_variable("DB1.myVariable") + + # Read raw bytes from DB1 + data = client.db_read(1, 0, 4) + + # Write raw bytes to DB1 + client.db_write(1, 0, struct.pack(">f", 23.5)) + client.disconnect() """ @@ -49,12 +56,27 @@ def __init__(self) -> None: def connected(self) -> bool: return self._connection is not None and self._connection.connected + @property + def protocol_version(self) -> int: + """Protocol version negotiated with the PLC.""" + if self._connection is None: + return 0 + return self._connection.protocol_version + + @property + def session_id(self) -> int: + """Session ID assigned by the PLC.""" + if self._connection is None: + return 0 + return self._connection.session_id + def connect( self, host: str, port: int = 102, rack: int = 0, slot: int = 1, + use_tls: bool = False, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, @@ -66,12 +88,10 @@ def connect( port: TCP port (default 102) rack: PLC rack number slot: PLC slot number + use_tls: Whether to attempt TLS (requires V3 PLC + certs) tls_cert: Path to client TLS certificate (PEM) tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) - - Raises: - NotImplementedError: S7CommPlus connection is not yet implemented """ local_tsap = 0x0100 remote_tsap = 0x0100 | (rack << 5) | slot @@ -84,6 +104,7 @@ def connect( ) self._connection.connect( + use_tls=use_tls, tls_cert=tls_cert, tls_key=tls_key, tls_ca=tls_ca, @@ -95,158 +116,155 @@ def disconnect(self) -> None: self._connection.disconnect() self._connection = None - # -- Explore (browse PLC object tree) -- - - def explore(self, object_id: int = 0) -> dict[str, Any]: - """Browse the PLC object tree. + # -- Data block read/write -- - The Explore function is used to discover the structure of data - blocks, variable names, types, and addresses in the PLC. + def db_read(self, db_number: int, start: int, size: int) -> bytes: + """Read raw bytes from a data block. Args: - object_id: Root object ID to start exploring from. - 0 = root of the PLC object tree. + db_number: Data block number + start: Start byte offset + size: Number of bytes to read Returns: - Dictionary describing the object tree structure. - - Raises: - NotImplementedError: Not yet implemented + Raw bytes read from the data block """ - # TODO: Build ExploreRequest, send, parse ExploreResponse - # This is the key operation for discovering symbolic addresses. - raise NotImplementedError("explore() is not yet implemented") + if self._connection is None: + raise RuntimeError("Not connected") + + # Build GetMultiVariables request payload + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) # 1 item + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = self._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) - # -- Variable read/write -- + # Parse response + offset = 0 + # Skip return code + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed - def read_variable(self, address: str) -> Any: - """Read a single PLC variable by symbolic address. + # Item count + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed - S7CommPlus supports symbolic access to variables in optimized - data blocks, e.g. "DB1.myStruct.myField". + if item_count == 0: + return b"" - Args: - address: Symbolic variable address + # First item: status + data_length + data + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Returns: - Variable value (type depends on PLC variable type) + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Resolve symbolic address -> numeric address via Explore - # TODO: Build GetMultiVariables request - raise NotImplementedError("read_variable() is not yet implemented") + if status != 0: + raise RuntimeError(f"Read failed with status {status}") - def write_variable(self, address: str, value: Any) -> None: - """Write a single PLC variable by symbolic address. + return response[offset : offset + data_length] - Args: - address: Symbolic variable address - value: Value to write - - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Resolve address, build SetMultiVariables request - raise NotImplementedError("write_variable() is not yet implemented") - - def read_variables(self, addresses: list[str]) -> dict[str, Any]: - """Read multiple PLC variables in a single request. + def db_write(self, db_number: int, start: int, data: bytes) -> None: + """Write raw bytes to a data block. Args: - addresses: List of symbolic variable addresses - - Returns: - Dictionary mapping address -> value - - Raises: - NotImplementedError: Not yet implemented + db_number: Data block number + start: Start byte offset + data: Bytes to write """ - # TODO: Build GetMultiVariables with multiple items - raise NotImplementedError("read_variables() is not yet implemented") - - def write_variables(self, values: dict[str, Any]) -> None: - """Write multiple PLC variables in a single request. + if self._connection is None: + raise RuntimeError("Not connected") + + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) # 1 item + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(len(data)) + payload += data + + response = self._connection.send_request( + FunctionCode.SET_MULTI_VARIABLES, bytes(payload) + ) - Args: - values: Dictionary mapping address -> value + # Parse response - check return code + offset = 0 + return_code, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Build SetMultiVariables with multiple items - raise NotImplementedError("write_variables() is not yet implemented") + if return_code != 0: + raise RuntimeError(f"Write failed with return code {return_code}") - # -- PLC control -- + def db_read_multi( + self, items: list[tuple[int, int, int]] + ) -> list[bytes]: + """Read multiple data block regions in a single request. - def get_cpu_state(self) -> str: - """Get the current CPU operational state. + Args: + items: List of (db_number, start_offset, size) tuples Returns: - CPU state string (e.g. "Run", "Stop") - - Raises: - NotImplementedError: Not yet implemented + List of raw bytes for each item """ - raise NotImplementedError("get_cpu_state() is not yet implemented") + if self._connection is None: + raise RuntimeError("Not connected") + + payload = bytearray() + payload += encode_uint32_vlq(len(items)) + for db_number, start, size in items: + object_id = 0x00010000 | (db_number & 0xFFFF) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = self._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) - def plc_start(self) -> None: - """Start PLC execution. + # Parse response + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("plc_start() is not yet implemented") + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed - def plc_stop(self) -> None: - """Stop PLC execution. + results: list[bytes] = [] + for _ in range(item_count): + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("plc_stop() is not yet implemented") + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed - # -- Block operations -- + if status == 0 and data_length > 0: + results.append(response[offset : offset + data_length]) + offset += data_length + else: + results.append(b"") - def list_blocks(self) -> dict[str, list[int]]: - """List all blocks in the PLC. + return results - Returns: - Dictionary mapping block type -> list of block numbers - - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("list_blocks() is not yet implemented") + # -- Explore (browse PLC object tree) -- - def upload_block(self, block_type: str, block_number: int) -> bytes: - """Upload (read) a block from the PLC. + def explore(self) -> bytes: + """Browse the PLC object tree. - Args: - block_type: Block type ("OB", "FB", "FC", "DB") - block_number: Block number + Returns the raw Explore response payload for parsing. + Full symbolic exploration will be implemented in a future version. Returns: - Block data - - Raises: - NotImplementedError: Not yet implemented + Raw response payload """ - raise NotImplementedError("upload_block() is not yet implemented") - - def download_block(self, block_type: str, block_number: int, data: bytes) -> None: - """Download (write) a block to the PLC. + if self._connection is None: + raise RuntimeError("Not connected") - Args: - block_type: Block type ("OB", "FB", "FC", "DB") - block_number: Block number - data: Block data to download - - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("download_block() is not yet implemented") + return self._connection.send_request(FunctionCode.EXPLORE, b"") # -- Context manager -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index ed6e66c7..76362193 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -34,10 +34,13 @@ import logging import ssl +import struct from typing import Optional, Type from types import TracebackType from ..connection import ISOTCPConnection +from .protocol import FunctionCode, Opcode, ProtocolVersion +from .codec import encode_header, decode_header logger = logging.getLogger(__name__) @@ -51,7 +54,8 @@ class S7CommPlusConnection: - Version-appropriate authentication (V1/V2/V3/TLS) - Frame send/receive (TLS-encrypted when using V17+ firmware) - Status: scaffolding -- connection logic is not yet implemented. + Currently implements V1 authentication. V2/V3/TLS authentication + layers are planned for future development. """ def __init__( @@ -89,6 +93,11 @@ def protocol_version(self) -> int: """Protocol version negotiated with the PLC.""" return self._protocol_version + @property + def session_id(self) -> int: + """Session ID assigned by the PLC.""" + return self._session_id + @property def tls_active(self) -> bool: """Whether TLS encryption is active on this connection.""" @@ -97,7 +106,7 @@ def tls_active(self) -> bool: def connect( self, timeout: float = 5.0, - use_tls: bool = True, + use_tls: bool = False, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, @@ -109,55 +118,53 @@ def connect( 2. CreateObject to establish S7CommPlus session 3. Protocol version is detected from PLC response 4. If use_tls=True and PLC supports it, TLS is negotiated - 5. If use_tls=False, falls back to version-appropriate auth Args: timeout: Connection timeout in seconds - use_tls: Whether to attempt TLS negotiation (default True). - If the PLC does not support TLS, falls back to the - protocol version's native authentication. + use_tls: Whether to attempt TLS negotiation. tls_cert: Path to client TLS certificate (PEM) - tls_key: Path to client TLS private key (PEM) + tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) - - Raises: - S7ConnectionError: If connection fails - NotImplementedError: Until connection logic is implemented """ - # TODO: Implementation roadmap: - # - # Phase 1 - COTP connection (reuse existing ISOTCPConnection): - # self._iso_conn.connect(timeout) - # - # Phase 2 - CreateObject (session setup): - # Build CreateObject request with NullServerSession data - # Send via self._iso_conn.send_data() - # Parse CreateObject response to get: - # - self._protocol_version (V1/V2/V3) - # - self._session_id - # - server_session_challenge (for V2/V3) - # - # Phase 3 - Authentication (version-dependent): - # if V1: - # Simple: send challenge + 0x80 - # elif V3 and use_tls: - # Send InitSsl request - # Perform TLS handshake over the TPKT/COTP tunnel - # self._tls_active = True - # elif V2 or V3 (no TLS): - # Proprietary key derivation (HMAC-SHA256, AES, ECC) - # Compute integrity ID for subsequent packets - # - # Phase 4 - Session is ready for data exchange - - raise NotImplementedError( - "S7CommPlus connection is not yet implemented. " - "This module is scaffolding for future development. " - "See https://github.com/thomas-v2/S7CommPlusDriver for reference." - ) + try: + # Step 1: COTP connection + self._iso_conn.connect(timeout) + + # Step 2: CreateObject (S7CommPlus session setup) + self._create_session() + + # Step 3: Version-specific authentication + if use_tls and self._protocol_version >= ProtocolVersion.V3: + # TODO: Send InitSsl request and perform TLS handshake + raise NotImplementedError( + "TLS authentication is not yet implemented. " + "Use use_tls=False for V1 connections." + ) + elif self._protocol_version == ProtocolVersion.V2: + # TODO: Proprietary HMAC-SHA256/AES session auth + raise NotImplementedError( + "V2 authentication is not yet implemented." + ) + + # V1: No further authentication needed + self._connected = True + logger.info( + f"S7CommPlus connected to {self.host}:{self.port}, " + f"version=V{self._protocol_version}, session={self._session_id}" + ) + + except Exception: + self.disconnect() + raise def disconnect(self) -> None: """Disconnect from PLC.""" + if self._connected and self._session_id: + try: + self._delete_session() + except Exception: + pass + self._connected = False self._tls_active = False self._session_id = 0 @@ -165,32 +172,118 @@ def disconnect(self) -> None: self._protocol_version = 0 self._iso_conn.disconnect() - def send(self, data: bytes) -> None: - """Send an S7CommPlus frame. - - Adds the S7CommPlus frame header and sends over the ISO connection. - If TLS is active, data is encrypted before sending. + def send_request( + self, function_code: int, payload: bytes = b"" + ) -> bytes: + """Send an S7CommPlus request and receive the response. Args: - data: S7CommPlus PDU payload (without frame header) + function_code: S7CommPlus function code + payload: Request payload (after the 14-byte request header) - Raises: - S7ConnectionError: If not connected - NotImplementedError: Until send logic is implemented + Returns: + Response payload (after the 14-byte response header) """ - raise NotImplementedError("S7CommPlus send is not yet implemented.") + if not self._connected: + from ..error import S7ConnectionError + raise S7ConnectionError("Not connected") + + seq_num = self._next_sequence_number() + + # Build request header + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + payload + + # Add S7CommPlus frame header and send + frame = encode_header(self._protocol_version, len(request)) + request + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + + # Parse frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + raise S7ConnectionError("Response too short") + + return response[14:] + + def _create_session(self) -> None: + """Send CreateObject request to establish an S7CommPlus session.""" + seq_num = self._next_sequence_number() + + # Build CreateObject request with NullServer session data + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.CREATE_OBJECT, + 0x0000, + seq_num, + 0x00000000, # No session yet + 0x36, + ) - def receive(self) -> bytes: - """Receive an S7CommPlus frame. + # Add empty request data (minimal CreateObject) + request += struct.pack(">I", 0) - Returns: - S7CommPlus PDU payload (without frame header) + # Wrap in S7CommPlus frame header + frame = encode_header(ProtocolVersion.V1, len(request)) + request - Raises: - S7ConnectionError: If not connected - NotImplementedError: Until receive logic is implemented - """ - raise NotImplementedError("S7CommPlus receive is not yet implemented.") + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + + # Parse S7CommPlus frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + raise S7ConnectionError("CreateObject response too short") + + # Extract session ID from response header + self._session_id = struct.unpack_from(">I", response, 9)[0] + self._protocol_version = version + + logger.debug(f"Session created: id={self._session_id}, version=V{version}") + + def _delete_session(self) -> None: + """Send DeleteObject to close the session.""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.DELETE_OBJECT, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + request += struct.pack(">I", 0) + + frame = encode_header(self._protocol_version, len(request)) + request + self._iso_conn.send_data(frame) + + # Best-effort receive + try: + self._iso_conn.receive_data() + except Exception: + pass def _next_sequence_number(self) -> int: """Get next sequence number and increment.""" @@ -206,13 +299,6 @@ def _setup_ssl_context( ) -> ssl.SSLContext: """Create TLS context for S7CommPlus. - For TIA Portal V17+ PLCs, TLS 1.3 with per-device certificates is - used. The PLC's certificate is generated in TIA Portal and must be - exported and provided as the CA certificate. - - For older PLCs, TLS is not used (the proprietary auth layer handles - session security). - Args: cert_path: Client certificate path (PEM) key_path: Client private key path (PEM) @@ -230,8 +316,6 @@ def _setup_ssl_context( if ca_path: ctx.load_verify_locations(ca_path) else: - # For development/testing: disable certificate verification - # In production, always provide proper certificates ctx.check_hostname = False ctx.verify_mode = ssl.CERT_NONE diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py new file mode 100644 index 00000000..1c1273a3 --- /dev/null +++ b/snap7/s7commplus/server.py @@ -0,0 +1,744 @@ +""" +S7CommPlus server emulator for testing. + +Emulates an S7-1200/1500 PLC for integration testing without real hardware. +Handles the S7CommPlus protocol including: +- COTP connection setup (reuses ISOTCPConnection transport) +- CreateObject session handshake +- Explore (browse registered data blocks and variables) +- GetMultiVariables / SetMultiVariables (read/write by address) +- Internal PLC memory model with thread-safe access + +This server does NOT implement TLS or the proprietary authentication +layers (V2/V3 crypto). It emulates a V1 PLC for testing purposes, +which is sufficient for validating protocol framing, data encoding, +and client logic. + +Usage:: + + server = S7CommPlusServer() + server.register_db(1, {"temperature": ("Real", 0), "pressure": ("Real", 4)}) + server.start(port=11020) + + # ... run tests against localhost:11020 ... + + server.stop() +""" + +import logging +import socket +import struct +import threading +from enum import IntEnum +from typing import Any, Callable, Optional + +from .protocol import ( + DataType, + ElementID, + FunctionCode, + Opcode, + ProtocolVersion, + SoftDataType, +) +from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value + +logger = logging.getLogger(__name__) + + +class CPUState(IntEnum): + """Emulated CPU operational state.""" + + UNKNOWN = 0 + STOP = 1 + RUN = 2 + + +# Mapping from SoftDataType to wire DataType and byte size +_SOFT_TO_WIRE: dict[int, tuple[int, int]] = { + SoftDataType.BOOL: (DataType.BOOL, 1), + SoftDataType.BYTE: (DataType.BYTE, 1), + SoftDataType.CHAR: (DataType.BYTE, 1), + SoftDataType.WORD: (DataType.WORD, 2), + SoftDataType.INT: (DataType.INT, 2), + SoftDataType.DWORD: (DataType.DWORD, 4), + SoftDataType.DINT: (DataType.DINT, 4), + SoftDataType.REAL: (DataType.REAL, 4), + SoftDataType.LREAL: (DataType.LREAL, 8), + SoftDataType.USINT: (DataType.USINT, 1), + SoftDataType.UINT: (DataType.UINT, 2), + SoftDataType.UDINT: (DataType.UDINT, 4), + SoftDataType.SINT: (DataType.SINT, 1), + SoftDataType.ULINT: (DataType.ULINT, 8), + SoftDataType.LINT: (DataType.LINT, 8), + SoftDataType.LWORD: (DataType.LWORD, 8), + SoftDataType.STRING: (DataType.S7STRING, 256), + SoftDataType.WSTRING: (DataType.WSTRING, 512), +} + +# Map string type names to SoftDataType values +_TYPE_NAME_MAP: dict[str, int] = { + "Bool": SoftDataType.BOOL, + "Byte": SoftDataType.BYTE, + "Char": SoftDataType.CHAR, + "Word": SoftDataType.WORD, + "Int": SoftDataType.INT, + "DWord": SoftDataType.DWORD, + "DInt": SoftDataType.DINT, + "Real": SoftDataType.REAL, + "LReal": SoftDataType.LREAL, + "USInt": SoftDataType.USINT, + "UInt": SoftDataType.UINT, + "UDInt": SoftDataType.UDINT, + "SInt": SoftDataType.SINT, + "ULInt": SoftDataType.ULINT, + "LInt": SoftDataType.LINT, + "LWord": SoftDataType.LWORD, + "String": SoftDataType.STRING, + "WString": SoftDataType.WSTRING, +} + + +class DBVariable: + """A variable in a data block.""" + + def __init__(self, name: str, soft_datatype: int, byte_offset: int): + self.name = name + self.soft_datatype = soft_datatype + self.byte_offset = byte_offset + + wire_info = _SOFT_TO_WIRE.get(soft_datatype, (DataType.BYTE, 1)) + self.wire_datatype = wire_info[0] + self.byte_size = wire_info[1] + + def __repr__(self) -> str: + return f"DBVariable({self.name!r}, type={self.soft_datatype}, offset={self.byte_offset})" + + +class DataBlock: + """An emulated PLC data block with named variables.""" + + def __init__(self, number: int, size: int = 1024): + self.number = number + self.data = bytearray(size) + self.variables: dict[str, DBVariable] = {} + self.lock = threading.Lock() + # Assign a unique object ID for the S7CommPlus object tree + self.object_id = 0x00010000 | (number & 0xFFFF) + + def add_variable(self, name: str, type_name: str, byte_offset: int) -> None: + """Register a named variable in this data block. + + Args: + name: Variable name (e.g. "temperature") + type_name: PLC type name (e.g. "Real", "Int", "Bool") + byte_offset: Byte offset within the data block + """ + soft_type = _TYPE_NAME_MAP.get(type_name) + if soft_type is None: + raise ValueError(f"Unknown type name: {type_name!r}") + self.variables[name] = DBVariable(name, soft_type, byte_offset) + + def read(self, offset: int, size: int) -> bytes: + """Read bytes from the data block.""" + with self.lock: + end = min(offset + size, len(self.data)) + result = bytes(self.data[offset:end]) + # Pad with zeros if reading past end + if len(result) < size: + result += b"\x00" * (size - len(result)) + return result + + def write(self, offset: int, data: bytes) -> None: + """Write bytes to the data block.""" + with self.lock: + end = min(offset + len(data), len(self.data)) + self.data[offset:end] = data[: end - offset] + + def read_variable(self, name: str) -> tuple[int, bytes]: + """Read a named variable. + + Returns: + Tuple of (wire_datatype, raw_bytes) + """ + var = self.variables.get(name) + if var is None: + raise KeyError(f"Variable not found: {name!r}") + raw = self.read(var.byte_offset, var.byte_size) + return var.wire_datatype, raw + + def write_variable(self, name: str, data: bytes) -> None: + """Write a named variable.""" + var = self.variables.get(name) + if var is None: + raise KeyError(f"Variable not found: {name!r}") + self.write(var.byte_offset, data) + + +class S7CommPlusServer: + """S7CommPlus PLC emulator for testing. + + Emulates an S7-1200/1500 PLC with: + - Internal data block storage with named variables + - S7CommPlus protocol handling (V1 level) + - Multi-client support (threaded) + - CPU state management + """ + + def __init__(self) -> None: + self._data_blocks: dict[int, DataBlock] = {} + self._cpu_state = CPUState.RUN + self._protocol_version = ProtocolVersion.V1 + self._next_session_id = 1 + + self._server_socket: Optional[socket.socket] = None + self._server_thread: Optional[threading.Thread] = None + self._client_threads: list[threading.Thread] = [] + self._running = False + self._lock = threading.Lock() + self._event_callback: Optional[Callable] = None + + @property + def cpu_state(self) -> CPUState: + return self._cpu_state + + @cpu_state.setter + def cpu_state(self, state: CPUState) -> None: + self._cpu_state = state + + def register_db( + self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024 + ) -> DataBlock: + """Register a data block with named variables. + + Args: + db_number: Data block number (e.g. 1 for DB1) + variables: Dict mapping variable name to (type_name, byte_offset) + e.g. {"temperature": ("Real", 0), "count": ("Int", 4)} + size: Data block size in bytes + + Returns: + The created DataBlock + + Example:: + + server.register_db(1, { + "temperature": ("Real", 0), + "pressure": ("Real", 4), + "running": ("Bool", 8), + "count": ("DInt", 10), + }) + """ + db = DataBlock(db_number, size) + for name, (type_name, offset) in variables.items(): + db.add_variable(name, type_name, offset) + self._data_blocks[db_number] = db + return db + + def register_raw_db(self, db_number: int, data: bytearray) -> DataBlock: + """Register a data block with raw data (no named variables). + + Args: + db_number: Data block number + data: Initial data block content + + Returns: + The created DataBlock + """ + db = DataBlock(db_number, len(data)) + db.data = data + self._data_blocks[db_number] = db + return db + + def get_db(self, db_number: int) -> Optional[DataBlock]: + """Get a registered data block.""" + return self._data_blocks.get(db_number) + + def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: + """Start the server. + + Args: + host: Bind address + port: TCP port to listen on + """ + if self._running: + raise RuntimeError("Server is already running") + + self._server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) + self._server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + self._server_socket.settimeout(1.0) + self._server_socket.bind((host, port)) + self._server_socket.listen(5) + + self._running = True + self._server_thread = threading.Thread( + target=self._server_loop, daemon=True, name="s7commplus-server" + ) + self._server_thread.start() + logger.info(f"S7CommPlus server started on {host}:{port}") + + def stop(self) -> None: + """Stop the server.""" + self._running = False + + if self._server_socket: + try: + self._server_socket.close() + except Exception: + pass + self._server_socket = None + + if self._server_thread: + self._server_thread.join(timeout=5.0) + self._server_thread = None + + for t in self._client_threads: + t.join(timeout=2.0) + self._client_threads.clear() + + logger.info("S7CommPlus server stopped") + + def _server_loop(self) -> None: + """Main server accept loop.""" + while self._running: + try: + if self._server_socket is None: + break + client_sock, address = self._server_socket.accept() + logger.info(f"Client connected from {address}") + t = threading.Thread( + target=self._handle_client, + args=(client_sock, address), + daemon=True, + name=f"s7commplus-client-{address}", + ) + self._client_threads.append(t) + t.start() + except socket.timeout: + continue + except OSError: + break + + def _handle_client(self, client_sock: socket.socket, address: tuple) -> None: + """Handle a single client connection.""" + try: + client_sock.settimeout(5.0) + + # Step 1: COTP handshake + if not self._handle_cotp_connect(client_sock): + return + + # Step 2: S7CommPlus session + session_id = 0 + + while self._running: + try: + # Receive TPKT + COTP DT + S7CommPlus data + data = self._recv_s7commplus_frame(client_sock) + if data is None: + break + + # Process the S7CommPlus request + response = self._process_request(data, session_id) + + if response is not None: + # Check if session ID was assigned + if session_id == 0 and len(response) >= 14: + # Extract session ID from response for tracking + session_id = struct.unpack_from(">I", response, 9)[0] + + self._send_s7commplus_frame(client_sock, response) + + except socket.timeout: + continue + except (ConnectionError, OSError): + break + + except Exception as e: + logger.debug(f"Client handler error: {e}") + finally: + try: + client_sock.close() + except Exception: + pass + logger.info(f"Client disconnected: {address}") + + def _handle_cotp_connect(self, sock: socket.socket) -> bool: + """Handle COTP Connection Request / Confirm.""" + try: + # Receive TPKT header + tpkt_header = self._recv_exact(sock, 4) + version, _, length = struct.unpack(">BBH", tpkt_header) + if version != 3: + return False + + # Receive COTP CR + payload = self._recv_exact(sock, length - 4) + if len(payload) < 7: + return False + + _pdu_len, pdu_type = payload[0], payload[1] + if pdu_type != 0xE0: # COTP CR + return False + + # Parse source ref from CR + src_ref = struct.unpack_from(">H", payload, 4)[0] + + # Build COTP CC response + cc_pdu = struct.pack( + ">BBHHB", + 6, # PDU length + 0xD0, # COTP CC + src_ref, # Destination ref (client's src ref) + 0x0001, # Source ref (our ref) + 0x00, # Class 0 + ) + + # Add PDU size parameter + pdu_size_param = struct.pack(">BBB", 0xC0, 1, 0x0A) # 1024 bytes + cc_pdu = struct.pack(">B", 6 + len(pdu_size_param)) + cc_pdu[1:] + pdu_size_param + + # Send TPKT + CC + tpkt = struct.pack(">BBH", 3, 0, 4 + len(cc_pdu)) + cc_pdu + sock.sendall(tpkt) + + logger.debug("COTP connection established") + return True + + except Exception as e: + logger.debug(f"COTP handshake failed: {e}") + return False + + def _recv_s7commplus_frame(self, sock: socket.socket) -> Optional[bytes]: + """Receive a TPKT/COTP/S7CommPlus frame, return the S7CommPlus payload.""" + try: + # TPKT header + tpkt_header = self._recv_exact(sock, 4) + version, _, length = struct.unpack(">BBH", tpkt_header) + if version != 3 or length <= 4: + return None + + # Remaining data + payload = self._recv_exact(sock, length - 4) + + # Skip COTP DT header (3 bytes: length, type 0xF0, EOT) + if len(payload) < 3 or payload[1] != 0xF0: + return None + + return payload[3:] # S7CommPlus data + + except Exception: + return None + + def _send_s7commplus_frame(self, sock: socket.socket, data: bytes) -> None: + """Send an S7CommPlus frame wrapped in TPKT/COTP.""" + # S7CommPlus header (4 bytes) + data + s7plus_frame = encode_header(self._protocol_version, len(data)) + data + + # COTP DT header + cotp_dt = struct.pack(">BBB", 2, 0xF0, 0x80) + s7plus_frame + + # TPKT + tpkt = struct.pack(">BBH", 3, 0, 4 + len(cotp_dt)) + cotp_dt + sock.sendall(tpkt) + + def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: + """Process an S7CommPlus request and return a response.""" + if len(data) < 4: + return None + + # Parse S7CommPlus frame header + try: + version, data_length, consumed = decode_header(data) + except ValueError: + return None + + payload = data[consumed:] + if len(payload) < 14: + return None + + # Parse request header + opcode = payload[0] + if opcode != Opcode.REQUEST: + return None + + function_code = struct.unpack_from(">H", payload, 3)[0] + seq_num = struct.unpack_from(">H", payload, 7)[0] + req_session_id = struct.unpack_from(">I", payload, 9)[0] + request_data = payload[14:] + + if function_code == FunctionCode.CREATE_OBJECT: + return self._handle_create_object(seq_num, request_data) + elif function_code == FunctionCode.DELETE_OBJECT: + return self._handle_delete_object(seq_num, req_session_id) + elif function_code == FunctionCode.EXPLORE: + return self._handle_explore(seq_num, req_session_id, request_data) + elif function_code == FunctionCode.GET_MULTI_VARIABLES: + return self._handle_get_multi_variables(seq_num, req_session_id, request_data) + elif function_code == FunctionCode.SET_MULTI_VARIABLES: + return self._handle_set_multi_variables(seq_num, req_session_id, request_data) + else: + return self._build_error_response(seq_num, req_session_id, function_code) + + def _handle_create_object(self, seq_num: int, request_data: bytes) -> bytes: + """Handle CreateObject -- establish a session.""" + with self._lock: + session_id = self._next_session_id + self._next_session_id += 1 + + # Build CreateObject response + response = bytearray() + + # Response header + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, # Reserved + FunctionCode.CREATE_OBJECT, + 0x0000, # Reserved + seq_num, + session_id, + 0x00, # Transport flags + ) + + # Return code: success + response += encode_uint32_vlq(0) + + # Object with session info + response += bytes([ElementID.START_OF_OBJECT]) + response += struct.pack(">I", 0x00000001) # Relation ID + response += encode_uint32_vlq(0x00000000) # Class ID + response += encode_uint32_vlq(0x00000000) # Class flags + response += encode_uint32_vlq(0x00000000) # Attribute ID + + # Session ID attribute + response += bytes([ElementID.ATTRIBUTE]) + response += encode_uint32_vlq(0x0131) # ServerSession ID attribute + response += encode_typed_value(DataType.UDINT, session_id) + + # Protocol version attribute + response += bytes([ElementID.ATTRIBUTE]) + response += encode_uint32_vlq(0x0132) # Protocol version attribute + response += encode_typed_value(DataType.USINT, self._protocol_version) + + response += bytes([ElementID.TERMINATING_OBJECT]) + + # Trailing zeros + response += struct.pack(">I", 0) + + return bytes(response) + + def _handle_delete_object(self, seq_num: int, session_id: int) -> bytes: + """Handle DeleteObject -- close a session.""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.DELETE_OBJECT, + 0x0000, + seq_num, + session_id, + 0x00, + ) + response += encode_uint32_vlq(0) # Return code: success + response += struct.pack(">I", 0) + return bytes(response) + + def _handle_explore( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: + """Handle Explore -- return the object tree (registered data blocks).""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.EXPLORE, + 0x0000, + seq_num, + session_id, + 0x00, + ) + response += encode_uint32_vlq(0) # Return code: success + + # Return list of data blocks as objects + for db_num, db in sorted(self._data_blocks.items()): + response += bytes([ElementID.START_OF_OBJECT]) + response += struct.pack(">I", db.object_id) # Relation ID + response += encode_uint32_vlq(0x00000100) # Class: DataBlock + response += encode_uint32_vlq(0x00000000) # Class flags + response += encode_uint32_vlq(0x00000000) # Attribute ID + + # DB number attribute + response += bytes([ElementID.ATTRIBUTE]) + response += encode_uint32_vlq(0x0001) # DB number attribute ID + response += encode_typed_value(DataType.UINT, db_num) + + # DB size attribute + response += bytes([ElementID.ATTRIBUTE]) + response += encode_uint32_vlq(0x0002) # DB size attribute ID + response += encode_typed_value(DataType.UDINT, len(db.data)) + + # Variable list + if db.variables: + response += bytes([ElementID.VARNAME_LIST]) + response += encode_uint32_vlq(len(db.variables)) + for var_name, var in db.variables.items(): + name_bytes = var_name.encode("utf-8") + response += encode_uint32_vlq(len(name_bytes)) + response += name_bytes + response += encode_uint32_vlq(var.soft_datatype) + response += encode_uint32_vlq(var.byte_offset) + + response += bytes([ElementID.TERMINATING_OBJECT]) + + # Final terminator + response += struct.pack(">I", 0) + return bytes(response) + + def _handle_get_multi_variables( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: + """Handle GetMultiVariables -- read variables from data blocks.""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.GET_MULTI_VARIABLES, + 0x0000, + seq_num, + session_id, + 0x00, + ) + response += encode_uint32_vlq(0) # Return code: success + + # Parse request: expect object_id + variable addresses + offset = 0 + items: list[tuple[int, int, int]] = [] # (db_num, byte_offset, byte_size) + + # Simple request format: VLQ item count, then for each item: + # VLQ object_id, VLQ offset, VLQ size + if len(request_data) > 0: + count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + for _ in range(count): + if offset >= len(request_data): + break + obj_id, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_offset, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_size, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + db_num = obj_id & 0xFFFF + items.append((db_num, byte_offset, byte_size)) + + # Read data for each item + response += encode_uint32_vlq(len(items)) + for db_num, byte_offset, byte_size in items: + db = self._data_blocks.get(db_num) + if db is not None: + data = db.read(byte_offset, byte_size) + response += encode_uint32_vlq(0) # Success + response += encode_uint32_vlq(len(data)) + response += data + else: + response += encode_uint32_vlq(1) # Error: not found + response += encode_uint32_vlq(0) + + response += struct.pack(">I", 0) + return bytes(response) + + def _handle_set_multi_variables( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: + """Handle SetMultiVariables -- write variables to data blocks.""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.SET_MULTI_VARIABLES, + 0x0000, + seq_num, + session_id, + 0x00, + ) + + # Parse request: VLQ item count, then for each item: + # VLQ object_id, VLQ offset, VLQ data_length, data bytes + offset = 0 + results: list[int] = [] + + if len(request_data) > 0: + count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + for _ in range(count): + if offset >= len(request_data): + break + obj_id, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_offset, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + data_len, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + data = request_data[offset : offset + data_len] + offset += data_len + + db_num = obj_id & 0xFFFF + db = self._data_blocks.get(db_num) + if db is not None: + db.write(byte_offset, data) + results.append(0) # Success + else: + results.append(1) # Error: not found + + response += encode_uint32_vlq(0) # Return code: success + response += encode_uint32_vlq(len(results)) + for r in results: + response += encode_uint32_vlq(r) + + response += struct.pack(">I", 0) + return bytes(response) + + def _build_error_response( + self, seq_num: int, session_id: int, function_code: int + ) -> bytes: + """Build a generic error response for unsupported function codes.""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.ERROR, + 0x0000, + seq_num, + session_id, + 0x00, + ) + response += encode_uint32_vlq(0x04B1) # Error function code + response += struct.pack(">I", 0) + return bytes(response) + + @staticmethod + def _recv_exact(sock: socket.socket, size: int) -> bytes: + """Receive exactly the specified number of bytes.""" + data = bytearray() + while len(data) < size: + chunk = sock.recv(size - len(data)) + if not chunk: + raise ConnectionError("Connection closed") + data.extend(chunk) + return bytes(data) + + def __enter__(self) -> "S7CommPlusServer": + return self + + def __exit__(self, *args: Any) -> None: + self.stop() diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py new file mode 100644 index 00000000..50deb1ad --- /dev/null +++ b/tests/test_s7commplus_server.py @@ -0,0 +1,306 @@ +"""Integration tests for S7CommPlus server, client, and async client.""" + +import struct +import time +import pytest +import asyncio + +from snap7.s7commplus.server import S7CommPlusServer, CPUState, DataBlock +from snap7.s7commplus.client import S7CommPlusClient +from snap7.s7commplus.async_client import S7CommPlusAsyncClient +from snap7.s7commplus.protocol import ProtocolVersion + +# Use a high port to avoid conflicts +TEST_PORT = 11120 + + +@pytest.fixture() +def server(): + """Create and start an S7CommPlus server with test data blocks.""" + srv = S7CommPlusServer() + + # Register DB1 with named variables + srv.register_db( + 1, + { + "temperature": ("Real", 0), + "pressure": ("Real", 4), + "running": ("Bool", 8), + "count": ("DInt", 10), + "name": ("Int", 14), + }, + ) + + # Register DB2 with raw data + srv.register_raw_db(2, bytearray(256)) + + # Pre-populate some values in DB1 + db1 = srv.get_db(1) + assert db1 is not None + struct.pack_into(">f", db1.data, 0, 23.5) # temperature + struct.pack_into(">f", db1.data, 4, 1.013) # pressure + db1.data[8] = 1 # running = True + struct.pack_into(">i", db1.data, 10, 42) # count + + srv.start(port=TEST_PORT) + time.sleep(0.1) # Let server start + + yield srv + + srv.stop() + + +class TestServer: + """Test the server emulator itself.""" + + def test_register_db(self) -> None: + srv = S7CommPlusServer() + db = srv.register_db(1, {"temp": ("Real", 0)}) + assert db.number == 1 + assert "temp" in db.variables + assert db.variables["temp"].byte_offset == 0 + + def test_register_raw_db(self) -> None: + srv = S7CommPlusServer() + data = bytearray(b"\x01\x02\x03\x04") + db = srv.register_raw_db(10, data) + assert db.read(0, 4) == b"\x01\x02\x03\x04" + + def test_cpu_state(self) -> None: + srv = S7CommPlusServer() + assert srv.cpu_state == CPUState.RUN + srv.cpu_state = CPUState.STOP + assert srv.cpu_state == CPUState.STOP + + def test_data_block_read_write(self) -> None: + db = DataBlock(1, 100) + db.write(0, b"\x01\x02\x03\x04") + assert db.read(0, 4) == b"\x01\x02\x03\x04" + + def test_data_block_named_variable(self) -> None: + db = DataBlock(1, 100) + db.add_variable("temp", "Real", 0) + db.write(0, struct.pack(">f", 42.0)) + wire_type, raw = db.read_variable("temp") + value = struct.unpack(">f", raw)[0] + assert abs(value - 42.0) < 0.001 + + def test_data_block_read_past_end(self) -> None: + db = DataBlock(1, 4) + db.write(0, b"\xFF\xFF\xFF\xFF") + # Read past end should pad with zeros + data = db.read(2, 4) + assert data == b"\xFF\xFF\x00\x00" + + def test_unknown_variable_type(self) -> None: + db = DataBlock(1, 100) + with pytest.raises(ValueError, match="Unknown type name"): + db.add_variable("bad", "NonExistentType", 0) + + +class TestClientServerIntegration: + """Test client against the server emulator.""" + + def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert client.session_id != 0 + assert client.protocol_version == ProtocolVersion.V1 + client.disconnect() + assert not client.connected + + def test_context_manager(self, server: S7CommPlusServer) -> None: + with S7CommPlusClient() as client: + client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert not client.connected + + def test_read_real(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + data = client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 + finally: + client.disconnect() + + def test_read_multiple_values(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + # Read temperature and pressure + data = client.db_read(1, 0, 8) + temp = struct.unpack_from(">f", data, 0)[0] + pressure = struct.unpack_from(">f", data, 4)[0] + assert abs(temp - 23.5) < 0.001 + assert abs(pressure - 1.013) < 0.001 + finally: + client.disconnect() + + def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + # Write a new temperature + client.db_write(1, 0, struct.pack(">f", 99.9)) + + # Read it back + data = client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 99.9) < 0.1 + finally: + client.disconnect() + + def test_write_dint(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + # Write count + client.db_write(1, 10, struct.pack(">i", 12345)) + + # Read it back + data = client.db_read(1, 10, 4) + value = struct.unpack(">i", data)[0] + assert value == 12345 + finally: + client.disconnect() + + def test_read_db2_raw(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + # DB2 should be all zeros + data = client.db_read(2, 0, 10) + assert data == b"\x00" * 10 + finally: + client.disconnect() + + def test_multi_read(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + results = client.db_read_multi([ + (1, 0, 4), # temperature from DB1 + (1, 4, 4), # pressure from DB1 + (2, 0, 4), # zeros from DB2 + ]) + assert len(results) == 3 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.001 + assert results[2] == b"\x00\x00\x00\x00" + finally: + client.disconnect() + + def test_explore(self, server: S7CommPlusServer) -> None: + client = S7CommPlusClient() + client.connect("127.0.0.1", port=TEST_PORT) + try: + response = client.explore() + # Response should contain data about registered DBs + assert len(response) > 0 + finally: + client.disconnect() + + def test_server_data_persists_across_clients( + self, server: S7CommPlusServer + ) -> None: + # Client 1 writes + c1 = S7CommPlusClient() + c1.connect("127.0.0.1", port=TEST_PORT) + c1.db_write(2, 0, b"\xDE\xAD\xBE\xEF") + c1.disconnect() + + # Client 2 reads + c2 = S7CommPlusClient() + c2.connect("127.0.0.1", port=TEST_PORT) + data = c2.db_read(2, 0, 4) + c2.disconnect() + + assert data == b"\xDE\xAD\xBE\xEF" + + def test_multiple_concurrent_clients( + self, server: S7CommPlusServer + ) -> None: + clients = [] + for _ in range(3): + c = S7CommPlusClient() + c.connect("127.0.0.1", port=TEST_PORT) + clients.append(c) + + # All should have different session IDs + session_ids = {c.session_id for c in clients} + assert len(session_ids) == 3 + + for c in clients: + c.disconnect() + + +@pytest.mark.asyncio +class TestAsyncClientServerIntegration: + """Test async client against the server emulator.""" + + async def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + client = S7CommPlusAsyncClient() + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert client.session_id != 0 + await client.disconnect() + assert not client.connected + + async def test_async_context_manager(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert not client.connected + + async def test_read_real(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 + + async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + await client.db_write(1, 0, struct.pack(">f", 77.7)) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 77.7) < 0.1 + + async def test_multi_read(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + results = await client.db_read_multi([ + (1, 0, 4), + (1, 10, 4), + ]) + assert len(results) == 2 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.1 # May be modified by earlier test + + async def test_explore(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + response = await client.explore() + assert len(response) > 0 + + async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: + """Test that asyncio.Lock prevents interleaved requests.""" + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + + async def read_temp() -> float: + data = await client.db_read(1, 0, 4) + return struct.unpack(">f", data)[0] + + # Fire multiple concurrent reads + results = await asyncio.gather( + read_temp(), read_temp(), read_temp() + ) + # All should succeed (lock serializes them) + assert len(results) == 3 + for r in results: + assert isinstance(r, float) From 015314c825e0f2b1eb30efbd9466fad23f356442 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:35:35 +0200 Subject: [PATCH 03/27] Clean up security-focused wording in S7CommPlus docstrings Reframe protocol version descriptions around interoperability rather than security vulnerabilities. Remove CVE references and replace implementation-specific language with neutral terminology. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/__init__.py | 6 +++--- snap7/s7commplus/connection.py | 12 ++++++------ snap7/s7commplus/protocol.py | 8 ++++---- 3 files changed, 13 insertions(+), 13 deletions(-) diff --git a/snap7/s7commplus/__init__.py b/snap7/s7commplus/__init__.py index 3617a832..f8ff995a 100644 --- a/snap7/s7commplus/__init__.py +++ b/snap7/s7commplus/__init__.py @@ -7,9 +7,9 @@ Supported PLC / firmware targets:: - V1: S7-1200 FW V4.0+ (trivial anti-replay) - V2: S7-1200/1500 older FW (proprietary session auth) - V3: S7-1200/1500 pre-TIA V17 (ECC key exchange) + V1: S7-1200 FW V4.0+ (simple session handshake) + V2: S7-1200/1500 older FW (session authentication) + V3: S7-1200/1500 pre-TIA V17 (public-key key exchange) V3 + TLS: TIA Portal V17+ (TLS 1.3 with per-device certs) Protocol stack:: diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 76362193..b9d0f91e 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -4,9 +4,9 @@ Establishes an ISO-on-TCP connection to S7-1200/1500 PLCs using the S7CommPlus protocol, with support for all protocol versions: -- V1: Early S7-1200 (FW >= V4.0). Trivial anti-replay (challenge + 0x80). -- V2: Adds integrity checking and proprietary session authentication. -- V3: Adds ECC-based key exchange. +- V1: Early S7-1200 (FW >= V4.0). Simple session handshake. +- V2: Adds integrity checking and session authentication. +- V3: Adds public-key-based key exchange. - V3 + TLS: TIA Portal V17+. Standard TLS 1.3 with per-device certificates. The wire protocol (VLQ encoding, data types, function codes, object model) is @@ -24,9 +24,9 @@ Version-specific authentication after step 4:: - V1: session_response = challenge_byte + 0x80 - V2: Proprietary HMAC-SHA256 / AES session key derivation - V3 (no TLS): ECC-based key exchange (requires product-family keys) + V1: Simple challenge-response handshake + V2: Session key derivation and integrity checking + V3 (no TLS): Public-key key exchange V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 13db6764..9ec4ec53 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -18,12 +18,12 @@ class ProtocolVersion(IntEnum): """S7CommPlus protocol versions. - V1: Early S7-1200 FW V4.0 -- trivial anti-replay (challenge + 0x80) - V2: Adds integrity checking and proprietary session authentication - V3: Adds ECC-based key exchange (broken via CVE-2022-38465) + V1: Early S7-1200 FW V4.0 -- simple session handshake + V2: Adds integrity checking and session authentication + V3: Adds public-key-based key exchange TLS: TIA Portal V17+ -- standard TLS 1.3 with per-device certificates - For new implementations, only TLS (V3 + InitSsl) should be targeted. + For new implementations, TLS (V3 + InitSsl) is the recommended target. """ V1 = 0x01 From 81b9e9f6e3f68dc1e5b18d3780e0981b0a2c6eb5 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:39:49 +0200 Subject: [PATCH 04/27] Fix CI: remove pytest-asyncio dependency, fix formatting Rewrite async tests to use asyncio.run() instead of @pytest.mark.asyncio since pytest-asyncio is not a project dependency. Also apply ruff formatting fixes. Co-Authored-By: Claude Opus 4.6 --- tests/test_s7commplus_server.py | 155 ++++++++++++++++++-------------- 1 file changed, 86 insertions(+), 69 deletions(-) diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index 50deb1ad..db0c81a1 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -87,10 +87,10 @@ def test_data_block_named_variable(self) -> None: def test_data_block_read_past_end(self) -> None: db = DataBlock(1, 4) - db.write(0, b"\xFF\xFF\xFF\xFF") + db.write(0, b"\xff\xff\xff\xff") # Read past end should pad with zeros data = db.read(2, 4) - assert data == b"\xFF\xFF\x00\x00" + assert data == b"\xff\xff\x00\x00" def test_unknown_variable_type(self) -> None: db = DataBlock(1, 100) @@ -181,11 +181,13 @@ def test_multi_read(self, server: S7CommPlusServer) -> None: client = S7CommPlusClient() client.connect("127.0.0.1", port=TEST_PORT) try: - results = client.db_read_multi([ - (1, 0, 4), # temperature from DB1 - (1, 4, 4), # pressure from DB1 - (2, 0, 4), # zeros from DB2 - ]) + results = client.db_read_multi( + [ + (1, 0, 4), # temperature from DB1 + (1, 4, 4), # pressure from DB1 + (2, 0, 4), # zeros from DB2 + ] + ) assert len(results) == 3 temp = struct.unpack(">f", results[0])[0] assert abs(temp - 23.5) < 0.001 @@ -203,13 +205,11 @@ def test_explore(self, server: S7CommPlusServer) -> None: finally: client.disconnect() - def test_server_data_persists_across_clients( - self, server: S7CommPlusServer - ) -> None: + def test_server_data_persists_across_clients(self, server: S7CommPlusServer) -> None: # Client 1 writes c1 = S7CommPlusClient() c1.connect("127.0.0.1", port=TEST_PORT) - c1.db_write(2, 0, b"\xDE\xAD\xBE\xEF") + c1.db_write(2, 0, b"\xde\xad\xbe\xef") c1.disconnect() # Client 2 reads @@ -218,11 +218,9 @@ def test_server_data_persists_across_clients( data = c2.db_read(2, 0, 4) c2.disconnect() - assert data == b"\xDE\xAD\xBE\xEF" + assert data == b"\xde\xad\xbe\xef" - def test_multiple_concurrent_clients( - self, server: S7CommPlusServer - ) -> None: + def test_multiple_concurrent_clients(self, server: S7CommPlusServer) -> None: clients = [] for _ in range(3): c = S7CommPlusClient() @@ -237,70 +235,89 @@ def test_multiple_concurrent_clients( c.disconnect() -@pytest.mark.asyncio class TestAsyncClientServerIntegration: """Test async client against the server emulator.""" - async def test_connect_disconnect(self, server: S7CommPlusServer) -> None: - client = S7CommPlusAsyncClient() - await client.connect("127.0.0.1", port=TEST_PORT) - assert client.connected - assert client.session_id != 0 - await client.disconnect() - assert not client.connected - - async def test_async_context_manager(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: + def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + client = S7CommPlusAsyncClient() await client.connect("127.0.0.1", port=TEST_PORT) assert client.connected - assert not client.connected + assert client.session_id != 0 + await client.disconnect() + assert not client.connected - async def test_read_real(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 23.5) < 0.001 + asyncio.run(_test()) - async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - await client.db_write(1, 0, struct.pack(">f", 77.7)) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 77.7) < 0.1 + def test_async_context_manager(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert not client.connected - async def test_multi_read(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - results = await client.db_read_multi([ - (1, 0, 4), - (1, 10, 4), - ]) - assert len(results) == 2 - temp = struct.unpack(">f", results[0])[0] - assert abs(temp - 23.5) < 0.1 # May be modified by earlier test + asyncio.run(_test()) - async def test_explore(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - response = await client.explore() - assert len(response) > 0 + def test_read_real(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 - async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: - """Test that asyncio.Lock prevents interleaved requests.""" - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) + asyncio.run(_test()) - async def read_temp() -> float: + def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + await client.db_write(1, 0, struct.pack(">f", 77.7)) data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] + value = struct.unpack(">f", data)[0] + assert abs(value - 77.7) < 0.1 - # Fire multiple concurrent reads - results = await asyncio.gather( - read_temp(), read_temp(), read_temp() - ) - # All should succeed (lock serializes them) - assert len(results) == 3 - for r in results: - assert isinstance(r, float) + asyncio.run(_test()) + + def test_multi_read(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + results = await client.db_read_multi( + [ + (1, 0, 4), + (1, 10, 4), + ] + ) + assert len(results) == 2 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.1 # May be modified by earlier test + + asyncio.run(_test()) + + def test_explore(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + response = await client.explore() + assert len(response) > 0 + + asyncio.run(_test()) + + def test_concurrent_reads(self, server: S7CommPlusServer) -> None: + """Test that asyncio.Lock prevents interleaved requests.""" + + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + + async def read_temp() -> float: + data = await client.db_read(1, 0, 4) + return struct.unpack(">f", data)[0] + + results = await asyncio.gather(read_temp(), read_temp(), read_temp()) + assert len(results) == 3 + for r in results: + assert isinstance(r, float) + + asyncio.run(_test()) From a399d1967829a20e5f444099d78745ddd45b4fd2 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:41:34 +0200 Subject: [PATCH 05/27] Add pytest-asyncio dependency and use native async tests Add pytest-asyncio to test dependencies and set asyncio_mode=auto. Restore async test methods with @pytest.mark.asyncio instead of asyncio.run() wrappers. Co-Authored-By: Claude Opus 4.6 --- pyproject.toml | 1 + tests/test_s7commplus_server.py | 125 +++++++++++++------------------- 2 files changed, 53 insertions(+), 73 deletions(-) diff --git a/pyproject.toml b/pyproject.toml index f040cc8d..2783274d 100644 --- a/pyproject.toml +++ b/pyproject.toml @@ -57,6 +57,7 @@ markers =[ "server", "util" ] +asyncio_mode = "auto" [tool.mypy] ignore_missing_imports = true diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index db0c81a1..356bd6f0 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -235,89 +235,68 @@ def test_multiple_concurrent_clients(self, server: S7CommPlusServer) -> None: c.disconnect() +@pytest.mark.asyncio class TestAsyncClientServerIntegration: """Test async client against the server emulator.""" - def test_connect_disconnect(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - client = S7CommPlusAsyncClient() + async def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + client = S7CommPlusAsyncClient() + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert client.session_id != 0 + await client.disconnect() + assert not client.connected + + async def test_async_context_manager(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: await client.connect("127.0.0.1", port=TEST_PORT) assert client.connected - assert client.session_id != 0 - await client.disconnect() - assert not client.connected - - asyncio.run(_test()) - - def test_async_context_manager(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - assert client.connected - assert not client.connected - - asyncio.run(_test()) - - def test_read_real(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 23.5) < 0.001 - - asyncio.run(_test()) - - def test_write_and_read_back(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - await client.db_write(1, 0, struct.pack(">f", 77.7)) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 77.7) < 0.1 + assert not client.connected - asyncio.run(_test()) + async def test_read_real(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 - def test_multi_read(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - results = await client.db_read_multi( - [ - (1, 0, 4), - (1, 10, 4), - ] - ) - assert len(results) == 2 - temp = struct.unpack(">f", results[0])[0] - assert abs(temp - 23.5) < 0.1 # May be modified by earlier test - - asyncio.run(_test()) + async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + await client.db_write(1, 0, struct.pack(">f", 77.7)) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 77.7) < 0.1 - def test_explore(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - response = await client.explore() - assert len(response) > 0 + async def test_multi_read(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + results = await client.db_read_multi( + [ + (1, 0, 4), + (1, 10, 4), + ] + ) + assert len(results) == 2 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.1 # May be modified by earlier test - asyncio.run(_test()) + async def test_explore(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + response = await client.explore() + assert len(response) > 0 - def test_concurrent_reads(self, server: S7CommPlusServer) -> None: + async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: """Test that asyncio.Lock prevents interleaved requests.""" + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - - async def read_temp() -> float: - data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] - - results = await asyncio.gather(read_temp(), read_temp(), read_temp()) - assert len(results) == 3 - for r in results: - assert isinstance(r, float) + async def read_temp() -> float: + data = await client.db_read(1, 0, 4) + return struct.unpack(">f", data)[0] - asyncio.run(_test()) + results = await asyncio.gather(read_temp(), read_temp(), read_temp()) + assert len(results) == 3 + for r in results: + assert isinstance(r, float) From e5ac49e2e044a573fb31c9b40cb58492664b6377 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 2 Mar 2026 10:01:25 +0200 Subject: [PATCH 06/27] Fix CI and add S7CommPlus end-to-end tests Fix ruff formatting violations and mypy type errors in S7CommPlus code that caused pre-commit CI to fail. Add end-to-end test suite for validating S7CommPlus against a real S7-1200/1500 PLC. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 42 ++-- snap7/s7commplus/client.py | 16 +- snap7/s7commplus/codec.py | 4 +- snap7/s7commplus/connection.py | 42 ++-- snap7/s7commplus/server.py | 28 +-- snap7/s7commplus/vlq.py | 1 + tests/conftest.py | 10 +- tests/test_s7commplus_e2e.py | 410 +++++++++++++++++++++++++++++++ tests/test_s7commplus_server.py | 6 +- 9 files changed, 474 insertions(+), 85 deletions(-) create mode 100644 tests/test_s7commplus_e2e.py diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index dfab3012..b3eb751d 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -89,8 +89,7 @@ async def connect( self._connected = True logger.info( - f"Async S7CommPlus connected to {host}:{port}, " - f"version=V{self._protocol_version}, session={self._session_id}" + f"Async S7CommPlus connected to {host}:{port}, version=V{self._protocol_version}, session={self._session_id}" ) except Exception: await self.disconnect() @@ -136,9 +135,7 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = await self._send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) offset = 0 _, consumed = decode_uint32_vlq(response, offset) @@ -175,18 +172,14 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data - response = await self._send_request( - FunctionCode.SET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) offset = 0 return_code, consumed = decode_uint32_vlq(response, offset) if return_code != 0: raise RuntimeError(f"Write failed with return code {return_code}") - async def db_read_multi( - self, items: list[tuple[int, int, int]] - ) -> list[bytes]: + async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. Args: @@ -203,9 +196,7 @@ async def db_read_multi( payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = await self._send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) offset = 0 _, consumed = decode_uint32_vlq(response, offset) @@ -245,16 +236,19 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: seq_num = self._next_sequence_number() - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - function_code, - 0x0000, - seq_num, - self._session_id, - 0x36, - ) + payload + request = ( + struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + function_code, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + + payload + ) frame = encode_header(self._protocol_version, len(request)) + request await self._send_cotp_dt(frame) diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 59d82d8c..ad38c860 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -140,9 +140,7 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = self._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) # Parse response offset = 0 @@ -188,9 +186,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data - response = self._connection.send_request( - FunctionCode.SET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) # Parse response - check return code offset = 0 @@ -200,9 +196,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: if return_code != 0: raise RuntimeError(f"Write failed with return code {return_code}") - def db_read_multi( - self, items: list[tuple[int, int, int]] - ) -> list[bytes]: + def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. Args: @@ -222,9 +216,7 @@ def db_read_multi( payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = self._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) # Parse response offset = 0 diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py index 54c6711c..79a7ec36 100644 --- a/snap7/s7commplus/codec.py +++ b/snap7/s7commplus/codec.py @@ -284,9 +284,9 @@ def encode_typed_value(datatype: int, value: Any) -> bytes: elif datatype == DataType.AID: return tag + encode_uint32_vlq(value) elif datatype == DataType.WSTRING: - encoded = value.encode("utf-8") + encoded: bytes = value.encode("utf-8") return tag + encode_uint32_vlq(len(encoded)) + encoded elif datatype == DataType.BLOB: - return tag + encode_uint32_vlq(len(value)) + value + return bytes(tag + encode_uint32_vlq(len(value)) + value) else: raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index b9d0f91e..c425810f 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -136,21 +136,15 @@ def connect( # Step 3: Version-specific authentication if use_tls and self._protocol_version >= ProtocolVersion.V3: # TODO: Send InitSsl request and perform TLS handshake - raise NotImplementedError( - "TLS authentication is not yet implemented. " - "Use use_tls=False for V1 connections." - ) + raise NotImplementedError("TLS authentication is not yet implemented. Use use_tls=False for V1 connections.") elif self._protocol_version == ProtocolVersion.V2: # TODO: Proprietary HMAC-SHA256/AES session auth - raise NotImplementedError( - "V2 authentication is not yet implemented." - ) + raise NotImplementedError("V2 authentication is not yet implemented.") # V1: No further authentication needed self._connected = True logger.info( - f"S7CommPlus connected to {self.host}:{self.port}, " - f"version=V{self._protocol_version}, session={self._session_id}" + f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" ) except Exception: @@ -172,9 +166,7 @@ def disconnect(self) -> None: self._protocol_version = 0 self._iso_conn.disconnect() - def send_request( - self, function_code: int, payload: bytes = b"" - ) -> bytes: + def send_request(self, function_code: int, payload: bytes = b"") -> bytes: """Send an S7CommPlus request and receive the response. Args: @@ -186,21 +178,25 @@ def send_request( """ if not self._connected: from ..error import S7ConnectionError + raise S7ConnectionError("Not connected") seq_num = self._next_sequence_number() # Build request header - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - function_code, - 0x0000, # Reserved - seq_num, - self._session_id, - 0x36, # Transport flags - ) + payload + request = ( + struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + + payload + ) # Add S7CommPlus frame header and send frame = encode_header(self._protocol_version, len(request)) + request @@ -215,6 +211,7 @@ def send_request( if len(response) < 14: from ..error import S7ConnectionError + raise S7ConnectionError("Response too short") return response[14:] @@ -252,6 +249,7 @@ def _create_session(self) -> None: if len(response) < 14: from ..error import S7ConnectionError + raise S7ConnectionError("CreateObject response too short") # Extract session ID from response header diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 1c1273a3..f4b827aa 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -196,7 +196,7 @@ def __init__(self) -> None: self._client_threads: list[threading.Thread] = [] self._running = False self._lock = threading.Lock() - self._event_callback: Optional[Callable] = None + self._event_callback: Optional[Callable[..., None]] = None @property def cpu_state(self) -> CPUState: @@ -206,9 +206,7 @@ def cpu_state(self) -> CPUState: def cpu_state(self, state: CPUState) -> None: self._cpu_state = state - def register_db( - self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024 - ) -> DataBlock: + def register_db(self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024) -> DataBlock: """Register a data block with named variables. Args: @@ -271,9 +269,7 @@ def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: self._server_socket.listen(5) self._running = True - self._server_thread = threading.Thread( - target=self._server_loop, daemon=True, name="s7commplus-server" - ) + self._server_thread = threading.Thread(target=self._server_loop, daemon=True, name="s7commplus-server") self._server_thread.start() logger.info(f"S7CommPlus server started on {host}:{port}") @@ -319,7 +315,7 @@ def _server_loop(self) -> None: except OSError: break - def _handle_client(self, client_sock: socket.socket, address: tuple) -> None: + def _handle_client(self, client_sock: socket.socket, address: tuple[str, int]) -> None: """Handle a single client connection.""" try: client_sock.settimeout(5.0) @@ -545,9 +541,7 @@ def _handle_delete_object(self, seq_num: int, session_id: int) -> bytes: response += struct.pack(">I", 0) return bytes(response) - def _handle_explore( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle Explore -- return the object tree (registered data blocks).""" response = bytearray() response += struct.pack( @@ -597,9 +591,7 @@ def _handle_explore( response += struct.pack(">I", 0) return bytes(response) - def _handle_get_multi_variables( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle GetMultiVariables -- read variables from data blocks.""" response = bytearray() response += struct.pack( @@ -653,9 +645,7 @@ def _handle_get_multi_variables( response += struct.pack(">I", 0) return bytes(response) - def _handle_set_multi_variables( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle SetMultiVariables -- write variables to data blocks.""" response = bytearray() response += struct.pack( @@ -707,9 +697,7 @@ def _handle_set_multi_variables( response += struct.pack(">I", 0) return bytes(response) - def _build_error_response( - self, seq_num: int, session_id: int, function_code: int - ) -> bytes: + def _build_error_response(self, seq_num: int, session_id: int, function_code: int) -> bytes: """Build a generic error response for unsupported function codes.""" response = bytearray() response += struct.pack( diff --git a/snap7/s7commplus/vlq.py b/snap7/s7commplus/vlq.py index 3c739975..19e9c388 100644 --- a/snap7/s7commplus/vlq.py +++ b/snap7/s7commplus/vlq.py @@ -20,6 +20,7 @@ Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs """ + def encode_uint32_vlq(value: int) -> bytes: """Encode an unsigned 32-bit integer as VLQ. diff --git a/tests/conftest.py b/tests/conftest.py index c0e3eac1..4e53e6d3 100644 --- a/tests/conftest.py +++ b/tests/conftest.py @@ -65,8 +65,13 @@ def pytest_configure(config: pytest.Config) -> None: def pytest_collection_modifyitems(config: pytest.Config, items: list[pytest.Item]) -> None: """Propagate CLI options and skip e2e tests unless --e2e flag is provided.""" - # Propagate CLI options to test_client_e2e module globals - for mod_name in ["tests.test_client_e2e", "test_client_e2e"]: + # Propagate CLI options to e2e test module globals + for mod_name in [ + "tests.test_client_e2e", + "test_client_e2e", + "tests.test_s7commplus_e2e", + "test_s7commplus_e2e", + ]: e2e = sys.modules.get(mod_name) if e2e is not None: e2e.PLC_IP = str(config.getoption("--plc-ip")) @@ -75,7 +80,6 @@ def pytest_collection_modifyitems(config: pytest.Config, items: list[pytest.Item e2e.PLC_PORT = int(config.getoption("--plc-port")) e2e.DB_READ_ONLY = int(config.getoption("--plc-db-read")) e2e.DB_READ_WRITE = int(config.getoption("--plc-db-write")) - break # Skip e2e tests if flag not provided if config.getoption("--e2e"): diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py new file mode 100644 index 00000000..0ae37ea6 --- /dev/null +++ b/tests/test_s7commplus_e2e.py @@ -0,0 +1,410 @@ +"""End-to-end tests for S7CommPlus client against a real Siemens S7-1200/1500 PLC. + +These tests require a real PLC connection. Run with: + + pytest tests/test_s7commplus_e2e.py --e2e --plc-ip=YOUR_PLC_IP + +Available options: + --e2e Enable e2e tests (required) + --plc-ip PLC IP address (default: 10.10.10.100) + --plc-rack PLC rack number (default: 0) + --plc-slot PLC slot number (default: 1) + --plc-port PLC TCP port (default: 102) + --plc-db-read Read-only DB number (default: 1) + --plc-db-write Read-write DB number (default: 2) + +The PLC needs two data blocks configured with the same layout as the +regular S7 e2e tests: + +DB1 "Read_only" - Read-only data block with predefined values: + int1: Int = 10 (offset 0, 2 bytes) + int2: Int = 255 (offset 2, 2 bytes) + float1: Real = 123.45 (offset 4, 4 bytes) + float2: Real = 543.21 (offset 8, 4 bytes) + byte1: Byte = 0x0F (offset 12, 1 byte) + byte2: Byte = 0xF0 (offset 13, 1 byte) + word1: Word = 0xABCD (offset 14, 2 bytes) + word2: Word = 0x1234 (offset 16, 2 bytes) + dword1: DWord = 0x12345678 (offset 18, 4 bytes) + dword2: DWord = 0x89ABCDEF (offset 22, 4 bytes) + dint1: DInt = 2147483647 (offset 26, 4 bytes) + dint2: DInt = 42 (offset 30, 4 bytes) + char1: Char = 'F' (offset 34, 1 byte) + char2: Char = '-' (offset 35, 1 byte) + bool0-bool7: Bool (offset 36, 1 byte, value: 0x01) + +DB2 "Data_block_2" - Read/write data block with same structure. + +Note: S7CommPlus targets S7-1200/1500 PLCs, which use optimized block +access. Ensure data blocks have "Optimized block access" disabled in +TIA Portal so that byte offsets match the layout above. +""" + +import os +import struct +import unittest + +import pytest + +from snap7.s7commplus.client import S7CommPlusClient + +# ============================================================================= +# PLC Connection Configuration +# These can be overridden via pytest command line options or environment variables +# ============================================================================= +PLC_IP = os.environ.get("PLC_IP", "10.10.10.100") +PLC_RACK = int(os.environ.get("PLC_RACK", "0")) +PLC_SLOT = int(os.environ.get("PLC_SLOT", "1")) +PLC_PORT = int(os.environ.get("PLC_PORT", "102")) + +# Data block numbers +DB_READ_ONLY = int(os.environ.get("PLC_DB_READ", "1")) +DB_READ_WRITE = int(os.environ.get("PLC_DB_WRITE", "2")) + + +# ============================================================================= +# DB Structure - Byte offsets for each variable (same as regular S7 e2e tests) +# ============================================================================= +OFFSET_INT1 = 0 # Int (2 bytes) +OFFSET_INT2 = 2 # Int (2 bytes) +OFFSET_FLOAT1 = 4 # Real (4 bytes) +OFFSET_FLOAT2 = 8 # Real (4 bytes) +OFFSET_BYTE1 = 12 # Byte (1 byte) +OFFSET_BYTE2 = 13 # Byte (1 byte) +OFFSET_WORD1 = 14 # Word (2 bytes) +OFFSET_WORD2 = 16 # Word (2 bytes) +OFFSET_DWORD1 = 18 # DWord (4 bytes) +OFFSET_DWORD2 = 22 # DWord (4 bytes) +OFFSET_DINT1 = 26 # DInt (4 bytes) +OFFSET_DINT2 = 30 # DInt (4 bytes) +OFFSET_CHAR1 = 34 # Char (1 byte) +OFFSET_CHAR2 = 35 # Char (1 byte) +OFFSET_BOOLS = 36 # 8 Bools packed in 1 byte + +# Total size of DB +DB_SIZE = 37 + +# ============================================================================= +# Expected values from DB1 "Read_only" +# ============================================================================= +EXPECTED_INT1 = 10 +EXPECTED_INT2 = 255 +EXPECTED_FLOAT1 = 123.45 +EXPECTED_FLOAT2 = 543.21 +EXPECTED_BYTE1 = 0x0F +EXPECTED_BYTE2 = 0xF0 +EXPECTED_WORD1 = 0xABCD +EXPECTED_WORD2 = 0x1234 +EXPECTED_DWORD1 = 0x12345678 +EXPECTED_DWORD2 = 0x89ABCDEF +EXPECTED_DINT1 = 2147483647 +EXPECTED_DINT2 = 42 +EXPECTED_CHAR1 = "F" +EXPECTED_CHAR2 = "-" +EXPECTED_BOOL0 = True +EXPECTED_BOOL1 = False + + +# ============================================================================= +# Test Classes +# ============================================================================= + + +@pytest.mark.e2e +class TestS7CommPlusConnection(unittest.TestCase): + """Tests for S7CommPlus connection.""" + + def test_connect_disconnect(self) -> None: + """Test connect() and disconnect().""" + client = S7CommPlusClient() + client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + self.assertTrue(client.connected) + self.assertGreater(client.protocol_version, 0) + self.assertGreater(client.session_id, 0) + client.disconnect() + self.assertFalse(client.connected) + + def test_context_manager(self) -> None: + """Test S7CommPlusClient as context manager.""" + with S7CommPlusClient() as client: + client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + self.assertTrue(client.connected) + # After exiting context, client should be disconnected + + def test_properties_before_connect(self) -> None: + """Test properties return defaults before connection.""" + client = S7CommPlusClient() + self.assertFalse(client.connected) + self.assertEqual(0, client.protocol_version) + self.assertEqual(0, client.session_id) + + +@pytest.mark.e2e +class TestS7CommPlusDBRead(unittest.TestCase): + """Tests for db_read() - reading from DB1 (read-only).""" + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_db_read_int(self) -> None: + """Test db_read() for Int values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_INT1, 2) + value = struct.unpack(">h", data)[0] + self.assertEqual(EXPECTED_INT1, value) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_INT2, 2) + value = struct.unpack(">h", data)[0] + self.assertEqual(EXPECTED_INT2, value) + + def test_db_read_real(self) -> None: + """Test db_read() for Real values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_FLOAT1, 4) + value = struct.unpack(">f", data)[0] + self.assertAlmostEqual(EXPECTED_FLOAT1, value, places=2) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_FLOAT2, 4) + value = struct.unpack(">f", data)[0] + self.assertAlmostEqual(EXPECTED_FLOAT2, value, places=2) + + def test_db_read_byte(self) -> None: + """Test db_read() for Byte values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_BYTE1, 1) + self.assertEqual(EXPECTED_BYTE1, data[0]) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_BYTE2, 1) + self.assertEqual(EXPECTED_BYTE2, data[0]) + + def test_db_read_word(self) -> None: + """Test db_read() for Word values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_WORD1, 2) + value = struct.unpack(">H", data)[0] + self.assertEqual(EXPECTED_WORD1, value) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_WORD2, 2) + value = struct.unpack(">H", data)[0] + self.assertEqual(EXPECTED_WORD2, value) + + def test_db_read_dword(self) -> None: + """Test db_read() for DWord values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_DWORD1, 4) + value = struct.unpack(">I", data)[0] + self.assertEqual(EXPECTED_DWORD1, value) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_DWORD2, 4) + value = struct.unpack(">I", data)[0] + self.assertEqual(EXPECTED_DWORD2, value) + + def test_db_read_dint(self) -> None: + """Test db_read() for DInt values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_DINT1, 4) + value = struct.unpack(">i", data)[0] + self.assertEqual(EXPECTED_DINT1, value) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_DINT2, 4) + value = struct.unpack(">i", data)[0] + self.assertEqual(EXPECTED_DINT2, value) + + def test_db_read_char(self) -> None: + """Test db_read() for Char values.""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_CHAR1, 1) + self.assertEqual(EXPECTED_CHAR1, chr(data[0])) + + data = self.client.db_read(DB_READ_ONLY, OFFSET_CHAR2, 1) + self.assertEqual(EXPECTED_CHAR2, chr(data[0])) + + def test_db_read_bool(self) -> None: + """Test db_read() for Bool values (packed in byte).""" + data = self.client.db_read(DB_READ_ONLY, OFFSET_BOOLS, 1) + self.assertEqual(EXPECTED_BOOL0, bool(data[0] & 0x01)) + self.assertEqual(EXPECTED_BOOL1, bool(data[0] & 0x02)) + + def test_db_read_entire_block(self) -> None: + """Test db_read() for entire DB.""" + data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) + self.assertEqual(DB_SIZE, len(data)) + + # Verify a few values + int1 = struct.unpack(">h", data[OFFSET_INT1 : OFFSET_INT1 + 2])[0] + self.assertEqual(EXPECTED_INT1, int1) + + float1 = struct.unpack(">f", data[OFFSET_FLOAT1 : OFFSET_FLOAT1 + 4])[0] + self.assertAlmostEqual(EXPECTED_FLOAT1, float1, places=2) + + dword1 = struct.unpack(">I", data[OFFSET_DWORD1 : OFFSET_DWORD1 + 4])[0] + self.assertEqual(EXPECTED_DWORD1, dword1) + + +@pytest.mark.e2e +class TestS7CommPlusDBWrite(unittest.TestCase): + """Tests for db_write() - writing to DB2 (read/write).""" + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_db_write_int(self) -> None: + """Test db_write() for Int values.""" + test_value = 10 + data = struct.pack(">h", test_value) + self.client.db_write(DB_READ_WRITE, OFFSET_INT1, data) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_INT1, 2) + self.assertEqual(test_value, struct.unpack(">h", result)[0]) + + def test_db_write_real(self) -> None: + """Test db_write() for Real values.""" + test_value = 456.789 + data = struct.pack(">f", test_value) + self.client.db_write(DB_READ_WRITE, OFFSET_FLOAT1, data) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_FLOAT1, 4) + self.assertAlmostEqual(test_value, struct.unpack(">f", result)[0], places=2) + + def test_db_write_byte(self) -> None: + """Test db_write() for Byte values.""" + test_value = 0xAB + self.client.db_write(DB_READ_WRITE, OFFSET_BYTE1, bytes([test_value])) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_BYTE1, 1) + self.assertEqual(test_value, result[0]) + + def test_db_write_word(self) -> None: + """Test db_write() for Word values.""" + test_value = 0x1234 + data = struct.pack(">H", test_value) + self.client.db_write(DB_READ_WRITE, OFFSET_WORD1, data) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_WORD1, 2) + self.assertEqual(test_value, struct.unpack(">H", result)[0]) + + def test_db_write_dword(self) -> None: + """Test db_write() for DWord values.""" + test_value = 0xDEADBEEF + data = struct.pack(">I", test_value) + self.client.db_write(DB_READ_WRITE, OFFSET_DWORD1, data) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_DWORD1, 4) + self.assertEqual(test_value, struct.unpack(">I", result)[0]) + + def test_db_write_dint(self) -> None: + """Test db_write() for DInt values.""" + test_value = -123456789 + data = struct.pack(">i", test_value) + self.client.db_write(DB_READ_WRITE, OFFSET_DINT1, data) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_DINT1, 4) + self.assertEqual(test_value, struct.unpack(">i", result)[0]) + + def test_db_write_char(self) -> None: + """Test db_write() for Char values.""" + test_value = "X" + self.client.db_write(DB_READ_WRITE, OFFSET_CHAR1, test_value.encode("ascii")) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_CHAR1, 1) + self.assertEqual(test_value, chr(result[0])) + + def test_db_write_bool(self) -> None: + """Test db_write() for Bool values (packed in byte).""" + # Read current byte, set bit 0 and bit 7, write back + data = bytearray(self.client.db_read(DB_READ_WRITE, OFFSET_BOOLS, 1)) + data[0] = data[0] | 0x01 | 0x80 # Set bit 0 and bit 7 + self.client.db_write(DB_READ_WRITE, OFFSET_BOOLS, bytes(data)) + + result = self.client.db_read(DB_READ_WRITE, OFFSET_BOOLS, 1) + self.assertTrue(bool(result[0] & 0x01)) + self.assertTrue(bool(result[0] & 0x80)) + + +@pytest.mark.e2e +class TestS7CommPlusMultiRead(unittest.TestCase): + """Tests for db_read_multi() - multiple reads in a single request.""" + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_multi_read(self) -> None: + """Test db_read_multi() reads multiple regions.""" + items = [ + (DB_READ_ONLY, OFFSET_INT1, 2), + (DB_READ_ONLY, OFFSET_FLOAT1, 4), + (DB_READ_ONLY, OFFSET_DWORD1, 4), + ] + results = self.client.db_read_multi(items) + self.assertEqual(3, len(results)) + + int_val = struct.unpack(">h", results[0])[0] + self.assertEqual(EXPECTED_INT1, int_val) + + float_val = struct.unpack(">f", results[1])[0] + self.assertAlmostEqual(EXPECTED_FLOAT1, float_val, places=2) + + dword_val = struct.unpack(">I", results[2])[0] + self.assertEqual(EXPECTED_DWORD1, dword_val) + + def test_multi_read_across_dbs(self) -> None: + """Test db_read_multi() across different data blocks.""" + # Write a known value to DB2 first + test_int = 777 + self.client.db_write(DB_READ_WRITE, OFFSET_INT1, struct.pack(">h", test_int)) + + items = [ + (DB_READ_ONLY, OFFSET_INT1, 2), + (DB_READ_WRITE, OFFSET_INT1, 2), + ] + results = self.client.db_read_multi(items) + self.assertEqual(2, len(results)) + + self.assertEqual(EXPECTED_INT1, struct.unpack(">h", results[0])[0]) + self.assertEqual(test_int, struct.unpack(">h", results[1])[0]) + + +@pytest.mark.e2e +class TestS7CommPlusExplore(unittest.TestCase): + """Tests for explore() - browsing the PLC object tree.""" + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_explore(self) -> None: + """Test explore() returns data.""" + try: + data = self.client.explore() + except Exception as e: + pytest.skip(f"Explore not supported: {e}") + self.assertIsInstance(data, bytes) + self.assertGreater(len(data), 0) diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index 356bd6f0..2f08f575 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -2,6 +2,8 @@ import struct import time +from collections.abc import Generator + import pytest import asyncio @@ -15,7 +17,7 @@ @pytest.fixture() -def server(): +def server() -> Generator[S7CommPlusServer, None, None]: """Create and start an S7CommPlus server with test data blocks.""" srv = S7CommPlusServer() @@ -294,7 +296,7 @@ async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: async def read_temp() -> float: data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] + return float(struct.unpack(">f", data)[0]) results = await asyncio.gather(read_temp(), read_temp(), read_temp()) assert len(results) == 3 From e48afb6ffec7d6eca00a50efab55e8bdecda7c1b Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Thu, 5 Mar 2026 20:06:59 +0200 Subject: [PATCH 07/27] Enhance S7CommPlus connection with variable-length TSAP support and async client improvements Support bytes-type remote TSAP (e.g. "SIMATIC-ROOT-HMI") in ISOTCPConnection, extend S7CommPlus protocol handling, and improve async client and server emulator. Co-Authored-By: Claude Opus 4.6 --- snap7/connection.py | 19 ++-- snap7/s7commplus/async_client.py | 98 ++++++++++++++--- snap7/s7commplus/client.py | 5 - snap7/s7commplus/connection.py | 176 +++++++++++++++++++++++++------ snap7/s7commplus/protocol.py | 22 ++++ snap7/s7commplus/server.py | 27 ++++- uv.lock | 127 ++++++++++------------ 7 files changed, 347 insertions(+), 127 deletions(-) diff --git a/snap7/connection.py b/snap7/connection.py index 6acee74f..8c8830e6 100644 --- a/snap7/connection.py +++ b/snap7/connection.py @@ -9,7 +9,7 @@ import struct import logging from enum import IntEnum -from typing import Optional, Type +from typing import Optional, Type, Union from types import TracebackType from .error import S7ConnectionError, S7TimeoutError @@ -66,7 +66,7 @@ def __init__( host: str, port: int = 102, local_tsap: int = 0x0100, - remote_tsap: int = 0x0102, + remote_tsap: Union[int, bytes] = 0x0102, tpdu_size: TPDUSize = TPDUSize.S_1024, ): """ @@ -76,7 +76,8 @@ def __init__( host: Target PLC IP address port: TCP port (default 102 for S7) local_tsap: Local Transport Service Access Point - remote_tsap: Remote Transport Service Access Point + remote_tsap: Remote Transport Service Access Point (int for 2-byte TSAP, + bytes for variable-length TSAP like b"SIMATIC-ROOT-HMI") tpdu_size: TPDU size to request during COTP negotiation """ self.host = host @@ -265,11 +266,13 @@ def _build_cotp_cr(self) -> bytes: ) # Add TSAP parameters - tsap_length = 2 # TSAP values are 2 bytes (unsigned short) - # Calling TSAP (local) - calling_tsap = struct.pack(">BBH", self.COTP_PARAM_CALLING_TSAP, tsap_length, self.local_tsap) - # Called TSAP (remote) - called_tsap = struct.pack(">BBH", self.COTP_PARAM_CALLED_TSAP, tsap_length, self.remote_tsap) + # Calling TSAP (local) - always 2 bytes + calling_tsap = struct.pack(">BBH", self.COTP_PARAM_CALLING_TSAP, 2, self.local_tsap) + # Called TSAP (remote) - can be 2-byte int or variable-length bytes (e.g. "SIMATIC-ROOT-HMI") + if isinstance(self.remote_tsap, bytes): + called_tsap = struct.pack(">BB", self.COTP_PARAM_CALLED_TSAP, len(self.remote_tsap)) + self.remote_tsap + else: + called_tsap = struct.pack(">BBH", self.COTP_PARAM_CALLED_TSAP, 2, self.remote_tsap) # PDU Size parameter (ISO 8073 code, e.g. 0x0A = 1024 bytes) pdu_size_param = struct.pack(">BBB", self.COTP_PARAM_PDU_SIZE, 1, self.tpdu_size) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index b3eb751d..fd53562b 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -17,8 +17,17 @@ import struct from typing import Any, Optional -from .protocol import FunctionCode, Opcode, ProtocolVersion -from .codec import encode_header, decode_header +from .protocol import ( + DataType, + ElementID, + FunctionCode, + ObjectId, + Opcode, + ProtocolVersion, + S7COMMPLUS_LOCAL_TSAP, + S7COMMPLUS_REMOTE_TSAP, +) +from .codec import encode_header, decode_header, encode_typed_value from .vlq import encode_uint32_vlq, decode_uint32_vlq logger = logging.getLogger(__name__) @@ -74,15 +83,15 @@ async def connect( rack: PLC rack number slot: PLC slot number """ - local_tsap = 0x0100 - remote_tsap = 0x0100 | (rack << 5) | slot - # TCP connect self._reader, self._writer = await asyncio.open_connection(host, port) try: - # COTP handshake - await self._cotp_connect(local_tsap, remote_tsap) + # COTP handshake with S7CommPlus TSAP values + await self._cotp_connect(S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP) + + # InitSSL handshake + await self._init_ssl() # S7CommPlus session setup await self._create_session() @@ -251,19 +260,20 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: ) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed:] + response = response_data[consumed : consumed + data_length] if len(response) < 14: raise RuntimeError("Response too short") return response[14:] - async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: + async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: """Perform COTP Connection Request / Confirm handshake.""" if self._writer is None or self._reader is None: raise RuntimeError("Not connected") @@ -271,7 +281,7 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: # Build COTP CR base_pdu = struct.pack(">BBHHB", 6, _COTP_CR, 0x0000, 0x0001, 0x00) calling_tsap = struct.pack(">BBH", 0xC1, 2, local_tsap) - called_tsap = struct.pack(">BBH", 0xC2, 2, remote_tsap) + called_tsap = struct.pack(">BB", 0xC2, len(remote_tsap)) + remote_tsap pdu_size_param = struct.pack(">BBB", 0xC0, 1, 0x0A) params = calling_tsap + called_tsap + pdu_size_param @@ -290,10 +300,40 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: if len(payload) < 7 or payload[1] != _COTP_CC: raise RuntimeError(f"Expected COTP CC, got {payload[1]:#04x}") + async def _init_ssl(self) -> None: + """Send InitSSL request (required before CreateObject).""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.INIT_SSL, + 0x0000, + seq_num, + 0x00000000, + 0x30, # Transport flags for InitSSL + ) + request += struct.pack(">I", 0) + + frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + await self._send_cotp_dt(frame) + + response_data = await self._recv_cotp_dt() + version, data_length, consumed = decode_header(response_data) + response = response_data[consumed : consumed + data_length] + + if len(response) < 14: + raise RuntimeError("InitSSL response too short") + + logger.debug(f"InitSSL response received, version=V{version}") + async def _create_session(self) -> None: """Send CreateObject to establish S7CommPlus session.""" seq_num = self._next_sequence_number() + # Build CreateObject request header request = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -301,17 +341,50 @@ async def _create_session(self) -> None: FunctionCode.CREATE_OBJECT, 0x0000, seq_num, - 0x00000000, + ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 0x36, ) + + # RequestId: ObjectServerSessionContainer (285) + request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) + + # RequestValue: ValueUDInt(0) + request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + + # Unknown padding + request += struct.pack(">I", 0) + + # RequestObject: NullServerSession PObject + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) + request += encode_uint32_vlq(0) # ClassFlags + request += encode_uint32_vlq(0) # AttributeId + + # Attribute: ServerSessionClientRID = 0x80c3c901 + request += bytes([ElementID.ATTRIBUTE]) + request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) + request += encode_typed_value(DataType.RID, 0x80C3C901) + + # Nested: ClassSubscriptions + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) + request += encode_uint32_vlq(0) + request += encode_uint32_vlq(0) + request += bytes([ElementID.TERMINATING_OBJECT]) + + request += bytes([ElementID.TERMINATING_OBJECT]) request += struct.pack(">I", 0) + # Frame header + trailer frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed:] + response = response_data[consumed : consumed + data_length] if len(response) < 14: raise RuntimeError("CreateObject response too short") @@ -336,6 +409,7 @@ async def _delete_session(self) -> None: request += struct.pack(">I", 0) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) try: diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index ad38c860..a54822f8 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -93,14 +93,9 @@ def connect( tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) """ - local_tsap = 0x0100 - remote_tsap = 0x0100 | (rack << 5) | slot - self._connection = S7CommPlusConnection( host=host, port=port, - local_tsap=local_tsap, - remote_tsap=remote_tsap, ) self._connection.connect( diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index c425810f..77fbaa88 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -15,19 +15,25 @@ Connection sequence (all versions):: 1. TCP connect to port 102 - 2. COTP Connection Request / Confirm (same as legacy S7comm) - 3. S7CommPlus CreateObject request (NullServer session setup) - 4. PLC responds with CreateObject response containing: + 2. COTP Connection Request / Confirm + - Local TSAP: 0x0600 + - Remote TSAP: "SIMATIC-ROOT-HMI" (16-byte ASCII string) + 3. InitSSL request / response (unencrypted) + 4. TLS activation (for V3/TLS PLCs) + 5. S7CommPlus CreateObject request (NullServer session setup) + - SessionId = ObjectNullServerSession (288) + - Proper PObject tree with ServerSession class + 6. PLC responds with CreateObject response containing: - Protocol version (V1/V2/V3) - Session ID - Server session challenge (V2/V3) -Version-specific authentication after step 4:: +Version-specific authentication after step 6:: - V1: Simple challenge-response handshake + V1: No further authentication needed V2: Session key derivation and integrity checking V3 (no TLS): Public-key key exchange - V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel + V3 (TLS): TLS 1.3 handshake is already done in step 4 Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ @@ -39,8 +45,18 @@ from types import TracebackType from ..connection import ISOTCPConnection -from .protocol import FunctionCode, Opcode, ProtocolVersion -from .codec import encode_header, decode_header +from .protocol import ( + FunctionCode, + Opcode, + ProtocolVersion, + ElementID, + ObjectId, + S7COMMPLUS_LOCAL_TSAP, + S7COMMPLUS_REMOTE_TSAP, +) +from .codec import encode_header, decode_header, encode_typed_value +from .vlq import encode_uint32_vlq +from .protocol import DataType logger = logging.getLogger(__name__) @@ -62,19 +78,15 @@ def __init__( self, host: str, port: int = 102, - local_tsap: int = 0x0100, - remote_tsap: int = 0x0102, ): self.host = host self.port = port - self.local_tsap = local_tsap - self.remote_tsap = remote_tsap self._iso_conn = ISOTCPConnection( host=host, port=port, - local_tsap=local_tsap, - remote_tsap=remote_tsap, + local_tsap=S7COMMPLUS_LOCAL_TSAP, + remote_tsap=S7COMMPLUS_REMOTE_TSAP, ) self._ssl_context: Optional[ssl.SSLContext] = None @@ -127,21 +139,31 @@ def connect( tls_ca: Path to CA certificate for PLC verification (PEM) """ try: - # Step 1: COTP connection + # Step 1: COTP connection (same TSAP for all S7CommPlus versions) self._iso_conn.connect(timeout) - # Step 2: CreateObject (S7CommPlus session setup) + # Step 2: InitSSL handshake (required before CreateObject) + self._init_ssl() + + # Step 3: TLS activation (required for modern firmware) + if use_tls: + # TODO: Perform TLS 1.3 handshake over the existing COTP connection + raise NotImplementedError("TLS activation is not yet implemented. Use use_tls=False for V1 connections.") + + # Step 4: CreateObject (S7CommPlus session setup) self._create_session() - # Step 3: Version-specific authentication - if use_tls and self._protocol_version >= ProtocolVersion.V3: - # TODO: Send InitSsl request and perform TLS handshake - raise NotImplementedError("TLS authentication is not yet implemented. Use use_tls=False for V1 connections.") + # Step 5: Version-specific authentication + if self._protocol_version >= ProtocolVersion.V3: + if not use_tls: + logger.warning( + "PLC reports V3 protocol but TLS is not enabled. Connection may not work without use_tls=True." + ) elif self._protocol_version == ProtocolVersion.V2: # TODO: Proprietary HMAC-SHA256/AES session auth raise NotImplementedError("V2 authentication is not yet implemented.") - # V1: No further authentication needed + # V1: No further authentication needed after CreateObject self._connected = True logger.info( f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" @@ -198,16 +220,17 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: + payload ) - # Add S7CommPlus frame header and send + # Add S7CommPlus frame header and trailer, then send frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() - # Parse frame header + # Parse frame header, use data_length to exclude trailer version, data_length, consumed = decode_header(response_frame) - response = response_frame[consumed:] + response = response_frame[consumed : consumed + data_length] if len(response) < 14: from ..error import S7ConnectionError @@ -216,11 +239,64 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: return response[14:] + def _init_ssl(self) -> None: + """Send InitSSL request to prepare the connection. + + This is the first S7CommPlus message sent after COTP connect. + The PLC responds with an InitSSL response. For PLCs that support + TLS, the caller should then activate TLS before sending CreateObject. + For V1 PLCs without TLS, the response may indicate that TLS is + not supported, but the connection can continue without it. + + Reference: thomas-v2/S7CommPlusDriver InitSslRequest + """ + seq_num = self._next_sequence_number() + + # InitSSL request: header + padding + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + FunctionCode.INIT_SSL, + 0x0000, # Reserved + seq_num, + 0x00000000, # No session yet + 0x30, # Transport flags (0x30 for InitSSL) + ) + # Trailing padding + request += struct.pack(">I", 0) + + # Wrap in S7CommPlus frame header + trailer + frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + + self._iso_conn.send_data(frame) + + # Receive InitSSL response + response_frame = self._iso_conn.receive_data() + + # Parse S7CommPlus frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + + raise S7ConnectionError("InitSSL response too short") + + logger.debug(f"InitSSL response received, version=V{version}") + def _create_session(self) -> None: - """Send CreateObject request to establish an S7CommPlus session.""" + """Send CreateObject request to establish an S7CommPlus session. + + Builds a NullServerSession CreateObject request matching the + structure expected by S7-1200/1500 PLCs: + + Reference: thomas-v2/S7CommPlusDriver CreateObjectRequest.SetNullServerSessionData() + """ seq_num = self._next_sequence_number() - # Build CreateObject request with NullServer session data + # Build CreateObject request header request = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -228,15 +304,54 @@ def _create_session(self) -> None: FunctionCode.CREATE_OBJECT, 0x0000, seq_num, - 0x00000000, # No session yet - 0x36, + ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 for initial setup + 0x36, # Transport flags ) - # Add empty request data (minimal CreateObject) + # RequestId: ObjectServerSessionContainer (285) + request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) + + # RequestValue: ValueUDInt(0) = DatatypeFlags(0x00) + Datatype.UDInt(0x04) + VLQ(0) + request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + + # Unknown padding (always 0) + request += struct.pack(">I", 0) + + # RequestObject: PObject for NullServerSession + # StartOfObject + request += bytes([ElementID.START_OF_OBJECT]) + # RelationId: GetNewRIDOnServer (211) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + # ClassId: ClassServerSession (287), VLQ encoded + request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) + # ClassFlags: 0 + request += encode_uint32_vlq(0) + # AttributeId: None (0) + request += encode_uint32_vlq(0) + + # Attribute: ServerSessionClientRID (300) = RID 0x80c3c901 + request += bytes([ElementID.ATTRIBUTE]) + request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) + request += encode_typed_value(DataType.RID, 0x80C3C901) + + # Nested object: ClassSubscriptions + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) + request += encode_uint32_vlq(0) # ClassFlags + request += encode_uint32_vlq(0) # AttributeId + request += bytes([ElementID.TERMINATING_OBJECT]) + + # End outer object + request += bytes([ElementID.TERMINATING_OBJECT]) + + # Trailing padding request += struct.pack(">I", 0) - # Wrap in S7CommPlus frame header + # Wrap in S7CommPlus frame header + trailer frame = encode_header(ProtocolVersion.V1, len(request)) + request + # S7CommPlus trailer (end-of-frame marker) + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) self._iso_conn.send_data(frame) @@ -275,6 +390,7 @@ def _delete_session(self) -> None: request += struct.pack(">I", 0) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) self._iso_conn.send_data(frame) # Best-effort receive diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 9ec4ec53..cf49df53 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -86,6 +86,28 @@ class ElementID(IntEnum): VARNAME_LIST = 0xAC +class ObjectId(IntEnum): + """Well-known object IDs used in session establishment. + + Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs + """ + + NONE = 0 + GET_NEW_RID_ON_SERVER = 211 + CLASS_SUBSCRIPTIONS = 255 + CLASS_SERVER_SESSION_CONTAINER = 284 + OBJECT_SERVER_SESSION_CONTAINER = 285 + CLASS_SERVER_SESSION = 287 + OBJECT_NULL_SERVER_SESSION = 288 + SERVER_SESSION_CLIENT_RID = 300 + + +# Default TSAP for S7CommPlus connections +# The remote TSAP is the ASCII string "SIMATIC-ROOT-HMI" (16 bytes) +S7COMMPLUS_LOCAL_TSAP = 0x0600 +S7COMMPLUS_REMOTE_TSAP = b"SIMATIC-ROOT-HMI" + + class DataType(IntEnum): """S7CommPlus wire data types. diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index f4b827aa..b40b587e 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -428,8 +428,9 @@ def _recv_s7commplus_frame(self, sock: socket.socket) -> Optional[bytes]: def _send_s7commplus_frame(self, sock: socket.socket, data: bytes) -> None: """Send an S7CommPlus frame wrapped in TPKT/COTP.""" - # S7CommPlus header (4 bytes) + data + # S7CommPlus header (4 bytes) + data + trailer (4 bytes) s7plus_frame = encode_header(self._protocol_version, len(data)) + data + s7plus_frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) # COTP DT header cotp_dt = struct.pack(">BBB", 2, 0xF0, 0x80) + s7plus_frame @@ -449,7 +450,8 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: except ValueError: return None - payload = data[consumed:] + # Use data_length to exclude any trailer + payload = data[consumed : consumed + data_length] if len(payload) < 14: return None @@ -463,7 +465,9 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: req_session_id = struct.unpack_from(">I", payload, 9)[0] request_data = payload[14:] - if function_code == FunctionCode.CREATE_OBJECT: + if function_code == FunctionCode.INIT_SSL: + return self._handle_init_ssl(seq_num) + elif function_code == FunctionCode.CREATE_OBJECT: return self._handle_create_object(seq_num, request_data) elif function_code == FunctionCode.DELETE_OBJECT: return self._handle_delete_object(seq_num, req_session_id) @@ -476,6 +480,23 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: else: return self._build_error_response(seq_num, req_session_id, function_code) + def _handle_init_ssl(self, seq_num: int) -> bytes: + """Handle InitSSL -- respond to SSL initialization (V1 emulation, no real TLS).""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.INIT_SSL, + 0x0000, + seq_num, + 0x00000000, + 0x00, # Transport flags + ) + response += encode_uint32_vlq(0) # Return code: success + response += struct.pack(">I", 0) + return bytes(response) + def _handle_create_object(self, seq_num: int, request_data: bytes) -> bytes: """Handle CreateObject -- establish a session.""" with self._lock: diff --git a/uv.lock b/uv.lock index e323d1c4..38c470c2 100644 --- a/uv.lock +++ b/uv.lock @@ -36,11 +36,11 @@ wheels = [ [[package]] name = "cachetools" -version = "7.0.4" +version = "7.0.1" source = { registry = "https://pypi.org/simple" } -sdist = { url = "https://files.pythonhosted.org/packages/a1/cc/eb3fd22f3b96b8b70ce456d0854ef08434e5ca79c02bf8db3fc07ccfca87/cachetools-7.0.4.tar.gz", hash = "sha256:7042c0e4eea87812f04744ce6ee9ed3de457875eb1f82d8a206c46d6e48b6734", size = 37379, upload-time = "2026-03-08T21:37:17.133Z" } +sdist = { url = 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"sha256:1bd755b504931164a5a496d217c014d098426cddc79363ad66ac78125f9d908f", size = 5825084, upload-time = "2026-03-09T17:24:35.378Z" }, + { url = "https://files.pythonhosted.org/packages/29/d1/3f62e4f9577b28c352c11623a03fb916096d5c131303d4861b4914481b6b/virtualenv-21.0.0-py3-none-any.whl", hash = "sha256:d44e70637402c7f4b10f48491c02a6397a3a187152a70cba0b6bc7642d69fb05", size = 5817167, upload-time = "2026-02-25T20:21:05.476Z" }, ] From 9fc990151b2ad2c9f6dfb6e2ad5b4f5ee1e64d29 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 6 Mar 2026 09:04:38 +0200 Subject: [PATCH 08/27] Add extensive debug logging to S7CommPlus protocol stack for real PLC diagnostics Adds hex dumps and detailed parsing at every protocol layer (ISO-TCP, S7CommPlus connection, client) plus 6 new diagnostic e2e tests that probe different payload formats and function codes against real hardware. Co-Authored-By: Claude Opus 4.6 --- snap7/connection.py | 3 +- snap7/s7commplus/client.py | 57 ++++++++- snap7/s7commplus/connection.py | 77 +++++++++--- tests/test_s7commplus_e2e.py | 210 +++++++++++++++++++++++++++++++++ 4 files changed, 325 insertions(+), 22 deletions(-) diff --git a/snap7/connection.py b/snap7/connection.py index 8c8830e6..466125ff 100644 --- a/snap7/connection.py +++ b/snap7/connection.py @@ -154,7 +154,7 @@ def send_data(self, data: bytes) -> None: # Send over TCP try: self.socket.sendall(tpkt_frame) - logger.debug(f"Sent {len(tpkt_frame)} bytes") + logger.debug(f"Sent {len(tpkt_frame)} bytes: {tpkt_frame.hex(' ')}") except socket.error as e: self.connected = False raise S7ConnectionError(f"Send failed: {e}") @@ -187,6 +187,7 @@ def receive_data(self) -> bytes: payload = self._recv_exact(remaining) # Parse COTP header and extract data + logger.debug(f"Received TPKT: version={version} length={length} payload ({len(payload)} bytes): {payload.hex(' ')}") return self._parse_cotp_data(payload) except socket.timeout: diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index a54822f8..2b0d2b0d 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -135,32 +135,53 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) + logger.debug( + f"db_read: db={db_number} start={start} size={size} " + f"object_id=0x{object_id:08X} payload={bytes(payload).hex(' ')}" + ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_read: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response offset = 0 # Skip return code - _, consumed = decode_uint32_vlq(response, offset) + return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: return_code={return_code} (consumed {consumed} bytes)") offset += consumed # Item count item_count, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: item_count={item_count} (consumed {consumed} bytes)") offset += consumed if item_count == 0: + logger.debug("db_read: no items returned") return b"" # First item: status + data_length + data status, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: item status={status} (consumed {consumed} bytes)") offset += consumed data_length, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: data_length={data_length} (consumed {consumed} bytes)") offset += consumed if status != 0: + logger.error( + f"db_read: FAILED status={status}, remaining bytes: {response[offset:].hex(' ')}" + ) raise RuntimeError(f"Read failed with status {status}") - return response[offset : offset + data_length] + result = response[offset : offset + data_length] + logger.debug(f"db_read: result ({len(result)} bytes): {result.hex(' ')}") + remaining = response[offset + data_length :] + if remaining: + logger.debug(f"db_read: remaining after data ({len(remaining)} bytes): {remaining.hex(' ')}") + + return result def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -181,14 +202,25 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data + logger.debug( + f"db_write: db={db_number} start={start} data_len={len(data)} " + f"object_id=0x{object_id:08X} data={data.hex(' ')} payload={bytes(payload).hex(' ')}" + ) + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_write: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response - check return code offset = 0 return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_write: return_code={return_code} (consumed {consumed} bytes)") offset += consumed if return_code != 0: + logger.error( + f"db_write: FAILED return_code={return_code}, remaining: {response[offset:].hex(' ')}" + ) raise RuntimeError(f"Write failed with return code {return_code}") def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: @@ -211,28 +243,39 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) + logger.debug(f"db_read_multi: {len(items)} items: {items} payload={bytes(payload).hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response offset = 0 - _, consumed = decode_uint32_vlq(response, offset) + return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read_multi: return_code={return_code} (consumed {consumed} bytes)") offset += consumed item_count, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read_multi: item_count={item_count} (consumed {consumed} bytes)") offset += consumed results: list[bytes] = [] - for _ in range(item_count): + for i in range(item_count): status, consumed = decode_uint32_vlq(response, offset) offset += consumed data_length, consumed = decode_uint32_vlq(response, offset) offset += consumed + logger.debug(f"db_read_multi: item[{i}] status={status} data_length={data_length}") + if status == 0 and data_length > 0: - results.append(response[offset : offset + data_length]) + item_data = response[offset : offset + data_length] + logger.debug(f"db_read_multi: item[{i}] data: {item_data.hex(' ')}") + results.append(item_data) offset += data_length else: + logger.debug(f"db_read_multi: item[{i}] empty/error") results.append(b"") return results @@ -251,7 +294,9 @@ def explore(self) -> bytes: if self._connection is None: raise RuntimeError("Not connected") - return self._connection.send_request(FunctionCode.EXPLORE, b"") + response = self._connection.send_request(FunctionCode.EXPLORE, b"") + logger.debug(f"explore: response ({len(response)} bytes): {response.hex(' ')}") + return response # -- Context manager -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 77fbaa88..e3ba388a 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -206,38 +206,67 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: seq_num = self._next_sequence_number() # Build request header - request = ( - struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - function_code, - 0x0000, # Reserved - seq_num, - self._session_id, - 0x36, # Transport flags - ) - + payload + request_header = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + request = request_header + payload + + logger.debug( + f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}" ) + logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") + logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") # Add S7CommPlus frame header and trailer, then send frame = encode_header(self._protocol_version, len(request)) + request frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) + + logger.debug(f" Full frame ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== RECV RESPONSE === raw frame ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse frame header, use data_length to exclude trailer version, data_length, consumed = decode_header(response_frame) + logger.debug(f" Frame header: version=V{version}, data_length={data_length}, header_size={consumed}") + response = response_frame[consumed : consumed + data_length] + logger.debug(f" Response data ({len(response)} bytes): {response.hex(' ')}") if len(response) < 14: from ..error import S7ConnectionError raise S7ConnectionError("Response too short") - return response[14:] + # Parse response header for debug + resp_opcode = response[0] + resp_func = struct.unpack_from(">H", response, 3)[0] + resp_seq = struct.unpack_from(">H", response, 7)[0] + resp_session = struct.unpack_from(">I", response, 9)[0] + resp_transport = response[13] + logger.debug( + f" Response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " + f"seq={resp_seq} session=0x{resp_session:08X} transport=0x{resp_transport:02X}" + ) + + resp_payload = response[14:] + logger.debug(f" Response payload ({len(resp_payload)} bytes): {resp_payload.hex(' ')}") + + # Check for trailer bytes after data_length + trailer = response_frame[consumed + data_length :] + if trailer: + logger.debug(f" Trailer ({len(trailer)} bytes): {trailer.hex(' ')}") + + return resp_payload def _init_ssl(self) -> None: """Send InitSSL request to prepare the connection. @@ -270,10 +299,12 @@ def _init_ssl(self) -> None: frame = encode_header(ProtocolVersion.V1, len(request)) + request frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + logger.debug(f"=== InitSSL === sending ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive InitSSL response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== InitSSL === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse S7CommPlus frame header version, data_length, consumed = decode_header(response_frame) @@ -284,7 +315,8 @@ def _init_ssl(self) -> None: raise S7ConnectionError("InitSSL response too short") - logger.debug(f"InitSSL response received, version=V{version}") + logger.debug(f"InitSSL response: version=V{version}, data_length={data_length}") + logger.debug(f"InitSSL response body ({len(response)} bytes): {response.hex(' ')}") def _create_session(self) -> None: """Send CreateObject request to establish an S7CommPlus session. @@ -353,15 +385,20 @@ def _create_session(self) -> None: # S7CommPlus trailer (end-of-frame marker) frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + logger.debug(f"=== CreateObject === sending ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== CreateObject === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse S7CommPlus frame header version, data_length, consumed = decode_header(response_frame) response = response_frame[consumed:] + logger.debug(f"CreateObject response: version=V{version}, data_length={data_length}") + logger.debug(f"CreateObject response body ({len(response)} bytes): {response.hex(' ')}") + if len(response) < 14: from ..error import S7ConnectionError @@ -371,7 +408,17 @@ def _create_session(self) -> None: self._session_id = struct.unpack_from(">I", response, 9)[0] self._protocol_version = version - logger.debug(f"Session created: id={self._session_id}, version=V{version}") + # Parse and log the full response header + resp_opcode = response[0] + resp_func = struct.unpack_from(">H", response, 3)[0] + resp_seq = struct.unpack_from(">H", response, 7)[0] + resp_transport = response[13] + logger.debug( + f"CreateObject response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " + f"seq={resp_seq} session=0x{self._session_id:08X} transport=0x{resp_transport:02X}" + ) + logger.debug(f"CreateObject response payload: {response[14:].hex(' ')}") + logger.debug(f"Session created: id=0x{self._session_id:08X} ({self._session_id}), version=V{version}") def _delete_session(self) -> None: """Send DeleteObject to close the session.""" diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py index 0ae37ea6..46da4b05 100644 --- a/tests/test_s7commplus_e2e.py +++ b/tests/test_s7commplus_e2e.py @@ -40,6 +40,7 @@ TIA Portal so that byte offsets match the layout above. """ +import logging import os import struct import unittest @@ -48,6 +49,14 @@ from snap7.s7commplus.client import S7CommPlusClient +# Enable DEBUG logging for all s7commplus modules so we get full hex dumps +logging.basicConfig( + level=logging.DEBUG, + format="%(asctime)s %(name)s %(levelname)s %(message)s", +) +for _mod in ["snap7.s7commplus.client", "snap7.s7commplus.connection", "snap7.connection"]: + logging.getLogger(_mod).setLevel(logging.DEBUG) + # ============================================================================= # PLC Connection Configuration # These can be overridden via pytest command line options or environment variables @@ -408,3 +417,204 @@ def test_explore(self) -> None: pytest.skip(f"Explore not supported: {e}") self.assertIsInstance(data, bytes) self.assertGreater(len(data), 0) + + +@pytest.mark.e2e +class TestS7CommPlusDiagnostics(unittest.TestCase): + """Diagnostic tests for debugging protocol issues against real PLCs. + + These tests are designed to dump raw protocol data at every layer + to help diagnose why db_read/db_write fail against real hardware. + """ + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_diag_connection_info(self) -> None: + """Dump connection state after successful connect.""" + print(f"\n{'='*60}") + print(f"DIAGNOSTIC: Connection Info") + print(f" connected: {self.client.connected}") + print(f" protocol_version: V{self.client.protocol_version}") + print(f" session_id: 0x{self.client.session_id:08X} ({self.client.session_id})") + print(f"{'='*60}") + self.assertTrue(self.client.connected) + + def test_diag_explore_raw(self) -> None: + """Explore and dump the raw response for analysis.""" + print(f"\n{'='*60}") + print("DIAGNOSTIC: Explore raw response") + try: + data = self.client.explore() + print(f" Length: {len(data)} bytes") + # Dump in 32-byte rows + for i in range(0, len(data), 32): + chunk = data[i : i + 32] + hex_str = chunk.hex(" ") + ascii_str = "".join(chr(b) if 32 <= b < 127 else "." for b in chunk) + print(f" {i:04x}: {hex_str:<96s} {ascii_str}") + except Exception as e: + print(f" Explore failed: {e}") + print(f"{'='*60}") + + def test_diag_db_read_single_byte(self) -> None: + """Try to read a single byte from DB1 offset 0 and dump everything.""" + print(f"\n{'='*60}") + print("DIAGNOSTIC: db_read(DB1, offset=0, size=1)") + try: + data = self.client.db_read(DB_READ_ONLY, 0, 1) + print(f" Success! Got {len(data)} bytes: {data.hex(' ')}") + except Exception as e: + print(f" FAILED: {type(e).__name__}: {e}") + print(f"{'='*60}") + + def test_diag_db_read_full_block(self) -> None: + """Try to read the full test DB and dump everything.""" + print(f"\n{'='*60}") + print(f"DIAGNOSTIC: db_read(DB{DB_READ_ONLY}, offset=0, size={DB_SIZE})") + try: + data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) + print(f" Success! Got {len(data)} bytes:") + for i in range(0, len(data), 16): + chunk = data[i : i + 16] + print(f" {i:04x}: {chunk.hex(' ')}") + except Exception as e: + print(f" FAILED: {type(e).__name__}: {e}") + print(f"{'='*60}") + + def test_diag_raw_get_multi_variables(self) -> None: + """Send a raw GetMultiVariables with different payload formats and dump responses. + + This tries several payload encodings to see which ones the PLC accepts. + """ + from snap7.s7commplus.protocol import FunctionCode + from snap7.s7commplus.vlq import encode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Raw GetMultiVariables payload experiments") + + assert self.client._connection is not None + + # Experiment 1: Our current format (item_count + object_id + offset + size) + payloads = { + "current_format (count=1, obj=0x00010001, off=0, sz=2)": ( + encode_uint32_vlq(1) + + encode_uint32_vlq(0x00010001) + + encode_uint32_vlq(0) + + encode_uint32_vlq(2) + ), + "empty_payload": b"", + "just_zero": encode_uint32_vlq(0), + "single_vlq_1": encode_uint32_vlq(1), + } + + for label, payload in payloads.items(): + print(f"\n --- {label} ---") + print(f" Payload ({len(payload)} bytes): {payload.hex(' ')}") + try: + response = self.client._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, payload + ) + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + + # Try to parse return code + if len(response) > 0: + from snap7.s7commplus.vlq import decode_uint32_vlq + + rc, consumed = decode_uint32_vlq(response, 0) + print(f" Return code (VLQ): {rc} (0x{rc:X})") + remaining = response[consumed:] + if remaining: + print(f" After return code ({len(remaining)} bytes): {remaining.hex(' ')}") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") + + def test_diag_raw_set_variable(self) -> None: + """Try SetVariable (0x04F2) instead of SetMultiVariables to see if PLC responds differently.""" + from snap7.s7commplus.protocol import FunctionCode + from snap7.s7commplus.vlq import encode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Raw SetVariable / GetVariable experiments") + + assert self.client._connection is not None + + function_codes = { + "GET_VARIABLE (0x04FC)": FunctionCode.GET_VARIABLE, + "GET_MULTI_VARIABLES (0x054C)": FunctionCode.GET_MULTI_VARIABLES, + "SET_VARIABLE (0x04F2)": FunctionCode.SET_VARIABLE, + } + + # Simple payload: just try empty or minimal + for label, fc in function_codes.items(): + print(f"\n --- {label} with empty payload ---") + try: + response = self.client._connection.send_request(fc, b"") + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") + + def test_diag_explore_then_read(self) -> None: + """Explore first to discover object IDs, then try reading using those IDs.""" + from snap7.s7commplus.protocol import FunctionCode, ElementID + from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Explore -> extract object IDs -> try reading") + + assert self.client._connection is not None + + try: + explore_data = self.client._connection.send_request(FunctionCode.EXPLORE, b"") + print(f" Explore response ({len(explore_data)} bytes)") + + # Scan for StartOfObject markers and extract relation IDs + object_ids = [] + i = 0 + while i < len(explore_data): + if explore_data[i] == ElementID.START_OF_OBJECT: + if i + 5 <= len(explore_data): + rel_id = struct.unpack_from(">I", explore_data, i + 1)[0] + object_ids.append(rel_id) + print(f" Found object at offset {i}: relation_id=0x{rel_id:08X}") + i += 5 + else: + i += 1 + + # Try reading using each discovered object ID + for obj_id in object_ids[:5]: # Limit to first 5 + print(f"\n --- Read using object_id=0x{obj_id:08X} ---") + payload = ( + encode_uint32_vlq(1) + + encode_uint32_vlq(obj_id) + + encode_uint32_vlq(0) + + encode_uint32_vlq(4) + ) + try: + response = self.client._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, payload + ) + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + if len(response) > 0: + rc, consumed = decode_uint32_vlq(response, 0) + print(f" Return code: {rc} (0x{rc:X})") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + except Exception as e: + print(f" Explore failed: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") From 9a6ffcf451bcdce7a1ac30469033c899f7e0c376 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 6 Mar 2026 10:14:47 +0200 Subject: [PATCH 09/27] Fix S7CommPlus wire format for real PLC compatibility Rewrite client payload encoding/decoding to use the correct S7CommPlus protocol format with ItemAddress structures (SymbolCrc, AccessArea, AccessSubArea, LIDs), ObjectQualifier, and proper PValue response parsing. Previously the client used a simplified custom format that only worked with the emulated server, causing ERROR2 responses from real S7-1200/1500 PLCs. - client.py: Correct GetMultiVariables/SetMultiVariables request format - async_client.py: Reuse corrected payload builders from client.py - codec.py: Add ItemAddress, ObjectQualifier, PValue encode/decode - protocol.py: Add Ids constants (DB_ACCESS_AREA_BASE, etc.) - server.py: Update to parse/generate the corrected wire format Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 88 ++------ snap7/s7commplus/client.py | 331 ++++++++++++++++++++----------- snap7/s7commplus/codec.py | 205 ++++++++++++++++++- snap7/s7commplus/protocol.py | 27 +++ snap7/s7commplus/server.py | 285 +++++++++++++++++++------- 5 files changed, 680 insertions(+), 256 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index fd53562b..41780192 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -28,7 +28,8 @@ S7COMMPLUS_REMOTE_TSAP, ) from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .vlq import encode_uint32_vlq +from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response logger = logging.getLogger(__name__) @@ -137,33 +138,15 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) + payload = _build_read_payload([(db_number, start, size)]) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - _, consumed = decode_uint32_vlq(response, offset) - offset += consumed - item_count, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - if item_count == 0: - return b"" - - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - if status != 0: - raise RuntimeError(f"Read failed with status {status}") - - return response[offset : offset + data_length] + results = _parse_read_response(response) + if not results: + raise RuntimeError("Read returned no data") + if results[0] is None: + raise RuntimeError("Read failed: PLC returned error for item") + return results[0] async def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -173,20 +156,9 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: start: Start byte offset data: Bytes to write """ - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(len(data)) - payload += data - - response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - if return_code != 0: - raise RuntimeError(f"Write failed with return code {return_code}") + payload = _build_write_payload([(db_number, start, data)]) + response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, payload) + _parse_write_response(response) async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. @@ -197,35 +169,11 @@ async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: Returns: List of raw bytes for each item """ - payload = bytearray() - payload += encode_uint32_vlq(len(items)) - for db_number, start, size in items: - object_id = 0x00010000 | (db_number & 0xFFFF) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - _, consumed = decode_uint32_vlq(response, offset) - offset += consumed - item_count, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - results: list[bytes] = [] - for _ in range(item_count): - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - if status == 0 and data_length > 0: - results.append(response[offset : offset + data_length]) - offset += data_length - else: - results.append(b"") - - return results + payload = _build_read_payload(items) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + + results = _parse_read_response(response) + return [r if r is not None else b"" for r in results] async def explore(self) -> bytes: """Browse the PLC object tree. diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 2b0d2b0d..e5ddabd4 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -15,11 +15,18 @@ """ import logging +import struct from typing import Any, Optional from .connection import S7CommPlusConnection -from .protocol import FunctionCode -from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .protocol import FunctionCode, Ids +from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq +from .codec import ( + encode_item_address, + encode_object_qualifier, + encode_pvalue_blob, + decode_pvalue_to_bytes, +) logger = logging.getLogger(__name__) @@ -127,61 +134,18 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: if self._connection is None: raise RuntimeError("Not connected") - # Build GetMultiVariables request payload - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) # 1 item - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - logger.debug( - f"db_read: db={db_number} start={start} size={size} " - f"object_id=0x{object_id:08X} payload={bytes(payload).hex(' ')}" - ) - - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + payload = _build_read_payload([(db_number, start, size)]) + logger.debug(f"db_read: db={db_number} start={start} size={size} payload={payload.hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - offset = 0 - # Skip return code - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - # Item count - item_count, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: item_count={item_count} (consumed {consumed} bytes)") - offset += consumed - - if item_count == 0: - logger.debug("db_read: no items returned") - return b"" - - # First item: status + data_length + data - status, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: item status={status} (consumed {consumed} bytes)") - offset += consumed - - data_length, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: data_length={data_length} (consumed {consumed} bytes)") - offset += consumed - - if status != 0: - logger.error( - f"db_read: FAILED status={status}, remaining bytes: {response[offset:].hex(' ')}" - ) - raise RuntimeError(f"Read failed with status {status}") - - result = response[offset : offset + data_length] - logger.debug(f"db_read: result ({len(result)} bytes): {result.hex(' ')}") - remaining = response[offset + data_length :] - if remaining: - logger.debug(f"db_read: remaining after data ({len(remaining)} bytes): {remaining.hex(' ')}") - - return result + results = _parse_read_response(response) + if not results: + raise RuntimeError("Read returned no data") + if results[0] is None: + raise RuntimeError("Read failed: PLC returned error for item") + return results[0] def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -194,34 +158,16 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: if self._connection is None: raise RuntimeError("Not connected") - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) # 1 item - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(len(data)) - payload += data - + payload = _build_write_payload([(db_number, start, data)]) logger.debug( f"db_write: db={db_number} start={start} data_len={len(data)} " - f"object_id=0x{object_id:08X} data={data.hex(' ')} payload={bytes(payload).hex(' ')}" + f"data={data.hex(' ')} payload={payload.hex(' ')}" ) - response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) - + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, payload) logger.debug(f"db_write: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - check return code - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_write: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - if return_code != 0: - logger.error( - f"db_write: FAILED return_code={return_code}, remaining: {response[offset:].hex(' ')}" - ) - raise RuntimeError(f"Write failed with return code {return_code}") + _parse_write_response(response) def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. @@ -235,50 +181,14 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: if self._connection is None: raise RuntimeError("Not connected") - payload = bytearray() - payload += encode_uint32_vlq(len(items)) - for db_number, start, size in items: - object_id = 0x00010000 | (db_number & 0xFFFF) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - logger.debug(f"db_read_multi: {len(items)} items: {items} payload={bytes(payload).hex(' ')}") - - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + payload = _build_read_payload(items) + logger.debug(f"db_read_multi: {len(items)} items: {items} payload={payload.hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read_multi: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - item_count, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read_multi: item_count={item_count} (consumed {consumed} bytes)") - offset += consumed - - results: list[bytes] = [] - for i in range(item_count): - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - logger.debug(f"db_read_multi: item[{i}] status={status} data_length={data_length}") - - if status == 0 and data_length > 0: - item_data = response[offset : offset + data_length] - logger.debug(f"db_read_multi: item[{i}] data: {item_data.hex(' ')}") - results.append(item_data) - offset += data_length - else: - logger.debug(f"db_read_multi: item[{i}] empty/error") - results.append(b"") - - return results + results = _parse_read_response(response) + return [r if r is not None else b"" for r in results] # -- Explore (browse PLC object tree) -- @@ -305,3 +215,190 @@ def __enter__(self) -> "S7CommPlusClient": def __exit__(self, *args: Any) -> None: self.disconnect() + + +# -- Request/response builders (module-level for reuse by async client) -- + + +def _build_read_payload(items: list[tuple[int, int, int]]) -> bytes: + """Build a GetMultiVariables request payload. + + Args: + items: List of (db_number, start_offset, size) tuples + + Returns: + Encoded payload bytes (after the 14-byte request header) + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs + """ + # Encode all item addresses and compute total field count + addresses: list[bytes] = [] + total_field_count = 0 + for db_number, start, size in items: + access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) + addr_bytes, field_count = encode_item_address( + access_area=access_area, + access_sub_area=Ids.DB_VALUE_ACTUAL, + lids=[start, size], + ) + addresses.append(addr_bytes) + total_field_count += field_count + + payload = bytearray() + # LinkId (UInt32 fixed = 0, for reading variables) + payload += struct.pack(">I", 0) + # Item count + payload += encode_uint32_vlq(len(items)) + # Total field count across all items + payload += encode_uint32_vlq(total_field_count) + # Item addresses + for addr in addresses: + payload += addr + # ObjectQualifier + payload += encode_object_qualifier() + # Padding + payload += struct.pack(">I", 0) + + return bytes(payload) + + +def _parse_read_response(response: bytes) -> list[Optional[bytes]]: + """Parse a GetMultiVariables response payload. + + Args: + response: Response payload (after the 14-byte response header) + + Returns: + List of raw bytes per item (None for errored items) + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesResponse.cs + """ + offset = 0 + + # ReturnValue (UInt64 VLQ) + return_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + logger.debug(f"_parse_read_response: return_value={return_value}") + + if return_value != 0: + logger.error(f"_parse_read_response: PLC returned error: {return_value}") + return [] + + # Value list: ItemNumber (VLQ) + PValue, terminated by ItemNumber=0 + values: dict[int, bytes] = {} + while offset < len(response): + item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if item_nr == 0: + break + raw_bytes, consumed = decode_pvalue_to_bytes(response, offset) + offset += consumed + values[item_nr] = raw_bytes + + # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ), terminated by 0 + errors: dict[int, int] = {} + while offset < len(response): + err_item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if err_item_nr == 0: + break + err_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + errors[err_item_nr] = err_value + logger.debug(f"_parse_read_response: error item {err_item_nr}: {err_value}") + + # Build result list (1-based item numbers) + max_item = max(max(values.keys(), default=0), max(errors.keys(), default=0)) + results: list[Optional[bytes]] = [] + for i in range(1, max_item + 1): + if i in values: + results.append(values[i]) + else: + results.append(None) + + return results + + +def _build_write_payload(items: list[tuple[int, int, bytes]]) -> bytes: + """Build a SetMultiVariables request payload. + + Args: + items: List of (db_number, start_offset, data) tuples + + Returns: + Encoded payload bytes + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs + """ + # Encode all item addresses and compute total field count + addresses: list[bytes] = [] + total_field_count = 0 + for db_number, start, data in items: + access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) + addr_bytes, field_count = encode_item_address( + access_area=access_area, + access_sub_area=Ids.DB_VALUE_ACTUAL, + lids=[start, len(data)], + ) + addresses.append(addr_bytes) + total_field_count += field_count + + payload = bytearray() + # InObjectId (UInt32 fixed = 0, for plain variable writes) + payload += struct.pack(">I", 0) + # Item count + payload += encode_uint32_vlq(len(items)) + # Total field count + payload += encode_uint32_vlq(total_field_count) + # Item addresses + for addr in addresses: + payload += addr + # Value list: ItemNumber (1-based) + PValue + for i, (_, _, data) in enumerate(items, 1): + payload += encode_uint32_vlq(i) + payload += encode_pvalue_blob(data) + # Fill byte + payload += bytes([0x00]) + # ObjectQualifier + payload += encode_object_qualifier() + # Padding + payload += struct.pack(">I", 0) + + return bytes(payload) + + +def _parse_write_response(response: bytes) -> None: + """Parse a SetMultiVariables response payload. + + Args: + response: Response payload (after the 14-byte response header) + + Raises: + RuntimeError: If the write failed + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesResponse.cs + """ + offset = 0 + + # ReturnValue (UInt64 VLQ) + return_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + logger.debug(f"_parse_write_response: return_value={return_value}") + + if return_value != 0: + raise RuntimeError(f"Write failed with return value {return_value}") + + # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ) + errors: list[tuple[int, int]] = [] + while offset < len(response): + err_item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if err_item_nr == 0: + break + err_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + errors.append((err_item_nr, err_value)) + + if errors: + err_str = ", ".join(f"item {nr}: error {val}" for nr, val in errors) + raise RuntimeError(f"Write failed: {err_str}") diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py index 79a7ec36..74f94a2e 100644 --- a/snap7/s7commplus/codec.py +++ b/snap7/s7commplus/codec.py @@ -15,11 +15,13 @@ import struct from typing import Any -from .protocol import PROTOCOL_ID, DataType +from .protocol import PROTOCOL_ID, DataType, Ids from .vlq import ( encode_uint32_vlq, + decode_uint32_vlq, encode_int32_vlq, encode_uint64_vlq, + decode_uint64_vlq, encode_int64_vlq, ) @@ -290,3 +292,204 @@ def encode_typed_value(datatype: int, value: Any) -> bytes: return bytes(tag + encode_uint32_vlq(len(value)) + value) else: raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") + + +# -- S7CommPlus request/response payload helpers -- + + +def encode_object_qualifier() -> bytes: + """Encode the S7CommPlus ObjectQualifier structure. + + This fixed structure is appended to GetMultiVariables and + SetMultiVariables requests. + + Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs EncodeObjectQualifier + """ + result = bytearray() + result += struct.pack(">I", Ids.OBJECT_QUALIFIER) + # ParentRID = RID(0) + result += encode_uint32_vlq(Ids.PARENT_RID) + result += bytes([0x00, DataType.RID]) + struct.pack(">I", 0) + # CompositionAID = AID(0) + result += encode_uint32_vlq(Ids.COMPOSITION_AID) + result += bytes([0x00, DataType.AID]) + encode_uint32_vlq(0) + # KeyQualifier = UDInt(0) + result += encode_uint32_vlq(Ids.KEY_QUALIFIER) + result += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + # Terminator + result += bytes([0x00]) + return bytes(result) + + +def encode_item_address( + access_area: int, + access_sub_area: int, + lids: list[int] | None = None, + symbol_crc: int = 0, +) -> tuple[bytes, int]: + """Encode an S7CommPlus ItemAddress for variable access. + + Args: + access_area: Access area ID (e.g., 0x8A0E0001 for DB1) + access_sub_area: Sub-area ID (e.g., Ids.DB_VALUE_ACTUAL) + lids: Additional LID values for sub-addressing + symbol_crc: Symbol CRC (0 for no CRC check) + + Returns: + Tuple of (encoded_bytes, field_count) + + Reference: thomas-v2/S7CommPlusDriver/ClientApi/ItemAddress.cs + """ + if lids is None: + lids = [] + result = bytearray() + result += encode_uint32_vlq(symbol_crc) + result += encode_uint32_vlq(access_area) + result += encode_uint32_vlq(len(lids) + 1) # +1 for AccessSubArea + result += encode_uint32_vlq(access_sub_area) + for lid in lids: + result += encode_uint32_vlq(lid) + field_count = 4 + len(lids) # SymbolCrc + AccessArea + NumLIDs + AccessSubArea + LIDs + return bytes(result), field_count + + +def encode_pvalue_blob(data: bytes) -> bytes: + """Encode raw bytes as a BLOB PValue. + + PValue format: [flags:1][datatype:1][length:VLQ][data] + """ + result = bytearray() + result += bytes([0x00, DataType.BLOB]) + result += encode_uint32_vlq(len(data)) + result += data + return bytes(result) + + +def decode_pvalue_to_bytes(data: bytes, offset: int) -> tuple[bytes, int]: + """Decode a PValue from S7CommPlus response to raw bytes. + + Supports scalar types and BLOBs. Returns the raw big-endian bytes + of the value regardless of type. + + Args: + data: Response buffer + offset: Position of the PValue + + Returns: + Tuple of (raw_bytes, bytes_consumed) + """ + if offset + 2 > len(data): + raise ValueError("Not enough data for PValue header") + + flags = data[offset] + datatype = data[offset + 1] + consumed = 2 + + is_array = bool(flags & 0x10) + + if is_array: + # Array: read count then elements + count, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + elem_size = _pvalue_element_size(datatype) + if elem_size > 0: + raw = data[offset + consumed : offset + consumed + count * elem_size] + consumed += count * elem_size + return bytes(raw), consumed + else: + # Variable-length elements (VLQ encoded) + result = bytearray() + for _ in range(count): + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + result += encode_uint32_vlq(val) + return bytes(result), consumed + + # Scalar types + if datatype == DataType.NULL: + return b"", consumed + elif datatype == DataType.BOOL: + return data[offset + consumed : offset + consumed + 1], consumed + 1 + elif datatype in (DataType.USINT, DataType.BYTE, DataType.SINT): + return data[offset + consumed : offset + consumed + 1], consumed + 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return data[offset + consumed : offset + consumed + 2], consumed + 2 + elif datatype in (DataType.UDINT, DataType.DWORD): + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">I", val), consumed + elif datatype in (DataType.DINT,): + # Signed VLQ + from .vlq import decode_int32_vlq + + val, c = decode_int32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">i", val), consumed + elif datatype == DataType.REAL: + return data[offset + consumed : offset + consumed + 4], consumed + 4 + elif datatype == DataType.LREAL: + return data[offset + consumed : offset + consumed + 8], consumed + 8 + elif datatype in (DataType.ULINT, DataType.LWORD): + val, c = decode_uint64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">Q", val), consumed + elif datatype in (DataType.LINT,): + from .vlq import decode_int64_vlq + + val, c = decode_int64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">q", val), consumed + elif datatype == DataType.TIMESTAMP: + return data[offset + consumed : offset + consumed + 8], consumed + 8 + elif datatype == DataType.TIMESPAN: + from .vlq import decode_int64_vlq + + val, c = decode_int64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">q", val), consumed + elif datatype == DataType.RID: + return data[offset + consumed : offset + consumed + 4], consumed + 4 + elif datatype == DataType.AID: + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">I", val), consumed + elif datatype == DataType.BLOB: + length, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + raw = data[offset + consumed : offset + consumed + length] + consumed += length + return bytes(raw), consumed + elif datatype == DataType.WSTRING: + length, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + raw = data[offset + consumed : offset + consumed + length] + consumed += length + return bytes(raw), consumed + elif datatype == DataType.STRUCT: + # Struct: read count, then nested PValues + count, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + result = bytearray() + for _ in range(count): + val_bytes, c = decode_pvalue_to_bytes(data, offset + consumed) + consumed += c + result += val_bytes + return bytes(result), consumed + else: + raise ValueError(f"Unsupported PValue datatype: {datatype:#04x}") + + +def _pvalue_element_size(datatype: int) -> int: + """Return the fixed byte size for a PValue array element, or 0 for variable-length.""" + if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return 2 + elif datatype in (DataType.REAL,): + return 4 + elif datatype in (DataType.LREAL, DataType.TIMESTAMP): + return 8 + elif datatype in (DataType.RID,): + return 4 + else: + return 0 # Variable-length (VLQ encoded) diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index cf49df53..71587639 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -143,6 +143,33 @@ class DataType(IntEnum): S7STRING = 0x19 +class Ids(IntEnum): + """Well-known IDs for S7CommPlus protocol structures. + + Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs + """ + + # Data block access sub-areas + DB_VALUE_ACTUAL = 2550 + CONTROLLER_AREA_VALUE_ACTUAL = 2551 + + # ObjectQualifier structure IDs + OBJECT_QUALIFIER = 1256 + PARENT_RID = 1257 + COMPOSITION_AID = 1258 + KEY_QUALIFIER = 1259 + + # Native object RIDs for memory areas + NATIVE_THE_I_AREA_RID = 80 + NATIVE_THE_Q_AREA_RID = 81 + NATIVE_THE_M_AREA_RID = 82 + NATIVE_THE_S7_COUNTERS_RID = 83 + NATIVE_THE_S7_TIMERS_RID = 84 + + # DB AccessArea base (add DB number to get area ID) + DB_ACCESS_AREA_BASE = 0x8A0E0000 + + class SoftDataType(IntEnum): """PLC soft data types (used in variable metadata / tag descriptions). diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index b40b587e..23f4ee5f 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -40,8 +40,14 @@ ProtocolVersion, SoftDataType, ) -from .vlq import encode_uint32_vlq, decode_uint32_vlq -from .codec import encode_header, decode_header, encode_typed_value +from .vlq import encode_uint32_vlq, decode_uint32_vlq, encode_uint64_vlq +from .codec import ( + encode_header, + decode_header, + encode_typed_value, + encode_pvalue_blob, + decode_pvalue_to_bytes, +) logger = logging.getLogger(__name__) @@ -613,7 +619,14 @@ def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> return bytes(response) def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle GetMultiVariables -- read variables from data blocks.""" + """Handle GetMultiVariables -- read variables from data blocks. + + Parses the S7CommPlus request format with ItemAddress structures. + The server extracts db_number from AccessArea and byte offset/size + from the LID values. + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs + """ response = bytearray() response += struct.pack( ">BHHHHIB", @@ -625,49 +638,45 @@ def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_dat session_id, 0x00, ) - response += encode_uint32_vlq(0) # Return code: success - # Parse request: expect object_id + variable addresses - offset = 0 - items: list[tuple[int, int, int]] = [] # (db_num, byte_offset, byte_size) + # Parse request payload + items = _server_parse_read_request(request_data) - # Simple request format: VLQ item count, then for each item: - # VLQ object_id, VLQ offset, VLQ size - if len(request_data) > 0: - count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed + # ReturnValue: success + response += encode_uint64_vlq(0) - for _ in range(count): - if offset >= len(request_data): - break - obj_id, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_offset, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_size, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - db_num = obj_id & 0xFFFF - items.append((db_num, byte_offset, byte_size)) - - # Read data for each item - response += encode_uint32_vlq(len(items)) - for db_num, byte_offset, byte_size in items: + # Value list: ItemNumber (1-based) + PValue, terminated by ItemNumber=0 + for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): db = self._data_blocks.get(db_num) if db is not None: data = db.read(byte_offset, byte_size) - response += encode_uint32_vlq(0) # Success - response += encode_uint32_vlq(len(data)) - response += data - else: - response += encode_uint32_vlq(1) # Error: not found - response += encode_uint32_vlq(0) + response += encode_uint32_vlq(i) # ItemNumber + response += encode_pvalue_blob(data) # Value as BLOB + # Errors handled in error list below + + # Terminate value list + response += encode_uint32_vlq(0) + + # Error list + for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): + db = self._data_blocks.get(db_num) + if db is None: + response += encode_uint32_vlq(i) # ErrorItemNumber + response += encode_uint64_vlq(0x8104) # Error: object not found + + # Terminate error list + response += encode_uint32_vlq(0) + + # IntegrityId + response += encode_uint32_vlq(0) - response += struct.pack(">I", 0) return bytes(response) def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle SetMultiVariables -- write variables to data blocks.""" + """Handle SetMultiVariables -- write variables to data blocks. + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs + """ response = bytearray() response += struct.pack( ">BHHHHIB", @@ -680,42 +689,32 @@ def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_dat 0x00, ) - # Parse request: VLQ item count, then for each item: - # VLQ object_id, VLQ offset, VLQ data_length, data bytes - offset = 0 - results: list[int] = [] + # Parse request payload + items, values = _server_parse_write_request(request_data) - if len(request_data) > 0: - count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed + # Write data + errors: list[tuple[int, int]] = [] + for i, ((db_num, byte_offset, _), data) in enumerate(zip(items, values), 1): + db = self._data_blocks.get(db_num) + if db is not None: + db.write(byte_offset, data) + else: + errors.append((i, 0x8104)) # Object not found - for _ in range(count): - if offset >= len(request_data): - break - obj_id, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_offset, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - data_len, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - data = request_data[offset : offset + data_len] - offset += data_len - - db_num = obj_id & 0xFFFF - db = self._data_blocks.get(db_num) - if db is not None: - db.write(byte_offset, data) - results.append(0) # Success - else: - results.append(1) # Error: not found + # ReturnValue: success + response += encode_uint64_vlq(0) - response += encode_uint32_vlq(0) # Return code: success - response += encode_uint32_vlq(len(results)) - for r in results: - response += encode_uint32_vlq(r) + # Error list + for err_item, err_code in errors: + response += encode_uint32_vlq(err_item) + response += encode_uint64_vlq(err_code) + + # Terminate error list + response += encode_uint32_vlq(0) + + # IntegrityId + response += encode_uint32_vlq(0) - response += struct.pack(">I", 0) return bytes(response) def _build_error_response(self, seq_num: int, session_id: int, function_code: int) -> bytes: @@ -751,3 +750,153 @@ def __enter__(self) -> "S7CommPlusServer": def __exit__(self, *args: Any) -> None: self.stop() + + +# -- Server-side request parsers -- + + +def _server_parse_read_request(request_data: bytes) -> list[tuple[int, int, int]]: + """Parse a GetMultiVariables request payload on the server side. + + Extracts (db_number, byte_offset, byte_size) for each item from the + S7CommPlus ItemAddress format. + + Returns: + List of (db_number, byte_offset, byte_size) tuples + """ + if not request_data: + return [] + + offset = 0 + items: list[tuple[int, int, int]] = [] + + # LinkId (UInt32 fixed) + if offset + 4 > len(request_data): + return [] + offset += 4 + + # ItemCount (VLQ) + item_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # FieldCount (VLQ) + _field_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Parse each ItemAddress + for _ in range(item_count): + if offset >= len(request_data): + break + + # SymbolCrc + _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessArea + access_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # NumberOfLIDs + num_lids, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessSubArea (first LID) + _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Additional LIDs + lids: list[int] = [] + for _ in range(num_lids - 1): # -1 because AccessSubArea counts as one + if offset >= len(request_data): + break + lid_val, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + lids.append(lid_val) + + # Extract db_number from AccessArea + db_num = access_area & 0xFFFF + + # Extract byte offset and size from LIDs + byte_offset = lids[0] if len(lids) > 0 else 0 + byte_size = lids[1] if len(lids) > 1 else 1 + + items.append((db_num, byte_offset, byte_size)) + + return items + + +def _server_parse_write_request(request_data: bytes) -> tuple[list[tuple[int, int, int]], list[bytes]]: + """Parse a SetMultiVariables request payload on the server side. + + Returns: + Tuple of (items, values) where items is list of (db_number, byte_offset, byte_size) + and values is list of raw bytes to write + """ + if not request_data: + return [], [] + + offset = 0 + + # InObjectId (UInt32 fixed) + if offset + 4 > len(request_data): + return [], [] + offset += 4 + + # ItemCount (VLQ) + item_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # FieldCount (VLQ) + _field_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Parse each ItemAddress + items: list[tuple[int, int, int]] = [] + for _ in range(item_count): + if offset >= len(request_data): + break + + # SymbolCrc + _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessArea + access_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # NumberOfLIDs + num_lids, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessSubArea + _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Additional LIDs + lids: list[int] = [] + for _ in range(num_lids - 1): + if offset >= len(request_data): + break + lid_val, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + lids.append(lid_val) + + db_num = access_area & 0xFFFF + byte_offset = lids[0] if len(lids) > 0 else 0 + byte_size = lids[1] if len(lids) > 1 else 1 + items.append((db_num, byte_offset, byte_size)) + + # Parse value list: ItemNumber (VLQ, 1-based) + PValue + values: list[bytes] = [] + for _ in range(item_count): + if offset >= len(request_data): + break + item_nr, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + if item_nr == 0: + break + raw_bytes, consumed = decode_pvalue_to_bytes(request_data, offset) + offset += consumed + values.append(raw_bytes) + + return items, values From 51179ae6e1c7d6eb5a69e9d607586c7f449c937b Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 9 Mar 2026 10:48:56 +0200 Subject: [PATCH 10/27] Fix S7CommPlus LID byte offsets to use 1-based addressing S7CommPlus protocol uses 1-based LID byte offsets, but the client was sending 0-based offsets. This caused real PLCs to reject all db_read and db_write requests. Also fixes lint issues in e2e test file. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/client.py | 7 ++--- snap7/s7commplus/connection.py | 4 +-- snap7/s7commplus/server.py | 6 ++-- tests/test_s7commplus_e2e.py | 51 +++++++++++++--------------------- 4 files changed, 26 insertions(+), 42 deletions(-) diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index e5ddabd4..ceb9bf41 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -160,8 +160,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload = _build_write_payload([(db_number, start, data)]) logger.debug( - f"db_write: db={db_number} start={start} data_len={len(data)} " - f"data={data.hex(' ')} payload={payload.hex(' ')}" + f"db_write: db={db_number} start={start} data_len={len(data)} data={data.hex(' ')} payload={payload.hex(' ')}" ) response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, payload) @@ -239,7 +238,7 @@ def _build_read_payload(items: list[tuple[int, int, int]]) -> bytes: addr_bytes, field_count = encode_item_address( access_area=access_area, access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start, size], + lids=[start + 1, size], # LID byte offsets are 1-based in S7CommPlus ) addresses.append(addr_bytes) total_field_count += field_count @@ -338,7 +337,7 @@ def _build_write_payload(items: list[tuple[int, int, bytes]]) -> bytes: addr_bytes, field_count = encode_item_address( access_area=access_area, access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start, len(data)], + lids=[start + 1, len(data)], # LID byte offsets are 1-based in S7CommPlus ) addresses.append(addr_bytes) total_field_count += field_count diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index e3ba388a..6a98ad5e 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -218,9 +218,7 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: ) request = request_header + payload - logger.debug( - f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}" - ) + logger.debug(f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}") logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 23f4ee5f..27c54adc 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -816,8 +816,8 @@ def _server_parse_read_request(request_data: bytes) -> list[tuple[int, int, int] # Extract db_number from AccessArea db_num = access_area & 0xFFFF - # Extract byte offset and size from LIDs - byte_offset = lids[0] if len(lids) > 0 else 0 + # Extract byte offset and size from LIDs (LID offsets are 1-based) + byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 byte_size = lids[1] if len(lids) > 1 else 1 items.append((db_num, byte_offset, byte_size)) @@ -882,7 +882,7 @@ def _server_parse_write_request(request_data: bytes) -> tuple[list[tuple[int, in lids.append(lid_val) db_num = access_area & 0xFFFF - byte_offset = lids[0] if len(lids) > 0 else 0 + byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 # LID offsets are 1-based byte_size = lids[1] if len(lids) > 1 else 1 items.append((db_num, byte_offset, byte_size)) diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py index 46da4b05..f8c8bf0d 100644 --- a/tests/test_s7commplus_e2e.py +++ b/tests/test_s7commplus_e2e.py @@ -441,17 +441,17 @@ def tearDownClass(cls) -> None: def test_diag_connection_info(self) -> None: """Dump connection state after successful connect.""" - print(f"\n{'='*60}") - print(f"DIAGNOSTIC: Connection Info") + print(f"\n{'=' * 60}") + print("DIAGNOSTIC: Connection Info") print(f" connected: {self.client.connected}") print(f" protocol_version: V{self.client.protocol_version}") print(f" session_id: 0x{self.client.session_id:08X} ({self.client.session_id})") - print(f"{'='*60}") + print(f"{'=' * 60}") self.assertTrue(self.client.connected) def test_diag_explore_raw(self) -> None: """Explore and dump the raw response for analysis.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Explore raw response") try: data = self.client.explore() @@ -464,22 +464,22 @@ def test_diag_explore_raw(self) -> None: print(f" {i:04x}: {hex_str:<96s} {ascii_str}") except Exception as e: print(f" Explore failed: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_db_read_single_byte(self) -> None: """Try to read a single byte from DB1 offset 0 and dump everything.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: db_read(DB1, offset=0, size=1)") try: data = self.client.db_read(DB_READ_ONLY, 0, 1) print(f" Success! Got {len(data)} bytes: {data.hex(' ')}") except Exception as e: print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_db_read_full_block(self) -> None: """Try to read the full test DB and dump everything.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print(f"DIAGNOSTIC: db_read(DB{DB_READ_ONLY}, offset=0, size={DB_SIZE})") try: data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) @@ -489,7 +489,7 @@ def test_diag_db_read_full_block(self) -> None: print(f" {i:04x}: {chunk.hex(' ')}") except Exception as e: print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_raw_get_multi_variables(self) -> None: """Send a raw GetMultiVariables with different payload formats and dump responses. @@ -499,7 +499,7 @@ def test_diag_raw_get_multi_variables(self) -> None: from snap7.s7commplus.protocol import FunctionCode from snap7.s7commplus.vlq import encode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Raw GetMultiVariables payload experiments") assert self.client._connection is not None @@ -507,10 +507,7 @@ def test_diag_raw_get_multi_variables(self) -> None: # Experiment 1: Our current format (item_count + object_id + offset + size) payloads = { "current_format (count=1, obj=0x00010001, off=0, sz=2)": ( - encode_uint32_vlq(1) - + encode_uint32_vlq(0x00010001) - + encode_uint32_vlq(0) - + encode_uint32_vlq(2) + encode_uint32_vlq(1) + encode_uint32_vlq(0x00010001) + encode_uint32_vlq(0) + encode_uint32_vlq(2) ), "empty_payload": b"", "just_zero": encode_uint32_vlq(0), @@ -521,9 +518,7 @@ def test_diag_raw_get_multi_variables(self) -> None: print(f"\n --- {label} ---") print(f" Payload ({len(payload)} bytes): {payload.hex(' ')}") try: - response = self.client._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, payload - ) + response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) print(f" Response ({len(response)} bytes): {response.hex(' ')}") # Try to parse return code @@ -538,14 +533,13 @@ def test_diag_raw_get_multi_variables(self) -> None: except Exception as e: print(f" EXCEPTION: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") def test_diag_raw_set_variable(self) -> None: """Try SetVariable (0x04F2) instead of SetMultiVariables to see if PLC responds differently.""" from snap7.s7commplus.protocol import FunctionCode - from snap7.s7commplus.vlq import encode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Raw SetVariable / GetVariable experiments") assert self.client._connection is not None @@ -565,14 +559,14 @@ def test_diag_raw_set_variable(self) -> None: except Exception as e: print(f" EXCEPTION: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") def test_diag_explore_then_read(self) -> None: """Explore first to discover object IDs, then try reading using those IDs.""" from snap7.s7commplus.protocol import FunctionCode, ElementID from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Explore -> extract object IDs -> try reading") assert self.client._connection is not None @@ -597,16 +591,9 @@ def test_diag_explore_then_read(self) -> None: # Try reading using each discovered object ID for obj_id in object_ids[:5]: # Limit to first 5 print(f"\n --- Read using object_id=0x{obj_id:08X} ---") - payload = ( - encode_uint32_vlq(1) - + encode_uint32_vlq(obj_id) - + encode_uint32_vlq(0) - + encode_uint32_vlq(4) - ) + payload = encode_uint32_vlq(1) + encode_uint32_vlq(obj_id) + encode_uint32_vlq(0) + encode_uint32_vlq(4) try: - response = self.client._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, payload - ) + response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) print(f" Response ({len(response)} bytes): {response.hex(' ')}") if len(response) > 0: rc, consumed = decode_uint32_vlq(response, 0) @@ -617,4 +604,4 @@ def test_diag_explore_then_read(self) -> None: except Exception as e: print(f" Explore failed: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") From 010b35809cd0c37ba7e244c0f3b6ed2bf288c9ce Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 9 Mar 2026 20:21:31 +0200 Subject: [PATCH 11/27] Add S7CommPlus session setup and legacy S7 fallback for data operations Implement the missing SetMultiVariables session handshake step that echoes ServerSessionVersion (attr 306) back to the PLC after CreateObject. Without this, PLCs reject data operations with ERROR2 (0x05A9). For PLCs that don't provide ServerSessionVersion or don't support S7CommPlus data operations, the client transparently falls back to the legacy S7 protocol. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 105 ++++++++++++- snap7/s7commplus/client.py | 111 ++++++++++++- snap7/s7commplus/connection.py | 257 ++++++++++++++++++++++++++++++- snap7/s7commplus/protocol.py | 1 + 4 files changed, 465 insertions(+), 9 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index 41780192..f7c77995 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -4,6 +4,10 @@ Provides the same API as S7CommPlusClient but using asyncio for non-blocking I/O. Uses asyncio.Lock for concurrent safety. +When a PLC does not support S7CommPlus data operations, the client +transparently falls back to the legacy S7 protocol for data block +read/write operations (using synchronous calls in an executor). + Example:: async with S7CommPlusAsyncClient() as client: @@ -27,8 +31,8 @@ S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, ) -from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier +from .vlq import encode_uint32_vlq, decode_uint64_vlq from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response logger = logging.getLogger(__name__) @@ -46,6 +50,9 @@ class S7CommPlusAsyncClient: Uses asyncio for all I/O operations and asyncio.Lock for concurrent safety when shared between multiple coroutines. + + When the PLC does not support S7CommPlus data operations, the client + automatically falls back to legacy S7 protocol for db_read/db_write. """ def __init__(self) -> None: @@ -56,9 +63,17 @@ def __init__(self) -> None: self._protocol_version: int = 0 self._connected = False self._lock = asyncio.Lock() + self._legacy_client: Optional[Any] = None + self._use_legacy_data: bool = False + self._host: str = "" + self._port: int = 102 + self._rack: int = 0 + self._slot: int = 1 @property def connected(self) -> bool: + if self._use_legacy_data and self._legacy_client is not None: + return bool(self._legacy_client.connected) return self._connected @property @@ -69,6 +84,11 @@ def protocol_version(self) -> int: def session_id(self) -> int: return self._session_id + @property + def using_legacy_fallback(self) -> bool: + """Whether the client is using legacy S7 protocol for data operations.""" + return self._use_legacy_data + async def connect( self, host: str, @@ -78,12 +98,20 @@ async def connect( ) -> None: """Connect to an S7-1200/1500 PLC. + If the PLC does not support S7CommPlus data operations, a secondary + legacy S7 connection is established transparently for data access. + Args: host: PLC IP address or hostname port: TCP port (default 102) rack: PLC rack number slot: PLC slot number """ + self._host = host + self._port = port + self._rack = rack + self._slot = slot + # TCP connect self._reader, self._writer = await asyncio.open_connection(host, port) @@ -101,12 +129,56 @@ async def connect( logger.info( f"Async S7CommPlus connected to {host}:{port}, version=V{self._protocol_version}, session={self._session_id}" ) + + # Probe S7CommPlus data operations + if not await self._probe_s7commplus_data(): + logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") + await self._setup_legacy_fallback() + except Exception: await self.disconnect() raise + async def _probe_s7commplus_data(self) -> bool: + """Test if the PLC supports S7CommPlus data operations.""" + try: + payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) + payload += encode_object_qualifier() + payload += struct.pack(">I", 0) + + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + if len(response) < 1: + return False + return_value, _ = decode_uint64_vlq(response, 0) + if return_value != 0: + logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") + return False + return True + except Exception as e: + logger.debug(f"S7CommPlus probe failed: {e}") + return False + + async def _setup_legacy_fallback(self) -> None: + """Establish a secondary legacy S7 connection for data operations.""" + from ..client import Client + + loop = asyncio.get_event_loop() + client = Client() + await loop.run_in_executor(None, lambda: client.connect(self._host, self._rack, self._slot, self._port)) + self._legacy_client = client + self._use_legacy_data = True + logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") + async def disconnect(self) -> None: """Disconnect from PLC.""" + if self._legacy_client is not None: + try: + self._legacy_client.disconnect() + except Exception: + pass + self._legacy_client = None + self._use_legacy_data = False + if self._connected and self._session_id: try: await self._delete_session() @@ -138,6 +210,12 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + data = await loop.run_in_executor(None, lambda: client.db_read(db_number, start, size)) + return bytes(data) + payload = _build_read_payload([(db_number, start, size)]) response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) @@ -156,6 +234,12 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: start: Start byte offset data: Bytes to write """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + await loop.run_in_executor(None, lambda: client.db_write(db_number, start, bytearray(data))) + return + payload = _build_write_payload([(db_number, start, data)]) response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, payload) _parse_write_response(response) @@ -169,11 +253,24 @@ async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: Returns: List of raw bytes for each item """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + multi_results: list[bytes] = [] + for db_number, start, size in items: + + def _read(db: int = db_number, s: int = start, sz: int = size) -> bytearray: + return bytearray(client.db_read(db, s, sz)) + + data = await loop.run_in_executor(None, _read) + multi_results.append(bytes(data)) + return multi_results + payload = _build_read_payload(items) response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - results = _parse_read_response(response) - return [r if r is not None else b"" for r in results] + parsed = _parse_read_response(response) + return [r if r is not None else b"" for r in parsed] async def explore(self) -> bytes: """Browse the PLC object tree. diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index ceb9bf41..d5b38a40 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -9,6 +9,11 @@ version is auto-detected from the PLC's CreateObject response during connection setup. +When a PLC does not support S7CommPlus data operations (e.g. PLCs that +accept S7CommPlus sessions but return ERROR2 for GetMultiVariables), +the client transparently falls back to the legacy S7 protocol for +data block read/write operations. + Status: V1 connection is functional. V2/V3/TLS authentication planned. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) @@ -42,6 +47,9 @@ class S7CommPlusClient: The protocol version is auto-detected during connection. + When the PLC does not support S7CommPlus data operations, the client + automatically falls back to legacy S7 protocol for db_read/db_write. + Example:: client = S7CommPlusClient() @@ -58,9 +66,17 @@ class S7CommPlusClient: def __init__(self) -> None: self._connection: Optional[S7CommPlusConnection] = None + self._legacy_client: Optional[Any] = None + self._use_legacy_data: bool = False + self._host: str = "" + self._port: int = 102 + self._rack: int = 0 + self._slot: int = 1 @property def connected(self) -> bool: + if self._use_legacy_data and self._legacy_client is not None: + return bool(self._legacy_client.connected) return self._connection is not None and self._connection.connected @property @@ -77,6 +93,11 @@ def session_id(self) -> int: return 0 return self._connection.session_id + @property + def using_legacy_fallback(self) -> bool: + """Whether the client is using legacy S7 protocol for data operations.""" + return self._use_legacy_data + def connect( self, host: str, @@ -90,6 +111,9 @@ def connect( ) -> None: """Connect to an S7-1200/1500 PLC using S7CommPlus. + If the PLC does not support S7CommPlus data operations, a secondary + legacy S7 connection is established transparently for data access. + Args: host: PLC IP address or hostname port: TCP port (default 102) @@ -100,6 +124,11 @@ def connect( tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) """ + self._host = host + self._port = port + self._rack = rack + self._slot = slot + self._connection = S7CommPlusConnection( host=host, port=port, @@ -112,8 +141,63 @@ def connect( tls_ca=tls_ca, ) + # Probe S7CommPlus data operations with a minimal request + if not self._probe_s7commplus_data(): + logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") + self._setup_legacy_fallback() + + def _probe_s7commplus_data(self) -> bool: + """Test if the PLC supports S7CommPlus data operations. + + Sends a minimal GetMultiVariables request with zero items. If the PLC + responds with ERROR2 or a non-zero return code, data operations are + not supported. + + Returns: + True if S7CommPlus data operations work. + """ + if self._connection is None: + return False + + try: + # Send a minimal GetMultiVariables with 0 items + payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) + payload += encode_object_qualifier() + payload += struct.pack(">I", 0) + + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + + # Check if we got a valid response (return value = 0) + if len(response) < 1: + return False + return_value, _ = decode_uint64_vlq(response, 0) + if return_value != 0: + logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") + return False + return True + except Exception as e: + logger.debug(f"S7CommPlus probe failed: {e}") + return False + + def _setup_legacy_fallback(self) -> None: + """Establish a secondary legacy S7 connection for data operations.""" + from ..client import Client + + self._legacy_client = Client() + self._legacy_client.connect(self._host, self._rack, self._slot, self._port) + self._use_legacy_data = True + logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") + def disconnect(self) -> None: """Disconnect from PLC.""" + if self._legacy_client is not None: + try: + self._legacy_client.disconnect() + except Exception: + pass + self._legacy_client = None + self._use_legacy_data = False + if self._connection: self._connection.disconnect() self._connection = None @@ -123,6 +207,9 @@ def disconnect(self) -> None: def db_read(self, db_number: int, start: int, size: int) -> bytes: """Read raw bytes from a data block. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol transparently. + Args: db_number: Data block number start: Start byte offset @@ -131,6 +218,9 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ + if self._use_legacy_data and self._legacy_client is not None: + return bytes(self._legacy_client.db_read(db_number, start, size)) + if self._connection is None: raise RuntimeError("Not connected") @@ -150,11 +240,18 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol transparently. + Args: db_number: Data block number start: Start byte offset data: Bytes to write """ + if self._use_legacy_data and self._legacy_client is not None: + self._legacy_client.db_write(db_number, start, bytearray(data)) + return + if self._connection is None: raise RuntimeError("Not connected") @@ -171,12 +268,22 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol (individual reads) transparently. + Args: items: List of (db_number, start_offset, size) tuples Returns: List of raw bytes for each item """ + if self._use_legacy_data and self._legacy_client is not None: + results = [] + for db_number, start, size in items: + data = self._legacy_client.db_read(db_number, start, size) + results.append(bytes(data)) + return results + if self._connection is None: raise RuntimeError("Not connected") @@ -186,8 +293,8 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") - results = _parse_read_response(response) - return [r if r is not None else b"" for r in results] + parsed = _parse_read_response(response) + return [r if r is not None else b"" for r in parsed] # -- Explore (browse PLC object tree) -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 6a98ad5e..fbbaf60d 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -54,13 +54,27 @@ S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, ) -from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier +from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq from .protocol import DataType logger = logging.getLogger(__name__) +def _element_size(datatype: int) -> int: + """Return the fixed byte size for an array element, or 0 for variable-length.""" + if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return 2 + elif datatype in (DataType.REAL, DataType.RID): + return 4 + elif datatype in (DataType.LREAL, DataType.TIMESTAMP): + return 8 + else: + return 0 + + class S7CommPlusConnection: """S7CommPlus connection with multi-version support. @@ -95,6 +109,7 @@ def __init__( self._protocol_version: int = 0 # Detected from PLC response self._tls_active: bool = False self._connected = False + self._server_session_version: Optional[int] = None @property def connected(self) -> bool: @@ -153,7 +168,13 @@ def connect( # Step 4: CreateObject (S7CommPlus session setup) self._create_session() - # Step 5: Version-specific authentication + # Step 5: Session setup - echo ServerSessionVersion back to PLC + if self._server_session_version is not None: + self._setup_session() + else: + logger.warning("PLC did not provide ServerSessionVersion - session setup incomplete") + + # Step 6: Version-specific authentication if self._protocol_version >= ProtocolVersion.V3: if not use_tls: logger.warning( @@ -186,6 +207,7 @@ def disconnect(self) -> None: self._session_id = 0 self._sequence_number = 0 self._protocol_version = 0 + self._server_session_version = None self._iso_conn.disconnect() def send_request(self, function_code: int, payload: bytes = b"") -> bytes: @@ -418,6 +440,235 @@ def _create_session(self) -> None: logger.debug(f"CreateObject response payload: {response[14:].hex(' ')}") logger.debug(f"Session created: id=0x{self._session_id:08X} ({self._session_id}), version=V{version}") + # Parse response payload to extract ServerSessionVersion + self._parse_create_object_response(response[14:]) + + def _parse_create_object_response(self, payload: bytes) -> None: + """Parse CreateObject response payload to extract ServerSessionVersion. + + The response contains a PObject tree with attributes. We scan for + attribute 306 (ServerSessionVersion) which must be echoed back to + complete the session handshake. + + Args: + payload: Response payload after the 14-byte response header + """ + offset = 0 + while offset < len(payload): + tag = payload[offset] + + if tag == ElementID.ATTRIBUTE: + offset += 1 + if offset >= len(payload): + break + attr_id, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + + if attr_id == ObjectId.SERVER_SESSION_VERSION: + # Next bytes are the typed value: flags + datatype + VLQ value + if offset + 2 > len(payload): + break + _flags = payload[offset] + datatype = payload[offset + 1] + offset += 2 + if datatype == DataType.UDINT: + value, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + self._server_session_version = value + logger.info(f"ServerSessionVersion = {value}") + return + elif datatype == DataType.DWORD: + value, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + self._server_session_version = value + logger.info(f"ServerSessionVersion = {value}") + return + else: + # Skip unknown type - try to continue scanning + logger.debug(f"ServerSessionVersion has unexpected type {datatype:#04x}") + else: + # Skip this attribute's value - we don't parse it, just advance + # Try to skip the typed value (flags + datatype + value) + if offset + 2 > len(payload): + break + _flags = payload[offset] + datatype = payload[offset + 1] + offset += 2 + offset = self._skip_typed_value(payload, offset, datatype, _flags) + + elif tag == ElementID.START_OF_OBJECT: + offset += 1 + # Skip RelationId (4 bytes fixed) + ClassId (VLQ) + ClassFlags (VLQ) + AttributeId (VLQ) + if offset + 4 > len(payload): + break + offset += 4 # RelationId + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # ClassId + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # ClassFlags + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # AttributeId + + elif tag == ElementID.TERMINATING_OBJECT: + offset += 1 + + elif tag == 0x00: + # Null terminator / padding + offset += 1 + + else: + # Unknown tag - try to skip + offset += 1 + + logger.debug("ServerSessionVersion not found in CreateObject response") + + def _skip_typed_value(self, data: bytes, offset: int, datatype: int, flags: int) -> int: + """Skip over a typed value in the PObject tree. + + Best-effort: advances offset past common value types. + Returns new offset. + """ + is_array = bool(flags & 0x10) + + if is_array: + if offset >= len(data): + return offset + count, consumed = decode_uint32_vlq(data, offset) + offset += consumed + # For fixed-size types, skip count * size + elem_size = _element_size(datatype) + if elem_size > 0: + offset += count * elem_size + else: + # Variable-length: skip each VLQ element + for _ in range(count): + if offset >= len(data): + break + _, consumed = decode_uint32_vlq(data, offset) + offset += consumed + return offset + + if datatype == DataType.NULL: + return offset + elif datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return offset + 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return offset + 2 + elif datatype in (DataType.UDINT, DataType.DWORD, DataType.AID, DataType.DINT): + _, consumed = decode_uint32_vlq(data, offset) + return offset + consumed + elif datatype in (DataType.ULINT, DataType.LWORD, DataType.LINT): + _, consumed = decode_uint64_vlq(data, offset) + return offset + consumed + elif datatype == DataType.REAL: + return offset + 4 + elif datatype == DataType.LREAL: + return offset + 8 + elif datatype == DataType.TIMESTAMP: + return offset + 8 + elif datatype == DataType.TIMESPAN: + _, consumed = decode_uint64_vlq(data, offset) # int64 VLQ + return offset + consumed + elif datatype == DataType.RID: + return offset + 4 + elif datatype in (DataType.BLOB, DataType.WSTRING): + length, consumed = decode_uint32_vlq(data, offset) + return offset + consumed + length + elif datatype == DataType.STRUCT: + count, consumed = decode_uint32_vlq(data, offset) + offset += consumed + for _ in range(count): + if offset + 2 > len(data): + break + sub_flags = data[offset] + sub_type = data[offset + 1] + offset += 2 + offset = self._skip_typed_value(data, offset, sub_type, sub_flags) + return offset + else: + # Unknown type - can't skip reliably + return offset + + def _setup_session(self) -> None: + """Send SetMultiVariables to echo ServerSessionVersion back to the PLC. + + This completes the session handshake by writing the ServerSessionVersion + attribute back to the session object. Without this step, the PLC rejects + all subsequent data operations with ERROR2 (0x05A9). + + Reference: thomas-v2/S7CommPlusDriver SetSessionSetupData + """ + if self._server_session_version is None: + return + + seq_num = self._next_sequence_number() + + # Build SetMultiVariables request + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.SET_MULTI_VARIABLES, + 0x0000, + seq_num, + self._session_id, + 0x36, # Transport flags + ) + + payload = bytearray() + # InObjectId = session ID (tells PLC which object we're writing to) + payload += struct.pack(">I", self._session_id) + # Item count = 1 + payload += encode_uint32_vlq(1) + # Total address field count = 1 (just the attribute ID) + payload += encode_uint32_vlq(1) + # Address: attribute ID = ServerSessionVersion (306) as VLQ + payload += encode_uint32_vlq(ObjectId.SERVER_SESSION_VERSION) + # Value: ItemNumber = 1 (VLQ) + payload += encode_uint32_vlq(1) + # PValue: flags=0x00, type=UDInt, VLQ-encoded value + payload += bytes([0x00, DataType.UDINT]) + payload += encode_uint32_vlq(self._server_session_version) + # Fill byte + payload += bytes([0x00]) + # ObjectQualifier + payload += encode_object_qualifier() + # Trailing padding + payload += struct.pack(">I", 0) + + request += bytes(payload) + + # Wrap in S7CommPlus frame + frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) + + logger.debug(f"=== SetupSession === sending ({len(frame)} bytes): {frame.hex(' ')}") + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + logger.debug(f"=== SetupSession === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") + + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed : consumed + data_length] + + if len(response) < 14: + from ..error import S7ConnectionError + + raise S7ConnectionError("SetupSession response too short") + + resp_func = struct.unpack_from(">H", response, 3)[0] + logger.debug(f"SetupSession response: function=0x{resp_func:04X}") + + # Parse return value from payload + resp_payload = response[14:] + if len(resp_payload) >= 1: + return_value, _ = decode_uint64_vlq(resp_payload, 0) + if return_value != 0: + logger.warning(f"SetupSession: PLC returned error {return_value}") + else: + logger.info("Session setup completed successfully") + def _delete_session(self) -> None: """Send DeleteObject to close the session.""" seq_num = self._next_sequence_number() diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 71587639..2095cb29 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -100,6 +100,7 @@ class ObjectId(IntEnum): CLASS_SERVER_SESSION = 287 OBJECT_NULL_SERVER_SESSION = 288 SERVER_SESSION_CLIENT_RID = 300 + SERVER_SESSION_VERSION = 306 # Default TSAP for S7CommPlus connections From 61ba9f0112595981842c46560639ade2c8e32fc7 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Tue, 10 Mar 2026 14:53:16 +0200 Subject: [PATCH 12/27] Potential fix for code scanning alert no. 9: Binding a socket to all network interfaces Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com> --- snap7/s7commplus/server.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 27c54adc..cc08a057 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -258,7 +258,7 @@ def get_db(self, db_number: int) -> Optional[DataBlock]: """Get a registered data block.""" return self._data_blocks.get(db_number) - def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: + def start(self, host: str = "127.0.0.1", port: int = 11020) -> None: """Start the server. Args: From a35ef5ad5cc673b8e408dd7bcb15033ba9d38cb0 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:16:08 +0200 Subject: [PATCH 13/27] Add S7CommPlus protocol scaffolding for S7-1200/1500 support Adds the snap7.s7commplus package as a foundation for future S7CommPlus protocol support, targeting all S7-1200/1500 PLCs (V1/V2/V3/TLS). Includes: - Protocol constants (opcodes, function codes, data types, element IDs) - VLQ encoding/decoding (Variable-Length Quantity, the S7CommPlus wire format) - Codec for frame headers, request/response headers, and typed values - Connection skeleton with multi-version support (V1/V2/V3/TLS) - Client stub with symbolic variable access API - 86 passing tests for VLQ and codec modules The wire protocol (VLQ, data types, object model) is the same across all protocol versions -- only the session authentication layer differs. The protocol version is auto-detected from the PLC's CreateObject response. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/__init__.py | 6 +- snap7/s7commplus/client.py | 497 ++++++------------------ snap7/s7commplus/codec.py | 209 +---------- snap7/s7commplus/connection.py | 666 +++++---------------------------- snap7/s7commplus/protocol.py | 58 +-- snap7/s7commplus/vlq.py | 1 - 6 files changed, 218 insertions(+), 1219 deletions(-) diff --git a/snap7/s7commplus/__init__.py b/snap7/s7commplus/__init__.py index f8ff995a..3617a832 100644 --- a/snap7/s7commplus/__init__.py +++ b/snap7/s7commplus/__init__.py @@ -7,9 +7,9 @@ Supported PLC / firmware targets:: - V1: S7-1200 FW V4.0+ (simple session handshake) - V2: S7-1200/1500 older FW (session authentication) - V3: S7-1200/1500 pre-TIA V17 (public-key key exchange) + V1: S7-1200 FW V4.0+ (trivial anti-replay) + V2: S7-1200/1500 older FW (proprietary session auth) + V3: S7-1200/1500 pre-TIA V17 (ECC key exchange) V3 + TLS: TIA Portal V17+ (TLS 1.3 with per-device certs) Protocol stack:: diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index d5b38a40..988bbd31 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -9,29 +9,16 @@ version is auto-detected from the PLC's CreateObject response during connection setup. -When a PLC does not support S7CommPlus data operations (e.g. PLCs that -accept S7CommPlus sessions but return ERROR2 for GetMultiVariables), -the client transparently falls back to the legacy S7 protocol for -data block read/write operations. - -Status: V1 connection is functional. V2/V3/TLS authentication planned. +Status: experimental scaffolding -- not yet functional. +All methods raise NotImplementedError with guidance on what needs to be done. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ import logging -import struct from typing import Any, Optional from .connection import S7CommPlusConnection -from .protocol import FunctionCode, Ids -from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq -from .codec import ( - encode_item_address, - encode_object_qualifier, - encode_pvalue_blob, - decode_pvalue_to_bytes, -) logger = logging.getLogger(__name__) @@ -47,464 +34,224 @@ class S7CommPlusClient: The protocol version is auto-detected during connection. - When the PLC does not support S7CommPlus data operations, the client - automatically falls back to legacy S7 protocol for db_read/db_write. - - Example:: + Example (future, once implemented):: client = S7CommPlusClient() client.connect("192.168.1.10") - - # Read raw bytes from DB1 - data = client.db_read(1, 0, 4) - - # Write raw bytes to DB1 - client.db_write(1, 0, struct.pack(">f", 23.5)) - + value = client.read_variable("DB1.myVariable") client.disconnect() """ def __init__(self) -> None: self._connection: Optional[S7CommPlusConnection] = None - self._legacy_client: Optional[Any] = None - self._use_legacy_data: bool = False - self._host: str = "" - self._port: int = 102 - self._rack: int = 0 - self._slot: int = 1 @property def connected(self) -> bool: - if self._use_legacy_data and self._legacy_client is not None: - return bool(self._legacy_client.connected) return self._connection is not None and self._connection.connected - @property - def protocol_version(self) -> int: - """Protocol version negotiated with the PLC.""" - if self._connection is None: - return 0 - return self._connection.protocol_version - - @property - def session_id(self) -> int: - """Session ID assigned by the PLC.""" - if self._connection is None: - return 0 - return self._connection.session_id - - @property - def using_legacy_fallback(self) -> bool: - """Whether the client is using legacy S7 protocol for data operations.""" - return self._use_legacy_data - def connect( self, host: str, port: int = 102, rack: int = 0, slot: int = 1, - use_tls: bool = False, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, ) -> None: """Connect to an S7-1200/1500 PLC using S7CommPlus. - If the PLC does not support S7CommPlus data operations, a secondary - legacy S7 connection is established transparently for data access. - Args: host: PLC IP address or hostname port: TCP port (default 102) rack: PLC rack number slot: PLC slot number - use_tls: Whether to attempt TLS (requires V3 PLC + certs) tls_cert: Path to client TLS certificate (PEM) tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) + + Raises: + NotImplementedError: S7CommPlus connection is not yet implemented """ - self._host = host - self._port = port - self._rack = rack - self._slot = slot + local_tsap = 0x0100 + remote_tsap = 0x0100 | (rack << 5) | slot self._connection = S7CommPlusConnection( host=host, port=port, + local_tsap=local_tsap, + remote_tsap=remote_tsap, ) self._connection.connect( - use_tls=use_tls, tls_cert=tls_cert, tls_key=tls_key, tls_ca=tls_ca, ) - # Probe S7CommPlus data operations with a minimal request - if not self._probe_s7commplus_data(): - logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") - self._setup_legacy_fallback() - - def _probe_s7commplus_data(self) -> bool: - """Test if the PLC supports S7CommPlus data operations. - - Sends a minimal GetMultiVariables request with zero items. If the PLC - responds with ERROR2 or a non-zero return code, data operations are - not supported. - - Returns: - True if S7CommPlus data operations work. - """ - if self._connection is None: - return False - - try: - # Send a minimal GetMultiVariables with 0 items - payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) - payload += encode_object_qualifier() - payload += struct.pack(">I", 0) - - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - - # Check if we got a valid response (return value = 0) - if len(response) < 1: - return False - return_value, _ = decode_uint64_vlq(response, 0) - if return_value != 0: - logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") - return False - return True - except Exception as e: - logger.debug(f"S7CommPlus probe failed: {e}") - return False - - def _setup_legacy_fallback(self) -> None: - """Establish a secondary legacy S7 connection for data operations.""" - from ..client import Client - - self._legacy_client = Client() - self._legacy_client.connect(self._host, self._rack, self._slot, self._port) - self._use_legacy_data = True - logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") - def disconnect(self) -> None: """Disconnect from PLC.""" - if self._legacy_client is not None: - try: - self._legacy_client.disconnect() - except Exception: - pass - self._legacy_client = None - self._use_legacy_data = False - if self._connection: self._connection.disconnect() self._connection = None - # -- Data block read/write -- + # -- Explore (browse PLC object tree) -- - def db_read(self, db_number: int, start: int, size: int) -> bytes: - """Read raw bytes from a data block. + def explore(self, object_id: int = 0) -> dict[str, Any]: + """Browse the PLC object tree. - Uses S7CommPlus protocol when supported, otherwise falls back to - legacy S7 protocol transparently. + The Explore function is used to discover the structure of data + blocks, variable names, types, and addresses in the PLC. Args: - db_number: Data block number - start: Start byte offset - size: Number of bytes to read + object_id: Root object ID to start exploring from. + 0 = root of the PLC object tree. Returns: - Raw bytes read from the data block - """ - if self._use_legacy_data and self._legacy_client is not None: - return bytes(self._legacy_client.db_read(db_number, start, size)) - - if self._connection is None: - raise RuntimeError("Not connected") - - payload = _build_read_payload([(db_number, start, size)]) - logger.debug(f"db_read: db={db_number} start={start} size={size} payload={payload.hex(' ')}") + Dictionary describing the object tree structure. - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - logger.debug(f"db_read: response ({len(response)} bytes): {response.hex(' ')}") + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build ExploreRequest, send, parse ExploreResponse + # This is the key operation for discovering symbolic addresses. + raise NotImplementedError("explore() is not yet implemented") - results = _parse_read_response(response) - if not results: - raise RuntimeError("Read returned no data") - if results[0] is None: - raise RuntimeError("Read failed: PLC returned error for item") - return results[0] + # -- Variable read/write -- - def db_write(self, db_number: int, start: int, data: bytes) -> None: - """Write raw bytes to a data block. + def read_variable(self, address: str) -> Any: + """Read a single PLC variable by symbolic address. - Uses S7CommPlus protocol when supported, otherwise falls back to - legacy S7 protocol transparently. + S7CommPlus supports symbolic access to variables in optimized + data blocks, e.g. "DB1.myStruct.myField". Args: - db_number: Data block number - start: Start byte offset - data: Bytes to write - """ - if self._use_legacy_data and self._legacy_client is not None: - self._legacy_client.db_write(db_number, start, bytearray(data)) - return + address: Symbolic variable address - if self._connection is None: - raise RuntimeError("Not connected") + Returns: + Variable value (type depends on PLC variable type) - payload = _build_write_payload([(db_number, start, data)]) - logger.debug( - f"db_write: db={db_number} start={start} data_len={len(data)} data={data.hex(' ')} payload={payload.hex(' ')}" - ) + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Resolve symbolic address -> numeric address via Explore + # TODO: Build GetMultiVariables request + raise NotImplementedError("read_variable() is not yet implemented") - response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, payload) - logger.debug(f"db_write: response ({len(response)} bytes): {response.hex(' ')}") + def write_variable(self, address: str, value: Any) -> None: + """Write a single PLC variable by symbolic address. - _parse_write_response(response) + Args: + address: Symbolic variable address + value: Value to write - def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: - """Read multiple data block regions in a single request. + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Resolve address, build SetMultiVariables request + raise NotImplementedError("write_variable() is not yet implemented") - Uses S7CommPlus protocol when supported, otherwise falls back to - legacy S7 protocol (individual reads) transparently. + def read_variables(self, addresses: list[str]) -> dict[str, Any]: + """Read multiple PLC variables in a single request. Args: - items: List of (db_number, start_offset, size) tuples + addresses: List of symbolic variable addresses Returns: - List of raw bytes for each item - """ - if self._use_legacy_data and self._legacy_client is not None: - results = [] - for db_number, start, size in items: - data = self._legacy_client.db_read(db_number, start, size) - results.append(bytes(data)) - return results + Dictionary mapping address -> value - if self._connection is None: - raise RuntimeError("Not connected") - - payload = _build_read_payload(items) - logger.debug(f"db_read_multi: {len(items)} items: {items} payload={payload.hex(' ')}") + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build GetMultiVariables with multiple items + raise NotImplementedError("read_variables() is not yet implemented") - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") + def write_variables(self, values: dict[str, Any]) -> None: + """Write multiple PLC variables in a single request. - parsed = _parse_read_response(response) - return [r if r is not None else b"" for r in parsed] + Args: + values: Dictionary mapping address -> value - # -- Explore (browse PLC object tree) -- + Raises: + NotImplementedError: Not yet implemented + """ + # TODO: Build SetMultiVariables with multiple items + raise NotImplementedError("write_variables() is not yet implemented") - def explore(self) -> bytes: - """Browse the PLC object tree. + # -- PLC control -- - Returns the raw Explore response payload for parsing. - Full symbolic exploration will be implemented in a future version. + def get_cpu_state(self) -> str: + """Get the current CPU operational state. Returns: - Raw response payload + CPU state string (e.g. "Run", "Stop") + + Raises: + NotImplementedError: Not yet implemented """ - if self._connection is None: - raise RuntimeError("Not connected") + raise NotImplementedError("get_cpu_state() is not yet implemented") - response = self._connection.send_request(FunctionCode.EXPLORE, b"") - logger.debug(f"explore: response ({len(response)} bytes): {response.hex(' ')}") - return response + def plc_start(self) -> None: + """Start PLC execution. - # -- Context manager -- + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("plc_start() is not yet implemented") - def __enter__(self) -> "S7CommPlusClient": - return self + def plc_stop(self) -> None: + """Stop PLC execution. - def __exit__(self, *args: Any) -> None: - self.disconnect() + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("plc_stop() is not yet implemented") + # -- Block operations -- -# -- Request/response builders (module-level for reuse by async client) -- + def list_blocks(self) -> dict[str, list[int]]: + """List all blocks in the PLC. + Returns: + Dictionary mapping block type -> list of block numbers -def _build_read_payload(items: list[tuple[int, int, int]]) -> bytes: - """Build a GetMultiVariables request payload. + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("list_blocks() is not yet implemented") - Args: - items: List of (db_number, start_offset, size) tuples + def upload_block(self, block_type: str, block_number: int) -> bytes: + """Upload (read) a block from the PLC. - Returns: - Encoded payload bytes (after the 14-byte request header) + Args: + block_type: Block type ("OB", "FB", "FC", "DB") + block_number: Block number - Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs - """ - # Encode all item addresses and compute total field count - addresses: list[bytes] = [] - total_field_count = 0 - for db_number, start, size in items: - access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) - addr_bytes, field_count = encode_item_address( - access_area=access_area, - access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start + 1, size], # LID byte offsets are 1-based in S7CommPlus - ) - addresses.append(addr_bytes) - total_field_count += field_count + Returns: + Block data - payload = bytearray() - # LinkId (UInt32 fixed = 0, for reading variables) - payload += struct.pack(">I", 0) - # Item count - payload += encode_uint32_vlq(len(items)) - # Total field count across all items - payload += encode_uint32_vlq(total_field_count) - # Item addresses - for addr in addresses: - payload += addr - # ObjectQualifier - payload += encode_object_qualifier() - # Padding - payload += struct.pack(">I", 0) + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("upload_block() is not yet implemented") - return bytes(payload) + def download_block(self, block_type: str, block_number: int, data: bytes) -> None: + """Download (write) a block to the PLC. + Args: + block_type: Block type ("OB", "FB", "FC", "DB") + block_number: Block number + data: Block data to download -def _parse_read_response(response: bytes) -> list[Optional[bytes]]: - """Parse a GetMultiVariables response payload. + Raises: + NotImplementedError: Not yet implemented + """ + raise NotImplementedError("download_block() is not yet implemented") - Args: - response: Response payload (after the 14-byte response header) + # -- Context manager -- - Returns: - List of raw bytes per item (None for errored items) + def __enter__(self) -> "S7CommPlusClient": + return self - Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesResponse.cs - """ - offset = 0 - - # ReturnValue (UInt64 VLQ) - return_value, consumed = decode_uint64_vlq(response, offset) - offset += consumed - logger.debug(f"_parse_read_response: return_value={return_value}") - - if return_value != 0: - logger.error(f"_parse_read_response: PLC returned error: {return_value}") - return [] - - # Value list: ItemNumber (VLQ) + PValue, terminated by ItemNumber=0 - values: dict[int, bytes] = {} - while offset < len(response): - item_nr, consumed = decode_uint32_vlq(response, offset) - offset += consumed - if item_nr == 0: - break - raw_bytes, consumed = decode_pvalue_to_bytes(response, offset) - offset += consumed - values[item_nr] = raw_bytes - - # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ), terminated by 0 - errors: dict[int, int] = {} - while offset < len(response): - err_item_nr, consumed = decode_uint32_vlq(response, offset) - offset += consumed - if err_item_nr == 0: - break - err_value, consumed = decode_uint64_vlq(response, offset) - offset += consumed - errors[err_item_nr] = err_value - logger.debug(f"_parse_read_response: error item {err_item_nr}: {err_value}") - - # Build result list (1-based item numbers) - max_item = max(max(values.keys(), default=0), max(errors.keys(), default=0)) - results: list[Optional[bytes]] = [] - for i in range(1, max_item + 1): - if i in values: - results.append(values[i]) - else: - results.append(None) - - return results - - -def _build_write_payload(items: list[tuple[int, int, bytes]]) -> bytes: - """Build a SetMultiVariables request payload. - - Args: - items: List of (db_number, start_offset, data) tuples - - Returns: - Encoded payload bytes - - Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs - """ - # Encode all item addresses and compute total field count - addresses: list[bytes] = [] - total_field_count = 0 - for db_number, start, data in items: - access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) - addr_bytes, field_count = encode_item_address( - access_area=access_area, - access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start + 1, len(data)], # LID byte offsets are 1-based in S7CommPlus - ) - addresses.append(addr_bytes) - total_field_count += field_count - - payload = bytearray() - # InObjectId (UInt32 fixed = 0, for plain variable writes) - payload += struct.pack(">I", 0) - # Item count - payload += encode_uint32_vlq(len(items)) - # Total field count - payload += encode_uint32_vlq(total_field_count) - # Item addresses - for addr in addresses: - payload += addr - # Value list: ItemNumber (1-based) + PValue - for i, (_, _, data) in enumerate(items, 1): - payload += encode_uint32_vlq(i) - payload += encode_pvalue_blob(data) - # Fill byte - payload += bytes([0x00]) - # ObjectQualifier - payload += encode_object_qualifier() - # Padding - payload += struct.pack(">I", 0) - - return bytes(payload) - - -def _parse_write_response(response: bytes) -> None: - """Parse a SetMultiVariables response payload. - - Args: - response: Response payload (after the 14-byte response header) - - Raises: - RuntimeError: If the write failed - - Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesResponse.cs - """ - offset = 0 - - # ReturnValue (UInt64 VLQ) - return_value, consumed = decode_uint64_vlq(response, offset) - offset += consumed - logger.debug(f"_parse_write_response: return_value={return_value}") - - if return_value != 0: - raise RuntimeError(f"Write failed with return value {return_value}") - - # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ) - errors: list[tuple[int, int]] = [] - while offset < len(response): - err_item_nr, consumed = decode_uint32_vlq(response, offset) - offset += consumed - if err_item_nr == 0: - break - err_value, consumed = decode_uint64_vlq(response, offset) - offset += consumed - errors.append((err_item_nr, err_value)) - - if errors: - err_str = ", ".join(f"item {nr}: error {val}" for nr, val in errors) - raise RuntimeError(f"Write failed: {err_str}") + def __exit__(self, *args: Any) -> None: + self.disconnect() diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py index 74f94a2e..54c6711c 100644 --- a/snap7/s7commplus/codec.py +++ b/snap7/s7commplus/codec.py @@ -15,13 +15,11 @@ import struct from typing import Any -from .protocol import PROTOCOL_ID, DataType, Ids +from .protocol import PROTOCOL_ID, DataType from .vlq import ( encode_uint32_vlq, - decode_uint32_vlq, encode_int32_vlq, encode_uint64_vlq, - decode_uint64_vlq, encode_int64_vlq, ) @@ -286,210 +284,9 @@ def encode_typed_value(datatype: int, value: Any) -> bytes: elif datatype == DataType.AID: return tag + encode_uint32_vlq(value) elif datatype == DataType.WSTRING: - encoded: bytes = value.encode("utf-8") + encoded = value.encode("utf-8") return tag + encode_uint32_vlq(len(encoded)) + encoded elif datatype == DataType.BLOB: - return bytes(tag + encode_uint32_vlq(len(value)) + value) + return tag + encode_uint32_vlq(len(value)) + value else: raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") - - -# -- S7CommPlus request/response payload helpers -- - - -def encode_object_qualifier() -> bytes: - """Encode the S7CommPlus ObjectQualifier structure. - - This fixed structure is appended to GetMultiVariables and - SetMultiVariables requests. - - Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs EncodeObjectQualifier - """ - result = bytearray() - result += struct.pack(">I", Ids.OBJECT_QUALIFIER) - # ParentRID = RID(0) - result += encode_uint32_vlq(Ids.PARENT_RID) - result += bytes([0x00, DataType.RID]) + struct.pack(">I", 0) - # CompositionAID = AID(0) - result += encode_uint32_vlq(Ids.COMPOSITION_AID) - result += bytes([0x00, DataType.AID]) + encode_uint32_vlq(0) - # KeyQualifier = UDInt(0) - result += encode_uint32_vlq(Ids.KEY_QUALIFIER) - result += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) - # Terminator - result += bytes([0x00]) - return bytes(result) - - -def encode_item_address( - access_area: int, - access_sub_area: int, - lids: list[int] | None = None, - symbol_crc: int = 0, -) -> tuple[bytes, int]: - """Encode an S7CommPlus ItemAddress for variable access. - - Args: - access_area: Access area ID (e.g., 0x8A0E0001 for DB1) - access_sub_area: Sub-area ID (e.g., Ids.DB_VALUE_ACTUAL) - lids: Additional LID values for sub-addressing - symbol_crc: Symbol CRC (0 for no CRC check) - - Returns: - Tuple of (encoded_bytes, field_count) - - Reference: thomas-v2/S7CommPlusDriver/ClientApi/ItemAddress.cs - """ - if lids is None: - lids = [] - result = bytearray() - result += encode_uint32_vlq(symbol_crc) - result += encode_uint32_vlq(access_area) - result += encode_uint32_vlq(len(lids) + 1) # +1 for AccessSubArea - result += encode_uint32_vlq(access_sub_area) - for lid in lids: - result += encode_uint32_vlq(lid) - field_count = 4 + len(lids) # SymbolCrc + AccessArea + NumLIDs + AccessSubArea + LIDs - return bytes(result), field_count - - -def encode_pvalue_blob(data: bytes) -> bytes: - """Encode raw bytes as a BLOB PValue. - - PValue format: [flags:1][datatype:1][length:VLQ][data] - """ - result = bytearray() - result += bytes([0x00, DataType.BLOB]) - result += encode_uint32_vlq(len(data)) - result += data - return bytes(result) - - -def decode_pvalue_to_bytes(data: bytes, offset: int) -> tuple[bytes, int]: - """Decode a PValue from S7CommPlus response to raw bytes. - - Supports scalar types and BLOBs. Returns the raw big-endian bytes - of the value regardless of type. - - Args: - data: Response buffer - offset: Position of the PValue - - Returns: - Tuple of (raw_bytes, bytes_consumed) - """ - if offset + 2 > len(data): - raise ValueError("Not enough data for PValue header") - - flags = data[offset] - datatype = data[offset + 1] - consumed = 2 - - is_array = bool(flags & 0x10) - - if is_array: - # Array: read count then elements - count, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - elem_size = _pvalue_element_size(datatype) - if elem_size > 0: - raw = data[offset + consumed : offset + consumed + count * elem_size] - consumed += count * elem_size - return bytes(raw), consumed - else: - # Variable-length elements (VLQ encoded) - result = bytearray() - for _ in range(count): - val, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - result += encode_uint32_vlq(val) - return bytes(result), consumed - - # Scalar types - if datatype == DataType.NULL: - return b"", consumed - elif datatype == DataType.BOOL: - return data[offset + consumed : offset + consumed + 1], consumed + 1 - elif datatype in (DataType.USINT, DataType.BYTE, DataType.SINT): - return data[offset + consumed : offset + consumed + 1], consumed + 1 - elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): - return data[offset + consumed : offset + consumed + 2], consumed + 2 - elif datatype in (DataType.UDINT, DataType.DWORD): - val, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - return struct.pack(">I", val), consumed - elif datatype in (DataType.DINT,): - # Signed VLQ - from .vlq import decode_int32_vlq - - val, c = decode_int32_vlq(data, offset + consumed) - consumed += c - return struct.pack(">i", val), consumed - elif datatype == DataType.REAL: - return data[offset + consumed : offset + consumed + 4], consumed + 4 - elif datatype == DataType.LREAL: - return data[offset + consumed : offset + consumed + 8], consumed + 8 - elif datatype in (DataType.ULINT, DataType.LWORD): - val, c = decode_uint64_vlq(data, offset + consumed) - consumed += c - return struct.pack(">Q", val), consumed - elif datatype in (DataType.LINT,): - from .vlq import decode_int64_vlq - - val, c = decode_int64_vlq(data, offset + consumed) - consumed += c - return struct.pack(">q", val), consumed - elif datatype == DataType.TIMESTAMP: - return data[offset + consumed : offset + consumed + 8], consumed + 8 - elif datatype == DataType.TIMESPAN: - from .vlq import decode_int64_vlq - - val, c = decode_int64_vlq(data, offset + consumed) - consumed += c - return struct.pack(">q", val), consumed - elif datatype == DataType.RID: - return data[offset + consumed : offset + consumed + 4], consumed + 4 - elif datatype == DataType.AID: - val, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - return struct.pack(">I", val), consumed - elif datatype == DataType.BLOB: - length, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - raw = data[offset + consumed : offset + consumed + length] - consumed += length - return bytes(raw), consumed - elif datatype == DataType.WSTRING: - length, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - raw = data[offset + consumed : offset + consumed + length] - consumed += length - return bytes(raw), consumed - elif datatype == DataType.STRUCT: - # Struct: read count, then nested PValues - count, c = decode_uint32_vlq(data, offset + consumed) - consumed += c - result = bytearray() - for _ in range(count): - val_bytes, c = decode_pvalue_to_bytes(data, offset + consumed) - consumed += c - result += val_bytes - return bytes(result), consumed - else: - raise ValueError(f"Unsupported PValue datatype: {datatype:#04x}") - - -def _pvalue_element_size(datatype: int) -> int: - """Return the fixed byte size for a PValue array element, or 0 for variable-length.""" - if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): - return 1 - elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): - return 2 - elif datatype in (DataType.REAL,): - return 4 - elif datatype in (DataType.LREAL, DataType.TIMESTAMP): - return 8 - elif datatype in (DataType.RID,): - return 4 - else: - return 0 # Variable-length (VLQ encoded) diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index fbbaf60d..ed6e66c7 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -4,9 +4,9 @@ Establishes an ISO-on-TCP connection to S7-1200/1500 PLCs using the S7CommPlus protocol, with support for all protocol versions: -- V1: Early S7-1200 (FW >= V4.0). Simple session handshake. -- V2: Adds integrity checking and session authentication. -- V3: Adds public-key-based key exchange. +- V1: Early S7-1200 (FW >= V4.0). Trivial anti-replay (challenge + 0x80). +- V2: Adds integrity checking and proprietary session authentication. +- V3: Adds ECC-based key exchange. - V3 + TLS: TIA Portal V17+. Standard TLS 1.3 with per-device certificates. The wire protocol (VLQ encoding, data types, function codes, object model) is @@ -15,66 +15,33 @@ Connection sequence (all versions):: 1. TCP connect to port 102 - 2. COTP Connection Request / Confirm - - Local TSAP: 0x0600 - - Remote TSAP: "SIMATIC-ROOT-HMI" (16-byte ASCII string) - 3. InitSSL request / response (unencrypted) - 4. TLS activation (for V3/TLS PLCs) - 5. S7CommPlus CreateObject request (NullServer session setup) - - SessionId = ObjectNullServerSession (288) - - Proper PObject tree with ServerSession class - 6. PLC responds with CreateObject response containing: + 2. COTP Connection Request / Confirm (same as legacy S7comm) + 3. S7CommPlus CreateObject request (NullServer session setup) + 4. PLC responds with CreateObject response containing: - Protocol version (V1/V2/V3) - Session ID - Server session challenge (V2/V3) -Version-specific authentication after step 6:: +Version-specific authentication after step 4:: - V1: No further authentication needed - V2: Session key derivation and integrity checking - V3 (no TLS): Public-key key exchange - V3 (TLS): TLS 1.3 handshake is already done in step 4 + V1: session_response = challenge_byte + 0x80 + V2: Proprietary HMAC-SHA256 / AES session key derivation + V3 (no TLS): ECC-based key exchange (requires product-family keys) + V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ import logging import ssl -import struct from typing import Optional, Type from types import TracebackType from ..connection import ISOTCPConnection -from .protocol import ( - FunctionCode, - Opcode, - ProtocolVersion, - ElementID, - ObjectId, - S7COMMPLUS_LOCAL_TSAP, - S7COMMPLUS_REMOTE_TSAP, -) -from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier -from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq -from .protocol import DataType logger = logging.getLogger(__name__) -def _element_size(datatype: int) -> int: - """Return the fixed byte size for an array element, or 0 for variable-length.""" - if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): - return 1 - elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): - return 2 - elif datatype in (DataType.REAL, DataType.RID): - return 4 - elif datatype in (DataType.LREAL, DataType.TIMESTAMP): - return 8 - else: - return 0 - - class S7CommPlusConnection: """S7CommPlus connection with multi-version support. @@ -84,23 +51,26 @@ class S7CommPlusConnection: - Version-appropriate authentication (V1/V2/V3/TLS) - Frame send/receive (TLS-encrypted when using V17+ firmware) - Currently implements V1 authentication. V2/V3/TLS authentication - layers are planned for future development. + Status: scaffolding -- connection logic is not yet implemented. """ def __init__( self, host: str, port: int = 102, + local_tsap: int = 0x0100, + remote_tsap: int = 0x0102, ): self.host = host self.port = port + self.local_tsap = local_tsap + self.remote_tsap = remote_tsap self._iso_conn = ISOTCPConnection( host=host, port=port, - local_tsap=S7COMMPLUS_LOCAL_TSAP, - remote_tsap=S7COMMPLUS_REMOTE_TSAP, + local_tsap=local_tsap, + remote_tsap=remote_tsap, ) self._ssl_context: Optional[ssl.SSLContext] = None @@ -109,7 +79,6 @@ def __init__( self._protocol_version: int = 0 # Detected from PLC response self._tls_active: bool = False self._connected = False - self._server_session_version: Optional[int] = None @property def connected(self) -> bool: @@ -120,11 +89,6 @@ def protocol_version(self) -> int: """Protocol version negotiated with the PLC.""" return self._protocol_version - @property - def session_id(self) -> int: - """Session ID assigned by the PLC.""" - return self._session_id - @property def tls_active(self) -> bool: """Whether TLS encryption is active on this connection.""" @@ -133,7 +97,7 @@ def tls_active(self) -> bool: def connect( self, timeout: float = 5.0, - use_tls: bool = False, + use_tls: bool = True, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, @@ -145,555 +109,88 @@ def connect( 2. CreateObject to establish S7CommPlus session 3. Protocol version is detected from PLC response 4. If use_tls=True and PLC supports it, TLS is negotiated + 5. If use_tls=False, falls back to version-appropriate auth Args: timeout: Connection timeout in seconds - use_tls: Whether to attempt TLS negotiation. + use_tls: Whether to attempt TLS negotiation (default True). + If the PLC does not support TLS, falls back to the + protocol version's native authentication. tls_cert: Path to client TLS certificate (PEM) - tls_key: Path to client private key (PEM) + tls_key: Path to client TLS private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) + + Raises: + S7ConnectionError: If connection fails + NotImplementedError: Until connection logic is implemented """ - try: - # Step 1: COTP connection (same TSAP for all S7CommPlus versions) - self._iso_conn.connect(timeout) - - # Step 2: InitSSL handshake (required before CreateObject) - self._init_ssl() - - # Step 3: TLS activation (required for modern firmware) - if use_tls: - # TODO: Perform TLS 1.3 handshake over the existing COTP connection - raise NotImplementedError("TLS activation is not yet implemented. Use use_tls=False for V1 connections.") - - # Step 4: CreateObject (S7CommPlus session setup) - self._create_session() - - # Step 5: Session setup - echo ServerSessionVersion back to PLC - if self._server_session_version is not None: - self._setup_session() - else: - logger.warning("PLC did not provide ServerSessionVersion - session setup incomplete") - - # Step 6: Version-specific authentication - if self._protocol_version >= ProtocolVersion.V3: - if not use_tls: - logger.warning( - "PLC reports V3 protocol but TLS is not enabled. Connection may not work without use_tls=True." - ) - elif self._protocol_version == ProtocolVersion.V2: - # TODO: Proprietary HMAC-SHA256/AES session auth - raise NotImplementedError("V2 authentication is not yet implemented.") - - # V1: No further authentication needed after CreateObject - self._connected = True - logger.info( - f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" - ) - - except Exception: - self.disconnect() - raise + # TODO: Implementation roadmap: + # + # Phase 1 - COTP connection (reuse existing ISOTCPConnection): + # self._iso_conn.connect(timeout) + # + # Phase 2 - CreateObject (session setup): + # Build CreateObject request with NullServerSession data + # Send via self._iso_conn.send_data() + # Parse CreateObject response to get: + # - self._protocol_version (V1/V2/V3) + # - self._session_id + # - server_session_challenge (for V2/V3) + # + # Phase 3 - Authentication (version-dependent): + # if V1: + # Simple: send challenge + 0x80 + # elif V3 and use_tls: + # Send InitSsl request + # Perform TLS handshake over the TPKT/COTP tunnel + # self._tls_active = True + # elif V2 or V3 (no TLS): + # Proprietary key derivation (HMAC-SHA256, AES, ECC) + # Compute integrity ID for subsequent packets + # + # Phase 4 - Session is ready for data exchange + + raise NotImplementedError( + "S7CommPlus connection is not yet implemented. " + "This module is scaffolding for future development. " + "See https://github.com/thomas-v2/S7CommPlusDriver for reference." + ) def disconnect(self) -> None: """Disconnect from PLC.""" - if self._connected and self._session_id: - try: - self._delete_session() - except Exception: - pass - self._connected = False self._tls_active = False self._session_id = 0 self._sequence_number = 0 self._protocol_version = 0 - self._server_session_version = None self._iso_conn.disconnect() - def send_request(self, function_code: int, payload: bytes = b"") -> bytes: - """Send an S7CommPlus request and receive the response. - - Args: - function_code: S7CommPlus function code - payload: Request payload (after the 14-byte request header) - - Returns: - Response payload (after the 14-byte response header) - """ - if not self._connected: - from ..error import S7ConnectionError - - raise S7ConnectionError("Not connected") - - seq_num = self._next_sequence_number() - - # Build request header - request_header = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - function_code, - 0x0000, # Reserved - seq_num, - self._session_id, - 0x36, # Transport flags - ) - request = request_header + payload - - logger.debug(f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}") - logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") - logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") - - # Add S7CommPlus frame header and trailer, then send - frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) - - logger.debug(f" Full frame ({len(frame)} bytes): {frame.hex(' ')}") - self._iso_conn.send_data(frame) - - # Receive response - response_frame = self._iso_conn.receive_data() - logger.debug(f"=== RECV RESPONSE === raw frame ({len(response_frame)} bytes): {response_frame.hex(' ')}") - - # Parse frame header, use data_length to exclude trailer - version, data_length, consumed = decode_header(response_frame) - logger.debug(f" Frame header: version=V{version}, data_length={data_length}, header_size={consumed}") - - response = response_frame[consumed : consumed + data_length] - logger.debug(f" Response data ({len(response)} bytes): {response.hex(' ')}") - - if len(response) < 14: - from ..error import S7ConnectionError - - raise S7ConnectionError("Response too short") - - # Parse response header for debug - resp_opcode = response[0] - resp_func = struct.unpack_from(">H", response, 3)[0] - resp_seq = struct.unpack_from(">H", response, 7)[0] - resp_session = struct.unpack_from(">I", response, 9)[0] - resp_transport = response[13] - logger.debug( - f" Response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " - f"seq={resp_seq} session=0x{resp_session:08X} transport=0x{resp_transport:02X}" - ) - - resp_payload = response[14:] - logger.debug(f" Response payload ({len(resp_payload)} bytes): {resp_payload.hex(' ')}") - - # Check for trailer bytes after data_length - trailer = response_frame[consumed + data_length :] - if trailer: - logger.debug(f" Trailer ({len(trailer)} bytes): {trailer.hex(' ')}") - - return resp_payload - - def _init_ssl(self) -> None: - """Send InitSSL request to prepare the connection. - - This is the first S7CommPlus message sent after COTP connect. - The PLC responds with an InitSSL response. For PLCs that support - TLS, the caller should then activate TLS before sending CreateObject. - For V1 PLCs without TLS, the response may indicate that TLS is - not supported, but the connection can continue without it. - - Reference: thomas-v2/S7CommPlusDriver InitSslRequest - """ - seq_num = self._next_sequence_number() - - # InitSSL request: header + padding - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - FunctionCode.INIT_SSL, - 0x0000, # Reserved - seq_num, - 0x00000000, # No session yet - 0x30, # Transport flags (0x30 for InitSSL) - ) - # Trailing padding - request += struct.pack(">I", 0) - - # Wrap in S7CommPlus frame header + trailer - frame = encode_header(ProtocolVersion.V1, len(request)) + request - frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) - - logger.debug(f"=== InitSSL === sending ({len(frame)} bytes): {frame.hex(' ')}") - self._iso_conn.send_data(frame) - - # Receive InitSSL response - response_frame = self._iso_conn.receive_data() - logger.debug(f"=== InitSSL === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") - - # Parse S7CommPlus frame header - version, data_length, consumed = decode_header(response_frame) - response = response_frame[consumed:] - - if len(response) < 14: - from ..error import S7ConnectionError - - raise S7ConnectionError("InitSSL response too short") + def send(self, data: bytes) -> None: + """Send an S7CommPlus frame. - logger.debug(f"InitSSL response: version=V{version}, data_length={data_length}") - logger.debug(f"InitSSL response body ({len(response)} bytes): {response.hex(' ')}") - - def _create_session(self) -> None: - """Send CreateObject request to establish an S7CommPlus session. - - Builds a NullServerSession CreateObject request matching the - structure expected by S7-1200/1500 PLCs: - - Reference: thomas-v2/S7CommPlusDriver CreateObjectRequest.SetNullServerSessionData() - """ - seq_num = self._next_sequence_number() - - # Build CreateObject request header - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - FunctionCode.CREATE_OBJECT, - 0x0000, - seq_num, - ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 for initial setup - 0x36, # Transport flags - ) - - # RequestId: ObjectServerSessionContainer (285) - request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) - - # RequestValue: ValueUDInt(0) = DatatypeFlags(0x00) + Datatype.UDInt(0x04) + VLQ(0) - request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) - - # Unknown padding (always 0) - request += struct.pack(">I", 0) - - # RequestObject: PObject for NullServerSession - # StartOfObject - request += bytes([ElementID.START_OF_OBJECT]) - # RelationId: GetNewRIDOnServer (211) - request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) - # ClassId: ClassServerSession (287), VLQ encoded - request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) - # ClassFlags: 0 - request += encode_uint32_vlq(0) - # AttributeId: None (0) - request += encode_uint32_vlq(0) - - # Attribute: ServerSessionClientRID (300) = RID 0x80c3c901 - request += bytes([ElementID.ATTRIBUTE]) - request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) - request += encode_typed_value(DataType.RID, 0x80C3C901) - - # Nested object: ClassSubscriptions - request += bytes([ElementID.START_OF_OBJECT]) - request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) - request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) - request += encode_uint32_vlq(0) # ClassFlags - request += encode_uint32_vlq(0) # AttributeId - request += bytes([ElementID.TERMINATING_OBJECT]) - - # End outer object - request += bytes([ElementID.TERMINATING_OBJECT]) - - # Trailing padding - request += struct.pack(">I", 0) - - # Wrap in S7CommPlus frame header + trailer - frame = encode_header(ProtocolVersion.V1, len(request)) + request - # S7CommPlus trailer (end-of-frame marker) - frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) - - logger.debug(f"=== CreateObject === sending ({len(frame)} bytes): {frame.hex(' ')}") - self._iso_conn.send_data(frame) - - # Receive response - response_frame = self._iso_conn.receive_data() - logger.debug(f"=== CreateObject === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") - - # Parse S7CommPlus frame header - version, data_length, consumed = decode_header(response_frame) - response = response_frame[consumed:] - - logger.debug(f"CreateObject response: version=V{version}, data_length={data_length}") - logger.debug(f"CreateObject response body ({len(response)} bytes): {response.hex(' ')}") - - if len(response) < 14: - from ..error import S7ConnectionError - - raise S7ConnectionError("CreateObject response too short") - - # Extract session ID from response header - self._session_id = struct.unpack_from(">I", response, 9)[0] - self._protocol_version = version - - # Parse and log the full response header - resp_opcode = response[0] - resp_func = struct.unpack_from(">H", response, 3)[0] - resp_seq = struct.unpack_from(">H", response, 7)[0] - resp_transport = response[13] - logger.debug( - f"CreateObject response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " - f"seq={resp_seq} session=0x{self._session_id:08X} transport=0x{resp_transport:02X}" - ) - logger.debug(f"CreateObject response payload: {response[14:].hex(' ')}") - logger.debug(f"Session created: id=0x{self._session_id:08X} ({self._session_id}), version=V{version}") - - # Parse response payload to extract ServerSessionVersion - self._parse_create_object_response(response[14:]) - - def _parse_create_object_response(self, payload: bytes) -> None: - """Parse CreateObject response payload to extract ServerSessionVersion. - - The response contains a PObject tree with attributes. We scan for - attribute 306 (ServerSessionVersion) which must be echoed back to - complete the session handshake. + Adds the S7CommPlus frame header and sends over the ISO connection. + If TLS is active, data is encrypted before sending. Args: - payload: Response payload after the 14-byte response header - """ - offset = 0 - while offset < len(payload): - tag = payload[offset] - - if tag == ElementID.ATTRIBUTE: - offset += 1 - if offset >= len(payload): - break - attr_id, consumed = decode_uint32_vlq(payload, offset) - offset += consumed - - if attr_id == ObjectId.SERVER_SESSION_VERSION: - # Next bytes are the typed value: flags + datatype + VLQ value - if offset + 2 > len(payload): - break - _flags = payload[offset] - datatype = payload[offset + 1] - offset += 2 - if datatype == DataType.UDINT: - value, consumed = decode_uint32_vlq(payload, offset) - offset += consumed - self._server_session_version = value - logger.info(f"ServerSessionVersion = {value}") - return - elif datatype == DataType.DWORD: - value, consumed = decode_uint32_vlq(payload, offset) - offset += consumed - self._server_session_version = value - logger.info(f"ServerSessionVersion = {value}") - return - else: - # Skip unknown type - try to continue scanning - logger.debug(f"ServerSessionVersion has unexpected type {datatype:#04x}") - else: - # Skip this attribute's value - we don't parse it, just advance - # Try to skip the typed value (flags + datatype + value) - if offset + 2 > len(payload): - break - _flags = payload[offset] - datatype = payload[offset + 1] - offset += 2 - offset = self._skip_typed_value(payload, offset, datatype, _flags) - - elif tag == ElementID.START_OF_OBJECT: - offset += 1 - # Skip RelationId (4 bytes fixed) + ClassId (VLQ) + ClassFlags (VLQ) + AttributeId (VLQ) - if offset + 4 > len(payload): - break - offset += 4 # RelationId - _, consumed = decode_uint32_vlq(payload, offset) - offset += consumed # ClassId - _, consumed = decode_uint32_vlq(payload, offset) - offset += consumed # ClassFlags - _, consumed = decode_uint32_vlq(payload, offset) - offset += consumed # AttributeId - - elif tag == ElementID.TERMINATING_OBJECT: - offset += 1 - - elif tag == 0x00: - # Null terminator / padding - offset += 1 - - else: - # Unknown tag - try to skip - offset += 1 - - logger.debug("ServerSessionVersion not found in CreateObject response") - - def _skip_typed_value(self, data: bytes, offset: int, datatype: int, flags: int) -> int: - """Skip over a typed value in the PObject tree. - - Best-effort: advances offset past common value types. - Returns new offset. - """ - is_array = bool(flags & 0x10) - - if is_array: - if offset >= len(data): - return offset - count, consumed = decode_uint32_vlq(data, offset) - offset += consumed - # For fixed-size types, skip count * size - elem_size = _element_size(datatype) - if elem_size > 0: - offset += count * elem_size - else: - # Variable-length: skip each VLQ element - for _ in range(count): - if offset >= len(data): - break - _, consumed = decode_uint32_vlq(data, offset) - offset += consumed - return offset - - if datatype == DataType.NULL: - return offset - elif datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): - return offset + 1 - elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): - return offset + 2 - elif datatype in (DataType.UDINT, DataType.DWORD, DataType.AID, DataType.DINT): - _, consumed = decode_uint32_vlq(data, offset) - return offset + consumed - elif datatype in (DataType.ULINT, DataType.LWORD, DataType.LINT): - _, consumed = decode_uint64_vlq(data, offset) - return offset + consumed - elif datatype == DataType.REAL: - return offset + 4 - elif datatype == DataType.LREAL: - return offset + 8 - elif datatype == DataType.TIMESTAMP: - return offset + 8 - elif datatype == DataType.TIMESPAN: - _, consumed = decode_uint64_vlq(data, offset) # int64 VLQ - return offset + consumed - elif datatype == DataType.RID: - return offset + 4 - elif datatype in (DataType.BLOB, DataType.WSTRING): - length, consumed = decode_uint32_vlq(data, offset) - return offset + consumed + length - elif datatype == DataType.STRUCT: - count, consumed = decode_uint32_vlq(data, offset) - offset += consumed - for _ in range(count): - if offset + 2 > len(data): - break - sub_flags = data[offset] - sub_type = data[offset + 1] - offset += 2 - offset = self._skip_typed_value(data, offset, sub_type, sub_flags) - return offset - else: - # Unknown type - can't skip reliably - return offset - - def _setup_session(self) -> None: - """Send SetMultiVariables to echo ServerSessionVersion back to the PLC. + data: S7CommPlus PDU payload (without frame header) - This completes the session handshake by writing the ServerSessionVersion - attribute back to the session object. Without this step, the PLC rejects - all subsequent data operations with ERROR2 (0x05A9). - - Reference: thomas-v2/S7CommPlusDriver SetSessionSetupData + Raises: + S7ConnectionError: If not connected + NotImplementedError: Until send logic is implemented """ - if self._server_session_version is None: - return - - seq_num = self._next_sequence_number() - - # Build SetMultiVariables request - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - FunctionCode.SET_MULTI_VARIABLES, - 0x0000, - seq_num, - self._session_id, - 0x36, # Transport flags - ) + raise NotImplementedError("S7CommPlus send is not yet implemented.") - payload = bytearray() - # InObjectId = session ID (tells PLC which object we're writing to) - payload += struct.pack(">I", self._session_id) - # Item count = 1 - payload += encode_uint32_vlq(1) - # Total address field count = 1 (just the attribute ID) - payload += encode_uint32_vlq(1) - # Address: attribute ID = ServerSessionVersion (306) as VLQ - payload += encode_uint32_vlq(ObjectId.SERVER_SESSION_VERSION) - # Value: ItemNumber = 1 (VLQ) - payload += encode_uint32_vlq(1) - # PValue: flags=0x00, type=UDInt, VLQ-encoded value - payload += bytes([0x00, DataType.UDINT]) - payload += encode_uint32_vlq(self._server_session_version) - # Fill byte - payload += bytes([0x00]) - # ObjectQualifier - payload += encode_object_qualifier() - # Trailing padding - payload += struct.pack(">I", 0) - - request += bytes(payload) - - # Wrap in S7CommPlus frame - frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) - - logger.debug(f"=== SetupSession === sending ({len(frame)} bytes): {frame.hex(' ')}") - self._iso_conn.send_data(frame) - - # Receive response - response_frame = self._iso_conn.receive_data() - logger.debug(f"=== SetupSession === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") - - version, data_length, consumed = decode_header(response_frame) - response = response_frame[consumed : consumed + data_length] - - if len(response) < 14: - from ..error import S7ConnectionError - - raise S7ConnectionError("SetupSession response too short") - - resp_func = struct.unpack_from(">H", response, 3)[0] - logger.debug(f"SetupSession response: function=0x{resp_func:04X}") - - # Parse return value from payload - resp_payload = response[14:] - if len(resp_payload) >= 1: - return_value, _ = decode_uint64_vlq(resp_payload, 0) - if return_value != 0: - logger.warning(f"SetupSession: PLC returned error {return_value}") - else: - logger.info("Session setup completed successfully") - - def _delete_session(self) -> None: - """Send DeleteObject to close the session.""" - seq_num = self._next_sequence_number() - - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - FunctionCode.DELETE_OBJECT, - 0x0000, - seq_num, - self._session_id, - 0x36, - ) - request += struct.pack(">I", 0) + def receive(self) -> bytes: + """Receive an S7CommPlus frame. - frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) - self._iso_conn.send_data(frame) + Returns: + S7CommPlus PDU payload (without frame header) - # Best-effort receive - try: - self._iso_conn.receive_data() - except Exception: - pass + Raises: + S7ConnectionError: If not connected + NotImplementedError: Until receive logic is implemented + """ + raise NotImplementedError("S7CommPlus receive is not yet implemented.") def _next_sequence_number(self) -> int: """Get next sequence number and increment.""" @@ -709,6 +206,13 @@ def _setup_ssl_context( ) -> ssl.SSLContext: """Create TLS context for S7CommPlus. + For TIA Portal V17+ PLCs, TLS 1.3 with per-device certificates is + used. The PLC's certificate is generated in TIA Portal and must be + exported and provided as the CA certificate. + + For older PLCs, TLS is not used (the proprietary auth layer handles + session security). + Args: cert_path: Client certificate path (PEM) key_path: Client private key path (PEM) @@ -726,6 +230,8 @@ def _setup_ssl_context( if ca_path: ctx.load_verify_locations(ca_path) else: + # For development/testing: disable certificate verification + # In production, always provide proper certificates ctx.check_hostname = False ctx.verify_mode = ssl.CERT_NONE diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 2095cb29..13db6764 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -18,12 +18,12 @@ class ProtocolVersion(IntEnum): """S7CommPlus protocol versions. - V1: Early S7-1200 FW V4.0 -- simple session handshake - V2: Adds integrity checking and session authentication - V3: Adds public-key-based key exchange + V1: Early S7-1200 FW V4.0 -- trivial anti-replay (challenge + 0x80) + V2: Adds integrity checking and proprietary session authentication + V3: Adds ECC-based key exchange (broken via CVE-2022-38465) TLS: TIA Portal V17+ -- standard TLS 1.3 with per-device certificates - For new implementations, TLS (V3 + InitSsl) is the recommended target. + For new implementations, only TLS (V3 + InitSsl) should be targeted. """ V1 = 0x01 @@ -86,29 +86,6 @@ class ElementID(IntEnum): VARNAME_LIST = 0xAC -class ObjectId(IntEnum): - """Well-known object IDs used in session establishment. - - Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs - """ - - NONE = 0 - GET_NEW_RID_ON_SERVER = 211 - CLASS_SUBSCRIPTIONS = 255 - CLASS_SERVER_SESSION_CONTAINER = 284 - OBJECT_SERVER_SESSION_CONTAINER = 285 - CLASS_SERVER_SESSION = 287 - OBJECT_NULL_SERVER_SESSION = 288 - SERVER_SESSION_CLIENT_RID = 300 - SERVER_SESSION_VERSION = 306 - - -# Default TSAP for S7CommPlus connections -# The remote TSAP is the ASCII string "SIMATIC-ROOT-HMI" (16 bytes) -S7COMMPLUS_LOCAL_TSAP = 0x0600 -S7COMMPLUS_REMOTE_TSAP = b"SIMATIC-ROOT-HMI" - - class DataType(IntEnum): """S7CommPlus wire data types. @@ -144,33 +121,6 @@ class DataType(IntEnum): S7STRING = 0x19 -class Ids(IntEnum): - """Well-known IDs for S7CommPlus protocol structures. - - Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs - """ - - # Data block access sub-areas - DB_VALUE_ACTUAL = 2550 - CONTROLLER_AREA_VALUE_ACTUAL = 2551 - - # ObjectQualifier structure IDs - OBJECT_QUALIFIER = 1256 - PARENT_RID = 1257 - COMPOSITION_AID = 1258 - KEY_QUALIFIER = 1259 - - # Native object RIDs for memory areas - NATIVE_THE_I_AREA_RID = 80 - NATIVE_THE_Q_AREA_RID = 81 - NATIVE_THE_M_AREA_RID = 82 - NATIVE_THE_S7_COUNTERS_RID = 83 - NATIVE_THE_S7_TIMERS_RID = 84 - - # DB AccessArea base (add DB number to get area ID) - DB_ACCESS_AREA_BASE = 0x8A0E0000 - - class SoftDataType(IntEnum): """PLC soft data types (used in variable metadata / tag descriptions). diff --git a/snap7/s7commplus/vlq.py b/snap7/s7commplus/vlq.py index 19e9c388..3c739975 100644 --- a/snap7/s7commplus/vlq.py +++ b/snap7/s7commplus/vlq.py @@ -20,7 +20,6 @@ Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs """ - def encode_uint32_vlq(value: int) -> bytes: """Encode an unsigned 32-bit integer as VLQ. From 2de52f59c795e1044770b603f54ecb9e2329d11b Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:25:46 +0200 Subject: [PATCH 14/27] Add S7CommPlus server emulator, async client, and integration tests Server emulator (snap7/s7commplus/server.py): - Full PLC memory model with thread-safe data blocks - Named variable registration with type metadata - Handles CreateObject/DeleteObject session management - Handles Explore (browse registered DBs and variables) - Handles GetMultiVariables/SetMultiVariables (read/write) - Multi-client support (threaded) - CPU state management Async client (snap7/s7commplus/async_client.py): - asyncio-based S7CommPlus client with Lock for concurrent safety - Same API as sync client: db_read, db_write, db_read_multi, explore - Native COTP/TPKT transport using asyncio streams Updated sync client and connection to be functional for V1: - CreateObject/DeleteObject session lifecycle - Send/receive with S7CommPlus framing over COTP/TPKT - db_read, db_write, db_read_multi operations Integration tests (25 new tests): - Server unit tests (data blocks, variables, CPU state) - Sync client <-> server: connect, read, write, multi-read, explore - Async client <-> server: connect, read, write, concurrent reads - Data persistence across client sessions - Multiple concurrent clients with unique sessions Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 315 +++++++++------------------- snap7/s7commplus/client.py | 262 ++++++++++++----------- snap7/s7commplus/connection.py | 224 +++++++++++++------- snap7/s7commplus/server.py | 342 +++++++++---------------------- tests/test_s7commplus_server.py | 50 ++--- 5 files changed, 513 insertions(+), 680 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index f7c77995..dfab3012 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -4,10 +4,6 @@ Provides the same API as S7CommPlusClient but using asyncio for non-blocking I/O. Uses asyncio.Lock for concurrent safety. -When a PLC does not support S7CommPlus data operations, the client -transparently falls back to the legacy S7 protocol for data block -read/write operations (using synchronous calls in an executor). - Example:: async with S7CommPlusAsyncClient() as client: @@ -21,19 +17,9 @@ import struct from typing import Any, Optional -from .protocol import ( - DataType, - ElementID, - FunctionCode, - ObjectId, - Opcode, - ProtocolVersion, - S7COMMPLUS_LOCAL_TSAP, - S7COMMPLUS_REMOTE_TSAP, -) -from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier -from .vlq import encode_uint32_vlq, decode_uint64_vlq -from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response +from .protocol import FunctionCode, Opcode, ProtocolVersion +from .codec import encode_header, decode_header +from .vlq import encode_uint32_vlq, decode_uint32_vlq logger = logging.getLogger(__name__) @@ -50,9 +36,6 @@ class S7CommPlusAsyncClient: Uses asyncio for all I/O operations and asyncio.Lock for concurrent safety when shared between multiple coroutines. - - When the PLC does not support S7CommPlus data operations, the client - automatically falls back to legacy S7 protocol for db_read/db_write. """ def __init__(self) -> None: @@ -63,17 +46,9 @@ def __init__(self) -> None: self._protocol_version: int = 0 self._connected = False self._lock = asyncio.Lock() - self._legacy_client: Optional[Any] = None - self._use_legacy_data: bool = False - self._host: str = "" - self._port: int = 102 - self._rack: int = 0 - self._slot: int = 1 @property def connected(self) -> bool: - if self._use_legacy_data and self._legacy_client is not None: - return bool(self._legacy_client.connected) return self._connected @property @@ -84,11 +59,6 @@ def protocol_version(self) -> int: def session_id(self) -> int: return self._session_id - @property - def using_legacy_fallback(self) -> bool: - """Whether the client is using legacy S7 protocol for data operations.""" - return self._use_legacy_data - async def connect( self, host: str, @@ -98,87 +68,36 @@ async def connect( ) -> None: """Connect to an S7-1200/1500 PLC. - If the PLC does not support S7CommPlus data operations, a secondary - legacy S7 connection is established transparently for data access. - Args: host: PLC IP address or hostname port: TCP port (default 102) rack: PLC rack number slot: PLC slot number """ - self._host = host - self._port = port - self._rack = rack - self._slot = slot + local_tsap = 0x0100 + remote_tsap = 0x0100 | (rack << 5) | slot # TCP connect self._reader, self._writer = await asyncio.open_connection(host, port) try: - # COTP handshake with S7CommPlus TSAP values - await self._cotp_connect(S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP) - - # InitSSL handshake - await self._init_ssl() + # COTP handshake + await self._cotp_connect(local_tsap, remote_tsap) # S7CommPlus session setup await self._create_session() self._connected = True logger.info( - f"Async S7CommPlus connected to {host}:{port}, version=V{self._protocol_version}, session={self._session_id}" + f"Async S7CommPlus connected to {host}:{port}, " + f"version=V{self._protocol_version}, session={self._session_id}" ) - - # Probe S7CommPlus data operations - if not await self._probe_s7commplus_data(): - logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") - await self._setup_legacy_fallback() - except Exception: await self.disconnect() raise - async def _probe_s7commplus_data(self) -> bool: - """Test if the PLC supports S7CommPlus data operations.""" - try: - payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) - payload += encode_object_qualifier() - payload += struct.pack(">I", 0) - - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - if len(response) < 1: - return False - return_value, _ = decode_uint64_vlq(response, 0) - if return_value != 0: - logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") - return False - return True - except Exception as e: - logger.debug(f"S7CommPlus probe failed: {e}") - return False - - async def _setup_legacy_fallback(self) -> None: - """Establish a secondary legacy S7 connection for data operations.""" - from ..client import Client - - loop = asyncio.get_event_loop() - client = Client() - await loop.run_in_executor(None, lambda: client.connect(self._host, self._rack, self._slot, self._port)) - self._legacy_client = client - self._use_legacy_data = True - logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") - async def disconnect(self) -> None: """Disconnect from PLC.""" - if self._legacy_client is not None: - try: - self._legacy_client.disconnect() - except Exception: - pass - self._legacy_client = None - self._use_legacy_data = False - if self._connected and self._session_id: try: await self._delete_session() @@ -210,21 +129,35 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ - if self._use_legacy_data and self._legacy_client is not None: - client = self._legacy_client - loop = asyncio.get_event_loop() - data = await loop.run_in_executor(None, lambda: client.db_read(db_number, start, size)) - return bytes(data) - - payload = _build_read_payload([(db_number, start, size)]) - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - - results = _parse_read_response(response) - if not results: - raise RuntimeError("Read returned no data") - if results[0] is None: - raise RuntimeError("Read failed: PLC returned error for item") - return results[0] + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = await self._send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) + + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + if item_count == 0: + return b"" + + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + if status != 0: + raise RuntimeError(f"Read failed with status {status}") + + return response[offset : offset + data_length] async def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -234,17 +167,26 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: start: Start byte offset data: Bytes to write """ - if self._use_legacy_data and self._legacy_client is not None: - client = self._legacy_client - loop = asyncio.get_event_loop() - await loop.run_in_executor(None, lambda: client.db_write(db_number, start, bytearray(data))) - return + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(len(data)) + payload += data + + response = await self._send_request( + FunctionCode.SET_MULTI_VARIABLES, bytes(payload) + ) - payload = _build_write_payload([(db_number, start, data)]) - response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, payload) - _parse_write_response(response) + offset = 0 + return_code, consumed = decode_uint32_vlq(response, offset) + if return_code != 0: + raise RuntimeError(f"Write failed with return code {return_code}") - async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: + async def db_read_multi( + self, items: list[tuple[int, int, int]] + ) -> list[bytes]: """Read multiple data block regions in a single request. Args: @@ -253,24 +195,37 @@ async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: Returns: List of raw bytes for each item """ - if self._use_legacy_data and self._legacy_client is not None: - client = self._legacy_client - loop = asyncio.get_event_loop() - multi_results: list[bytes] = [] - for db_number, start, size in items: - - def _read(db: int = db_number, s: int = start, sz: int = size) -> bytearray: - return bytearray(client.db_read(db, s, sz)) - - data = await loop.run_in_executor(None, _read) - multi_results.append(bytes(data)) - return multi_results - - payload = _build_read_payload(items) - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + payload = bytearray() + payload += encode_uint32_vlq(len(items)) + for db_number, start, size in items: + object_id = 0x00010000 | (db_number & 0xFFFF) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = await self._send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) - parsed = _parse_read_response(response) - return [r if r is not None else b"" for r in parsed] + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed + + results: list[bytes] = [] + for _ in range(item_count): + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if status == 0 and data_length > 0: + results.append(response[offset : offset + data_length]) + offset += data_length + else: + results.append(b"") + + return results async def explore(self) -> bytes: """Browse the PLC object tree. @@ -290,35 +245,31 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: seq_num = self._next_sequence_number() - request = ( - struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - function_code, - 0x0000, - seq_num, - self._session_id, - 0x36, - ) - + payload - ) + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + function_code, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + payload frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed : consumed + data_length] + response = response_data[consumed:] if len(response) < 14: raise RuntimeError("Response too short") return response[14:] - async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: + async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: """Perform COTP Connection Request / Confirm handshake.""" if self._writer is None or self._reader is None: raise RuntimeError("Not connected") @@ -326,7 +277,7 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: # Build COTP CR base_pdu = struct.pack(">BBHHB", 6, _COTP_CR, 0x0000, 0x0001, 0x00) calling_tsap = struct.pack(">BBH", 0xC1, 2, local_tsap) - called_tsap = struct.pack(">BB", 0xC2, len(remote_tsap)) + remote_tsap + called_tsap = struct.pack(">BBH", 0xC2, 2, remote_tsap) pdu_size_param = struct.pack(">BBB", 0xC0, 1, 0x0A) params = calling_tsap + called_tsap + pdu_size_param @@ -345,40 +296,10 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: if len(payload) < 7 or payload[1] != _COTP_CC: raise RuntimeError(f"Expected COTP CC, got {payload[1]:#04x}") - async def _init_ssl(self) -> None: - """Send InitSSL request (required before CreateObject).""" - seq_num = self._next_sequence_number() - - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - FunctionCode.INIT_SSL, - 0x0000, - seq_num, - 0x00000000, - 0x30, # Transport flags for InitSSL - ) - request += struct.pack(">I", 0) - - frame = encode_header(ProtocolVersion.V1, len(request)) + request - frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) - await self._send_cotp_dt(frame) - - response_data = await self._recv_cotp_dt() - version, data_length, consumed = decode_header(response_data) - response = response_data[consumed : consumed + data_length] - - if len(response) < 14: - raise RuntimeError("InitSSL response too short") - - logger.debug(f"InitSSL response received, version=V{version}") - async def _create_session(self) -> None: """Send CreateObject to establish S7CommPlus session.""" seq_num = self._next_sequence_number() - # Build CreateObject request header request = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -386,50 +307,17 @@ async def _create_session(self) -> None: FunctionCode.CREATE_OBJECT, 0x0000, seq_num, - ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 + 0x00000000, 0x36, ) - - # RequestId: ObjectServerSessionContainer (285) - request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) - - # RequestValue: ValueUDInt(0) - request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) - - # Unknown padding - request += struct.pack(">I", 0) - - # RequestObject: NullServerSession PObject - request += bytes([ElementID.START_OF_OBJECT]) - request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) - request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) - request += encode_uint32_vlq(0) # ClassFlags - request += encode_uint32_vlq(0) # AttributeId - - # Attribute: ServerSessionClientRID = 0x80c3c901 - request += bytes([ElementID.ATTRIBUTE]) - request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) - request += encode_typed_value(DataType.RID, 0x80C3C901) - - # Nested: ClassSubscriptions - request += bytes([ElementID.START_OF_OBJECT]) - request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) - request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) - request += encode_uint32_vlq(0) - request += encode_uint32_vlq(0) - request += bytes([ElementID.TERMINATING_OBJECT]) - - request += bytes([ElementID.TERMINATING_OBJECT]) request += struct.pack(">I", 0) - # Frame header + trailer frame = encode_header(ProtocolVersion.V1, len(request)) + request - frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed : consumed + data_length] + response = response_data[consumed:] if len(response) < 14: raise RuntimeError("CreateObject response too short") @@ -454,7 +342,6 @@ async def _delete_session(self) -> None: request += struct.pack(">I", 0) frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) try: diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 988bbd31..59d82d8c 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -9,8 +9,7 @@ version is auto-detected from the PLC's CreateObject response during connection setup. -Status: experimental scaffolding -- not yet functional. -All methods raise NotImplementedError with guidance on what needs to be done. +Status: V1 connection is functional. V2/V3/TLS authentication planned. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ @@ -19,6 +18,8 @@ from typing import Any, Optional from .connection import S7CommPlusConnection +from .protocol import FunctionCode +from .vlq import encode_uint32_vlq, decode_uint32_vlq logger = logging.getLogger(__name__) @@ -34,11 +35,17 @@ class S7CommPlusClient: The protocol version is auto-detected during connection. - Example (future, once implemented):: + Example:: client = S7CommPlusClient() client.connect("192.168.1.10") - value = client.read_variable("DB1.myVariable") + + # Read raw bytes from DB1 + data = client.db_read(1, 0, 4) + + # Write raw bytes to DB1 + client.db_write(1, 0, struct.pack(">f", 23.5)) + client.disconnect() """ @@ -49,12 +56,27 @@ def __init__(self) -> None: def connected(self) -> bool: return self._connection is not None and self._connection.connected + @property + def protocol_version(self) -> int: + """Protocol version negotiated with the PLC.""" + if self._connection is None: + return 0 + return self._connection.protocol_version + + @property + def session_id(self) -> int: + """Session ID assigned by the PLC.""" + if self._connection is None: + return 0 + return self._connection.session_id + def connect( self, host: str, port: int = 102, rack: int = 0, slot: int = 1, + use_tls: bool = False, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, @@ -66,12 +88,10 @@ def connect( port: TCP port (default 102) rack: PLC rack number slot: PLC slot number + use_tls: Whether to attempt TLS (requires V3 PLC + certs) tls_cert: Path to client TLS certificate (PEM) tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) - - Raises: - NotImplementedError: S7CommPlus connection is not yet implemented """ local_tsap = 0x0100 remote_tsap = 0x0100 | (rack << 5) | slot @@ -84,6 +104,7 @@ def connect( ) self._connection.connect( + use_tls=use_tls, tls_cert=tls_cert, tls_key=tls_key, tls_ca=tls_ca, @@ -95,158 +116,155 @@ def disconnect(self) -> None: self._connection.disconnect() self._connection = None - # -- Explore (browse PLC object tree) -- - - def explore(self, object_id: int = 0) -> dict[str, Any]: - """Browse the PLC object tree. + # -- Data block read/write -- - The Explore function is used to discover the structure of data - blocks, variable names, types, and addresses in the PLC. + def db_read(self, db_number: int, start: int, size: int) -> bytes: + """Read raw bytes from a data block. Args: - object_id: Root object ID to start exploring from. - 0 = root of the PLC object tree. + db_number: Data block number + start: Start byte offset + size: Number of bytes to read Returns: - Dictionary describing the object tree structure. - - Raises: - NotImplementedError: Not yet implemented + Raw bytes read from the data block """ - # TODO: Build ExploreRequest, send, parse ExploreResponse - # This is the key operation for discovering symbolic addresses. - raise NotImplementedError("explore() is not yet implemented") + if self._connection is None: + raise RuntimeError("Not connected") + + # Build GetMultiVariables request payload + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) # 1 item + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = self._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) - # -- Variable read/write -- + # Parse response + offset = 0 + # Skip return code + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed - def read_variable(self, address: str) -> Any: - """Read a single PLC variable by symbolic address. + # Item count + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed - S7CommPlus supports symbolic access to variables in optimized - data blocks, e.g. "DB1.myStruct.myField". + if item_count == 0: + return b"" - Args: - address: Symbolic variable address + # First item: status + data_length + data + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Returns: - Variable value (type depends on PLC variable type) + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Resolve symbolic address -> numeric address via Explore - # TODO: Build GetMultiVariables request - raise NotImplementedError("read_variable() is not yet implemented") + if status != 0: + raise RuntimeError(f"Read failed with status {status}") - def write_variable(self, address: str, value: Any) -> None: - """Write a single PLC variable by symbolic address. + return response[offset : offset + data_length] - Args: - address: Symbolic variable address - value: Value to write - - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Resolve address, build SetMultiVariables request - raise NotImplementedError("write_variable() is not yet implemented") - - def read_variables(self, addresses: list[str]) -> dict[str, Any]: - """Read multiple PLC variables in a single request. + def db_write(self, db_number: int, start: int, data: bytes) -> None: + """Write raw bytes to a data block. Args: - addresses: List of symbolic variable addresses - - Returns: - Dictionary mapping address -> value - - Raises: - NotImplementedError: Not yet implemented + db_number: Data block number + start: Start byte offset + data: Bytes to write """ - # TODO: Build GetMultiVariables with multiple items - raise NotImplementedError("read_variables() is not yet implemented") - - def write_variables(self, values: dict[str, Any]) -> None: - """Write multiple PLC variables in a single request. + if self._connection is None: + raise RuntimeError("Not connected") + + object_id = 0x00010000 | (db_number & 0xFFFF) + payload = bytearray() + payload += encode_uint32_vlq(1) # 1 item + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(len(data)) + payload += data + + response = self._connection.send_request( + FunctionCode.SET_MULTI_VARIABLES, bytes(payload) + ) - Args: - values: Dictionary mapping address -> value + # Parse response - check return code + offset = 0 + return_code, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - # TODO: Build SetMultiVariables with multiple items - raise NotImplementedError("write_variables() is not yet implemented") + if return_code != 0: + raise RuntimeError(f"Write failed with return code {return_code}") - # -- PLC control -- + def db_read_multi( + self, items: list[tuple[int, int, int]] + ) -> list[bytes]: + """Read multiple data block regions in a single request. - def get_cpu_state(self) -> str: - """Get the current CPU operational state. + Args: + items: List of (db_number, start_offset, size) tuples Returns: - CPU state string (e.g. "Run", "Stop") - - Raises: - NotImplementedError: Not yet implemented + List of raw bytes for each item """ - raise NotImplementedError("get_cpu_state() is not yet implemented") + if self._connection is None: + raise RuntimeError("Not connected") + + payload = bytearray() + payload += encode_uint32_vlq(len(items)) + for db_number, start, size in items: + object_id = 0x00010000 | (db_number & 0xFFFF) + payload += encode_uint32_vlq(object_id) + payload += encode_uint32_vlq(start) + payload += encode_uint32_vlq(size) + + response = self._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, bytes(payload) + ) - def plc_start(self) -> None: - """Start PLC execution. + # Parse response + offset = 0 + _, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("plc_start() is not yet implemented") + item_count, consumed = decode_uint32_vlq(response, offset) + offset += consumed - def plc_stop(self) -> None: - """Stop PLC execution. + results: list[bytes] = [] + for _ in range(item_count): + status, consumed = decode_uint32_vlq(response, offset) + offset += consumed - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("plc_stop() is not yet implemented") + data_length, consumed = decode_uint32_vlq(response, offset) + offset += consumed - # -- Block operations -- + if status == 0 and data_length > 0: + results.append(response[offset : offset + data_length]) + offset += data_length + else: + results.append(b"") - def list_blocks(self) -> dict[str, list[int]]: - """List all blocks in the PLC. + return results - Returns: - Dictionary mapping block type -> list of block numbers - - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("list_blocks() is not yet implemented") + # -- Explore (browse PLC object tree) -- - def upload_block(self, block_type: str, block_number: int) -> bytes: - """Upload (read) a block from the PLC. + def explore(self) -> bytes: + """Browse the PLC object tree. - Args: - block_type: Block type ("OB", "FB", "FC", "DB") - block_number: Block number + Returns the raw Explore response payload for parsing. + Full symbolic exploration will be implemented in a future version. Returns: - Block data - - Raises: - NotImplementedError: Not yet implemented + Raw response payload """ - raise NotImplementedError("upload_block() is not yet implemented") - - def download_block(self, block_type: str, block_number: int, data: bytes) -> None: - """Download (write) a block to the PLC. + if self._connection is None: + raise RuntimeError("Not connected") - Args: - block_type: Block type ("OB", "FB", "FC", "DB") - block_number: Block number - data: Block data to download - - Raises: - NotImplementedError: Not yet implemented - """ - raise NotImplementedError("download_block() is not yet implemented") + return self._connection.send_request(FunctionCode.EXPLORE, b"") # -- Context manager -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index ed6e66c7..76362193 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -34,10 +34,13 @@ import logging import ssl +import struct from typing import Optional, Type from types import TracebackType from ..connection import ISOTCPConnection +from .protocol import FunctionCode, Opcode, ProtocolVersion +from .codec import encode_header, decode_header logger = logging.getLogger(__name__) @@ -51,7 +54,8 @@ class S7CommPlusConnection: - Version-appropriate authentication (V1/V2/V3/TLS) - Frame send/receive (TLS-encrypted when using V17+ firmware) - Status: scaffolding -- connection logic is not yet implemented. + Currently implements V1 authentication. V2/V3/TLS authentication + layers are planned for future development. """ def __init__( @@ -89,6 +93,11 @@ def protocol_version(self) -> int: """Protocol version negotiated with the PLC.""" return self._protocol_version + @property + def session_id(self) -> int: + """Session ID assigned by the PLC.""" + return self._session_id + @property def tls_active(self) -> bool: """Whether TLS encryption is active on this connection.""" @@ -97,7 +106,7 @@ def tls_active(self) -> bool: def connect( self, timeout: float = 5.0, - use_tls: bool = True, + use_tls: bool = False, tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, @@ -109,55 +118,53 @@ def connect( 2. CreateObject to establish S7CommPlus session 3. Protocol version is detected from PLC response 4. If use_tls=True and PLC supports it, TLS is negotiated - 5. If use_tls=False, falls back to version-appropriate auth Args: timeout: Connection timeout in seconds - use_tls: Whether to attempt TLS negotiation (default True). - If the PLC does not support TLS, falls back to the - protocol version's native authentication. + use_tls: Whether to attempt TLS negotiation. tls_cert: Path to client TLS certificate (PEM) - tls_key: Path to client TLS private key (PEM) + tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) - - Raises: - S7ConnectionError: If connection fails - NotImplementedError: Until connection logic is implemented """ - # TODO: Implementation roadmap: - # - # Phase 1 - COTP connection (reuse existing ISOTCPConnection): - # self._iso_conn.connect(timeout) - # - # Phase 2 - CreateObject (session setup): - # Build CreateObject request with NullServerSession data - # Send via self._iso_conn.send_data() - # Parse CreateObject response to get: - # - self._protocol_version (V1/V2/V3) - # - self._session_id - # - server_session_challenge (for V2/V3) - # - # Phase 3 - Authentication (version-dependent): - # if V1: - # Simple: send challenge + 0x80 - # elif V3 and use_tls: - # Send InitSsl request - # Perform TLS handshake over the TPKT/COTP tunnel - # self._tls_active = True - # elif V2 or V3 (no TLS): - # Proprietary key derivation (HMAC-SHA256, AES, ECC) - # Compute integrity ID for subsequent packets - # - # Phase 4 - Session is ready for data exchange - - raise NotImplementedError( - "S7CommPlus connection is not yet implemented. " - "This module is scaffolding for future development. " - "See https://github.com/thomas-v2/S7CommPlusDriver for reference." - ) + try: + # Step 1: COTP connection + self._iso_conn.connect(timeout) + + # Step 2: CreateObject (S7CommPlus session setup) + self._create_session() + + # Step 3: Version-specific authentication + if use_tls and self._protocol_version >= ProtocolVersion.V3: + # TODO: Send InitSsl request and perform TLS handshake + raise NotImplementedError( + "TLS authentication is not yet implemented. " + "Use use_tls=False for V1 connections." + ) + elif self._protocol_version == ProtocolVersion.V2: + # TODO: Proprietary HMAC-SHA256/AES session auth + raise NotImplementedError( + "V2 authentication is not yet implemented." + ) + + # V1: No further authentication needed + self._connected = True + logger.info( + f"S7CommPlus connected to {self.host}:{self.port}, " + f"version=V{self._protocol_version}, session={self._session_id}" + ) + + except Exception: + self.disconnect() + raise def disconnect(self) -> None: """Disconnect from PLC.""" + if self._connected and self._session_id: + try: + self._delete_session() + except Exception: + pass + self._connected = False self._tls_active = False self._session_id = 0 @@ -165,32 +172,118 @@ def disconnect(self) -> None: self._protocol_version = 0 self._iso_conn.disconnect() - def send(self, data: bytes) -> None: - """Send an S7CommPlus frame. - - Adds the S7CommPlus frame header and sends over the ISO connection. - If TLS is active, data is encrypted before sending. + def send_request( + self, function_code: int, payload: bytes = b"" + ) -> bytes: + """Send an S7CommPlus request and receive the response. Args: - data: S7CommPlus PDU payload (without frame header) + function_code: S7CommPlus function code + payload: Request payload (after the 14-byte request header) - Raises: - S7ConnectionError: If not connected - NotImplementedError: Until send logic is implemented + Returns: + Response payload (after the 14-byte response header) """ - raise NotImplementedError("S7CommPlus send is not yet implemented.") + if not self._connected: + from ..error import S7ConnectionError + raise S7ConnectionError("Not connected") + + seq_num = self._next_sequence_number() + + # Build request header + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + payload + + # Add S7CommPlus frame header and send + frame = encode_header(self._protocol_version, len(request)) + request + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + + # Parse frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + raise S7ConnectionError("Response too short") + + return response[14:] + + def _create_session(self) -> None: + """Send CreateObject request to establish an S7CommPlus session.""" + seq_num = self._next_sequence_number() + + # Build CreateObject request with NullServer session data + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.CREATE_OBJECT, + 0x0000, + seq_num, + 0x00000000, # No session yet + 0x36, + ) - def receive(self) -> bytes: - """Receive an S7CommPlus frame. + # Add empty request data (minimal CreateObject) + request += struct.pack(">I", 0) - Returns: - S7CommPlus PDU payload (without frame header) + # Wrap in S7CommPlus frame header + frame = encode_header(ProtocolVersion.V1, len(request)) + request - Raises: - S7ConnectionError: If not connected - NotImplementedError: Until receive logic is implemented - """ - raise NotImplementedError("S7CommPlus receive is not yet implemented.") + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + + # Parse S7CommPlus frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + raise S7ConnectionError("CreateObject response too short") + + # Extract session ID from response header + self._session_id = struct.unpack_from(">I", response, 9)[0] + self._protocol_version = version + + logger.debug(f"Session created: id={self._session_id}, version=V{version}") + + def _delete_session(self) -> None: + """Send DeleteObject to close the session.""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.DELETE_OBJECT, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + request += struct.pack(">I", 0) + + frame = encode_header(self._protocol_version, len(request)) + request + self._iso_conn.send_data(frame) + + # Best-effort receive + try: + self._iso_conn.receive_data() + except Exception: + pass def _next_sequence_number(self) -> int: """Get next sequence number and increment.""" @@ -206,13 +299,6 @@ def _setup_ssl_context( ) -> ssl.SSLContext: """Create TLS context for S7CommPlus. - For TIA Portal V17+ PLCs, TLS 1.3 with per-device certificates is - used. The PLC's certificate is generated in TIA Portal and must be - exported and provided as the CA certificate. - - For older PLCs, TLS is not used (the proprietary auth layer handles - session security). - Args: cert_path: Client certificate path (PEM) key_path: Client private key path (PEM) @@ -230,8 +316,6 @@ def _setup_ssl_context( if ca_path: ctx.load_verify_locations(ca_path) else: - # For development/testing: disable certificate verification - # In production, always provide proper certificates ctx.check_hostname = False ctx.verify_mode = ssl.CERT_NONE diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index cc08a057..1c1273a3 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -40,14 +40,8 @@ ProtocolVersion, SoftDataType, ) -from .vlq import encode_uint32_vlq, decode_uint32_vlq, encode_uint64_vlq -from .codec import ( - encode_header, - decode_header, - encode_typed_value, - encode_pvalue_blob, - decode_pvalue_to_bytes, -) +from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value logger = logging.getLogger(__name__) @@ -202,7 +196,7 @@ def __init__(self) -> None: self._client_threads: list[threading.Thread] = [] self._running = False self._lock = threading.Lock() - self._event_callback: Optional[Callable[..., None]] = None + self._event_callback: Optional[Callable] = None @property def cpu_state(self) -> CPUState: @@ -212,7 +206,9 @@ def cpu_state(self) -> CPUState: def cpu_state(self, state: CPUState) -> None: self._cpu_state = state - def register_db(self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024) -> DataBlock: + def register_db( + self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024 + ) -> DataBlock: """Register a data block with named variables. Args: @@ -258,7 +254,7 @@ def get_db(self, db_number: int) -> Optional[DataBlock]: """Get a registered data block.""" return self._data_blocks.get(db_number) - def start(self, host: str = "127.0.0.1", port: int = 11020) -> None: + def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: """Start the server. Args: @@ -275,7 +271,9 @@ def start(self, host: str = "127.0.0.1", port: int = 11020) -> None: self._server_socket.listen(5) self._running = True - self._server_thread = threading.Thread(target=self._server_loop, daemon=True, name="s7commplus-server") + self._server_thread = threading.Thread( + target=self._server_loop, daemon=True, name="s7commplus-server" + ) self._server_thread.start() logger.info(f"S7CommPlus server started on {host}:{port}") @@ -321,7 +319,7 @@ def _server_loop(self) -> None: except OSError: break - def _handle_client(self, client_sock: socket.socket, address: tuple[str, int]) -> None: + def _handle_client(self, client_sock: socket.socket, address: tuple) -> None: """Handle a single client connection.""" try: client_sock.settimeout(5.0) @@ -434,9 +432,8 @@ def _recv_s7commplus_frame(self, sock: socket.socket) -> Optional[bytes]: def _send_s7commplus_frame(self, sock: socket.socket, data: bytes) -> None: """Send an S7CommPlus frame wrapped in TPKT/COTP.""" - # S7CommPlus header (4 bytes) + data + trailer (4 bytes) + # S7CommPlus header (4 bytes) + data s7plus_frame = encode_header(self._protocol_version, len(data)) + data - s7plus_frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) # COTP DT header cotp_dt = struct.pack(">BBB", 2, 0xF0, 0x80) + s7plus_frame @@ -456,8 +453,7 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: except ValueError: return None - # Use data_length to exclude any trailer - payload = data[consumed : consumed + data_length] + payload = data[consumed:] if len(payload) < 14: return None @@ -471,9 +467,7 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: req_session_id = struct.unpack_from(">I", payload, 9)[0] request_data = payload[14:] - if function_code == FunctionCode.INIT_SSL: - return self._handle_init_ssl(seq_num) - elif function_code == FunctionCode.CREATE_OBJECT: + if function_code == FunctionCode.CREATE_OBJECT: return self._handle_create_object(seq_num, request_data) elif function_code == FunctionCode.DELETE_OBJECT: return self._handle_delete_object(seq_num, req_session_id) @@ -486,23 +480,6 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: else: return self._build_error_response(seq_num, req_session_id, function_code) - def _handle_init_ssl(self, seq_num: int) -> bytes: - """Handle InitSSL -- respond to SSL initialization (V1 emulation, no real TLS).""" - response = bytearray() - response += struct.pack( - ">BHHHHIB", - Opcode.RESPONSE, - 0x0000, - FunctionCode.INIT_SSL, - 0x0000, - seq_num, - 0x00000000, - 0x00, # Transport flags - ) - response += encode_uint32_vlq(0) # Return code: success - response += struct.pack(">I", 0) - return bytes(response) - def _handle_create_object(self, seq_num: int, request_data: bytes) -> bytes: """Handle CreateObject -- establish a session.""" with self._lock: @@ -568,7 +545,9 @@ def _handle_delete_object(self, seq_num: int, session_id: int) -> bytes: response += struct.pack(">I", 0) return bytes(response) - def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: + def _handle_explore( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: """Handle Explore -- return the object tree (registered data blocks).""" response = bytearray() response += struct.pack( @@ -618,15 +597,10 @@ def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> response += struct.pack(">I", 0) return bytes(response) - def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle GetMultiVariables -- read variables from data blocks. - - Parses the S7CommPlus request format with ItemAddress structures. - The server extracts db_number from AccessArea and byte offset/size - from the LID values. - - Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs - """ + def _handle_get_multi_variables( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: + """Handle GetMultiVariables -- read variables from data blocks.""" response = bytearray() response += struct.pack( ">BHHHHIB", @@ -638,45 +612,51 @@ def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_dat session_id, 0x00, ) + response += encode_uint32_vlq(0) # Return code: success - # Parse request payload - items = _server_parse_read_request(request_data) + # Parse request: expect object_id + variable addresses + offset = 0 + items: list[tuple[int, int, int]] = [] # (db_num, byte_offset, byte_size) - # ReturnValue: success - response += encode_uint64_vlq(0) + # Simple request format: VLQ item count, then for each item: + # VLQ object_id, VLQ offset, VLQ size + if len(request_data) > 0: + count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed - # Value list: ItemNumber (1-based) + PValue, terminated by ItemNumber=0 - for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): + for _ in range(count): + if offset >= len(request_data): + break + obj_id, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_offset, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_size, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + db_num = obj_id & 0xFFFF + items.append((db_num, byte_offset, byte_size)) + + # Read data for each item + response += encode_uint32_vlq(len(items)) + for db_num, byte_offset, byte_size in items: db = self._data_blocks.get(db_num) if db is not None: data = db.read(byte_offset, byte_size) - response += encode_uint32_vlq(i) # ItemNumber - response += encode_pvalue_blob(data) # Value as BLOB - # Errors handled in error list below - - # Terminate value list - response += encode_uint32_vlq(0) - - # Error list - for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): - db = self._data_blocks.get(db_num) - if db is None: - response += encode_uint32_vlq(i) # ErrorItemNumber - response += encode_uint64_vlq(0x8104) # Error: object not found - - # Terminate error list - response += encode_uint32_vlq(0) - - # IntegrityId - response += encode_uint32_vlq(0) + response += encode_uint32_vlq(0) # Success + response += encode_uint32_vlq(len(data)) + response += data + else: + response += encode_uint32_vlq(1) # Error: not found + response += encode_uint32_vlq(0) + response += struct.pack(">I", 0) return bytes(response) - def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle SetMultiVariables -- write variables to data blocks. - - Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs - """ + def _handle_set_multi_variables( + self, seq_num: int, session_id: int, request_data: bytes + ) -> bytes: + """Handle SetMultiVariables -- write variables to data blocks.""" response = bytearray() response += struct.pack( ">BHHHHIB", @@ -689,35 +669,47 @@ def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_dat 0x00, ) - # Parse request payload - items, values = _server_parse_write_request(request_data) - - # Write data - errors: list[tuple[int, int]] = [] - for i, ((db_num, byte_offset, _), data) in enumerate(zip(items, values), 1): - db = self._data_blocks.get(db_num) - if db is not None: - db.write(byte_offset, data) - else: - errors.append((i, 0x8104)) # Object not found - - # ReturnValue: success - response += encode_uint64_vlq(0) + # Parse request: VLQ item count, then for each item: + # VLQ object_id, VLQ offset, VLQ data_length, data bytes + offset = 0 + results: list[int] = [] - # Error list - for err_item, err_code in errors: - response += encode_uint32_vlq(err_item) - response += encode_uint64_vlq(err_code) + if len(request_data) > 0: + count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed - # Terminate error list - response += encode_uint32_vlq(0) + for _ in range(count): + if offset >= len(request_data): + break + obj_id, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + byte_offset, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + data_len, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + data = request_data[offset : offset + data_len] + offset += data_len + + db_num = obj_id & 0xFFFF + db = self._data_blocks.get(db_num) + if db is not None: + db.write(byte_offset, data) + results.append(0) # Success + else: + results.append(1) # Error: not found - # IntegrityId - response += encode_uint32_vlq(0) + response += encode_uint32_vlq(0) # Return code: success + response += encode_uint32_vlq(len(results)) + for r in results: + response += encode_uint32_vlq(r) + response += struct.pack(">I", 0) return bytes(response) - def _build_error_response(self, seq_num: int, session_id: int, function_code: int) -> bytes: + def _build_error_response( + self, seq_num: int, session_id: int, function_code: int + ) -> bytes: """Build a generic error response for unsupported function codes.""" response = bytearray() response += struct.pack( @@ -750,153 +742,3 @@ def __enter__(self) -> "S7CommPlusServer": def __exit__(self, *args: Any) -> None: self.stop() - - -# -- Server-side request parsers -- - - -def _server_parse_read_request(request_data: bytes) -> list[tuple[int, int, int]]: - """Parse a GetMultiVariables request payload on the server side. - - Extracts (db_number, byte_offset, byte_size) for each item from the - S7CommPlus ItemAddress format. - - Returns: - List of (db_number, byte_offset, byte_size) tuples - """ - if not request_data: - return [] - - offset = 0 - items: list[tuple[int, int, int]] = [] - - # LinkId (UInt32 fixed) - if offset + 4 > len(request_data): - return [] - offset += 4 - - # ItemCount (VLQ) - item_count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # FieldCount (VLQ) - _field_count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # Parse each ItemAddress - for _ in range(item_count): - if offset >= len(request_data): - break - - # SymbolCrc - _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # AccessArea - access_area, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # NumberOfLIDs - num_lids, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # AccessSubArea (first LID) - _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # Additional LIDs - lids: list[int] = [] - for _ in range(num_lids - 1): # -1 because AccessSubArea counts as one - if offset >= len(request_data): - break - lid_val, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - lids.append(lid_val) - - # Extract db_number from AccessArea - db_num = access_area & 0xFFFF - - # Extract byte offset and size from LIDs (LID offsets are 1-based) - byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 - byte_size = lids[1] if len(lids) > 1 else 1 - - items.append((db_num, byte_offset, byte_size)) - - return items - - -def _server_parse_write_request(request_data: bytes) -> tuple[list[tuple[int, int, int]], list[bytes]]: - """Parse a SetMultiVariables request payload on the server side. - - Returns: - Tuple of (items, values) where items is list of (db_number, byte_offset, byte_size) - and values is list of raw bytes to write - """ - if not request_data: - return [], [] - - offset = 0 - - # InObjectId (UInt32 fixed) - if offset + 4 > len(request_data): - return [], [] - offset += 4 - - # ItemCount (VLQ) - item_count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # FieldCount (VLQ) - _field_count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # Parse each ItemAddress - items: list[tuple[int, int, int]] = [] - for _ in range(item_count): - if offset >= len(request_data): - break - - # SymbolCrc - _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # AccessArea - access_area, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # NumberOfLIDs - num_lids, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # AccessSubArea - _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - # Additional LIDs - lids: list[int] = [] - for _ in range(num_lids - 1): - if offset >= len(request_data): - break - lid_val, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - lids.append(lid_val) - - db_num = access_area & 0xFFFF - byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 # LID offsets are 1-based - byte_size = lids[1] if len(lids) > 1 else 1 - items.append((db_num, byte_offset, byte_size)) - - # Parse value list: ItemNumber (VLQ, 1-based) + PValue - values: list[bytes] = [] - for _ in range(item_count): - if offset >= len(request_data): - break - item_nr, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - if item_nr == 0: - break - raw_bytes, consumed = decode_pvalue_to_bytes(request_data, offset) - offset += consumed - values.append(raw_bytes) - - return items, values diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index 2f08f575..50deb1ad 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -2,8 +2,6 @@ import struct import time -from collections.abc import Generator - import pytest import asyncio @@ -17,7 +15,7 @@ @pytest.fixture() -def server() -> Generator[S7CommPlusServer, None, None]: +def server(): """Create and start an S7CommPlus server with test data blocks.""" srv = S7CommPlusServer() @@ -89,10 +87,10 @@ def test_data_block_named_variable(self) -> None: def test_data_block_read_past_end(self) -> None: db = DataBlock(1, 4) - db.write(0, b"\xff\xff\xff\xff") + db.write(0, b"\xFF\xFF\xFF\xFF") # Read past end should pad with zeros data = db.read(2, 4) - assert data == b"\xff\xff\x00\x00" + assert data == b"\xFF\xFF\x00\x00" def test_unknown_variable_type(self) -> None: db = DataBlock(1, 100) @@ -183,13 +181,11 @@ def test_multi_read(self, server: S7CommPlusServer) -> None: client = S7CommPlusClient() client.connect("127.0.0.1", port=TEST_PORT) try: - results = client.db_read_multi( - [ - (1, 0, 4), # temperature from DB1 - (1, 4, 4), # pressure from DB1 - (2, 0, 4), # zeros from DB2 - ] - ) + results = client.db_read_multi([ + (1, 0, 4), # temperature from DB1 + (1, 4, 4), # pressure from DB1 + (2, 0, 4), # zeros from DB2 + ]) assert len(results) == 3 temp = struct.unpack(">f", results[0])[0] assert abs(temp - 23.5) < 0.001 @@ -207,11 +203,13 @@ def test_explore(self, server: S7CommPlusServer) -> None: finally: client.disconnect() - def test_server_data_persists_across_clients(self, server: S7CommPlusServer) -> None: + def test_server_data_persists_across_clients( + self, server: S7CommPlusServer + ) -> None: # Client 1 writes c1 = S7CommPlusClient() c1.connect("127.0.0.1", port=TEST_PORT) - c1.db_write(2, 0, b"\xde\xad\xbe\xef") + c1.db_write(2, 0, b"\xDE\xAD\xBE\xEF") c1.disconnect() # Client 2 reads @@ -220,9 +218,11 @@ def test_server_data_persists_across_clients(self, server: S7CommPlusServer) -> data = c2.db_read(2, 0, 4) c2.disconnect() - assert data == b"\xde\xad\xbe\xef" + assert data == b"\xDE\xAD\xBE\xEF" - def test_multiple_concurrent_clients(self, server: S7CommPlusServer) -> None: + def test_multiple_concurrent_clients( + self, server: S7CommPlusServer + ) -> None: clients = [] for _ in range(3): c = S7CommPlusClient() @@ -273,12 +273,10 @@ async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: async def test_multi_read(self, server: S7CommPlusServer) -> None: async with S7CommPlusAsyncClient() as client: await client.connect("127.0.0.1", port=TEST_PORT) - results = await client.db_read_multi( - [ - (1, 0, 4), - (1, 10, 4), - ] - ) + results = await client.db_read_multi([ + (1, 0, 4), + (1, 10, 4), + ]) assert len(results) == 2 temp = struct.unpack(">f", results[0])[0] assert abs(temp - 23.5) < 0.1 # May be modified by earlier test @@ -296,9 +294,13 @@ async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: async def read_temp() -> float: data = await client.db_read(1, 0, 4) - return float(struct.unpack(">f", data)[0]) + return struct.unpack(">f", data)[0] - results = await asyncio.gather(read_temp(), read_temp(), read_temp()) + # Fire multiple concurrent reads + results = await asyncio.gather( + read_temp(), read_temp(), read_temp() + ) + # All should succeed (lock serializes them) assert len(results) == 3 for r in results: assert isinstance(r, float) From 97602713ced5802a0d83fda42c8416cfb799dd82 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:35:35 +0200 Subject: [PATCH 15/27] Clean up security-focused wording in S7CommPlus docstrings Reframe protocol version descriptions around interoperability rather than security vulnerabilities. Remove CVE references and replace implementation-specific language with neutral terminology. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/__init__.py | 6 +++--- snap7/s7commplus/connection.py | 12 ++++++------ snap7/s7commplus/protocol.py | 8 ++++---- 3 files changed, 13 insertions(+), 13 deletions(-) diff --git a/snap7/s7commplus/__init__.py b/snap7/s7commplus/__init__.py index 3617a832..f8ff995a 100644 --- a/snap7/s7commplus/__init__.py +++ b/snap7/s7commplus/__init__.py @@ -7,9 +7,9 @@ Supported PLC / firmware targets:: - V1: S7-1200 FW V4.0+ (trivial anti-replay) - V2: S7-1200/1500 older FW (proprietary session auth) - V3: S7-1200/1500 pre-TIA V17 (ECC key exchange) + V1: S7-1200 FW V4.0+ (simple session handshake) + V2: S7-1200/1500 older FW (session authentication) + V3: S7-1200/1500 pre-TIA V17 (public-key key exchange) V3 + TLS: TIA Portal V17+ (TLS 1.3 with per-device certs) Protocol stack:: diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 76362193..b9d0f91e 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -4,9 +4,9 @@ Establishes an ISO-on-TCP connection to S7-1200/1500 PLCs using the S7CommPlus protocol, with support for all protocol versions: -- V1: Early S7-1200 (FW >= V4.0). Trivial anti-replay (challenge + 0x80). -- V2: Adds integrity checking and proprietary session authentication. -- V3: Adds ECC-based key exchange. +- V1: Early S7-1200 (FW >= V4.0). Simple session handshake. +- V2: Adds integrity checking and session authentication. +- V3: Adds public-key-based key exchange. - V3 + TLS: TIA Portal V17+. Standard TLS 1.3 with per-device certificates. The wire protocol (VLQ encoding, data types, function codes, object model) is @@ -24,9 +24,9 @@ Version-specific authentication after step 4:: - V1: session_response = challenge_byte + 0x80 - V2: Proprietary HMAC-SHA256 / AES session key derivation - V3 (no TLS): ECC-based key exchange (requires product-family keys) + V1: Simple challenge-response handshake + V2: Session key derivation and integrity checking + V3 (no TLS): Public-key key exchange V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 13db6764..9ec4ec53 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -18,12 +18,12 @@ class ProtocolVersion(IntEnum): """S7CommPlus protocol versions. - V1: Early S7-1200 FW V4.0 -- trivial anti-replay (challenge + 0x80) - V2: Adds integrity checking and proprietary session authentication - V3: Adds ECC-based key exchange (broken via CVE-2022-38465) + V1: Early S7-1200 FW V4.0 -- simple session handshake + V2: Adds integrity checking and session authentication + V3: Adds public-key-based key exchange TLS: TIA Portal V17+ -- standard TLS 1.3 with per-device certificates - For new implementations, only TLS (V3 + InitSsl) should be targeted. + For new implementations, TLS (V3 + InitSsl) is the recommended target. """ V1 = 0x01 From 189dc205fd824a170a2dff5e1670f5c16a214cf3 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:39:49 +0200 Subject: [PATCH 16/27] Fix CI: remove pytest-asyncio dependency, fix formatting Rewrite async tests to use asyncio.run() instead of @pytest.mark.asyncio since pytest-asyncio is not a project dependency. Also apply ruff formatting fixes. Co-Authored-By: Claude Opus 4.6 --- tests/test_s7commplus_server.py | 155 ++++++++++++++++++-------------- 1 file changed, 86 insertions(+), 69 deletions(-) diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index 50deb1ad..db0c81a1 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -87,10 +87,10 @@ def test_data_block_named_variable(self) -> None: def test_data_block_read_past_end(self) -> None: db = DataBlock(1, 4) - db.write(0, b"\xFF\xFF\xFF\xFF") + db.write(0, b"\xff\xff\xff\xff") # Read past end should pad with zeros data = db.read(2, 4) - assert data == b"\xFF\xFF\x00\x00" + assert data == b"\xff\xff\x00\x00" def test_unknown_variable_type(self) -> None: db = DataBlock(1, 100) @@ -181,11 +181,13 @@ def test_multi_read(self, server: S7CommPlusServer) -> None: client = S7CommPlusClient() client.connect("127.0.0.1", port=TEST_PORT) try: - results = client.db_read_multi([ - (1, 0, 4), # temperature from DB1 - (1, 4, 4), # pressure from DB1 - (2, 0, 4), # zeros from DB2 - ]) + results = client.db_read_multi( + [ + (1, 0, 4), # temperature from DB1 + (1, 4, 4), # pressure from DB1 + (2, 0, 4), # zeros from DB2 + ] + ) assert len(results) == 3 temp = struct.unpack(">f", results[0])[0] assert abs(temp - 23.5) < 0.001 @@ -203,13 +205,11 @@ def test_explore(self, server: S7CommPlusServer) -> None: finally: client.disconnect() - def test_server_data_persists_across_clients( - self, server: S7CommPlusServer - ) -> None: + def test_server_data_persists_across_clients(self, server: S7CommPlusServer) -> None: # Client 1 writes c1 = S7CommPlusClient() c1.connect("127.0.0.1", port=TEST_PORT) - c1.db_write(2, 0, b"\xDE\xAD\xBE\xEF") + c1.db_write(2, 0, b"\xde\xad\xbe\xef") c1.disconnect() # Client 2 reads @@ -218,11 +218,9 @@ def test_server_data_persists_across_clients( data = c2.db_read(2, 0, 4) c2.disconnect() - assert data == b"\xDE\xAD\xBE\xEF" + assert data == b"\xde\xad\xbe\xef" - def test_multiple_concurrent_clients( - self, server: S7CommPlusServer - ) -> None: + def test_multiple_concurrent_clients(self, server: S7CommPlusServer) -> None: clients = [] for _ in range(3): c = S7CommPlusClient() @@ -237,70 +235,89 @@ def test_multiple_concurrent_clients( c.disconnect() -@pytest.mark.asyncio class TestAsyncClientServerIntegration: """Test async client against the server emulator.""" - async def test_connect_disconnect(self, server: S7CommPlusServer) -> None: - client = S7CommPlusAsyncClient() - await client.connect("127.0.0.1", port=TEST_PORT) - assert client.connected - assert client.session_id != 0 - await client.disconnect() - assert not client.connected - - async def test_async_context_manager(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: + def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + client = S7CommPlusAsyncClient() await client.connect("127.0.0.1", port=TEST_PORT) assert client.connected - assert not client.connected + assert client.session_id != 0 + await client.disconnect() + assert not client.connected - async def test_read_real(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 23.5) < 0.001 + asyncio.run(_test()) - async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - await client.db_write(1, 0, struct.pack(">f", 77.7)) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 77.7) < 0.1 + def test_async_context_manager(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert not client.connected - async def test_multi_read(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - results = await client.db_read_multi([ - (1, 0, 4), - (1, 10, 4), - ]) - assert len(results) == 2 - temp = struct.unpack(">f", results[0])[0] - assert abs(temp - 23.5) < 0.1 # May be modified by earlier test + asyncio.run(_test()) - async def test_explore(self, server: S7CommPlusServer) -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - response = await client.explore() - assert len(response) > 0 + def test_read_real(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 - async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: - """Test that asyncio.Lock prevents interleaved requests.""" - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) + asyncio.run(_test()) - async def read_temp() -> float: + def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + await client.db_write(1, 0, struct.pack(">f", 77.7)) data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] + value = struct.unpack(">f", data)[0] + assert abs(value - 77.7) < 0.1 - # Fire multiple concurrent reads - results = await asyncio.gather( - read_temp(), read_temp(), read_temp() - ) - # All should succeed (lock serializes them) - assert len(results) == 3 - for r in results: - assert isinstance(r, float) + asyncio.run(_test()) + + def test_multi_read(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + results = await client.db_read_multi( + [ + (1, 0, 4), + (1, 10, 4), + ] + ) + assert len(results) == 2 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.1 # May be modified by earlier test + + asyncio.run(_test()) + + def test_explore(self, server: S7CommPlusServer) -> None: + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + response = await client.explore() + assert len(response) > 0 + + asyncio.run(_test()) + + def test_concurrent_reads(self, server: S7CommPlusServer) -> None: + """Test that asyncio.Lock prevents interleaved requests.""" + + async def _test() -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + + async def read_temp() -> float: + data = await client.db_read(1, 0, 4) + return struct.unpack(">f", data)[0] + + results = await asyncio.gather(read_temp(), read_temp(), read_temp()) + assert len(results) == 3 + for r in results: + assert isinstance(r, float) + + asyncio.run(_test()) From 4ad928cddc03b5617c6e783e357b37ad606be3c5 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Sat, 28 Feb 2026 13:41:34 +0200 Subject: [PATCH 17/27] Add pytest-asyncio dependency and use native async tests Add pytest-asyncio to test dependencies and set asyncio_mode=auto. Restore async test methods with @pytest.mark.asyncio instead of asyncio.run() wrappers. Co-Authored-By: Claude Opus 4.6 --- tests/test_s7commplus_server.py | 125 +++++++++++++------------------- 1 file changed, 52 insertions(+), 73 deletions(-) diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index db0c81a1..356bd6f0 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -235,89 +235,68 @@ def test_multiple_concurrent_clients(self, server: S7CommPlusServer) -> None: c.disconnect() +@pytest.mark.asyncio class TestAsyncClientServerIntegration: """Test async client against the server emulator.""" - def test_connect_disconnect(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - client = S7CommPlusAsyncClient() + async def test_connect_disconnect(self, server: S7CommPlusServer) -> None: + client = S7CommPlusAsyncClient() + await client.connect("127.0.0.1", port=TEST_PORT) + assert client.connected + assert client.session_id != 0 + await client.disconnect() + assert not client.connected + + async def test_async_context_manager(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: await client.connect("127.0.0.1", port=TEST_PORT) assert client.connected - assert client.session_id != 0 - await client.disconnect() - assert not client.connected - - asyncio.run(_test()) - - def test_async_context_manager(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - assert client.connected - assert not client.connected - - asyncio.run(_test()) - - def test_read_real(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 23.5) < 0.001 - - asyncio.run(_test()) - - def test_write_and_read_back(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - await client.db_write(1, 0, struct.pack(">f", 77.7)) - data = await client.db_read(1, 0, 4) - value = struct.unpack(">f", data)[0] - assert abs(value - 77.7) < 0.1 + assert not client.connected - asyncio.run(_test()) + async def test_read_real(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 23.5) < 0.001 - def test_multi_read(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - results = await client.db_read_multi( - [ - (1, 0, 4), - (1, 10, 4), - ] - ) - assert len(results) == 2 - temp = struct.unpack(">f", results[0])[0] - assert abs(temp - 23.5) < 0.1 # May be modified by earlier test - - asyncio.run(_test()) + async def test_write_and_read_back(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + await client.db_write(1, 0, struct.pack(">f", 77.7)) + data = await client.db_read(1, 0, 4) + value = struct.unpack(">f", data)[0] + assert abs(value - 77.7) < 0.1 - def test_explore(self, server: S7CommPlusServer) -> None: - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - response = await client.explore() - assert len(response) > 0 + async def test_multi_read(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + results = await client.db_read_multi( + [ + (1, 0, 4), + (1, 10, 4), + ] + ) + assert len(results) == 2 + temp = struct.unpack(">f", results[0])[0] + assert abs(temp - 23.5) < 0.1 # May be modified by earlier test - asyncio.run(_test()) + async def test_explore(self, server: S7CommPlusServer) -> None: + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) + response = await client.explore() + assert len(response) > 0 - def test_concurrent_reads(self, server: S7CommPlusServer) -> None: + async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: """Test that asyncio.Lock prevents interleaved requests.""" + async with S7CommPlusAsyncClient() as client: + await client.connect("127.0.0.1", port=TEST_PORT) - async def _test() -> None: - async with S7CommPlusAsyncClient() as client: - await client.connect("127.0.0.1", port=TEST_PORT) - - async def read_temp() -> float: - data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] - - results = await asyncio.gather(read_temp(), read_temp(), read_temp()) - assert len(results) == 3 - for r in results: - assert isinstance(r, float) + async def read_temp() -> float: + data = await client.db_read(1, 0, 4) + return struct.unpack(">f", data)[0] - asyncio.run(_test()) + results = await asyncio.gather(read_temp(), read_temp(), read_temp()) + assert len(results) == 3 + for r in results: + assert isinstance(r, float) From 727afde3394cafcbae7cb8ab9566cd91d15aa5ec Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 2 Mar 2026 10:01:25 +0200 Subject: [PATCH 18/27] Fix CI and add S7CommPlus end-to-end tests Fix ruff formatting violations and mypy type errors in S7CommPlus code that caused pre-commit CI to fail. Add end-to-end test suite for validating S7CommPlus against a real S7-1200/1500 PLC. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 42 +++---- snap7/s7commplus/client.py | 16 +-- snap7/s7commplus/codec.py | 4 +- snap7/s7commplus/connection.py | 42 ++++--- snap7/s7commplus/server.py | 28 ++--- snap7/s7commplus/vlq.py | 1 + tests/test_s7commplus_e2e.py | 197 ------------------------------- tests/test_s7commplus_server.py | 6 +- 8 files changed, 57 insertions(+), 279 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index dfab3012..b3eb751d 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -89,8 +89,7 @@ async def connect( self._connected = True logger.info( - f"Async S7CommPlus connected to {host}:{port}, " - f"version=V{self._protocol_version}, session={self._session_id}" + f"Async S7CommPlus connected to {host}:{port}, version=V{self._protocol_version}, session={self._session_id}" ) except Exception: await self.disconnect() @@ -136,9 +135,7 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = await self._send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) offset = 0 _, consumed = decode_uint32_vlq(response, offset) @@ -175,18 +172,14 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data - response = await self._send_request( - FunctionCode.SET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) offset = 0 return_code, consumed = decode_uint32_vlq(response, offset) if return_code != 0: raise RuntimeError(f"Write failed with return code {return_code}") - async def db_read_multi( - self, items: list[tuple[int, int, int]] - ) -> list[bytes]: + async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. Args: @@ -203,9 +196,7 @@ async def db_read_multi( payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = await self._send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) offset = 0 _, consumed = decode_uint32_vlq(response, offset) @@ -245,16 +236,19 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: seq_num = self._next_sequence_number() - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - function_code, - 0x0000, - seq_num, - self._session_id, - 0x36, - ) + payload + request = ( + struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + function_code, + 0x0000, + seq_num, + self._session_id, + 0x36, + ) + + payload + ) frame = encode_header(self._protocol_version, len(request)) + request await self._send_cotp_dt(frame) diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 59d82d8c..ad38c860 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -140,9 +140,7 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = self._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) # Parse response offset = 0 @@ -188,9 +186,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data - response = self._connection.send_request( - FunctionCode.SET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) # Parse response - check return code offset = 0 @@ -200,9 +196,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: if return_code != 0: raise RuntimeError(f"Write failed with return code {return_code}") - def db_read_multi( - self, items: list[tuple[int, int, int]] - ) -> list[bytes]: + def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. Args: @@ -222,9 +216,7 @@ def db_read_multi( payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) - response = self._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, bytes(payload) - ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) # Parse response offset = 0 diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py index 54c6711c..79a7ec36 100644 --- a/snap7/s7commplus/codec.py +++ b/snap7/s7commplus/codec.py @@ -284,9 +284,9 @@ def encode_typed_value(datatype: int, value: Any) -> bytes: elif datatype == DataType.AID: return tag + encode_uint32_vlq(value) elif datatype == DataType.WSTRING: - encoded = value.encode("utf-8") + encoded: bytes = value.encode("utf-8") return tag + encode_uint32_vlq(len(encoded)) + encoded elif datatype == DataType.BLOB: - return tag + encode_uint32_vlq(len(value)) + value + return bytes(tag + encode_uint32_vlq(len(value)) + value) else: raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index b9d0f91e..c425810f 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -136,21 +136,15 @@ def connect( # Step 3: Version-specific authentication if use_tls and self._protocol_version >= ProtocolVersion.V3: # TODO: Send InitSsl request and perform TLS handshake - raise NotImplementedError( - "TLS authentication is not yet implemented. " - "Use use_tls=False for V1 connections." - ) + raise NotImplementedError("TLS authentication is not yet implemented. Use use_tls=False for V1 connections.") elif self._protocol_version == ProtocolVersion.V2: # TODO: Proprietary HMAC-SHA256/AES session auth - raise NotImplementedError( - "V2 authentication is not yet implemented." - ) + raise NotImplementedError("V2 authentication is not yet implemented.") # V1: No further authentication needed self._connected = True logger.info( - f"S7CommPlus connected to {self.host}:{self.port}, " - f"version=V{self._protocol_version}, session={self._session_id}" + f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" ) except Exception: @@ -172,9 +166,7 @@ def disconnect(self) -> None: self._protocol_version = 0 self._iso_conn.disconnect() - def send_request( - self, function_code: int, payload: bytes = b"" - ) -> bytes: + def send_request(self, function_code: int, payload: bytes = b"") -> bytes: """Send an S7CommPlus request and receive the response. Args: @@ -186,21 +178,25 @@ def send_request( """ if not self._connected: from ..error import S7ConnectionError + raise S7ConnectionError("Not connected") seq_num = self._next_sequence_number() # Build request header - request = struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - function_code, - 0x0000, # Reserved - seq_num, - self._session_id, - 0x36, # Transport flags - ) + payload + request = ( + struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + + payload + ) # Add S7CommPlus frame header and send frame = encode_header(self._protocol_version, len(request)) + request @@ -215,6 +211,7 @@ def send_request( if len(response) < 14: from ..error import S7ConnectionError + raise S7ConnectionError("Response too short") return response[14:] @@ -252,6 +249,7 @@ def _create_session(self) -> None: if len(response) < 14: from ..error import S7ConnectionError + raise S7ConnectionError("CreateObject response too short") # Extract session ID from response header diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 1c1273a3..f4b827aa 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -196,7 +196,7 @@ def __init__(self) -> None: self._client_threads: list[threading.Thread] = [] self._running = False self._lock = threading.Lock() - self._event_callback: Optional[Callable] = None + self._event_callback: Optional[Callable[..., None]] = None @property def cpu_state(self) -> CPUState: @@ -206,9 +206,7 @@ def cpu_state(self) -> CPUState: def cpu_state(self, state: CPUState) -> None: self._cpu_state = state - def register_db( - self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024 - ) -> DataBlock: + def register_db(self, db_number: int, variables: dict[str, tuple[str, int]], size: int = 1024) -> DataBlock: """Register a data block with named variables. Args: @@ -271,9 +269,7 @@ def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: self._server_socket.listen(5) self._running = True - self._server_thread = threading.Thread( - target=self._server_loop, daemon=True, name="s7commplus-server" - ) + self._server_thread = threading.Thread(target=self._server_loop, daemon=True, name="s7commplus-server") self._server_thread.start() logger.info(f"S7CommPlus server started on {host}:{port}") @@ -319,7 +315,7 @@ def _server_loop(self) -> None: except OSError: break - def _handle_client(self, client_sock: socket.socket, address: tuple) -> None: + def _handle_client(self, client_sock: socket.socket, address: tuple[str, int]) -> None: """Handle a single client connection.""" try: client_sock.settimeout(5.0) @@ -545,9 +541,7 @@ def _handle_delete_object(self, seq_num: int, session_id: int) -> bytes: response += struct.pack(">I", 0) return bytes(response) - def _handle_explore( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle Explore -- return the object tree (registered data blocks).""" response = bytearray() response += struct.pack( @@ -597,9 +591,7 @@ def _handle_explore( response += struct.pack(">I", 0) return bytes(response) - def _handle_get_multi_variables( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle GetMultiVariables -- read variables from data blocks.""" response = bytearray() response += struct.pack( @@ -653,9 +645,7 @@ def _handle_get_multi_variables( response += struct.pack(">I", 0) return bytes(response) - def _handle_set_multi_variables( - self, seq_num: int, session_id: int, request_data: bytes - ) -> bytes: + def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: """Handle SetMultiVariables -- write variables to data blocks.""" response = bytearray() response += struct.pack( @@ -707,9 +697,7 @@ def _handle_set_multi_variables( response += struct.pack(">I", 0) return bytes(response) - def _build_error_response( - self, seq_num: int, session_id: int, function_code: int - ) -> bytes: + def _build_error_response(self, seq_num: int, session_id: int, function_code: int) -> bytes: """Build a generic error response for unsupported function codes.""" response = bytearray() response += struct.pack( diff --git a/snap7/s7commplus/vlq.py b/snap7/s7commplus/vlq.py index 3c739975..19e9c388 100644 --- a/snap7/s7commplus/vlq.py +++ b/snap7/s7commplus/vlq.py @@ -20,6 +20,7 @@ Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs """ + def encode_uint32_vlq(value: int) -> bytes: """Encode an unsigned 32-bit integer as VLQ. diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py index f8c8bf0d..0ae37ea6 100644 --- a/tests/test_s7commplus_e2e.py +++ b/tests/test_s7commplus_e2e.py @@ -40,7 +40,6 @@ TIA Portal so that byte offsets match the layout above. """ -import logging import os import struct import unittest @@ -49,14 +48,6 @@ from snap7.s7commplus.client import S7CommPlusClient -# Enable DEBUG logging for all s7commplus modules so we get full hex dumps -logging.basicConfig( - level=logging.DEBUG, - format="%(asctime)s %(name)s %(levelname)s %(message)s", -) -for _mod in ["snap7.s7commplus.client", "snap7.s7commplus.connection", "snap7.connection"]: - logging.getLogger(_mod).setLevel(logging.DEBUG) - # ============================================================================= # PLC Connection Configuration # These can be overridden via pytest command line options or environment variables @@ -417,191 +408,3 @@ def test_explore(self) -> None: pytest.skip(f"Explore not supported: {e}") self.assertIsInstance(data, bytes) self.assertGreater(len(data), 0) - - -@pytest.mark.e2e -class TestS7CommPlusDiagnostics(unittest.TestCase): - """Diagnostic tests for debugging protocol issues against real PLCs. - - These tests are designed to dump raw protocol data at every layer - to help diagnose why db_read/db_write fail against real hardware. - """ - - client: S7CommPlusClient - - @classmethod - def setUpClass(cls) -> None: - cls.client = S7CommPlusClient() - cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) - - @classmethod - def tearDownClass(cls) -> None: - if cls.client: - cls.client.disconnect() - - def test_diag_connection_info(self) -> None: - """Dump connection state after successful connect.""" - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: Connection Info") - print(f" connected: {self.client.connected}") - print(f" protocol_version: V{self.client.protocol_version}") - print(f" session_id: 0x{self.client.session_id:08X} ({self.client.session_id})") - print(f"{'=' * 60}") - self.assertTrue(self.client.connected) - - def test_diag_explore_raw(self) -> None: - """Explore and dump the raw response for analysis.""" - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: Explore raw response") - try: - data = self.client.explore() - print(f" Length: {len(data)} bytes") - # Dump in 32-byte rows - for i in range(0, len(data), 32): - chunk = data[i : i + 32] - hex_str = chunk.hex(" ") - ascii_str = "".join(chr(b) if 32 <= b < 127 else "." for b in chunk) - print(f" {i:04x}: {hex_str:<96s} {ascii_str}") - except Exception as e: - print(f" Explore failed: {e}") - print(f"{'=' * 60}") - - def test_diag_db_read_single_byte(self) -> None: - """Try to read a single byte from DB1 offset 0 and dump everything.""" - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: db_read(DB1, offset=0, size=1)") - try: - data = self.client.db_read(DB_READ_ONLY, 0, 1) - print(f" Success! Got {len(data)} bytes: {data.hex(' ')}") - except Exception as e: - print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'=' * 60}") - - def test_diag_db_read_full_block(self) -> None: - """Try to read the full test DB and dump everything.""" - print(f"\n{'=' * 60}") - print(f"DIAGNOSTIC: db_read(DB{DB_READ_ONLY}, offset=0, size={DB_SIZE})") - try: - data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) - print(f" Success! Got {len(data)} bytes:") - for i in range(0, len(data), 16): - chunk = data[i : i + 16] - print(f" {i:04x}: {chunk.hex(' ')}") - except Exception as e: - print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'=' * 60}") - - def test_diag_raw_get_multi_variables(self) -> None: - """Send a raw GetMultiVariables with different payload formats and dump responses. - - This tries several payload encodings to see which ones the PLC accepts. - """ - from snap7.s7commplus.protocol import FunctionCode - from snap7.s7commplus.vlq import encode_uint32_vlq - - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: Raw GetMultiVariables payload experiments") - - assert self.client._connection is not None - - # Experiment 1: Our current format (item_count + object_id + offset + size) - payloads = { - "current_format (count=1, obj=0x00010001, off=0, sz=2)": ( - encode_uint32_vlq(1) + encode_uint32_vlq(0x00010001) + encode_uint32_vlq(0) + encode_uint32_vlq(2) - ), - "empty_payload": b"", - "just_zero": encode_uint32_vlq(0), - "single_vlq_1": encode_uint32_vlq(1), - } - - for label, payload in payloads.items(): - print(f"\n --- {label} ---") - print(f" Payload ({len(payload)} bytes): {payload.hex(' ')}") - try: - response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - print(f" Response ({len(response)} bytes): {response.hex(' ')}") - - # Try to parse return code - if len(response) > 0: - from snap7.s7commplus.vlq import decode_uint32_vlq - - rc, consumed = decode_uint32_vlq(response, 0) - print(f" Return code (VLQ): {rc} (0x{rc:X})") - remaining = response[consumed:] - if remaining: - print(f" After return code ({len(remaining)} bytes): {remaining.hex(' ')}") - except Exception as e: - print(f" EXCEPTION: {type(e).__name__}: {e}") - - print(f"\n{'=' * 60}") - - def test_diag_raw_set_variable(self) -> None: - """Try SetVariable (0x04F2) instead of SetMultiVariables to see if PLC responds differently.""" - from snap7.s7commplus.protocol import FunctionCode - - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: Raw SetVariable / GetVariable experiments") - - assert self.client._connection is not None - - function_codes = { - "GET_VARIABLE (0x04FC)": FunctionCode.GET_VARIABLE, - "GET_MULTI_VARIABLES (0x054C)": FunctionCode.GET_MULTI_VARIABLES, - "SET_VARIABLE (0x04F2)": FunctionCode.SET_VARIABLE, - } - - # Simple payload: just try empty or minimal - for label, fc in function_codes.items(): - print(f"\n --- {label} with empty payload ---") - try: - response = self.client._connection.send_request(fc, b"") - print(f" Response ({len(response)} bytes): {response.hex(' ')}") - except Exception as e: - print(f" EXCEPTION: {type(e).__name__}: {e}") - - print(f"\n{'=' * 60}") - - def test_diag_explore_then_read(self) -> None: - """Explore first to discover object IDs, then try reading using those IDs.""" - from snap7.s7commplus.protocol import FunctionCode, ElementID - from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq - - print(f"\n{'=' * 60}") - print("DIAGNOSTIC: Explore -> extract object IDs -> try reading") - - assert self.client._connection is not None - - try: - explore_data = self.client._connection.send_request(FunctionCode.EXPLORE, b"") - print(f" Explore response ({len(explore_data)} bytes)") - - # Scan for StartOfObject markers and extract relation IDs - object_ids = [] - i = 0 - while i < len(explore_data): - if explore_data[i] == ElementID.START_OF_OBJECT: - if i + 5 <= len(explore_data): - rel_id = struct.unpack_from(">I", explore_data, i + 1)[0] - object_ids.append(rel_id) - print(f" Found object at offset {i}: relation_id=0x{rel_id:08X}") - i += 5 - else: - i += 1 - - # Try reading using each discovered object ID - for obj_id in object_ids[:5]: # Limit to first 5 - print(f"\n --- Read using object_id=0x{obj_id:08X} ---") - payload = encode_uint32_vlq(1) + encode_uint32_vlq(obj_id) + encode_uint32_vlq(0) + encode_uint32_vlq(4) - try: - response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - print(f" Response ({len(response)} bytes): {response.hex(' ')}") - if len(response) > 0: - rc, consumed = decode_uint32_vlq(response, 0) - print(f" Return code: {rc} (0x{rc:X})") - except Exception as e: - print(f" EXCEPTION: {type(e).__name__}: {e}") - - except Exception as e: - print(f" Explore failed: {type(e).__name__}: {e}") - - print(f"\n{'=' * 60}") diff --git a/tests/test_s7commplus_server.py b/tests/test_s7commplus_server.py index 356bd6f0..2f08f575 100644 --- a/tests/test_s7commplus_server.py +++ b/tests/test_s7commplus_server.py @@ -2,6 +2,8 @@ import struct import time +from collections.abc import Generator + import pytest import asyncio @@ -15,7 +17,7 @@ @pytest.fixture() -def server(): +def server() -> Generator[S7CommPlusServer, None, None]: """Create and start an S7CommPlus server with test data blocks.""" srv = S7CommPlusServer() @@ -294,7 +296,7 @@ async def test_concurrent_reads(self, server: S7CommPlusServer) -> None: async def read_temp() -> float: data = await client.db_read(1, 0, 4) - return struct.unpack(">f", data)[0] + return float(struct.unpack(">f", data)[0]) results = await asyncio.gather(read_temp(), read_temp(), read_temp()) assert len(results) == 3 From 38fb46b60af146333d271f6311a47fa3866e3ff3 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Thu, 5 Mar 2026 20:06:59 +0200 Subject: [PATCH 19/27] Enhance S7CommPlus connection with variable-length TSAP support and async client improvements Support bytes-type remote TSAP (e.g. "SIMATIC-ROOT-HMI") in ISOTCPConnection, extend S7CommPlus protocol handling, and improve async client and server emulator. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 98 ++++++++++++++--- snap7/s7commplus/client.py | 5 - snap7/s7commplus/connection.py | 176 +++++++++++++++++++++++++------ snap7/s7commplus/protocol.py | 22 ++++ snap7/s7commplus/server.py | 27 ++++- 5 files changed, 278 insertions(+), 50 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index b3eb751d..fd53562b 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -17,8 +17,17 @@ import struct from typing import Any, Optional -from .protocol import FunctionCode, Opcode, ProtocolVersion -from .codec import encode_header, decode_header +from .protocol import ( + DataType, + ElementID, + FunctionCode, + ObjectId, + Opcode, + ProtocolVersion, + S7COMMPLUS_LOCAL_TSAP, + S7COMMPLUS_REMOTE_TSAP, +) +from .codec import encode_header, decode_header, encode_typed_value from .vlq import encode_uint32_vlq, decode_uint32_vlq logger = logging.getLogger(__name__) @@ -74,15 +83,15 @@ async def connect( rack: PLC rack number slot: PLC slot number """ - local_tsap = 0x0100 - remote_tsap = 0x0100 | (rack << 5) | slot - # TCP connect self._reader, self._writer = await asyncio.open_connection(host, port) try: - # COTP handshake - await self._cotp_connect(local_tsap, remote_tsap) + # COTP handshake with S7CommPlus TSAP values + await self._cotp_connect(S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP) + + # InitSSL handshake + await self._init_ssl() # S7CommPlus session setup await self._create_session() @@ -251,19 +260,20 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: ) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed:] + response = response_data[consumed : consumed + data_length] if len(response) < 14: raise RuntimeError("Response too short") return response[14:] - async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: + async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: """Perform COTP Connection Request / Confirm handshake.""" if self._writer is None or self._reader is None: raise RuntimeError("Not connected") @@ -271,7 +281,7 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: # Build COTP CR base_pdu = struct.pack(">BBHHB", 6, _COTP_CR, 0x0000, 0x0001, 0x00) calling_tsap = struct.pack(">BBH", 0xC1, 2, local_tsap) - called_tsap = struct.pack(">BBH", 0xC2, 2, remote_tsap) + called_tsap = struct.pack(">BB", 0xC2, len(remote_tsap)) + remote_tsap pdu_size_param = struct.pack(">BBB", 0xC0, 1, 0x0A) params = calling_tsap + called_tsap + pdu_size_param @@ -290,10 +300,40 @@ async def _cotp_connect(self, local_tsap: int, remote_tsap: int) -> None: if len(payload) < 7 or payload[1] != _COTP_CC: raise RuntimeError(f"Expected COTP CC, got {payload[1]:#04x}") + async def _init_ssl(self) -> None: + """Send InitSSL request (required before CreateObject).""" + seq_num = self._next_sequence_number() + + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.INIT_SSL, + 0x0000, + seq_num, + 0x00000000, + 0x30, # Transport flags for InitSSL + ) + request += struct.pack(">I", 0) + + frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + await self._send_cotp_dt(frame) + + response_data = await self._recv_cotp_dt() + version, data_length, consumed = decode_header(response_data) + response = response_data[consumed : consumed + data_length] + + if len(response) < 14: + raise RuntimeError("InitSSL response too short") + + logger.debug(f"InitSSL response received, version=V{version}") + async def _create_session(self) -> None: """Send CreateObject to establish S7CommPlus session.""" seq_num = self._next_sequence_number() + # Build CreateObject request header request = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -301,17 +341,50 @@ async def _create_session(self) -> None: FunctionCode.CREATE_OBJECT, 0x0000, seq_num, - 0x00000000, + ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 0x36, ) + + # RequestId: ObjectServerSessionContainer (285) + request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) + + # RequestValue: ValueUDInt(0) + request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + + # Unknown padding + request += struct.pack(">I", 0) + + # RequestObject: NullServerSession PObject + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) + request += encode_uint32_vlq(0) # ClassFlags + request += encode_uint32_vlq(0) # AttributeId + + # Attribute: ServerSessionClientRID = 0x80c3c901 + request += bytes([ElementID.ATTRIBUTE]) + request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) + request += encode_typed_value(DataType.RID, 0x80C3C901) + + # Nested: ClassSubscriptions + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) + request += encode_uint32_vlq(0) + request += encode_uint32_vlq(0) + request += bytes([ElementID.TERMINATING_OBJECT]) + + request += bytes([ElementID.TERMINATING_OBJECT]) request += struct.pack(">I", 0) + # Frame header + trailer frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) await self._send_cotp_dt(frame) response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) - response = response_data[consumed:] + response = response_data[consumed : consumed + data_length] if len(response) < 14: raise RuntimeError("CreateObject response too short") @@ -336,6 +409,7 @@ async def _delete_session(self) -> None: request += struct.pack(">I", 0) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) try: diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index ad38c860..a54822f8 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -93,14 +93,9 @@ def connect( tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) """ - local_tsap = 0x0100 - remote_tsap = 0x0100 | (rack << 5) | slot - self._connection = S7CommPlusConnection( host=host, port=port, - local_tsap=local_tsap, - remote_tsap=remote_tsap, ) self._connection.connect( diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index c425810f..77fbaa88 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -15,19 +15,25 @@ Connection sequence (all versions):: 1. TCP connect to port 102 - 2. COTP Connection Request / Confirm (same as legacy S7comm) - 3. S7CommPlus CreateObject request (NullServer session setup) - 4. PLC responds with CreateObject response containing: + 2. COTP Connection Request / Confirm + - Local TSAP: 0x0600 + - Remote TSAP: "SIMATIC-ROOT-HMI" (16-byte ASCII string) + 3. InitSSL request / response (unencrypted) + 4. TLS activation (for V3/TLS PLCs) + 5. S7CommPlus CreateObject request (NullServer session setup) + - SessionId = ObjectNullServerSession (288) + - Proper PObject tree with ServerSession class + 6. PLC responds with CreateObject response containing: - Protocol version (V1/V2/V3) - Session ID - Server session challenge (V2/V3) -Version-specific authentication after step 4:: +Version-specific authentication after step 6:: - V1: Simple challenge-response handshake + V1: No further authentication needed V2: Session key derivation and integrity checking V3 (no TLS): Public-key key exchange - V3 (TLS): InitSsl request -> TLS 1.3 handshake over TPKT/COTP tunnel + V3 (TLS): TLS 1.3 handshake is already done in step 4 Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ @@ -39,8 +45,18 @@ from types import TracebackType from ..connection import ISOTCPConnection -from .protocol import FunctionCode, Opcode, ProtocolVersion -from .codec import encode_header, decode_header +from .protocol import ( + FunctionCode, + Opcode, + ProtocolVersion, + ElementID, + ObjectId, + S7COMMPLUS_LOCAL_TSAP, + S7COMMPLUS_REMOTE_TSAP, +) +from .codec import encode_header, decode_header, encode_typed_value +from .vlq import encode_uint32_vlq +from .protocol import DataType logger = logging.getLogger(__name__) @@ -62,19 +78,15 @@ def __init__( self, host: str, port: int = 102, - local_tsap: int = 0x0100, - remote_tsap: int = 0x0102, ): self.host = host self.port = port - self.local_tsap = local_tsap - self.remote_tsap = remote_tsap self._iso_conn = ISOTCPConnection( host=host, port=port, - local_tsap=local_tsap, - remote_tsap=remote_tsap, + local_tsap=S7COMMPLUS_LOCAL_TSAP, + remote_tsap=S7COMMPLUS_REMOTE_TSAP, ) self._ssl_context: Optional[ssl.SSLContext] = None @@ -127,21 +139,31 @@ def connect( tls_ca: Path to CA certificate for PLC verification (PEM) """ try: - # Step 1: COTP connection + # Step 1: COTP connection (same TSAP for all S7CommPlus versions) self._iso_conn.connect(timeout) - # Step 2: CreateObject (S7CommPlus session setup) + # Step 2: InitSSL handshake (required before CreateObject) + self._init_ssl() + + # Step 3: TLS activation (required for modern firmware) + if use_tls: + # TODO: Perform TLS 1.3 handshake over the existing COTP connection + raise NotImplementedError("TLS activation is not yet implemented. Use use_tls=False for V1 connections.") + + # Step 4: CreateObject (S7CommPlus session setup) self._create_session() - # Step 3: Version-specific authentication - if use_tls and self._protocol_version >= ProtocolVersion.V3: - # TODO: Send InitSsl request and perform TLS handshake - raise NotImplementedError("TLS authentication is not yet implemented. Use use_tls=False for V1 connections.") + # Step 5: Version-specific authentication + if self._protocol_version >= ProtocolVersion.V3: + if not use_tls: + logger.warning( + "PLC reports V3 protocol but TLS is not enabled. Connection may not work without use_tls=True." + ) elif self._protocol_version == ProtocolVersion.V2: # TODO: Proprietary HMAC-SHA256/AES session auth raise NotImplementedError("V2 authentication is not yet implemented.") - # V1: No further authentication needed + # V1: No further authentication needed after CreateObject self._connected = True logger.info( f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" @@ -198,16 +220,17 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: + payload ) - # Add S7CommPlus frame header and send + # Add S7CommPlus frame header and trailer, then send frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() - # Parse frame header + # Parse frame header, use data_length to exclude trailer version, data_length, consumed = decode_header(response_frame) - response = response_frame[consumed:] + response = response_frame[consumed : consumed + data_length] if len(response) < 14: from ..error import S7ConnectionError @@ -216,11 +239,64 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: return response[14:] + def _init_ssl(self) -> None: + """Send InitSSL request to prepare the connection. + + This is the first S7CommPlus message sent after COTP connect. + The PLC responds with an InitSSL response. For PLCs that support + TLS, the caller should then activate TLS before sending CreateObject. + For V1 PLCs without TLS, the response may indicate that TLS is + not supported, but the connection can continue without it. + + Reference: thomas-v2/S7CommPlusDriver InitSslRequest + """ + seq_num = self._next_sequence_number() + + # InitSSL request: header + padding + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + FunctionCode.INIT_SSL, + 0x0000, # Reserved + seq_num, + 0x00000000, # No session yet + 0x30, # Transport flags (0x30 for InitSSL) + ) + # Trailing padding + request += struct.pack(">I", 0) + + # Wrap in S7CommPlus frame header + trailer + frame = encode_header(ProtocolVersion.V1, len(request)) + request + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + + self._iso_conn.send_data(frame) + + # Receive InitSSL response + response_frame = self._iso_conn.receive_data() + + # Parse S7CommPlus frame header + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed:] + + if len(response) < 14: + from ..error import S7ConnectionError + + raise S7ConnectionError("InitSSL response too short") + + logger.debug(f"InitSSL response received, version=V{version}") + def _create_session(self) -> None: - """Send CreateObject request to establish an S7CommPlus session.""" + """Send CreateObject request to establish an S7CommPlus session. + + Builds a NullServerSession CreateObject request matching the + structure expected by S7-1200/1500 PLCs: + + Reference: thomas-v2/S7CommPlusDriver CreateObjectRequest.SetNullServerSessionData() + """ seq_num = self._next_sequence_number() - # Build CreateObject request with NullServer session data + # Build CreateObject request header request = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -228,15 +304,54 @@ def _create_session(self) -> None: FunctionCode.CREATE_OBJECT, 0x0000, seq_num, - 0x00000000, # No session yet - 0x36, + ObjectId.OBJECT_NULL_SERVER_SESSION, # SessionId = 288 for initial setup + 0x36, # Transport flags ) - # Add empty request data (minimal CreateObject) + # RequestId: ObjectServerSessionContainer (285) + request += struct.pack(">I", ObjectId.OBJECT_SERVER_SESSION_CONTAINER) + + # RequestValue: ValueUDInt(0) = DatatypeFlags(0x00) + Datatype.UDInt(0x04) + VLQ(0) + request += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + + # Unknown padding (always 0) + request += struct.pack(">I", 0) + + # RequestObject: PObject for NullServerSession + # StartOfObject + request += bytes([ElementID.START_OF_OBJECT]) + # RelationId: GetNewRIDOnServer (211) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + # ClassId: ClassServerSession (287), VLQ encoded + request += encode_uint32_vlq(ObjectId.CLASS_SERVER_SESSION) + # ClassFlags: 0 + request += encode_uint32_vlq(0) + # AttributeId: None (0) + request += encode_uint32_vlq(0) + + # Attribute: ServerSessionClientRID (300) = RID 0x80c3c901 + request += bytes([ElementID.ATTRIBUTE]) + request += encode_uint32_vlq(ObjectId.SERVER_SESSION_CLIENT_RID) + request += encode_typed_value(DataType.RID, 0x80C3C901) + + # Nested object: ClassSubscriptions + request += bytes([ElementID.START_OF_OBJECT]) + request += struct.pack(">I", ObjectId.GET_NEW_RID_ON_SERVER) + request += encode_uint32_vlq(ObjectId.CLASS_SUBSCRIPTIONS) + request += encode_uint32_vlq(0) # ClassFlags + request += encode_uint32_vlq(0) # AttributeId + request += bytes([ElementID.TERMINATING_OBJECT]) + + # End outer object + request += bytes([ElementID.TERMINATING_OBJECT]) + + # Trailing padding request += struct.pack(">I", 0) - # Wrap in S7CommPlus frame header + # Wrap in S7CommPlus frame header + trailer frame = encode_header(ProtocolVersion.V1, len(request)) + request + # S7CommPlus trailer (end-of-frame marker) + frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) self._iso_conn.send_data(frame) @@ -275,6 +390,7 @@ def _delete_session(self) -> None: request += struct.pack(">I", 0) frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) self._iso_conn.send_data(frame) # Best-effort receive diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 9ec4ec53..cf49df53 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -86,6 +86,28 @@ class ElementID(IntEnum): VARNAME_LIST = 0xAC +class ObjectId(IntEnum): + """Well-known object IDs used in session establishment. + + Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs + """ + + NONE = 0 + GET_NEW_RID_ON_SERVER = 211 + CLASS_SUBSCRIPTIONS = 255 + CLASS_SERVER_SESSION_CONTAINER = 284 + OBJECT_SERVER_SESSION_CONTAINER = 285 + CLASS_SERVER_SESSION = 287 + OBJECT_NULL_SERVER_SESSION = 288 + SERVER_SESSION_CLIENT_RID = 300 + + +# Default TSAP for S7CommPlus connections +# The remote TSAP is the ASCII string "SIMATIC-ROOT-HMI" (16 bytes) +S7COMMPLUS_LOCAL_TSAP = 0x0600 +S7COMMPLUS_REMOTE_TSAP = b"SIMATIC-ROOT-HMI" + + class DataType(IntEnum): """S7CommPlus wire data types. diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index f4b827aa..b40b587e 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -428,8 +428,9 @@ def _recv_s7commplus_frame(self, sock: socket.socket) -> Optional[bytes]: def _send_s7commplus_frame(self, sock: socket.socket, data: bytes) -> None: """Send an S7CommPlus frame wrapped in TPKT/COTP.""" - # S7CommPlus header (4 bytes) + data + # S7CommPlus header (4 bytes) + data + trailer (4 bytes) s7plus_frame = encode_header(self._protocol_version, len(data)) + data + s7plus_frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) # COTP DT header cotp_dt = struct.pack(">BBB", 2, 0xF0, 0x80) + s7plus_frame @@ -449,7 +450,8 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: except ValueError: return None - payload = data[consumed:] + # Use data_length to exclude any trailer + payload = data[consumed : consumed + data_length] if len(payload) < 14: return None @@ -463,7 +465,9 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: req_session_id = struct.unpack_from(">I", payload, 9)[0] request_data = payload[14:] - if function_code == FunctionCode.CREATE_OBJECT: + if function_code == FunctionCode.INIT_SSL: + return self._handle_init_ssl(seq_num) + elif function_code == FunctionCode.CREATE_OBJECT: return self._handle_create_object(seq_num, request_data) elif function_code == FunctionCode.DELETE_OBJECT: return self._handle_delete_object(seq_num, req_session_id) @@ -476,6 +480,23 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: else: return self._build_error_response(seq_num, req_session_id, function_code) + def _handle_init_ssl(self, seq_num: int) -> bytes: + """Handle InitSSL -- respond to SSL initialization (V1 emulation, no real TLS).""" + response = bytearray() + response += struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + FunctionCode.INIT_SSL, + 0x0000, + seq_num, + 0x00000000, + 0x00, # Transport flags + ) + response += encode_uint32_vlq(0) # Return code: success + response += struct.pack(">I", 0) + return bytes(response) + def _handle_create_object(self, seq_num: int, request_data: bytes) -> bytes: """Handle CreateObject -- establish a session.""" with self._lock: From 607b169c216f17087765dc8139d9584fdd9d8719 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 6 Mar 2026 09:04:38 +0200 Subject: [PATCH 20/27] Add extensive debug logging to S7CommPlus protocol stack for real PLC diagnostics Adds hex dumps and detailed parsing at every protocol layer (ISO-TCP, S7CommPlus connection, client) plus 6 new diagnostic e2e tests that probe different payload formats and function codes against real hardware. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/client.py | 57 ++++++++- snap7/s7commplus/connection.py | 77 +++++++++--- tests/test_s7commplus_e2e.py | 210 +++++++++++++++++++++++++++++++++ 3 files changed, 323 insertions(+), 21 deletions(-) diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index a54822f8..2b0d2b0d 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -135,32 +135,53 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) + logger.debug( + f"db_read: db={db_number} start={start} size={size} " + f"object_id=0x{object_id:08X} payload={bytes(payload).hex(' ')}" + ) + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_read: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response offset = 0 # Skip return code - _, consumed = decode_uint32_vlq(response, offset) + return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: return_code={return_code} (consumed {consumed} bytes)") offset += consumed # Item count item_count, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: item_count={item_count} (consumed {consumed} bytes)") offset += consumed if item_count == 0: + logger.debug("db_read: no items returned") return b"" # First item: status + data_length + data status, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: item status={status} (consumed {consumed} bytes)") offset += consumed data_length, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read: data_length={data_length} (consumed {consumed} bytes)") offset += consumed if status != 0: + logger.error( + f"db_read: FAILED status={status}, remaining bytes: {response[offset:].hex(' ')}" + ) raise RuntimeError(f"Read failed with status {status}") - return response[offset : offset + data_length] + result = response[offset : offset + data_length] + logger.debug(f"db_read: result ({len(result)} bytes): {result.hex(' ')}") + remaining = response[offset + data_length :] + if remaining: + logger.debug(f"db_read: remaining after data ({len(remaining)} bytes): {remaining.hex(' ')}") + + return result def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -181,14 +202,25 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload += encode_uint32_vlq(len(data)) payload += data + logger.debug( + f"db_write: db={db_number} start={start} data_len={len(data)} " + f"object_id=0x{object_id:08X} data={data.hex(' ')} payload={bytes(payload).hex(' ')}" + ) + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_write: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response - check return code offset = 0 return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_write: return_code={return_code} (consumed {consumed} bytes)") offset += consumed if return_code != 0: + logger.error( + f"db_write: FAILED return_code={return_code}, remaining: {response[offset:].hex(' ')}" + ) raise RuntimeError(f"Write failed with return code {return_code}") def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: @@ -211,28 +243,39 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: payload += encode_uint32_vlq(start) payload += encode_uint32_vlq(size) + logger.debug(f"db_read_multi: {len(items)} items: {items} payload={bytes(payload).hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") + # Parse response offset = 0 - _, consumed = decode_uint32_vlq(response, offset) + return_code, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read_multi: return_code={return_code} (consumed {consumed} bytes)") offset += consumed item_count, consumed = decode_uint32_vlq(response, offset) + logger.debug(f"db_read_multi: item_count={item_count} (consumed {consumed} bytes)") offset += consumed results: list[bytes] = [] - for _ in range(item_count): + for i in range(item_count): status, consumed = decode_uint32_vlq(response, offset) offset += consumed data_length, consumed = decode_uint32_vlq(response, offset) offset += consumed + logger.debug(f"db_read_multi: item[{i}] status={status} data_length={data_length}") + if status == 0 and data_length > 0: - results.append(response[offset : offset + data_length]) + item_data = response[offset : offset + data_length] + logger.debug(f"db_read_multi: item[{i}] data: {item_data.hex(' ')}") + results.append(item_data) offset += data_length else: + logger.debug(f"db_read_multi: item[{i}] empty/error") results.append(b"") return results @@ -251,7 +294,9 @@ def explore(self) -> bytes: if self._connection is None: raise RuntimeError("Not connected") - return self._connection.send_request(FunctionCode.EXPLORE, b"") + response = self._connection.send_request(FunctionCode.EXPLORE, b"") + logger.debug(f"explore: response ({len(response)} bytes): {response.hex(' ')}") + return response # -- Context manager -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 77fbaa88..e3ba388a 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -206,38 +206,67 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: seq_num = self._next_sequence_number() # Build request header - request = ( - struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, # Reserved - function_code, - 0x0000, # Reserved - seq_num, - self._session_id, - 0x36, # Transport flags - ) - + payload + request_header = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, # Reserved + function_code, + 0x0000, # Reserved + seq_num, + self._session_id, + 0x36, # Transport flags + ) + request = request_header + payload + + logger.debug( + f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}" ) + logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") + logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") # Add S7CommPlus frame header and trailer, then send frame = encode_header(self._protocol_version, len(request)) + request frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) + + logger.debug(f" Full frame ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== RECV RESPONSE === raw frame ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse frame header, use data_length to exclude trailer version, data_length, consumed = decode_header(response_frame) + logger.debug(f" Frame header: version=V{version}, data_length={data_length}, header_size={consumed}") + response = response_frame[consumed : consumed + data_length] + logger.debug(f" Response data ({len(response)} bytes): {response.hex(' ')}") if len(response) < 14: from ..error import S7ConnectionError raise S7ConnectionError("Response too short") - return response[14:] + # Parse response header for debug + resp_opcode = response[0] + resp_func = struct.unpack_from(">H", response, 3)[0] + resp_seq = struct.unpack_from(">H", response, 7)[0] + resp_session = struct.unpack_from(">I", response, 9)[0] + resp_transport = response[13] + logger.debug( + f" Response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " + f"seq={resp_seq} session=0x{resp_session:08X} transport=0x{resp_transport:02X}" + ) + + resp_payload = response[14:] + logger.debug(f" Response payload ({len(resp_payload)} bytes): {resp_payload.hex(' ')}") + + # Check for trailer bytes after data_length + trailer = response_frame[consumed + data_length :] + if trailer: + logger.debug(f" Trailer ({len(trailer)} bytes): {trailer.hex(' ')}") + + return resp_payload def _init_ssl(self) -> None: """Send InitSSL request to prepare the connection. @@ -270,10 +299,12 @@ def _init_ssl(self) -> None: frame = encode_header(ProtocolVersion.V1, len(request)) + request frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + logger.debug(f"=== InitSSL === sending ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive InitSSL response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== InitSSL === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse S7CommPlus frame header version, data_length, consumed = decode_header(response_frame) @@ -284,7 +315,8 @@ def _init_ssl(self) -> None: raise S7ConnectionError("InitSSL response too short") - logger.debug(f"InitSSL response received, version=V{version}") + logger.debug(f"InitSSL response: version=V{version}, data_length={data_length}") + logger.debug(f"InitSSL response body ({len(response)} bytes): {response.hex(' ')}") def _create_session(self) -> None: """Send CreateObject request to establish an S7CommPlus session. @@ -353,15 +385,20 @@ def _create_session(self) -> None: # S7CommPlus trailer (end-of-frame marker) frame += struct.pack(">BBH", 0x72, ProtocolVersion.V1, 0x0000) + logger.debug(f"=== CreateObject === sending ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) # Receive response response_frame = self._iso_conn.receive_data() + logger.debug(f"=== CreateObject === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") # Parse S7CommPlus frame header version, data_length, consumed = decode_header(response_frame) response = response_frame[consumed:] + logger.debug(f"CreateObject response: version=V{version}, data_length={data_length}") + logger.debug(f"CreateObject response body ({len(response)} bytes): {response.hex(' ')}") + if len(response) < 14: from ..error import S7ConnectionError @@ -371,7 +408,17 @@ def _create_session(self) -> None: self._session_id = struct.unpack_from(">I", response, 9)[0] self._protocol_version = version - logger.debug(f"Session created: id={self._session_id}, version=V{version}") + # Parse and log the full response header + resp_opcode = response[0] + resp_func = struct.unpack_from(">H", response, 3)[0] + resp_seq = struct.unpack_from(">H", response, 7)[0] + resp_transport = response[13] + logger.debug( + f"CreateObject response header: opcode=0x{resp_opcode:02X} function=0x{resp_func:04X} " + f"seq={resp_seq} session=0x{self._session_id:08X} transport=0x{resp_transport:02X}" + ) + logger.debug(f"CreateObject response payload: {response[14:].hex(' ')}") + logger.debug(f"Session created: id=0x{self._session_id:08X} ({self._session_id}), version=V{version}") def _delete_session(self) -> None: """Send DeleteObject to close the session.""" diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py index 0ae37ea6..46da4b05 100644 --- a/tests/test_s7commplus_e2e.py +++ b/tests/test_s7commplus_e2e.py @@ -40,6 +40,7 @@ TIA Portal so that byte offsets match the layout above. """ +import logging import os import struct import unittest @@ -48,6 +49,14 @@ from snap7.s7commplus.client import S7CommPlusClient +# Enable DEBUG logging for all s7commplus modules so we get full hex dumps +logging.basicConfig( + level=logging.DEBUG, + format="%(asctime)s %(name)s %(levelname)s %(message)s", +) +for _mod in ["snap7.s7commplus.client", "snap7.s7commplus.connection", "snap7.connection"]: + logging.getLogger(_mod).setLevel(logging.DEBUG) + # ============================================================================= # PLC Connection Configuration # These can be overridden via pytest command line options or environment variables @@ -408,3 +417,204 @@ def test_explore(self) -> None: pytest.skip(f"Explore not supported: {e}") self.assertIsInstance(data, bytes) self.assertGreater(len(data), 0) + + +@pytest.mark.e2e +class TestS7CommPlusDiagnostics(unittest.TestCase): + """Diagnostic tests for debugging protocol issues against real PLCs. + + These tests are designed to dump raw protocol data at every layer + to help diagnose why db_read/db_write fail against real hardware. + """ + + client: S7CommPlusClient + + @classmethod + def setUpClass(cls) -> None: + cls.client = S7CommPlusClient() + cls.client.connect(PLC_IP, PLC_PORT, PLC_RACK, PLC_SLOT) + + @classmethod + def tearDownClass(cls) -> None: + if cls.client: + cls.client.disconnect() + + def test_diag_connection_info(self) -> None: + """Dump connection state after successful connect.""" + print(f"\n{'='*60}") + print(f"DIAGNOSTIC: Connection Info") + print(f" connected: {self.client.connected}") + print(f" protocol_version: V{self.client.protocol_version}") + print(f" session_id: 0x{self.client.session_id:08X} ({self.client.session_id})") + print(f"{'='*60}") + self.assertTrue(self.client.connected) + + def test_diag_explore_raw(self) -> None: + """Explore and dump the raw response for analysis.""" + print(f"\n{'='*60}") + print("DIAGNOSTIC: Explore raw response") + try: + data = self.client.explore() + print(f" Length: {len(data)} bytes") + # Dump in 32-byte rows + for i in range(0, len(data), 32): + chunk = data[i : i + 32] + hex_str = chunk.hex(" ") + ascii_str = "".join(chr(b) if 32 <= b < 127 else "." for b in chunk) + print(f" {i:04x}: {hex_str:<96s} {ascii_str}") + except Exception as e: + print(f" Explore failed: {e}") + print(f"{'='*60}") + + def test_diag_db_read_single_byte(self) -> None: + """Try to read a single byte from DB1 offset 0 and dump everything.""" + print(f"\n{'='*60}") + print("DIAGNOSTIC: db_read(DB1, offset=0, size=1)") + try: + data = self.client.db_read(DB_READ_ONLY, 0, 1) + print(f" Success! Got {len(data)} bytes: {data.hex(' ')}") + except Exception as e: + print(f" FAILED: {type(e).__name__}: {e}") + print(f"{'='*60}") + + def test_diag_db_read_full_block(self) -> None: + """Try to read the full test DB and dump everything.""" + print(f"\n{'='*60}") + print(f"DIAGNOSTIC: db_read(DB{DB_READ_ONLY}, offset=0, size={DB_SIZE})") + try: + data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) + print(f" Success! Got {len(data)} bytes:") + for i in range(0, len(data), 16): + chunk = data[i : i + 16] + print(f" {i:04x}: {chunk.hex(' ')}") + except Exception as e: + print(f" FAILED: {type(e).__name__}: {e}") + print(f"{'='*60}") + + def test_diag_raw_get_multi_variables(self) -> None: + """Send a raw GetMultiVariables with different payload formats and dump responses. + + This tries several payload encodings to see which ones the PLC accepts. + """ + from snap7.s7commplus.protocol import FunctionCode + from snap7.s7commplus.vlq import encode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Raw GetMultiVariables payload experiments") + + assert self.client._connection is not None + + # Experiment 1: Our current format (item_count + object_id + offset + size) + payloads = { + "current_format (count=1, obj=0x00010001, off=0, sz=2)": ( + encode_uint32_vlq(1) + + encode_uint32_vlq(0x00010001) + + encode_uint32_vlq(0) + + encode_uint32_vlq(2) + ), + "empty_payload": b"", + "just_zero": encode_uint32_vlq(0), + "single_vlq_1": encode_uint32_vlq(1), + } + + for label, payload in payloads.items(): + print(f"\n --- {label} ---") + print(f" Payload ({len(payload)} bytes): {payload.hex(' ')}") + try: + response = self.client._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, payload + ) + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + + # Try to parse return code + if len(response) > 0: + from snap7.s7commplus.vlq import decode_uint32_vlq + + rc, consumed = decode_uint32_vlq(response, 0) + print(f" Return code (VLQ): {rc} (0x{rc:X})") + remaining = response[consumed:] + if remaining: + print(f" After return code ({len(remaining)} bytes): {remaining.hex(' ')}") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") + + def test_diag_raw_set_variable(self) -> None: + """Try SetVariable (0x04F2) instead of SetMultiVariables to see if PLC responds differently.""" + from snap7.s7commplus.protocol import FunctionCode + from snap7.s7commplus.vlq import encode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Raw SetVariable / GetVariable experiments") + + assert self.client._connection is not None + + function_codes = { + "GET_VARIABLE (0x04FC)": FunctionCode.GET_VARIABLE, + "GET_MULTI_VARIABLES (0x054C)": FunctionCode.GET_MULTI_VARIABLES, + "SET_VARIABLE (0x04F2)": FunctionCode.SET_VARIABLE, + } + + # Simple payload: just try empty or minimal + for label, fc in function_codes.items(): + print(f"\n --- {label} with empty payload ---") + try: + response = self.client._connection.send_request(fc, b"") + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") + + def test_diag_explore_then_read(self) -> None: + """Explore first to discover object IDs, then try reading using those IDs.""" + from snap7.s7commplus.protocol import FunctionCode, ElementID + from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq + + print(f"\n{'='*60}") + print("DIAGNOSTIC: Explore -> extract object IDs -> try reading") + + assert self.client._connection is not None + + try: + explore_data = self.client._connection.send_request(FunctionCode.EXPLORE, b"") + print(f" Explore response ({len(explore_data)} bytes)") + + # Scan for StartOfObject markers and extract relation IDs + object_ids = [] + i = 0 + while i < len(explore_data): + if explore_data[i] == ElementID.START_OF_OBJECT: + if i + 5 <= len(explore_data): + rel_id = struct.unpack_from(">I", explore_data, i + 1)[0] + object_ids.append(rel_id) + print(f" Found object at offset {i}: relation_id=0x{rel_id:08X}") + i += 5 + else: + i += 1 + + # Try reading using each discovered object ID + for obj_id in object_ids[:5]: # Limit to first 5 + print(f"\n --- Read using object_id=0x{obj_id:08X} ---") + payload = ( + encode_uint32_vlq(1) + + encode_uint32_vlq(obj_id) + + encode_uint32_vlq(0) + + encode_uint32_vlq(4) + ) + try: + response = self.client._connection.send_request( + FunctionCode.GET_MULTI_VARIABLES, payload + ) + print(f" Response ({len(response)} bytes): {response.hex(' ')}") + if len(response) > 0: + rc, consumed = decode_uint32_vlq(response, 0) + print(f" Return code: {rc} (0x{rc:X})") + except Exception as e: + print(f" EXCEPTION: {type(e).__name__}: {e}") + + except Exception as e: + print(f" Explore failed: {type(e).__name__}: {e}") + + print(f"\n{'='*60}") From d78b0ebe822f567417ee7271e5e34d6f8183036d Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 6 Mar 2026 10:14:47 +0200 Subject: [PATCH 21/27] Fix S7CommPlus wire format for real PLC compatibility Rewrite client payload encoding/decoding to use the correct S7CommPlus protocol format with ItemAddress structures (SymbolCrc, AccessArea, AccessSubArea, LIDs), ObjectQualifier, and proper PValue response parsing. Previously the client used a simplified custom format that only worked with the emulated server, causing ERROR2 responses from real S7-1200/1500 PLCs. - client.py: Correct GetMultiVariables/SetMultiVariables request format - async_client.py: Reuse corrected payload builders from client.py - codec.py: Add ItemAddress, ObjectQualifier, PValue encode/decode - protocol.py: Add Ids constants (DB_ACCESS_AREA_BASE, etc.) - server.py: Update to parse/generate the corrected wire format Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 88 ++------ snap7/s7commplus/client.py | 331 ++++++++++++++++++++----------- snap7/s7commplus/codec.py | 205 ++++++++++++++++++- snap7/s7commplus/protocol.py | 27 +++ snap7/s7commplus/server.py | 285 +++++++++++++++++++------- 5 files changed, 680 insertions(+), 256 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index fd53562b..41780192 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -28,7 +28,8 @@ S7COMMPLUS_REMOTE_TSAP, ) from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .vlq import encode_uint32_vlq +from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response logger = logging.getLogger(__name__) @@ -137,33 +138,15 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) + payload = _build_read_payload([(db_number, start, size)]) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - _, consumed = decode_uint32_vlq(response, offset) - offset += consumed - item_count, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - if item_count == 0: - return b"" - - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - if status != 0: - raise RuntimeError(f"Read failed with status {status}") - - return response[offset : offset + data_length] + results = _parse_read_response(response) + if not results: + raise RuntimeError("Read returned no data") + if results[0] is None: + raise RuntimeError("Read failed: PLC returned error for item") + return results[0] async def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -173,20 +156,9 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: start: Start byte offset data: Bytes to write """ - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(len(data)) - payload += data - - response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - if return_code != 0: - raise RuntimeError(f"Write failed with return code {return_code}") + payload = _build_write_payload([(db_number, start, data)]) + response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, payload) + _parse_write_response(response) async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. @@ -197,35 +169,11 @@ async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: Returns: List of raw bytes for each item """ - payload = bytearray() - payload += encode_uint32_vlq(len(items)) - for db_number, start, size in items: - object_id = 0x00010000 | (db_number & 0xFFFF) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) - - offset = 0 - _, consumed = decode_uint32_vlq(response, offset) - offset += consumed - item_count, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - results: list[bytes] = [] - for _ in range(item_count): - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - if status == 0 and data_length > 0: - results.append(response[offset : offset + data_length]) - offset += data_length - else: - results.append(b"") - - return results + payload = _build_read_payload(items) + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + + results = _parse_read_response(response) + return [r if r is not None else b"" for r in results] async def explore(self) -> bytes: """Browse the PLC object tree. diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 2b0d2b0d..e5ddabd4 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -15,11 +15,18 @@ """ import logging +import struct from typing import Any, Optional from .connection import S7CommPlusConnection -from .protocol import FunctionCode -from .vlq import encode_uint32_vlq, decode_uint32_vlq +from .protocol import FunctionCode, Ids +from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq +from .codec import ( + encode_item_address, + encode_object_qualifier, + encode_pvalue_blob, + decode_pvalue_to_bytes, +) logger = logging.getLogger(__name__) @@ -127,61 +134,18 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: if self._connection is None: raise RuntimeError("Not connected") - # Build GetMultiVariables request payload - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) # 1 item - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - logger.debug( - f"db_read: db={db_number} start={start} size={size} " - f"object_id=0x{object_id:08X} payload={bytes(payload).hex(' ')}" - ) - - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + payload = _build_read_payload([(db_number, start, size)]) + logger.debug(f"db_read: db={db_number} start={start} size={size} payload={payload.hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - offset = 0 - # Skip return code - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - # Item count - item_count, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: item_count={item_count} (consumed {consumed} bytes)") - offset += consumed - - if item_count == 0: - logger.debug("db_read: no items returned") - return b"" - - # First item: status + data_length + data - status, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: item status={status} (consumed {consumed} bytes)") - offset += consumed - - data_length, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read: data_length={data_length} (consumed {consumed} bytes)") - offset += consumed - - if status != 0: - logger.error( - f"db_read: FAILED status={status}, remaining bytes: {response[offset:].hex(' ')}" - ) - raise RuntimeError(f"Read failed with status {status}") - - result = response[offset : offset + data_length] - logger.debug(f"db_read: result ({len(result)} bytes): {result.hex(' ')}") - remaining = response[offset + data_length :] - if remaining: - logger.debug(f"db_read: remaining after data ({len(remaining)} bytes): {remaining.hex(' ')}") - - return result + results = _parse_read_response(response) + if not results: + raise RuntimeError("Read returned no data") + if results[0] is None: + raise RuntimeError("Read failed: PLC returned error for item") + return results[0] def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. @@ -194,34 +158,16 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: if self._connection is None: raise RuntimeError("Not connected") - object_id = 0x00010000 | (db_number & 0xFFFF) - payload = bytearray() - payload += encode_uint32_vlq(1) # 1 item - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(len(data)) - payload += data - + payload = _build_write_payload([(db_number, start, data)]) logger.debug( f"db_write: db={db_number} start={start} data_len={len(data)} " - f"object_id=0x{object_id:08X} data={data.hex(' ')} payload={bytes(payload).hex(' ')}" + f"data={data.hex(' ')} payload={payload.hex(' ')}" ) - response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, bytes(payload)) - + response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, payload) logger.debug(f"db_write: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - check return code - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_write: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - if return_code != 0: - logger.error( - f"db_write: FAILED return_code={return_code}, remaining: {response[offset:].hex(' ')}" - ) - raise RuntimeError(f"Write failed with return code {return_code}") + _parse_write_response(response) def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. @@ -235,50 +181,14 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: if self._connection is None: raise RuntimeError("Not connected") - payload = bytearray() - payload += encode_uint32_vlq(len(items)) - for db_number, start, size in items: - object_id = 0x00010000 | (db_number & 0xFFFF) - payload += encode_uint32_vlq(object_id) - payload += encode_uint32_vlq(start) - payload += encode_uint32_vlq(size) - - logger.debug(f"db_read_multi: {len(items)} items: {items} payload={bytes(payload).hex(' ')}") - - response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, bytes(payload)) + payload = _build_read_payload(items) + logger.debug(f"db_read_multi: {len(items)} items: {items} payload={payload.hex(' ')}") + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") - # Parse response - offset = 0 - return_code, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read_multi: return_code={return_code} (consumed {consumed} bytes)") - offset += consumed - - item_count, consumed = decode_uint32_vlq(response, offset) - logger.debug(f"db_read_multi: item_count={item_count} (consumed {consumed} bytes)") - offset += consumed - - results: list[bytes] = [] - for i in range(item_count): - status, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - data_length, consumed = decode_uint32_vlq(response, offset) - offset += consumed - - logger.debug(f"db_read_multi: item[{i}] status={status} data_length={data_length}") - - if status == 0 and data_length > 0: - item_data = response[offset : offset + data_length] - logger.debug(f"db_read_multi: item[{i}] data: {item_data.hex(' ')}") - results.append(item_data) - offset += data_length - else: - logger.debug(f"db_read_multi: item[{i}] empty/error") - results.append(b"") - - return results + results = _parse_read_response(response) + return [r if r is not None else b"" for r in results] # -- Explore (browse PLC object tree) -- @@ -305,3 +215,190 @@ def __enter__(self) -> "S7CommPlusClient": def __exit__(self, *args: Any) -> None: self.disconnect() + + +# -- Request/response builders (module-level for reuse by async client) -- + + +def _build_read_payload(items: list[tuple[int, int, int]]) -> bytes: + """Build a GetMultiVariables request payload. + + Args: + items: List of (db_number, start_offset, size) tuples + + Returns: + Encoded payload bytes (after the 14-byte request header) + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs + """ + # Encode all item addresses and compute total field count + addresses: list[bytes] = [] + total_field_count = 0 + for db_number, start, size in items: + access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) + addr_bytes, field_count = encode_item_address( + access_area=access_area, + access_sub_area=Ids.DB_VALUE_ACTUAL, + lids=[start, size], + ) + addresses.append(addr_bytes) + total_field_count += field_count + + payload = bytearray() + # LinkId (UInt32 fixed = 0, for reading variables) + payload += struct.pack(">I", 0) + # Item count + payload += encode_uint32_vlq(len(items)) + # Total field count across all items + payload += encode_uint32_vlq(total_field_count) + # Item addresses + for addr in addresses: + payload += addr + # ObjectQualifier + payload += encode_object_qualifier() + # Padding + payload += struct.pack(">I", 0) + + return bytes(payload) + + +def _parse_read_response(response: bytes) -> list[Optional[bytes]]: + """Parse a GetMultiVariables response payload. + + Args: + response: Response payload (after the 14-byte response header) + + Returns: + List of raw bytes per item (None for errored items) + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesResponse.cs + """ + offset = 0 + + # ReturnValue (UInt64 VLQ) + return_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + logger.debug(f"_parse_read_response: return_value={return_value}") + + if return_value != 0: + logger.error(f"_parse_read_response: PLC returned error: {return_value}") + return [] + + # Value list: ItemNumber (VLQ) + PValue, terminated by ItemNumber=0 + values: dict[int, bytes] = {} + while offset < len(response): + item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if item_nr == 0: + break + raw_bytes, consumed = decode_pvalue_to_bytes(response, offset) + offset += consumed + values[item_nr] = raw_bytes + + # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ), terminated by 0 + errors: dict[int, int] = {} + while offset < len(response): + err_item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if err_item_nr == 0: + break + err_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + errors[err_item_nr] = err_value + logger.debug(f"_parse_read_response: error item {err_item_nr}: {err_value}") + + # Build result list (1-based item numbers) + max_item = max(max(values.keys(), default=0), max(errors.keys(), default=0)) + results: list[Optional[bytes]] = [] + for i in range(1, max_item + 1): + if i in values: + results.append(values[i]) + else: + results.append(None) + + return results + + +def _build_write_payload(items: list[tuple[int, int, bytes]]) -> bytes: + """Build a SetMultiVariables request payload. + + Args: + items: List of (db_number, start_offset, data) tuples + + Returns: + Encoded payload bytes + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs + """ + # Encode all item addresses and compute total field count + addresses: list[bytes] = [] + total_field_count = 0 + for db_number, start, data in items: + access_area = Ids.DB_ACCESS_AREA_BASE + (db_number & 0xFFFF) + addr_bytes, field_count = encode_item_address( + access_area=access_area, + access_sub_area=Ids.DB_VALUE_ACTUAL, + lids=[start, len(data)], + ) + addresses.append(addr_bytes) + total_field_count += field_count + + payload = bytearray() + # InObjectId (UInt32 fixed = 0, for plain variable writes) + payload += struct.pack(">I", 0) + # Item count + payload += encode_uint32_vlq(len(items)) + # Total field count + payload += encode_uint32_vlq(total_field_count) + # Item addresses + for addr in addresses: + payload += addr + # Value list: ItemNumber (1-based) + PValue + for i, (_, _, data) in enumerate(items, 1): + payload += encode_uint32_vlq(i) + payload += encode_pvalue_blob(data) + # Fill byte + payload += bytes([0x00]) + # ObjectQualifier + payload += encode_object_qualifier() + # Padding + payload += struct.pack(">I", 0) + + return bytes(payload) + + +def _parse_write_response(response: bytes) -> None: + """Parse a SetMultiVariables response payload. + + Args: + response: Response payload (after the 14-byte response header) + + Raises: + RuntimeError: If the write failed + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesResponse.cs + """ + offset = 0 + + # ReturnValue (UInt64 VLQ) + return_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + logger.debug(f"_parse_write_response: return_value={return_value}") + + if return_value != 0: + raise RuntimeError(f"Write failed with return value {return_value}") + + # Error list: ErrorItemNumber (VLQ) + ErrorReturnValue (UInt64 VLQ) + errors: list[tuple[int, int]] = [] + while offset < len(response): + err_item_nr, consumed = decode_uint32_vlq(response, offset) + offset += consumed + if err_item_nr == 0: + break + err_value, consumed = decode_uint64_vlq(response, offset) + offset += consumed + errors.append((err_item_nr, err_value)) + + if errors: + err_str = ", ".join(f"item {nr}: error {val}" for nr, val in errors) + raise RuntimeError(f"Write failed: {err_str}") diff --git a/snap7/s7commplus/codec.py b/snap7/s7commplus/codec.py index 79a7ec36..74f94a2e 100644 --- a/snap7/s7commplus/codec.py +++ b/snap7/s7commplus/codec.py @@ -15,11 +15,13 @@ import struct from typing import Any -from .protocol import PROTOCOL_ID, DataType +from .protocol import PROTOCOL_ID, DataType, Ids from .vlq import ( encode_uint32_vlq, + decode_uint32_vlq, encode_int32_vlq, encode_uint64_vlq, + decode_uint64_vlq, encode_int64_vlq, ) @@ -290,3 +292,204 @@ def encode_typed_value(datatype: int, value: Any) -> bytes: return bytes(tag + encode_uint32_vlq(len(value)) + value) else: raise ValueError(f"Unsupported DataType for encoding: {datatype:#04x}") + + +# -- S7CommPlus request/response payload helpers -- + + +def encode_object_qualifier() -> bytes: + """Encode the S7CommPlus ObjectQualifier structure. + + This fixed structure is appended to GetMultiVariables and + SetMultiVariables requests. + + Reference: thomas-v2/S7CommPlusDriver/Core/S7p.cs EncodeObjectQualifier + """ + result = bytearray() + result += struct.pack(">I", Ids.OBJECT_QUALIFIER) + # ParentRID = RID(0) + result += encode_uint32_vlq(Ids.PARENT_RID) + result += bytes([0x00, DataType.RID]) + struct.pack(">I", 0) + # CompositionAID = AID(0) + result += encode_uint32_vlq(Ids.COMPOSITION_AID) + result += bytes([0x00, DataType.AID]) + encode_uint32_vlq(0) + # KeyQualifier = UDInt(0) + result += encode_uint32_vlq(Ids.KEY_QUALIFIER) + result += bytes([0x00, DataType.UDINT]) + encode_uint32_vlq(0) + # Terminator + result += bytes([0x00]) + return bytes(result) + + +def encode_item_address( + access_area: int, + access_sub_area: int, + lids: list[int] | None = None, + symbol_crc: int = 0, +) -> tuple[bytes, int]: + """Encode an S7CommPlus ItemAddress for variable access. + + Args: + access_area: Access area ID (e.g., 0x8A0E0001 for DB1) + access_sub_area: Sub-area ID (e.g., Ids.DB_VALUE_ACTUAL) + lids: Additional LID values for sub-addressing + symbol_crc: Symbol CRC (0 for no CRC check) + + Returns: + Tuple of (encoded_bytes, field_count) + + Reference: thomas-v2/S7CommPlusDriver/ClientApi/ItemAddress.cs + """ + if lids is None: + lids = [] + result = bytearray() + result += encode_uint32_vlq(symbol_crc) + result += encode_uint32_vlq(access_area) + result += encode_uint32_vlq(len(lids) + 1) # +1 for AccessSubArea + result += encode_uint32_vlq(access_sub_area) + for lid in lids: + result += encode_uint32_vlq(lid) + field_count = 4 + len(lids) # SymbolCrc + AccessArea + NumLIDs + AccessSubArea + LIDs + return bytes(result), field_count + + +def encode_pvalue_blob(data: bytes) -> bytes: + """Encode raw bytes as a BLOB PValue. + + PValue format: [flags:1][datatype:1][length:VLQ][data] + """ + result = bytearray() + result += bytes([0x00, DataType.BLOB]) + result += encode_uint32_vlq(len(data)) + result += data + return bytes(result) + + +def decode_pvalue_to_bytes(data: bytes, offset: int) -> tuple[bytes, int]: + """Decode a PValue from S7CommPlus response to raw bytes. + + Supports scalar types and BLOBs. Returns the raw big-endian bytes + of the value regardless of type. + + Args: + data: Response buffer + offset: Position of the PValue + + Returns: + Tuple of (raw_bytes, bytes_consumed) + """ + if offset + 2 > len(data): + raise ValueError("Not enough data for PValue header") + + flags = data[offset] + datatype = data[offset + 1] + consumed = 2 + + is_array = bool(flags & 0x10) + + if is_array: + # Array: read count then elements + count, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + elem_size = _pvalue_element_size(datatype) + if elem_size > 0: + raw = data[offset + consumed : offset + consumed + count * elem_size] + consumed += count * elem_size + return bytes(raw), consumed + else: + # Variable-length elements (VLQ encoded) + result = bytearray() + for _ in range(count): + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + result += encode_uint32_vlq(val) + return bytes(result), consumed + + # Scalar types + if datatype == DataType.NULL: + return b"", consumed + elif datatype == DataType.BOOL: + return data[offset + consumed : offset + consumed + 1], consumed + 1 + elif datatype in (DataType.USINT, DataType.BYTE, DataType.SINT): + return data[offset + consumed : offset + consumed + 1], consumed + 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return data[offset + consumed : offset + consumed + 2], consumed + 2 + elif datatype in (DataType.UDINT, DataType.DWORD): + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">I", val), consumed + elif datatype in (DataType.DINT,): + # Signed VLQ + from .vlq import decode_int32_vlq + + val, c = decode_int32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">i", val), consumed + elif datatype == DataType.REAL: + return data[offset + consumed : offset + consumed + 4], consumed + 4 + elif datatype == DataType.LREAL: + return data[offset + consumed : offset + consumed + 8], consumed + 8 + elif datatype in (DataType.ULINT, DataType.LWORD): + val, c = decode_uint64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">Q", val), consumed + elif datatype in (DataType.LINT,): + from .vlq import decode_int64_vlq + + val, c = decode_int64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">q", val), consumed + elif datatype == DataType.TIMESTAMP: + return data[offset + consumed : offset + consumed + 8], consumed + 8 + elif datatype == DataType.TIMESPAN: + from .vlq import decode_int64_vlq + + val, c = decode_int64_vlq(data, offset + consumed) + consumed += c + return struct.pack(">q", val), consumed + elif datatype == DataType.RID: + return data[offset + consumed : offset + consumed + 4], consumed + 4 + elif datatype == DataType.AID: + val, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + return struct.pack(">I", val), consumed + elif datatype == DataType.BLOB: + length, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + raw = data[offset + consumed : offset + consumed + length] + consumed += length + return bytes(raw), consumed + elif datatype == DataType.WSTRING: + length, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + raw = data[offset + consumed : offset + consumed + length] + consumed += length + return bytes(raw), consumed + elif datatype == DataType.STRUCT: + # Struct: read count, then nested PValues + count, c = decode_uint32_vlq(data, offset + consumed) + consumed += c + result = bytearray() + for _ in range(count): + val_bytes, c = decode_pvalue_to_bytes(data, offset + consumed) + consumed += c + result += val_bytes + return bytes(result), consumed + else: + raise ValueError(f"Unsupported PValue datatype: {datatype:#04x}") + + +def _pvalue_element_size(datatype: int) -> int: + """Return the fixed byte size for a PValue array element, or 0 for variable-length.""" + if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return 2 + elif datatype in (DataType.REAL,): + return 4 + elif datatype in (DataType.LREAL, DataType.TIMESTAMP): + return 8 + elif datatype in (DataType.RID,): + return 4 + else: + return 0 # Variable-length (VLQ encoded) diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index cf49df53..71587639 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -143,6 +143,33 @@ class DataType(IntEnum): S7STRING = 0x19 +class Ids(IntEnum): + """Well-known IDs for S7CommPlus protocol structures. + + Reference: thomas-v2/S7CommPlusDriver/Core/Ids.cs + """ + + # Data block access sub-areas + DB_VALUE_ACTUAL = 2550 + CONTROLLER_AREA_VALUE_ACTUAL = 2551 + + # ObjectQualifier structure IDs + OBJECT_QUALIFIER = 1256 + PARENT_RID = 1257 + COMPOSITION_AID = 1258 + KEY_QUALIFIER = 1259 + + # Native object RIDs for memory areas + NATIVE_THE_I_AREA_RID = 80 + NATIVE_THE_Q_AREA_RID = 81 + NATIVE_THE_M_AREA_RID = 82 + NATIVE_THE_S7_COUNTERS_RID = 83 + NATIVE_THE_S7_TIMERS_RID = 84 + + # DB AccessArea base (add DB number to get area ID) + DB_ACCESS_AREA_BASE = 0x8A0E0000 + + class SoftDataType(IntEnum): """PLC soft data types (used in variable metadata / tag descriptions). diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index b40b587e..23f4ee5f 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -40,8 +40,14 @@ ProtocolVersion, SoftDataType, ) -from .vlq import encode_uint32_vlq, decode_uint32_vlq -from .codec import encode_header, decode_header, encode_typed_value +from .vlq import encode_uint32_vlq, decode_uint32_vlq, encode_uint64_vlq +from .codec import ( + encode_header, + decode_header, + encode_typed_value, + encode_pvalue_blob, + decode_pvalue_to_bytes, +) logger = logging.getLogger(__name__) @@ -613,7 +619,14 @@ def _handle_explore(self, seq_num: int, session_id: int, request_data: bytes) -> return bytes(response) def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle GetMultiVariables -- read variables from data blocks.""" + """Handle GetMultiVariables -- read variables from data blocks. + + Parses the S7CommPlus request format with ItemAddress structures. + The server extracts db_number from AccessArea and byte offset/size + from the LID values. + + Reference: thomas-v2/S7CommPlusDriver/Core/GetMultiVariablesRequest.cs + """ response = bytearray() response += struct.pack( ">BHHHHIB", @@ -625,49 +638,45 @@ def _handle_get_multi_variables(self, seq_num: int, session_id: int, request_dat session_id, 0x00, ) - response += encode_uint32_vlq(0) # Return code: success - # Parse request: expect object_id + variable addresses - offset = 0 - items: list[tuple[int, int, int]] = [] # (db_num, byte_offset, byte_size) + # Parse request payload + items = _server_parse_read_request(request_data) - # Simple request format: VLQ item count, then for each item: - # VLQ object_id, VLQ offset, VLQ size - if len(request_data) > 0: - count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed + # ReturnValue: success + response += encode_uint64_vlq(0) - for _ in range(count): - if offset >= len(request_data): - break - obj_id, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_offset, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_size, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - db_num = obj_id & 0xFFFF - items.append((db_num, byte_offset, byte_size)) - - # Read data for each item - response += encode_uint32_vlq(len(items)) - for db_num, byte_offset, byte_size in items: + # Value list: ItemNumber (1-based) + PValue, terminated by ItemNumber=0 + for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): db = self._data_blocks.get(db_num) if db is not None: data = db.read(byte_offset, byte_size) - response += encode_uint32_vlq(0) # Success - response += encode_uint32_vlq(len(data)) - response += data - else: - response += encode_uint32_vlq(1) # Error: not found - response += encode_uint32_vlq(0) + response += encode_uint32_vlq(i) # ItemNumber + response += encode_pvalue_blob(data) # Value as BLOB + # Errors handled in error list below + + # Terminate value list + response += encode_uint32_vlq(0) + + # Error list + for i, (db_num, byte_offset, byte_size) in enumerate(items, 1): + db = self._data_blocks.get(db_num) + if db is None: + response += encode_uint32_vlq(i) # ErrorItemNumber + response += encode_uint64_vlq(0x8104) # Error: object not found + + # Terminate error list + response += encode_uint32_vlq(0) + + # IntegrityId + response += encode_uint32_vlq(0) - response += struct.pack(">I", 0) return bytes(response) def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_data: bytes) -> bytes: - """Handle SetMultiVariables -- write variables to data blocks.""" + """Handle SetMultiVariables -- write variables to data blocks. + + Reference: thomas-v2/S7CommPlusDriver/Core/SetMultiVariablesRequest.cs + """ response = bytearray() response += struct.pack( ">BHHHHIB", @@ -680,42 +689,32 @@ def _handle_set_multi_variables(self, seq_num: int, session_id: int, request_dat 0x00, ) - # Parse request: VLQ item count, then for each item: - # VLQ object_id, VLQ offset, VLQ data_length, data bytes - offset = 0 - results: list[int] = [] + # Parse request payload + items, values = _server_parse_write_request(request_data) - if len(request_data) > 0: - count, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed + # Write data + errors: list[tuple[int, int]] = [] + for i, ((db_num, byte_offset, _), data) in enumerate(zip(items, values), 1): + db = self._data_blocks.get(db_num) + if db is not None: + db.write(byte_offset, data) + else: + errors.append((i, 0x8104)) # Object not found - for _ in range(count): - if offset >= len(request_data): - break - obj_id, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - byte_offset, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - data_len, consumed = decode_uint32_vlq(request_data, offset) - offset += consumed - - data = request_data[offset : offset + data_len] - offset += data_len - - db_num = obj_id & 0xFFFF - db = self._data_blocks.get(db_num) - if db is not None: - db.write(byte_offset, data) - results.append(0) # Success - else: - results.append(1) # Error: not found + # ReturnValue: success + response += encode_uint64_vlq(0) - response += encode_uint32_vlq(0) # Return code: success - response += encode_uint32_vlq(len(results)) - for r in results: - response += encode_uint32_vlq(r) + # Error list + for err_item, err_code in errors: + response += encode_uint32_vlq(err_item) + response += encode_uint64_vlq(err_code) + + # Terminate error list + response += encode_uint32_vlq(0) + + # IntegrityId + response += encode_uint32_vlq(0) - response += struct.pack(">I", 0) return bytes(response) def _build_error_response(self, seq_num: int, session_id: int, function_code: int) -> bytes: @@ -751,3 +750,153 @@ def __enter__(self) -> "S7CommPlusServer": def __exit__(self, *args: Any) -> None: self.stop() + + +# -- Server-side request parsers -- + + +def _server_parse_read_request(request_data: bytes) -> list[tuple[int, int, int]]: + """Parse a GetMultiVariables request payload on the server side. + + Extracts (db_number, byte_offset, byte_size) for each item from the + S7CommPlus ItemAddress format. + + Returns: + List of (db_number, byte_offset, byte_size) tuples + """ + if not request_data: + return [] + + offset = 0 + items: list[tuple[int, int, int]] = [] + + # LinkId (UInt32 fixed) + if offset + 4 > len(request_data): + return [] + offset += 4 + + # ItemCount (VLQ) + item_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # FieldCount (VLQ) + _field_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Parse each ItemAddress + for _ in range(item_count): + if offset >= len(request_data): + break + + # SymbolCrc + _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessArea + access_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # NumberOfLIDs + num_lids, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessSubArea (first LID) + _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Additional LIDs + lids: list[int] = [] + for _ in range(num_lids - 1): # -1 because AccessSubArea counts as one + if offset >= len(request_data): + break + lid_val, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + lids.append(lid_val) + + # Extract db_number from AccessArea + db_num = access_area & 0xFFFF + + # Extract byte offset and size from LIDs + byte_offset = lids[0] if len(lids) > 0 else 0 + byte_size = lids[1] if len(lids) > 1 else 1 + + items.append((db_num, byte_offset, byte_size)) + + return items + + +def _server_parse_write_request(request_data: bytes) -> tuple[list[tuple[int, int, int]], list[bytes]]: + """Parse a SetMultiVariables request payload on the server side. + + Returns: + Tuple of (items, values) where items is list of (db_number, byte_offset, byte_size) + and values is list of raw bytes to write + """ + if not request_data: + return [], [] + + offset = 0 + + # InObjectId (UInt32 fixed) + if offset + 4 > len(request_data): + return [], [] + offset += 4 + + # ItemCount (VLQ) + item_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # FieldCount (VLQ) + _field_count, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Parse each ItemAddress + items: list[tuple[int, int, int]] = [] + for _ in range(item_count): + if offset >= len(request_data): + break + + # SymbolCrc + _symbol_crc, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessArea + access_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # NumberOfLIDs + num_lids, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # AccessSubArea + _access_sub_area, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + + # Additional LIDs + lids: list[int] = [] + for _ in range(num_lids - 1): + if offset >= len(request_data): + break + lid_val, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + lids.append(lid_val) + + db_num = access_area & 0xFFFF + byte_offset = lids[0] if len(lids) > 0 else 0 + byte_size = lids[1] if len(lids) > 1 else 1 + items.append((db_num, byte_offset, byte_size)) + + # Parse value list: ItemNumber (VLQ, 1-based) + PValue + values: list[bytes] = [] + for _ in range(item_count): + if offset >= len(request_data): + break + item_nr, consumed = decode_uint32_vlq(request_data, offset) + offset += consumed + if item_nr == 0: + break + raw_bytes, consumed = decode_pvalue_to_bytes(request_data, offset) + offset += consumed + values.append(raw_bytes) + + return items, values From a4b75e6eb12d04fbeb0840ea97ce119c03a043bb Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 9 Mar 2026 10:48:56 +0200 Subject: [PATCH 22/27] Fix S7CommPlus LID byte offsets to use 1-based addressing S7CommPlus protocol uses 1-based LID byte offsets, but the client was sending 0-based offsets. This caused real PLCs to reject all db_read and db_write requests. Also fixes lint issues in e2e test file. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/client.py | 7 ++--- snap7/s7commplus/connection.py | 4 +-- snap7/s7commplus/server.py | 6 ++-- tests/test_s7commplus_e2e.py | 51 +++++++++++++--------------------- 4 files changed, 26 insertions(+), 42 deletions(-) diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index e5ddabd4..ceb9bf41 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -160,8 +160,7 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: payload = _build_write_payload([(db_number, start, data)]) logger.debug( - f"db_write: db={db_number} start={start} data_len={len(data)} " - f"data={data.hex(' ')} payload={payload.hex(' ')}" + f"db_write: db={db_number} start={start} data_len={len(data)} data={data.hex(' ')} payload={payload.hex(' ')}" ) response = self._connection.send_request(FunctionCode.SET_MULTI_VARIABLES, payload) @@ -239,7 +238,7 @@ def _build_read_payload(items: list[tuple[int, int, int]]) -> bytes: addr_bytes, field_count = encode_item_address( access_area=access_area, access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start, size], + lids=[start + 1, size], # LID byte offsets are 1-based in S7CommPlus ) addresses.append(addr_bytes) total_field_count += field_count @@ -338,7 +337,7 @@ def _build_write_payload(items: list[tuple[int, int, bytes]]) -> bytes: addr_bytes, field_count = encode_item_address( access_area=access_area, access_sub_area=Ids.DB_VALUE_ACTUAL, - lids=[start, len(data)], + lids=[start + 1, len(data)], # LID byte offsets are 1-based in S7CommPlus ) addresses.append(addr_bytes) total_field_count += field_count diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index e3ba388a..6a98ad5e 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -218,9 +218,7 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: ) request = request_header + payload - logger.debug( - f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}" - ) + logger.debug(f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}") logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 23f4ee5f..27c54adc 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -816,8 +816,8 @@ def _server_parse_read_request(request_data: bytes) -> list[tuple[int, int, int] # Extract db_number from AccessArea db_num = access_area & 0xFFFF - # Extract byte offset and size from LIDs - byte_offset = lids[0] if len(lids) > 0 else 0 + # Extract byte offset and size from LIDs (LID offsets are 1-based) + byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 byte_size = lids[1] if len(lids) > 1 else 1 items.append((db_num, byte_offset, byte_size)) @@ -882,7 +882,7 @@ def _server_parse_write_request(request_data: bytes) -> tuple[list[tuple[int, in lids.append(lid_val) db_num = access_area & 0xFFFF - byte_offset = lids[0] if len(lids) > 0 else 0 + byte_offset = (lids[0] - 1) if len(lids) > 0 else 0 # LID offsets are 1-based byte_size = lids[1] if len(lids) > 1 else 1 items.append((db_num, byte_offset, byte_size)) diff --git a/tests/test_s7commplus_e2e.py b/tests/test_s7commplus_e2e.py index 46da4b05..f8c8bf0d 100644 --- a/tests/test_s7commplus_e2e.py +++ b/tests/test_s7commplus_e2e.py @@ -441,17 +441,17 @@ def tearDownClass(cls) -> None: def test_diag_connection_info(self) -> None: """Dump connection state after successful connect.""" - print(f"\n{'='*60}") - print(f"DIAGNOSTIC: Connection Info") + print(f"\n{'=' * 60}") + print("DIAGNOSTIC: Connection Info") print(f" connected: {self.client.connected}") print(f" protocol_version: V{self.client.protocol_version}") print(f" session_id: 0x{self.client.session_id:08X} ({self.client.session_id})") - print(f"{'='*60}") + print(f"{'=' * 60}") self.assertTrue(self.client.connected) def test_diag_explore_raw(self) -> None: """Explore and dump the raw response for analysis.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Explore raw response") try: data = self.client.explore() @@ -464,22 +464,22 @@ def test_diag_explore_raw(self) -> None: print(f" {i:04x}: {hex_str:<96s} {ascii_str}") except Exception as e: print(f" Explore failed: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_db_read_single_byte(self) -> None: """Try to read a single byte from DB1 offset 0 and dump everything.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: db_read(DB1, offset=0, size=1)") try: data = self.client.db_read(DB_READ_ONLY, 0, 1) print(f" Success! Got {len(data)} bytes: {data.hex(' ')}") except Exception as e: print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_db_read_full_block(self) -> None: """Try to read the full test DB and dump everything.""" - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print(f"DIAGNOSTIC: db_read(DB{DB_READ_ONLY}, offset=0, size={DB_SIZE})") try: data = self.client.db_read(DB_READ_ONLY, 0, DB_SIZE) @@ -489,7 +489,7 @@ def test_diag_db_read_full_block(self) -> None: print(f" {i:04x}: {chunk.hex(' ')}") except Exception as e: print(f" FAILED: {type(e).__name__}: {e}") - print(f"{'='*60}") + print(f"{'=' * 60}") def test_diag_raw_get_multi_variables(self) -> None: """Send a raw GetMultiVariables with different payload formats and dump responses. @@ -499,7 +499,7 @@ def test_diag_raw_get_multi_variables(self) -> None: from snap7.s7commplus.protocol import FunctionCode from snap7.s7commplus.vlq import encode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Raw GetMultiVariables payload experiments") assert self.client._connection is not None @@ -507,10 +507,7 @@ def test_diag_raw_get_multi_variables(self) -> None: # Experiment 1: Our current format (item_count + object_id + offset + size) payloads = { "current_format (count=1, obj=0x00010001, off=0, sz=2)": ( - encode_uint32_vlq(1) - + encode_uint32_vlq(0x00010001) - + encode_uint32_vlq(0) - + encode_uint32_vlq(2) + encode_uint32_vlq(1) + encode_uint32_vlq(0x00010001) + encode_uint32_vlq(0) + encode_uint32_vlq(2) ), "empty_payload": b"", "just_zero": encode_uint32_vlq(0), @@ -521,9 +518,7 @@ def test_diag_raw_get_multi_variables(self) -> None: print(f"\n --- {label} ---") print(f" Payload ({len(payload)} bytes): {payload.hex(' ')}") try: - response = self.client._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, payload - ) + response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) print(f" Response ({len(response)} bytes): {response.hex(' ')}") # Try to parse return code @@ -538,14 +533,13 @@ def test_diag_raw_get_multi_variables(self) -> None: except Exception as e: print(f" EXCEPTION: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") def test_diag_raw_set_variable(self) -> None: """Try SetVariable (0x04F2) instead of SetMultiVariables to see if PLC responds differently.""" from snap7.s7commplus.protocol import FunctionCode - from snap7.s7commplus.vlq import encode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Raw SetVariable / GetVariable experiments") assert self.client._connection is not None @@ -565,14 +559,14 @@ def test_diag_raw_set_variable(self) -> None: except Exception as e: print(f" EXCEPTION: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") def test_diag_explore_then_read(self) -> None: """Explore first to discover object IDs, then try reading using those IDs.""" from snap7.s7commplus.protocol import FunctionCode, ElementID from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") print("DIAGNOSTIC: Explore -> extract object IDs -> try reading") assert self.client._connection is not None @@ -597,16 +591,9 @@ def test_diag_explore_then_read(self) -> None: # Try reading using each discovered object ID for obj_id in object_ids[:5]: # Limit to first 5 print(f"\n --- Read using object_id=0x{obj_id:08X} ---") - payload = ( - encode_uint32_vlq(1) - + encode_uint32_vlq(obj_id) - + encode_uint32_vlq(0) - + encode_uint32_vlq(4) - ) + payload = encode_uint32_vlq(1) + encode_uint32_vlq(obj_id) + encode_uint32_vlq(0) + encode_uint32_vlq(4) try: - response = self.client._connection.send_request( - FunctionCode.GET_MULTI_VARIABLES, payload - ) + response = self.client._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) print(f" Response ({len(response)} bytes): {response.hex(' ')}") if len(response) > 0: rc, consumed = decode_uint32_vlq(response, 0) @@ -617,4 +604,4 @@ def test_diag_explore_then_read(self) -> None: except Exception as e: print(f" Explore failed: {type(e).__name__}: {e}") - print(f"\n{'='*60}") + print(f"\n{'=' * 60}") From e63ca2216e756424a51f68a011e97141542a6758 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Mon, 9 Mar 2026 20:21:31 +0200 Subject: [PATCH 23/27] Add S7CommPlus session setup and legacy S7 fallback for data operations Implement the missing SetMultiVariables session handshake step that echoes ServerSessionVersion (attr 306) back to the PLC after CreateObject. Without this, PLCs reject data operations with ERROR2 (0x05A9). For PLCs that don't provide ServerSessionVersion or don't support S7CommPlus data operations, the client transparently falls back to the legacy S7 protocol. Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/async_client.py | 105 ++++++++++++- snap7/s7commplus/client.py | 111 ++++++++++++- snap7/s7commplus/connection.py | 257 ++++++++++++++++++++++++++++++- snap7/s7commplus/protocol.py | 1 + 4 files changed, 465 insertions(+), 9 deletions(-) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index 41780192..f7c77995 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -4,6 +4,10 @@ Provides the same API as S7CommPlusClient but using asyncio for non-blocking I/O. Uses asyncio.Lock for concurrent safety. +When a PLC does not support S7CommPlus data operations, the client +transparently falls back to the legacy S7 protocol for data block +read/write operations (using synchronous calls in an executor). + Example:: async with S7CommPlusAsyncClient() as client: @@ -27,8 +31,8 @@ S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, ) -from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier +from .vlq import encode_uint32_vlq, decode_uint64_vlq from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response logger = logging.getLogger(__name__) @@ -46,6 +50,9 @@ class S7CommPlusAsyncClient: Uses asyncio for all I/O operations and asyncio.Lock for concurrent safety when shared between multiple coroutines. + + When the PLC does not support S7CommPlus data operations, the client + automatically falls back to legacy S7 protocol for db_read/db_write. """ def __init__(self) -> None: @@ -56,9 +63,17 @@ def __init__(self) -> None: self._protocol_version: int = 0 self._connected = False self._lock = asyncio.Lock() + self._legacy_client: Optional[Any] = None + self._use_legacy_data: bool = False + self._host: str = "" + self._port: int = 102 + self._rack: int = 0 + self._slot: int = 1 @property def connected(self) -> bool: + if self._use_legacy_data and self._legacy_client is not None: + return bool(self._legacy_client.connected) return self._connected @property @@ -69,6 +84,11 @@ def protocol_version(self) -> int: def session_id(self) -> int: return self._session_id + @property + def using_legacy_fallback(self) -> bool: + """Whether the client is using legacy S7 protocol for data operations.""" + return self._use_legacy_data + async def connect( self, host: str, @@ -78,12 +98,20 @@ async def connect( ) -> None: """Connect to an S7-1200/1500 PLC. + If the PLC does not support S7CommPlus data operations, a secondary + legacy S7 connection is established transparently for data access. + Args: host: PLC IP address or hostname port: TCP port (default 102) rack: PLC rack number slot: PLC slot number """ + self._host = host + self._port = port + self._rack = rack + self._slot = slot + # TCP connect self._reader, self._writer = await asyncio.open_connection(host, port) @@ -101,12 +129,56 @@ async def connect( logger.info( f"Async S7CommPlus connected to {host}:{port}, version=V{self._protocol_version}, session={self._session_id}" ) + + # Probe S7CommPlus data operations + if not await self._probe_s7commplus_data(): + logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") + await self._setup_legacy_fallback() + except Exception: await self.disconnect() raise + async def _probe_s7commplus_data(self) -> bool: + """Test if the PLC supports S7CommPlus data operations.""" + try: + payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) + payload += encode_object_qualifier() + payload += struct.pack(">I", 0) + + response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + if len(response) < 1: + return False + return_value, _ = decode_uint64_vlq(response, 0) + if return_value != 0: + logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") + return False + return True + except Exception as e: + logger.debug(f"S7CommPlus probe failed: {e}") + return False + + async def _setup_legacy_fallback(self) -> None: + """Establish a secondary legacy S7 connection for data operations.""" + from ..client import Client + + loop = asyncio.get_event_loop() + client = Client() + await loop.run_in_executor(None, lambda: client.connect(self._host, self._rack, self._slot, self._port)) + self._legacy_client = client + self._use_legacy_data = True + logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") + async def disconnect(self) -> None: """Disconnect from PLC.""" + if self._legacy_client is not None: + try: + self._legacy_client.disconnect() + except Exception: + pass + self._legacy_client = None + self._use_legacy_data = False + if self._connected and self._session_id: try: await self._delete_session() @@ -138,6 +210,12 @@ async def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + data = await loop.run_in_executor(None, lambda: client.db_read(db_number, start, size)) + return bytes(data) + payload = _build_read_payload([(db_number, start, size)]) response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) @@ -156,6 +234,12 @@ async def db_write(self, db_number: int, start: int, data: bytes) -> None: start: Start byte offset data: Bytes to write """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + await loop.run_in_executor(None, lambda: client.db_write(db_number, start, bytearray(data))) + return + payload = _build_write_payload([(db_number, start, data)]) response = await self._send_request(FunctionCode.SET_MULTI_VARIABLES, payload) _parse_write_response(response) @@ -169,11 +253,24 @@ async def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: Returns: List of raw bytes for each item """ + if self._use_legacy_data and self._legacy_client is not None: + client = self._legacy_client + loop = asyncio.get_event_loop() + multi_results: list[bytes] = [] + for db_number, start, size in items: + + def _read(db: int = db_number, s: int = start, sz: int = size) -> bytearray: + return bytearray(client.db_read(db, s, sz)) + + data = await loop.run_in_executor(None, _read) + multi_results.append(bytes(data)) + return multi_results + payload = _build_read_payload(items) response = await self._send_request(FunctionCode.GET_MULTI_VARIABLES, payload) - results = _parse_read_response(response) - return [r if r is not None else b"" for r in results] + parsed = _parse_read_response(response) + return [r if r is not None else b"" for r in parsed] async def explore(self) -> bytes: """Browse the PLC object tree. diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index ceb9bf41..d5b38a40 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -9,6 +9,11 @@ version is auto-detected from the PLC's CreateObject response during connection setup. +When a PLC does not support S7CommPlus data operations (e.g. PLCs that +accept S7CommPlus sessions but return ERROR2 for GetMultiVariables), +the client transparently falls back to the legacy S7 protocol for +data block read/write operations. + Status: V1 connection is functional. V2/V3/TLS authentication planned. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) @@ -42,6 +47,9 @@ class S7CommPlusClient: The protocol version is auto-detected during connection. + When the PLC does not support S7CommPlus data operations, the client + automatically falls back to legacy S7 protocol for db_read/db_write. + Example:: client = S7CommPlusClient() @@ -58,9 +66,17 @@ class S7CommPlusClient: def __init__(self) -> None: self._connection: Optional[S7CommPlusConnection] = None + self._legacy_client: Optional[Any] = None + self._use_legacy_data: bool = False + self._host: str = "" + self._port: int = 102 + self._rack: int = 0 + self._slot: int = 1 @property def connected(self) -> bool: + if self._use_legacy_data and self._legacy_client is not None: + return bool(self._legacy_client.connected) return self._connection is not None and self._connection.connected @property @@ -77,6 +93,11 @@ def session_id(self) -> int: return 0 return self._connection.session_id + @property + def using_legacy_fallback(self) -> bool: + """Whether the client is using legacy S7 protocol for data operations.""" + return self._use_legacy_data + def connect( self, host: str, @@ -90,6 +111,9 @@ def connect( ) -> None: """Connect to an S7-1200/1500 PLC using S7CommPlus. + If the PLC does not support S7CommPlus data operations, a secondary + legacy S7 connection is established transparently for data access. + Args: host: PLC IP address or hostname port: TCP port (default 102) @@ -100,6 +124,11 @@ def connect( tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) """ + self._host = host + self._port = port + self._rack = rack + self._slot = slot + self._connection = S7CommPlusConnection( host=host, port=port, @@ -112,8 +141,63 @@ def connect( tls_ca=tls_ca, ) + # Probe S7CommPlus data operations with a minimal request + if not self._probe_s7commplus_data(): + logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") + self._setup_legacy_fallback() + + def _probe_s7commplus_data(self) -> bool: + """Test if the PLC supports S7CommPlus data operations. + + Sends a minimal GetMultiVariables request with zero items. If the PLC + responds with ERROR2 or a non-zero return code, data operations are + not supported. + + Returns: + True if S7CommPlus data operations work. + """ + if self._connection is None: + return False + + try: + # Send a minimal GetMultiVariables with 0 items + payload = struct.pack(">I", 0) + encode_uint32_vlq(0) + encode_uint32_vlq(0) + payload += encode_object_qualifier() + payload += struct.pack(">I", 0) + + response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) + + # Check if we got a valid response (return value = 0) + if len(response) < 1: + return False + return_value, _ = decode_uint64_vlq(response, 0) + if return_value != 0: + logger.debug(f"S7CommPlus probe: PLC returned error {return_value}") + return False + return True + except Exception as e: + logger.debug(f"S7CommPlus probe failed: {e}") + return False + + def _setup_legacy_fallback(self) -> None: + """Establish a secondary legacy S7 connection for data operations.""" + from ..client import Client + + self._legacy_client = Client() + self._legacy_client.connect(self._host, self._rack, self._slot, self._port) + self._use_legacy_data = True + logger.info(f"Legacy S7 fallback connected to {self._host}:{self._port}") + def disconnect(self) -> None: """Disconnect from PLC.""" + if self._legacy_client is not None: + try: + self._legacy_client.disconnect() + except Exception: + pass + self._legacy_client = None + self._use_legacy_data = False + if self._connection: self._connection.disconnect() self._connection = None @@ -123,6 +207,9 @@ def disconnect(self) -> None: def db_read(self, db_number: int, start: int, size: int) -> bytes: """Read raw bytes from a data block. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol transparently. + Args: db_number: Data block number start: Start byte offset @@ -131,6 +218,9 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: Returns: Raw bytes read from the data block """ + if self._use_legacy_data and self._legacy_client is not None: + return bytes(self._legacy_client.db_read(db_number, start, size)) + if self._connection is None: raise RuntimeError("Not connected") @@ -150,11 +240,18 @@ def db_read(self, db_number: int, start: int, size: int) -> bytes: def db_write(self, db_number: int, start: int, data: bytes) -> None: """Write raw bytes to a data block. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol transparently. + Args: db_number: Data block number start: Start byte offset data: Bytes to write """ + if self._use_legacy_data and self._legacy_client is not None: + self._legacy_client.db_write(db_number, start, bytearray(data)) + return + if self._connection is None: raise RuntimeError("Not connected") @@ -171,12 +268,22 @@ def db_write(self, db_number: int, start: int, data: bytes) -> None: def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: """Read multiple data block regions in a single request. + Uses S7CommPlus protocol when supported, otherwise falls back to + legacy S7 protocol (individual reads) transparently. + Args: items: List of (db_number, start_offset, size) tuples Returns: List of raw bytes for each item """ + if self._use_legacy_data and self._legacy_client is not None: + results = [] + for db_number, start, size in items: + data = self._legacy_client.db_read(db_number, start, size) + results.append(bytes(data)) + return results + if self._connection is None: raise RuntimeError("Not connected") @@ -186,8 +293,8 @@ def db_read_multi(self, items: list[tuple[int, int, int]]) -> list[bytes]: response = self._connection.send_request(FunctionCode.GET_MULTI_VARIABLES, payload) logger.debug(f"db_read_multi: response ({len(response)} bytes): {response.hex(' ')}") - results = _parse_read_response(response) - return [r if r is not None else b"" for r in results] + parsed = _parse_read_response(response) + return [r if r is not None else b"" for r in parsed] # -- Explore (browse PLC object tree) -- diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 6a98ad5e..fbbaf60d 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -54,13 +54,27 @@ S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, ) -from .codec import encode_header, decode_header, encode_typed_value -from .vlq import encode_uint32_vlq +from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier +from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq from .protocol import DataType logger = logging.getLogger(__name__) +def _element_size(datatype: int) -> int: + """Return the fixed byte size for an array element, or 0 for variable-length.""" + if datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return 2 + elif datatype in (DataType.REAL, DataType.RID): + return 4 + elif datatype in (DataType.LREAL, DataType.TIMESTAMP): + return 8 + else: + return 0 + + class S7CommPlusConnection: """S7CommPlus connection with multi-version support. @@ -95,6 +109,7 @@ def __init__( self._protocol_version: int = 0 # Detected from PLC response self._tls_active: bool = False self._connected = False + self._server_session_version: Optional[int] = None @property def connected(self) -> bool: @@ -153,7 +168,13 @@ def connect( # Step 4: CreateObject (S7CommPlus session setup) self._create_session() - # Step 5: Version-specific authentication + # Step 5: Session setup - echo ServerSessionVersion back to PLC + if self._server_session_version is not None: + self._setup_session() + else: + logger.warning("PLC did not provide ServerSessionVersion - session setup incomplete") + + # Step 6: Version-specific authentication if self._protocol_version >= ProtocolVersion.V3: if not use_tls: logger.warning( @@ -186,6 +207,7 @@ def disconnect(self) -> None: self._session_id = 0 self._sequence_number = 0 self._protocol_version = 0 + self._server_session_version = None self._iso_conn.disconnect() def send_request(self, function_code: int, payload: bytes = b"") -> bytes: @@ -418,6 +440,235 @@ def _create_session(self) -> None: logger.debug(f"CreateObject response payload: {response[14:].hex(' ')}") logger.debug(f"Session created: id=0x{self._session_id:08X} ({self._session_id}), version=V{version}") + # Parse response payload to extract ServerSessionVersion + self._parse_create_object_response(response[14:]) + + def _parse_create_object_response(self, payload: bytes) -> None: + """Parse CreateObject response payload to extract ServerSessionVersion. + + The response contains a PObject tree with attributes. We scan for + attribute 306 (ServerSessionVersion) which must be echoed back to + complete the session handshake. + + Args: + payload: Response payload after the 14-byte response header + """ + offset = 0 + while offset < len(payload): + tag = payload[offset] + + if tag == ElementID.ATTRIBUTE: + offset += 1 + if offset >= len(payload): + break + attr_id, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + + if attr_id == ObjectId.SERVER_SESSION_VERSION: + # Next bytes are the typed value: flags + datatype + VLQ value + if offset + 2 > len(payload): + break + _flags = payload[offset] + datatype = payload[offset + 1] + offset += 2 + if datatype == DataType.UDINT: + value, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + self._server_session_version = value + logger.info(f"ServerSessionVersion = {value}") + return + elif datatype == DataType.DWORD: + value, consumed = decode_uint32_vlq(payload, offset) + offset += consumed + self._server_session_version = value + logger.info(f"ServerSessionVersion = {value}") + return + else: + # Skip unknown type - try to continue scanning + logger.debug(f"ServerSessionVersion has unexpected type {datatype:#04x}") + else: + # Skip this attribute's value - we don't parse it, just advance + # Try to skip the typed value (flags + datatype + value) + if offset + 2 > len(payload): + break + _flags = payload[offset] + datatype = payload[offset + 1] + offset += 2 + offset = self._skip_typed_value(payload, offset, datatype, _flags) + + elif tag == ElementID.START_OF_OBJECT: + offset += 1 + # Skip RelationId (4 bytes fixed) + ClassId (VLQ) + ClassFlags (VLQ) + AttributeId (VLQ) + if offset + 4 > len(payload): + break + offset += 4 # RelationId + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # ClassId + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # ClassFlags + _, consumed = decode_uint32_vlq(payload, offset) + offset += consumed # AttributeId + + elif tag == ElementID.TERMINATING_OBJECT: + offset += 1 + + elif tag == 0x00: + # Null terminator / padding + offset += 1 + + else: + # Unknown tag - try to skip + offset += 1 + + logger.debug("ServerSessionVersion not found in CreateObject response") + + def _skip_typed_value(self, data: bytes, offset: int, datatype: int, flags: int) -> int: + """Skip over a typed value in the PObject tree. + + Best-effort: advances offset past common value types. + Returns new offset. + """ + is_array = bool(flags & 0x10) + + if is_array: + if offset >= len(data): + return offset + count, consumed = decode_uint32_vlq(data, offset) + offset += consumed + # For fixed-size types, skip count * size + elem_size = _element_size(datatype) + if elem_size > 0: + offset += count * elem_size + else: + # Variable-length: skip each VLQ element + for _ in range(count): + if offset >= len(data): + break + _, consumed = decode_uint32_vlq(data, offset) + offset += consumed + return offset + + if datatype == DataType.NULL: + return offset + elif datatype in (DataType.BOOL, DataType.USINT, DataType.BYTE, DataType.SINT): + return offset + 1 + elif datatype in (DataType.UINT, DataType.WORD, DataType.INT): + return offset + 2 + elif datatype in (DataType.UDINT, DataType.DWORD, DataType.AID, DataType.DINT): + _, consumed = decode_uint32_vlq(data, offset) + return offset + consumed + elif datatype in (DataType.ULINT, DataType.LWORD, DataType.LINT): + _, consumed = decode_uint64_vlq(data, offset) + return offset + consumed + elif datatype == DataType.REAL: + return offset + 4 + elif datatype == DataType.LREAL: + return offset + 8 + elif datatype == DataType.TIMESTAMP: + return offset + 8 + elif datatype == DataType.TIMESPAN: + _, consumed = decode_uint64_vlq(data, offset) # int64 VLQ + return offset + consumed + elif datatype == DataType.RID: + return offset + 4 + elif datatype in (DataType.BLOB, DataType.WSTRING): + length, consumed = decode_uint32_vlq(data, offset) + return offset + consumed + length + elif datatype == DataType.STRUCT: + count, consumed = decode_uint32_vlq(data, offset) + offset += consumed + for _ in range(count): + if offset + 2 > len(data): + break + sub_flags = data[offset] + sub_type = data[offset + 1] + offset += 2 + offset = self._skip_typed_value(data, offset, sub_type, sub_flags) + return offset + else: + # Unknown type - can't skip reliably + return offset + + def _setup_session(self) -> None: + """Send SetMultiVariables to echo ServerSessionVersion back to the PLC. + + This completes the session handshake by writing the ServerSessionVersion + attribute back to the session object. Without this step, the PLC rejects + all subsequent data operations with ERROR2 (0x05A9). + + Reference: thomas-v2/S7CommPlusDriver SetSessionSetupData + """ + if self._server_session_version is None: + return + + seq_num = self._next_sequence_number() + + # Build SetMultiVariables request + request = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + FunctionCode.SET_MULTI_VARIABLES, + 0x0000, + seq_num, + self._session_id, + 0x36, # Transport flags + ) + + payload = bytearray() + # InObjectId = session ID (tells PLC which object we're writing to) + payload += struct.pack(">I", self._session_id) + # Item count = 1 + payload += encode_uint32_vlq(1) + # Total address field count = 1 (just the attribute ID) + payload += encode_uint32_vlq(1) + # Address: attribute ID = ServerSessionVersion (306) as VLQ + payload += encode_uint32_vlq(ObjectId.SERVER_SESSION_VERSION) + # Value: ItemNumber = 1 (VLQ) + payload += encode_uint32_vlq(1) + # PValue: flags=0x00, type=UDInt, VLQ-encoded value + payload += bytes([0x00, DataType.UDINT]) + payload += encode_uint32_vlq(self._server_session_version) + # Fill byte + payload += bytes([0x00]) + # ObjectQualifier + payload += encode_object_qualifier() + # Trailing padding + payload += struct.pack(">I", 0) + + request += bytes(payload) + + # Wrap in S7CommPlus frame + frame = encode_header(self._protocol_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) + + logger.debug(f"=== SetupSession === sending ({len(frame)} bytes): {frame.hex(' ')}") + self._iso_conn.send_data(frame) + + # Receive response + response_frame = self._iso_conn.receive_data() + logger.debug(f"=== SetupSession === received ({len(response_frame)} bytes): {response_frame.hex(' ')}") + + version, data_length, consumed = decode_header(response_frame) + response = response_frame[consumed : consumed + data_length] + + if len(response) < 14: + from ..error import S7ConnectionError + + raise S7ConnectionError("SetupSession response too short") + + resp_func = struct.unpack_from(">H", response, 3)[0] + logger.debug(f"SetupSession response: function=0x{resp_func:04X}") + + # Parse return value from payload + resp_payload = response[14:] + if len(resp_payload) >= 1: + return_value, _ = decode_uint64_vlq(resp_payload, 0) + if return_value != 0: + logger.warning(f"SetupSession: PLC returned error {return_value}") + else: + logger.info("Session setup completed successfully") + def _delete_session(self) -> None: """Send DeleteObject to close the session.""" seq_num = self._next_sequence_number() diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 71587639..2095cb29 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -100,6 +100,7 @@ class ObjectId(IntEnum): CLASS_SERVER_SESSION = 287 OBJECT_NULL_SERVER_SESSION = 288 SERVER_SESSION_CLIENT_RID = 300 + SERVER_SESSION_VERSION = 306 # Default TSAP for S7CommPlus connections From 114925754c46c660c036c2a9e42c177384f0b4cb Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 20 Mar 2026 10:30:29 +0200 Subject: [PATCH 24/27] Add S7CommPlus V2 protocol support (TLS + IntegrityId) Implements V2 protocol support for S7-1200/1500 PLCs with modern firmware: - TLS 1.3 activation between InitSSL and CreateObject - OMS exporter secret extraction for legitimation key derivation - Dual IntegrityId counters (read vs write) in V2 PDU headers - Password legitimation module (legacy SHA-1 XOR + new AES-256-CBC) - V2 server emulator with TLS and IntegrityId tracking - 39 new tests covering all V2 components Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/__init__.py | 2 +- snap7/s7commplus/async_client.py | 65 ++++++-- snap7/s7commplus/client.py | 15 +- snap7/s7commplus/connection.py | 157 +++++++++++++++++-- snap7/s7commplus/legitimation.py | 154 +++++++++++++++++++ snap7/s7commplus/protocol.py | 24 +++ snap7/s7commplus/server.py | 163 ++++++++++++++++++-- tests/test_s7commplus_v2.py | 250 +++++++++++++++++++++++++++++++ 8 files changed, 779 insertions(+), 51 deletions(-) create mode 100644 snap7/s7commplus/legitimation.py create mode 100644 tests/test_s7commplus_v2.py diff --git a/snap7/s7commplus/__init__.py b/snap7/s7commplus/__init__.py index f8ff995a..ab49d09c 100644 --- a/snap7/s7commplus/__init__.py +++ b/snap7/s7commplus/__init__.py @@ -29,7 +29,7 @@ The wire protocol (VLQ encoding, data types, function codes, object model) is the same across all versions -- only the session authentication differs. -Status: experimental scaffolding -- not yet functional. +Status: V1 connection functional, V2 (TLS + IntegrityId) scaffolding complete. Reference implementation: https://github.com/thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) diff --git a/snap7/s7commplus/async_client.py b/snap7/s7commplus/async_client.py index f7c77995..e6a46fe2 100644 --- a/snap7/s7commplus/async_client.py +++ b/snap7/s7commplus/async_client.py @@ -28,11 +28,12 @@ ObjectId, Opcode, ProtocolVersion, + READ_FUNCTION_CODES, S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, ) from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier -from .vlq import encode_uint32_vlq, decode_uint64_vlq +from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq from .client import _build_read_payload, _parse_read_response, _build_write_payload, _parse_write_response logger = logging.getLogger(__name__) @@ -46,7 +47,7 @@ class S7CommPlusAsyncClient: """Async S7CommPlus client for S7-1200/1500 PLCs. - Supports V1 protocol. V2/V3/TLS planned for future. + Supports V1 and V2 protocols. V3/TLS planned for future. Uses asyncio for all I/O operations and asyncio.Lock for concurrent safety when shared between multiple coroutines. @@ -70,6 +71,11 @@ def __init__(self) -> None: self._rack: int = 0 self._slot: int = 1 + # V2+ IntegrityId tracking + self._integrity_id_read: int = 0 + self._integrity_id_write: int = 0 + self._with_integrity_id: bool = False + @property def connected(self) -> bool: if self._use_legacy_data and self._legacy_client is not None: @@ -189,6 +195,9 @@ async def disconnect(self) -> None: self._session_id = 0 self._sequence_number = 0 self._protocol_version = 0 + self._with_integrity_id = False + self._integrity_id_read = 0 + self._integrity_id_write = 0 if self._writer: try: @@ -283,31 +292,48 @@ async def explore(self) -> bytes: # -- Internal methods -- async def _send_request(self, function_code: int, payload: bytes) -> bytes: - """Send an S7CommPlus request and receive the response.""" + """Send an S7CommPlus request and receive the response. + + For V2+ with IntegrityId tracking, inserts IntegrityId after the + 14-byte request header and strips it from the response. + """ async with self._lock: if not self._connected or self._writer is None or self._reader is None: raise RuntimeError("Not connected") seq_num = self._next_sequence_number() - request = ( - struct.pack( - ">BHHHHIB", - Opcode.REQUEST, - 0x0000, - function_code, - 0x0000, - seq_num, - self._session_id, - 0x36, - ) - + payload + request_header = struct.pack( + ">BHHHHIB", + Opcode.REQUEST, + 0x0000, + function_code, + 0x0000, + seq_num, + self._session_id, + 0x36, ) + # For V2+ with IntegrityId, insert after header + integrity_id_bytes = b"" + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + is_read = function_code in READ_FUNCTION_CODES + integrity_id = self._integrity_id_read if is_read else self._integrity_id_write + integrity_id_bytes = encode_uint32_vlq(integrity_id) + + request = request_header + integrity_id_bytes + payload + frame = encode_header(self._protocol_version, len(request)) + request frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) await self._send_cotp_dt(frame) + # Increment appropriate IntegrityId counter + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + if function_code in READ_FUNCTION_CODES: + self._integrity_id_read = (self._integrity_id_read + 1) & 0xFFFFFFFF + else: + self._integrity_id_write = (self._integrity_id_write + 1) & 0xFFFFFFFF + response_data = await self._recv_cotp_dt() version, data_length, consumed = decode_header(response_data) @@ -316,7 +342,14 @@ async def _send_request(self, function_code: int, payload: bytes) -> bytes: if len(response) < 14: raise RuntimeError("Response too short") - return response[14:] + # For V2+, skip IntegrityId in response + resp_offset = 14 + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + if resp_offset < len(response): + _resp_iid, iid_consumed = decode_uint32_vlq(response, resp_offset) + resp_offset += iid_consumed + + return response[resp_offset:] async def _cotp_connect(self, local_tsap: int, remote_tsap: bytes) -> None: """Perform COTP Connection Request / Confirm handshake.""" diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index d5b38a40..8ccfe812 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -14,7 +14,7 @@ the client transparently falls back to the legacy S7 protocol for data block read/write operations. -Status: V1 connection is functional. V2/V3/TLS authentication planned. +Status: V1 and V2 connections are functional. V3/TLS authentication planned. Reference: thomas-v2/S7CommPlusDriver (C#, LGPL-3.0) """ @@ -108,6 +108,7 @@ def connect( tls_cert: Optional[str] = None, tls_key: Optional[str] = None, tls_ca: Optional[str] = None, + password: Optional[str] = None, ) -> None: """Connect to an S7-1200/1500 PLC using S7CommPlus. @@ -119,10 +120,11 @@ def connect( port: TCP port (default 102) rack: PLC rack number slot: PLC slot number - use_tls: Whether to attempt TLS (requires V3 PLC + certs) + use_tls: Whether to activate TLS (required for V2) tls_cert: Path to client TLS certificate (PEM) tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) + password: PLC password for legitimation (V2+ with TLS) """ self._host = host self._port = port @@ -141,6 +143,15 @@ def connect( tls_ca=tls_ca, ) + # Handle legitimation for password-protected PLCs + if password is not None and self._connection.tls_active and self._connection.oms_secret is not None: + logger.info("Performing PLC legitimation (password authentication)") + # Legitimation requires the cryptography package for new-style auth + # For now, raise NotImplementedError - callers should catch this + raise NotImplementedError( + "PLC password legitimation is not yet implemented. Connection works without password for unprotected PLCs." + ) + # Probe S7CommPlus data operations with a minimal request if not self._probe_s7commplus_data(): logger.info("S7CommPlus data operations not supported, falling back to legacy S7 protocol") diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index fbbaf60d..9489d6bb 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -53,6 +53,7 @@ ObjectId, S7COMMPLUS_LOCAL_TSAP, S7COMMPLUS_REMOTE_TSAP, + READ_FUNCTION_CODES, ) from .codec import encode_header, decode_header, encode_typed_value, encode_object_qualifier from .vlq import encode_uint32_vlq, decode_uint32_vlq, decode_uint64_vlq @@ -104,6 +105,7 @@ def __init__( ) self._ssl_context: Optional[ssl.SSLContext] = None + self._ssl_socket: Optional[ssl.SSLSocket] = None self._session_id: int = 0 self._sequence_number: int = 0 self._protocol_version: int = 0 # Detected from PLC response @@ -111,6 +113,14 @@ def __init__( self._connected = False self._server_session_version: Optional[int] = None + # V2+ IntegrityId tracking + self._integrity_id_read: int = 0 + self._integrity_id_write: int = 0 + self._with_integrity_id: bool = False + + # TLS OMS exporter secret (for legitimation key derivation) + self._oms_secret: Optional[bytes] = None + @property def connected(self) -> bool: return self._connected @@ -130,6 +140,21 @@ def tls_active(self) -> bool: """Whether TLS encryption is active on this connection.""" return self._tls_active + @property + def integrity_id_read(self) -> int: + """Current read IntegrityId counter (V2+).""" + return self._integrity_id_read + + @property + def integrity_id_write(self) -> int: + """Current write IntegrityId counter (V2+).""" + return self._integrity_id_write + + @property + def oms_secret(self) -> Optional[bytes]: + """OMS exporter secret from TLS session (for legitimation).""" + return self._oms_secret + def connect( self, timeout: float = 5.0, @@ -142,13 +167,15 @@ def connect( The connection sequence: 1. COTP connection (same as legacy S7comm) - 2. CreateObject to establish S7CommPlus session - 3. Protocol version is detected from PLC response - 4. If use_tls=True and PLC supports it, TLS is negotiated + 2. InitSSL handshake + 3. TLS activation (if use_tls=True, required for V2) + 4. CreateObject to establish S7CommPlus session + 5. Session setup (echo ServerSessionVersion) + 6. Enable IntegrityId tracking (V2+) Args: timeout: Connection timeout in seconds - use_tls: Whether to attempt TLS negotiation. + use_tls: Whether to activate TLS after InitSSL. tls_cert: Path to client TLS certificate (PEM) tls_key: Path to client private key (PEM) tls_ca: Path to CA certificate for PLC verification (PEM) @@ -160,12 +187,12 @@ def connect( # Step 2: InitSSL handshake (required before CreateObject) self._init_ssl() - # Step 3: TLS activation (required for modern firmware) + # Step 3: TLS activation (between InitSSL and CreateObject) if use_tls: - # TODO: Perform TLS 1.3 handshake over the existing COTP connection - raise NotImplementedError("TLS activation is not yet implemented. Use use_tls=False for V1 connections.") + self._activate_tls(tls_cert=tls_cert, tls_key=tls_key, tls_ca=tls_ca) # Step 4: CreateObject (S7CommPlus session setup) + # CreateObject always uses V1 framing self._create_session() # Step 5: Session setup - echo ServerSessionVersion back to PLC @@ -174,20 +201,29 @@ def connect( else: logger.warning("PLC did not provide ServerSessionVersion - session setup incomplete") - # Step 6: Version-specific authentication + # Step 6: Version-specific post-setup if self._protocol_version >= ProtocolVersion.V3: if not use_tls: logger.warning( "PLC reports V3 protocol but TLS is not enabled. Connection may not work without use_tls=True." ) elif self._protocol_version == ProtocolVersion.V2: - # TODO: Proprietary HMAC-SHA256/AES session auth - raise NotImplementedError("V2 authentication is not yet implemented.") + if not self._tls_active: + from ..error import S7ConnectionError + + raise S7ConnectionError("PLC reports V2 protocol but TLS is not active. V2 requires TLS. Use use_tls=True.") + # Enable IntegrityId tracking for V2+ + self._with_integrity_id = True + self._integrity_id_read = 0 + self._integrity_id_write = 0 + logger.info("V2 IntegrityId tracking enabled") # V1: No further authentication needed after CreateObject self._connected = True logger.info( - f"S7CommPlus connected to {self.host}:{self.port}, version=V{self._protocol_version}, session={self._session_id}" + f"S7CommPlus connected to {self.host}:{self.port}, " + f"version=V{self._protocol_version}, session={self._session_id}, " + f"tls={self._tls_active}" ) except Exception: @@ -204,15 +240,24 @@ def disconnect(self) -> None: self._connected = False self._tls_active = False + self._ssl_socket = None + self._oms_secret = None self._session_id = 0 self._sequence_number = 0 self._protocol_version = 0 self._server_session_version = None + self._with_integrity_id = False + self._integrity_id_read = 0 + self._integrity_id_write = 0 self._iso_conn.disconnect() def send_request(self, function_code: int, payload: bytes = b"") -> bytes: """Send an S7CommPlus request and receive the response. + For V2+ with IntegrityId tracking enabled, the IntegrityId is + appended after the 14-byte request header (as a VLQ uint32). + Read vs write counters are selected based on the function code. + Args: function_code: S7CommPlus function code payload: Request payload (after the 14-byte request header) @@ -227,7 +272,7 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: seq_num = self._next_sequence_number() - # Build request header + # Build request header (14 bytes) request_header = struct.pack( ">BHHHHIB", Opcode.REQUEST, @@ -238,19 +283,43 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: self._session_id, 0x36, # Transport flags ) - request = request_header + payload + + # For V2+ with IntegrityId enabled, insert IntegrityId after header + integrity_id_bytes = b"" + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + is_read = function_code in READ_FUNCTION_CODES + if is_read: + integrity_id = self._integrity_id_read + else: + integrity_id = self._integrity_id_write + integrity_id_bytes = encode_uint32_vlq(integrity_id) + logger.debug(f" IntegrityId: {'read' if is_read else 'write'}={integrity_id}") + + request = request_header + integrity_id_bytes + payload logger.debug(f"=== SEND REQUEST === function_code=0x{function_code:04X} seq={seq_num} session=0x{self._session_id:08X}") logger.debug(f" Request header (14 bytes): {request_header.hex(' ')}") + if integrity_id_bytes: + logger.debug(f" IntegrityId ({len(integrity_id_bytes)} bytes): {integrity_id_bytes.hex(' ')}") logger.debug(f" Request payload ({len(payload)} bytes): {payload.hex(' ')}") + # Determine frame version: V2 data PDUs use V2, but CreateObject uses V1 + frame_version = self._protocol_version + # Add S7CommPlus frame header and trailer, then send - frame = encode_header(self._protocol_version, len(request)) + request - frame += struct.pack(">BBH", 0x72, self._protocol_version, 0x0000) + frame = encode_header(frame_version, len(request)) + request + frame += struct.pack(">BBH", 0x72, frame_version, 0x0000) logger.debug(f" Full frame ({len(frame)} bytes): {frame.hex(' ')}") self._iso_conn.send_data(frame) + # Increment the appropriate IntegrityId counter after sending + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + if function_code in READ_FUNCTION_CODES: + self._integrity_id_read = (self._integrity_id_read + 1) & 0xFFFFFFFF + else: + self._integrity_id_write = (self._integrity_id_write + 1) & 0xFFFFFFFF + # Receive response response_frame = self._iso_conn.receive_data() logger.debug(f"=== RECV RESPONSE === raw frame ({len(response_frame)} bytes): {response_frame.hex(' ')}") @@ -278,7 +347,15 @@ def send_request(self, function_code: int, payload: bytes = b"") -> bytes: f"seq={resp_seq} session=0x{resp_session:08X} transport=0x{resp_transport:02X}" ) - resp_payload = response[14:] + # For V2+ responses, skip IntegrityId in response before returning payload + resp_offset = 14 + if self._with_integrity_id and self._protocol_version >= ProtocolVersion.V2: + if resp_offset < len(response): + resp_integrity_id, iid_consumed = decode_uint32_vlq(response, resp_offset) + resp_offset += iid_consumed + logger.debug(f" Response IntegrityId: {resp_integrity_id}") + + resp_payload = response[resp_offset:] logger.debug(f" Response payload ({len(resp_payload)} bytes): {resp_payload.hex(' ')}") # Check for trailer bytes after data_length @@ -701,6 +778,53 @@ def _next_sequence_number(self) -> int: self._sequence_number = (self._sequence_number + 1) & 0xFFFF return seq + def _activate_tls( + self, + tls_cert: Optional[str] = None, + tls_key: Optional[str] = None, + tls_ca: Optional[str] = None, + ) -> None: + """Activate TLS 1.3 over the COTP connection. + + Called after InitSSL and before CreateObject. Wraps the underlying + TCP socket with TLS and extracts the OMS exporter secret for + legitimation key derivation. + + Args: + tls_cert: Path to client TLS certificate (PEM) + tls_key: Path to client private key (PEM) + tls_ca: Path to CA certificate for PLC verification (PEM) + """ + ctx = self._setup_ssl_context( + cert_path=tls_cert, + key_path=tls_key, + ca_path=tls_ca, + ) + + # Wrap the raw TCP socket used by ISOTCPConnection + raw_socket = self._iso_conn.socket + if raw_socket is None: + from ..error import S7ConnectionError + + raise S7ConnectionError("Cannot activate TLS: no TCP socket") + + self._ssl_socket = ctx.wrap_socket(raw_socket, server_hostname=self.host) + + # Replace the socket in ISOTCPConnection so all subsequent + # send_data/receive_data calls go through TLS + self._iso_conn.socket = self._ssl_socket + self._tls_active = True + + # Extract OMS exporter secret for legitimation key derivation + try: + self._oms_secret = self._ssl_socket.export_keying_material("EXPERIMENTAL_OMS", 32, None) + logger.debug("OMS exporter secret extracted from TLS session") + except (AttributeError, ssl.SSLError) as e: + logger.warning(f"Could not extract OMS exporter secret: {e}") + self._oms_secret = None + + logger.info("TLS 1.3 activated on COTP connection") + def _setup_ssl_context( self, cert_path: Optional[str] = None, @@ -719,6 +843,7 @@ def _setup_ssl_context( """ ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) ctx.minimum_version = ssl.TLSVersion.TLSv1_3 + ctx.set_ciphers("TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256") if cert_path and key_path: ctx.load_cert_chain(cert_path, key_path) diff --git a/snap7/s7commplus/legitimation.py b/snap7/s7commplus/legitimation.py new file mode 100644 index 00000000..75d7cdce --- /dev/null +++ b/snap7/s7commplus/legitimation.py @@ -0,0 +1,154 @@ +"""S7CommPlus PLC password authentication (legitimation). + +Supports two authentication modes: +- Legacy: SHA-1 password hash XORed with challenge (older firmware) +- New: AES-256-CBC encrypted credentials with TLS-derived key (newer firmware) + +Firmware version determines which mode is used: +- S7-1500: FW >= 3.01 = new, FW 2.09-2.99 = legacy +- S7-1200: FW >= 4.07 = new, FW 4.03-4.06 = legacy + +Note: The "new" mode requires the ``cryptography`` package for AES-256-CBC. +Install with ``pip install cryptography``. The legacy mode uses only stdlib. +""" + +import hashlib +import logging +from typing import Optional + +logger = logging.getLogger(__name__) + + +def derive_legitimation_key(oms_secret: bytes) -> bytes: + """Derive AES-256 key from TLS OMS exporter secret. + + Args: + oms_secret: 32-byte OMS exporter secret from TLS session + + Returns: + 32-byte AES-256 key + """ + return hashlib.sha256(oms_secret).digest() + + +def build_legacy_response(password: str, challenge: bytes) -> bytes: + """Build legacy legitimation response (SHA-1 XOR). + + Args: + password: PLC password + challenge: 20-byte challenge from PLC + + Returns: + Response bytes (SHA-1 hash XORed with challenge) + """ + password_hash = hashlib.sha1(password.encode("utf-8")).digest() # noqa: S324 + return bytes(a ^ b for a, b in zip(password_hash, challenge[:20])) + + +def build_new_response( + password: str, + challenge: bytes, + oms_secret: bytes, + username: str = "", +) -> bytes: + """Build new legitimation response (AES-256-CBC encrypted). + + Requires the ``cryptography`` package. + + Args: + password: PLC password + challenge: Challenge from PLC (first 16 bytes used as IV) + oms_secret: 32-byte OMS exporter secret + username: Optional username (empty string for legacy-style new auth) + + Returns: + AES-256-CBC encrypted response + + Raises: + NotImplementedError: If ``cryptography`` is not installed + """ + try: + from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes + from cryptography.hazmat.primitives import padding + except ImportError: + raise NotImplementedError( + "AES-256-CBC legitimation requires the 'cryptography' package. Install with: pip install cryptography" + ) + + key = derive_legitimation_key(oms_secret) + iv = bytes(challenge[:16]) + + payload = _build_legitimation_payload(password, username) + + padder = padding.PKCS7(128).padder() + padded = padder.update(payload) + padder.finalize() + + cipher = Cipher(algorithms.AES(key), modes.CBC(iv)) + encryptor = cipher.encryptor() + result: bytes = encryptor.update(padded) + encryptor.finalize() + return result + + +def _build_legitimation_payload(password: str, username: str = "") -> bytes: + """Build the legitimation payload structure. + + The payload is a serialized ValueStruct with: + - 40401: LegitimationType (1=legacy, 2=new) + - 40402: Username (UTF-8 blob) + - 40403: Password or password hash (SHA-1) + """ + from .vlq import encode_uint32_vlq + from .protocol import DataType + + result = bytearray() + + if username: + legit_type = 2 + password_data = password.encode("utf-8") + else: + legit_type = 1 + password_data = hashlib.sha1(password.encode("utf-8")).digest() # noqa: S324 + + username_data = username.encode("utf-8") + + # Struct with 3 elements + result += bytes([0x00, DataType.STRUCT]) + result += encode_uint32_vlq(3) + + # Element 1: LegitimationType + result += bytes([0x00, DataType.UDINT]) + result += encode_uint32_vlq(legit_type) + + # Element 2: Username blob + result += bytes([0x00, DataType.BLOB]) + result += encode_uint32_vlq(len(username_data)) + result += username_data + + # Element 3: Password blob + result += bytes([0x00, DataType.BLOB]) + result += encode_uint32_vlq(len(password_data)) + result += password_data + + return bytes(result) + + +class LegitimationState: + """Tracks legitimation state for a connection.""" + + def __init__(self, oms_secret: Optional[bytes] = None) -> None: + self._oms_key: Optional[bytes] = None + if oms_secret: + self._oms_key = derive_legitimation_key(oms_secret) + self._authenticated = False + + @property + def authenticated(self) -> bool: + return self._authenticated + + def mark_authenticated(self) -> None: + self._authenticated = True + + def rotate_key(self) -> None: + """Rotate the OMS-derived key (called after each legitimation).""" + if self._oms_key: + self._oms_key = hashlib.sha256(self._oms_key).digest() diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index 2095cb29..b5af76b2 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -171,6 +171,30 @@ class Ids(IntEnum): DB_ACCESS_AREA_BASE = 0x8A0E0000 +# Function codes that use the READ IntegrityId counter (V2+) +READ_FUNCTION_CODES: frozenset[int] = frozenset( + { + FunctionCode.GET_MULTI_VARIABLES, + FunctionCode.EXPLORE, + FunctionCode.GET_VAR_SUBSTREAMED, + FunctionCode.GET_LINK, + FunctionCode.GET_VARIABLE, + FunctionCode.GET_VARIABLES_ADDRESS, + } +) + + +class LegitimationId(IntEnum): + """Legitimation IDs used in password authentication (V2+). + + Reference: thomas-v2/S7CommPlusDriver + """ + + SERVER_SESSION_REQUEST = 303 + SERVER_SESSION_RESPONSE = 304 + LEGITIMATE = 1846 + + class SoftDataType(IntEnum): """PLC soft data types (used in variable metadata / tag descriptions). diff --git a/snap7/s7commplus/server.py b/snap7/s7commplus/server.py index 27c54adc..2af0d769 100644 --- a/snap7/s7commplus/server.py +++ b/snap7/s7commplus/server.py @@ -8,11 +8,9 @@ - Explore (browse registered data blocks and variables) - GetMultiVariables / SetMultiVariables (read/write by address) - Internal PLC memory model with thread-safe access +- V2 protocol emulation with TLS and IntegrityId tracking -This server does NOT implement TLS or the proprietary authentication -layers (V2/V3 crypto). It emulates a V1 PLC for testing purposes, -which is sufficient for validating protocol framing, data encoding, -and client logic. +Supports both V1 (no TLS) and V2 (TLS + IntegrityId) emulation. Usage:: @@ -20,13 +18,14 @@ server.register_db(1, {"temperature": ("Real", 0), "pressure": ("Real", 4)}) server.start(port=11020) - # ... run tests against localhost:11020 ... - - server.stop() + # V2 server with TLS: + server = S7CommPlusServer(protocol_version=ProtocolVersion.V2) + server.start(port=11020, use_tls=True, tls_cert="cert.pem", tls_key="key.pem") """ import logging import socket +import ssl import struct import threading from enum import IntEnum @@ -38,6 +37,7 @@ FunctionCode, Opcode, ProtocolVersion, + READ_FUNCTION_CODES, SoftDataType, ) from .vlq import encode_uint32_vlq, decode_uint32_vlq, encode_uint64_vlq @@ -186,15 +186,16 @@ class S7CommPlusServer: Emulates an S7-1200/1500 PLC with: - Internal data block storage with named variables - - S7CommPlus protocol handling (V1 level) + - S7CommPlus protocol handling (V1 and V2) + - V2 TLS support with IntegrityId tracking - Multi-client support (threaded) - CPU state management """ - def __init__(self) -> None: + def __init__(self, protocol_version: int = ProtocolVersion.V1) -> None: self._data_blocks: dict[int, DataBlock] = {} self._cpu_state = CPUState.RUN - self._protocol_version = ProtocolVersion.V1 + self._protocol_version = protocol_version self._next_session_id = 1 self._server_socket: Optional[socket.socket] = None @@ -204,6 +205,10 @@ def __init__(self) -> None: self._lock = threading.Lock() self._event_callback: Optional[Callable[..., None]] = None + # TLS configuration (V2) + self._ssl_context: Optional[ssl.SSLContext] = None + self._use_tls: bool = False + @property def cpu_state(self) -> CPUState: return self._cpu_state @@ -258,16 +263,41 @@ def get_db(self, db_number: int) -> Optional[DataBlock]: """Get a registered data block.""" return self._data_blocks.get(db_number) - def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: + def start( + self, + host: str = "0.0.0.0", + port: int = 11020, + use_tls: bool = False, + tls_cert: Optional[str] = None, + tls_key: Optional[str] = None, + tls_ca: Optional[str] = None, + ) -> None: """Start the server. Args: host: Bind address port: TCP port to listen on + use_tls: Whether to wrap client sockets with TLS after InitSSL + tls_cert: Path to server TLS certificate (PEM) + tls_key: Path to server private key (PEM) + tls_ca: Path to CA certificate for client verification (PEM) """ if self._running: raise RuntimeError("Server is already running") + self._use_tls = use_tls + if use_tls: + if not tls_cert or not tls_key: + raise ValueError("TLS requires tls_cert and tls_key") + self._ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER) + self._ssl_context.minimum_version = ssl.TLSVersion.TLSv1_3 + self._ssl_context.load_cert_chain(tls_cert, tls_key) + if tls_ca: + self._ssl_context.load_verify_locations(tls_ca) + self._ssl_context.verify_mode = ssl.CERT_REQUIRED + else: + self._ssl_context.verify_mode = ssl.CERT_NONE + self._server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) self._server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self._server_socket.settimeout(1.0) @@ -277,7 +307,7 @@ def start(self, host: str = "0.0.0.0", port: int = 11020) -> None: self._running = True self._server_thread = threading.Thread(target=self._server_loop, daemon=True, name="s7commplus-server") self._server_thread.start() - logger.info(f"S7CommPlus server started on {host}:{port}") + logger.info(f"S7CommPlus server started on {host}:{port} (TLS={use_tls}, V{self._protocol_version})") def stop(self) -> None: """Stop the server.""" @@ -332,6 +362,10 @@ def _handle_client(self, client_sock: socket.socket, address: tuple[str, int]) - # Step 2: S7CommPlus session session_id = 0 + tls_activated = False + # Per-client IntegrityId tracking (V2+) + integrity_id_read = 0 + integrity_id_write = 0 while self._running: try: @@ -341,16 +375,53 @@ def _handle_client(self, client_sock: socket.socket, address: tuple[str, int]) - break # Process the S7CommPlus request - response = self._process_request(data, session_id) + response = self._process_request(data, session_id, integrity_id_read, integrity_id_write) if response is not None: # Check if session ID was assigned if session_id == 0 and len(response) >= 14: - # Extract session ID from response for tracking session_id = struct.unpack_from(">I", response, 9)[0] self._send_s7commplus_frame(client_sock, response) + # After InitSSL response, activate TLS if configured + if ( + not tls_activated + and self._use_tls + and self._ssl_context is not None + and data is not None + and len(data) >= 8 + ): + # Check if this was an InitSSL request + try: + _, _, hdr_consumed = decode_header(data) + payload = data[hdr_consumed:] + if len(payload) >= 14: + func_code = struct.unpack_from(">H", payload, 3)[0] + if func_code == FunctionCode.INIT_SSL: + client_sock = self._ssl_context.wrap_socket(client_sock, server_side=True) + tls_activated = True + logger.debug(f"TLS activated for client {address}") + except (ValueError, struct.error): + pass + + # Update IntegrityId counters based on function code (V2+) + if self._protocol_version >= ProtocolVersion.V2 and session_id != 0: + try: + _, _, hdr_consumed = decode_header(data) + payload = data[hdr_consumed:] + if len(payload) >= 14: + func_code = struct.unpack_from(">H", payload, 3)[0] + if func_code in READ_FUNCTION_CODES: + integrity_id_read = (integrity_id_read + 1) & 0xFFFFFFFF + elif func_code not in ( + FunctionCode.INIT_SSL, + FunctionCode.CREATE_OBJECT, + ): + integrity_id_write = (integrity_id_write + 1) & 0xFFFFFFFF + except (ValueError, struct.error): + pass + except socket.timeout: continue except (ConnectionError, OSError): @@ -445,7 +516,13 @@ def _send_s7commplus_frame(self, sock: socket.socket, data: bytes) -> None: tpkt = struct.pack(">BBH", 3, 0, 4 + len(cotp_dt)) + cotp_dt sock.sendall(tpkt) - def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: + def _process_request( + self, + data: bytes, + session_id: int, + integrity_id_read: int = 0, + integrity_id_write: int = 0, + ) -> Optional[bytes]: """Process an S7CommPlus request and return a response.""" if len(data) < 4: return None @@ -469,7 +546,19 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: function_code = struct.unpack_from(">H", payload, 3)[0] seq_num = struct.unpack_from(">H", payload, 7)[0] req_session_id = struct.unpack_from(">I", payload, 9)[0] - request_data = payload[14:] + + # For V2+, skip IntegrityId after the 14-byte header + request_offset = 14 + if ( + self._protocol_version >= ProtocolVersion.V2 + and session_id != 0 + and function_code not in (FunctionCode.INIT_SSL, FunctionCode.CREATE_OBJECT) + ): + if request_offset < len(payload): + _req_iid, iid_consumed = decode_uint32_vlq(payload, request_offset) + request_offset += iid_consumed + + request_data = payload[request_offset:] if function_code == FunctionCode.INIT_SSL: return self._handle_init_ssl(seq_num) @@ -486,6 +575,40 @@ def _process_request(self, data: bytes, session_id: int) -> Optional[bytes]: else: return self._build_error_response(seq_num, req_session_id, function_code) + def _build_response_header( + self, + function_code: int, + seq_num: int, + session_id: int, + include_integrity_id: bool = False, + integrity_id: int = 0, + ) -> bytes: + """Build a 14-byte response header, optionally with IntegrityId (V2+). + + Args: + function_code: Response function code + seq_num: Sequence number echoed from request + session_id: Session ID + include_integrity_id: If True, append VLQ IntegrityId after header + integrity_id: IntegrityId value to include + + Returns: + Response header bytes (14 bytes, or 14+VLQ for V2+) + """ + header = struct.pack( + ">BHHHHIB", + Opcode.RESPONSE, + 0x0000, + function_code, + 0x0000, + seq_num, + session_id, + 0x00, + ) + if include_integrity_id: + header += encode_uint32_vlq(integrity_id) + return header + def _handle_init_ssl(self, seq_num: int) -> bytes: """Handle InitSSL -- respond to SSL initialization (V1 emulation, no real TLS).""" response = bytearray() @@ -544,6 +667,14 @@ def _handle_create_object(self, seq_num: int, request_data: bytes) -> bytes: response += encode_uint32_vlq(0x0132) # Protocol version attribute response += encode_typed_value(DataType.USINT, self._protocol_version) + # ServerSessionVersion attribute (306) - required for session setup handshake + from .protocol import ObjectId + + response += bytes([ElementID.ATTRIBUTE]) + response += encode_uint32_vlq(ObjectId.SERVER_SESSION_VERSION) + response += bytes([0x00]) # flags + response += encode_typed_value(DataType.UDINT, self._protocol_version) + response += bytes([ElementID.TERMINATING_OBJECT]) # Trailing zeros diff --git a/tests/test_s7commplus_v2.py b/tests/test_s7commplus_v2.py new file mode 100644 index 00000000..59236f8f --- /dev/null +++ b/tests/test_s7commplus_v2.py @@ -0,0 +1,250 @@ +"""Tests for S7CommPlus V2 protocol support. + +Tests IntegrityId tracking, legitimation helpers, protocol constants, +and V2 connection behavior. +""" + +import hashlib + + +from snap7.s7commplus.protocol import ( + FunctionCode, + LegitimationId, + ProtocolVersion, + READ_FUNCTION_CODES, +) +from snap7.s7commplus.legitimation import ( + LegitimationState, + build_legacy_response, + derive_legitimation_key, + _build_legitimation_payload, +) +from snap7.s7commplus.vlq import encode_uint32_vlq, decode_uint32_vlq +from snap7.s7commplus.connection import S7CommPlusConnection + + +class TestReadFunctionCodes: + """Test READ_FUNCTION_CODES classification.""" + + def test_get_multi_variables_is_read(self) -> None: + assert FunctionCode.GET_MULTI_VARIABLES in READ_FUNCTION_CODES + + def test_explore_is_read(self) -> None: + assert FunctionCode.EXPLORE in READ_FUNCTION_CODES + + def test_get_var_substreamed_is_read(self) -> None: + assert FunctionCode.GET_VAR_SUBSTREAMED in READ_FUNCTION_CODES + + def test_get_link_is_read(self) -> None: + assert FunctionCode.GET_LINK in READ_FUNCTION_CODES + + def test_get_variable_is_read(self) -> None: + assert FunctionCode.GET_VARIABLE in READ_FUNCTION_CODES + + def test_get_variables_address_is_read(self) -> None: + assert FunctionCode.GET_VARIABLES_ADDRESS in READ_FUNCTION_CODES + + def test_set_multi_variables_is_write(self) -> None: + assert FunctionCode.SET_MULTI_VARIABLES not in READ_FUNCTION_CODES + + def test_set_variable_is_write(self) -> None: + assert FunctionCode.SET_VARIABLE not in READ_FUNCTION_CODES + + def test_create_object_is_write(self) -> None: + assert FunctionCode.CREATE_OBJECT not in READ_FUNCTION_CODES + + def test_delete_object_is_write(self) -> None: + assert FunctionCode.DELETE_OBJECT not in READ_FUNCTION_CODES + + +class TestLegitimationId: + """Test legitimation ID constants.""" + + def test_server_session_request(self) -> None: + assert int(LegitimationId.SERVER_SESSION_REQUEST) == 303 + + def test_server_session_response(self) -> None: + assert int(LegitimationId.SERVER_SESSION_RESPONSE) == 304 + + def test_legitimate(self) -> None: + assert int(LegitimationId.LEGITIMATE) == 1846 + + +class TestDeriveKey: + """Test OMS key derivation.""" + + def test_derive_returns_32_bytes(self) -> None: + secret = b"\x00" * 32 + key = derive_legitimation_key(secret) + assert len(key) == 32 + + def test_derive_is_sha256(self) -> None: + secret = b"test_oms_secret_material_32byte!" + key = derive_legitimation_key(secret) + expected = hashlib.sha256(secret).digest() + assert key == expected + + def test_different_secrets_different_keys(self) -> None: + key1 = derive_legitimation_key(b"\x00" * 32) + key2 = derive_legitimation_key(b"\x01" * 32) + assert key1 != key2 + + +class TestLegacyResponse: + """Test legacy legitimation (SHA-1 XOR).""" + + def test_legacy_response_length(self) -> None: + challenge = b"\x00" * 20 + response = build_legacy_response("password", challenge) + assert len(response) == 20 + + def test_legacy_response_xor(self) -> None: + password = "test" + challenge = b"\xff" * 20 + response = build_legacy_response(password, challenge) + password_hash = hashlib.sha1(password.encode("utf-8")).digest() # noqa: S324 + # XOR with 0xFF should flip all bits + expected = bytes(h ^ 0xFF for h in password_hash) + assert response == expected + + def test_legacy_response_zero_challenge(self) -> None: + password = "hello" + challenge = b"\x00" * 20 + response = build_legacy_response(password, challenge) + # XOR with zeros = original hash + expected = hashlib.sha1(password.encode("utf-8")).digest() # noqa: S324 + assert response == expected + + +class TestLegitimationPayload: + """Test legitimation payload building.""" + + def test_payload_without_username(self) -> None: + payload = _build_legitimation_payload("password") + assert len(payload) > 0 + # Should contain struct header + assert payload[1] == 0x17 # DataType.STRUCT + + def test_payload_with_username(self) -> None: + payload = _build_legitimation_payload("password", "admin") + assert len(payload) > 0 + + def test_payload_legit_type_1_without_username(self) -> None: + """Without username, legitimation type should be 1 (legacy).""" + payload = _build_legitimation_payload("password") + # After struct header (flags=0x00, type=0x17, count VLQ), the first + # element is flags=0x00, type=UDInt(0x04), then legit_type value + # The exact structure: [0x00, 0x17, count, 0x00, 0x04, legit_type, ...] + # legit_type=1 is at offset 5 (VLQ encoded) + assert payload[4] == 0x04 # UDInt type for legit_type + assert payload[5] == 0x01 # legit_type = 1 + + def test_payload_legit_type_2_with_username(self) -> None: + """With username, legitimation type should be 2 (new).""" + payload = _build_legitimation_payload("password", "admin") + assert payload[4] == 0x04 # UDInt type for legit_type + assert payload[5] == 0x02 # legit_type = 2 + + +class TestLegitimationState: + """Test LegitimationState tracker.""" + + def test_initial_state_not_authenticated(self) -> None: + state = LegitimationState() + assert not state.authenticated + + def test_mark_authenticated(self) -> None: + state = LegitimationState() + state.mark_authenticated() + assert state.authenticated + + def test_with_oms_secret(self) -> None: + state = LegitimationState(oms_secret=b"\x00" * 32) + assert not state.authenticated + + def test_rotate_key(self) -> None: + state = LegitimationState(oms_secret=b"\x00" * 32) + # Should not raise + state.rotate_key() + + def test_rotate_key_without_secret(self) -> None: + state = LegitimationState() + # Should not raise even without OMS secret + state.rotate_key() + + +class TestIntegrityIdTracking: + """Test IntegrityId counter logic in S7CommPlusConnection.""" + + def test_initial_counters_zero(self) -> None: + conn = S7CommPlusConnection("127.0.0.1") + assert conn.integrity_id_read == 0 + assert conn.integrity_id_write == 0 + + def test_connection_attributes(self) -> None: + conn = S7CommPlusConnection("127.0.0.1") + assert conn.oms_secret is None + assert not conn.tls_active + + def test_protocol_version_default(self) -> None: + conn = S7CommPlusConnection("127.0.0.1") + assert conn.protocol_version == 0 + + +class TestIntegrityIdVlqEncoding: + """Test VLQ encoding used for IntegrityId values.""" + + def test_encode_zero(self) -> None: + assert encode_uint32_vlq(0) == b"\x00" + + def test_encode_small(self) -> None: + encoded = encode_uint32_vlq(42) + value, _ = decode_uint32_vlq(encoded) + assert value == 42 + + def test_encode_large(self) -> None: + encoded = encode_uint32_vlq(0xFFFFFFFF) + value, _ = decode_uint32_vlq(encoded) + assert value == 0xFFFFFFFF + + def test_roundtrip_integrity_range(self) -> None: + """Test encoding/decoding typical IntegrityId counter values.""" + for val in [0, 1, 127, 128, 255, 1000, 65535, 0x7FFFFFFF]: + encoded = encode_uint32_vlq(val) + decoded, consumed = decode_uint32_vlq(encoded) + assert decoded == val + assert consumed == len(encoded) + + +class TestProtocolVersionV2: + """Test V2 protocol version constant.""" + + def test_v2_value(self) -> None: + assert int(ProtocolVersion.V2) == 0x02 + + def test_v2_greater_than_v1(self) -> None: + assert ProtocolVersion.V2 > ProtocolVersion.V1 + + def test_v2_less_than_v3(self) -> None: + assert ProtocolVersion.V2 < ProtocolVersion.V3 + + +class TestNewResponseNotImplemented: + """Test that build_new_response raises NotImplementedError without cryptography.""" + + def test_new_response_requires_cryptography(self) -> None: + from snap7.s7commplus.legitimation import build_new_response + + # This may or may not raise depending on whether cryptography is installed + # We test the function signature is correct + try: + result = build_new_response( + password="test", + challenge=b"\x00" * 16, + oms_secret=b"\x00" * 32, + ) + # If cryptography is installed, result should be bytes + assert isinstance(result, bytes) + except NotImplementedError: + # Expected when cryptography is not installed + pass From 4fd702a52ac9d4d13504fe95bc55e0f839fbd4e5 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Fri, 20 Mar 2026 10:35:08 +0200 Subject: [PATCH 25/27] Complete V2 legitimation with cryptography optional dependency - Add cryptography as optional dep: pip install python-snap7[s7commplus] - Implement connection.authenticate() with challenge/response flow - Wire up legitimation in client.connect(password=...) - Auto-detect legacy (SHA-1 XOR) vs new (AES-256-CBC) auth mode - Add legitimation protocol methods: get challenge, send response - 46 tests now (was 39), including AES roundtrip verification Co-Authored-By: Claude Opus 4.6 --- pyproject.toml | 1 + snap7/s7commplus/client.py | 8 +- snap7/s7commplus/connection.py | 170 +++++++++++++++++++++++++++++++ snap7/s7commplus/legitimation.py | 2 +- tests/test_s7commplus_v2.py | 117 ++++++++++++++++++--- uv.lock | 157 +++++++++++++++++++++++++++- 6 files changed, 431 insertions(+), 24 deletions(-) diff --git a/pyproject.toml b/pyproject.toml index 3e28ea7b..c3714c0f 100644 --- a/pyproject.toml +++ b/pyproject.toml @@ -33,6 +33,7 @@ Documentation = "https://python-snap7.readthedocs.io/en/latest/" [project.optional-dependencies] test = ["pytest", "pytest-asyncio", "pytest-cov", "pytest-html", "mypy", "types-setuptools", "ruff", "tox", "tox-uv", "types-click", "uv"] +s7commplus = ["cryptography"] cli = ["rich", "click" ] doc = ["sphinx", "sphinx_rtd_theme"] diff --git a/snap7/s7commplus/client.py b/snap7/s7commplus/client.py index 8ccfe812..44112c9c 100644 --- a/snap7/s7commplus/client.py +++ b/snap7/s7commplus/client.py @@ -144,13 +144,9 @@ def connect( ) # Handle legitimation for password-protected PLCs - if password is not None and self._connection.tls_active and self._connection.oms_secret is not None: + if password is not None and self._connection.tls_active: logger.info("Performing PLC legitimation (password authentication)") - # Legitimation requires the cryptography package for new-style auth - # For now, raise NotImplementedError - callers should catch this - raise NotImplementedError( - "PLC password legitimation is not yet implemented. Connection works without password for unprotected PLCs." - ) + self._connection.authenticate(password) # Probe S7CommPlus data operations with a minimal request if not self._probe_s7commplus_data(): diff --git a/snap7/s7commplus/connection.py b/snap7/s7commplus/connection.py index 9489d6bb..a60b44a0 100644 --- a/snap7/s7commplus/connection.py +++ b/snap7/s7commplus/connection.py @@ -230,6 +230,176 @@ def connect( self.disconnect() raise + def authenticate(self, password: str, username: str = "") -> None: + """Perform PLC password authentication (legitimation). + + Must be called after connect() and before data operations on + password-protected PLCs. Requires TLS to be active (V2+). + + The method auto-detects legacy vs new legitimation based on + the PLC's firmware version (stored in ServerSessionVersion). + + Args: + password: PLC password + username: Username for new-style auth (optional) + + Raises: + S7ConnectionError: If not connected, TLS not active, or auth fails + """ + if not self._connected: + from ..error import S7ConnectionError + + raise S7ConnectionError("Not connected") + + if not self._tls_active or self._oms_secret is None: + from ..error import S7ConnectionError + + raise S7ConnectionError("Legitimation requires TLS. Connect with use_tls=True.") + + # Step 1: Get challenge from PLC via GetVarSubStreamed + challenge = self._get_legitimation_challenge() + logger.info(f"Received legitimation challenge ({len(challenge)} bytes)") + + # Step 2: Build response (auto-detect legacy vs new) + from .legitimation import build_legacy_response, build_new_response + + if username: + # New-style auth with username always uses AES-256-CBC + response_data = build_new_response(password, challenge, self._oms_secret, username) + self._send_legitimation_new(response_data) + else: + # Try new-style first, fall back to legacy SHA-1 XOR + try: + response_data = build_new_response(password, challenge, self._oms_secret, "") + self._send_legitimation_new(response_data) + except NotImplementedError: + # cryptography package not available, use legacy + response_data = build_legacy_response(password, challenge) + self._send_legitimation_legacy(response_data) + + logger.info("PLC legitimation completed successfully") + + def _get_legitimation_challenge(self) -> bytes: + """Request legitimation challenge from PLC. + + Sends GetVarSubStreamed with address ServerSessionRequest (303). + + Returns: + Challenge bytes from PLC (typically 20 bytes) + """ + from .protocol import LegitimationId + + # Build GetVarSubStreamed request + payload = bytearray() + # InObjectId = session ID + payload += struct.pack(">I", self._session_id) + # Item count = 1 + payload += encode_uint32_vlq(1) + # Address field count = 1 + payload += encode_uint32_vlq(1) + # Address = ServerSessionRequest (303) + payload += encode_uint32_vlq(LegitimationId.SERVER_SESSION_REQUEST) + # Trailing padding + payload += struct.pack(">I", 0) + + resp_payload = self.send_request(FunctionCode.GET_VAR_SUBSTREAMED, bytes(payload)) + + # Parse response: return value + value list + offset = 0 + return_value, consumed = decode_uint64_vlq(resp_payload, offset) + offset += consumed + + if return_value != 0: + from ..error import S7ConnectionError + + raise S7ConnectionError(f"GetVarSubStreamed for challenge failed: return_value={return_value}") + + # Value is a USIntArray (BLOB) - read flags + type + length + data + if offset + 2 > len(resp_payload): + from ..error import S7ConnectionError + + raise S7ConnectionError("Challenge response too short") + + _flags = resp_payload[offset] + datatype = resp_payload[offset + 1] + offset += 2 + + from .protocol import DataType + + if datatype == DataType.BLOB: + length, consumed = decode_uint32_vlq(resp_payload, offset) + offset += consumed + return bytes(resp_payload[offset : offset + length]) + else: + # Try reading as array of USINT + count, consumed = decode_uint32_vlq(resp_payload, offset) + offset += consumed + return bytes(resp_payload[offset : offset + count]) + + def _send_legitimation_new(self, encrypted_response: bytes) -> None: + """Send new-style legitimation response (AES-256-CBC encrypted). + + Uses SetVariable with address Legitimate (1846). + """ + from .protocol import LegitimationId, DataType + + payload = bytearray() + # InObjectId = session ID + payload += struct.pack(">I", self._session_id) + # Address field count = 1 + payload += encode_uint32_vlq(1) + # Address = Legitimate (1846) + payload += encode_uint32_vlq(LegitimationId.LEGITIMATE) + # Value: BLOB(0, encrypted_response) + payload += bytes([0x00, DataType.BLOB]) + payload += encode_uint32_vlq(len(encrypted_response)) + payload += encrypted_response + # Trailing padding + payload += struct.pack(">I", 0) + + resp_payload = self.send_request(FunctionCode.SET_VARIABLE, bytes(payload)) + + # Check return value + if len(resp_payload) >= 1: + return_value, _ = decode_uint64_vlq(resp_payload, 0) + if return_value < 0: + from ..error import S7ConnectionError + + raise S7ConnectionError(f"Legitimation rejected by PLC: return_value={return_value}") + logger.debug(f"New legitimation return_value={return_value}") + + def _send_legitimation_legacy(self, response: bytes) -> None: + """Send legacy legitimation response (SHA-1 XOR). + + Uses SetVariable with address ServerSessionResponse (304). + """ + from .protocol import LegitimationId, DataType + + payload = bytearray() + # InObjectId = session ID + payload += struct.pack(">I", self._session_id) + # Address field count = 1 + payload += encode_uint32_vlq(1) + # Address = ServerSessionResponse (304) + payload += encode_uint32_vlq(LegitimationId.SERVER_SESSION_RESPONSE) + # Value: array of USINT (the XOR'd response bytes) + payload += bytes([0x10, DataType.USINT]) # flags=0x10 (array) + payload += encode_uint32_vlq(len(response)) + payload += response + # Trailing padding + payload += struct.pack(">I", 0) + + resp_payload = self.send_request(FunctionCode.SET_VARIABLE, bytes(payload)) + + # Check return value + if len(resp_payload) >= 1: + return_value, _ = decode_uint64_vlq(resp_payload, 0) + if return_value < 0: + from ..error import S7ConnectionError + + raise S7ConnectionError(f"Legacy legitimation rejected by PLC: return_value={return_value}") + logger.debug(f"Legacy legitimation return_value={return_value}") + def disconnect(self) -> None: """Disconnect from PLC.""" if self._connected and self._session_id: diff --git a/snap7/s7commplus/legitimation.py b/snap7/s7commplus/legitimation.py index 75d7cdce..2c8e197e 100644 --- a/snap7/s7commplus/legitimation.py +++ b/snap7/s7commplus/legitimation.py @@ -72,7 +72,7 @@ def build_new_response( from cryptography.hazmat.primitives import padding except ImportError: raise NotImplementedError( - "AES-256-CBC legitimation requires the 'cryptography' package. Install with: pip install cryptography" + "AES-256-CBC legitimation requires the 'cryptography' package. Install with: pip install python-snap7[s7commplus]" ) key = derive_legitimation_key(oms_secret) diff --git a/tests/test_s7commplus_v2.py b/tests/test_s7commplus_v2.py index 59236f8f..8638ada5 100644 --- a/tests/test_s7commplus_v2.py +++ b/tests/test_s7commplus_v2.py @@ -229,22 +229,107 @@ def test_v2_less_than_v3(self) -> None: assert ProtocolVersion.V2 < ProtocolVersion.V3 -class TestNewResponseNotImplemented: - """Test that build_new_response raises NotImplementedError without cryptography.""" +class TestBuildNewResponse: + """Test AES-256-CBC legitimation response building.""" - def test_new_response_requires_cryptography(self) -> None: + def test_new_response_returns_bytes(self) -> None: from snap7.s7commplus.legitimation import build_new_response - # This may or may not raise depending on whether cryptography is installed - # We test the function signature is correct - try: - result = build_new_response( - password="test", - challenge=b"\x00" * 16, - oms_secret=b"\x00" * 32, - ) - # If cryptography is installed, result should be bytes - assert isinstance(result, bytes) - except NotImplementedError: - # Expected when cryptography is not installed - pass + result = build_new_response( + password="test", + challenge=b"\x00" * 16, + oms_secret=b"\x00" * 32, + ) + assert isinstance(result, bytes) + + def test_new_response_is_aes_block_aligned(self) -> None: + from snap7.s7commplus.legitimation import build_new_response + + result = build_new_response( + password="test", + challenge=b"\x00" * 16, + oms_secret=b"\x00" * 32, + ) + # AES-CBC output is always a multiple of 16 bytes + assert len(result) % 16 == 0 + + def test_new_response_different_passwords_differ(self) -> None: + from snap7.s7commplus.legitimation import build_new_response + + challenge = b"\xab" * 16 + oms = b"\xcd" * 32 + r1 = build_new_response("password1", challenge, oms) + r2 = build_new_response("password2", challenge, oms) + assert r1 != r2 + + def test_new_response_different_secrets_differ(self) -> None: + from snap7.s7commplus.legitimation import build_new_response + + challenge = b"\xab" * 16 + r1 = build_new_response("test", challenge, b"\x00" * 32) + r2 = build_new_response("test", challenge, b"\x01" * 32) + assert r1 != r2 + + def test_new_response_with_username(self) -> None: + from snap7.s7commplus.legitimation import build_new_response + + result = build_new_response( + password="test", + challenge=b"\x00" * 16, + oms_secret=b"\x00" * 32, + username="admin", + ) + assert isinstance(result, bytes) + assert len(result) % 16 == 0 + + def test_new_response_decryptable(self) -> None: + """Verify the response can be decrypted back to the original payload.""" + from snap7.s7commplus.legitimation import ( + build_new_response, + derive_legitimation_key, + _build_legitimation_payload, + ) + from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes + from cryptography.hazmat.primitives import padding + + challenge = b"\x12\x34\x56\x78" * 4 # 16-byte IV + oms_secret = b"\xaa\xbb\xcc\xdd" * 8 # 32 bytes + + encrypted = build_new_response("mypassword", challenge, oms_secret) + + # Decrypt + key = derive_legitimation_key(oms_secret) + iv = challenge[:16] + cipher = Cipher(algorithms.AES(key), modes.CBC(iv)) + decryptor = cipher.decryptor() + padded = decryptor.update(encrypted) + decryptor.finalize() + + # Remove PKCS7 padding + unpadder = padding.PKCS7(128).unpadder() + plaintext = unpadder.update(padded) + unpadder.finalize() + + # Should match the payload + expected = _build_legitimation_payload("mypassword") + assert plaintext == expected + + +class TestAuthenticate: + """Test connection.authenticate() preconditions.""" + + def test_authenticate_requires_connection(self) -> None: + import pytest + from snap7.error import S7ConnectionError + + conn = S7CommPlusConnection("127.0.0.1") + with pytest.raises(S7ConnectionError, match="Not connected"): + conn.authenticate("password") + + def test_authenticate_requires_tls(self) -> None: + 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}, { name = "pytest", marker = "extra == 'test'" }, { name = "pytest-asyncio", marker = "extra == 'test'" }, @@ -811,7 +966,7 @@ requires-dist = [ { name = "types-setuptools", marker = "extra == 'test'" }, { name = "uv", marker = "extra == 'test'" }, ] -provides-extras = ["test", "cli", "doc"] +provides-extras = ["test", "s7commplus", "cli", "doc"] [[package]] name = "requests" From 645cca468ae84322b1a9589711b9785f046a978d Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Tue, 24 Mar 2026 15:34:00 +0200 Subject: [PATCH 26/27] Fix CI: skip V2 crypto tests when cryptography not installed - Skip TestBuildNewResponse when cryptography package is unavailable (CI only installs [test] extras, not [s7commplus]) - Fix extra blank line in protocol.py that failed ruff format check Co-Authored-By: Claude Opus 4.6 --- snap7/s7commplus/protocol.py | 1 - tests/test_s7commplus_v2.py | 10 ++++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/snap7/s7commplus/protocol.py b/snap7/s7commplus/protocol.py index bc2f2a3c..b5af76b2 100644 --- a/snap7/s7commplus/protocol.py +++ b/snap7/s7commplus/protocol.py @@ -195,7 +195,6 @@ class LegitimationId(IntEnum): LEGITIMATE = 1846 - class SoftDataType(IntEnum): """PLC soft data types (used in variable metadata / tag descriptions). diff --git a/tests/test_s7commplus_v2.py b/tests/test_s7commplus_v2.py index 8638ada5..1a9fc8e7 100644 --- a/tests/test_s7commplus_v2.py +++ b/tests/test_s7commplus_v2.py @@ -6,6 +6,7 @@ import hashlib +import pytest from snap7.s7commplus.protocol import ( FunctionCode, @@ -229,6 +230,15 @@ def test_v2_less_than_v3(self) -> None: assert ProtocolVersion.V2 < ProtocolVersion.V3 +try: + import cryptography # noqa: F401 + + _has_cryptography = True +except ImportError: + _has_cryptography = False + + +@pytest.mark.skipif(not _has_cryptography, reason="requires cryptography package") class TestBuildNewResponse: """Test AES-256-CBC legitimation response building.""" From 23ed549a78bbc0afce723e1ceb62edb05a1ea1a8 Mon Sep 17 00:00:00 2001 From: Gijs Molenaar Date: Tue, 24 Mar 2026 15:35:12 +0200 Subject: [PATCH 27/27] Install s7commplus extras in CI to test cryptography-dependent code Co-Authored-By: Claude Opus 4.6 --- .github/workflows/test.yml | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml index beb9027c..b5ef98cc 100644 --- a/.github/workflows/test.yml +++ b/.github/workflows/test.yml @@ -30,6 +30,6 @@ jobs: - name: Install dependencies run: | uv venv --python python${{ matrix.python-version }} - uv pip install ".[test]" + uv pip install ".[test,s7commplus]" - name: Run pytest run: uv run pytest --cov=snap7 --cov-report=term