test(sandbox): a static AST guard pins the codec and worker import boundary (BACKLOG #346) - #252
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wshallwshall wants to merge 2 commits into
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test(sandbox): a static AST guard pins the codec and worker import boundary (BACKLOG #346)#252wshallwshall wants to merge 2 commits into
wshallwshall wants to merge 2 commits into
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…ry (BACKLOG #346) The sandbox's import boundary (DEFAULT_FORBIDDEN_MODULES in pipeline/sandbox.py -- socket/ssl/asyncio, the I/O- and secret-bearing messagefoundry.* subpackages, cryptography) is enforced only at RUNTIME and only inside the off-by-default [sandbox].mode=subprocess child. Nothing statically pins that the two modules which run inside that boundary -- _sandbox_codec.py and _sandbox_worker.py -- do not themselves import a forbidden module. Both are clean today; a future edit reintroducing a forbidden import would make mode=subprocess DOA on first deployment while the default-mode suite stayed green -- the failure inverts, hitting the most security-conscious installs hardest and quietest. This is defence-in-depth test coverage, not a code change: neither sandbox.py nor the codec is touched. tests/test_sandbox_import_boundary.py walks the two files' own ast import nodes (ast.Import/ast.ImportFrom, including nested/function-level and relative imports resolved to absolute) and asserts none resolves under a DEFAULT_FORBIDDEN_MODULES prefix. The forbidden set is imported from the runtime constant, never copied, so the guard tracks whatever the sandbox forbids. It ships with a positive control (each static import form the walker handles is seen, including the load-bearing from-parent alias-append) and a negative control (benign messagefoundry.* imports raise zero flags). Scope is the two files' DIRECT imports, deliberately not a transitive walk: importing the codec pulls asyncio/cryptography/store/transports/auth into sys.modules, so a transitive walker would red on clean shipped code and prove nothing. sandbox.py is out of scope per BACKLOG #346 even though the worker child imports it; the docstring records that residual for the owner. Falsified: planting `import socket` into the real _sandbox_codec.py reddens the live guard naming it; removing the walker's alias-append reddens only the alias-append positive-control case; an over-broad matcher reddens the negative control. All plants restored before commit.
… landed (BACKLOG #346) The #346 banner alone: OPEN -> SHIPPED, pointing at tests/test_sandbox_import_boundary.py (the static ast guard added in the preceding commit). The completeness wording is softened from "every forbidden import form is seen" to "each static import form the walker handles" -- a static walker cannot see dynamic importlib/__import__ forms, and CLAUDE.md section 11 prefers a bounded claim to an enumeration. Only the #346 banner line changed; the ranked table, the four census distribution lines, and every other item's banner are untouched. The census was NOT recomputed.
wshallwshall
enabled auto-merge (squash)
August 6, 2026 14:16
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Fixes BACKLOG #346. Test-only.
A static AST guard pins the sandbox codec plus worker import boundary, so a future import that
crosses it fails at test time rather than at runtime in a sandboxed worker.
VERIFIED 3/3: the live guard, a POSITIVE control, and a NEGATIVE control. The negative control is the
part that matters -- it proves the guard can actually fail, rather than passing because it inspects
nothing. Commit messages glyph-free; banner gate OK.