fix(hardware): resolve probe binaries via absolute path to block Windows CWD planting (BE-3434)

[mattmillerai]

ELI-5

comfy env peeks at your machine's hardware by running little programs like nvidia-smi and sysctl. Before this change it asked for them by bare name — and on Windows, "run nvidia-smi" means "look in the folder I'm standing in first." So if you cd into a folder a bad actor prepared and it contained a fake nvidia-smi.exe, comfy env would run their program. This change looks up the real program on your system PATH and runs it by its full absolute path instead, so the folder you happen to be in can't hijack the probe.

What & why

Follow-up to #562 (deferred review thread r3607162549). hardware.py's _run invoked probe binaries (nvidia-smi, rocm-smi, sysctl) by bare name. On Windows CreateProcess searches the current working directory, so running comfy env from an attacker-controlled directory could execute a planted nvidia-smi.exe (low severity, binary-planting).

Fix (comfy_cli/hardware.py):

• New _resolve_binary(name) resolves cmd[0] via shutil.which() (a trusted PATH lookup) and returns the absolute path; _run now invokes [resolved, *cmd[1:]]. If which returns None (binary absent) the probe is skipped, exactly matching the module's existing degrade-to-None contract.
• Windows defense-in-depth: shutil.which on Windows can itself resolve against the CWD, so a resolved path that provably lives inside os.getcwd() is additionally rejected (_is_within_cwd, using os.path.commonpath on realpath-resolved paths — component-wise, symlink-safe). A legitimate system binary (e.g. nvidia-smi.exe under System32) is unaffected.
• The timeout=5 bound and the never-raise contract are preserved (_resolve_binary/_is_within_cwd are fully wrapped and degrade to None/False).

POSIX is behavior-neutral: subprocess without shell=True already uses execvp (PATH search, never CWD), and shutil.which resolves the same binary — so only Windows semantics are tightened. This is why the CWD guard is Windows-gated.

Tests

tests/comfy_cli/test_hardware.py — added two classes (7 tests): _run invokes the resolved absolute path / skips when absent / never raises on resolve failure; the Windows CWD guard rejects a CWD-planted binary, allows a System32 binary, and is not applied off-Windows. Full module suite: 25 passed. ruff check + ruff format --check clean.

Notes / judgment calls

• Stacked on feat: add cross-platform hardware block to comfy env --json (BE-3399) #562 (matt/be-3399-hardware-block) because hardware.py only exists on that unmerged branch — base will auto-retarget to main when feat: add cross-platform hardware block to comfy env --json (BE-3399) #562 merges.
• Out of scope: cuda_detect.py has a similar bare-name nvidia-smi invocation, but it predates feat: add cross-platform hardware block to comfy env --json (BE-3399) #562 and this ticket scopes specifically to hardware.py:_run. Flagging for a possible separate follow-up.
• Kept shutil.which on the default PATH (rather than restricting to hardcoded system dirs) — the CWD-exclusion guard is the ticket's primary suggested mitigation and is more robust than an allowlist that could miss the NVIDIA driver's install location.

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[github-actions]

🔍 Cursor Review — Consolidated panel

Triggered by @mattmillerai.

Found 4 finding(s).

Severity	Count
🟡 Medium	1
🟢 Low	3

Panel: 6/8 reviewers contributed findings.

Reviewers that did not contribute: kimi-k2.5:adversarial (empty), kimi-k2.5:edge-case (empty)