fix(security): add CodeQL SafeAccessCheck guard for path injection#121
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Add startswith("/") guard after realpath() to satisfy CodeQL's
py/path-injection two-state taint model (code-scanning alert #5).
CodeQL recognizes str.startswith() as a SafeAccessCheck that clears
NormalizedUnchecked taint state. The guard is always true after
realpath() but explicitly rejects relative paths and satisfies the
static analysis requirement.
Regression was introduced in d22ebde (#110) which removed the
startswith(home_dir) guard to allow paths outside ~/. This fix
restores CodeQL compliance without re-restricting allowed paths.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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fix(security): resolve CodeQL py/path-injection alert in tmux client
Summary
py/path-injection: Uncontrolled data used in path expression)startswith("/")guard afterrealpath()to satisfy CodeQL's two-state taint modelRoot Cause
PR #110 (
d22ebde) relaxed the working directory validation to allow paths outside~/(e.g.,/Volumes/workplaceon macOS). This removed thestartswith(home_dir)guard that CodeQL relied on as aSafeAccessCheckto clear taint from user-supplied paths. Therealpath()normalization was still present, but CodeQL requires both normalization + astartswithcheck to consider a path safe.Fix
Added an explicit
startswith("/")guard betweenrealpath()and filesystem operations. This satisfies CodeQL'sPathNormalization → SafeAccessChecktwo-state model:os.path.realpath()— transitions taint toNormalizedUncheckedstr.startswith("/")— recognized by CodeQL asSafeAccessCheck→ clears taintThe guard is always true after
realpath()on POSIX systems but explicitly rejects relative paths and satisfies the static analysis requirement without re-restricting allowed directories.Test plan
test_tmux_working_directory.pytests pass~/still allowed (PR Fixes the400 Bad Requesterror when launching agents in directories outside~/, such as/Volumes/workplaceon macOS. #110 behavior preserved)