The guard feeds untrusted byte streams (tokenized binaries, remote cat
output) into OS-path and shell-text operations; every incident so far
(#76762, #77703, #77780, #78256, #77729) was hot-fixed with an except at
whichever frame crashed that week. tilllt's regression suite on #79454
showed 4 members of the class still open on merged main. Close the class
at three boundaries instead:
- _expand_candidate_path(): single ingestion chokepoint for path
candidates — reject NUL/empty tokens before any Path OS call and
tolerate ValueError/RuntimeError/OSError from expanduser (T1/T2, plus
the HOME-unset launchd crash). Both _resolve_terminal_script_path and
_resolve_script_path now go through it.
- _sanitize_remote_script_text(): apply the local-read contract (NUL =
binary = nothing to scan; >1MiB = fail closed) to whatever any
read_remote_script callback returns, at the recursion boundary — the
guard stops trusting its callbacks (T3/T4).
- contains_gateway_lifecycle_command_or_referenced_script() is now total
by construction: direct regex scans (pure string ops) run first; the
best-effort filesystem walk is wrapped so an unexpected failure logs a
warning and falls back to the direct-scan verdict instead of killing
every terminal command until gateway restart.
terminal_tool's remote fallback also bounds the read at the source
(head -c 1MiB+1 instead of cat), so a 166MB ELF never crosses the wire —
the superlinear-shlex 30-minute stall from #79838's field report drops
to a 0.02s fail-closed verdict.
Regression tests: tilllt's T1-T4 adopted verbatim, plus an adversarial
never-raises sweep (NUL paths, unset HOME, over-long paths) and a
walk-crash fallback test.
kshitij
c8d48b8b13