Aari 04a85b307a
fix(sandbox): scrub abbreviated *_PASS vars and Postgres PGPASSFILE from skill env (#4026)
* fix(sandbox): scrub abbreviated *_PASS vars and Postgres PGPASSFILE from skill env

env_policy blocks the full PASSWORD/PASSWD spellings but not the ubiquitous
abbreviated _PASS form (DB_PASS, SMTP_PASS, MYSQL_PASS, ...), whose value is the
plaintext password itself, so every skill subprocess inherited it. Postgres's
file-based credential sources PGPASSFILE (.pgpass locator) and PGSERVICEFILE
(pg_service.conf, may carry a password) were likewise missed -- the psql analog
of the MYSQL_PWD/REDISCLI_AUTH no-flag sources #4018 added.

Collapse *PASSWORD*/*PASSWD* into a single *PASS* pattern (which subsumes both,
covers the abbreviated family, and catches PGPASSFILE) and add PGSERVICEFILE to
the exact-name denylist. *PASS* deliberately does not touch PWD/OLDPWD, which
carry no PASS substring. Capability-handle vars (KUBECONFIG, DOCKER_CONFIG,
GIT_ASKPASS, ...) are a broader, non-value-bearing class and are left out of
this fix.

test_secret_like_names_are_blocked already pins the contract; the new names are
added to its parametrize list (red before, green after) and the benign-names
test guards against over-scrubbing PWD/OLDPWD.

* test(sandbox): pin the *_ASKPASS over-scrub that *PASS* introduces

*PASS* also matches the credential-helper vars GIT_ASKPASS, SSH_ASKPASS and
SUDO_ASKPASS, which main inherits. Each names a program whose purpose is to hand
the caller a credential, so inheriting the pointer is the same leak class as
inheriting the value -- a skill can simply invoke it. Scrubbing them is intended;
pin all three in test_secret_like_names_are_blocked (red on main) so the
behaviour is a decision rather than a side effect of the pattern's shape.

test_benign_names_are_allowed could not have caught this: none of its 14 names
carries a PASS substring, so it passes identically before and after the
broadening and asserts nothing about it. Record that in its docstring -- the
absence of a benign PASS-bearing name is a decision, and PWD/OLDPWD are the
boundary the list does pin.

Also note the incidental COMPASS_*/BYPASS_* over-scrub in the module comment
(over-scrubbing is this module's fail-safe direction; required-secrets is the
escape hatch), and list PGPASSFILE alongside PGSERVICEFILE in AGENTS.md.
2026-07-10 14:05:47 +08:00
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