Answers two hard questions: "what guards the hashes FIM trusts?" and "how do we
make the sensor itself hard to silently disable?" — within the honest limit that
a root attacker who shares your privileges can't be fully stopped on-box, only
made loud.
- pkgdb.py: guards the package DB that `pacman -Qkk` trusts. Anchors a
fingerprint of /var/lib/pacman/local (refreshed ONLY by the pacman hook) and
cross-checks pacman.log; a DB change with no logged transaction is flagged
pkgdb_tamper (CRITICAL, sid 100021) — catches an attacker rewriting a stored
checksum to mask a modified binary. Verified end-to-end against a simulated
hash-overwrite.
- selfprotect.py: Sentinel's own binaries/config/units/hook are always in the
FIM watch set (self-integrity); a heartbeat is written each loop; an external
`watchdog` command polls a remote dashboard and pushes if the sensor goes
silent or unreachable — silence becomes the alarm.
- daemon: heartbeat + slow-cadence pkgdb check; DB anchor re-anchored in
build_fim_baseline so the pacman hook refreshes it after each transaction
- web: /api/status now reports heartbeat_age/stale; dashboard shows it
- cli: pkgdb-check, watchdog (--url/--token/--max-age, bypasses min-severity)
- config: pkgdb_verify/_interval, heartbeat_max_age
- README: threat model (trust-anchor problem) + hardening layers (immutability,
signed-package + external anchor); reframes "anti-rootkit" as tamper-evidence
- tests: +8 (DB fingerprint, anchor/transaction logic, pacman.log parse,
heartbeat + watchdog verdicts). 80/80 pass
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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