Detects binary/config tampering by content hash — catching a malicious swap
even when mtime is preserved (the gap in mtime-based persistence checks). Two
engines split by file ownership:
- fim.py hash baseline: SHA-256 (+ mode/uid/gid/size) of security-critical
files the package manager doesn't track (/usr/local, /etc configs, systemd
units, SSH keys). The baseline refreshes ONLY via fim-update / the pacman
hook, so a flagged change stays flagged until acknowledged (Tripwire
semantics). Alerts: fim_modified 100017 / fim_added 100018 / fim_removed 100019.
- package verification: `pacman -Qkk` checks package-owned binaries against the
distro's own signed checksums — no baseline to maintain, implicitly current
because the package DB updates on every upgrade. fim_pkg_modified 100020.
Auto-update on system updates: a pacman PostTransaction hook runs
`enodia-sentinel fim-update` after every install/upgrade/remove, so legitimate
package changes never alert — no manual `tripwire --update`.
- daemon: backgrounded FIM scan + optional pkg-verify on slow cadences, feeding
the normal alert/snapshot/push pipeline; baseline loaded/built at startup
- cli: fim-baseline / fim-update / fim-check [--packages]
- config: fim_enabled, fim_paths, fim_scan_interval, fim_pkg_verify[_interval]
- packaging: ship + install the pacman hook (Makefile + PKGBUILD)
- tests: +7 (hashing, diff incl. mtime-preserving tamper, pacman -Qkk parse).
72/72 pass. Verified end-to-end: a content swap with preserved mtime is caught.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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