The hardening refactor that just landed closes the same-uid attack
surface (FS view, ptrace, /proc visibility, signals) for the web +
gameserver units via systemd directives plus system-wide
kernel.yama.ptrace_scope=2. Keeping the script-sandbox on a separate
uid was the inconsistent half-step — defense-in-depth only, with
build-time-idmap complexity attached. One principle wins: harden
once, share the uid.
scripts/libexec/left4me-script-sandbox: drop the idmap block (uid
lookups, STAGING setup, cleanup_staging trap, mount --bind
--map-users), switch User=/Group= to left4me, point BindPaths at
\$OVERLAY_DIR directly. Header comment updated to reflect
hardening-not-uid as the same-uid defense. nsenter self-wrap kept —
it's about mount-namespace escape, not uid.
Tests + comments + companion docs updated. Build-time-idmap and
overlay-idmap plans marked SUPERSEDED; user-uid-split spec revised
to "1 user is correct"; one-line update notes on the hardening
specs and the build-overlay-unit-design.
Companion ckn-bw commit removes the l4d2-sandbox user + group and
tightens /var/lib/left4me from 0711 → 0755 (the traverse-only mode
was specifically for the sandbox uid).
Pulls the 5 privileged helpers out of deploy/files/usr/local/{libexec,sbin}/
into top-level scripts/{libexec,sbin}/. They are application-inherent code
(invoked at runtime via sudo from l4d2host/l4d2web), not deploy artifacts —
the previous nesting under deploy/files/ confused source-of-truth with
install-target FHS layout.
deploy/ now means "reference exemplar": README explaining the target
layout, plus example sudoers / sysctl / sandbox-resolv.conf / env
templates / curated systemd units (the ones ckn-bw's reactor emits).
Anyone building a fresh deployment (other than ckn-bw) reads this tree.
Dead static artifacts deleted: left4me-apply-cake helper, left4me-cake
+ left4me-nft-mark service units, cake.env, left4me-mark.nft, and the
superseded deploy-test-server.sh installer.
Tests split to match the new shape:
- scripts/tests/{test_overlay,test_script_sandbox,test_systemctl_helper,
test_journalctl_helper,test_helpers_use_fixed_paths,test_sudoers_grants}.py
with shared fixtures in conftest.py
- deploy/tests/test_example_units.py (renamed from test_deploy_artifacts.py)
— slimmed to lock down the curated example units, sysctl, env templates
l4d2host/tests/test_overlay_helper.py: helper-source path updated to
scripts/libexec/left4me-overlay (was building the path segment-by-segment
under deploy/files/, missed by the path-prefix grep during pre-flight).
Runtime install-target paths (/usr/local/{libexec,sbin}/) unchanged, so
l4d2host/service_control.py, l4d2web/services/overlay_builders.py, the
sudoers grants, and the systemd units all keep their existing path
references.
Requires the matching ckn-bw change to bundles/left4me/items.py
(install_left4me_scripts repointed from /opt/left4me/src/deploy/files/...
to /opt/left4me/src/scripts/...). Left4me lands first so a fresh
git_deploy exposes the new source path before the bundle apply runs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
