The docker-exec privilege-drop shim tests started a sleep container and
released the fixture as soon as `docker exec <c> true` returned 0. On
s6-overlay that succeeds almost immediately — ~0.05s in measurement —
long before the `01-hermes-setup` cont-init hook (docker/stage2-hook.sh)
has finished seeding + `chown hermes:hermes` config.yaml and running the
Python config migration (cont-init only fully settles at ~9.8s under
arm64 QEMU emulation).
`test_shim_opt_out_keeps_root` wipes config.yaml, writes it as root with
HERMES_DOCKER_EXEC_AS_ROOT=1, and asserts root:root ownership. When the
fixture released the test inside that ~10s window, stage2-hook's
boot-time `chown hermes:hermes config.yaml` raced the root-written file
and reset it to hermes:hermes — failing the assertion. The window is
invisible on native amd64 (stage2-hook completes in a blink) but wide
open under the arm64 build's QEMU emulation, which is why only build-arm64
flaked while build-amd64 stayed green.
Replace the responsiveness poll with a wait on the canonical
'cont-init finished' signal: $HERMES_HOME/logs/container-boot.log gaining
a `profile=default` line, written by 02-reconcile-profiles which s6 runs
strictly after 01-hermes-setup. Mirrors the readiness pattern already
used in test_container_restart.py. Also bumps the readiness timeout 20s->60s
to cover slow emulation.
No production code change — test-only hardening of a timing race.
When operators ran `docker exec <c> hermes login` (or anything else
that wrote under $HERMES_HOME) they defaulted to root, leaving
/opt/data/auth.json root:root mode 0600. The supervised gateway
(UID 10000) then couldn't read its own credentials and returned
"Provider authentication failed: Hermes is not logged into Nous
Portal" on every Telegram/Discord/etc. message — even though
`docker exec <c> hermes chat -q ping` (also root) succeeded because
root could read its own root-owned file. _load_auth_store swallowed
PermissionError as a parse failure and copied the file aside as
auth.json.corrupt, making the diagnostic more misleading.
Fix: install a privilege-drop shim at /opt/hermes/bin/hermes,
prepended ahead of the venv on PATH. When invoked as root the shim
exec's the real venv binary via `s6-setuidgid hermes` — so any file
the docker-exec session writes is uid-aligned with the supervised
processes. Non-root callers (the supervised processes themselves,
`docker exec --user hermes`, kanban subagents, anything inside the
container that's not coming through docker-exec) hit a single exec
to the absolute venv path with no privilege change.
Recursion is impossible: the shim exec's the venv binary by
absolute path (/opt/hermes/.venv/bin/hermes), so the second hop
cannot re-enter the shim regardless of PATH state. No sentinel env
var needed (unlike #33583's gateway-run redirect which DOES need
HERMES_S6_SUPERVISED_CHILD because there's no absolute-path
equivalent for the s6 dispatch).
Opt-out: `docker exec -e HERMES_DOCKER_EXEC_AS_ROOT=1 …` for
diagnostic sessions where the operator deliberately wants root.
Strict truthiness (1/true/yes case-insensitive); typos like `=0`
do not silently opt out, mirroring HERMES_GATEWAY_NO_SUPERVISE in
#33583.
If `s6-setuidgid` is missing (someone stripped s6-overlay in a
downstream fork), the shim exits 126 with a remediation message
pointing at `--user hermes` and the opt-out — never silently runs
as root.
Test plan:
- tests/docker/test_docker_exec_privilege_drop.py — 11 tests
- shim drops root to hermes uid (file ownership check)
- shim short-circuits for non-root docker exec
- HERMES_DOCKER_EXEC_AS_ROOT=1 keeps root
- strict-truthiness parametrization (5 falsy values reject)
- main CMD path unaffected (recursion guard)
- E2E: every file written by docker-exec is readable by uid 10000
- Full tests/docker/ harness: 32/32 pass against fresh image build
- shellcheck --severity=error: clean
- hadolint: clean
- Manual: reproduced the original symptom (root-owned auth.json)
by bypassing the shim; confirmed default docker-exec produces
hermes-owned files; confirmed opt-out env keeps root semantics.
Known follow-up: this prevents NEW instances of the bug. Volumes
that already have root:root /opt/data/auth.json from a pre-shim
image need a one-time `chown hermes:hermes` before rebooting onto
the new image. A stage2-hook chown sweep can self-heal that, but
is deferred per scope decision.
