Brings the agent's secret-source system to parity with the desktop app's
`command` secrets provider (hermes-desktop src/main/secrets/commandProvider.ts),
so a vault helper configured for the desktop also resolves on the gateway/CLI.
NEW agent/secret_sources/command.py — ports the TS provider's security model:
- Runs a user-configured helper via `/bin/sh -c`; the requested key travels
ONLY in the HERMES_SECRET_KEY env var, never interpolated into the command
string, so a hostile key name is inert data (not code).
- parse_secret_output mirrors the TS parser: exact dotenv-key match wins; >=2
env-shaped lines without the wanted key -> None; otherwise a bare value;
base64 '='-padding disambiguation; cross-key misroute guard (a single
OTHER_KEY=realvalue line never leaks into a different wanted key).
- Hard 3s timeout (kills the whole process group via killpg, so a forking
helper can't keep the pipe open), 1 MiB output cap, POSIX-only (Windows
degrades to an empty result + warning). Every failure degrades to "no value";
it never raises and never blocks startup.
- Logs ONLY structured fields (code=/signal=/errno=) to stderr; the helper's
stderr is piped and DISCARDED; the command string and secret values are
never logged. Reuses bitwarden.py's FetchResult so env_loader consumes both
sources identically.
hermes_cli/env_loader.py — _apply_external_secret_sources now reads a unified
`secrets.provider` selector ("env" | "command" | "bitwarden"):
- provider=command routes to apply_command_secrets, records the provenance as
"command" in _SECRET_SOURCES (so format_secret_source_suffix labels keys
"(from command)" — already generic, not duplicated), and re-runs the ASCII
credential sanitizer like the bitwarden path.
- provider=bitwarden keeps the existing behavior byte-for-byte.
- env / unset is a no-op (today's default — zero change for existing users).
- BACK-COMPAT: a config with only `secrets.bitwarden.enabled: true` and no
`provider` key is treated as provider=bitwarden, so existing Bitwarden users
are unaffected.
Config (the provider selector, command path, timeouts) lives in config.yaml
under `secrets:` per the project rubric — only resolved secret VALUES touch env.
Tests: NEW tests/test_command_secret_source.py — 27 cases, E2E against a real
temp HERMES_HOME with real chmod+x shell helpers (not mocks): bare/dotenv/
base64 round-trip, cross-key misroute, injection-inert key (canary not
created), timeout kill within bound, non-zero-exit degrade, no-secret-in-logs,
precedence/override, dispatch via config.yaml provider:command, idempotency,
and back-compat bitwarden routing. 27 new + 50 baseline green; wider
secrets/env_loader/config surface 229 passed / 5 skipped, no regression.
