Two defense-in-depth fixes surfaced by /sh-security-review (both were
unverified — no exploit — but cheaply strengthen the credential contract):
- dispatcher: wrap the requests.post/get in app_workflow_dispatcher and
app_run_locator in try/except that re-raises DispatcherError with the
exception TYPE only (`from None`). The no-token-in-a-propagating-exception
guarantee is now enforced by code, not by requests' incidental behavior.
- github_app: parse expires_at BEFORE caching the token and raise GitHubAppError
(scrubbed) on a malformed value, so a parse failure fails closed without
leaving a half-written cache (token set, expiry None) behind a bare ValueError.
Tests: +3 (transport-error scrub for both HTTP seams; malformed-expiry fail-closed
with no half-written cache). Full suite 1526 passing; ruff clean.
The P3 dispatcher's default seams shell out to gh/git, but the R720 box has
no gh and a read-only PAT with no Actions scope — so dispatch_apply_verify
returned no run_id and every task parked at verify ("dispatch unresolved").
Add a GitHub-App auth path: the box mints short-lived (~1h) installation
access tokens from the App private key and uses them for the three dispatch
seams, removing the gh dependency.
- agent_team/github_app.py (new): mint_installation_token (RS256 App JWT,
iss=app_id, iat backdated 60s, exp 9 min; POST /access_tokens) + a lazy
TokenProvider that caches and re-mints near expiry. Secret-safe: the JWT
and token are never logged, never in an exception message, never persisted.
- dispatcher.py: app_branch_pusher / app_workflow_dispatcher / app_run_locator
(additive; gh/git _default_* left untouched). Push auth rides a host-scoped
http.extraHeader via GIT_CONFIG_* env (token never in argv/ps); the REST
run locator maps id->databaseId / created_at->createdAt into select_run_id
and surfaces 4xx promptly instead of silently exhausting the poll window.
- coordinator.py: default_dispatch_node_factory binds the App seams when
AGENT_TEAM_GH_APP_ID / _INSTALLATION_ID / _PRIVATE_KEY are all set; partial
or unreadable config logs one warning and falls back to gh-default (never
raises at serve-start).
- requirements.txt: pin PyJWT, cryptography, requests (App seams + CI fetcher).
- DEPLOY-R720.md / README.md: App dispatch config, permission/scope audit,
env-precedence check, key rotation/revocation + incident response.
Tests: +18 (test_github_app.py new; dispatcher/coordinator additions) covering
JWT claims, cache/re-mint, token-scrub-on-error, REST field mapping + run-name
correlation, and the partial-env inert fallback. Full suite 1523 passing.
