Pre-launch hardening for the hosted Astrolabe Cloud offering. Addresses
all five findings raised in #626 (Tim Kaufmann, code review of v0.65.0).
Re-verified against master before fixing.
Finding 3 (LLM-controllable user_id) — drop user_id from the public
signatures of provision_nextcloud_access, revoke_nextcloud_access,
check_provisioning_status, check_logged_in. Tool wrappers now always
derive identity from the verified AccessToken; user_id is no longer
accepted as MCP input. Adds parameterized CI-guard test that locks the
schema.
Finding 2 (predictable session cookie) — replace mcp_session=<user_id>
cookie with a cryptographically random session_id mapped server-side
(new browser_sessions table, alembic 005). Cookie value is opaque,
expires, revocable. SessionAuthBackend looks up user_id via the new
mapping and additionally requires a refresh token to fail closed.
Finding 4 (logout doesn't revoke refresh token) — oauth_logout now
calls the IdP revocation_endpoint (RFC 7009) when advertised, deletes
the stored refresh token regardless, and clears the browser_sessions
row. Cleanup is best-effort: logout always 302s.
Finding 1 (unverified ID token decodes) — verify_id_token helper does
JWKS signature + issuer + audience + exp + nonce checks per OIDC core
3.1.3.7. Used by both OAuth callback handlers (browser + MCP). Removes
the four "verify_signature: False" decodes that previously trusted IdP
claims unconditionally. Drops dead-code _validate_token_audience in
token_broker. Refactors token_utils + provisioning_decorator to read
user_id from the verified AccessToken instead of re-decoding the JWT.
Finding 5 (hardcoded Fernet keys in docker-compose.yml) — replace the
three inline TOKEN_ENCRYPTION_KEY values with required env var
interpolation; document in env.sample.
Test coverage: 4 new unit test modules (signature pinning, browser
sessions, ID-token verification, logout + revoke + session backend).
693 unit tests pass; ruff/format/ty clean.
Migration note: existing browser admin-UI sessions become invalid on
rollout (cookies are looked up against the new browser_sessions table,
which starts empty). Users re-login. MCP API access is unaffected.
Tracked on Astrolabe Cloud POC board card #37.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
