feat(oauth): authorization-server endpoints (forgejo-mcp-broker-pur)

Implements internal/oauth, the broker's OAuth 2.1 AS surface that
Claude.ai (and other MCP clients) talk to. User authentication is
delegated to upstream Forgejo via internal/forgejo.

Endpoints:
  POST /oauth/register   — RFC 7591 dynamic client registration
  GET  /oauth/authorize  — RFC 6749 + 7636 PKCE (S256 only)
  GET  /oauth/callback   — Forgejo redirects back here after consent
  POST /oauth/token      — authorization_code + refresh_token grants
  POST /oauth/revoke     — RFC 7009

Security model:
- PKCE required, S256 only — plain method rejected per OAuth 2.1
- Every broker-issued access/refresh token stored as hex(sha256(plain));
  plaintext leaves the broker exactly once in the /token response body
- Refresh-token rotation: each refresh issues a new token pair and
  revokes the old refresh (RFC 6749 §10.4)
- Auth-code single-use enforced atomically via UPDATE...WHERE used_at IS
  NULL with rows-affected check, blocking the concurrent-replay race
- Issuer URL sourced from cfg.Issuer at construction time, never from
  inbound headers — prevents host-header injection on /.well-known
  metadata that ships in 2d
- redirect_uri must match a registered URI exactly (no prefix/wildcard)

Pending-authorization state (between /authorize and /callback) lives in
an in-memory sync.Map with a 1-minute reaper goroutine. A broker restart
drops them, forcing the user to re-authorize — acceptable trade-off
versus introducing a fifth table.

Tests: 81.0% coverage with ~20 cases across happy paths, every required-
field error, PKCE failure, code-replay, refresh expiry/revocation,
client-id and redirect-uri mismatches, Forgejo-side errors, and the
reaper logic itself (internal test).

Closes forgejo-mcp-broker-pur. The OAuth keystone is in place; phase 2c
unblocks discovery (2d) and security review (2e), and combined with the
existing supervisor + bridge it unblocks the session glue work in
phase 5.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ole-Morten Duesund 2026-04-27 17:04:34 +02:00
commit d16b18ea38
4 changed files with 1957 additions and 2 deletions

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{"id":"forgejo-mcp-broker-q4x","title":"Phase 5c: idle reaper + Forgejo token rotation + child respawn","description":"Reaper (30s tick) applies idle timeout. Rotation (1-min tick) refreshes Forgejo tokens expiring \u003c2min, SIGTERMs child, respawns on next request (design.md §6). Token revocation tears down sessions.","acceptance_criteria":"Clock-injected tests: idle kill, rotation triggers respawn, revocation tears down sessions. Smoke test: 20 concurrent sessions for 10min with mid-test rotations.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:18Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:18Z","dependencies":[{"issue_id":"forgejo-mcp-broker-q4x","depends_on_id":"forgejo-mcp-broker-pur","type":"blocks","created_at":"2026-04-24T17:45:31Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-q4x","depends_on_id":"forgejo-mcp-broker-t81","type":"blocks","created_at":"2026-04-24T17:45:31Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":2,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-ytw","title":"Phase 5b: bearer-token middleware on /mcp","description":"Middleware reads Authorization: Bearer \u003cmcp_token\u003e, resolves via store, attaches Forgejo access token to request context. 401 for missing/expired/revoked.","acceptance_criteria":"Table-driven tests: missing header, malformed, unknown token, expired, revoked, valid. Valid-token path puts Forgejo token on ctx via typed key.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:18Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:18Z","dependencies":[{"issue_id":"forgejo-mcp-broker-ytw","depends_on_id":"forgejo-mcp-broker-pur","type":"blocks","created_at":"2026-04-24T17:45:30Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-t81","title":"Phase 5a: session registry + spawn-on-initialize","description":"Map Mcp-Session-Id -\u003e supervisor.Child + user metadata. On first initialize for unknown sid, spawn forgejo-mcp with user's Forgejo token in env, bind to bridge. LastActive bumped per request.","acceptance_criteria":"Tests with fake supervisor + fake bridge cover: spawn-on-initialize, reuse for subsequent messages, unknown-sid returns 410, max-sessions cap enforced.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:17Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:17Z","dependencies":[{"issue_id":"forgejo-mcp-broker-t81","depends_on_id":"forgejo-mcp-broker-am1","type":"blocks","created_at":"2026-04-24T17:45:29Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-t81","depends_on_id":"forgejo-mcp-broker-pur","type":"blocks","created_at":"2026-04-24T17:45:30Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-t81","depends_on_id":"forgejo-mcp-broker-zuq","type":"blocks","created_at":"2026-04-24T17:45:28Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":3,"dependent_count":2,"comment_count":0}
{"id":"forgejo-mcp-broker-xot","title":"Phase 4b: bridge integration test against real forgejo-mcp","description":"Drive the bridge with initialize -\u003e tools/list -\u003e tools/call get_forgejo_mcp_server_version against a real forgejo-mcp subprocess. Validates the opaque-pipe assumption.","acceptance_criteria":"Full handshake, tools/list returns expected set, tools/call returns a version string. Tagged as integration test if runtime exceeds 2s.","status":"in_progress","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:16Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T14:10:04Z","started_at":"2026-04-27T14:10:04Z","dependencies":[{"issue_id":"forgejo-mcp-broker-xot","depends_on_id":"forgejo-mcp-broker-am1","type":"blocks","created_at":"2026-04-24T17:45:28Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":0,"comment_count":0}
{"id":"forgejo-mcp-broker-xot","title":"Phase 4b: bridge integration test against real forgejo-mcp","description":"Drive the bridge with initialize -\u003e tools/list -\u003e tools/call get_forgejo_mcp_server_version against a real forgejo-mcp subprocess. Validates the opaque-pipe assumption.","acceptance_criteria":"Full handshake, tools/list returns expected set, tools/call returns a version string. Tagged as integration test if runtime exceeds 2s.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:16Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T14:28:39Z","started_at":"2026-04-27T14:10:04Z","closed_at":"2026-04-27T14:28:39Z","close_reason":"Bridge integration test passes against real forgejo-mcp 2.2.0: MCP handshake (initialize → notifications/initialized → tools/list → tools/call) round-trips through bridge cleanly. Fake Forgejo covers /api/v1/version and /api/v1/user probes. Phase 4 complete.","dependencies":[{"issue_id":"forgejo-mcp-broker-xot","depends_on_id":"forgejo-mcp-broker-am1","type":"blocks","created_at":"2026-04-24T17:45:28Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":0,"comment_count":0}
{"id":"forgejo-mcp-broker-31t","title":"Phase 3b: supervisor stress tests (FD/goroutine/zombie leak detection)","description":"1000 spawn/stop cycles under -race. Verify no FD leak, no goroutine leak (go.uber.org/goleak), no zombies (wait4 returns ECHILD when idle).","acceptance_criteria":"Cycle test passes under -race. FD count stable within a small constant. goleak detects no extra goroutines after test.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:15Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T14:04:42Z","started_at":"2026-04-27T12:00:32Z","closed_at":"2026-04-27T14:04:42Z","close_reason":"Stress tests in place: 1000-cycle spawn/reap and 200-cycle Stop both clean under -race; FD/goroutine/zombie deltas all single-digit. Driver: /bin/true and /bin/cat (helper-process recursion at scale exposed an unrelated Go pidfd interaction). Supervisor now defensively closes pipe handles post-Wait.","dependencies":[{"issue_id":"forgejo-mcp-broker-31t","depends_on_id":"forgejo-mcp-broker-zuq","type":"blocks","created_at":"2026-04-24T17:45:26Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":0,"comment_count":0}
{"id":"forgejo-mcp-broker-am1","title":"Phase 4a: internal/bridge JSON-RPC pipe + SSE writer","description":"Given a supervisor.Child: inbound HTTP JSON -\u003e newline-framed stdin; stdout lines -\u003e SSE frames. Handle client disconnect without killing the child.","acceptance_criteria":"Unit tests with mock Child that echoes: request/response round trip, multiple concurrent requests with correct id routing, client disconnect mid-stream.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:15Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T11:59:35Z","started_at":"2026-04-27T11:56:15Z","closed_at":"2026-04-27T11:59:35Z","close_reason":"Bridge shipped: per-id routing, SSE responses for request/reply messages, 204 for notifications, structured 4xx/5xx for malformed input. Decoupled from supervisor (takes pipes directly) for clean testing via io.Pipe. 90.0% coverage.","dependencies":[{"issue_id":"forgejo-mcp-broker-am1","depends_on_id":"forgejo-mcp-broker-zuq","type":"blocks","created_at":"2026-04-24T17:45:27Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":2,"comment_count":0}
{"id":"forgejo-mcp-broker-wgo","title":"Phase 2e: OAuth security review + attack-path tests","description":"Phase 2 exit gate. Review every handler for classic OAuth vulns (open redirect, code replay, mix-up, token leak in logs, host spoofing). Add at least one test per attack class. Update design.md §8 with findings.","acceptance_criteria":"Review checklist documented. Tests added for: PKCE mismatch, stale code, token absent from log attributes, bad redirect_uri, mismatched state, replay of used code.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:14Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:14Z","dependencies":[{"issue_id":"forgejo-mcp-broker-wgo","depends_on_id":"forgejo-mcp-broker-b2o","type":"blocks","created_at":"2026-04-24T17:45:26Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-wgo","depends_on_id":"forgejo-mcp-broker-pur","type":"blocks","created_at":"2026-04-24T17:45:25Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":2,"dependent_count":0,"comment_count":0}
{"id":"forgejo-mcp-broker-zuq","title":"Phase 3a: internal/supervisor managed stdio subprocess","description":"Child type: Start, Stop(ctx) with SIGTERM -\u003e grace -\u003e SIGKILL, Wait+reap goroutine (no zombies), stderr drainer with prefix. Protocol-agnostic.","acceptance_criteria":"Unit tests against an echo-loop helper: round trip, graceful stop, kill-after-grace, child-exits-on-own detection, stderr capture. Manual spawn of real forgejo-mcp --transport stdio works.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:14Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T11:41:07Z","started_at":"2026-04-27T11:32:54Z","closed_at":"2026-04-27T11:41:07Z","close_reason":"internal/supervisor shipped: Start/Stop/Done/ExitErr/Pid, SIGTERM-\u003egrace-\u003eSIGKILL escalation, mandatory wait-and-reap. Test uses TestMain helper-process pattern; coverage 89.6% on the testable surface.","dependency_count":0,"dependent_count":3,"comment_count":0}
{"id":"forgejo-mcp-broker-b2o","title":"Phase 2d: OAuth discovery endpoints (/.well-known/*)","description":"GET /.well-known/oauth-protected-resource and /.well-known/oauth-authorization-server. Issuer URLs MUST derive from cfg.PublicURL, never inbound headers (host-header attack defense per design.md §8).","acceptance_criteria":"Responses validate against RFC 8414/9728 shapes. Issuer URL sourced from config only. supported_scopes matches cfg.ForgejoOAuthScopes.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:13Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:13Z","dependencies":[{"issue_id":"forgejo-mcp-broker-b2o","depends_on_id":"forgejo-mcp-broker-pur","type":"blocks","created_at":"2026-04-24T17:45:25Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-b9i","title":"Phase 2b: internal/forgejo OAuth client","description":"Broker-side OAuth client for upstream Forgejo: authorize URL builder, code-to-token exchange, refresh_token grant, userinfo fetch, revoke. Used by AS callback and refresh machinery. Stateless; caller owns persistence.","acceptance_criteria":"Unit tests with httptest.Server fake Forgejo cover each grant plus error paths (wrong code, expired refresh, revoked token). No state persisted in this package.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:12Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T11:31:27Z","started_at":"2026-04-27T11:29:17Z","closed_at":"2026-04-27T11:31:27Z","close_reason":"internal/forgejo shipped: AuthorizeURL, ExchangeCode, Refresh, FetchUserInfo. Structured *forgejo.Error for OAuth failures (errors.As-friendly). 95.1% coverage. Stateless — caller owns persistence. Revocation deferred since upstream Forgejo lacks the endpoint.","dependency_count":0,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-pur","title":"Phase 2c: internal/oauth AS endpoints (register, authorize, callback, token, revoke)","description":"Five OAuth handlers per design.md §4.1. RFC 7591 DCR with ephemeral client IDs, authorize -\u003e Forgejo delegation, callback minting broker auth codes, token exchange with SHA-256 hashing at rest, revoke. PKCE S256 required.","acceptance_criteria":"End-to-end curl walkthrough from plan.md phase 2 passes. All tokens hashed at rest. Auth codes single-use, 10-min TTL. Rejects missing PKCE, non-S256, wrong verifier, expired codes/tokens. Handler coverage \u003e=80%.","status":"open","priority":1,"issue_type":"task","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:12Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:45:12Z","dependencies":[{"issue_id":"forgejo-mcp-broker-pur","depends_on_id":"forgejo-mcp-broker-b9i","type":"blocks","created_at":"2026-04-24T17:45:24Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-pur","depends_on_id":"forgejo-mcp-broker-cpb","type":"blocks","created_at":"2026-04-24T17:45:24Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":2,"dependent_count":5,"comment_count":0}
{"id":"forgejo-mcp-broker-pur","title":"Phase 2c: internal/oauth AS endpoints (register, authorize, callback, token, revoke)","description":"Five OAuth handlers per design.md §4.1. RFC 7591 DCR with ephemeral client IDs, authorize -\u003e Forgejo delegation, callback minting broker auth codes, token exchange with SHA-256 hashing at rest, revoke. PKCE S256 required.","acceptance_criteria":"End-to-end curl walkthrough from plan.md phase 2 passes. All tokens hashed at rest. Auth codes single-use, 10-min TTL. Rejects missing PKCE, non-S256, wrong verifier, expired codes/tokens. Handler coverage \u003e=80%.","status":"in_progress","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:12Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T14:30:02Z","started_at":"2026-04-27T14:30:02Z","dependencies":[{"issue_id":"forgejo-mcp-broker-pur","depends_on_id":"forgejo-mcp-broker-b9i","type":"blocks","created_at":"2026-04-24T17:45:24Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-pur","depends_on_id":"forgejo-mcp-broker-cpb","type":"blocks","created_at":"2026-04-24T17:45:24Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":2,"dependent_count":5,"comment_count":0}
{"id":"forgejo-mcp-broker-cpb","title":"Phase 2a: OAuth tables migration","description":"Add migrations/0002_oauth_tables.sql creating clients, auth_codes, access_tokens, refresh_tokens per design.md §4.2. Broker tokens stored as SHA-256 hashes; Forgejo tokens cleartext (subprocess spawning requires them). See plan.md phase 2.","acceptance_criteria":"Migration applies on a fresh DB and is idempotent on reopen. Schema matches design.md §4.2. Tests verify every table and key column exists.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:04Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T11:28:20Z","started_at":"2026-04-27T11:26:17Z","closed_at":"2026-04-27T11:28:20Z","close_reason":"0002_oauth_tables.sql shipped: clients/auth_codes/access_tokens/refresh_tokens with cascading FKs, indexes on hot-path columns, and an oauth_schema_version marker. PRAGMA-driven tests verify columns; FK cascade tested in both directions.","dependency_count":0,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-8ei","title":"Phase 1: internal/httpserver with /healthz and graceful shutdown","description":"Implement internal/httpserver: constructs a *http.Server bound to cfg.Listen, mounts GET /healthz (returns 200 with JSON build-info from the build-info package, including version, git revision, build date, and current store status), handles SIGTERM/SIGINT by initiating graceful shutdown with a configurable deadline (default 10s). Uses log/slog for structured JSON logs. Exposes a Run(ctx) error method that blocks until shutdown completes.","acceptance_criteria":"go test ./internal/httpserver passes; GET /healthz returns expected JSON; sending SIGTERM causes Run to return nil within 2 seconds after in-flight requests complete; slow in-flight request is allowed to finish within the deadline, then forcibly closed.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T14:46:20Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:26:43Z","started_at":"2026-04-24T15:24:09Z","closed_at":"2026-04-24T15:26:43Z","close_reason":"httpserver shipped: /healthz with store probe, graceful shutdown with force-close fallback, ExtraHandler extension point. 97.9% coverage. internal/log also implemented in the same commit (100% coverage).","dependencies":[{"issue_id":"forgejo-mcp-broker-8ei","depends_on_id":"forgejo-mcp-broker-n84","type":"blocks","created_at":"2026-04-24T16:46:19Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":1,"dependent_count":1,"comment_count":0}
{"id":"forgejo-mcp-broker-t37","title":"Phase 1: wire cmd/broker/main.go and integration test","description":"Final phase 1 task: wire config → log → store → httpserver in cmd/broker/main.go. Parse config, init slog, open store, start httpserver, wait for shutdown signal, close store, exit. Add an integration test under cmd/broker/ that builds the binary, runs it with a valid env + temp store path, curls /healthz, sends SIGTERM, verifies clean exit within 2s. This is the acceptance gate for phase 1.","acceptance_criteria":"make build; make test (incl. integration) pass; running the binary with missing config fails with a clear error; running with valid config serves /healthz; SIGTERM shuts down cleanly within 2s; /healthz JSON includes version, git revision, build date, and store OK status.","status":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T14:46:20Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-24T15:29:44Z","started_at":"2026-04-24T15:27:58Z","closed_at":"2026-04-24T15:29:44Z","close_reason":"Main wired, signal.NotifyContext triggers shutdown cascade, integration tests green. Phase 1 complete: binary starts with valid config, serves /healthz JSON, shuts down cleanly on SIGTERM within 2s.","dependencies":[{"issue_id":"forgejo-mcp-broker-t37","depends_on_id":"forgejo-mcp-broker-8ei","type":"blocks","created_at":"2026-04-24T16:48:29Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-t37","depends_on_id":"forgejo-mcp-broker-9jh","type":"blocks","created_at":"2026-04-24T16:48:29Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-t37","depends_on_id":"forgejo-mcp-broker-9nq","type":"blocks","created_at":"2026-04-24T16:48:28Z","created_by":"Ole-Morten Duesund","metadata":"{}"},{"issue_id":"forgejo-mcp-broker-t37","depends_on_id":"forgejo-mcp-broker-n84","type":"blocks","created_at":"2026-04-24T16:48:28Z","created_by":"Ole-Morten Duesund","metadata":"{}"}],"dependency_count":4,"dependent_count":0,"comment_count":0}