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feat(oauth): bearer-token middleware (forgejo-mcp-broker-ytw)

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Adds Authenticator.RequireBearer — http middleware that gates downstream
handlers on a valid broker access token.

Lookup path:
  1. Read Authorization: Bearer <token> header.
  2. SHA-256 the token, query access_tokens by token_hash.
  3. Reject expired or revoked rows.
  4. Build a Session (client_id, forgejo user info, upstream token,
     scopes) and attach to r.Context() under a typed key.

Downstream handlers (the MCP endpoint shipping in 5a) read the
upstream Forgejo token via SessionFromContext to spawn forgejo-mcp
subprocesses scoped to the right user.

Failures emit 401 with an RFC 6750 §3 WWW-Authenticate header carrying
distinct error codes (invalid_request for missing/malformed headers,
invalid_token with reason=expired/revoked/unknown for token problems).
The body stays empty so a confused browser doesn't render auth errors;
all detail rides in the header where compliant clients look for it.

Tests: 90.9% on RequireBearer, 91.7% on lookupSession. Covers valid
token, missing/wrong-scheme/empty Authorization, unknown token,
expired token (clock-advanced past AccessTokenTTL), revoked token (via
the public /oauth/revoke endpoint).

Closes forgejo-mcp-broker-ytw.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ole-Morten Duesund 2026-04-27 17:10:21 +02:00
commit 9c8cf40501
3 changed files with 375 additions and 2 deletions
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@ -1,12 +1,12 @@
{"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-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":"in_progress","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:18Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T15:08:52Z","started_at":"2026-04-27T15:08:52Z","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":"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":"in_progress","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:13Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T15:06:24Z","started_at":"2026-04-27T15:06:24Z","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-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":"closed","priority":1,"issue_type":"task","assignee":"Ole-Morten Duesund","owner":"olemd@glemt.net","created_at":"2026-04-24T15:45:13Z","created_by":"Ole-Morten Duesund","updated_at":"2026-04-27T15:08:19Z","started_at":"2026-04-27T15:06:24Z","closed_at":"2026-04-27T15:08:19Z","close_reason":"Discovery endpoints shipped: /.well-known/oauth-authorization-server (RFC 8414) and /.well-known/oauth-protected-resource (RFC 9728). All URLs derived from cfg.Issuer; explicit Host-header-spoofing test verifies attacker-supplied hosts don't leak into metadata.","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":"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":"2026-04-27T15:04:43Z","started_at":"2026-04-27T14:30:02Z","closed_at":"2026-04-27T15:04:43Z","close_reason":"OAuth AS shipped: register, authorize, callback, token (auth_code + refresh grants), revoke. PKCE S256 enforced. Tokens hashed at rest. Refresh rotation with old-token revocation. Auth-code single-use via atomic UPDATE rows-affected. 81% coverage. ~1700 LOC. Unblocks 2d, 2e, and is a key dep for 5a.","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}