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feat(oauth): /.well-known discovery endpoints (forgejo-mcp-broker-b2o)

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Adds RFC 8414 (oauth-authorization-server) and RFC 9728 (oauth-
protected-resource) metadata documents.

Both URLs are derived from cfg.Issuer at construction time, never from
inbound request headers. Test TestDiscovery_IssuerIgnoresHostHeader
explicitly probes this — a malicious Host: evil.example.com value must
not leak into the published metadata. Defense against the OAuth
metadata-spoofing class starts at the discovery layer.

Capabilities published reflect the actual OAuth surface:
  - response_types_supported = ["code"]
  - grant_types_supported = ["authorization_code", "refresh_token"]
  - code_challenge_methods_supported = ["S256"]   (PKCE only, no plain)
  - token_endpoint_auth_methods_supported = ["none"]   (PKCE-only public clients)

Protected-resource metadata advertises /mcp as the resource; phase 5
will mount the gated MCP endpoint there.

Closes forgejo-mcp-broker-b2o.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Ole-Morten Duesund 2026-04-27 17:08:12 +02:00
commit fee12a2ac0
3 changed files with 187 additions and 8 deletions
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@ -6,9 +6,9 @@
{"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-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-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":"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-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}
{"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}