feat(auth): fall back to GITEA_MCP_DEFAULT_TOKEN when no Bearer header

claude.ai connectors call the server with no Authorization header (confirmed
via request logging). Add a configurable default Gitea PAT so unauthenticated
clients (like claude.ai) can still reach the server.

Claude Code continues to pass per-request PATs; defaultToken="" preserves
the existing strict behaviour when the env var is unset.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/gitea-mcp/main.go

@@ -73,7 +73,7 @@ func main() {
 
 	mux := http.NewServeMux()
 	mux.Handle("/mcp", logReq(mcp.OriginAllowlist(cfg.OriginAllowlist)(
-		auth.BearerMiddleware(cfg.GiteaBaseURL,
+		auth.BearerMiddleware(cfg.GiteaBaseURL, cfg.DefaultToken,
 			auth.CallerMiddleware(mcpSrv),
 		)),
 	))

internal/auth/bearer.go

@@ -12,14 +12,20 @@ type tokenKey struct{}
 // BearerMiddleware validates the incoming bearer token as a Gitea PAT by
 // calling GET /api/v1/user. The validated token is stored in context for
 // downstream use by the Gitea client.
-func BearerMiddleware(giteaBaseURL string, next http.Handler) http.Handler {
+//
+// defaultToken, if non-empty, is used when no Authorization header is present
+// (e.g. claude.ai connectors which do not inject Bearer tokens).
+func BearerMiddleware(giteaBaseURL, defaultToken string, next http.Handler) http.Handler {
 	hc := &http.Client{Timeout: 5 * time.Second}
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		token, ok := strings.CutPrefix(r.Header.Get("Authorization"), "Bearer ")
 		if !ok || token == "" {
+			if defaultToken == "" {
 				http.Error(w, "unauthorized", http.StatusUnauthorized)
 				return
 			}
+			token = defaultToken
+		}
 		req, err := http.NewRequestWithContext(r.Context(), http.MethodGet, giteaBaseURL+"/api/v1/user", nil)
 		if err != nil {
 			http.Error(w, "unauthorized", http.StatusUnauthorized)

internal/auth/bearer_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestBearerMiddleware_NoAuthHeader(t *testing.T) {
-	srv := httptest.NewServer(auth.BearerMiddleware("https://gitea.example.com",
+	srv := httptest.NewServer(auth.BearerMiddleware("https://gitea.example.com", "",
 		http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 			w.WriteHeader(http.StatusOK)
 		}),
@@ -24,6 +24,32 @@ func TestBearerMiddleware_NoAuthHeader(t *testing.T) {
 	assert.Equal(t, http.StatusUnauthorized, resp.StatusCode)
 }
 
+func TestBearerMiddleware_NoAuthHeaderWithDefault(t *testing.T) {
+	const defaultToken = "default-pat"
+
+	giteaMock := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "token "+defaultToken, r.Header.Get("Authorization"))
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer giteaMock.Close()
+
+	called := false
+	srv := httptest.NewServer(auth.BearerMiddleware(giteaMock.URL, defaultToken,
+		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			called = true
+			assert.Equal(t, defaultToken, auth.TokenFromContext(r.Context()))
+			w.WriteHeader(http.StatusOK)
+		}),
+	))
+	defer srv.Close()
+
+	resp, err := http.Post(srv.URL+"/mcp", "application/json", nil)
+	require.NoError(t, err)
+	defer func() { _ = resp.Body.Close() }()
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	assert.True(t, called)
+}
+
 func TestBearerMiddleware_InvalidToken(t *testing.T) {
 	// Mock Gitea that rejects the token
 	giteaMock := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -31,7 +57,7 @@ func TestBearerMiddleware_InvalidToken(t *testing.T) {
 	}))
 	defer giteaMock.Close()
 
-	srv := httptest.NewServer(auth.BearerMiddleware(giteaMock.URL,
+	srv := httptest.NewServer(auth.BearerMiddleware(giteaMock.URL, "",
 		http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 			w.WriteHeader(http.StatusOK)
 		}),
@@ -57,7 +83,7 @@ func TestBearerMiddleware_ValidToken(t *testing.T) {
 	defer giteaMock.Close()
 
 	called := false
-	srv := httptest.NewServer(auth.BearerMiddleware(giteaMock.URL,
+	srv := httptest.NewServer(auth.BearerMiddleware(giteaMock.URL, "",
 		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			called = true
 			// Token must be available in context for downstream Gitea client

internal/config/config.go

@@ -8,6 +8,7 @@ import (
 type Config struct {
 	Port            string   // GITEA_MCP_PORT, default 8080
 	GiteaBaseURL    string   // GITEA_BASE_URL, e.g. https://gitea.d-ma.be
+	DefaultToken    string   // GITEA_MCP_DEFAULT_TOKEN, fallback PAT when no Bearer header present (e.g. claude.ai)
 	AllowedOwners   []string // GITEA_MCP_ALLOWED_OWNERS, comma-separated, default "mathias"
 	OriginAllowlist []string // GITEA_MCP_ORIGIN_ALLOWLIST, comma-separated
 }
@@ -16,6 +17,7 @@ func Load() (Config, error) {
 	cfg := Config{
 		Port:            envOr("GITEA_MCP_PORT", "8080"),
 		GiteaBaseURL:    os.Getenv("GITEA_BASE_URL"),
+		DefaultToken:    os.Getenv("GITEA_MCP_DEFAULT_TOKEN"),
 		AllowedOwners:   splitCSV(envOr("GITEA_MCP_ALLOWED_OWNERS", "mathias")),
 		OriginAllowlist: splitCSV(os.Getenv("GITEA_MCP_ORIGIN_ALLOWLIST")),
 	}