feat(ingestion): add bearer token auth middleware for MCP endpoint

ingestion/cmd/server/main.go

@@ -57,6 +57,12 @@ func main() {
 
 	mcpSrv := mcp.NewServer(brainDir, &pipelineCfg, llmClient.Complete)
 
+	mcpToken := os.Getenv("BRAIN_MCP_TOKEN")
+	if mcpToken == "" {
+		logger.Error("BRAIN_MCP_TOKEN not set")
+		os.Exit(1)
+	}
+
 	ctx := context.Background()
 	if watchInterval > 0 {
 		watcher.Start(ctx, watcher.Config{
@@ -74,7 +80,7 @@ func main() {
 	mux.HandleFunc("POST /ingest-raw", h.IngestRaw)
 	mux.HandleFunc("POST /backfill-refs", h.BackfillRefs)
 	mux.HandleFunc("GET /pass-rate", h.PassRate)
-	mux.Handle("POST /mcp", mcpSrv)
+	mux.Handle("POST /mcp", mcp.BearerAuth(mcpToken, mcpSrv))
 
 	addr := ":" + port
 	watchIntervalLog := "disabled"

ingestion/internal/mcp/auth.go

@@ -0,0 +1,23 @@
+package mcp
+
+import (
+	"net/http"
+	"strings"
+)
+
+// BearerAuth returns a middleware that enforces a static bearer token on every
+// request. token must be non-empty; if it is empty, every request is rejected.
+func BearerAuth(token string, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if token == "" {
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		got := strings.TrimPrefix(r.Header.Get("Authorization"), "Bearer ")
+		if got != token {
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}

ingestion/internal/mcp/auth_test.go

@@ -0,0 +1,56 @@
+package mcp_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/mcp"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBearerAuth_MissingHeader(t *testing.T) {
+	handler := mcp.BearerAuth("secret", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	req := httptest.NewRequest(http.MethodPost, "/mcp", nil)
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	assert.Equal(t, http.StatusUnauthorized, rr.Code)
+}
+
+func TestBearerAuth_WrongToken(t *testing.T) {
+	handler := mcp.BearerAuth("secret", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	req := httptest.NewRequest(http.MethodPost, "/mcp", nil)
+	req.Header.Set("Authorization", "Bearer wrong")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	assert.Equal(t, http.StatusUnauthorized, rr.Code)
+}
+
+func TestBearerAuth_CorrectToken(t *testing.T) {
+	called := false
+	handler := mcp.BearerAuth("secret", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		called = true
+		w.WriteHeader(http.StatusOK)
+	}))
+	req := httptest.NewRequest(http.MethodPost, "/mcp", nil)
+	req.Header.Set("Authorization", "Bearer secret")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	assert.Equal(t, http.StatusOK, rr.Code)
+	assert.True(t, called)
+}
+
+func TestBearerAuth_EmptyConfiguredToken(t *testing.T) {
+	// Server started without a token configured — every request must fail.
+	handler := mcp.BearerAuth("", http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	req := httptest.NewRequest(http.MethodPost, "/mcp", nil)
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	assert.Equal(t, http.StatusUnauthorized, rr.Code)
+}