Prevent loops for proxied requests on unknown endpoints (#166)

Follow-up for https://github.com/gesellix/Bose-SoundTouch/issues/161

pkg/service/handlers/handlers_proxy.go

@@ -15,6 +15,13 @@ import (
 
 // HandleProxyRequest handles requests to the logging proxy.
 func (s *Server) HandleProxyRequest(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("X-Bose-Proxy-Hop") != "" {
+		log.Printf("[PROXY_LOOP] Loop detected for %s %s, breaking loop", r.Method, r.URL.Path)
+		http.Error(w, "Loop detected", http.StatusNotFound)
+
+		return
+	}
+
 	targetURLStr := strings.TrimPrefix(r.URL.Path, "/proxy/")
 	if targetURLStr == "" {
 		http.Error(w, "Target URL is required", http.StatusBadRequest)
@@ -65,6 +72,8 @@ func (s *Server) ServeProxy(target *url.URL) http.HandlerFunc {
 					pr.Out.URL.Path = target.Path
 				}
 
+				pr.Out.Header.Set("X-Bose-Proxy-Hop", "1")
+
 				lp.LogRequest(pr.Out)
 			},
 			Transport: &http.Transport{
@@ -101,6 +110,13 @@ func (s *Server) HandleNotFound(w http.ResponseWriter, r *http.Request) {
 
 // HandleBoseProxy proxies the request to the Bose upstream.
 func (s *Server) HandleBoseProxy(w http.ResponseWriter, r *http.Request) {
+	if r.Header.Get("X-Bose-Proxy-Hop") != "" {
+		log.Printf("[PROXY_LOOP] Loop detected for %s %s, breaking loop", r.Method, r.URL.Path)
+		http.Error(w, "Loop detected", http.StatusNotFound)
+
+		return
+	}
+
 	host := r.Host
 	if host == "" {
 		host = "streaming.bose.com"

pkg/service/handlers/loop_prevention_test.go

@@ -0,0 +1,53 @@
+package handlers
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/gesellix/bose-soundtouch/pkg/service/datastore"
+)
+
+func TestHandleBoseProxy_LoopPrevention(t *testing.T) {
+	tmpDir, err := os.MkdirTemp("", "proxy-loop-test")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	ds := datastore.NewDataStore(filepath.Join(tmpDir, "test.db"))
+	server := NewServer(ds, nil, "http://localhost", false, false, false)
+
+	t.Run("first hop should be allowed", func(t *testing.T) {
+		req := httptest.NewRequest("GET", "/unknown-endpoint", nil)
+		req.Host = "localhost"
+		w := httptest.NewRecorder()
+		server.HandleBoseProxy(w, req)
+		if w.Code == http.StatusNotFound {
+			t.Errorf("Expected first hop to be allowed (even if it fails later), but got 404")
+		}
+	})
+
+	t.Run("second hop should be blocked", func(t *testing.T) {
+		req := httptest.NewRequest("GET", "/unknown-endpoint", nil)
+		req.Host = "localhost"
+		req.Header.Set("X-Bose-Proxy-Hop", "1")
+		w := httptest.NewRecorder()
+		server.HandleBoseProxy(w, req)
+		if w.Code != http.StatusNotFound {
+			t.Errorf("Expected second hop to be blocked with 404, but got %d", w.Code)
+		}
+	})
+
+	t.Run("HandleProxyRequest loop detection", func(t *testing.T) {
+		req := httptest.NewRequest("GET", "/proxy/http://example.com", nil)
+		req.Header.Set("X-Bose-Proxy-Hop", "1")
+		w := httptest.NewRecorder()
+		server.HandleProxyRequest(w, req)
+		if w.Code != http.StatusNotFound {
+			t.Errorf("Expected HandleProxyRequest loop to be blocked with 404, but got %d", w.Code)
+		}
+	})
+}