fix: validate UUIDs in OPDS middleware before authentication

- Add UUID validation in device_auth middleware for OPDS routes
- Return 400 Bad Request for invalid device/book IDs instead of 401
- Remove redundant UUID validation from OPDS handlers (middleware handles it)

internal/handlers/opds.go

@@ -54,6 +54,7 @@ func (h *OPDSHandler) getBaseURLs(c echo.Context) (string, string, error) {
 // GetDeviceCatalog returns the OPDS catalog feed for a device
 func (h *OPDSHandler) GetDeviceCatalog(c echo.Context) error {
 	deviceID := c.Param("deviceId")
+
 	page := c.QueryParam("page")
 	perPage := c.QueryParam("per_page")
 	includeFormat := c.QueryParam("include_format")
@@ -217,6 +218,7 @@ func (h *OPDSHandler) GetDeviceCatalog(c echo.Context) error {
 // SearchDeviceCatalog searches the OPDS catalog for a device
 func (h *OPDSHandler) SearchDeviceCatalog(c echo.Context) error {
 	deviceID := c.Param("deviceId")
+
 	query := c.QueryParam("q")
 
 	if query == "" {
@@ -341,16 +343,9 @@ func (h *OPDSHandler) DownloadBook(c echo.Context) error {
 		format = "epub"
 	}
 
-	// Parse IDs
+	// Parse IDs (middleware guarantees valid UUIDs)
-	deviceUUID, err := uuid.Parse(deviceID)
+	deviceUUID, _ := uuid.Parse(deviceID)
-	if err != nil {
+	bookUUID, _ := uuid.Parse(bookID)
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid device id"})
-	}
-
-	bookUUID, err := uuid.Parse(bookID)
-	if err != nil {
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid book id"})
-	}
 
 	// Verify device exists
 	device, err := h.db.GetDevice(c.Request().Context(), pgtype.UUID{Bytes: deviceUUID, Valid: true})
@@ -484,16 +479,9 @@ func (h *OPDSHandler) GetCoverImage(c echo.Context) error {
 	deviceID := c.Param("deviceId")
 	bookID := c.Param("bookId")
 
-	// Parse IDs
+	// Parse IDs (middleware guarantees valid UUIDs)
-	deviceUUID, err := uuid.Parse(deviceID)
+	deviceUUID, _ := uuid.Parse(deviceID)
-	if err != nil {
+	bookUUID, _ := uuid.Parse(bookID)
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid device id"})
-	}
-
-	bookUUID, err := uuid.Parse(bookID)
-	if err != nil {
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid book id"})
-	}
 
 	// Verify device exists
 	device, err := h.db.GetDevice(c.Request().Context(), pgtype.UUID{Bytes: deviceUUID, Valid: true})
@@ -580,11 +568,8 @@ func (h *OPDSHandler) GetDeviceNavigation(c echo.Context) error {
 		return c.XML(http.StatusInternalServerError, opds.NewErrorFeed("Failed to get config"))
 	}
 
-	// Parse device ID
+	// Parse device ID (middleware guarantees valid UUID)
-	deviceUUID, err := uuid.Parse(deviceID)
+	deviceUUID, _ := uuid.Parse(deviceID)
-	if err != nil {
-		return c.XML(http.StatusBadRequest, opds.NewErrorFeed("Invalid device ID"))
-	}
 
 	// Verify device exists
 	_, err = h.db.GetDevice(c.Request().Context(), pgtype.UUID{Bytes: deviceUUID, Valid: true})
@@ -629,16 +614,9 @@ func (h *OPDSHandler) ListFormats(c echo.Context) error {
 	deviceID := c.Param("deviceId")
 	bookID := c.Param("bookId")
 
-	// Parse IDs
+	// Parse IDs (middleware guarantees valid UUIDs)
-	deviceUUID, err := uuid.Parse(deviceID)
+	deviceUUID, _ := uuid.Parse(deviceID)
-	if err != nil {
+	bookUUID, _ := uuid.Parse(bookID)
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid device id"})
-	}
-
-	bookUUID, err := uuid.Parse(bookID)
-	if err != nil {
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid book id"})
-	}
 
 	// Verify device exists
 	device, err := h.db.GetDevice(c.Request().Context(), pgtype.UUID{Bytes: deviceUUID, Valid: true})

internal/middleware/device_auth.go

@@ -42,6 +42,24 @@ func (m *DeviceAuthMiddleware) Authenticate(next echo.HandlerFunc) echo.HandlerF
 		var urlToken string
 		var queryToken string
 
+		// For OPDS routes, validate deviceId is a valid UUID before authentication
+		// This allows returning 400 Bad Request for invalid UUIDs instead of 401
+		if strings.HasPrefix(c.Request().URL.Path, "/opds/devices/") {
+			deviceID := c.Param("deviceId")
+			if deviceID != "" {
+				if _, err := uuid.Parse(deviceID); err != nil {
+					return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid device ID"})
+				}
+			}
+			// Also validate bookId for download, cover, and formats endpoints
+			bookID := c.Param("bookId")
+			if bookID != "" {
+				if _, err := uuid.Parse(bookID); err != nil {
+					return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid book ID"})
+				}
+			}
+		}
+
 		// Method 1: Try Bearer token header (KOReader, API clients, OPDS)
 		authHeader := c.Request().Header.Get("Authorization")
 		if authHeader != "" {