Never emit 0 as close code; use 1005 instead

src/WebSocket.h

@@ -124,8 +124,9 @@ public:
         return true;
     }
 
-    /* Send websocket close frame, emit close event, send FIN if successful */
-    void end(int code, std::string_view message = {}) {
+    /* Send websocket close frame, emit close event, send FIN if successful.
+     * Will not append a close reason if code is 0 or 1005. */
+    void end(int code = 0, std::string_view message = {}) {
         /* Check if we already called this one */
         WebSocketData *webSocketData = (WebSocketData *) us_socket_ext(SSL, (us_socket_t *) this);
         if (webSocketData->isShuttingDown) {

src/WebSocketProtocol.h

@@ -151,20 +151,23 @@ struct CloseFrame {
 };
 
 static inline CloseFrame parseClosePayload(char *src, size_t length) {
-    CloseFrame cf = {};
+    /* If we get no code or message, default to reporting 1005 no status code present */
+    CloseFrame cf = {1005};
     if (length >= 2) {
         memcpy(&cf.code, src, 2);
         cf = {cond_byte_swap<uint16_t>(cf.code), src + 2, length - 2};
         if (cf.code < 1000 || cf.code > 4999 || (cf.code > 1011 && cf.code < 4000) ||
             (cf.code >= 1004 && cf.code <= 1006) || !isValidUtf8((unsigned char *) cf.message, cf.length)) {
-            return {};
+            /* Even though we got a WebSocket close frame, it in itself is abnormal */
+            return {1006};
         }
     }
     return cf;
 }
 
 static inline size_t formatClosePayload(char *dst, uint16_t code, const char *message, size_t length) {
-    if (code) {
+    /* We could have more strict checks here, but never append code 0 or 1005 or 1006 */
+    if (code && code != 1005 && code != 1006) {
         code = cond_byte_swap<uint16_t>(code);
         memcpy(dst, &code, 2);
         /* It is invalid to pass nullptr to memcpy, even though length is 0 */