Restore _pinfo.masked to a boolean state (0 or 1) to keep backward compatibility.

Author: mathieucarbou

src/AsyncWebSocket.cpp

@@ -515,6 +515,7 @@ void AsyncWebSocketClient::_onData(void *pbuf, size_t plen) {
       _pinfo.index = 0;
       _pinfo.final = (fdata[0] & 0x80) != 0;
       _pinfo.opcode = fdata[0] & 0x0F;
+      // _pinfo.masked is a boolean: 1 if the frame is masked, 0 otherwise. Do not use as a counter.
       _pinfo.masked = ((fdata[1] & 0x80) != 0) ? 1 : 0;
       _pinfo.len = fdata[1] & 0x7F;
 
@@ -539,17 +540,26 @@ void AsyncWebSocketClient::_onData(void *pbuf, size_t plen) {
     }
 
     if (_pinfo.masked > 0 && _pinfo.masked < 5) {
-      // Handle fragmented mask data - Safari may split the 4-byte mask across multiple packets
-      while (_pinfo.masked < 5) {
-        if (plen == 0) {
-          //wait for more data
-          _pstate = 1;
-          return;
+      // Handle Safari edge case: close frame with plen 0, mask bit set, but no mask bytes
+      if (_pinfo.len == 0 && plen == 0) {
+        // Malformed frame (Safari bug): treat as unmasked for compatibility
+        _pinfo.masked = 0;
+      } else {
+        // Handle fragmented mask data - Safari may split the 4-byte mask across multiple packets
+        int mask_bytes_read = _pinfo.masked - 1;
+        while (mask_bytes_read < 4) {
+          if (plen == 0) {
+            // wait for more data
+            _pinfo.masked = mask_bytes_read + 1;
+            _pstate = 1;
+            return;
+          }
+          _pinfo.mask[mask_bytes_read] = data[0];
+          data += 1;
+          plen -= 1;
+          mask_bytes_read++;
         }
-        _pinfo.mask[_pinfo.masked - 1] = data[0];
-        data += 1;
-        plen -= 1;
-        _pinfo.masked++;
+        _pinfo.masked = 1;  // restore boolean semantics: mask fully read
       }
     }