fix issues caused by websocket frame fragmentation

CHANGES.rst

@@ -11,7 +11,7 @@ Changes
 
 -
 
--
+- Fix websocket issues caused by frame fragmentation. #1962
 
 -
 

CONTRIBUTORS.txt

@@ -91,6 +91,7 @@ Joongi Kim
 Josep Cugat
 Julia Tsemusheva
 Julien Duponchelle
+Jungkook Park
 Junjie Tao
 Justas Trimailovas
 Justin Turner Arthur

aiohttp/http_websocket.py

@@ -224,17 +224,17 @@ def _feed_data(self, data):
                     WSMessage(WSMsgType.PONG, payload, ''), len(payload))
 
             elif opcode not in (
-                    WSMsgType.TEXT, WSMsgType.BINARY) and not self._opcode:
+                    WSMsgType.TEXT, WSMsgType.BINARY) and self._opcode is None:
                 raise WebSocketError(
                     WSCloseCode.PROTOCOL_ERROR,
                     "Unexpected opcode={!r}".format(opcode))
             else:
                 # load text/binary
-
                 if not fin:
                     # got partial frame payload
                     if opcode != WSMsgType.CONTINUATION:
                         self._opcode = opcode
+
                     self._partial.append(payload)
                 else:
                     # previous frame was non finished
@@ -248,39 +248,37 @@ def _feed_data(self, data):
 
                     if opcode == WSMsgType.CONTINUATION:
                         opcode = self._opcode
+                        self._opcode = None
 
-                    self._partial.append(payload)
+                    payload_merged = b''.join(self._partial) + payload
+                    self._partial.clear()
 
                     if opcode == WSMsgType.TEXT:
                         try:
-                            text = b''.join(self._partial).decode('utf-8')
+                            text = payload_merged.decode('utf-8')
                             self.queue.feed_data(
                                 WSMessage(WSMsgType.TEXT, text, ''), len(text))
                         except UnicodeDecodeError as exc:
                             raise WebSocketError(
                                 WSCloseCode.INVALID_TEXT,
                                 'Invalid UTF-8 text message') from exc
                     else:
-                        data = b''.join(self._partial)
                         self.queue.feed_data(
-                            WSMessage(WSMsgType.BINARY, data, ''), len(data))
-
-                    self._start_opcode = None
-                    self._partial.clear()
+                            WSMessage(WSMsgType.BINARY, payload_merged, ''),
+                            len(payload_merged))
 
         return False, b''
 
-    def parse_frame(self, buf, continuation=False, EMPTY=b''):
+    def parse_frame(self, buf):
         """Return the next frame from the socket."""
         frames = []
         if self._tail:
-            buf, self._tail = self._tail + buf, EMPTY
+            buf, self._tail = self._tail + buf, b''
 
         start_pos = 0
         buf_length = len(buf)
 
         while True:
-
             # read header
             if self._state == WSParserState.READ_HEADER:
                 if buf_length - start_pos >= 2:
@@ -312,15 +310,6 @@ def parse_frame(self, buf, continuation=False, EMPTY=b''):
                             WSCloseCode.PROTOCOL_ERROR,
                             'Received fragmented control frame')
 
-                    continuation = not self._frame_fin
-                    if (fin == 0 and
-                            opcode == WSMsgType.CONTINUATION and
-                            not continuation):
-                        raise WebSocketError(
-                            WSCloseCode.PROTOCOL_ERROR,
-                            'Received new fragment frame with non-zero '
-                            'opcode {!r}'.format(opcode))
-
                     has_mask = (second_byte >> 7) & 1
                     length = (second_byte) & 0x7f
 
@@ -409,6 +398,8 @@ def parse_frame(self, buf, continuation=False, EMPTY=b''):
                 else:
                     break
 
+        self._tail = buf[start_pos:]
+
         return frames
 
 

tests/test_websocket_parser.py

@@ -12,23 +12,28 @@
                                     _websocket_mask)
 
 
-def build_frame(message, opcode, use_mask=False, noheader=False):
+def build_frame(message, opcode, use_mask=False, noheader=False, is_fin=True):
     """Send a frame over the websocket with message as its payload."""
     msg_length = len(message)
     if use_mask:  # pragma: no cover
         mask_bit = 0x80
     else:
         mask_bit = 0
 
+    if is_fin:
+        header_first_byte = 0x80 | opcode
+    else:
+        header_first_byte = opcode
+
     if msg_length < 126:
         header = PACK_LEN1(
-            0x80 | opcode, msg_length | mask_bit)
+            header_first_byte, msg_length | mask_bit)
     elif msg_length < (1 << 16):  # pragma: no cover
         header = PACK_LEN2(
-            0x80 | opcode, 126 | mask_bit, msg_length)
+            header_first_byte, 126 | mask_bit, msg_length)
     else:
         header = PACK_LEN3(
-            0x80 | opcode, 127 | mask_bit, msg_length)
+            header_first_byte, 127 | mask_bit, msg_length)
 
     if use_mask:  # pragma: no cover
         mask = random.randrange(0, 0xffffffff)
@@ -117,13 +122,6 @@ def test_parse_frame_header_control_frame(out, parser):
         raise out.exception()
 
 
-def test_parse_frame_header_continuation(out, parser):
-    with pytest.raises(WebSocketError):
-        parser._frame_fin = True
-        parser.parse_frame(struct.pack('!BB', 0b00000000, 0b00000000))
-        raise out.exception()
-
-
 def _test_parse_frame_header_new_data_err(out, parser):
     with pytest.raises(WebSocketError):
         parser.parse_frame(struct.pack('!BB', 0b000000000, 0b00000000))
@@ -234,13 +232,21 @@ def test_simple_binary(out, parser):
     assert res == ((WSMsgType.BINARY, b'binary', ''), 6)
 
 
+def test_fragmentation_header(out, parser):
+    data = build_frame(b'a', WSMsgType.TEXT)
+    parser._feed_data(data[:1])
+    parser._feed_data(data[1:])
+
+    res = out._buffer[0]
+    assert res == (WSMessage(WSMsgType.TEXT, 'a', ''), 1)
+
+
 def test_continuation(out, parser):
-    parser.parse_frame = mock.Mock()
-    parser.parse_frame.return_value = [
-        (0, WSMsgType.TEXT, b'line1'),
-        (1, WSMsgType.CONTINUATION, b'line2')]
+    data1 = build_frame(b'line1', WSMsgType.TEXT, is_fin=False)
+    parser._feed_data(data1)
 
-    parser._feed_data(b'')
+    data2 = build_frame(b'line2', WSMsgType.CONTINUATION)
+    parser._feed_data(data2)
 
     res = out._buffer[0]
     assert res == (WSMessage(WSMsgType.TEXT, 'line1line2', ''), 10)
@@ -254,7 +260,15 @@ def test_continuation_with_ping(out, parser):
         (1, WSMsgType.CONTINUATION, b'line2'),
     ]
 
-    parser.feed_data(b'')
+    data1 = build_frame(b'line1', WSMsgType.TEXT, is_fin=False)
+    parser._feed_data(data1)
+
+    data2 = build_frame(b'', WSMsgType.PING)
+    parser._feed_data(data2)
+
+    data3 = build_frame(b'line2', WSMsgType.CONTINUATION)
+    parser._feed_data(data3)
+
     res = out._buffer[0]
     assert res == (WSMessage(WSMsgType.PING, b'', ''), 0)
     res = out._buffer[1]