Validate size when sending out of range frames

When sending a frame to the server, care must be taken to not exceed the maximum frame size setting. If the size is higher than the defined setting then a ValueError is thrown.

Author: jdecuyper

hyper/http20/connection.py

@@ -510,8 +510,12 @@ def _send_cb(self, frame, tolerate_peer_gone=False):
 
         data = frame.serialize()
 
-        if frame.body_len > FRAME_MAX_LEN:  # pragma: no cover
-            raise ValueError("Frame size %d is too large" % frame.body_len)
+        if frame.body_len > self._settings[SettingsFrame.SETTINGS_MAX_FRAME_SIZE]:
+            raise ValueError(
+                     "Frame size %d exceeds maximum frame size setting %d" %
+                     (frame.body_len,
+                     self._settings[SettingsFrame.SETTINGS_MAX_FRAME_SIZE])
+            )
 
         log.info(
             "Sending frame %s on stream %d",

test/test_hyper.py

@@ -1351,9 +1351,12 @@ def data_callback(frame):
     def test_connection_sends_rst_frame_if_frame_size_too_large(self):
         sock = DummySocket()
         d = DataFrame(1)
-        # Create big data frame that exceeds the FRAME_MAX_LEN value in order
-        # to trigger the reset frame with error code 6 (FRAME_SIZE_ERROR)
-        d.data = b''.join([b"hi there sir" for x in range(40)])
+        # Receive oversized frame on the client side.
+        # Create huge data frame that exceeds the FRAME_MAX_LEN value in order
+        # to trigger the reset frame with error code 6 (FRAME_SIZE_ERROR).
+        # FRAME_MAX_LEN is a constant value for the hyper client and cannot 
+        # be updated as of now.
+        d.data = b''.join([b"hi there client" for x in range(40)])
         sock.buffer = BytesIO(d.serialize())
 
         frames = []
@@ -1375,7 +1378,7 @@ def send_rst_frame(stream_id, error_code):
         assert f.stream_id == 1
         assert f.error_code == 6 #FRAME_SIZE_ERROR
 
-    def test_connection_stream_is_removed_on_frame_size_error(self):
+    def test_connection_stream_is_removed_when_receiving_out_of_range_frame(self):
         sock = DummySocket()
         d = DataFrame(1)
         d.data = b''.join([b"hi there sir" for x in range(40)])
@@ -1391,6 +1394,20 @@ def test_connection_stream_is_removed_on_frame_size_error(self):
         c._recv_cb()
         assert len(c.streams) == 0
 
+    def test_connection_error_when_send_out_of_range_frame(self):
+        # Send oversized frame to the server side.
+        # Create huge data frame that exceeds the intitial FRAME_MAX_LEN setting
+        # in order to trigger a value error when sending it.
+        # Note that the value of the FRAME_MAX_LEN setting can be updated
+        # by the server through a settings frame.
+        d = DataFrame(1)
+        d.data = b''.join([b"hi there server" for x in range(1500)])
+
+        c = HTTP20Connection('www.google.com')
+        c._sock = DummySocket()
+        with pytest.raises(ValueError):
+            c._send_cb(d)
+
 # Some utility classes for the tests.
 class NullEncoder(object):
     @staticmethod