Check the opcode of the frame

We implement a system of opcode checking so we can differentiate the
types of frame we are receiving.

In case the opcode is unknown, we close the connection according to RFC
6455: "If an unknown opcode is received, the receiving endpoint MUST
_Fail the WebSocket Connection_."

However, if the opcode is know but we do not support it, we just display
 a warning and ignore the frame.

For now on, nothing happens if we receive a PING or PONG frame.

fixed Pithikos#6

Signed-off-by: Olivier Gayot <[email protected]>

Author: ogayot

websocket_server/websocket_server.py

@@ -37,9 +37,12 @@
 PAYLOAD_LEN_EXT16 = 0x7e
 PAYLOAD_LEN_EXT64 = 0x7f
 
-OPCODE_TEXT = 0x01
-CLOSE_CONN  = 0x8
-
+OPCODE_CONTINUATION = 0x0
+OPCODE_TEXT         = 0x1
+OPCODE_BINARY       = 0x2
+OPCODE_CLOSE_CONN   = 0x8
+OPCODE_PING         = 0x9
+OPCODE_PONG         = 0xA
 
 
 # -------------------------------- API ---------------------------------
@@ -99,6 +102,12 @@ def __init__(self, port, host='127.0.0.1'):
 	def _message_received_(self, handler, msg):
 		self.message_received(self.handler_to_client(handler), self, msg)
 
+	def _ping_received_(self, handler, msg):
+		pass
+
+	def _pong_received_(self, handler, msg):
+		pass
+
 	def _new_client_(self, handler):
 		self.id_counter += 1
 		client={
@@ -164,19 +173,36 @@ def read_next_message(self):
 		opcode = b1 & OPCODE
 		masked = b2 & MASKED
 		payload_length = b2 & PAYLOAD_LEN
+		opcode_handler = None
 
 		if not b1:
 			print("Client closed connection.")
 			self.keep_alive = 0
 			return
-		if opcode == CLOSE_CONN:
+		if opcode == OPCODE_CLOSE_CONN:
 			print("Client asked to close connection.")
 			self.keep_alive = 0
 			return
 		if not masked:
 			print("Client must always be masked.")
 			self.keep_alive = 0
 			return
+		if opcode == OPCODE_CONTINUATION:
+			print("Continuation frames not handled.")
+			return
+		elif opcode == OPCODE_BINARY:
+			print("Binary frames not handled.")
+			return
+		elif opcode == OPCODE_TEXT:
+			opcode_handler = self.server._message_received_
+		elif opcode == OPCODE_PING:
+			opcode_handler = self.server._ping_received_
+		elif opcode == OPCODE_PONG:
+			opcode_handler = self.server._pong_received_
+		else:
+			print("Unknown opcode %#x." + opcode)
+			self.keep_alive = 0
+			return
 
 		if payload_length == 126:
 			payload_length = struct.unpack(">H", self.rfile.read(2))[0]
@@ -188,7 +214,7 @@ def read_next_message(self):
 		for char in self.read_bytes(payload_length):
 			char ^= masks[len(decoded) % 4]
 			decoded += chr(char)
-		self.server._message_received_(self, decoded)
+		opcode_handler(self, decoded)
 
 	def send_message(self, message):
 		self.send_text(message)