# Copyright 2012, Google Inc.
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#
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# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
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"""This file provides classes and helper functions for parsing/building frames
of the WebSocket protocol (RFC 6455).
Specification:
http://tools.ietf.org/html/rfc6455
"""
from collections import deque
import logging
import os
import struct
import time
from mod_pywebsocket import common
from mod_pywebsocket import util
from mod_pywebsocket._stream_base import BadOperationException
from mod_pywebsocket._stream_base import ConnectionTerminatedException
from mod_pywebsocket._stream_base import InvalidFrameException
from mod_pywebsocket._stream_base import InvalidUTF8Exception
from mod_pywebsocket._stream_base import StreamBase
from mod_pywebsocket._stream_base import UnsupportedFrameException
_NOOP_MASKER = util.NoopMasker()
class Frame(object):
def __init__(self, fin=1, rsv1=0, rsv2=0, rsv3=0,
opcode=None, payload=''):
self.fin = fin
self.rsv1 = rsv1
self.rsv2 = rsv2
self.rsv3 = rsv3
self.opcode = opcode
self.payload = payload
# Helper functions made public to be used for writing unittests for WebSocket
# clients.
def create_length_header(length, mask):
"""Creates a length header.
Args:
length: Frame length. Must be less than 2^63.
mask: Mask bit. Must be boolean.
Raises:
ValueError: when bad data is given.
"""
if mask:
mask_bit = 1 << 7
else:
mask_bit = 0
if length < 0:
raise ValueError('length must be non negative integer')
elif length <= 125:
return chr(mask_bit | length)
elif length < (1 << 16):
return chr(mask_bit | 126) + struct.pack('!H', length)
elif length < (1 << 63):
return chr(mask_bit | 127) + struct.pack('!Q', length)
else:
raise ValueError('Payload is too big for one frame')
def create_header(opcode, payload_length, fin, rsv1, rsv2, rsv3, mask):
"""Creates a frame header.
Raises:
Exception: when bad data is given.
"""
if opcode < 0 or 0xf < opcode:
raise ValueError('Opcode out of range')
if payload_length < 0 or (1 << 63) <= payload_length:
raise ValueError('payload_length out of range')
if (fin | rsv1 | rsv2 | rsv3) & ~1:
raise ValueError('FIN bit and Reserved bit parameter must be 0 or 1')
header = ''
first_byte = ((fin << 7)
| (rsv1 << 6) | (rsv2 << 5) | (rsv3 << 4)
| opcode)
header += chr(first_byte)
header += create_length_header(payload_length, mask)
return header
def _build_frame(header, body, mask):
if not mask:
return header + body
masking_nonce = os.urandom(4)
masker = util.RepeatedXorMasker(masking_nonce)
return header + masking_nonce + masker.mask(body)
def _filter_and_format_frame_object(frame, mask, frame_filters):
for frame_filter in frame_filters:
frame_filter.filter(frame)
header = create_header(
frame.opcode, len(frame.payload), frame.fin,
frame.rsv1, frame.rsv2, frame.rsv3, mask)
return _build_frame(header, frame.payload, mask)
def create_binary_frame(
message, opcode=common.OPCODE_BINARY, fin=1, mask=False, frame_filters=[]):
"""Creates a simple binary frame with no extension, reserved bit."""
frame = Frame(fin=fin, opcode=opcode, payload=message)
return _filter_and_format_frame_object(frame, mask, frame_filters)
def create_text_frame(
message, opcode=common.OPCODE_TEXT, fin=1, mask=False, frame_filters=[]):
"""Creates a simple text frame with no extension, reserved bit."""
encoded_message = message.encode('utf-8')
return create_binary_frame(encoded_message, opcode, fin, mask,
frame_filters)
def parse_frame(receive_bytes, logger=None,
ws_version=common.VERSION_HYBI_LATEST,
unmask_receive=True):
"""Parses a frame. Returns a tuple containing each header field and
payload.
Args:
receive_bytes: a function that reads frame data from a stream or
something similar. The function takes length of the bytes to be
read. The function must raise ConnectionTerminatedException if
there is not enough data to be read.
logger: a logging object.
ws_version: the version of WebSocket protocol.
unmask_receive: unmask received frames. When received unmasked
frame, raises InvalidFrameException.
Raises:
ConnectionTerminatedException: when receive_bytes raises it.
InvalidFrameException: when the frame contains invalid data.
"""
if not logger:
logger = logging.getLogger()
logger.log(common.LOGLEVEL_FINE, 'Receive the first 2 octets of a frame')
received = receive_bytes(2)
first_byte = ord(received[0])
fin = (first_byte >> 7) & 1
rsv1 = (first_byte >> 6) & 1
rsv2 = (first_byte >> 5) & 1
rsv3 = (first_byte >> 4) & 1
opcode = first_byte & 0xf
second_byte = ord(received[1])
mask = (second_byte >> 7) & 1
payload_length = second_byte & 0x7f
logger.log(common.LOGLEVEL_FINE,
'FIN=%s, RSV1=%s, RSV2=%s, RSV3=%s, opcode=%s, '
'Mask=%s, Payload_length=%s',
fin, rsv1, rsv2, rsv3, opcode, mask, payload_length)
if (mask == 1) != unmask_receive:
raise InvalidFrameException(
'Mask bit on the received frame did\'nt match masking '
'configuration for received frames')
# The HyBi and later specs disallow putting a value in 0x0-0xFFFF
# into the 8-octet extended payload length field (or 0x0-0xFD in
# 2-octet field).
valid_length_encoding = True
length_encoding_bytes = 1
if payload_length == 127:
logger.log(common.LOGLEVEL_FINE,
'Receive 8-octet extended payload length')
extended_payload_length = receive_bytes(8)
payload_length = struct.unpack(
'!Q', extended_payload_length)[0]
if payload_length > 0x7FFFFFFFFFFFFFFF:
raise InvalidFrameException(
'Extended payload length >= 2^63')
if ws_version >= 13 and payload_length < 0x10000:
valid_length_encoding = False
length_encoding_bytes = 8
logger.log(common.LOGLEVEL_FINE,
'Decoded_payload_length=%s', payload_length)
elif payload_length == 126:
logger.log(common.LOGLEVEL_FINE,
'Receive 2-octet extended payload length')
extended_payload_length = receive_bytes(2)
payload_length = struct.unpack(
'!H', extended_payload_length)[0]
if ws_version >= 13 and payload_length < 126:
valid_length_encoding = False
length_encoding_bytes = 2
logger.log(common.LOGLEVEL_FINE,
'Decoded_payload_length=%s', payload_length)
if not valid_length_encoding:
logger.warning(
'Payload length is not encoded using the minimal number of '
'bytes (%d is encoded using %d bytes)',
payload_length,
length_encoding_bytes)
if mask == 1:
logger.log(common.LOGLEVEL_FINE, 'Receive mask')
masking_nonce = receive_bytes(4)
masker = util.RepeatedXorMasker(masking_nonce)
logger.log(common.LOGLEVEL_FINE, 'Mask=%r', masking_nonce)
else:
masker = _NOOP_MASKER
logger.log(common.LOGLEVEL_FINE, 'Receive payload data')
if logger.isEnabledFor(common.LOGLEVEL_FINE):
receive_start = time.time()
raw_payload_bytes = receive_bytes(payload_length)
if logger.isEnabledFor(common.LOGLEVEL_FINE):
logger.log(
common.LOGLEVEL_FINE,
'Done receiving payload data at %s MB/s',
payload_length / (time.time() - receive_start) / 1000 / 1000)
logger.log(common.LOGLEVEL_FINE, 'Unmask payload data')
if logger.isEnabledFor(common.LOGLEVEL_FINE):
unmask_start = time.time()
bytes = masker.mask(raw_payload_bytes)
if logger.isEnabledFor(common.LOGLEVEL_FINE):
logger.log(
common.LOGLEVEL_FINE,
'Done unmasking payload data at %s MB/s',
payload_length / (time.time() - unmask_start) / 1000 / 1000)
return opcode, bytes, fin, rsv1, rsv2, rsv3
class FragmentedFrameBuilder(object):
"""A stateful class to send a message as fragments."""
def __init__(self, mask, frame_filters=[], encode_utf8=True):
"""Constructs an instance."""
self._mask = mask
self._frame_filters = frame_filters
# This is for skipping UTF-8 encoding when building text type frames
# from compressed data.
self._encode_utf8 = encode_utf8
self._started = False
# Hold opcode of the first frame in messages to verify types of other
# frames in the message are all the same.
self._opcode = common.OPCODE_TEXT
def build(self, message, end, binary):
if binary:
frame_type = common.OPCODE_BINARY
else:
frame_type = common.OPCODE_TEXT
if self._started:
if self._opcode != frame_type:
raise ValueError('Message types are different in frames for '
'the same message')
opcode = common.OPCODE_CONTINUATION
else:
opcode = frame_type
self._opcode = frame_type
if end:
self._started = False
fin = 1
else:
self._started = True
fin = 0
if binary or not self._encode_utf8:
return create_binary_frame(
message, opcode, fin, self._mask, self._frame_filters)
else:
return create_text_frame(
message, opcode, fin, self._mask, self._frame_filters)
def _create_control_frame(opcode, body, mask, frame_filters):
frame = Frame(opcode=opcode, payload=body)
for frame_filter in frame_filters:
frame_filter.filter(frame)
if len(frame.payload) > 125:
raise BadOperationException(
'Payload data size of control frames must be 125 bytes or less')
header = create_header(
frame.opcode, len(frame.payload), frame.fin,
frame.rsv1, frame.rsv2, frame.rsv3, mask)
return _build_frame(header, frame.payload, mask)
def create_ping_frame(body, mask=False, frame_filters=[]):
return _create_control_frame(common.OPCODE_PING, body, mask, frame_filters)
def create_pong_frame(body, mask=False, frame_filters=[]):
return _create_control_frame(common.OPCODE_PONG, body, mask, frame_filters)
def create_close_frame(body, mask=False, frame_filters=[]):
return _create_control_frame(
common.OPCODE_CLOSE, body, mask, frame_filters)
def create_closing_handshake_body(code, reason):
body = ''
if code is not None:
if (code > common.STATUS_USER_PRIVATE_MAX or
code < common.STATUS_NORMAL_CLOSURE):
raise BadOperationException('Status code is out of range')
if (code == common.STATUS_NO_STATUS_RECEIVED or
code == common.STATUS_ABNORMAL_CLOSURE or
code == common.STATUS_TLS_HANDSHAKE):
raise BadOperationException('Status code is reserved pseudo '
'code')
encoded_reason = reason.encode('utf-8')
body = struct.pack('!H', code) + encoded_reason
return body
class StreamOptions(object):
"""Holds option values to configure Stream objects."""
def __init__(self):
"""Constructs StreamOptions."""
# Enables deflate-stream extension.
self.deflate_stream = False
# Filters applied to frames.
self.outgoing_frame_filters = []
self.incoming_frame_filters = []
# Filters applied to messages. Control frames are not affected by them.
self.outgoing_message_filters = []
self.incoming_message_filters = []
self.encode_text_message_to_utf8 = True
self.mask_send = False
self.unmask_receive = True
# RFC6455 disallows fragmented control frames, but mux extension
# relaxes the restriction.
self.allow_fragmented_control_frame = False
class Stream(StreamBase):
"""A class for parsing/building frames of the WebSocket protocol
(RFC 6455).
"""
def __init__(self, request, options):
"""Constructs an instance.
Args:
request: mod_python request.
"""
StreamBase.__init__(self, request)
self._logger = util.get_class_logger(self)
self._options = options
if self._options.deflate_stream:
self._logger.debug('Setup filter for deflate-stream')
self._request = util.DeflateRequest(self._request)
self._request.client_terminated = False
self._request.server_terminated = False
# Holds body of received fragments.
self._received_fragments = []
# Holds the opcode of the first fragment.
self._original_opcode = None
self._writer = FragmentedFrameBuilder(
self._options.mask_send, self._options.outgoing_frame_filters,
self._options.encode_text_message_to_utf8)
self._ping_queue = deque()
def _receive_frame(self):
"""Receives a frame and return data in the frame as a tuple containing
each header field and payload separately.
Raises:
ConnectionTerminatedException: when read returns empty
string.
InvalidFrameException: when the frame contains invalid data.
"""
def _receive_bytes(length):
return self.receive_bytes(length)
return parse_frame(receive_bytes=_receive_bytes,
logger=self._logger,
ws_version=self._request.ws_version,
unmask_receive=self._options.unmask_receive)
def _receive_frame_as_frame_object(self):
opcode, bytes, fin, rsv1, rsv2, rsv3 = self._receive_frame()
return Frame(fin=fin, rsv1=rsv1, rsv2=rsv2, rsv3=rsv3,
opcode=opcode, payload=bytes)
def send_message(self, message, end=True, binary=False):
"""Send message.
Args:
message: text in unicode or binary in str to send.
binary: send message as binary frame.
Raises:
BadOperationException: when called on a server-terminated
connection or called with inconsistent message type or
binary parameter.
"""
if self._request.server_terminated:
raise BadOperationException(
'Requested send_message after sending out a closing handshake')
if binary and isinstance(message, unicode):
raise BadOperationException(
'Message for binary frame must be instance of str')
for message_filter in self._options.outgoing_message_filters:
message = message_filter.filter(message, end, binary)
try:
self._write(self._writer.build(message, end, binary))
except ValueError, e:
raise BadOperationException(e)
def _get_message_from_frame(self, frame):
"""Gets a message from frame. If the message is composed of fragmented
frames and the frame is not the last fragmented frame, this method
returns None. The whole message will be returned when the last
fragmented frame is passed to this method.
Raises:
InvalidFrameException: when the frame doesn't match defragmentation
context, or the frame contains invalid data.
"""
if frame.opcode == common.OPCODE_CONTINUATION:
if not self._received_fragments:
if frame.fin:
raise InvalidFrameException(
'Received a termination frame but fragmentation '
'not started')
else:
raise InvalidFrameException(
'Received an intermediate frame but '
'fragmentation not started')
if frame.fin:
# End of fragmentation frame
self._received_fragments.append(frame.payload)
message = ''.join(self._received_fragments)
self._received_fragments = []
return message
else:
# Intermediate frame
self._received_fragments.append(frame.payload)
return None
else:
if self._received_fragments:
if frame.fin:
raise InvalidFrameException(
'Received an unfragmented frame without '
'terminating existing fragmentation')
else:
raise InvalidFrameException(
'New fragmentation started without terminating '
'existing fragmentation')
if frame.fin:
# Unfragmented frame
self._original_opcode = frame.opcode
return frame.payload
else:
# Start of fragmentation frame
if (not self._options.allow_fragmented_control_frame and
common.is_control_opcode(frame.opcode)):
raise InvalidFrameException(
'Control frames must not be fragmented')
self._original_opcode = frame.opcode
self._received_fragments.append(frame.payload)
return None
def _process_close_message(self, message):
"""Processes close message.
Args:
message: close message.
Raises:
InvalidFrameException: when the message is invalid.
"""
self._request.client_terminated = True
# Status code is optional. We can have status reason only if we
# have status code. Status reason can be empty string. So,
# allowed cases are
# - no application data: no code no reason
# - 2 octet of application data: has code but no reason
# - 3 or more octet of application data: both code and reason
if len(message) == 0:
self._logger.debug('Received close frame (empty body)')
self._request.ws_close_code = (
common.STATUS_NO_STATUS_RECEIVED)
elif len(message) == 1:
raise InvalidFrameException(
'If a close frame has status code, the length of '
'status code must be 2 octet')
elif len(message) >= 2:
self._request.ws_close_code = struct.unpack(
'!H', message[0:2])[0]
self._request.ws_close_reason = message[2:].decode(
'utf-8', 'replace')
self._logger.debug(
'Received close frame (code=%d, reason=%r)',
self._request.ws_close_code,
self._request.ws_close_reason)
# Drain junk data after the close frame if necessary.
self._drain_received_data()
if self._request.server_terminated:
self._logger.debug(
'Received ack for server-initiated closing handshake')
return
self._logger.debug(
'Received client-initiated closing handshake')
code = common.STATUS_NORMAL_CLOSURE
reason = ''
if hasattr(self._request, '_dispatcher'):
dispatcher = self._request._dispatcher
code, reason = dispatcher.passive_closing_handshake(
self._request)
if code is None and reason is not None and len(reason) > 0:
self._logger.warning(
'Handler specified reason despite code being None')
reason = ''
if reason is None:
reason = ''
self._send_closing_handshake(code, reason)
self._logger.debug(
'Sent ack for client-initiated closing handshake '
'(code=%r, reason=%r)', code, reason)
def _process_ping_message(self, message):
"""Processes ping message.
Args:
message: ping message.
"""
try:
handler = self._request.on_ping_handler
if handler:
handler(self._request, message)
return
except AttributeError, e:
pass
self._send_pong(message)
def _process_pong_message(self, message):
"""Processes pong message.
Args:
message: pong message.
"""
# TODO(tyoshino): Add ping timeout handling.
inflight_pings = deque()
while True:
try:
expected_body = self._ping_queue.popleft()
if expected_body == message:
# inflight_pings contains pings ignored by the
# other peer. Just forget them.
self._logger.debug(
'Ping %r is acked (%d pings were ignored)',
expected_body, len(inflight_pings))
break
else:
inflight_pings.append(expected_body)
except IndexError, e:
# The received pong was unsolicited pong. Keep the
# ping queue as is.
self._ping_queue = inflight_pings
self._logger.debug('Received a unsolicited pong')
break
try:
handler = self._request.on_pong_handler
if handler:
handler(self._request, message)
except AttributeError, e:
pass
def receive_message(self):
"""Receive a WebSocket frame and return its payload as a text in
unicode or a binary in str.
Returns:
payload data of the frame
- as unicode instance if received text frame
- as str instance if received binary frame
or None iff received closing handshake.
Raises:
BadOperationException: when called on a client-terminated
connection.
ConnectionTerminatedException: when read returns empty
string.
InvalidFrameException: when the frame contains invalid
data.
UnsupportedFrameException: when the received frame has
flags, opcode we cannot handle. You can ignore this
exception and continue receiving the next frame.
"""
if self._request.client_terminated:
raise BadOperationException(
'Requested receive_message after receiving a closing '
'handshake')
while True:
# mp_conn.read will block if no bytes are available.
# Timeout is controlled by TimeOut directive of Apache.
frame = self._receive_frame_as_frame_object()
# Check the constraint on the payload size for control frames
# before extension processes the frame.
# See also http://tools.ietf.org/html/rfc6455#section-5.5
if (common.is_control_opcode(frame.opcode) and
len(frame.payload) > 125):
raise InvalidFrameException(
'Payload data size of control frames must be 125 bytes or '
'less')
for frame_filter in self._options.incoming_frame_filters:
frame_filter.filter(frame)
if frame.rsv1 or frame.rsv2 or frame.rsv3:
raise UnsupportedFrameException(
'Unsupported flag is set (rsv = %d%d%d)' %
(frame.rsv1, frame.rsv2, frame.rsv3))
message = self._get_message_from_frame(frame)
if message is None:
continue
for message_filter in self._options.incoming_message_filters:
message = message_filter.filter(message)
if self._original_opcode == common.OPCODE_TEXT:
# The WebSocket protocol section 4.4 specifies that invalid
# characters must be replaced with U+fffd REPLACEMENT
# CHARACTER.
try:
return message.decode('utf-8')
except UnicodeDecodeError, e:
raise InvalidUTF8Exception(e)
elif self._original_opcode == common.OPCODE_BINARY:
return message
elif self._original_opcode == common.OPCODE_CLOSE:
self._process_close_message(message)
return None
elif self._original_opcode == common.OPCODE_PING:
self._process_ping_message(message)
elif self._original_opcode == common.OPCODE_PONG:
self._process_pong_message(message)
else:
raise UnsupportedFrameException(
'Opcode %d is not supported' % self._original_opcode)
def _send_closing_handshake(self, code, reason):
body = create_closing_handshake_body(code, reason)
frame = create_close_frame(
body, mask=self._options.mask_send,
frame_filters=self._options.outgoing_frame_filters)
self._request.server_terminated = True
self._write(frame)
def close_connection(self, code=common.STATUS_NORMAL_CLOSURE, reason=''):
"""Closes a WebSocket connection.
Args:
code: Status code for close frame. If code is None, a close
frame with empty body will be sent.
reason: string representing close reason.
Raises:
BadOperationException: when reason is specified with code None
or reason is not an instance of both str and unicode.
"""
if self._request.server_terminated:
self._logger.debug(
'Requested close_connection but server is already terminated')
return
if code is None:
if reason is not None and len(reason) > 0:
raise BadOperationException(
'close reason must not be specified if code is None')
reason = ''
else:
if not isinstance(reason, str) and not isinstance(reason, unicode):
raise BadOperationException(
'close reason must be an instance of str or unicode')
self._send_closing_handshake(code, reason)
self._logger.debug(
'Sent server-initiated closing handshake (code=%r, reason=%r)',
code, reason)
if (code == common.STATUS_GOING_AWAY or
code == common.STATUS_PROTOCOL_ERROR):
# It doesn't make sense to wait for a close frame if the reason is
# protocol error or that the server is going away. For some of
# other reasons, it might not make sense to wait for a close frame,
# but it's not clear, yet.
return
# TODO(ukai): 2. wait until the /client terminated/ flag has been set,
# or until a server-defined timeout expires.
#
# For now, we expect receiving closing handshake right after sending
# out closing handshake.
message = self.receive_message()
if message is not None:
raise ConnectionTerminatedException(
'Didn\'t receive valid ack for closing handshake')
# TODO: 3. close the WebSocket connection.
# note: mod_python Connection (mp_conn) doesn't have close method.
def send_ping(self, body=''):
frame = create_ping_frame(
body,
self._options.mask_send,
self._options.outgoing_frame_filters)
self._write(frame)
self._ping_queue.append(body)
def _send_pong(self, body):
frame = create_pong_frame(
body,
self._options.mask_send,
self._options.outgoing_frame_filters)
self._write(frame)
def get_last_received_opcode(self):
"""Returns the opcode of the WebSocket message which the last received
frame belongs to. The return value is valid iff immediately after
receive_message call.
"""
return self._original_opcode
def _drain_received_data(self):
"""Drains unread data in the receive buffer to avoid sending out TCP
RST packet. This is because when deflate-stream is enabled, some
DEFLATE block for flushing data may follow a close frame. If any data
remains in the receive buffer of a socket when the socket is closed,
it sends out TCP RST packet to the other peer.
Since mod_python's mp_conn object doesn't support non-blocking read,
we perform this only when pywebsocket is running in standalone mode.
"""
# If self._options.deflate_stream is true, self._request is
# DeflateRequest, so we can get wrapped request object by
# self._request._request.
#
# Only _StandaloneRequest has _drain_received_data method.
if (self._options.deflate_stream and
('_drain_received_data' in dir(self._request._request))):
self._request._request._drain_received_data()
# vi:sts=4 sw=4 et