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524 lines
18 KiB
Python
524 lines
18 KiB
Python
# Copyright 2011, Google Inc.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are
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# met:
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#
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following disclaimer
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# in the documentation and/or other materials provided with the
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# distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived from
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# this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""Stream class for IETF HyBi 07 WebSocket protocol.
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"""
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from collections import deque
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import os
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import struct
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from mod_pywebsocket import common
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from mod_pywebsocket import util
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from mod_pywebsocket._stream_base import BadOperationException
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from mod_pywebsocket._stream_base import ConnectionTerminatedException
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from mod_pywebsocket._stream_base import InvalidFrameException
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from mod_pywebsocket._stream_base import StreamBase
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from mod_pywebsocket._stream_base import UnsupportedFrameException
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def is_control_opcode(opcode):
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return (opcode >> 3) == 1
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_NOOP_MASKER = util.NoopMasker()
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# Helper functions made public to be used for writing unittests for WebSocket
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# clients.
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def create_length_header(length, mask):
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"""Creates a length header.
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Args:
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length: Frame length. Must be less than 2^63.
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mask: Mask bit. Must be boolean.
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Raises:
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ValueError: when bad data is given.
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"""
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if mask:
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mask_bit = 1 << 7
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else:
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mask_bit = 0
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if length < 0:
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raise ValueError('length must be non negative integer')
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elif length <= 125:
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return chr(mask_bit | length)
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elif length < (1 << 16):
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return chr(mask_bit | 126) + struct.pack('!H', length)
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elif length < (1 << 63):
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return chr(mask_bit | 127) + struct.pack('!Q', length)
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else:
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raise ValueError('Payload is too big for one frame')
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def create_header(opcode, payload_length, fin, rsv1, rsv2, rsv3, mask):
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"""Creates a frame header.
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Raises:
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Exception: when bad data is given.
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"""
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if opcode < 0 or 0xf < opcode:
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raise ValueError('Opcode out of range')
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if payload_length < 0 or (1 << 63) <= payload_length:
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raise ValueError('payload_length out of range')
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if (fin | rsv1 | rsv2 | rsv3) & ~1:
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raise ValueError('FIN bit and Reserved bit parameter must be 0 or 1')
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header = ''
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first_byte = ((fin << 7)
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| (rsv1 << 6) | (rsv2 << 5) | (rsv3 << 4)
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| opcode)
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header += chr(first_byte)
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header += create_length_header(payload_length, mask)
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return header
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def _build_frame(header, body, mask):
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if not mask:
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return header + body
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masking_nonce = os.urandom(4)
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masker = util.RepeatedXorMasker(masking_nonce)
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return header + masking_nonce + masker.mask(body)
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def create_text_frame(message, opcode=common.OPCODE_TEXT, fin=1, mask=False):
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"""Creates a simple text frame with no extension, reserved bit."""
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encoded_message = message.encode('utf-8')
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header = create_header(opcode, len(encoded_message), fin, 0, 0, 0, mask)
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return _build_frame(header, encoded_message, mask)
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class FragmentedTextFrameBuilder(object):
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"""A stateful class to send a message as fragments."""
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def __init__(self, mask):
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"""Constructs an instance."""
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self._mask = mask
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self._started = False
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def build(self, message, end):
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if self._started:
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opcode = common.OPCODE_CONTINUATION
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else:
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opcode = common.OPCODE_TEXT
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if end:
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self._started = False
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fin = 1
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else:
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self._started = True
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fin = 0
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return create_text_frame(message, opcode, fin, self._mask)
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def create_ping_frame(body, mask=False):
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header = create_header(common.OPCODE_PING, len(body), 1, 0, 0, 0, mask)
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return _build_frame(header, body, mask)
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def create_pong_frame(body, mask=False):
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header = create_header(common.OPCODE_PONG, len(body), 1, 0, 0, 0, mask)
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return _build_frame(header, body, mask)
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def create_close_frame(body, mask=False):
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header = create_header(common.OPCODE_CLOSE, len(body), 1, 0, 0, 0, mask)
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return _build_frame(header, body, mask)
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class StreamOptions(object):
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"""Holds option values to configure Stream objects."""
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def __init__(self):
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"""Constructs StreamOptions."""
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self.deflate = False
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self.mask_send = False
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self.unmask_receive = True
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class Stream(StreamBase):
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"""Stream of WebSocket messages."""
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def __init__(self, request, options):
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"""Constructs an instance.
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Args:
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request: mod_python request.
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"""
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StreamBase.__init__(self, request)
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self._logger = util.get_class_logger(self)
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self._options = options
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if self._options.deflate:
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self._logger.debug('Deflated stream')
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self._request = util.DeflateRequest(self._request)
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self._request.client_terminated = False
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self._request.server_terminated = False
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# Holds body of received fragments.
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self._received_fragments = []
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# Holds the opcode of the first fragment.
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self._original_opcode = None
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self._writer = FragmentedTextFrameBuilder(self._options.mask_send)
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self._ping_queue = deque()
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def _receive_frame(self):
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"""Receives a frame and return data in the frame as a tuple containing
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each header field and payload separately.
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Raises:
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ConnectionTerminatedException: when read returns empty
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string.
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InvalidFrameException: when the frame contains invalid data.
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"""
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received = self.receive_bytes(2)
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first_byte = ord(received[0])
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fin = (first_byte >> 7) & 1
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rsv1 = (first_byte >> 6) & 1
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rsv2 = (first_byte >> 5) & 1
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rsv3 = (first_byte >> 4) & 1
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opcode = first_byte & 0xf
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second_byte = ord(received[1])
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mask = (second_byte >> 7) & 1
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payload_length = second_byte & 0x7f
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if (mask == 1) != self._options.unmask_receive:
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raise InvalidFrameException(
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'Mask bit on the received frame did\'nt match masking '
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'configuration for received frames')
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# The spec doesn't disallow putting a value in 0x0-0xFFFF into the
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# 8-octet extended payload length field (or 0x0-0xFD in 2-octet field).
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# So, we don't check the range of extended_payload_length.
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if payload_length == 127:
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extended_payload_length = self.receive_bytes(8)
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payload_length = struct.unpack(
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'!Q', extended_payload_length)[0]
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if payload_length > 0x7FFFFFFFFFFFFFFF:
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raise InvalidFrameException(
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'Extended payload length >= 2^63')
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elif payload_length == 126:
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extended_payload_length = self.receive_bytes(2)
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payload_length = struct.unpack(
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'!H', extended_payload_length)[0]
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if mask == 1:
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masking_nonce = self.receive_bytes(4)
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masker = util.RepeatedXorMasker(masking_nonce)
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else:
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masker = _NOOP_MASKER
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bytes = masker.mask(self.receive_bytes(payload_length))
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return opcode, bytes, fin, rsv1, rsv2, rsv3
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def send_message(self, message, end=True):
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"""Send message.
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Args:
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message: unicode string to send.
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Raises:
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BadOperationException: when called on a server-terminated
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connection.
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"""
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if self._request.server_terminated:
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raise BadOperationException(
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'Requested send_message after sending out a closing handshake')
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self._write(self._writer.build(message, end))
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def receive_message(self):
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"""Receive a WebSocket frame and return its payload an unicode string.
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Returns:
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payload unicode string in a WebSocket frame. None iff received
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closing handshake.
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Raises:
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BadOperationException: when called on a client-terminated
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connection.
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ConnectionTerminatedException: when read returns empty
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string.
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InvalidFrameException: when the frame contains invalid
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data.
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UnsupportedFrameException: when the received frame has
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flags, opcode we cannot handle. You can ignore this exception
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and continue receiving the next frame.
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"""
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if self._request.client_terminated:
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raise BadOperationException(
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'Requested receive_message after receiving a closing '
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'handshake')
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while True:
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# mp_conn.read will block if no bytes are available.
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# Timeout is controlled by TimeOut directive of Apache.
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opcode, bytes, fin, rsv1, rsv2, rsv3 = self._receive_frame()
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if rsv1 or rsv2 or rsv3:
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raise UnsupportedFrameException(
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'Unsupported flag is set (rsv = %d%d%d)' %
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(rsv1, rsv2, rsv3))
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if opcode == common.OPCODE_CONTINUATION:
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if not self._received_fragments:
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if fin:
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raise InvalidFrameException(
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'Received a termination frame but fragmentation '
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'not started')
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else:
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raise InvalidFrameException(
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'Received an intermediate frame but '
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'fragmentation not started')
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if fin:
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# End of fragmentation frame
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self._received_fragments.append(bytes)
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message = ''.join(self._received_fragments)
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self._received_fragments = []
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else:
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# Intermediate frame
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self._received_fragments.append(bytes)
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continue
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else:
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if self._received_fragments:
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if fin:
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raise InvalidFrameException(
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'Received an unfragmented frame without '
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'terminating existing fragmentation')
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else:
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raise InvalidFrameException(
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'New fragmentation started without terminating '
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'existing fragmentation')
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if fin:
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# Unfragmented frame
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self._original_opcode = opcode
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message = bytes
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if is_control_opcode(opcode) and len(message) > 125:
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raise InvalidFrameException(
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'Application data size of control frames must be '
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'125 bytes or less')
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else:
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# Start of fragmentation frame
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if is_control_opcode(opcode):
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raise InvalidFrameException(
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'Control frames must not be fragmented')
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self._original_opcode = opcode
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self._received_fragments.append(bytes)
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continue
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if self._original_opcode == common.OPCODE_TEXT:
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# The WebSocket protocol section 4.4 specifies that invalid
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# characters must be replaced with U+fffd REPLACEMENT
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# CHARACTER.
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return message.decode('utf-8', 'replace')
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elif self._original_opcode == common.OPCODE_CLOSE:
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self._request.client_terminated = True
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# Status code is optional. We can have status reason only if we
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# have status code. Status reason can be empty string. So,
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# allowed cases are
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# - no application data: no code no reason
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# - 2 octet of application data: has code but no reason
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# - 3 or more octet of application data: both code and reason
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if len(message) == 1:
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raise InvalidFrameException(
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'If a close frame has status code, the length of '
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'status code must be 2 octet')
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elif len(message) >= 2:
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self._request.ws_close_code = struct.unpack(
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'!H', message[0:2])[0]
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self._request.ws_close_reason = message[2:].decode(
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'utf-8', 'replace')
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self._logger.debug('Initiated flush read')
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self.flushread()
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if self._request.server_terminated:
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self._logger.debug(
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'Received ack for server-initiated closing '
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'handshake')
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return None
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self._logger.debug(
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'Received client-initiated closing handshake')
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self._send_closing_handshake(common.STATUS_NORMAL, '')
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self._logger.debug(
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'Sent ack for client-initiated closing handshake')
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return None
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elif self._original_opcode == common.OPCODE_PING:
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try:
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handler = self._request.on_ping_handler
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if handler:
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handler(self._request, message)
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continue
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except AttributeError, e:
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pass
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self._send_pong(message)
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elif self._original_opcode == common.OPCODE_PONG:
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# TODO(tyoshino): Add ping timeout handling.
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inflight_pings = deque()
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while True:
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try:
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expected_body = self._ping_queue.popleft()
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if expected_body == message:
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# inflight_pings contains pings ignored by the
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# other peer. Just forget them.
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self._logger.debug(
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'Ping %r is acked (%d pings were ignored)',
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expected_body, len(inflight_pings))
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break
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else:
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inflight_pings.append(expected_body)
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except IndexError, e:
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# The received pong was unsolicited pong. Keep the
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# ping queue as is.
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self._ping_queue = inflight_pings
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self._logger.debug('Received a unsolicited pong')
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break
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try:
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handler = self._request.on_pong_handler
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if handler:
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handler(self._request, message)
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continue
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except AttributeError, e:
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pass
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continue
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else:
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raise UnsupportedFrameException(
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'Opcode %d is not supported' % self._original_opcode)
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def _send_closing_handshake(self, code, reason):
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if code >= (1 << 16) or code < 0:
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raise BadOperationException('Status code is out of range')
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encoded_reason = reason.encode('utf-8')
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if len(encoded_reason) + 2 > 125:
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raise BadOperationException(
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'Application data size of close frames must be 125 bytes or '
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'less')
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frame = create_close_frame(
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struct.pack('!H', code) + encoded_reason, self._options.mask_send)
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self._request.server_terminated = True
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self._write(frame)
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def close_connection(self, code=common.STATUS_NORMAL, reason=''):
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"""Closes a WebSocket connection."""
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if self._request.server_terminated:
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self._logger.debug(
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'Requested close_connection but server is already terminated')
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return
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self._send_closing_handshake(code, reason)
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self._logger.debug('Sent server-initiated closing handshake')
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if (code == common.STATUS_GOING_AWAY or
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code == common.STATUS_PROTOCOL_ERROR):
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# It doesn't make sense to wait for a close frame if the reason is
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# protocol error or that the server is going away. For some of
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# other reasons, it might not make sense to wait for a close frame,
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# but it's not clear, yet.
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return
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# TODO(ukai): 2. wait until the /client terminated/ flag has been set,
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# or until a server-defined timeout expires.
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#
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# For now, we expect receiving closing handshake right after sending
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# out closing handshake.
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message = self.receive_message()
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if message is not None:
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raise ConnectionTerminatedException(
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'Didn\'t receive valid ack for closing handshake')
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# TODO: 3. close the WebSocket connection.
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# note: mod_python Connection (mp_conn) doesn't have close method.
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def send_ping(self, body=''):
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if len(body) > 125:
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raise ValueError(
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'Application data size of control frames must be 125 bytes or '
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'less')
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frame = create_ping_frame(body, self._options.mask_send)
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self._write(frame)
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self._ping_queue.append(body)
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def _send_pong(self, body):
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if len(body) > 125:
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raise ValueError(
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'Application data size of control frames must be 125 bytes or '
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'less')
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frame = create_pong_frame(body, self._options.mask_send)
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self._write(frame)
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# vi:sts=4 sw=4 et
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