399 lines
14 KiB
Python
399 lines
14 KiB
Python
# Copyright 2012, 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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"""Common functions and exceptions used by WebSocket opening handshake
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processors.
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"""
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from __future__ import absolute_import
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from mod_pywebsocket import common
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from mod_pywebsocket import http_header_util
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from mod_pywebsocket.extensions import get_extension_processor
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from mod_pywebsocket.stream import StreamOptions
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from mod_pywebsocket.stream import Stream
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from mod_pywebsocket import util
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from six.moves import map
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from six.moves import range
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# Defining aliases for values used frequently.
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_VERSION_LATEST = common.VERSION_HYBI_LATEST
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_VERSION_LATEST_STRING = str(_VERSION_LATEST)
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_SUPPORTED_VERSIONS = [
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_VERSION_LATEST,
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]
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class AbortedByUserException(Exception):
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"""Exception for aborting a connection intentionally.
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If this exception is raised in do_extra_handshake handler, the connection
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will be abandoned. No other WebSocket or HTTP(S) handler will be invoked.
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If this exception is raised in transfer_data_handler, the connection will
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be closed without closing handshake. No other WebSocket or HTTP(S) handler
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will be invoked.
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"""
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pass
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class HandshakeException(Exception):
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"""This exception will be raised when an error occurred while processing
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WebSocket initial handshake.
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"""
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def __init__(self, name, status=None):
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super(HandshakeException, self).__init__(name)
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self.status = status
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class VersionException(Exception):
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"""This exception will be raised when a version of client request does not
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match with version the server supports.
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"""
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def __init__(self, name, supported_versions=''):
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"""Construct an instance.
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Args:
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supported_version: a str object to show supported hybi versions.
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(e.g. '13')
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"""
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super(VersionException, self).__init__(name)
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self.supported_versions = supported_versions
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def get_default_port(is_secure):
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if is_secure:
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return common.DEFAULT_WEB_SOCKET_SECURE_PORT
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else:
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return common.DEFAULT_WEB_SOCKET_PORT
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def validate_subprotocol(subprotocol):
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"""Validate a value in the Sec-WebSocket-Protocol field.
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See the Section 4.1., 4.2.2., and 4.3. of RFC 6455.
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"""
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if not subprotocol:
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raise HandshakeException('Invalid subprotocol name: empty')
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# Parameter should be encoded HTTP token.
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state = http_header_util.ParsingState(subprotocol)
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token = http_header_util.consume_token(state)
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rest = http_header_util.peek(state)
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# If |rest| is not None, |subprotocol| is not one token or invalid. If
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# |rest| is None, |token| must not be None because |subprotocol| is
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# concatenation of |token| and |rest| and is not None.
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if rest is not None:
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raise HandshakeException('Invalid non-token string in subprotocol '
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'name: %r' % rest)
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def parse_host_header(request):
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fields = request.headers_in[common.HOST_HEADER].split(':', 1)
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if len(fields) == 1:
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return fields[0], get_default_port(request.is_https())
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try:
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return fields[0], int(fields[1])
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except ValueError as e:
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raise HandshakeException('Invalid port number format: %r' % e)
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def get_mandatory_header(request, key):
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value = request.headers_in.get(key)
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if value is None:
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raise HandshakeException('Header %s is not defined' % key)
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return value
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def validate_mandatory_header(request, key, expected_value, fail_status=None):
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value = get_mandatory_header(request, key)
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if value.lower() != expected_value.lower():
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raise HandshakeException(
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'Expected %r for header %s but found %r (case-insensitive)' %
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(expected_value, key, value),
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status=fail_status)
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def parse_token_list(data):
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"""Parses a header value which follows 1#token and returns parsed elements
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as a list of strings.
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Leading LWSes must be trimmed.
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"""
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state = http_header_util.ParsingState(data)
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token_list = []
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while True:
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token = http_header_util.consume_token(state)
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if token is not None:
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token_list.append(token)
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http_header_util.consume_lwses(state)
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if http_header_util.peek(state) is None:
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break
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if not http_header_util.consume_string(state, ','):
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raise HandshakeException('Expected a comma but found %r' %
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http_header_util.peek(state))
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http_header_util.consume_lwses(state)
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if len(token_list) == 0:
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raise HandshakeException('No valid token found')
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return token_list
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class HandshakerBase(object):
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def __init__(self, request, dispatcher):
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self._logger = util.get_class_logger(self)
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self._request = request
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self._dispatcher = dispatcher
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""" subclasses must implement the five following methods """
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def _protocol_rfc(self):
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""" Return the name of the RFC that the handshake class is implementing.
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"""
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raise AssertionError("subclasses should implement this method")
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def _transform_header(self, header):
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"""
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:param header: header name
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transform the header name if needed. For example, HTTP/2 subclass will
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return the name of the header in lower case.
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"""
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raise AssertionError("subclasses should implement this method")
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def _validate_request(self):
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""" validate that all the mandatory fields are set """
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raise AssertionError("subclasses should implement this method")
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def _set_accept(self):
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""" Computes accept value based on Sec-WebSocket-Accept if needed. """
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raise AssertionError("subclasses should implement this method")
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def _send_handshake(self):
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""" Prepare and send the response after it has been parsed and processed.
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"""
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raise AssertionError("subclasses should implement this method")
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def do_handshake(self):
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self._request.ws_close_code = None
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self._request.ws_close_reason = None
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# Parsing.
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self._validate_request()
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self._request.ws_resource = self._request.uri
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self._request.ws_version = self._check_version()
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try:
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self._get_origin()
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self._set_protocol()
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self._parse_extensions()
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self._set_accept()
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self._logger.debug('Protocol version is ' + self._protocol_rfc())
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# Setup extension processors.
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self._request.ws_extension_processors = self._get_extension_processors_requested(
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)
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# List of extra headers. The extra handshake handler may add header
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# data as name/value pairs to this list and pywebsocket appends
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# them to the WebSocket handshake.
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self._request.extra_headers = []
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# Extra handshake handler may modify/remove processors.
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self._dispatcher.do_extra_handshake(self._request)
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stream_options = StreamOptions()
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self._process_extensions(stream_options)
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self._request.ws_stream = Stream(self._request, stream_options)
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if self._request.ws_requested_protocols is not None:
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if self._request.ws_protocol is None:
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raise HandshakeException(
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'do_extra_handshake must choose one subprotocol from '
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'ws_requested_protocols and set it to ws_protocol')
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validate_subprotocol(self._request.ws_protocol)
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self._logger.debug('Subprotocol accepted: %r',
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self._request.ws_protocol)
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else:
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if self._request.ws_protocol is not None:
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raise HandshakeException(
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'ws_protocol must be None when the client didn\'t '
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'request any subprotocol')
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self._send_handshake()
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except HandshakeException as e:
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if not e.status:
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# Fallback to 400 bad request by default.
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e.status = common.HTTP_STATUS_BAD_REQUEST
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raise e
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def _check_version(self):
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sec_websocket_version_header = self._transform_header(
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common.SEC_WEBSOCKET_VERSION_HEADER)
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version = get_mandatory_header(self._request,
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sec_websocket_version_header)
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if version == _VERSION_LATEST_STRING:
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return _VERSION_LATEST
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if version.find(',') >= 0:
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raise HandshakeException(
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'Multiple versions (%r) are not allowed for header %s' %
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(version, sec_websocket_version_header),
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status=common.HTTP_STATUS_BAD_REQUEST)
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raise VersionException('Unsupported version %r for header %s' %
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(version, sec_websocket_version_header),
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supported_versions=', '.join(
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map(str, _SUPPORTED_VERSIONS)))
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def _get_origin(self):
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origin_header = self._transform_header(common.ORIGIN_HEADER)
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origin = self._request.headers_in.get(origin_header)
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if origin is None:
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self._logger.debug('Client request does not have origin header')
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self._request.ws_origin = origin
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def _set_protocol(self):
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self._request.ws_protocol = None
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# MOZILLA
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self._request.sts = None
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# /MOZILLA
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sec_websocket_protocol_header = self._transform_header(
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common.SEC_WEBSOCKET_PROTOCOL_HEADER)
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protocol_header = self._request.headers_in.get(
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sec_websocket_protocol_header)
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if protocol_header is None:
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self._request.ws_requested_protocols = None
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return
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self._request.ws_requested_protocols = parse_token_list(
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protocol_header)
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self._logger.debug('Subprotocols requested: %r',
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self._request.ws_requested_protocols)
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def _parse_extensions(self):
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sec_websocket_extensions_header = self._transform_header(
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common.SEC_WEBSOCKET_EXTENSIONS_HEADER)
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extensions_header = self._request.headers_in.get(
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sec_websocket_extensions_header)
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if not extensions_header:
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self._request.ws_requested_extensions = None
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return
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try:
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self._request.ws_requested_extensions = common.parse_extensions(
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extensions_header)
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except common.ExtensionParsingException as e:
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raise HandshakeException(
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'Failed to parse sec-websocket-extensions header: %r' % e)
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self._logger.debug(
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'Extensions requested: %r',
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list(
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map(common.ExtensionParameter.name,
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self._request.ws_requested_extensions)))
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def _get_extension_processors_requested(self):
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processors = []
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if self._request.ws_requested_extensions is not None:
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for extension_request in self._request.ws_requested_extensions:
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processor = get_extension_processor(extension_request)
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# Unknown extension requests are just ignored.
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if processor is not None:
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processors.append(processor)
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return processors
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def _process_extensions(self, stream_options):
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processors = [
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processor for processor in self._request.ws_extension_processors
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if processor is not None
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]
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# Ask each processor if there are extensions on the request which
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# cannot co-exist. When processor decided other processors cannot
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# co-exist with it, the processor marks them (or itself) as
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# "inactive". The first extension processor has the right to
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# make the final call.
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for processor in reversed(processors):
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if processor.is_active():
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processor.check_consistency_with_other_processors(processors)
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processors = [
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processor for processor in processors if processor.is_active()
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]
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accepted_extensions = []
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for index, processor in enumerate(processors):
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if not processor.is_active():
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continue
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extension_response = processor.get_extension_response()
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if extension_response is None:
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# Rejected.
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continue
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accepted_extensions.append(extension_response)
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processor.setup_stream_options(stream_options)
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# Inactivate all of the following compression extensions.
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for j in range(index + 1, len(processors)):
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processors[j].set_active(False)
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if len(accepted_extensions) > 0:
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self._request.ws_extensions = accepted_extensions
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self._logger.debug(
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'Extensions accepted: %r',
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list(map(common.ExtensionParameter.name, accepted_extensions)))
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else:
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self._request.ws_extensions = None
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# vi:sts=4 sw=4 et
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