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# Copyright 2012, Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# 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
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""This file provides the opening handshake processor for the WebSocket
protocol (RFC 6455).
Specification:
http://tools.ietf.org/html/rfc6455
"""
from __future__ import absolute_import
import base64
import re
from hashlib import sha1
from mod_pywebsocket import common
from mod_pywebsocket.handshake.base import get_mandatory_header
from mod_pywebsocket.handshake.base import HandshakeException
from mod_pywebsocket.handshake.base import parse_token_list
from mod_pywebsocket.handshake.base import validate_mandatory_header
from mod_pywebsocket.handshake.base import HandshakerBase
from mod_pywebsocket import util
# Used to validate the value in the Sec-WebSocket-Key header strictly. RFC 4648
# disallows non-zero padding, so the character right before == must be any of
# A, Q, g and w.
_SEC_WEBSOCKET_KEY_REGEX = re.compile('^[+/0-9A-Za-z]{21}[AQgw]==$')
def check_request_line(request):
# 5.1 1. The three character UTF-8 string "GET".
# 5.1 2. A UTF-8-encoded U+0020 SPACE character (0x20 byte).
if request.method != u'GET':
raise HandshakeException('Method is not GET: %r' % request.method)
if request.protocol != u'HTTP/1.1':
raise HandshakeException('Version is not HTTP/1.1: %r' %
request.protocol)
def compute_accept(key):
"""Computes value for the Sec-WebSocket-Accept header from value of the
Sec-WebSocket-Key header.
"""
accept_binary = sha1(key + common.WEBSOCKET_ACCEPT_UUID).digest()
accept = base64.b64encode(accept_binary)
return accept
def compute_accept_from_unicode(unicode_key):
"""A wrapper function for compute_accept which takes a unicode string as an
argument, and encodes it to byte string. It then passes it on to
compute_accept.
"""
key = unicode_key.encode('UTF-8')
return compute_accept(key)
def format_header(name, value):
return u'%s: %s\r\n' % (name, value)
class Handshaker(HandshakerBase):
"""Opening handshake processor for the WebSocket protocol (RFC 6455)."""
def __init__(self, request, dispatcher):
"""Construct an instance.
Args:
request: mod_python request.
dispatcher: Dispatcher (dispatch.Dispatcher).
Handshaker will add attributes such as ws_resource during handshake.
"""
super(Handshaker, self).__init__(request, dispatcher)
def _transform_header(self, header):
return header
def _protocol_rfc(self):
return 'RFC 6455'
def _validate_connection_header(self):
connection = get_mandatory_header(self._request,
common.CONNECTION_HEADER)
try:
connection_tokens = parse_token_list(connection)
except HandshakeException as e:
raise HandshakeException('Failed to parse %s: %s' %
(common.CONNECTION_HEADER, e))
connection_is_valid = False
for token in connection_tokens:
if token.lower() == common.UPGRADE_CONNECTION_TYPE.lower():
connection_is_valid = True
break
if not connection_is_valid:
raise HandshakeException(
'%s header doesn\'t contain "%s"' %
(common.CONNECTION_HEADER, common.UPGRADE_CONNECTION_TYPE))
def _validate_request(self):
check_request_line(self._request)
validate_mandatory_header(self._request, common.UPGRADE_HEADER,
common.WEBSOCKET_UPGRADE_TYPE)
self._validate_connection_header()
unused_host = get_mandatory_header(self._request, common.HOST_HEADER)
def _set_accept(self):
# Key validation, response generation.
key = self._get_key()
accept = compute_accept(key)
self._logger.debug('%s: %r (%s)', common.SEC_WEBSOCKET_ACCEPT_HEADER,
accept, util.hexify(base64.b64decode(accept)))
self._request._accept = accept
def _validate_key(self, key):
if key.find(',') >= 0:
raise HandshakeException('Request has multiple %s header lines or '
'contains illegal character \',\': %r' %
(common.SEC_WEBSOCKET_KEY_HEADER, key))
# Validate
key_is_valid = False
try:
# Validate key by quick regex match before parsing by base64
# module. Because base64 module skips invalid characters, we have
# to do this in advance to make this server strictly reject illegal
# keys.
if _SEC_WEBSOCKET_KEY_REGEX.match(key):
decoded_key = base64.b64decode(key)
if len(decoded_key) == 16:
key_is_valid = True
except TypeError as e:
pass
if not key_is_valid:
raise HandshakeException('Illegal value for header %s: %r' %
(common.SEC_WEBSOCKET_KEY_HEADER, key))
return decoded_key
def _get_key(self):
key = get_mandatory_header(self._request,
common.SEC_WEBSOCKET_KEY_HEADER)
decoded_key = self._validate_key(key)
self._logger.debug('%s: %r (%s)', common.SEC_WEBSOCKET_KEY_HEADER, key,
util.hexify(decoded_key))
return key.encode('UTF-8')
def _create_handshake_response(self, accept):
response = []
response.append(u'HTTP/1.1 101 Switching Protocols\r\n')
# WebSocket headers
response.append(
format_header(common.UPGRADE_HEADER,
common.WEBSOCKET_UPGRADE_TYPE))
response.append(
format_header(common.CONNECTION_HEADER,
common.UPGRADE_CONNECTION_TYPE))
response.append(
format_header(common.SEC_WEBSOCKET_ACCEPT_HEADER,
accept.decode('UTF-8')))
if self._request.ws_protocol is not None:
response.append(
format_header(common.SEC_WEBSOCKET_PROTOCOL_HEADER,
self._request.ws_protocol))
if (self._request.ws_extensions is not None
and len(self._request.ws_extensions) != 0):
response.append(
format_header(
common.SEC_WEBSOCKET_EXTENSIONS_HEADER,
common.format_extensions(self._request.ws_extensions)))
# Headers not specific for WebSocket
for name, value in self._request.extra_headers:
response.append(format_header(name, value))
response.append(u'\r\n')
return u''.join(response)
def _send_handshake(self):
raw_response = self._create_handshake_response(self._request._accept)
self._request.connection.write(raw_response.encode('UTF-8'))
self._logger.debug('Sent server\'s opening handshake: %r',
raw_response)
# vi:sts=4 sw=4 et
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