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1# Copyright 2009, Google Inc.
2# All rights reserved.
3#
4# Redistribution and use in source and binary forms, with or without
5# modification, are permitted provided that the following conditions are
6# met:
7#
8#     * Redistributions of source code must retain the above copyright
9# notice, this list of conditions and the following disclaimer.
10#     * Redistributions in binary form must reproduce the above
11# copyright notice, this list of conditions and the following disclaimer
12# in the documentation and/or other materials provided with the
13# distribution.
14#     * Neither the name of Google Inc. nor the names of its
15# contributors may be used to endorse or promote products derived from
16# this software without specific prior written permission.
17#
18# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30
31"""Web Socket handshaking.
32
33Note: request.connection.write/read are used in this module, even though
34mod_python document says that they should be used only in connection handlers.
35Unfortunately, we have no other options. For example, request.write/read are
36not suitable because they don't allow direct raw bytes writing/reading.
37"""
38
39
40import re
41
42import util
43
44
45_DEFAULT_WEB_SOCKET_PORT = 80
46_DEFAULT_WEB_SOCKET_SECURE_PORT = 443
47_WEB_SOCKET_SCHEME = 'ws'
48_WEB_SOCKET_SECURE_SCHEME = 'wss'
49
50_MANDATORY_HEADERS = [
51    # key, expected value or None
52    ['Upgrade', 'WebSocket'],
53    ['Connection', 'Upgrade'],
54    ['Host', None],
55    ['Origin', None],
56]
57
58_FIRST_FIVE_LINES = map(re.compile, [
59    r'^GET /[\S]* HTTP/1.1\r\n$',
60    r'^Upgrade: WebSocket\r\n$',
61    r'^Connection: Upgrade\r\n$',
62    r'^Host: [\S]+\r\n$',
63    r'^Origin: [\S]+\r\n$',
64])
65
66_SIXTH_AND_LATER = re.compile(
67    r'^'
68    r'(WebSocket-Protocol: [\x20-\x7e]+\r\n)?'
69    r'(Cookie: [^\r]*\r\n)*'
70    r'(Cookie2: [^\r]*\r\n)?'
71    r'(Cookie: [^\r]*\r\n)*'
72    r'\r\n')
73
74
75def _default_port(is_secure):
76    if is_secure:
77        return _DEFAULT_WEB_SOCKET_SECURE_PORT
78    else:
79        return _DEFAULT_WEB_SOCKET_PORT
80
81
82class HandshakeError(Exception):
83    """Exception in Web Socket Handshake."""
84
85    pass
86
87
88def _validate_protocol(protocol):
89    """Validate WebSocket-Protocol string."""
90
91    if not protocol:
92        raise HandshakeError('Invalid WebSocket-Protocol: empty')
93    for c in protocol:
94        if not 0x20 <= ord(c) <= 0x7e:
95            raise HandshakeError('Illegal character in protocol: %r' % c)
96
97
98class Handshaker(object):
99    """This class performs Web Socket handshake."""
100
101    def __init__(self, request, dispatcher, strict=False):
102        """Construct an instance.
103
104        Args:
105            request: mod_python request.
106            dispatcher: Dispatcher (dispatch.Dispatcher).
107            strict: Strictly check handshake request. Default: False.
108                If True, request.connection must provide get_memorized_lines
109                method.
110
111        Handshaker will add attributes such as ws_resource in performing
112        handshake.
113        """
114
115        self._request = request
116        self._dispatcher = dispatcher
117        self._strict = strict
118
119    def do_handshake(self):
120        """Perform Web Socket Handshake."""
121
122        self._check_header_lines()
123        self._set_resource()
124        self._set_origin()
125        self._set_location()
126        self._set_protocol()
127        self._dispatcher.do_extra_handshake(self._request)
128        self._send_handshake()
129
130    def _set_resource(self):
131        self._request.ws_resource = self._request.uri
132
133    def _set_origin(self):
134        self._request.ws_origin = self._request.headers_in['Origin']
135
136    def _set_location(self):
137        location_parts = []
138        if self._request.is_https():
139            location_parts.append(_WEB_SOCKET_SECURE_SCHEME)
140        else:
141            location_parts.append(_WEB_SOCKET_SCHEME)
142        location_parts.append('://')
143        host, port = self._parse_host_header()
144        connection_port = self._request.connection.local_addr[1]
145        if port != connection_port:
146            raise HandshakeError('Header/connection port mismatch: %d/%d' %
147                                 (port, connection_port))
148        location_parts.append(host)
149        if (port != _default_port(self._request.is_https())):
150            location_parts.append(':')
151            location_parts.append(str(port))
152        location_parts.append(self._request.uri)
153        self._request.ws_location = ''.join(location_parts)
154
155    def _parse_host_header(self):
156        fields = self._request.headers_in['Host'].split(':', 1)
157        if len(fields) == 1:
158            return fields[0], _default_port(self._request.is_https())
159        try:
160            return fields[0], int(fields[1])
161        except ValueError, e:
162            raise HandshakeError('Invalid port number format: %r' % e)
163
164    def _set_protocol(self):
165        protocol = self._request.headers_in.get('WebSocket-Protocol')
166        if protocol is not None:
167            _validate_protocol(protocol)
168        self._request.ws_protocol = protocol
169
170    def _send_handshake(self):
171        self._request.connection.write(
172                'HTTP/1.1 101 Web Socket Protocol Handshake\r\n')
173        self._request.connection.write('Upgrade: WebSocket\r\n')
174        self._request.connection.write('Connection: Upgrade\r\n')
175        self._request.connection.write('WebSocket-Origin: ')
176        self._request.connection.write(self._request.ws_origin)
177        self._request.connection.write('\r\n')
178        self._request.connection.write('WebSocket-Location: ')
179        self._request.connection.write(self._request.ws_location)
180        self._request.connection.write('\r\n')
181        if self._request.ws_protocol:
182            self._request.connection.write('WebSocket-Protocol: ')
183            self._request.connection.write(self._request.ws_protocol)
184            self._request.connection.write('\r\n')
185        self._request.connection.write('\r\n')
186
187    def _check_header_lines(self):
188        for key, expected_value in _MANDATORY_HEADERS:
189            actual_value = self._request.headers_in.get(key)
190            if not actual_value:
191                raise HandshakeError('Header %s is not defined' % key)
192            if expected_value:
193                if actual_value != expected_value:
194                    raise HandshakeError('Illegal value for header %s: %s' %
195                                         (key, actual_value))
196        if self._strict:
197            try:
198                lines = self._request.connection.get_memorized_lines()
199            except AttributeError, e:
200                util.prepend_message_to_exception(
201                    'Strict handshake is specified but the connection '
202                    'doesn\'t provide get_memorized_lines()', e)
203                raise
204            self._check_first_lines(lines)
205
206    def _check_first_lines(self, lines):
207        if len(lines) < len(_FIRST_FIVE_LINES):
208            raise HandshakeError('Too few header lines: %d' % len(lines))
209        for line, regexp in zip(lines, _FIRST_FIVE_LINES):
210            if not regexp.search(line):
211                raise HandshakeError('Unexpected header: %r doesn\'t match %r'
212                                     % (line, regexp.pattern))
213        sixth_and_later = ''.join(lines[5:])
214        if not _SIXTH_AND_LATER.search(sixth_and_later):
215            raise HandshakeError('Unexpected header: %r doesn\'t match %r'
216                                 % (sixth_and_later,
217                                    _SIXTH_AND_LATER.pattern))
218
219
220# vi:sts=4 sw=4 et
221