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29
30
31"""This file provides the opening handshake processor for the WebSocket
32protocol version HyBi 00.
33
34Specification:
35http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-00
36"""
37
38
39# Note: request.connection.write/read are used in this module, even though
40# mod_python document says that they should be used only in connection
41# handlers. Unfortunately, we have no other options. For example,
42# request.write/read are not suitable because they don't allow direct raw bytes
43# writing/reading.
44
45
46import logging
47import re
48import struct
49
50from mod_pywebsocket import common
51from mod_pywebsocket.stream import StreamHixie75
52from mod_pywebsocket import util
53from mod_pywebsocket.handshake._base import HandshakeException
54from mod_pywebsocket.handshake._base import check_request_line
55from mod_pywebsocket.handshake._base import format_header
56from mod_pywebsocket.handshake._base import get_default_port
57from mod_pywebsocket.handshake._base import get_mandatory_header
58from mod_pywebsocket.handshake._base import parse_host_header
59from mod_pywebsocket.handshake._base import validate_mandatory_header
60
61
62_MANDATORY_HEADERS = [
63    # key, expected value or None
64    [common.UPGRADE_HEADER, common.WEBSOCKET_UPGRADE_TYPE_HIXIE75],
65    [common.CONNECTION_HEADER, common.UPGRADE_CONNECTION_TYPE],
66]
67
68
69def _validate_subprotocol(subprotocol):
70    """Checks if characters in subprotocol are in range between U+0020 and
71    U+007E. A value in the Sec-WebSocket-Protocol field need to satisfy this
72    requirement.
73
74    See the Section 4.1. Opening handshake of the spec.
75    """
76
77    if not subprotocol:
78        raise HandshakeException('Invalid subprotocol name: empty')
79
80    # Parameter should be in the range U+0020 to U+007E.
81    for c in subprotocol:
82        if not 0x20 <= ord(c) <= 0x7e:
83            raise HandshakeException(
84                'Illegal character in subprotocol name: %r' % c)
85
86
87def _check_header_lines(request, mandatory_headers):
88    check_request_line(request)
89
90    # The expected field names, and the meaning of their corresponding
91    # values, are as follows.
92    #  |Upgrade| and |Connection|
93    for key, expected_value in mandatory_headers:
94        validate_mandatory_header(request, key, expected_value)
95
96
97def _build_location(request):
98    """Build WebSocket location for request."""
99
100    location_parts = []
101    if request.is_https():
102        location_parts.append(common.WEB_SOCKET_SECURE_SCHEME)
103    else:
104        location_parts.append(common.WEB_SOCKET_SCHEME)
105    location_parts.append('://')
106    host, port = parse_host_header(request)
107    connection_port = request.connection.local_addr[1]
108    if port != connection_port:
109        raise HandshakeException('Header/connection port mismatch: %d/%d' %
110                                 (port, connection_port))
111    location_parts.append(host)
112    if (port != get_default_port(request.is_https())):
113        location_parts.append(':')
114        location_parts.append(str(port))
115    location_parts.append(request.unparsed_uri)
116    return ''.join(location_parts)
117
118
119class Handshaker(object):
120    """Opening handshake processor for the WebSocket protocol version HyBi 00.
121    """
122
123    def __init__(self, request, dispatcher):
124        """Construct an instance.
125
126        Args:
127            request: mod_python request.
128            dispatcher: Dispatcher (dispatch.Dispatcher).
129
130        Handshaker will add attributes such as ws_resource in performing
131        handshake.
132        """
133
134        self._logger = util.get_class_logger(self)
135
136        self._request = request
137        self._dispatcher = dispatcher
138
139    def do_handshake(self):
140        """Perform WebSocket Handshake.
141
142        On _request, we set
143            ws_resource, ws_protocol, ws_location, ws_origin, ws_challenge,
144            ws_challenge_md5: WebSocket handshake information.
145            ws_stream: Frame generation/parsing class.
146            ws_version: Protocol version.
147
148        Raises:
149            HandshakeException: when any error happened in parsing the opening
150                                handshake request.
151        """
152
153        # 5.1 Reading the client's opening handshake.
154        # dispatcher sets it in self._request.
155        _check_header_lines(self._request, _MANDATORY_HEADERS)
156        self._set_resource()
157        self._set_subprotocol()
158        self._set_location()
159        self._set_origin()
160        self._set_challenge_response()
161        self._set_protocol_version()
162
163        self._dispatcher.do_extra_handshake(self._request)
164
165        self._send_handshake()
166
167    def _set_resource(self):
168        self._request.ws_resource = self._request.uri
169
170    def _set_subprotocol(self):
171        # |Sec-WebSocket-Protocol|
172        subprotocol = self._request.headers_in.get(
173            common.SEC_WEBSOCKET_PROTOCOL_HEADER)
174        if subprotocol is not None:
175            _validate_subprotocol(subprotocol)
176        self._request.ws_protocol = subprotocol
177
178    def _set_location(self):
179        # |Host|
180        host = self._request.headers_in.get(common.HOST_HEADER)
181        if host is not None:
182            self._request.ws_location = _build_location(self._request)
183        # TODO(ukai): check host is this host.
184
185    def _set_origin(self):
186        # |Origin|
187        origin = self._request.headers_in.get(common.ORIGIN_HEADER)
188        if origin is not None:
189            self._request.ws_origin = origin
190
191    def _set_protocol_version(self):
192        # |Sec-WebSocket-Draft|
193        draft = self._request.headers_in.get(common.SEC_WEBSOCKET_DRAFT_HEADER)
194        if draft is not None and draft != '0':
195            raise HandshakeException('Illegal value for %s: %s' %
196                                     (common.SEC_WEBSOCKET_DRAFT_HEADER,
197                                      draft))
198
199        self._logger.debug('Protocol version is HyBi 00')
200        self._request.ws_version = common.VERSION_HYBI00
201        self._request.ws_stream = StreamHixie75(self._request, True)
202
203    def _set_challenge_response(self):
204        # 5.2 4-8.
205        self._request.ws_challenge = self._get_challenge()
206        # 5.2 9. let /response/ be the MD5 finterprint of /challenge/
207        self._request.ws_challenge_md5 = util.md5_hash(
208            self._request.ws_challenge).digest()
209        self._logger.debug(
210            'Challenge: %r (%s)',
211            self._request.ws_challenge,
212            util.hexify(self._request.ws_challenge))
213        self._logger.debug(
214            'Challenge response: %r (%s)',
215            self._request.ws_challenge_md5,
216            util.hexify(self._request.ws_challenge_md5))
217
218    def _get_key_value(self, key_field):
219        key_value = get_mandatory_header(self._request, key_field)
220
221        self._logger.debug('%s: %r', key_field, key_value)
222
223        # 5.2 4. let /key-number_n/ be the digits (characters in the range
224        # U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9)) in /key_n/,
225        # interpreted as a base ten integer, ignoring all other characters
226        # in /key_n/.
227        try:
228            key_number = int(re.sub("\\D", "", key_value))
229        except:
230            raise HandshakeException('%s field contains no digit' % key_field)
231        # 5.2 5. let /spaces_n/ be the number of U+0020 SPACE characters
232        # in /key_n/.
233        spaces = re.subn(" ", "", key_value)[1]
234        if spaces == 0:
235            raise HandshakeException('%s field contains no space' % key_field)
236
237        self._logger.debug(
238            '%s: Key-number is %d and number of spaces is %d',
239            key_field, key_number, spaces)
240
241        # 5.2 6. if /key-number_n/ is not an integral multiple of /spaces_n/
242        # then abort the WebSocket connection.
243        if key_number % spaces != 0:
244            raise HandshakeException(
245                '%s: Key-number (%d) is not an integral multiple of spaces '
246                '(%d)' % (key_field, key_number, spaces))
247        # 5.2 7. let /part_n/ be /key-number_n/ divided by /spaces_n/.
248        part = key_number / spaces
249        self._logger.debug('%s: Part is %d', key_field, part)
250        return part
251
252    def _get_challenge(self):
253        # 5.2 4-7.
254        key1 = self._get_key_value(common.SEC_WEBSOCKET_KEY1_HEADER)
255        key2 = self._get_key_value(common.SEC_WEBSOCKET_KEY2_HEADER)
256        # 5.2 8. let /challenge/ be the concatenation of /part_1/,
257        challenge = ''
258        challenge += struct.pack('!I', key1)  # network byteorder int
259        challenge += struct.pack('!I', key2)  # network byteorder int
260        challenge += self._request.connection.read(8)
261        return challenge
262
263    def _send_handshake(self):
264        response = []
265
266        # 5.2 10. send the following line.
267        response.append('HTTP/1.1 101 WebSocket Protocol Handshake\r\n')
268
269        # 5.2 11. send the following fields to the client.
270        response.append(format_header(
271            common.UPGRADE_HEADER, common.WEBSOCKET_UPGRADE_TYPE_HIXIE75))
272        response.append(format_header(
273            common.CONNECTION_HEADER, common.UPGRADE_CONNECTION_TYPE))
274        response.append(format_header(
275            common.SEC_WEBSOCKET_LOCATION_HEADER, self._request.ws_location))
276        response.append(format_header(
277            common.SEC_WEBSOCKET_ORIGIN_HEADER, self._request.ws_origin))
278        if self._request.ws_protocol:
279            response.append(format_header(
280                common.SEC_WEBSOCKET_PROTOCOL_HEADER,
281                self._request.ws_protocol))
282        # 5.2 12. send two bytes 0x0D 0x0A.
283        response.append('\r\n')
284        # 5.2 13. send /response/
285        response.append(self._request.ws_challenge_md5)
286
287        raw_response = ''.join(response)
288        self._request.connection.write(raw_response)
289        self._logger.debug('Sent server\'s opening handshake: %r',
290                           raw_response)
291
292
293# vi:sts=4 sw=4 et
294