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"""Web Socket handshaking.
Note: request.connection.write/read are used in this module, even though
mod_python document says that they should be used only in connection handlers.
Unfortunately, we have no other options. For example, request.write/read are
not suitable because they don't allow direct raw bytes writing/reading.
"""
import re
import util
_DEFAULT_WEB_SOCKET_PORT = 80
_DEFAULT_WEB_SOCKET_SECURE_PORT = 443
_WEB_SOCKET_SCHEME = 'ws'
_WEB_SOCKET_SECURE_SCHEME = 'wss'
_MANDATORY_HEADERS = [
# key, expected value or None
['Upgrade', 'WebSocket'],
['Connection', 'Upgrade'],
['Host', None],
['Origin', None],
]
_FIRST_FIVE_LINES = map(re.compile, [
r'^GET /[\S]* HTTP/1.1\r\n$',
r'^Upgrade: WebSocket\r\n$',
r'^Connection: Upgrade\r\n$',
r'^Host: [\S]+\r\n$',
r'^Origin: [\S]+\r\n$',
])
_SIXTH_AND_LATER = re.compile(
r'^'
r'(WebSocket-Protocol: [\x20-\x7e]+\r\n)?'
r'(Cookie: [^\r]*\r\n)*'
r'(Cookie2: [^\r]*\r\n)?'
r'(Cookie: [^\r]*\r\n)*'
r'\r\n')
def _default_port(is_secure):
if is_secure:
return _DEFAULT_WEB_SOCKET_SECURE_PORT
else:
return _DEFAULT_WEB_SOCKET_PORT
class HandshakeError(Exception):
"""Exception in Web Socket Handshake."""
pass
def _validate_protocol(protocol):
"""Validate WebSocket-Protocol string."""
if not protocol:
raise HandshakeError('Invalid WebSocket-Protocol: empty')
for c in protocol:
if not 0x20 <= ord(c) <= 0x7e:
raise HandshakeError('Illegal character in protocol: %r' % c)
class Handshaker(object):
"""This class performs Web Socket handshake."""
def __init__(self, request, dispatcher, strict=False):
"""Construct an instance.
Args:
request: mod_python request.
dispatcher: Dispatcher (dispatch.Dispatcher).
strict: Strictly check handshake request. Default: False.
If True, request.connection must provide get_memorized_lines
method.
Handshaker will add attributes such as ws_resource in performing
handshake.
"""
self._request = request
self._dispatcher = dispatcher
self._strict = strict
def do_handshake(self):
"""Perform Web Socket Handshake."""
self._check_header_lines()
self._set_resource()
self._set_origin()
self._set_location()
self._set_protocol()
self._dispatcher.do_extra_handshake(self._request)
self._send_handshake()
def _set_resource(self):
self._request.ws_resource = self._request.uri
def _set_origin(self):
self._request.ws_origin = self._request.headers_in['Origin']
def _set_location(self):
location_parts = []
if self._request.is_https():
location_parts.append(_WEB_SOCKET_SECURE_SCHEME)
else:
location_parts.append(_WEB_SOCKET_SCHEME)
location_parts.append('://')
host, port = self._parse_host_header()
connection_port = self._request.connection.local_addr[1]
if port != connection_port:
raise HandshakeError('Header/connection port mismatch: %d/%d' %
(port, connection_port))
location_parts.append(host)
if (port != _default_port(self._request.is_https())):
location_parts.append(':')
location_parts.append(str(port))
location_parts.append(self._request.uri)
self._request.ws_location = ''.join(location_parts)
def _parse_host_header(self):
fields = self._request.headers_in['Host'].split(':', 1)
if len(fields) == 1:
return fields[0], _default_port(self._request.is_https())
try:
return fields[0], int(fields[1])
except ValueError, e:
raise HandshakeError('Invalid port number format: %r' % e)
def _set_protocol(self):
protocol = self._request.headers_in.get('WebSocket-Protocol')
if protocol is not None:
_validate_protocol(protocol)
self._request.ws_protocol = protocol
def _send_handshake(self):
self._request.connection.write(
'HTTP/1.1 101 Web Socket Protocol Handshake\r\n')
self._request.connection.write('Upgrade: WebSocket\r\n')
self._request.connection.write('Connection: Upgrade\r\n')
self._request.connection.write('WebSocket-Origin: ')
self._request.connection.write(self._request.ws_origin)
self._request.connection.write('\r\n')
self._request.connection.write('WebSocket-Location: ')
self._request.connection.write(self._request.ws_location)
self._request.connection.write('\r\n')
if self._request.ws_protocol:
self._request.connection.write('WebSocket-Protocol: ')
self._request.connection.write(self._request.ws_protocol)
self._request.connection.write('\r\n')
self._request.connection.write('\r\n')
def _check_header_lines(self):
for key, expected_value in _MANDATORY_HEADERS:
actual_value = self._request.headers_in.get(key)
if not actual_value:
raise HandshakeError('Header %s is not defined' % key)
if expected_value:
if actual_value != expected_value:
raise HandshakeError('Illegal value for header %s: %s' %
(key, actual_value))
if self._strict:
try:
lines = self._request.connection.get_memorized_lines()
except AttributeError, e:
util.prepend_message_to_exception(
'Strict handshake is specified but the connection '
'doesn\'t provide get_memorized_lines()', e)
raise
self._check_first_lines(lines)
def _check_first_lines(self, lines):
if len(lines) < len(_FIRST_FIVE_LINES):
raise HandshakeError('Too few header lines: %d' % len(lines))
for line, regexp in zip(lines, _FIRST_FIVE_LINES):
if not regexp.search(line):
raise HandshakeError('Unexpected header: %r doesn\'t match %r'
% (line, regexp.pattern))
sixth_and_later = ''.join(lines[5:])
if not _SIXTH_AND_LATER.search(sixth_and_later):
raise HandshakeError('Unexpected header: %r doesn\'t match %r'
% (sixth_and_later,
_SIXTH_AND_LATER.pattern))
# vi:sts=4 sw=4 et