import base64 import gzip import importlib import io import logging import secrets import urllib import zlib from . import exceptions from . import packet from . import payload from . import socket default_logger = logging.getLogger('engineio.server') class Server(object): """An Engine.IO server. This class implements a fully compliant Engine.IO web server with support for websocket and long-polling transports. :param async_mode: The asynchronous model to use. See the Deployment section in the documentation for a description of the available options. Valid async modes are "threading", "eventlet", "gevent" and "gevent_uwsgi". If this argument is not given, "eventlet" is tried first, then "gevent_uwsgi", then "gevent", and finally "threading". The first async mode that has all its dependencies installed is the one that is chosen. :param ping_interval: The interval in seconds at which the server pings the client. The default is 25 seconds. For advanced control, a two element tuple can be given, where the first number is the ping interval and the second is a grace period added by the server. :param ping_timeout: The time in seconds that the client waits for the server to respond before disconnecting. The default is 5 seconds. :param max_http_buffer_size: The maximum size of a message when using the polling transport. The default is 1,000,000 bytes. :param allow_upgrades: Whether to allow transport upgrades or not. The default is ``True``. :param http_compression: Whether to compress packages when using the polling transport. The default is ``True``. :param compression_threshold: Only compress messages when their byte size is greater than this value. The default is 1024 bytes. :param cookie: If set to a string, it is the name of the HTTP cookie the server sends back tot he client containing the client session id. If set to a dictionary, the ``'name'`` key contains the cookie name and other keys define cookie attributes, where the value of each attribute can be a string, a callable with no arguments, or a boolean. If set to ``None`` (the default), a cookie is not sent to the client. :param cors_allowed_origins: Origin or list of origins that are allowed to connect to this server. Only the same origin is allowed by default. Set this argument to ``'*'`` to allow all origins, or to ``[]`` to disable CORS handling. :param cors_credentials: Whether credentials (cookies, authentication) are allowed in requests to this server. The default is ``True``. :param logger: To enable logging set to ``True`` or pass a logger object to use. To disable logging set to ``False``. The default is ``False``. Note that fatal errors are logged even when ``logger`` is ``False``. :param json: An alternative json module to use for encoding and decoding packets. Custom json modules must have ``dumps`` and ``loads`` functions that are compatible with the standard library versions. :param async_handlers: If set to ``True``, run message event handlers in non-blocking threads. To run handlers synchronously, set to ``False``. The default is ``True``. :param monitor_clients: If set to ``True``, a background task will ensure inactive clients are closed. Set to ``False`` to disable the monitoring task (not recommended). The default is ``True``. :param kwargs: Reserved for future extensions, any additional parameters given as keyword arguments will be silently ignored. """ compression_methods = ['gzip', 'deflate'] event_names = ['connect', 'disconnect', 'message'] _default_monitor_clients = True sequence_number = 0 def __init__(self, async_mode=None, ping_interval=25, ping_timeout=5, max_http_buffer_size=1000000, allow_upgrades=True, http_compression=True, compression_threshold=1024, cookie=None, cors_allowed_origins=None, cors_credentials=True, logger=False, json=None, async_handlers=True, monitor_clients=None, **kwargs): self.ping_timeout = ping_timeout if isinstance(ping_interval, tuple): self.ping_interval = ping_interval[0] self.ping_interval_grace_period = ping_interval[1] else: self.ping_interval = ping_interval self.ping_interval_grace_period = 0 self.max_http_buffer_size = max_http_buffer_size self.allow_upgrades = allow_upgrades self.http_compression = http_compression self.compression_threshold = compression_threshold self.cookie = cookie self.cors_allowed_origins = cors_allowed_origins self.cors_credentials = cors_credentials self.async_handlers = async_handlers self.sockets = {} self.handlers = {} self.log_message_keys = set() self.start_service_task = monitor_clients \ if monitor_clients is not None else self._default_monitor_clients if json is not None: packet.Packet.json = json if not isinstance(logger, bool): self.logger = logger else: self.logger = default_logger if self.logger.level == logging.NOTSET: if logger: self.logger.setLevel(logging.INFO) else: self.logger.setLevel(logging.ERROR) self.logger.addHandler(logging.StreamHandler()) modes = self.async_modes() if async_mode is not None: modes = [async_mode] if async_mode in modes else [] self._async = None self.async_mode = None for mode in modes: try: self._async = importlib.import_module( 'engineio.async_drivers.' + mode)._async asyncio_based = self._async['asyncio'] \ if 'asyncio' in self._async else False if asyncio_based != self.is_asyncio_based(): continue # pragma: no cover self.async_mode = mode break except ImportError: pass if self.async_mode is None: raise ValueError('Invalid async_mode specified') if self.is_asyncio_based() and \ ('asyncio' not in self._async or not self._async['asyncio']): # pragma: no cover raise ValueError('The selected async_mode is not asyncio ' 'compatible') if not self.is_asyncio_based() and 'asyncio' in self._async and \ self._async['asyncio']: # pragma: no cover raise ValueError('The selected async_mode requires asyncio and ' 'must use the AsyncServer class') self.logger.info('Server initialized for %s.', self.async_mode) def is_asyncio_based(self): return False def async_modes(self): return ['eventlet', 'gevent_uwsgi', 'gevent', 'threading'] def on(self, event, handler=None): """Register an event handler. :param event: The event name. Can be ``'connect'``, ``'message'`` or ``'disconnect'``. :param handler: The function that should be invoked to handle the event. When this parameter is not given, the method acts as a decorator for the handler function. Example usage:: # as a decorator: @eio.on('connect') def connect_handler(sid, environ): print('Connection request') if environ['REMOTE_ADDR'] in blacklisted: return False # reject # as a method: def message_handler(sid, msg): print('Received message: ', msg) eio.send(sid, 'response') eio.on('message', message_handler) The handler function receives the ``sid`` (session ID) for the client as first argument. The ``'connect'`` event handler receives the WSGI environment as a second argument, and can return ``False`` to reject the connection. The ``'message'`` handler receives the message payload as a second argument. The ``'disconnect'`` handler does not take a second argument. """ if event not in self.event_names: raise ValueError('Invalid event') def set_handler(handler): self.handlers[event] = handler return handler if handler is None: return set_handler set_handler(handler) def send(self, sid, data): """Send a message to a client. :param sid: The session id of the recipient client. :param data: The data to send to the client. Data can be of type ``str``, ``bytes``, ``list`` or ``dict``. If a ``list`` or ``dict``, the data will be serialized as JSON. """ try: socket = self._get_socket(sid) except KeyError: # the socket is not available self.logger.warning('Cannot send to sid %s', sid) return socket.send(packet.Packet(packet.MESSAGE, data=data)) def get_session(self, sid): """Return the user session for a client. :param sid: The session id of the client. The return value is a dictionary. Modifications made to this dictionary are not guaranteed to be preserved unless ``save_session()`` is called, or when the ``session`` context manager is used. """ socket = self._get_socket(sid) return socket.session def save_session(self, sid, session): """Store the user session for a client. :param sid: The session id of the client. :param session: The session dictionary. """ socket = self._get_socket(sid) socket.session = session def session(self, sid): """Return the user session for a client with context manager syntax. :param sid: The session id of the client. This is a context manager that returns the user session dictionary for the client. Any changes that are made to this dictionary inside the context manager block are saved back to the session. Example usage:: @eio.on('connect') def on_connect(sid, environ): username = authenticate_user(environ) if not username: return False with eio.session(sid) as session: session['username'] = username @eio.on('message') def on_message(sid, msg): with eio.session(sid) as session: print('received message from ', session['username']) """ class _session_context_manager(object): def __init__(self, server, sid): self.server = server self.sid = sid self.session = None def __enter__(self): self.session = self.server.get_session(sid) return self.session def __exit__(self, *args): self.server.save_session(sid, self.session) return _session_context_manager(self, sid) def disconnect(self, sid=None): """Disconnect a client. :param sid: The session id of the client to close. If this parameter is not given, then all clients are closed. """ if sid is not None: try: socket = self._get_socket(sid) except KeyError: # pragma: no cover # the socket was already closed or gone pass else: socket.close() if sid in self.sockets: # pragma: no cover del self.sockets[sid] else: for client in self.sockets.values(): client.close() self.sockets = {} def transport(self, sid): """Return the name of the transport used by the client. The two possible values returned by this function are ``'polling'`` and ``'websocket'``. :param sid: The session of the client. """ return 'websocket' if self._get_socket(sid).upgraded else 'polling' def handle_request(self, environ, start_response): """Handle an HTTP request from the client. This is the entry point of the Engine.IO application, using the same interface as a WSGI application. For the typical usage, this function is invoked by the :class:`Middleware` instance, but it can be invoked directly when the middleware is not used. :param environ: The WSGI environment. :param start_response: The WSGI ``start_response`` function. This function returns the HTTP response body to deliver to the client as a byte sequence. """ if self.cors_allowed_origins != []: # Validate the origin header if present # This is important for WebSocket more than for HTTP, since # browsers only apply CORS controls to HTTP. origin = environ.get('HTTP_ORIGIN') if origin: allowed_origins = self._cors_allowed_origins(environ) if allowed_origins is not None and origin not in \ allowed_origins: self._log_error_once( origin + ' is not an accepted origin.', 'bad-origin') r = self._bad_request( origin + ' is not an accepted origin.') start_response(r['status'], r['headers']) return [r['response']] method = environ['REQUEST_METHOD'] query = urllib.parse.parse_qs(environ.get('QUERY_STRING', '')) jsonp = False jsonp_index = None # make sure the client speaks a compatible Engine.IO version sid = query['sid'][0] if 'sid' in query else None if sid is None and query.get('EIO') != ['4']: self._log_error_once( 'The client is using an unsupported version of the Socket.IO ' 'or Engine.IO protocols', 'bad-version') r = self._bad_request( 'The client is using an unsupported version of the Socket.IO ' 'or Engine.IO protocols') start_response(r['status'], r['headers']) return [r['response']] if 'j' in query: jsonp = True try: jsonp_index = int(query['j'][0]) except (ValueError, KeyError, IndexError): # Invalid JSONP index number pass if jsonp and jsonp_index is None: self._log_error_once('Invalid JSONP index number', 'bad-jsonp-index') r = self._bad_request('Invalid JSONP index number') elif method == 'GET': if sid is None: transport = query.get('transport', ['polling'])[0] # transport must be one of 'polling' or 'websocket'. # if 'websocket', the HTTP_UPGRADE header must match. upgrade_header = environ.get('HTTP_UPGRADE').lower() \ if 'HTTP_UPGRADE' in environ else None if transport == 'polling' \ or transport == upgrade_header == 'websocket': r = self._handle_connect(environ, start_response, transport, jsonp_index) else: self._log_error_once('Invalid transport ' + transport, 'bad-transport') r = self._bad_request('Invalid transport ' + transport) else: if sid not in self.sockets: self._log_error_once('Invalid session ' + sid, 'bad-sid') r = self._bad_request('Invalid session ' + sid) else: socket = self._get_socket(sid) try: packets = socket.handle_get_request( environ, start_response) if isinstance(packets, list): r = self._ok(packets, jsonp_index=jsonp_index) else: r = packets except exceptions.EngineIOError: if sid in self.sockets: # pragma: no cover self.disconnect(sid) r = self._bad_request() if sid in self.sockets and self.sockets[sid].closed: del self.sockets[sid] elif method == 'POST': if sid is None or sid not in self.sockets: self._log_error_once( 'Invalid session ' + (sid or 'None'), 'bad-sid') r = self._bad_request('Invalid session ' + (sid or 'None')) else: socket = self._get_socket(sid) try: socket.handle_post_request(environ) r = self._ok(jsonp_index=jsonp_index) except exceptions.EngineIOError: if sid in self.sockets: # pragma: no cover self.disconnect(sid) r = self._bad_request() except: # pragma: no cover # for any other unexpected errors, we log the error # and keep going self.logger.exception('post request handler error') r = self._ok(jsonp_index=jsonp_index) elif method == 'OPTIONS': r = self._ok() else: self.logger.warning('Method %s not supported', method) r = self._method_not_found() if not isinstance(r, dict): return r or [] if self.http_compression and \ len(r['response']) >= self.compression_threshold: encodings = [e.split(';')[0].strip() for e in environ.get('HTTP_ACCEPT_ENCODING', '').split(',')] for encoding in encodings: if encoding in self.compression_methods: r['response'] = \ getattr(self, '_' + encoding)(r['response']) r['headers'] += [('Content-Encoding', encoding)] break cors_headers = self._cors_headers(environ) start_response(r['status'], r['headers'] + cors_headers) return [r['response']] def start_background_task(self, target, *args, **kwargs): """Start a background task using the appropriate async model. This is a utility function that applications can use to start a background task using the method that is compatible with the selected async mode. :param target: the target function to execute. :param args: arguments to pass to the function. :param kwargs: keyword arguments to pass to the function. This function returns an object compatible with the `Thread` class in the Python standard library. The `start()` method on this object is already called by this function. """ th = self._async['thread'](target=target, args=args, kwargs=kwargs) th.start() return th # pragma: no cover def sleep(self, seconds=0): """Sleep for the requested amount of time using the appropriate async model. This is a utility function that applications can use to put a task to sleep without having to worry about using the correct call for the selected async mode. """ return self._async['sleep'](seconds) def create_queue(self, *args, **kwargs): """Create a queue object using the appropriate async model. This is a utility function that applications can use to create a queue without having to worry about using the correct call for the selected async mode. """ return self._async['queue'](*args, **kwargs) def get_queue_empty_exception(self): """Return the queue empty exception for the appropriate async model. This is a utility function that applications can use to work with a queue without having to worry about using the correct call for the selected async mode. """ return self._async['queue_empty'] def create_event(self, *args, **kwargs): """Create an event object using the appropriate async model. This is a utility function that applications can use to create an event without having to worry about using the correct call for the selected async mode. """ return self._async['event'](*args, **kwargs) def generate_id(self): """Generate a unique session id.""" id = base64.b64encode( secrets.token_bytes(12) + self.sequence_number.to_bytes(3, 'big')) self.sequence_number = (self.sequence_number + 1) & 0xffffff return id.decode('utf-8').replace('/', '_').replace('+', '-') def _generate_sid_cookie(self, sid, attributes): """Generate the sid cookie.""" cookie = attributes.get('name', 'io') + '=' + sid for attribute, value in attributes.items(): if attribute == 'name': continue if callable(value): value = value() if value is True: cookie += '; ' + attribute else: cookie += '; ' + attribute + '=' + value return cookie def _handle_connect(self, environ, start_response, transport, jsonp_index=None): """Handle a client connection request.""" if self.start_service_task: # start the service task to monitor connected clients self.start_service_task = False self.start_background_task(self._service_task) sid = self.generate_id() s = socket.Socket(self, sid) self.sockets[sid] = s pkt = packet.Packet(packet.OPEN, { 'sid': sid, 'upgrades': self._upgrades(sid, transport), 'pingTimeout': int(self.ping_timeout * 1000), 'pingInterval': int( self.ping_interval + self.ping_interval_grace_period) * 1000}) s.send(pkt) s.schedule_ping() # NOTE: some sections below are marked as "no cover" to workaround # what seems to be a bug in the coverage package. All the lines below # are covered by tests, but some are not reported as such for some # reason ret = self._trigger_event('connect', sid, environ, run_async=False) if ret is not None and ret is not True: # pragma: no cover del self.sockets[sid] self.logger.warning('Application rejected connection') return self._unauthorized(ret or None) if transport == 'websocket': # pragma: no cover ret = s.handle_get_request(environ, start_response) if s.closed and sid in self.sockets: # websocket connection ended, so we are done del self.sockets[sid] return ret else: # pragma: no cover s.connected = True headers = None if self.cookie: if isinstance(self.cookie, dict): headers = [( 'Set-Cookie', self._generate_sid_cookie(sid, self.cookie) )] else: headers = [( 'Set-Cookie', self._generate_sid_cookie(sid, { 'name': self.cookie, 'path': '/', 'SameSite': 'Lax' }) )] try: return self._ok(s.poll(), headers=headers, jsonp_index=jsonp_index) except exceptions.QueueEmpty: return self._bad_request() def _upgrades(self, sid, transport): """Return the list of possible upgrades for a client connection.""" if not self.allow_upgrades or self._get_socket(sid).upgraded or \ self._async['websocket'] is None or transport == 'websocket': return [] return ['websocket'] def _trigger_event(self, event, *args, **kwargs): """Invoke an event handler.""" run_async = kwargs.pop('run_async', False) if event in self.handlers: if run_async: return self.start_background_task(self.handlers[event], *args) else: try: return self.handlers[event](*args) except: self.logger.exception(event + ' handler error') if event == 'connect': # if connect handler raised error we reject the # connection return False def _get_socket(self, sid): """Return the socket object for a given session.""" try: s = self.sockets[sid] except KeyError: raise KeyError('Session not found') if s.closed: del self.sockets[sid] raise KeyError('Session is disconnected') return s def _ok(self, packets=None, headers=None, jsonp_index=None): """Generate a successful HTTP response.""" if packets is not None: if headers is None: headers = [] headers += [('Content-Type', 'text/plain; charset=UTF-8')] return {'status': '200 OK', 'headers': headers, 'response': payload.Payload(packets=packets).encode( jsonp_index=jsonp_index).encode('utf-8')} else: return {'status': '200 OK', 'headers': [('Content-Type', 'text/plain')], 'response': b'OK'} def _bad_request(self, message=None): """Generate a bad request HTTP error response.""" if message is None: message = 'Bad Request' message = packet.Packet.json.dumps(message) return {'status': '400 BAD REQUEST', 'headers': [('Content-Type', 'text/plain')], 'response': message.encode('utf-8')} def _method_not_found(self): """Generate a method not found HTTP error response.""" return {'status': '405 METHOD NOT FOUND', 'headers': [('Content-Type', 'text/plain')], 'response': b'Method Not Found'} def _unauthorized(self, message=None): """Generate a unauthorized HTTP error response.""" if message is None: message = 'Unauthorized' message = packet.Packet.json.dumps(message) return {'status': '401 UNAUTHORIZED', 'headers': [('Content-Type', 'application/json')], 'response': message.encode('utf-8')} def _cors_allowed_origins(self, environ): default_origins = [] if 'wsgi.url_scheme' in environ and 'HTTP_HOST' in environ: default_origins.append('{scheme}://{host}'.format( scheme=environ['wsgi.url_scheme'], host=environ['HTTP_HOST'])) if 'HTTP_X_FORWARDED_HOST' in environ: scheme = environ.get( 'HTTP_X_FORWARDED_PROTO', environ['wsgi.url_scheme']).split(',')[0].strip() default_origins.append('{scheme}://{host}'.format( scheme=scheme, host=environ['HTTP_X_FORWARDED_HOST'].split( ',')[0].strip())) if self.cors_allowed_origins is None: allowed_origins = default_origins elif self.cors_allowed_origins == '*': allowed_origins = None elif isinstance(self.cors_allowed_origins, str): allowed_origins = [self.cors_allowed_origins] else: allowed_origins = self.cors_allowed_origins return allowed_origins def _cors_headers(self, environ): """Return the cross-origin-resource-sharing headers.""" if self.cors_allowed_origins == []: # special case, CORS handling is completely disabled return [] headers = [] allowed_origins = self._cors_allowed_origins(environ) if 'HTTP_ORIGIN' in environ and \ (allowed_origins is None or environ['HTTP_ORIGIN'] in allowed_origins): headers = [('Access-Control-Allow-Origin', environ['HTTP_ORIGIN'])] if environ['REQUEST_METHOD'] == 'OPTIONS': headers += [('Access-Control-Allow-Methods', 'OPTIONS, GET, POST')] if 'HTTP_ACCESS_CONTROL_REQUEST_HEADERS' in environ: headers += [('Access-Control-Allow-Headers', environ['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])] if self.cors_credentials: headers += [('Access-Control-Allow-Credentials', 'true')] return headers def _gzip(self, response): """Apply gzip compression to a response.""" bytesio = io.BytesIO() with gzip.GzipFile(fileobj=bytesio, mode='w') as gz: gz.write(response) return bytesio.getvalue() def _deflate(self, response): """Apply deflate compression to a response.""" return zlib.compress(response) def _log_error_once(self, message, message_key): """Log message with logging.ERROR level the first time, then log with given level.""" if message_key not in self.log_message_keys: self.logger.error(message + ' (further occurrences of this error ' 'will be logged with level INFO)') self.log_message_keys.add(message_key) else: self.logger.info(message) def _service_task(self): # pragma: no cover """Monitor connected clients and clean up those that time out.""" while True: if len(self.sockets) == 0: # nothing to do self.sleep(self.ping_timeout) continue # go through the entire client list in a ping interval cycle sleep_interval = float(self.ping_timeout) / len(self.sockets) try: # iterate over the current clients for s in self.sockets.copy().values(): if not s.closing and not s.closed: s.check_ping_timeout() self.sleep(sleep_interval) except (SystemExit, KeyboardInterrupt): self.logger.info('service task canceled') break except: # an unexpected exception has occurred, log it and continue self.logger.exception('service task exception')