""" This module contains the class used to communicate with Telegram's servers encrypting every packet, and relies on a valid AuthKey in the used Session. """ import gzip import logging import struct from threading import Lock from .. import helpers as utils from ..crypto import AES from ..errors import ( BadMessageError, InvalidChecksumError, BrokenAuthKeyError, rpc_message_to_error ) from ..extensions import BinaryReader from ..tl import TLMessage, MessageContainer, GzipPacked from ..tl.all_tlobjects import tlobjects from ..tl.types import ( MsgsAck, Pong, BadServerSalt, BadMsgNotification, MsgNewDetailedInfo, NewSessionCreated, MsgDetailedInfo ) from ..tl.functions.auth import LogOutRequest __log__ = logging.getLogger(__name__) class MtProtoSender: """MTProto Mobile Protocol sender (https://core.telegram.org/mtproto/description). Note that this class is not thread-safe, and calling send/receive from two or more threads at the same time is undefined behaviour. Rationale: a new connection should be spawned to send/receive requests in parallel, so thread-safety (hence locking) isn't needed. """ def __init__(self, session, connection): """ Initializes a new MTProto sender. :param session: the Session to be used with this sender. Must contain the IP and port of the server, salt, ID, and AuthKey, :param connection: the Connection to be used. """ self.session = session self.connection = connection # Message IDs that need confirmation self._need_confirmation = set() # Requests (as msg_id: Message) sent waiting to be received self._pending_receive = {} # Multithreading self._send_lock = Lock() def connect(self): """Connects to the server.""" self.connection.connect(self.session.server_address, self.session.port) def is_connected(self): """ Determines whether the sender is connected or not. :return: true if the sender is connected. """ return self.connection.is_connected() def disconnect(self): """Disconnects from the server.""" self.connection.close() self._need_confirmation.clear() self._clear_all_pending() # region Send and receive def send(self, *requests): """ Sends the specified TLObject(s) (which must be requests), and acknowledging any message which needed confirmation. :param requests: the requests to be sent. """ # Finally send our packed request(s) messages = [TLMessage(self.session, r) for r in requests] self._pending_receive.update({m.msg_id: m for m in messages}) # Pack everything in the same container if we need to send AckRequests if self._need_confirmation: messages.append( TLMessage(self.session, MsgsAck(list(self._need_confirmation))) ) self._need_confirmation.clear() if len(messages) == 1: message = messages[0] else: message = TLMessage(self.session, MessageContainer(messages)) # On bad_msg_salt errors, Telegram will reply with the ID of # the container and not the requests it contains, so in case # this happens we need to know to which container they belong. for m in messages: m.container_msg_id = message.msg_id self._send_message(message) def _send_acknowledge(self, msg_id): """Sends a message acknowledge for the given msg_id.""" self._send_message(TLMessage(self.session, MsgsAck([msg_id]))) def receive(self, update_state): """ Receives a single message from the connected endpoint. This method returns nothing, and will only affect other parts of the MtProtoSender such as the updates callback being fired or a pending request being confirmed. Any unhandled object (likely updates) will be passed to update_state.process(TLObject). :param update_state: the UpdateState that will process all the received Update and Updates objects. """ try: body = self.connection.recv() except (BufferError, InvalidChecksumError): # TODO BufferError, we should spot the cause... # "No more bytes left"; something wrong happened, clear # everything to be on the safe side, or: # # "This packet should be skipped"; since this may have # been a result for a request, invalidate every request # and just re-invoke them to avoid problems __log__.exception('Error while receiving server response. ' '%d pending request(s) will be ignored', len(self._pending_receive)) self._clear_all_pending() return message, remote_msg_id, remote_seq = self._decode_msg(body) with BinaryReader(message) as reader: self._process_msg(remote_msg_id, remote_seq, reader, update_state) # endregion # region Low level processing def _send_message(self, message): """ Sends the given encrypted through the network. :param message: the TLMessage to be sent. """ with self._send_lock: self.connection.send(utils.pack_message(self.session, message)) def _decode_msg(self, body): """ Decodes the body of the payload received from the network. :param body: the body to be decoded. :return: a tuple of (decoded message, remote message id, remote seq). """ if len(body) < 8: if body == b'l\xfe\xff\xff': raise BrokenAuthKeyError() else: raise BufferError("Can't decode packet ({})".format(body)) with BinaryReader(body) as reader: return utils.unpack_message(self.session, reader) def _process_msg(self, msg_id, sequence, reader, state): """ Processes the message read from the network inside reader. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the BinaryReader that contains the message. :param state: the current UpdateState. :return: true if the message was handled correctly, false otherwise. """ # TODO Check salt, session_id and sequence_number self._need_confirmation.add(msg_id) code = reader.read_int(signed=False) reader.seek(-4) # These are a bit of special case, not yet generated by the code gen if code == 0xf35c6d01: # rpc_result, (response of an RPC call) __log__.debug('Processing Remote Procedure Call result') return self._handle_rpc_result(msg_id, sequence, reader) if code == MessageContainer.CONSTRUCTOR_ID: __log__.debug('Processing container result') return self._handle_container(msg_id, sequence, reader, state) if code == GzipPacked.CONSTRUCTOR_ID: __log__.debug('Processing gzipped result') return self._handle_gzip_packed(msg_id, sequence, reader, state) if code not in tlobjects: __log__.warning( 'Unknown message with ID %d, data left in the buffer %s', hex(code), repr(reader.get_bytes()[reader.tell_position():]) ) return False obj = reader.tgread_object() __log__.debug('Processing %s result', type(obj).__name__) if isinstance(obj, Pong): return self._handle_pong(msg_id, sequence, obj) if isinstance(obj, BadServerSalt): return self._handle_bad_server_salt(msg_id, sequence, obj) if isinstance(obj, BadMsgNotification): return self._handle_bad_msg_notification(msg_id, sequence, obj) if isinstance(obj, MsgDetailedInfo): return self._handle_msg_detailed_info(msg_id, sequence, obj) if isinstance(obj, MsgNewDetailedInfo): return self._handle_msg_new_detailed_info(msg_id, sequence, obj) if isinstance(obj, NewSessionCreated): return self._handle_new_session_created(msg_id, sequence, obj) if isinstance(obj, MsgsAck): # may handle the request we wanted # Ignore every ack request *unless* when logging out, when it's # when it seems to only make sense. We also need to set a non-None # result since Telegram doesn't send the response for these. for msg_id in obj.msg_ids: r = self._pop_request_of_type(msg_id, LogOutRequest) if r: r.result = True # Telegram won't send this value r.confirm_received.set() return True # If the object isn't any of the above, then it should be an Update. self.session.process_entities(obj) if state: state.process(obj) return True # endregion # region Message handling def _pop_request(self, msg_id): """ Pops a pending **request** from self._pending_receive. :param msg_id: the ID of the message that belongs to the request. :return: the request, or None if it wasn't found. """ message = self._pending_receive.pop(msg_id, None) if message: return message.request def _pop_request_of_type(self, msg_id, t): """ Pops a pending **request** from self._pending_receive. :param msg_id: the ID of the message that belongs to the request. :param t: the type of the desired request. :return: the request matching the type t, or None if it wasn't found. """ message = self._pending_receive.get(msg_id, None) if message and isinstance(message.request, t): return self._pending_receive.pop(msg_id).request def _pop_requests_of_container(self, container_msg_id): """ Pops pending **requests** from self._pending_receive. :param container_msg_id: the ID of the container. :return: the requests that belong to the given container. May be empty. """ msgs = [msg for msg in self._pending_receive.values() if msg.container_msg_id == container_msg_id] requests = [msg.request for msg in msgs] for msg in msgs: self._pending_receive.pop(msg.msg_id, None) return requests def _clear_all_pending(self): """ Clears all pending requests, and flags them all as received. """ for r in self._pending_receive.values(): r.request.confirm_received.set() self._pending_receive.clear() def _resend_request(self, msg_id): """ Re-sends the request that belongs to a certain msg_id. This may also be the msg_id of a container if they were sent in one. :param msg_id: the ID of the request to be resent. """ request = self._pop_request(msg_id) if request: return self.send(request) requests = self._pop_requests_of_container(msg_id) if requests: return self.send(*requests) def _handle_pong(self, msg_id, sequence, pong): """ Handles a Pong response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the Pong. :return: true, as it always succeeds. """ request = self._pop_request(pong.msg_id) if request: request.result = pong request.confirm_received.set() return True def _handle_container(self, msg_id, sequence, reader, state): """ Handles a MessageContainer response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the MessageContainer. :return: true, as it always succeeds. """ for inner_msg_id, _, inner_len in MessageContainer.iter_read(reader): begin_position = reader.tell_position() # Note that this code is IMPORTANT for skipping RPC results of # lost requests (i.e., ones from the previous connection session) try: if not self._process_msg(inner_msg_id, sequence, reader, state): reader.set_position(begin_position + inner_len) except: # If any error is raised, something went wrong; skip the packet reader.set_position(begin_position + inner_len) raise return True def _handle_bad_server_salt(self, msg_id, sequence, bad_salt): """ Handles a BadServerSalt response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the BadServerSalt. :return: true, as it always succeeds. """ self.session.salt = bad_salt.new_server_salt self.session.save() # "the bad_server_salt response is received with the # correct salt, and the message is to be re-sent with it" self._resend_request(bad_salt.bad_msg_id) return True def _handle_bad_msg_notification(self, msg_id, sequence, bad_msg): """ Handles a BadMessageError response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the BadMessageError. :return: true, as it always succeeds. """ error = BadMessageError(bad_msg.error_code) __log__.warning('Read bad msg notification %s: %s', bad_msg, error) if bad_msg.error_code in (16, 17): # sent msg_id too low or too high (respectively). # Use the current msg_id to determine the right time offset. self.session.update_time_offset(correct_msg_id=msg_id) __log__.info('Attempting to use the correct time offset') self._resend_request(bad_msg.bad_msg_id) return True elif bad_msg.error_code == 32: # msg_seqno too low, so just pump it up by some "large" amount # TODO A better fix would be to start with a new fresh session ID self.session._sequence += 64 __log__.info('Attempting to set the right higher sequence') self._resend_request(bad_msg.bad_msg_id) return True elif bad_msg.error_code == 33: # msg_seqno too high never seems to happen but just in case self.session._sequence -= 16 __log__.info('Attempting to set the right lower sequence') self._resend_request(bad_msg.bad_msg_id) return True else: raise error def _handle_msg_detailed_info(self, msg_id, sequence, msg_new): """ Handles a MsgDetailedInfo response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the MsgDetailedInfo. :return: true, as it always succeeds. """ # TODO For now, simply ack msg_new.answer_msg_id # Relevant tdesktop source code: https://goo.gl/VvpCC6 self._send_acknowledge(msg_new.answer_msg_id) return True def _handle_msg_new_detailed_info(self, msg_id, sequence, msg_new): """ Handles a MsgNewDetailedInfo response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the MsgNewDetailedInfo. :return: true, as it always succeeds. """ # TODO For now, simply ack msg_new.answer_msg_id # Relevant tdesktop source code: https://goo.gl/G7DPsR self._send_acknowledge(msg_new.answer_msg_id) return True def _handle_new_session_created(self, msg_id, sequence, new_session): """ Handles a NewSessionCreated response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the NewSessionCreated. :return: true, as it always succeeds. """ self.session.salt = new_session.server_salt # TODO https://goo.gl/LMyN7A return True def _handle_rpc_result(self, msg_id, sequence, reader): """ Handles a RPCResult response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the RPCResult. :return: true if the request ID to which this result belongs is found, false otherwise (meaning nothing was read). """ reader.read_int(signed=False) # code request_id = reader.read_long() inner_code = reader.read_int(signed=False) request = self._pop_request(request_id) if inner_code == 0x2144ca19: # RPC Error if self.session.report_errors and request: error = rpc_message_to_error( reader.read_int(), reader.tgread_string(), report_method=type(request).CONSTRUCTOR_ID ) else: error = rpc_message_to_error( reader.read_int(), reader.tgread_string() ) # Acknowledge that we received the error self._send_acknowledge(request_id) if request: request.rpc_error = error request.confirm_received.set() # else TODO Where should this error be reported? # Read may be async. Can an error not-belong to a request? return True # All contents were read okay elif request: if inner_code == 0x3072cfa1: # GZip packed unpacked_data = gzip.decompress(reader.tgread_bytes()) with BinaryReader(unpacked_data) as compressed_reader: request.on_response(compressed_reader) else: reader.seek(-4) request.on_response(reader) self.session.process_entities(request.result) request.confirm_received.set() return True # If it's really a result for RPC from previous connection # session, it will be skipped by the handle_container() __log__.warning('Lost request will be skipped') return False def _handle_gzip_packed(self, msg_id, sequence, reader, state): """ Handles a GzipPacked response. :param msg_id: the ID of the message. :param sequence: the sequence of the message. :param reader: the reader containing the GzipPacked. :return: the result of processing the packed message. """ with BinaryReader(GzipPacked.read(reader)) as compressed_reader: # We are reentering process_msg, which seemingly the same msg_id # to the self._need_confirmation set. Remove it from there first # to avoid any future conflicts (i.e. if we "ignore" messages # that we are already aware of, see 1a91c02 and old 63dfb1e) self._need_confirmation -= {msg_id} return self._process_msg(msg_id, sequence, compressed_reader, state) # endregion