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Document the network/ module

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Lonami Exo
2017-11-30 13:20:51 +01:00
parent 7509ba9067
commit 9046b46fcd
5 changed files with 300 additions and 46 deletions
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102
telethon/network/connection.py
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@@ -1,3 +1,7 @@
"""
This module holds both the Connection class and the ConnectionMode enum,
which specifies the protocol to be used by the Connection.
"""
import os
import struct
from datetime import timedelta
@@ -35,16 +39,24 @@ class ConnectionMode(Enum):
class Connection:
"""Represents an abstract connection (TCP, TCP abridged...).
'mode' must be any of the ConnectionMode enumeration.
"""
Represents an abstract connection (TCP, TCP abridged...).
'mode' must be any of the ConnectionMode enumeration.
Note that '.send()' and '.recv()' refer to messages, which
will be packed accordingly, whereas '.write()' and '.read()'
work on plain bytes, with no further additions.
Note that '.send()' and '.recv()' refer to messages, which
will be packed accordingly, whereas '.write()' and '.read()'
work on plain bytes, with no further additions.
"""
def __init__(self, mode=ConnectionMode.TCP_FULL,
proxy=None, timeout=timedelta(seconds=5)):
"""
Initializes a new connection.
:param mode: the ConnectionMode to be used.
:param proxy: whether to use a proxy or not.
:param timeout: timeout to be used for all operations.
"""
self._mode = mode
self._send_counter = 0
self._aes_encrypt, self._aes_decrypt = None, None
@@ -75,6 +87,12 @@ class Connection:
setattr(self, 'read', self._read_plain)
def connect(self, ip, port):
"""
Estabilishes a connection to IP:port.
:param ip: the IP to connect to.
:param port: the port to connect to.
"""
try:
self.conn.connect(ip, port)
except OSError as e:
@@ -92,9 +110,13 @@ class Connection:
self._setup_obfuscation()
def get_timeout(self):
"""Returns the timeout used by the connection."""
return self.conn.timeout
def _setup_obfuscation(self):
"""
Sets up the obfuscated protocol.
"""
# Obfuscated messages secrets cannot start with any of these
keywords = (b'PVrG', b'GET ', b'POST', b'\xee' * 4)
while True:
@@ -122,13 +144,19 @@ class Connection:
self.conn.write(bytes(random))
def is_connected(self):
"""
Determines whether the connection is alive or not.
:return: true if it's connected.
"""
return self.conn.connected
def close(self):
"""Closes the connection."""
self.conn.close()
def clone(self):
"""Creates a copy of this Connection"""
"""Creates a copy of this Connection."""
return Connection(
mode=self._mode, proxy=self.conn.proxy, timeout=self.conn.timeout
)
@@ -141,6 +169,15 @@ class Connection:
raise ValueError('Invalid connection mode specified: ' + str(self._mode))
def _recv_tcp_full(self):
"""
Receives a message from the network,
internally encoded using the TCP full protocol.
May raise InvalidChecksumError if the received data doesn't
match its valid checksum.
:return: the read message payload.
"""
packet_len_seq = self.read(8) # 4 and 4
packet_len, seq = struct.unpack('<ii', packet_len_seq)
@@ -154,9 +191,21 @@ class Connection:
return body
def _recv_intermediate(self):
"""
Receives a message from the network,
internally encoded using the TCP intermediate protocol.
:return: the read message payload.
"""
return self.read(struct.unpack('<i', self.read(4))[0])
def _recv_abridged(self):
"""
Receives a message from the network,
internally encoded using the TCP abridged protocol.
:return: the read message payload.
"""
length = struct.unpack('<B', self.read(1))[0]
if length >= 127:
length = struct.unpack('<i', self.read(3) + b'\0')[0]
@@ -173,6 +222,12 @@ class Connection:
raise ValueError('Invalid connection mode specified: ' + str(self._mode))
def _send_tcp_full(self, message):
"""
Encapsulates and sends the given message payload
using the TCP full mode (length, sequence, message, crc32).
:param message: the message to be sent.
"""
# https://core.telegram.org/mtproto#tcp-transport
# total length, sequence number, packet and checksum (CRC32)
length = len(message) + 12
@@ -182,9 +237,21 @@ class Connection:
self.write(data + crc)
def _send_intermediate(self, message):
"""
Encapsulates and sends the given message payload
using the TCP intermediate mode (length, message).
:param message: the message to be sent.
"""
self.write(struct.pack('<i', len(message)) + message)
def _send_abridged(self, message):
"""
Encapsulates and sends the given message payload
using the TCP abridged mode (short length, message).
:param message: the message to be sent.
"""
length = len(message) >> 2
if length < 127:
length = struct.pack('B', length)
@@ -201,9 +268,21 @@ class Connection:
raise ValueError('Invalid connection mode specified: ' + str(self._mode))
def _read_plain(self, length):
"""
Reads data from the socket connection.
:param length: how many bytes should be read.
:return: a byte sequence with len(data) == length
"""
return self.conn.read(length)
def _read_obfuscated(self, length):
"""
Reads data and decrypts from the socket connection.
:param length: how many bytes should be read.
:return: the decrypted byte sequence with len(data) == length
"""
return self._aes_decrypt.encrypt(
self.conn.read(length)
)
@@ -216,9 +295,20 @@ class Connection:
raise ValueError('Invalid connection mode specified: ' + str(self._mode))
def _write_plain(self, data):
"""
Writes the given data through the socket connection.
:param data: the data in bytes to be written.
"""
self.conn.write(data)
def _write_obfuscated(self, data):
"""
Writes the given data through the socket connection,
using the obfuscated mode (AES encryption is applied on top).
:param data: the data in bytes to be written.
"""
self.conn.write(self._aes_encrypt.encrypt(data))
# endregion