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Implement different mtproto proxy protocols; refactor obfuscated2

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This commit is contained in:
Сергей Прохоров
2019-03-10 01:00:11 +01:00
parent baa8970bb6
commit b873aa67cc
8 changed files with 209 additions and 68 deletions
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7
telethon/network/connection/__init__.py
View File

@@ -2,5 +2,10 @@ from .tcpfull import ConnectionTcpFull
from .tcpintermediate import ConnectionTcpIntermediate
from .tcpabridged import ConnectionTcpAbridged
from .tcpobfuscated import ConnectionTcpObfuscated
from .tcpmtproxy import ConnectionTcpMTProxy
from .tcpmtproxy import (
TcpMTProxy,
ConnectionTcpMTProxyAbridged,
ConnectionTcpMTProxyIntermediate,
ConnectionTcpMTProxyRandomizedIntermediate
)
from .http import ConnectionHttp

2
telethon/network/connection/connection.py
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@@ -30,6 +30,8 @@ class Connection(abc.ABC):
self._connected = False
self._send_task = None
self._recv_task = None
self._codec = None
self._obfuscation = None # TcpObfuscated and MTProxy
self._send_queue = asyncio.Queue(1)
self._recv_queue = asyncio.Queue(1)

40
telethon/network/connection/tcpabridged.py
View File

@@ -9,34 +9,36 @@ class ConnectionTcpAbridged(Connection):
only require 1 byte if the packet length is less than
508 bytes (127 << 2, which is very common).
"""
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._codec = AbridgedPacket()
def _init_conn(self):
self._writer.write(b'\xef')
def _write(self, data):
"""
Define wrapper write methods for `TcpObfuscated` to override.
"""
self._writer.write(data)
async def _read(self, n):
"""
Define wrapper read methods for `TcpObfuscated` to override.
"""
return await self._reader.readexactly(n)
self._writer.write(self._codec.tag)
def _send(self, data):
self._writer.write(self._codec.encode_packet(data))
async def _recv(self):
return await self._codec.read_packet(self._reader)
class AbridgedPacket:
tag = b'\xef'
mtproto_proxy_tag = b'\xef\xef\xef\xef'
def encode_packet(self, data):
length = len(data) >> 2
if length < 127:
length = struct.pack('B', length)
else:
length = b'\x7f' + int.to_bytes(length, 3, 'little')
return length + data
self._write(length + data)
async def _recv(self):
length = struct.unpack('<B', await self._read(1))[0]
async def read_packet(self, reader):
length = struct.unpack('<B', await reader.readexactly(1))[0]
if length >= 127:
length = struct.unpack(
'<i', await self._read(3) + b'\0')[0]
'<i', await reader.readexactly(3) + b'\0')[0]
return await self._read(length << 2)
return await reader.readexactly(length << 2)

45
telethon/network/connection/tcpintermediate.py
View File

@@ -1,4 +1,6 @@
import struct
import random
import os
from .connection import Connection
@@ -8,12 +10,47 @@ class ConnectionTcpIntermediate(Connection):
Intermediate mode between `ConnectionTcpFull` and `ConnectionTcpAbridged`.
Always sends 4 extra bytes for the packet length.
"""
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._codec = IntermediatePacket()
def _init_conn(self):
self._writer.write(b'\xee\xee\xee\xee')
self._writer.write(self._codec.tag)
def _send(self, data):
self._writer.write(struct.pack('<i', len(data)) + data)
self._writer.write(self._codec.encode_packet(data))
async def _recv(self):
return await self._reader.readexactly(
struct.unpack('<i', await self._reader.readexactly(4))[0])
return await self.codec.read_packet(self._reader)
class IntermediatePacket:
tag = b'\xee\xee\xee\xee'
mtproto_proxy_tag = tag
def encode_packet(self, data):
return struct.pack('<i', len(data)) + data
async def read_packet(self, reader):
length = struct.unpack('<i', await reader.readexactly(4))[0]
return await reader.readexactly(length)
class RandomizedIntermediatePacket(IntermediatePacket):
"""
Data packets are aligned to 4bytes. This codec adds random bytes of size
from 0 to 3 bytes, which are ignored by decoder.
"""
mtproto_proxy_tag = b'\xdd\xdd\xdd\xdd'
def encode_packet(self, data):
pad_size = random.randint(0, 3)
padding = os.urandom(pad_size)
return super().encode_packet(data + padding)
async def read_packet(self, reader):
packet_with_padding = await super().read_packet(reader)
pad_size = len(packet_with_padding) % 4
if pad_size > 0:
return packet_with_padding[:-pad_size]
return packet_with_padding

118
telethon/network/connection/tcpmtproxy.py
View File

@@ -1,12 +1,17 @@
import hashlib
import os
from .tcpobfuscated import ConnectionTcpObfuscated
from .connection import Connection
from .tcpabridged import AbridgedPacket
from .tcpintermediate import IntermediatePacket, RandomizedIntermediatePacket
from ...crypto import AESModeCTR
class ConnectionTcpMTProxy(ConnectionTcpObfuscated):
class TcpMTProxy(Connection):
"""
Wrapper around the "obfuscated2" mode that modifies it a little and allows
user to connect to the Telegram proxy servers commonly known as MTProxy.
Connector which allows user to connect to the Telegram via proxy servers
commonly known as MTProxy.
Implemented very ugly due to the leaky abstractions in Telethon networking
classes that should be refactored later (TODO).
@@ -15,6 +20,8 @@ class ConnectionTcpMTProxy(ConnectionTcpObfuscated):
The support for MTProtoProxies class is **EXPERIMENTAL** and prone to
be changed. You shouldn't be using this class yet.
"""
packet_codec = None
@staticmethod
def address_info(proxy_info):
if proxy_info is None:
@@ -25,19 +32,96 @@ class ConnectionTcpMTProxy(ConnectionTcpObfuscated):
proxy_host, proxy_port = self.address_info(proxy)
super().__init__(
proxy_host, proxy_port, dc_id, loop=loop, loggers=loggers)
# TODO: Implement the dd-secret secure mode (adds noise to fool DPI)
self._secret = bytes.fromhex(proxy[2])
if len(self._secret) != 16:
self._codec = self.packet_codec()
secret = bytes.fromhex(proxy[2])
is_dd = (len(secret) == 17) and (secret[0] == 0xDD)
if is_dd and (self.packet_codec != RandomizedIntermediatePacket):
raise ValueError(
"MTProxy secure mode is not implemented for now"
if len(self._secret) == 17 and self._secret[0] == 0xDD else
"MTProxy secret must be a hex-string representing 16 bytes"
)
"Only RandomizedIntermediate can be used with dd-secrets")
secret = secret[:-1] if is_dd else secret
if len(secret) != 16:
raise ValueError(
"MTProxy secret must be a hex-string representing 16 bytes")
self._dc_id = dc_id
self._secret = secret
def _compose_key(self, data):
return hashlib.sha256(data + self._secret).digest()
def _init_conn(self):
self._obfuscation = MTProxyIO(self._reader, self._writer,
self._codec.mtproto_proxy_tag,
self._secret, self._dc_id)
self._writer.write(self._obfuscation.header)
def _compose_tail(self, data):
dc_id_bytes = self._dc_id.to_bytes(2, "little", signed=True)
return super()._compose_tail(data[:60] + dc_id_bytes + data[62:])
def _send(self, data):
self._obfuscation.write(self._codec.encode_packet(data))
async def _recv(self):
return await self._codec.read_packet(self._obfuscation)
class ConnectionTcpMTProxyAbridged(TcpMTProxy):
"""
Connect to proxy using abridged protocol
"""
packet_codec = AbridgedPacket
class ConnectionTcpMTProxyIntermediate(TcpMTProxy):
"""
Connect to proxy using intermediate protocol
"""
packet_codec = IntermediatePacket
class ConnectionTcpMTProxyRandomizedIntermediate(TcpMTProxy):
"""
Connect to proxy using randomized intermediate protocol (dd-secrets)
"""
packet_codec = RandomizedIntermediatePacket
class MTProxyIO:
"""
It's very similar to tcpobfuscated.ObfuscatedIO, but the way
encryption keys, protocol tag and dc_id are encoded is different.
"""
header = None
def __init__(self, reader, writer, protocol_tag, secret, dc_id):
self._reader = reader
self._writer = writer
# Obfuscated messages secrets cannot start with any of these
keywords = (b'PVrG', b'GET ', b'POST', b'\xee\xee\xee\xee')
while True:
random = os.urandom(64)
if (random[0] != 0xef and
random[:4] not in keywords and
random[4:4] != b'\0\0\0\0'):
break
random = bytearray(random)
random_reversed = random[55:7:-1] # Reversed (8, len=48)
# Encryption has "continuous buffer" enabled
encrypt_key = hashlib.sha256(
bytes(random[8:40]) + secret).digest()
encrypt_iv = bytes(random[40:56])
decrypt_key = hashlib.sha256(
bytes(random_reversed[:32]) + secret).digest()
decrypt_iv = bytes(random_reversed[32:48])
self._aes_encrypt = AESModeCTR(encrypt_key, encrypt_iv)
self._aes_decrypt = AESModeCTR(decrypt_key, decrypt_iv)
random[56:60] = protocol_tag
dc_id_bytes = dc_id.to_bytes(2, "little", signed=True)
random = random[:60] + dc_id_bytes + random[62:]
random[56:64] = self._aes_encrypt.encrypt(bytes(random))[56:64]
self.header = random
async def readexactly(self, n):
return self._aes_decrypt.encrypt(await self._reader.readexactly(n))
def write(self, data):
self._writer.write(self._aes_encrypt.encrypt(data))

51
telethon/network/connection/tcpobfuscated.py
View File

@@ -1,11 +1,12 @@
import os
from .tcpabridged import AbridgedPacket
from .connection import Connection
from .tcpabridged import ConnectionTcpAbridged
from ...crypto import AESModeCTR
class ConnectionTcpObfuscated(ConnectionTcpAbridged):
class ConnectionTcpObfuscated(Connection):
"""
Mode that Telegram defines as "obfuscated2". Encodes the packet
just like `ConnectionTcpAbridged`, but encrypts every message with
@@ -15,16 +16,26 @@ class ConnectionTcpObfuscated(ConnectionTcpAbridged):
def __init__(self, ip, port, dc_id, *, loop, loggers, proxy=None):
super().__init__(
ip, port, dc_id, loop=loop, loggers=loggers, proxy=proxy)
self._aes_encrypt = None
self._aes_decrypt = None
def _write(self, data):
self._writer.write(self._aes_encrypt.encrypt(data))
async def _read(self, n):
return self._aes_decrypt.encrypt(await self._reader.readexactly(n))
self._codec = AbridgedPacket()
def _init_conn(self):
self._obfuscation = ObfuscatedIO(
self._reader, self._writer, self._codec.mtproto_proxy_tag)
self._writer.write(self._obfuscation.header)
def _send(self, data):
self._obfuscation.write(self._codec.encode_packet(data))
async def _recv(self):
return await self._codec.read_packet(self._obfuscation)
class ObfuscatedIO:
header = None
def __init__(self, reader, writer, protocol_tag):
self._reader = reader
self._writer = writer
# Obfuscated messages secrets cannot start with any of these
keywords = (b'PVrG', b'GET ', b'POST', b'\xee\xee\xee\xee')
while True:
@@ -38,23 +49,21 @@ class ConnectionTcpObfuscated(ConnectionTcpAbridged):
random_reversed = random[55:7:-1] # Reversed (8, len=48)
# Encryption has "continuous buffer" enabled
encrypt_key = self._compose_key(bytes(random[8:40]))
encrypt_key = bytes(random[8:40])
encrypt_iv = bytes(random[40:56])
decrypt_key = self._compose_key(bytes(random_reversed[:32]))
decrypt_key = bytes(random_reversed[:32])
decrypt_iv = bytes(random_reversed[32:48])
self._aes_encrypt = AESModeCTR(encrypt_key, encrypt_iv)
self._aes_decrypt = AESModeCTR(decrypt_key, decrypt_iv)
random[56:60] = b'\xef\xef\xef\xef'
random[56:64] = self._compose_tail(bytes(random))
random[56:60] = protocol_tag
random[56:64] = self._aes_encrypt.encrypt(bytes(random))[56:64]
self._writer.write(random)
self.header = random
# Next functions provide the variable parts of the connection handshake.
# This is necessary to modify obfuscated2 the way that MTProxy requires.
def _compose_key(self, data):
return data
async def readexactly(self, n):
return self._aes_decrypt.encrypt(await self._reader.readexactly(n))
def _compose_tail(self, data):
return self._aes_encrypt.encrypt(data)[56:64]
def write(self, data):
self._writer.write(self._aes_encrypt.encrypt(data))