273 lines
11 KiB
Python
273 lines
11 KiB
Python
# -*- coding: utf-8 -*-
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"""
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Created on Tue Sep 2 19:26:15 2014
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@author: Anton Grigoryev
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@author: Sammy Pfeiffer
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"""
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from binascii import crc32 as originalcrc32
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import numbers
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from datetime import datetime
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from time import time
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import io
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import os.path
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import json
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import socket
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import struct
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# pycrypto module
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from Crypto.Hash import SHA
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from Crypto.PublicKey import RSA
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from Crypto.Util.strxor import strxor
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# local modules
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import crypt
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import prime
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import TL
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def crc32(data):
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return originalcrc32(data) & 0xffffffff
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def vis(bs):
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"""
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Function to visualize byte streams. Split into bytes, print to console.
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:param bs: BYTE STRING
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"""
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bs = bytearray(bs)
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symbols_in_one_line = 8
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n = len(bs) // symbols_in_one_line
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for i in range(n):
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print(str(i*symbols_in_one_line)+" | "+" ".join(["%02X" % b for b in bs[i*symbols_in_one_line:(i+1)*symbols_in_one_line]])) # for every 8 symbols line
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if not len(bs) % symbols_in_one_line == 0:
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print(str((i+1)*symbols_in_one_line)+" | "+" ".join(["%02X" % b for b in bs[(i+1)*symbols_in_one_line:]])+"\n") # for last line
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class Session:
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""" Manages TCP Transport. encryption and message frames """
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def __init__(self, ip, port, auth_key=None):
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# creating socket
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self.sock = socket.socket()
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self.sock.connect((ip, port))
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self.number = 0
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if auth_key is None:
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self.create_auth_key()
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else:
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self.auth_key = auth_key
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def __del__(self):
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# closing socket when session object is deleted
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self.sock.close()
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@staticmethod
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def header_unencrypted(message):
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"""
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Creating header for the unencrypted message:
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:param message: byte string to send
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"""
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# Basic instructions: https://core.telegram.org/mtproto/description#unencrypted-message
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# Message id: https://core.telegram.org/mtproto/description#message-identifier-msg-id
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# http://stackoverflow.com/questions/8777753/converting-datetime-date-to-utc-timestamp-in-python
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# to make it work in py2 and py3 (py3 has the timestamp() method but py2 doesnt)
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curr_timestamp = (datetime.utcfromtimestamp(time()) - datetime(1970, 1, 1)).total_seconds()
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msg_id = int(curr_timestamp*2**30)*4
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#msg_id = int(datetime.utcnow().timestamp()*2**30)*4
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return (b'\x00\x00\x00\x00\x00\x00\x00\x00' +
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struct.pack('<Q', msg_id) +
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struct.pack('<I', len(message)))
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# TCP Transport
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# Instructions may be found here: https://core.telegram.org/mtproto#tcp-transport
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# If a payload (packet) needs to be transmitted from server to client or from client to server,
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# it is encapsulated as follows: 4 length bytes are added at the front (to include the length,
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# the sequence number, and CRC32; always divisible by 4) and 4 bytes with the packet sequence number
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# within this TCP connection (the first packet sent is numbered 0, the next one 1, etc.),
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# and 4 CRC32 bytes at the end (length, sequence number, and payload together).
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def send_message(self, message):
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"""
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Forming the message frame and sending message to server
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:param message: byte string to send
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"""
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data = self.header_unencrypted(message) + message
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step1 = struct.pack('<II', len(data)+12, self.number) + data
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step2 = step1 + struct.pack('<I', crc32(step1))
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self.sock.send(step2)
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self.number += 1
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# Sending message visualisation to console
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# print('>>')
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# vis(step2)
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def recv_message(self):
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"""
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Reading socket and receiving message from server. Check the CRC32.
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"""
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packet_length_data = self.sock.recv(4) # reads how many bytes to read
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if len(packet_length_data) > 0: # if we have smth. in the socket
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packet_length = struct.unpack("<I", packet_length_data)[0]
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packet = self.sock.recv(packet_length - 4) # read the rest of bytes from socket
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(x, auth_key_id, message_id, message_length)= struct.unpack("<I8s8sI", packet[0:24])
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data = packet[24:24+message_length]
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crc = packet[-4:]
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# Checking the CRC32 correctness of received data
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if crc32(packet_length_data + packet[0:-4]) == struct.unpack('<I', crc)[0]:
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return data
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else:
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raise Exception("CRC32 was not correct!")
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else:
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raise Exception("Nothing in the socket!")
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def method_call(self, method, **kwargs):
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z=io.BytesIO()
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TL.serialize_method(z, method, **kwargs)
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# z.getvalue() on py2.7 returns str, which means bytes
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# on py3.4 returns bytes
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# bytearray is closer to the same data type to be shared
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z_val = bytearray(z.getvalue())
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# print("z_val: " + z_val.__repr__())
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# print("z_val type: " + str(type(z_val)))
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# print("len of z_val: " + str(len(z_val)))
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self.send_message(z_val)
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server_answer = self.recv_message()
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return TL.deserialize(io.BytesIO(server_answer))
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def create_auth_key(self):
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nonce = os.urandom(16)
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print("Requesting PQ")
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ResPQ = self.method_call('req_pq', nonce=nonce)
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server_nonce = ResPQ['server_nonce']
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# TODO: selecting RSA public key based on this fingerprint
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public_key_fingerprint = ResPQ['server_public_key_fingerprints'][0]
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PQ_bytes = ResPQ['pq']
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# TODO: from_bytes here
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PQ = struct.unpack('>q', PQ_bytes)[0]
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[p, q] = prime.primefactors(PQ)
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if p > q: (p, q) = (q, p)
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assert p*q == PQ and p < q
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print("Factorization %d = %d * %d" % (PQ, p, q))
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# TODO: to_bytes here
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P_bytes = struct.pack('>i', p)
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Q_bytes = struct.pack('>i', q)
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f = open(os.path.join(os.path.dirname(__file__), "rsa.pub"))
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key = RSA.importKey(f.read())
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z = io.BytesIO()
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new_nonce = os.urandom(32)
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TL.serialize_obj(z, 'p_q_inner_data',
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pq=PQ_bytes,
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p=P_bytes,
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q=Q_bytes,
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nonce=nonce,
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server_nonce=server_nonce,
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new_nonce=new_nonce)
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data = z.getvalue()
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sha_digest = SHA.new(data).digest()
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random_bytes = os.urandom(255-len(data)-len(sha_digest))
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to_encrypt = sha_digest + data + random_bytes
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encrypted_data = key.encrypt(to_encrypt, 0)[0]
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print("Starting Diffie Hellman key exchange")
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server_DH_params = self.method_call('req_DH_params',
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nonce=nonce, # 16 bytes
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server_nonce=server_nonce,
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p=P_bytes,
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q=Q_bytes,
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public_key_fingerprint=public_key_fingerprint,
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encrypted_data=encrypted_data)
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assert nonce == server_DH_params['nonce']
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assert server_nonce == server_DH_params['server_nonce']
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encrypted_answer = server_DH_params['encrypted_answer']
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tmp_aes_key = SHA.new(new_nonce + server_nonce).digest() + SHA.new(server_nonce + new_nonce).digest()[0:12]
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tmp_aes_iv = SHA.new(server_nonce + new_nonce).digest()[12:20] + SHA.new(new_nonce + new_nonce).digest() + new_nonce[0:4]
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crypter = crypt.IGE(tmp_aes_key, tmp_aes_iv)
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answer_with_hash = crypter.decrypt(encrypted_answer)
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answer_hash = answer_with_hash[:20]
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answer = answer_with_hash[20:]
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# TODO: SHA hash assertion here
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server_DH_inner_data = TL.deserialize(io.BytesIO(answer))
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assert nonce == server_DH_inner_data['nonce']
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assert server_nonce == server_DH_inner_data['server_nonce']
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dh_prime_str = server_DH_inner_data['dh_prime']
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g = server_DH_inner_data['g']
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g_a_str = server_DH_inner_data['g_a']
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server_time = server_DH_inner_data['server_time']
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self.timedelta = server_time - time()
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print("Server-client time delta = %.1f s" % self.timedelta)
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dh_prime = int.from_bytes(dh_prime_str,'big')
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g_a = int.from_bytes(g_a_str,'big')
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assert prime.isprime(dh_prime)
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retry_id = 0
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while retry_id<25:
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try:
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b_str = os.urandom(256)
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b = int.from_bytes(b_str,'big')
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g_b = pow(g,b,dh_prime)
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g_b_str = int.to_bytes(g_b, g_b.bit_length() // 8 + 1, 'big')
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z = io.BytesIO()
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TL.serialize_obj(z, 'client_DH_inner_data',
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nonce=nonce,
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server_nonce=server_nonce,
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retry_id=retry_id,
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g_b=g_b_str)
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data = z.getvalue()
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data_with_sha = SHA.new(data).digest()+data
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data_with_sha_padded = data_with_sha + os.urandom(-len(data_with_sha) % 16)
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encrypted_data = crypter.encrypt(data_with_sha_padded)
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Set_client_DH_params_answer = self.method_call('set_client_DH_params',
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nonce=nonce,
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server_nonce=server_nonce,
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encrypted_data=encrypted_data)
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auth_key = pow(g_a, b, dh_prime)
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auth_key_str = int.to_bytes(auth_key, auth_key.bit_length() // 8 + 1, 'big')
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auth_key_sha = SHA.new(auth_key_str).digest()
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auth_key_hash = auth_key_sha[-8:]
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auth_key_aux_hash = auth_key_sha[:8]
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new_nonce_hash1 = SHA.new(new_nonce+b'\x01'+auth_key_aux_hash).digest()[-16:]
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new_nonce_hash2 = SHA.new(new_nonce+b'\x02'+auth_key_aux_hash).digest()[-16:]
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new_nonce_hash3 = SHA.new(new_nonce+b'\x03'+auth_key_aux_hash).digest()[-16:]
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assert Set_client_DH_params_answer['nonce'] == nonce
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assert Set_client_DH_params_answer['server_nonce'] == server_nonce
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assert Set_client_DH_params_answer['new_nonce_hash1'] == new_nonce_hash1
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print("Diffie Hellman key exchange processed successfully")
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self.server_salt = strxor(new_nonce[0:8], server_nonce[0:8])
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self.auth_key = auth_key_str
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print("Auth key generated")
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break
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except:
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print("Retry DH key exchange")
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retry_id += 1
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