272 lines
12 KiB
Python
272 lines
12 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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from binascii import hexlify
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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 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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from Crypto.Util.number import long_to_bytes, bytes_to_long
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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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i = 0
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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, server_salt=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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self.timedelta = 0
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self.session_id = os.urandom(8)
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self.auth_key = auth_key
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self.auth_key_id = SHA.new(self.auth_key).digest()[-8:] if self.auth_key else None
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self.sock.settimeout(5.0)
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self.MAX_RETRY = 5;
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self.AUTH_MAX_RETRY = 5;
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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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def send_message(self, message_data):
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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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message_id = struct.pack('<Q', int((time()+self.timedelta)*2**30)*4)
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if self.auth_key is None or self.server_salt is None:
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# Unencrypted data send
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message = (b'\x00\x00\x00\x00\x00\x00\x00\x00' +
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message_id +
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struct.pack('<I', len(message_data)) +
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message_data)
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else:
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# Encrypted data send
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encrypted_data = (self.server_salt +
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self.session_id +
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message_id +
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struct.pack('<II', self.number, len(message_data)) +
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message_data)
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message_key = SHA.new(encrypted_data).digest()[-16:]
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padding = os.urandom((-len(encrypted_data)) % 16)
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aes_key, aes_iv = self.aes_calculate(message_key)
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message = (self.auth_key_id + message_key +
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crypt.ige_encrypt(encrypted_data+padding, aes_key, aes_iv))
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step1 = struct.pack('<II', len(message)+12, self.number) + message
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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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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) < 4:
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raise Exception("Nothing 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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# check the CRC32
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if not crc32(packet_length_data + packet[0:-4]) == struct.unpack('<I', packet[-4:])[0]:
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raise Exception("CRC32 was not correct!")
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x = struct.unpack("<I", packet[:4])
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auth_key_id = packet[4:12]
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if auth_key_id == b'\x00\x00\x00\x00\x00\x00\x00\x00':
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# No encryption - Plain text
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(message_id, message_length) = struct.unpack("<8sI", packet[12:24])
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data = packet[24:24+message_length]
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elif auth_key_id == self.auth_key_id:
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message_key = packet[12:28]
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encrypted_data = packet[28:-4]
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aes_key, aes_iv = self.aes_calculate(message_key, direction="from server")
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decrypted_data = crypt.ige_decrypt(encrypted_data, aes_key, aes_iv)
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assert decrypted_data[0:8] == self.server_salt
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assert decrypted_data[8:16] == self.session_id
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message_id = decrypted_data[16:24]
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seq_no = struct.unpack("<I", decrypted_data[24:28])[0]
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message_data_length = struct.unpack("<I", decrypted_data[28:32])[0]
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data = decrypted_data[32:32+message_data_length]
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else:
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raise Exception("Got unknown auth_key id")
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return data
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def method_call(self, method, **kwargs):
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#print(kwargs)
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for i in range(1, self.MAX_RETRY):
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try:
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self.send_message(TL.serialize_method(method, **kwargs))
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server_answer = self.recv_message()
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except socket.timeout:
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print("Retry call method")
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continue
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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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f = open(os.path.join(os.path.dirname(__file__), "rsa.pub"))
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key = RSA.importKey(f.read())
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print(getattr(key.key, 'n') . getattr(key.key, 'e'))
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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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pq = bytes_to_long(pq_bytes)
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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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p_bytes = long_to_bytes(p)
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q_bytes = long_to_bytes(q)
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new_nonce = os.urandom(32)
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data = TL.serialize_obj('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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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", len(to_encrypt))
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server_dh_params = self.method_call('req_DH_params',
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nonce=nonce,
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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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answer_with_hash = crypt.ige_decrypt(encrypted_answer, tmp_aes_key, tmp_aes_iv)
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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 = bytes_to_long(dh_prime_str)
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g_a = bytes_to_long(g_a_str)
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assert prime.isprime(dh_prime)
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retry_id = 0
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b_str = os.urandom(256)
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b = bytes_to_long(b_str)
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g_b = pow(g, b, dh_prime)
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g_b_str = long_to_bytes(g_b)
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data = TL.serialize_obj('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_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 = crypt.ige_encrypt(data_with_sha_padded, tmp_aes_key, tmp_aes_iv)
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for i in range(1, self.AUTH_MAX_RETRY): # retry when dh_gen_retry or dh_gen_fail
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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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# print Set_client_DH_params_answer
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auth_key = pow(g_a, b, dh_prime)
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auth_key_str = long_to_bytes(auth_key)
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auth_key_sha = SHA.new(auth_key_str).digest()
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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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if Set_client_DH_params_answer.name == 'dh_gen_ok':
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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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self.auth_key_id = auth_key_sha[-8:]
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print("Auth key generated")
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return "Auth Ok"
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elif Set_client_DH_params_answer.name == 'dh_gen_retry':
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assert Set_client_DH_params_answer['new_nonce_hash2'] == new_nonce_hash2
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print ("Retry Auth")
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elif Set_client_DH_params_answer.name == 'dh_gen_fail':
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assert Set_client_DH_params_answer['new_nonce_hash3'] == new_nonce_hash3
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print("Auth Failed")
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raise Exception("Auth Failed")
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else: raise Exception("Response Error")
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def aes_calculate(self, msg_key, direction="to server"):
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x = 0 if direction == "to server" else 8
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sha1_a = SHA.new(msg_key + self.auth_key[x:x+32]).digest()
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sha1_b = SHA.new(self.auth_key[x+32:x+48] + msg_key + self.auth_key[48+x:64+x]).digest()
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sha1_c = SHA.new(self.auth_key[x+64:x+96] + msg_key).digest()
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sha1_d = SHA.new(msg_key + self.auth_key[x+96:x+128]).digest()
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aes_key = sha1_a[0:8] + sha1_b[8:20] + sha1_c[4:16]
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aes_iv = sha1_a[8:20] + sha1_b[0:8] + sha1_c[16:20] + sha1_d[0:8]
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return aes_key, aes_iv
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