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# Pyrogram - Telegram MTProto API Client Library for Python
# Copyright (C) 2017-2019 Dan Tès <https://github.com/delivrance>
#
# This file is part of Pyrogram.
#
# Pyrogram is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Pyrogram is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Pyrogram. If not, see <http://www.gnu.org/licenses/>.
import logging
import time
from hashlib import sha1
from io import BytesIO
from os import urandom
import pyrogram
from pyrogram.api import functions, types
from pyrogram.api.core import TLObject, Long, Int
from pyrogram.connection import Connection
from pyrogram.crypto import AES, RSA, Prime
from .internals import MsgId
log = logging.getLogger(__name__)
class Auth:
MAX_RETRIES = 5
def __init__(self, client: "pyrogram.Client", dc_id: int):
self.dc_id = dc_id
self.test_mode = client.storage.test_mode()
self.ipv6 = client.ipv6
self.proxy = client.proxy
self.connection = None
@staticmethod
def pack(data: TLObject) -> bytes:
return (
bytes(8)
+ Long(MsgId())
+ Int(len(data.write()))
+ data.write()
)
@staticmethod
def unpack(b: BytesIO):
b.seek(20) # Skip auth_key_id (8), message_id (8) and message_length (4)
return TLObject.read(b)
def send(self, data: TLObject):
data = self.pack(data)
self.connection.send(data)
response = BytesIO(self.connection.recv())
return self.unpack(response)
def create(self):
"""
https://core.telegram.org/mtproto/auth_key
https://core.telegram.org/mtproto/samples-auth_key
"""
retries_left = self.MAX_RETRIES
# The server may close the connection at any time, causing the auth key creation to fail.
# If that happens, just try again up to MAX_RETRIES times.
while True:
self.connection = Connection(self.dc_id, self.test_mode, self.ipv6, self.proxy)
try:
log.info("Start creating a new auth key on DC{}".format(self.dc_id))
self.connection.connect()
# Step 1; Step 2
nonce = int.from_bytes(urandom(16), "little", signed=True)
log.debug("Send req_pq: {}".format(nonce))
res_pq = self.send(functions.ReqPqMulti(nonce=nonce))
log.debug("Got ResPq: {}".format(res_pq.server_nonce))
log.debug("Server public key fingerprints: {}".format(res_pq.server_public_key_fingerprints))
for i in res_pq.server_public_key_fingerprints:
if i in RSA.server_public_keys:
log.debug("Using fingerprint: {}".format(i))
public_key_fingerprint = i
break
else:
log.debug("Fingerprint unknown: {}".format(i))
else:
raise Exception("Public key not found")
# Step 3
pq = int.from_bytes(res_pq.pq, "big")
log.debug("Start PQ factorization: {}".format(pq))
start = time.time()
g = Prime.decompose(pq)
p, q = sorted((g, pq // g)) # p < q
log.debug("Done PQ factorization ({}s): {} {}".format(round(time.time() - start, 3), p, q))
# Step 4
server_nonce = res_pq.server_nonce
new_nonce = int.from_bytes(urandom(32), "little", signed=True)
data = types.PQInnerData(
pq=res_pq.pq,
p=p.to_bytes(4, "big"),
q=q.to_bytes(4, "big"),
nonce=nonce,
server_nonce=server_nonce,
new_nonce=new_nonce,
).write()
sha = sha1(data).digest()
padding = urandom(- (len(data) + len(sha)) % 255)
data_with_hash = sha + data + padding
encrypted_data = RSA.encrypt(data_with_hash, public_key_fingerprint)
log.debug("Done encrypt data with RSA")
# Step 5. TODO: Handle "server_DH_params_fail". Code assumes response is ok
log.debug("Send req_DH_params")
server_dh_params = self.send(
functions.ReqDHParams(
nonce=nonce,
server_nonce=server_nonce,
p=p.to_bytes(4, "big"),
q=q.to_bytes(4, "big"),
public_key_fingerprint=public_key_fingerprint,
encrypted_data=encrypted_data
)
)
encrypted_answer = server_dh_params.encrypted_answer
server_nonce = server_nonce.to_bytes(16, "little", signed=True)
new_nonce = new_nonce.to_bytes(32, "little", signed=True)
tmp_aes_key = (
sha1(new_nonce + server_nonce).digest()
+ sha1(server_nonce + new_nonce).digest()[:12]
)
tmp_aes_iv = (
sha1(server_nonce + new_nonce).digest()[12:]
+ sha1(new_nonce + new_nonce).digest() + new_nonce[:4]
)
server_nonce = int.from_bytes(server_nonce, "little", signed=True)
answer_with_hash = AES.ige256_decrypt(encrypted_answer, tmp_aes_key, tmp_aes_iv)
answer = answer_with_hash[20:]
server_dh_inner_data = TLObject.read(BytesIO(answer))
log.debug("Done decrypting answer")
dh_prime = int.from_bytes(server_dh_inner_data.dh_prime, "big")
delta_time = server_dh_inner_data.server_time - time.time()
log.debug("Delta time: {}".format(round(delta_time, 3)))
# Step 6
g = server_dh_inner_data.g
b = int.from_bytes(urandom(256), "big")
g_b = pow(g, b, dh_prime).to_bytes(256, "big")
retry_id = 0
data = types.ClientDHInnerData(
nonce=nonce,
server_nonce=server_nonce,
retry_id=retry_id,
g_b=g_b
).write()
sha = sha1(data).digest()
padding = urandom(- (len(data) + len(sha)) % 16)
data_with_hash = sha + data + padding
encrypted_data = AES.ige256_encrypt(data_with_hash, tmp_aes_key, tmp_aes_iv)
log.debug("Send set_client_DH_params")
set_client_dh_params_answer = self.send(
functions.SetClientDHParams(
nonce=nonce,
server_nonce=server_nonce,
encrypted_data=encrypted_data
)
)
# TODO: Handle "auth_key_aux_hash" if the previous step fails
# Step 7; Step 8
g_a = int.from_bytes(server_dh_inner_data.g_a, "big")
auth_key = pow(g_a, b, dh_prime).to_bytes(256, "big")
server_nonce = server_nonce.to_bytes(16, "little", signed=True)
# TODO: Handle errors
#######################
# Security checks
#######################
assert dh_prime == Prime.CURRENT_DH_PRIME
log.debug("DH parameters check: OK")
# https://core.telegram.org/mtproto/security_guidelines#g-a-and-g-b-validation
g_b = int.from_bytes(g_b, "big")
assert 1 < g < dh_prime - 1
assert 1 < g_a < dh_prime - 1
assert 1 < g_b < dh_prime - 1
assert 2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64)
assert 2 ** (2048 - 64) < g_b < dh_prime - 2 ** (2048 - 64)
log.debug("g_a and g_b validation: OK")
# https://core.telegram.org/mtproto/security_guidelines#checking-sha1-hash-values
answer = server_dh_inner_data.write() # Call .write() to remove padding
assert answer_with_hash[:20] == sha1(answer).digest()
log.debug("SHA1 hash values check: OK")
# https://core.telegram.org/mtproto/security_guidelines#checking-nonce-server-nonce-and-new-nonce-fields
# 1st message
assert nonce == res_pq.nonce
# 2nd message
server_nonce = int.from_bytes(server_nonce, "little", signed=True)
assert nonce == server_dh_params.nonce
assert server_nonce == server_dh_params.server_nonce
# 3rd message
assert nonce == set_client_dh_params_answer.nonce
assert server_nonce == set_client_dh_params_answer.server_nonce
server_nonce = server_nonce.to_bytes(16, "little", signed=True)
log.debug("Nonce fields check: OK")
# Step 9
server_salt = AES.xor(new_nonce[:8], server_nonce[:8])
log.debug("Server salt: {}".format(int.from_bytes(server_salt, "little")))
log.info(
"Done auth key exchange: {}".format(
set_client_dh_params_answer.__class__.__name__
)
)
except Exception as e:
if retries_left:
retries_left -= 1
else:
raise e
time.sleep(1)
continue
else:
return auth_key
finally:
self.connection.close()
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