# Pyrogram - Telegram MTProto API Client Library for Python

# Copyright (C) 2017-present Dan <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 asyncio

import logging

import time

from hashlib import sha1

from io import BytesIO

from os import urandom

import pyrogram

from pyrogram import raw

from pyrogram.connection import Connection

from pyrogram.crypto import aes, rsa, prime

from pyrogram.errors import SecurityCheckMismatch

from pyrogram.raw.core import TLObject, Long, Int

from .internals import MsgId

log = logging.getLogger(__name__)

class Auth:

MAX_RETRIES = 5

def __init__(self, client: "pyrogram.Client", dc_id: int, test_mode: bool):

self.dc_id = dc_id

self.test_mode = 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)

async def invoke(self, data: TLObject):

data = self.pack(data)

await self.connection.send(data)

response = BytesIO(await self.connection.recv())

return self.unpack(response)

async 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%s", self.dc_id)

await self.connection.connect()

# Step 1; Step 2

nonce = int.from_bytes(urandom(16), "little", signed=True)

log.debug("Send req_pq: %s", nonce)

res_pq = await self.invoke(raw.functions.ReqPqMulti(nonce=nonce))

log.debug("Got ResPq: %s", res_pq.server_nonce)

log.debug("Server public key fingerprints: %s", 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: %s", i)

public_key_fingerprint = i

break

else:

log.debug("Fingerprint unknown: %s", i)

else:

raise Exception("Public key not found")

# Step 3

pq = int.from_bytes(res_pq.pq, "big")

log.debug("Start PQ factorization: %s", pq)

start = time.time()

g = prime.decompose(pq)

p, q = sorted((g, pq // g)) # p < q

log.debug("Done PQ factorization (%ss): %s %s", 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 = raw.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 = await self.invoke(

raw.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: %s", 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 = raw.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 = await self.invoke(

raw.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

#######################

SecurityCheckMismatch.check(dh_prime == prime.CURRENT_DH_PRIME, "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")

SecurityCheckMismatch.check(1 < g < dh_prime - 1, "1 < g < dh_prime - 1")

SecurityCheckMismatch.check(1 < g_a < dh_prime - 1, "1 < g_a < dh_prime - 1")

SecurityCheckMismatch.check(1 < g_b < dh_prime - 1, "1 < g_b < dh_prime - 1")

SecurityCheckMismatch.check(

2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64),

"2 ** (2048 - 64) < g_a < dh_prime - 2 ** (2048 - 64)"

)

SecurityCheckMismatch.check(

2 ** (2048 - 64) < g_b < dh_prime - 2 ** (2048 - 64),

"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

SecurityCheckMismatch.check(

answer_with_hash[:20] == sha1(answer).digest(),

"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

SecurityCheckMismatch.check(nonce == res_pq.nonce, "nonce == res_pq.nonce")

# 2nd message

server_nonce = int.from_bytes(server_nonce, "little", signed=True)

SecurityCheckMismatch.check(nonce == server_dh_params.nonce, "nonce == server_dh_params.nonce")

SecurityCheckMismatch.check(

server_nonce == server_dh_params.server_nonce,

"server_nonce == server_dh_params.server_nonce"

)

# 3rd message

SecurityCheckMismatch.check(

nonce == set_client_dh_params_answer.nonce,

"nonce == set_client_dh_params_answer.nonce"

)

SecurityCheckMismatch.check(

server_nonce == set_client_dh_params_answer.server_nonce,

"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: %s", int.from_bytes(server_salt, "little"))

log.info("Done auth key exchange: %s", set_client_dh_params_answer.__class__.__name__)

except Exception as e:

log.info("Retrying due to %s: %s", type(e).__name__, e)

if retries_left:

retries_left -= 1

else:

raise e

await asyncio.sleep(1)

continue

else:

return auth_key

finally:

await self.connection.close()