# 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 hashlib

import os

from pyrogram.api import types

def btoi(b: bytes) -> int:

return int.from_bytes(b, "big")

def itob(i: int) -> bytes:

return i.to_bytes(256, "big")

def sha256(data: bytes) -> bytes:

return hashlib.sha256(data).digest()

def xor(a: bytes, b: bytes) -> bytes:

return bytes(i ^ j for i, j in zip(a, b))

def compute_hash(algo: types.PasswordKdfAlgoSHA256SHA256PBKDF2HMACSHA512iter100000SHA256ModPow, password: str) -> bytes:

hash1 = sha256(algo.salt1 + password.encode() + algo.salt1)

hash2 = sha256(algo.salt2 + hash1 + algo.salt2)

hash3 = hashlib.pbkdf2_hmac("sha512", hash2, algo.salt1, 100000)

return sha256(algo.salt2 + hash3 + algo.salt2)

# noinspection PyPep8Naming

def compute_check(r: types.account.Password, password: str) -> types.InputCheckPasswordSRP:

algo = r.current_algo

p_bytes = algo.p

p = btoi(algo.p)

g_bytes = itob(algo.g)

g = algo.g

B_bytes = r.srp_B

B = btoi(B_bytes)

srp_id = r.srp_id

x_bytes = compute_hash(algo, password)

x = btoi(x_bytes)

g_x = pow(g, x, p)

k_bytes = sha256(p_bytes + g_bytes)

k = btoi(k_bytes)

kg_x = (k * g_x) % p

while True:

a_bytes = os.urandom(256)

a = btoi(a_bytes)

A = pow(g, a, p)

A_bytes = itob(A)

u = btoi(sha256(A_bytes + B_bytes))

if u > 0:

break

g_b = (B - kg_x) % p

ux = u * x

a_ux = a + ux

S = pow(g_b, a_ux, p)

S_bytes = itob(S)

K_bytes = sha256(S_bytes)

M1_bytes = sha256(

xor(sha256(p_bytes), sha256(g_bytes))

+ sha256(algo.salt1)

+ sha256(algo.salt2)

+ A_bytes

+ B_bytes

+ K_bytes

)

return types.InputCheckPasswordSRP(srp_id=srp_id, A=A_bytes, M1=M1_bytes)