86 lines
3.2 KiB
Python
86 lines
3.2 KiB
Python
# Pyrogram - Telegram MTProto API Client Library for Python
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# Copyright (C) 2017-2018 Dan Tès <https://github.com/delivrance>
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#
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# This file is part of Pyrogram.
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#
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# Pyrogram is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Lesser General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# Pyrogram is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public License
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# along with Pyrogram. If not, see <http://www.gnu.org/licenses/>.
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from hashlib import sha256
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from io import BytesIO
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from os import urandom
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from pyrogram.raw.core import Message, Long
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from . import aes
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def kdf(auth_key: bytes, msg_key: bytes, outgoing: bool) -> tuple:
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# https://core.telegram.org/mtproto/description#defining-aes-key-and-initialization-vector
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x = 0 if outgoing else 8
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sha256_a = sha256(msg_key + auth_key[x: x + 36]).digest()
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sha256_b = sha256(auth_key[x + 40:x + 76] + msg_key).digest() # 76 = 40 + 36
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aes_key = sha256_a[:8] + sha256_b[8:24] + sha256_a[24:32]
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aes_iv = sha256_b[:8] + sha256_a[8:24] + sha256_b[24:32]
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return aes_key, aes_iv
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def pack(message: Message, salt: int, session_id: bytes, auth_key: bytes, auth_key_id: bytes) -> bytes:
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data = Long(salt) + session_id + message.write()
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padding = urandom(-(len(data) + 12) % 16 + 12)
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# 88 = 88 + 0 (outgoing message)
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msg_key_large = sha256(auth_key[88: 88 + 32] + data + padding).digest()
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msg_key = msg_key_large[8:24]
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aes_key, aes_iv = kdf(auth_key, msg_key, True)
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return auth_key_id + msg_key + aes.ige256_encrypt(data + padding, aes_key, aes_iv)
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def unpack(b: BytesIO, session_id: bytes, auth_key: bytes, auth_key_id: bytes) -> Message:
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assert b.read(8) == auth_key_id, b.getvalue()
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msg_key = b.read(16)
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aes_key, aes_iv = kdf(auth_key, msg_key, False)
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data = BytesIO(aes.ige256_decrypt(b.read(), aes_key, aes_iv))
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data.read(8)
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# https://core.telegram.org/mtproto/security_guidelines#checking-session-id
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assert data.read(8) == session_id
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try:
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message = Message.read(data)
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except KeyError as e:
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if e.args[0] == 0:
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raise ConnectionError(f"Received empty data. Check your internet connection.")
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left = data.read().hex()
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left = [left[i:i + 64] for i in range(0, len(left), 64)]
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left = [[left[i:i + 8] for i in range(0, len(left), 8)] for left in left]
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left = "\n".join(" ".join(x for x in left) for left in left)
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raise ValueError(f"The server sent an unknown constructor: {hex(e.args[0])}\n{left}")
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# https://core.telegram.org/mtproto/security_guidelines#checking-sha256-hash-value-of-msg-key
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# https://core.telegram.org/mtproto/security_guidelines#checking-message-length
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# 96 = 88 + 8 (incoming message)
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assert msg_key == sha256(auth_key[96:96 + 32] + data.getvalue()).digest()[8:24]
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# https://core.telegram.org/mtproto/security_guidelines#checking-msg-id
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assert message.msg_id % 2 != 0
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return message
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