166 lines
6.4 KiB
Python
166 lines
6.4 KiB
Python
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"""
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This module holds several utilities regarding RSA and server fingerprints.
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"""
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import os
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import struct
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from hashlib import sha1
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try:
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import rsa
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import rsa.core
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except ImportError:
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rsa = None
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raise ImportError('Missing module "rsa", please install via pip.')
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from ..tl import TLObject
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# {fingerprint: (Crypto.PublicKey.RSA._RSAobj, old)} dictionary
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_server_keys = {}
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def get_byte_array(integer):
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"""Return the variable length bytes corresponding to the given int"""
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# Operate in big endian (unlike most of Telegram API) since:
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# > "...pq is a representation of a natural number
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# (in binary *big endian* format)..."
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# > "...current value of dh_prime equals
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# (in *big-endian* byte order)..."
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# Reference: https://core.telegram.org/mtproto/auth_key
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return int.to_bytes(
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integer,
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(integer.bit_length() + 8 - 1) // 8, # 8 bits per byte,
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byteorder='big',
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signed=False
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)
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def _compute_fingerprint(key):
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"""
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Given a RSA key, computes its fingerprint like Telegram does.
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:param key: the Crypto.RSA key.
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:return: its 8-bytes-long fingerprint.
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"""
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n = TLObject.serialize_bytes(get_byte_array(key.n))
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e = TLObject.serialize_bytes(get_byte_array(key.e))
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# Telegram uses the last 8 bytes as the fingerprint
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return struct.unpack('<q', sha1(n + e).digest()[-8:])[0]
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def add_key(pub, *, old):
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"""Adds a new public key to be used when encrypting new data is needed"""
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global _server_keys
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key = rsa.PublicKey.load_pkcs1(pub)
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_server_keys[_compute_fingerprint(key)] = (key, old)
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def encrypt(fingerprint, data, *, use_old=False):
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"""
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Encrypts the given data known the fingerprint to be used
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in the way Telegram requires us to do so (sha1(data) + data + padding)
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:param fingerprint: the fingerprint of the RSA key.
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:param data: the data to be encrypted.
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:param use_old: whether old keys should be used.
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:return:
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the cipher text, or None if no key matching this fingerprint is found.
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"""
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global _server_keys
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key, old = _server_keys.get(fingerprint, [None, None])
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if (not key) or (old and not use_old):
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return None
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# len(sha1.digest) is always 20, so we're left with 255 - 20 - x padding
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to_encrypt = sha1(data).digest() + data + os.urandom(235 - len(data))
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# rsa module rsa.encrypt adds 11 bits for padding which we don't want
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# rsa module uses rsa.transform.bytes2int(to_encrypt), easier way:
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payload = int.from_bytes(to_encrypt, 'big')
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encrypted = rsa.core.encrypt_int(payload, key.e, key.n)
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# rsa module uses transform.int2bytes(encrypted, keylength), easier:
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block = encrypted.to_bytes(256, 'big')
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return block
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# Add default keys
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# https://github.com/DrKLO/Telegram/blob/a724d96e9c008b609fe188d122aa2922e40de5fc/TMessagesProj/jni/tgnet/Handshake.cpp#L356-L436
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for pub in (
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAruw2yP/BCcsJliRoW5eBVBVle9dtjJw+OYED160Wybum9SXtBBLX
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riwt4rROd9csv0t0OHCaTmRqBcQ0J8fxhN6/cpR1GWgOZRUAiQxoMnlt0R93LCX/
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j1dnVa/gVbCjdSxpbrfY2g2L4frzjJvdl84Kd9ORYjDEAyFnEA7dD556OptgLQQ2
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e2iVNq8NZLYTzLp5YpOdO1doK+ttrltggTCy5SrKeLoCPPbOgGsdxJxyz5KKcZnS
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Lj16yE5HvJQn0CNpRdENvRUXe6tBP78O39oJ8BTHp9oIjd6XWXAsp2CvK45Ol8wF
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XGF710w9lwCGNbmNxNYhtIkdqfsEcwR5JwIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAvfLHfYH2r9R70w8prHblWt/nDkh+XkgpflqQVcnAfSuTtO05lNPs
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pQmL8Y2XjVT4t8cT6xAkdgfmmvnvRPOOKPi0OfJXoRVylFzAQG/j83u5K3kRLbae
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7fLccVhKZhY46lvsueI1hQdLgNV9n1cQ3TDS2pQOCtovG4eDl9wacrXOJTG2990V
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jgnIKNA0UMoP+KF03qzryqIt3oTvZq03DyWdGK+AZjgBLaDKSnC6qD2cFY81UryR
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WOab8zKkWAnhw2kFpcqhI0jdV5QaSCExvnsjVaX0Y1N0870931/5Jb9ICe4nweZ9
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kSDF/gip3kWLG0o8XQpChDfyvsqB9OLV/wIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAs/ditzm+mPND6xkhzwFIz6J/968CtkcSE/7Z2qAJiXbmZ3UDJPGr
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zqTDHkO30R8VeRM/Kz2f4nR05GIFiITl4bEjvpy7xqRDspJcCFIOcyXm8abVDhF+
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th6knSU0yLtNKuQVP6voMrnt9MV1X92LGZQLgdHZbPQz0Z5qIpaKhdyA8DEvWWvS
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Uwwc+yi1/gGaybwlzZwqXYoPOhwMebzKUk0xW14htcJrRrq+PXXQbRzTMynseCoP
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Ioke0dtCodbA3qQxQovE16q9zz4Otv2k4j63cz53J+mhkVWAeWxVGI0lltJmWtEY
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K6er8VqqWot3nqmWMXogrgRLggv/NbbooQIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAvmpxVY7ld/8DAjz6F6q05shjg8/4p6047bn6/m8yPy1RBsvIyvuD
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uGnP/RzPEhzXQ9UJ5Ynmh2XJZgHoE9xbnfxL5BXHplJhMtADXKM9bWB11PU1Eioc
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3+AXBB8QiNFBn2XI5UkO5hPhbb9mJpjA9Uhw8EdfqJP8QetVsI/xrCEbwEXe0xvi
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fRLJbY08/Gp66KpQvy7g8w7VB8wlgePexW3pT13Ap6vuC+mQuJPyiHvSxjEKHgqe
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Pji9NP3tJUFQjcECqcm0yV7/2d0t/pbCm+ZH1sadZspQCEPPrtbkQBlvHb4OLiIW
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PGHKSMeRFvp3IWcmdJqXahxLCUS1Eh6MAQIDAQAB
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-----END RSA PUBLIC KEY-----''',
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):
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add_key(pub, old=False)
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for pub in (
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAwVACPi9w23mF3tBkdZz+zwrzKOaaQdr01vAbU4E1pvkfj4sqDsm6
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lyDONS789sVoD/xCS9Y0hkkC3gtL1tSfTlgCMOOul9lcixlEKzwKENj1Yz/s7daS
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an9tqw3bfUV/nqgbhGX81v/+7RFAEd+RwFnK7a+XYl9sluzHRyVVaTTveB2GazTw
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Efzk2DWgkBluml8OREmvfraX3bkHZJTKX4EQSjBbbdJ2ZXIsRrYOXfaA+xayEGB+
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8hdlLmAjbCVfaigxX0CDqWeR1yFL9kwd9P0NsZRPsmoqVwMbMu7mStFai6aIhc3n
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Slv8kg9qv1m6XHVQY3PnEw+QQtqSIXklHwIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAxq7aeLAqJR20tkQQMfRn+ocfrtMlJsQ2Uksfs7Xcoo77jAid0bRt
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ksiVmT2HEIJUlRxfABoPBV8wY9zRTUMaMA654pUX41mhyVN+XoerGxFvrs9dF1Ru
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vCHbI02dM2ppPvyytvvMoefRoL5BTcpAihFgm5xCaakgsJ/tH5oVl74CdhQw8J5L
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xI/K++KJBUyZ26Uba1632cOiq05JBUW0Z2vWIOk4BLysk7+U9z+SxynKiZR3/xdi
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XvFKk01R3BHV+GUKM2RYazpS/P8v7eyKhAbKxOdRcFpHLlVwfjyM1VlDQrEZxsMp
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NTLYXb6Sce1Uov0YtNx5wEowlREH1WOTlwIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAsQZnSWVZNfClk29RcDTJQ76n8zZaiTGuUsi8sUhW8AS4PSbPKDm+
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DyJgdHDWdIF3HBzl7DHeFrILuqTs0vfS7Pa2NW8nUBwiaYQmPtwEa4n7bTmBVGsB
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1700/tz8wQWOLUlL2nMv+BPlDhxq4kmJCyJfgrIrHlX8sGPcPA4Y6Rwo0MSqYn3s
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g1Pu5gOKlaT9HKmE6wn5Sut6IiBjWozrRQ6n5h2RXNtO7O2qCDqjgB2vBxhV7B+z
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hRbLbCmW0tYMDsvPpX5M8fsO05svN+lKtCAuz1leFns8piZpptpSCFn7bWxiA9/f
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x5x17D7pfah3Sy2pA+NDXyzSlGcKdaUmwQIDAQAB
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-----END RSA PUBLIC KEY-----''',
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'''-----BEGIN RSA PUBLIC KEY-----
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MIIBCgKCAQEAwqjFW0pi4reKGbkc9pK83Eunwj/k0G8ZTioMMPbZmW99GivMibwa
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xDM9RDWabEMyUtGoQC2ZcDeLWRK3W8jMP6dnEKAlvLkDLfC4fXYHzFO5KHEqF06i
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qAqBdmI1iBGdQv/OQCBcbXIWCGDY2AsiqLhlGQfPOI7/vvKc188rTriocgUtoTUc
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/n/sIUzkgwTqRyvWYynWARWzQg0I9olLBBC2q5RQJJlnYXZwyTL3y9tdb7zOHkks
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WV9IMQmZmyZh/N7sMbGWQpt4NMchGpPGeJ2e5gHBjDnlIf2p1yZOYeUYrdbwcS0t
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UiggS4UeE8TzIuXFQxw7fzEIlmhIaq3FnwIDAQAB
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-----END RSA PUBLIC KEY-----''',
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):
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add_key(pub, old=True)
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