mirror of
https://github.com/LonamiWebs/Telethon.git
synced 2026-01-22 16:23:52 +03:00
302a9a8c5f
This partially reverts commit 5a3a94eb51.
It should be re-introduced once the rest of comments are addressed.
Session changes are kept for the future, even if unused for now,
as there may be people who have already upgraded their session.
213 lines
7.7 KiB
Python
213 lines
7.7 KiB
Python
"""
|
|
This module contains several functions that authenticate the client machine
|
|
with Telegram's servers, effectively creating an authorization key.
|
|
"""
|
|
import os
|
|
import time
|
|
from hashlib import sha1
|
|
|
|
from ..tl.types import (
|
|
ResPQ, PQInnerData, ServerDHParamsFail, ServerDHParamsOk,
|
|
ServerDHInnerData, ClientDHInnerData, DhGenOk, DhGenRetry, DhGenFail
|
|
)
|
|
from .. import helpers
|
|
from ..crypto import AES, AuthKey, Factorization, rsa
|
|
from ..errors import SecurityError
|
|
from ..extensions import BinaryReader
|
|
from ..tl.functions import (
|
|
ReqPqMultiRequest, ReqDHParamsRequest, SetClientDHParamsRequest
|
|
)
|
|
|
|
|
|
async def do_authentication(sender):
|
|
"""
|
|
Executes the authentication process with the Telegram servers.
|
|
|
|
:param sender: a connected `MTProtoPlainSender`.
|
|
:return: returns a (authorization key, time offset) tuple.
|
|
"""
|
|
# Step 1 sending: PQ Request, endianness doesn't matter since it's random
|
|
nonce = int.from_bytes(os.urandom(16), 'big', signed=True)
|
|
res_pq = await sender.send(ReqPqMultiRequest(nonce))
|
|
assert isinstance(res_pq, ResPQ), 'Step 1 answer was %s' % res_pq
|
|
|
|
if res_pq.nonce != nonce:
|
|
raise SecurityError('Step 1 invalid nonce from server')
|
|
|
|
pq = get_int(res_pq.pq)
|
|
|
|
# Step 2 sending: DH Exchange
|
|
p, q = Factorization.factorize(pq)
|
|
p, q = rsa.get_byte_array(p), rsa.get_byte_array(q)
|
|
new_nonce = int.from_bytes(os.urandom(32), 'little', signed=True)
|
|
|
|
pq_inner_data = bytes(PQInnerData(
|
|
pq=rsa.get_byte_array(pq), p=p, q=q,
|
|
nonce=res_pq.nonce,
|
|
server_nonce=res_pq.server_nonce,
|
|
new_nonce=new_nonce
|
|
))
|
|
|
|
# sha_digest + data + random_bytes
|
|
cipher_text, target_fingerprint = None, None
|
|
for fingerprint in res_pq.server_public_key_fingerprints:
|
|
cipher_text = rsa.encrypt(fingerprint, pq_inner_data)
|
|
if cipher_text is not None:
|
|
target_fingerprint = fingerprint
|
|
break
|
|
|
|
if cipher_text is None:
|
|
# Second attempt, but now we're allowed to use old keys
|
|
for fingerprint in res_pq.server_public_key_fingerprints:
|
|
cipher_text = rsa.encrypt(fingerprint, pq_inner_data, use_old=True)
|
|
if cipher_text is not None:
|
|
target_fingerprint = fingerprint
|
|
break
|
|
|
|
if cipher_text is None:
|
|
raise SecurityError(
|
|
'Step 2 could not find a valid key for fingerprints: {}'
|
|
.format(', '.join(
|
|
[str(f) for f in res_pq.server_public_key_fingerprints])
|
|
)
|
|
)
|
|
|
|
server_dh_params = await sender.send(ReqDHParamsRequest(
|
|
nonce=res_pq.nonce,
|
|
server_nonce=res_pq.server_nonce,
|
|
p=p, q=q,
|
|
public_key_fingerprint=target_fingerprint,
|
|
encrypted_data=cipher_text
|
|
))
|
|
|
|
assert isinstance(
|
|
server_dh_params, (ServerDHParamsOk, ServerDHParamsFail)),\
|
|
'Step 2.1 answer was %s' % server_dh_params
|
|
|
|
if server_dh_params.nonce != res_pq.nonce:
|
|
raise SecurityError('Step 2 invalid nonce from server')
|
|
|
|
if server_dh_params.server_nonce != res_pq.server_nonce:
|
|
raise SecurityError('Step 2 invalid server nonce from server')
|
|
|
|
if isinstance(server_dh_params, ServerDHParamsFail):
|
|
nnh = int.from_bytes(
|
|
sha1(new_nonce.to_bytes(32, 'little', signed=True)).digest()[4:20],
|
|
'little', signed=True
|
|
)
|
|
if server_dh_params.new_nonce_hash != nnh:
|
|
raise SecurityError('Step 2 invalid DH fail nonce from server')
|
|
|
|
assert isinstance(server_dh_params, ServerDHParamsOk),\
|
|
'Step 2.2 answer was %s' % server_dh_params
|
|
|
|
# Step 3 sending: Complete DH Exchange
|
|
key, iv = helpers.generate_key_data_from_nonce(
|
|
res_pq.server_nonce, new_nonce
|
|
)
|
|
if len(server_dh_params.encrypted_answer) % 16 != 0:
|
|
# See PR#453
|
|
raise SecurityError('Step 3 AES block size mismatch')
|
|
|
|
plain_text_answer = AES.decrypt_ige(
|
|
server_dh_params.encrypted_answer, key, iv
|
|
)
|
|
|
|
with BinaryReader(plain_text_answer) as reader:
|
|
reader.read(20) # hash sum
|
|
server_dh_inner = reader.tgread_object()
|
|
assert isinstance(server_dh_inner, ServerDHInnerData),\
|
|
'Step 3 answer was %s' % server_dh_inner
|
|
|
|
if server_dh_inner.nonce != res_pq.nonce:
|
|
raise SecurityError('Step 3 Invalid nonce in encrypted answer')
|
|
|
|
if server_dh_inner.server_nonce != res_pq.server_nonce:
|
|
raise SecurityError('Step 3 Invalid server nonce in encrypted answer')
|
|
|
|
dh_prime = get_int(server_dh_inner.dh_prime, signed=False)
|
|
g = server_dh_inner.g
|
|
g_a = get_int(server_dh_inner.g_a, signed=False)
|
|
time_offset = server_dh_inner.server_time - int(time.time())
|
|
|
|
b = get_int(os.urandom(256), signed=False)
|
|
g_b = pow(g, b, dh_prime)
|
|
gab = pow(g_a, b, dh_prime)
|
|
|
|
# IMPORTANT: Apart from the conditions on the Diffie-Hellman prime
|
|
# dh_prime and generator g, both sides are to check that g, g_a and
|
|
# g_b are greater than 1 and less than dh_prime - 1. We recommend
|
|
# checking that g_a and g_b are between 2^{2048-64} and
|
|
# dh_prime - 2^{2048-64} as well.
|
|
# (https://core.telegram.org/mtproto/auth_key#dh-key-exchange-complete)
|
|
if not (1 < g < (dh_prime - 1)):
|
|
raise SecurityError('g_a is not within (1, dh_prime - 1)')
|
|
|
|
if not (1 < g_a < (dh_prime - 1)):
|
|
raise SecurityError('g_a is not within (1, dh_prime - 1)')
|
|
|
|
if not (1 < g_b < (dh_prime - 1)):
|
|
raise SecurityError('g_b is not within (1, dh_prime - 1)')
|
|
|
|
safety_range = 2 ** (2048 - 64)
|
|
if not (safety_range <= g_a <= (dh_prime - safety_range)):
|
|
raise SecurityError('g_a is not within (2^{2048-64}, dh_prime - 2^{2048-64})')
|
|
|
|
if not (safety_range <= g_b <= (dh_prime - safety_range)):
|
|
raise SecurityError('g_b is not within (2^{2048-64}, dh_prime - 2^{2048-64})')
|
|
|
|
# Prepare client DH Inner Data
|
|
client_dh_inner = bytes(ClientDHInnerData(
|
|
nonce=res_pq.nonce,
|
|
server_nonce=res_pq.server_nonce,
|
|
retry_id=0, # TODO Actual retry ID
|
|
g_b=rsa.get_byte_array(g_b)
|
|
))
|
|
|
|
client_dh_inner_hashed = sha1(client_dh_inner).digest() + client_dh_inner
|
|
|
|
# Encryption
|
|
client_dh_encrypted = AES.encrypt_ige(client_dh_inner_hashed, key, iv)
|
|
|
|
# Prepare Set client DH params
|
|
dh_gen = await sender.send(SetClientDHParamsRequest(
|
|
nonce=res_pq.nonce,
|
|
server_nonce=res_pq.server_nonce,
|
|
encrypted_data=client_dh_encrypted,
|
|
))
|
|
|
|
nonce_types = (DhGenOk, DhGenRetry, DhGenFail)
|
|
assert isinstance(dh_gen, nonce_types), 'Step 3.1 answer was %s' % dh_gen
|
|
name = dh_gen.__class__.__name__
|
|
if dh_gen.nonce != res_pq.nonce:
|
|
raise SecurityError('Step 3 invalid {} nonce from server'.format(name))
|
|
|
|
if dh_gen.server_nonce != res_pq.server_nonce:
|
|
raise SecurityError(
|
|
'Step 3 invalid {} server nonce from server'.format(name))
|
|
|
|
auth_key = AuthKey(rsa.get_byte_array(gab))
|
|
nonce_number = 1 + nonce_types.index(type(dh_gen))
|
|
new_nonce_hash = auth_key.calc_new_nonce_hash(new_nonce, nonce_number)
|
|
|
|
dh_hash = getattr(dh_gen, 'new_nonce_hash{}'.format(nonce_number))
|
|
if dh_hash != new_nonce_hash:
|
|
raise SecurityError('Step 3 invalid new nonce hash')
|
|
|
|
if not isinstance(dh_gen, DhGenOk):
|
|
raise AssertionError('Step 3.2 answer was %s' % dh_gen)
|
|
|
|
return auth_key, time_offset
|
|
|
|
|
|
def get_int(byte_array, signed=True):
|
|
"""
|
|
Gets the specified integer from its byte array.
|
|
This should be used by this module alone, as it works with big endian.
|
|
|
|
:param byte_array: the byte array representing th integer.
|
|
:param signed: whether the number is signed or not.
|
|
:return: the integer representing the given byte array.
|
|
"""
|
|
return int.from_bytes(byte_array, byteorder='big', signed=signed)
|