def __call__(self, body: Object) -> Message:
return Message(
body,
MsgId(),
self.seq_no(type(body) not in not_content_related),
len(body)
)
def pack(self, message: Message):
data = Long(self.current_salt.salt) + self.session_id + message.write()
padding = urandom(-(len(data) + 12) % 16 + 12)
# 88 = 88 + 0 (outgoing message)
msg_key_large = sha256(self.auth_key[88: 88 + 32] + data + padding).digest()
msg_key = msg_key_large[8:24]
aes_key, aes_iv = KDF(self.auth_key, msg_key, True)
return self.auth_key_id + msg_key + AES.ige_encrypt(data + padding, aes_key, aes_iv)
def pack(message: Message, salt: int, session_id: bytes, auth_key: bytes,
auth_key_id: bytes) -> bytes:
data = Long(salt) + session_id + message.write()
padding = urandom(-(len(data) + 12) % 16 + 12)
# 88 = 88 + 0 (outgoing message)
msg_key_large = sha256(auth_key[88:88 + 32] + data + padding).digest()
msg_key = msg_key_large[8:24]
aes_key, aes_iv = KDF(auth_key, msg_key, True)
return auth_key_id + msg_key + AES.ige256_encrypt(
data + padding, aes_key, aes_iv)
def pack(self, message: Message):
data = Long(self.current_salt.salt) + self.session_id + message.write()
# MTProto 2.0 requires a minimum of 12 padding bytes.
# I don't get why it says up to 1024 when what it actually needs after the
# required 12 bytes is just extra 0..15 padding bytes for aes
# TODO: It works, but recheck this. What's the meaning of 12..1024 padding bytes?
padding = urandom(-(len(data) + 12) % 16 + 12)
# 88 = 88 + 0 (outgoing message)
msg_key_large = sha256(self.auth_key[88:88 + 32] + data +
padding).digest()
msg_key = msg_key_large[8:24]
aes_key, aes_iv = KDF(self.auth_key, msg_key, True)
return self.auth_key_id + msg_key + IGE.encrypt(
data + padding, aes_key, aes_iv)
def unpack(self, b: BytesIO) -> Message:
assert b.read(8) == self.auth_key_id, b.getvalue()
msg_key = b.read(16)
aes_key, aes_iv = KDF(self.auth_key, msg_key, False)
data = BytesIO(AES.ige_decrypt(b.read(), aes_key, aes_iv))
data.read(8)
# https://core.telegram.org/mtproto/security_guidelines#checking-session-id
assert data.read(8) == self.session_id
message = Message.read(data)
# https://core.telegram.org/mtproto/security_guidelines#checking-sha256-hash-value-of-msg-key
# https://core.telegram.org/mtproto/security_guidelines#checking-message-length
# 96 = 88 + 8 (incoming message)
assert msg_key == sha256(self.auth_key[96:96 + 32] + data.getvalue()).digest()[8:24]
# https://core.telegram.org/mtproto/security_guidelines#checking-msg-id
# TODO: check for lower msg_ids
assert message.msg_id % 2 != 0
return message