mirror of
https://github.com/LonamiWebs/Telethon.git
synced 2024-11-22 09:26:37 +03:00
75a648f438
Some fixes include, in more detail: - Using little over big endianess in some parts - Flagging all the constructor numbers as unsigned - Fixed bugs with factorizer - Implemented TLSharp's RSA
67 lines
2.5 KiB
Python
Executable File
67 lines
2.5 KiB
Python
Executable File
# This file is based on TLSharp
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# https://github.com/sochix/TLSharp/blob/master/TLSharp.Core/Network/TcpMessage.cs
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from zlib import crc32
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from utils.binary_writer import BinaryWriter
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from utils.binary_reader import BinaryReader
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class TcpMessage:
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def __init__(self, seq_number, body):
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"""
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:param seq_number: Sequence number
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:param body: Message body byte array
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"""
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if body is None:
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raise ValueError('body cannot be None')
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self.sequence_number = seq_number
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self.body = body
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def encode(self):
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"""Returns the bytes of the this message encoded, following Telegram's guidelines"""
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with BinaryWriter() as writer:
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''' https://core.telegram.org/mtproto#tcp-transport
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4 length bytes are added at the front
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(to include the length, the sequence number, and CRC32; always divisible by 4)
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and 4 bytes with the packet sequence number within this TCP connection
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(the first packet sent is numbered 0, the next one 1, etc.),
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and 4 CRC32 bytes at the end (length, sequence number, and payload together).
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'''
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writer.write_int(len(self.body) + 12)
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writer.write_int(self.sequence_number)
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writer.write(self.body)
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writer.flush() # Flush so we can get the buffer in the CRC
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# Ensure it's unsigned (see http://stackoverflow.com/a/30092291/4759433)
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crc = crc32(writer.get_bytes()[0:8 + len(self.body)]) & 0xFFFFFFFF
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writer.write_int(crc, signed=False)
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return writer.get_bytes()
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@staticmethod
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def decode(body):
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"""Returns a TcpMessage from the given encoded bytes, decoding them previously"""
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if body is None:
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raise ValueError('body cannot be None')
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if len(body) < 12:
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raise ValueError('Wrong size of input packet')
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with BinaryReader(body) as reader:
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packet_len = int.from_bytes(reader.read(4), byteorder='little')
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if packet_len < 12:
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raise ValueError('Invalid packet length: {}'.format(packet_len))
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seq = reader.read_int()
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packet = reader.read(packet_len - 12)
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checksum = reader.read_int()
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# Ensure it's unsigned (see http://stackoverflow.com/a/30092291/4759433)
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valid_checksum = crc32(body[:packet_len - 4]) & 0xFFFFFFFF
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if checksum != valid_checksum:
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raise ValueError('Invalid checksum, skip')
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return TcpMessage(seq, packet)
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