70 lines
1.9 KiB
Python
70 lines
1.9 KiB
Python
# -*- coding: utf-8 -*-
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"""
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proxy.py
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~~~~~~~~
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⚡⚡⚡ Fast, Lightweight, Pluggable, TLS interception capable proxy server focused on
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Network monitoring, controls & Application development, testing, debugging.
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:copyright: (c) 2013-present by Abhinav Singh and contributors.
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:license: BSD, see LICENSE for more details.
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"""
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import struct
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from typing import Optional
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NULL = b'\x00'
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class Socks4Packet:
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"""SOCKS4 and SOCKS4a protocol parser.
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FIXME: Currently doesn't buffer during parsing and expects
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packet to arrive within a single socket receive event.
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"""
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def __init__(self) -> None:
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# 1 byte, must be equal to 4
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self.vn: Optional[int] = None
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# 1 byte
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self.cd: Optional[int] = None
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# 2 bytes
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self.dstport: Optional[int] = None
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# 4 bytes
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self.dstip: Optional[bytes] = None
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# Variable bytes, NULL terminated
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self.userid: Optional[bytes] = None
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def parse(self, raw: memoryview) -> None:
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cursor = 0
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# Parse vn
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if self.vn is None:
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assert int(raw[cursor]) == 4
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self.vn = 4
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cursor += 1
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# Parse cd
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self.cd = raw[cursor]
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cursor += 1
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# Parse dstport
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self.dstport = struct.unpack('!H', raw[cursor:cursor+2])[0]
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cursor += 2
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# Parse dstip
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self.dstip = struct.unpack('!4s', raw[cursor:cursor+4])[0]
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cursor += 4
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# Parse userid
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ulen = len(raw) - cursor - 1
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self.userid = struct.unpack(
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'!%ds' % ulen, raw[cursor:cursor+ulen],
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)[0]
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cursor += ulen
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# Assert null terminated
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assert raw[cursor] == NULL[0]
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def pack(self) -> bytes:
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user_id = self.userid or b''
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return struct.pack(
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'!bbH4s%ds' % len(user_id),
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self.vn, self.cd,
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self.dstport, self.dstip,
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user_id,
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) + NULL
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