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[SOCKS4] Packet parser & builder (#1047)
* Initial commit * Parse socks4 packet * Lint check * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * fix lint issues * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Add handler test skeleton * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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‎proxy/socks/__init__.py‎

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# -*- 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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from .client import SocksClientConnection
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from .packet import Socks4Packet
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from .handler import SocksProtocolHandler
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from .operations import Socks4Operations, socks4Operations
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__all__ = [
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'Socks4Packet',
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'socks4Operations',
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'Socks4Operations',
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'SocksProtocolHandler',
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'SocksClientConnection',
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]

‎proxy/socks/client.py‎

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# -*- 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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from ..core.connection import TcpClientConnection
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class SocksClientConnection(TcpClientConnection):
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pass

‎proxy/socks/handler.py‎

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# -*- 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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from typing import Any, Optional
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from .client import SocksClientConnection
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from ..core.base import BaseTcpServerHandler
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class SocksProtocolHandler(BaseTcpServerHandler[SocksClientConnection]):
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"""Reference https://www.openssh.com/txt/socks4.protocol"""
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def __init__(self, *args: Any, **kwargs: Any) -> None:
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super().__init__(*args, **kwargs)
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@staticmethod
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def create(**kwargs: Any) -> SocksClientConnection:
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return SocksClientConnection(**kwargs)
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def handle_data(self, data: memoryview) -> Optional[bool]:
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return super().handle_data(data)

‎proxy/socks/operations.py‎

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# -*- 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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from typing import NamedTuple
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Socks4Operations = NamedTuple(
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'Socks4Operations', [
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('CONNECT', int),
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('BIND', int),
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],
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)
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socks4Operations = Socks4Operations(1, 2)

‎proxy/socks/packet.py‎

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# -*- 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

‎tests/socks/__init__.py‎

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# -*- 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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"""

‎tests/socks/test_handler.py‎

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# -*- 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.
7+
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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 pytest
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from pytest_mock import MockerFixture
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from proxy.socks import SocksProtocolHandler, SocksClientConnection
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from proxy.common.flag import FlagParser
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from ..test_assertions import Assertions
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class TestHttpProtocolHandlerWithoutServerMock(Assertions):
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@pytest.fixture(autouse=True) # type: ignore[misc]
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def _setUp(self, mocker: MockerFixture) -> None:
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self.mock_fromfd = mocker.patch('socket.fromfd')
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self.mock_selector = mocker.patch('selectors.DefaultSelector')
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self.fileno = 10
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self._addr = ('127.0.0.1', 54382)
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self._conn = self.mock_fromfd.return_value
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self.flags = FlagParser.initialize(threaded=True)
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self.handler = SocksProtocolHandler(
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SocksClientConnection(conn=self._conn, addr=self._addr),
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flags=self.flags,
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)
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self.handler.initialize()
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def test(self) -> None:
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self.assertEqual(1, 1)

‎tests/socks/test_packet.py‎

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# -*- 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.
7+
8+
: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 re
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import socket
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import binascii
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import unittest
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from proxy.socks import Socks4Packet, socks4Operations
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def unhexlify(raw: str) -> bytes:
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return binascii.unhexlify(re.sub(r'\s', '', raw))
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# Examples taken from https://en.wikipedia.org/wiki/SOCKS
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CLIENT_CONNECT_REQ = unhexlify('04 01 00 50 42 66 07 63 46 72 65 64 00')
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SERVER_CONNECT_OK = unhexlify('00 5A')
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class TestSocks4Packet(unittest.TestCase):
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def test_pack(self) -> None:
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pkt = Socks4Packet()
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pkt.vn = 4
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pkt.cd = socks4Operations.CONNECT
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pkt.dstport = 80
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pkt.dstip = socket.inet_aton('66.102.7.99')
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pkt.userid = b'Fred'
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self.assertEqual(
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pkt.pack(),
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CLIENT_CONNECT_REQ,
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)
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def test_parse(self) -> None:
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wiki = memoryview(CLIENT_CONNECT_REQ)
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pkt = Socks4Packet()
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pkt.parse(wiki)
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self.assertEqual(pkt.vn, 4)
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self.assertEqual(pkt.cd, socks4Operations.CONNECT)
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self.assertEqual(pkt.dstport, 80)
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assert pkt.dstip
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self.assertEqual(socket.inet_ntoa(pkt.dstip), '66.102.7.99')
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self.assertEqual(pkt.userid, b'Fred')

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