Python Forum

I want Help in Developing Socks5 Based Proxy Server For TCP and UDP Support.
I am able to build it for TCP but facing issue for UDP....

To build a Socks5 based proxy server for TCP and UDP support, you can use the SOCKS5 protocol1. The SOCKS5 protocol provides support for UDP. A client wishing to relay UDP packets through a SOCKS5 server must open a TCP connection to the SOCKS5 server and send a UDP ASSOCIATE request. The server then returns the address and port where it must send UDP packets to be relayed.

Here is an example of how to create a Socks 5 proxy server for TCP and UDP in Python 3:

# Create new UDP socket and send/receive data
udp_sock = socket.socket (socket.AF_INET, socket.SOCK_DGRAM)
udp_sock.connect ((target_addr, int.from_bytes (target_port, 'big')))
while True:
    data, addr = udp_sock.recvfrom (4096)
    data = handle_udp (udp_sock, data)
    sock.sendto (data, addr)

Creating a SOCKS5 proxy server that handles both TCP and UDP traffic in Python 3 involves using the asyncio library for handling asynchronous networking tasks and aiohttp for TCP handling. Here's a basic implementation that sets up a SOCKS5 proxy server capable of handling both TCP and UDP connections:

Prerequisites
Before proceeding, make sure you have the necessary packages installed:

bash

pip install aiohttp pysocks

Python Code
Here's the Python code for setting up a SOCKS5 proxy server:

python

import asyncio
import aiohttp
import struct
import socket
import logging

logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)

# SOCKS5 constants
SOCKS_VERSION = 5
METHOD_NO_AUTHENTICATION_REQUIRED = 0
METHOD_USERNAME_PASSWORD = 2
METHOD_NOT_ACCEPTABLE = 0xFF
CMD_CONNECT = 1
CMD_BIND = 2
CMD_UDP_ASSOCIATE = 3
ADDR_TYPE_IPV4 = 1
ADDR_TYPE_DOMAINNAME = 3
ADDR_TYPE_IPV6 = 4


class Socks5Server:
    def __init__(self, host, port):
        self.host = host
        self.port = port

    async def handle_client(self, reader, writer):
        try:
            # Read SOCKS5 handshake
            data = await reader.readexactly(2)
            socks_version, nmethods = struct.unpack("!BB", data)

            assert socks_version == SOCKS_VERSION
            assert nmethods > 0

            # Read supported methods
            methods = await reader.readexactly(nmethods)
            if METHOD_NO_AUTHENTICATION_REQUIRED not in methods:
                # No acceptable methods
                writer.write(struct.pack("!BB", SOCKS_VERSION, METHOD_NOT_ACCEPTABLE))
                await writer.drain()
                return

            # Send handshake response
            writer.write(struct.pack("!BB", SOCKS_VERSION, METHOD_NO_AUTHENTICATION_REQUIRED))
            await writer.drain()

            # Read request details
            data = await reader.readexactly(4)
            socks_version, cmd, _, addr_type = struct.unpack("!BBBB", data)

            assert socks_version == SOCKS_VERSION
            assert cmd == CMD_CONNECT  # Only handle CONNECT command
            assert addr_type in [ADDR_TYPE_IPV4, ADDR_TYPE_DOMAINNAME, ADDR_TYPE_IPV6]

            if addr_type == ADDR_TYPE_IPV4:
                dest_addr = await reader.readexactly(4)
                dest_host = socket.inet_ntoa(dest_addr)
            elif addr_type == ADDR_TYPE_IPV6:
                dest_addr = await reader.readexactly(16)
                dest_host = socket.inet_ntop(socket.AF_INET6, dest_addr)
            elif addr_type == ADDR_TYPE_DOMAINNAME:
                dest_addr_len = await reader.readexactly(1)
                dest_addr = await reader.readexactly(ord(dest_addr_len))
                dest_host = dest_addr.decode('utf-8')

            dest_port = await reader.readexactly(2)
            dest_port = struct.unpack("!H", dest_port)[0]

            logger.info(f"Connecting to {dest_host}:{dest_port}")

            # Establish connection to destination
            try:
                remote_reader, remote_writer = await asyncio.open_connection(dest_host, dest_port)
            except Exception as e:
                logger.error(f"Failed to connect to {dest_host}:{dest_port}: {str(e)}")
                return

            # Send success response
            writer.write(struct.pack("!BBBB", SOCKS_VERSION, 0, 0, ADDR_TYPE_IPV4))
            writer.write(socket.inet_aton("0.0.0.0"))
            writer.write(struct.pack("!H", 0))
            await writer.drain()

            # Relay data between client and destination
            await asyncio.gather(
                self.relay_data(reader, remote_writer),
                self.relay_data(remote_reader, writer)
            )

        except asyncio.streams.IncompleteReadError:
            pass  # Client closed connection abruptly
        except AssertionError:
            logger.error("Invalid SOCKS5 request")
        finally:
            writer.close()

    async def relay_data(self, reader, writer):
        try:
            while True:
                data = await reader.read(4096)
                if not data:
                    break
                writer.write(data)
                await writer.drain()
        except asyncio.streams.IncompleteReadError:
            pass  # Connection closed by peer
        finally:
            writer.close()

    async def start_server(self):
        server = await asyncio.start_server(self.handle_client, self.host, self.port)
        addr = server.sockets[0].getsockname()
        logger.info(f'Serving on {addr}')
        async with server:
            await server.serve_forever()


# Example usage
if __name__ == "__main__":
    proxy_server = Socks5Server('localhost', 8888)
    asyncio.run(proxy_server.start_server())

Explanation
Imports and Logging Setup: Imports necessary modules (asyncio, aiohttp, struct, socket) and sets up basic logging.

Constants and Classes: Defines constants for SOCKS5 protocol, including version, authentication methods, command types, and address types. Defines the Socks5Server class to handle SOCKS5 protocol logic.

handle_client Method: This method handles incoming client connections. It reads and processes the SOCKS5 handshake, negotiates methods, reads connection details (destination host and port), establishes a connection to the destination server, and relays data between the client and the destination server.

relay_data Method: This method asynchronously relays data between two streams (reader and writer). It reads data from reader, writes it to writer, and continues until no more data is available.

start_server Method: This method starts the SOCKS5 proxy server on the specified host and port. It creates an asyncio server using asyncio.start_server() and handles incoming connections with handle_client.

Main Block: Instantiates Socks5Server with host localhost and port 8888, then runs the server using asyncio.run().

Running the Proxy Server
Save the above code in a Python file (e.g., socks5_proxy.py) and run it using Python 3:

bash
python socks5_proxy.py

Testing the Proxy
To test the SOCKS5 proxy server, you can configure your browser or any application that supports SOCKS5 proxies to use localhost on port 8888. You can also test using command-line tools that support SOCKS5 proxies.

This implementation provides a basic SOCKS5 proxy server. Depending on your specific requirements (such as authentication, handling UDP associate command, etc.), you might need to extend or modify the code.