transparent proxy with python

tproxy_upstream.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import socket
import select
import sys

IP_TRANSPARENT = 19
HOST = "0.0.0.0"
PORT = 10

buffer_size = 4096


class TheServer:
    input_list = []
    channel = {}

    def __init__(self, host, port):
        self.server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.server.setsockopt(socket.IPPROTO_IP, IP_TRANSPARENT, 1)
        self.server.bind((host, port))
        self.server.listen(32)

    def forward(self, c_ip, c_port, r_ip, r_port):
        forward = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        forward.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        forward.setsockopt(socket.IPPROTO_IP, IP_TRANSPARENT, 1)
        forward.bind((c_ip, c_port))
        forward.settimeout(5)
        try:
            a = forward.connect((r_ip, r_port))
            print(a)
            return forward
        except Exception as e:
            print(e)
            return False

    def main_loop(self):
        self.input_list.append(self.server)
        while True:
            ss = select.select
            inputready, outputready, exceptready = ss(self.input_list, [], [])
            for s in inputready:
                if s == self.server:
                    self.on_accept()
                    break

                self.data = s.recv(buffer_size)
                if len(self.data) == 0:
                    self.on_close(s)
                    break
                else:
                    self.on_recv(s)

    def on_accept(self):
        clientsock, (c_ip, c_port) = self.server.accept()
        r_ip, r_port = clientsock.getsockname()
        print("[ ] Connection from tcp://%s:%d to tcp://%s:%d" %
              (c_ip, c_port, r_ip, r_port))

        forward = self.forward(c_ip, c_port, r_ip, r_port)
        if forward:
            print("%s:%d has connected" % (c_ip, c_port))
            self.input_list.append(clientsock)
            self.input_list.append(forward)
            self.channel[clientsock] = forward
            self.channel[forward] = clientsock
        else:
            print("Can't establish connection with remote server.")
            print("Closing connection with client side", c_ip, ":", c_port)
            clientsock.close()

    def on_close(self, s):
        print(s.getpeername(), "has disconnected")
        # remove objects from input_list
        self.input_list.remove(s)
        self.input_list.remove(self.channel[s])
        out = self.channel[s]
        # close the connection with client
        self.channel[out].close()  # equivalent to do self.s.close()
        # close the connection with remote server
        self.channel[s].close()
        # delete both objects from channel dict
        del self.channel[out]
        del self.channel[s]

    def on_recv(self, s):
        data = self.data
        # here we can parse and/or modify the data before send forward
        print(data.decode("utf-8"))
        self.channel[s].send(data)


if __name__ == '__main__':
    server = TheServer(HOST, PORT)
    try:
        server.main_loop()
    except KeyboardInterrupt:
        print("Ctrl C - Stopping server")
        sys.exit(1)