第5回:Pythonでネットワークプログラミング(TCPプロキシ)

pythonによるプロキシのプログラムです。ほぼ写経ですので、詳しく知りたい方は、参考文献をご参考ください。このプログラムは、プロキシの役割を通りにホスト←→プログラム←→クライアントを実現します。

#!/usr/bin/env python

import sys
import socket
import threading


def server_loop(local_host,local_port,remote_host,remote_port,receive_first):
    server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

    try:
        server.bind((local_host,local_port))
    except:
        print "[!!]Failed to listen on %s:%d" % (local_host,local_port)
        sys.exit(0)

    server.listen(5)


    print "[!!]Listening on %s:%d" % (local_host,local_port)
    while True:
        client_socket, addr = server.accept()

        print "[==>] Received incoming connection from %s:%d" % (addr[0],addr[1])

        proxy_thread = threading.Thread(target=proxy_handler,args=(client_socket,remote_host,remote_port,recevie_first))

        proxy_thread.start()

def main():
    if len(sys.argv[1:]) != 5:
        print "Usage: ./tcp_proxy.py [localhost] [localport] [remotehost] [remoteport] [recive_fisrt]"
        sys.exit(0)

    local_host = sys.argv[1]
    local_port = int(sys.argv[2])

    remote_host = sys.argv[3]
    remote_port = int(sys.argv[4])

    receive_first = sys.argv[5]

    if "True" in receive_first:
        receive_first = True
    else:
        receive_first = False

    server_loop(local_host,local_port,remote_host,remote_port,receive_first)

def proxy_handler(client_socket,remote_host,remote_port,recive_fisrt):
    remote_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    remote_socket.connect((remote_host,remote_port))

    if recevie_first:
        remote_buffer = receive_from(remote_socket)
        hexdump(remote_buffer)

        remote_buffer = response_handler(remote_buffer)

        if len(remote_buffer):
            print "[<==] Sending %d bytes to localhost." % len(remote_buffer)
            client_socket.send(remote_buffer)

    while True:

        local_buffer = receive_from(client_socket)

        if len(local_buffer):

            print "[==>] Received %d bytes from localhost." % len(local_buffer)
            hexdump(local_buffer)
            #パケット書き換えの時に使用
            local_buffer = request_handler(local_buffer)

            remote_socket.send(local_buffer)
            print "[==>] Sent to remote."


        remote_buffer = receive_from(remote_socket)

        if len(remote_buffer):
            print "[==>] Received %d bytes from remote." % len(remote_buffer)
            hexdump(remote_buffer)

            #パケット書き換えの時に使用
            remote_buffer = response_handler(remote_buffer)
            
            #ローカルにソケットを送信する
            client_socket.send(remote_buffer)
            print "[==>] Sent to localhost."

        #データがないときに、コネクションを閉じる。
        if not len(local_buffer) or not len(remote_buffer):
            client_socket.close()
            remote_socket.close()
            print "[*] No more data. Closing connections."

            break


#16進数に変換する。
def hexdump(src,length=16):
    result = []
    digits = 4 if isinstance(src, unicode) else 2
    for i in xrange(0, len(src), length):
        s = src[i:i+length]
        hexa = b' '.join(["%0*X" % (digits, ord(x)) for x in s])
        text = b''.join([x if 0x20 <= ord(x) < 0x7F else b'.' for  x in s])
        result.append( b"%04X %-*s %s" % (i,length*(digits + 1 ),hexa,text))

    print b'\n',join(result)


def receive_from(connection):
    buffer = ""

    #タイムアウト時間を2秒にセット
    conecction.settimeout(2)
    
    try:
        while True:
            data = connection.recv(4096)
            if not data:
                break
            buffer += data
    except:
        pass

    return buffer


#リモートに送るパケットの書き換え用
def request_handler(buffer):
    return buffer

#ローカルに来るパケットの書き換え用
def response_handler(buffer):
    return buffer
                
main()