#!/usr/bin/env python
# coding=utf-8

import sys
import socket
import threading


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 = ""

    #我们设置了两秒的超时，这取决与目标的情况，可能需要调整
    connection.settimeout(2)

    try:
        #持续从缓存中读取数据直到没有数据或者超时
        while True:
            data = connection.recv(4096)
            if not data:
                break
            buffer += data
    except:
        pass #pass是句空语句，是为了保持程序结构的完整性，防止报错

    return buffer


#对目标是远程主机的请求进行修改
def request_handler(buffer):
    #执行包修改
    return buffer


#对目标是本地主机的响应进行修改
def response_handler(buffer):
    #执行包修改
    return buffer


def proxy_handler(client_socket, remote_host, remote_port, receive_first):
    # 连接远程主机
    remote_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    remote_socket.connect((remote_host, remote_port))

    # 如果必要从远程主机接收数据
    if receive_first:
        remote_buffer = receive_from(remote_socket)
        hexdump(remote_buffer)

        #发送给我们的相应处理
        remote_buffer = response_handler(remote_buffer)

        #如果我们有数据传递给本地客户端，发送它
        if len(remote_buffer):
            print "[<==]Sending %d bytes to localhost." % len(remote_buffer)
            client_socket.send(remote_buffer)


    #现在我们从本地循环读取数据，发送给远程主机和本地主机
    while True:

        #从本地读取数据
        local_buffer = receive_from(client_socket)

        if len(local_buffer):
            print "[==]Received %d bytes from localhost" % len(local_buffer)
            hexdump(local_buffer)

            #发送给我们的本地请求
            local_buffer = request_handler(local_buffer)

            #向远程主机发送数据
            remote_socket.send(local_buffer)
            print "[==>]Sent to remote."

        # 接受响应的数据
        remote_buffer = receive_from(remote_socket)

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

            #发送到响应处理函数
            remote_buffer = response_handler(remote_buffer)

            #将响应发送给本地socket
            client_socket.send(remote_buffer)

            print "[<==]Sent to localhost."

        #如果两边都没有数据，关闭连接
        if not len(local_buffer) or not len(remote_buffer):
            client_socket.close()
            remote_socket.close()
            print "[*]No more data. Closing connections."

            break


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)
        print "[!!]Check for other listening sockets or correct permissions."
        sys.exit(0)

    print "[*]Listening on %s：%d" % (local_host, local_port)

    server.listen(5)

    while True:
        client_socket, addr = server.accept()

        # 打印出本地连接信息
        print "[==>]Received incoming connecting from %s:%d" % (addr[0], addr[1])
        # 开启一个线程与远程主机通信
        proxy_thread = threading.Thread(target=proxy_handler,
                                        args=(client_socket, remote_host, remote_port, receive_first))
        proxy_thread.start()


def main():
    # 没有华丽的命令行解析
    if len(sys.argv[1:]) != 5:
        print "Usage:./tcpProxy.py [localhost] [localport] [remoterhost] [remoteport] [receive_first]"
        print "Example:./tcpProxy.py 127.0.0.1 9000 10.12.132.1 9000 True"
        sys.exit(0)

    # 设置本地监听参数
    local_host = sys.argv[1]
    local_port = int(sys.argv[2])

    # 设置远程目标
    remote_host = sys.argv[3]
    remote_port = int(sys.argv[4])

    # 告诉代理发送给远程主机之前连接和接受数据
    receive_first = sys.argv[5]

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

    # 现在设置好我们的监听socket
    server_loop(local_host, local_port, remote_host, remote_port, receive_first)


# 调用main函数
main()
