Wireshark有抓包功能，可以用于流量分析，但是用于某些特殊場合則不具有靈便性蚪腋，這里我們參考了《Python黑帽子編程》這本書耸棒，并改進(jìn)了他荒澡，用于實現(xiàn)一個高性能的TCP代理

基本原理

作為一個代理(參考BurpSuite)，基本的思路應(yīng)該是:

1.接收客戶端的數(shù)據(jù)与殃，處理和編輯单山，發(fā)送給服務(wù)端
2.接收服務(wù)器的數(shù)據(jù)，處理和編輯幅疼，發(fā)送給客戶端

基本的TCP連接示例如下

##Todo: add

異步TCP

TCP會話過程中米奸，隨時可能接收到數(shù)據(jù)，為了提高代理性能爽篷，我們使用異步模式悴晰，該過程中使用epoll(僅限Linux系統(tǒng))功能(Select也可以)來提高整個代理的性能

epoll用法如下:

import select


epoll = select.epoll()
epoll.register(file_number,select.EPOLLIN)
epoll.register(file_number,select.EPOLLOUT)

##設(shè)置相關(guān)file_number為非阻塞
....

events = epoll.poll(TIMEOUT)
#events為一個List[]，成員為tuple(),其數(shù)據(jù)為(file_number,event)

多線程

客戶端的連接可能不止一個逐工，我們需要使用多線程來操作

核心代碼 - 代理handler

###參數(shù)分別為客戶端連接的socket,要連接的遠(yuǎn)程服務(wù)器host和port

def proxy_handler(client_socket,remote_host,remote_port):
    MAXLENGTH = 4096
    TIMEOUT = 300
   
    ##和遠(yuǎn)程服務(wù)器建立連接
    remote_socket= socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    remote_socket.connect((remote_host,remote_port))

    epoll = select.epoll()
    epoll.register(client_socket.fileno(),select.EPOLLIN)
    epoll.register(remote_socket.fileno(),select.EPOLLIN)
    ###向系統(tǒng)注冊epoll事件铡溪，事件為:文件有數(shù)據(jù)傳入

    remote_socket.setblocking(False)
    client_socket.setblocking(False)
    ###設(shè)置非阻塞Socket
  
    flag_loop = True

    while flag_loop:
        # 查詢epoll時間
        events = epoll.poll(TIMEOUT)
        if not events:
            ##返回為空表明連接崩潰，退出循環(huán)
            break

        ###解析相應(yīng)的事件
        for fd, status in events:
            # 客戶端 >> 服務(wù)器
            if fd == client_socket.fileno():
                msg = client_socket.recv(MAXLENGTH)
                if not msg:
                    # Connection closed
                    flag_loop = False
                    break
                print("[*] Received %d bytes from the client" % (len(msg)))

                ##request_handler和下面的response_handler用來審查和修改中間經(jīng)過的數(shù)據(jù)
                msg = request_handler(msg)
                remote_socket.send(msg)
                print("[*] Send %d bytes to the remote" % (len(msg)))

            # 服務(wù)器 >> 客戶端
            elif fd == remote_socket.fileno():
                msg = remote_socket.recv(MAXLENGTH)
                if not msg:
                    # Connection closed
                    flag_loop = False
                    break
                print("[*] Received %d bytes from the remote" % (len(msg)))

                msg = response_handler(msg)
                client_socket.send(msg)
                print("[*] Send %d bytes to the client" % (len(msg)))

    remote_socket.close()
    client_socket.close()

    print("[*] Connection closed")

則接下來考慮輸入多線程