TCP代理不僅可以將流量從一個主機轉發給另一個主機，而且可以評估基於網路的軟體。在企業級環境下進行滲透測試時，你會經常遇到無法使用Wireshark的情況，無法再Windows系統上載入驅動嗅探本地流量，分段的網路也阻止你使用工具直接嗅探目標主機。作者經常在實際案例中部署簡單的TCP代理以瞭解未知的協議，修改傳送到應用的資料包，或者為模糊測試建立一個測試環境。

程式碼如下：

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)
        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()
        
        # print the connected data of local
        print "[==>] Received incoming connection from %s:%d" % (addr[0],addr[1])
        
        # open a thread to connect with computer
        proxy_thread = threading.Thread(target=proxy_handler,args=(client_socket,remote_host,remote_port,receive_first))
        
        
        proxy_thread.start()
        

def proxy_handler(client_socket, remote_host,remote_port,receive_first):
    
    # connect the computer
    remote_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    
    remote_socket.connect((remote_host,remote_port))
    
    
    # get data from computer
    if receive_first:
        
        remote_buffer = receive_from(remote_socket)
        hexdump(remote_buffer)
        
        
        # handler the things that had been sent
        remote_buffer = response_handler(remote_buffer)
        
        
        # send the data if we hava to send to client
        if len(remote_buffer):
            print "[<==] Sending %d bytes to localhost." % len(remote_buffer)
            client_socket.send(remote_buffer)
            
        
        # read the data from local, then send to localhost and host
        while True:
            
            # get data from local
            local_buffer = receive_from(client_socket)
            
            
            
            if len(local_buffer):
                
                print "[<==] Received %d bytes from localhost." % len(local_buffer)
                hexdump(local_buffer)
                
                # send to local
                local_buffer = request_handler(local_buffer)
                
                # send to computer
                remote_socket.send(local_buffer)
                print "[==>] Sent to remote."
                
                
            # get the data that answer
            remote_buffer = receive_from(remote_socket)
            
            if len(remote_buffer):
                print "[<==] Received %d bytes from remote." % len(remote_buffer)
                hexdump(remote_buffer) 
                
                
                # send to response to handle the data
                remote_buffer = response_handler(remote_buffer)
		
		client_socket.send(remote_buffer)
                
                print "[==>] Sent to localhost."
        
            if not len(local_buffer) or not len(remote_buffer):
                client_socket.close()
                remote_socket.close()
                
                print "[*] No more data. Closing connections."
                
                
                break
    

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 = ""
    
    connection.settimeout(2)
        
    try:
            
            while True:
                data = connection.recv(4096)
                
                if not data:
                    break
                
                
                buffer += data
                
    except:
	pass
        
        
    return buffer
    
def request_handler(buffer):
    return buffer


def response_handler(buffer):
    return buffer


def main():
        
    # no fancy command line parsing here
    if len(sys.argv[1:]) != 5:
        print "Usage: ./proxy.py [localhost] [localport] [remotehost] [remoteport] [receive_first]"
        print "Example: ./proxy.py 127.0.0.1 9000 10.12.132.1 9000 True"
        sys.exit(0)
    
    # setup local listening parameters
    local_host  = sys.argv[1]
    local_port  = int(sys.argv[2])
    
    # setup remote target
    remote_host = sys.argv[3]
    remote_port = int(sys.argv[4])
    
    # this tells our proxy to connect and receive data
    # before sending to the remote host
    receive_first = sys.argv[5]
    
    if "True" in receive_first:
	    receive_first = True
    else:
	    receive_first = False
	    
    
    # now spin up our listening socket
    server_loop(local_host,local_port,remote_host,remote_port,receive_first)
    
    
main()
 

書上的測試程式碼是：

[email protected]:~# sudo python ./proxy.py 127.0.0.1 21 ftp.target.ca 21 True
[*] Listening on 127.0.0.1:21

一直沒反應，書上說的是，需要將代理指向真實的FTP伺服器，這樣才能獲得實際的響應。

之後搜尋了一番，在另一個博主這看到了別的測試方法。

在終端輸入以上句子後，在瀏覽器開啟百度，就會有反饋資料：

但是一開始開啟瀏覽器不會有迴應，因為還沒把埠設定為80，按照以下步驟設定，可以得到結果：