python黑帽之TCP代理proxy(chapter1）

周日花了大概3-4个小时把代码巧了遍，理解了下。做完前面的netcat理解大致原理和流程就不难了。不过要期末考试了，我就不费心费力去调代码了，里面肯定有很多bug。。以我先前对netcat的代码调试经验来看。

核心就一个，中间代理上两个socket，一个和远程主机通信，一个和本地客户端通信，就这么简单。代码献上，有兴趣的朋友可以试着调试下。

import sys
import socket
import threading

#打开server端口，listen,处理传进来的数据
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('[==>] Received incoming connection from %s:%d'%(addr[0],addr[1]))
		proxy_thread = threading.Thread(target = proxy_handler,args = (client_socket,remote_host,remote_port,receive_first))
		proxy_thread.start()

#这个函数定义了代理服务器的主要处理方法
def proxy_handler(client_socket,remote_host,remote_port,receive_first):
	#连接上远程主机
	remote_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
	remote_socket.connect((remote_host,remote_port))
	#如果receive_first为true说明要先从远程主机接收数据
	if receive_first:
		remote_buffer = receive_from(remote_socket)
		#看一看远程主机过来的内容有没有想要的东西^_^偷窥下
		hexdump(remote_buffer)
		#将接收到的数据处理下
		remote_buffer = response_handler(remote_buffer)
		#remote_buffer处理过后长度不为0说明要把数据传给客户端
		if len(remote_buffer):
			print('[<==] Sending %d bytes to local_host.'%len(remote_buffer))
			client_socket.send(remote_buffer)
	#不断地接收来自远程主机和客户端的信息然后发送给对方
	while True:
		local_buffer = receive_from(client_socket)
		if len(local_buffer):
			print('[==>] Received %d bites from local_host.'%len(local_buffer))
			hexdump(local_buffer)
			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)
			remote_buffer = response_handler(remote_buffer)
			client_socket.send(remote_buffer)
			print('[<== Sent to local_host]')
		#两边都没有数据，关闭连接，我怀疑这里会出问题
		if not len(local_buffer) or not len(remote_buffer):
			client_socket.close()
			remote_buffer.close()
			print('[*] No more data. Closing connections.')
			
			break

#这个函数不大懂意思，后面仔细研究下
def hexdump(src,length = 16):
	result = []
	digits = 4 if isinstance(src,unincode) else 2 #我的理解是中文4，外文2
	#xrange不会直接生成list，而是生成一个对象，要用的时候再去调用对象里面的东西
	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 = ''
	#设置两秒超时
	connection.settimeout(2)
	try:
		while True:
			data = connection.recv(4096)
			if not data:
				break
			buffer += data
	except:
		pass
	return buffer

#定义远程和本地主机消息处理函数，这里没有需要，不做操作
def request_handler(buffer):
	return(buffer)
def response_handler(buffer):
	return(buffer)
		
def main():
	#从命令行读入参数，如果数目不对则报错
	if len(sys.argv(1:)) != 5:
		print('Usage: python tcp_proxy.py [local_host] [local_port] [remote_host] [remote_port] [receive_first]')
		print('Example: python tcp_proxy.py 127.0.0.1')
		sys.exit(0)
	
	#设置监听参数
	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])
	
	#告诉代理在发送数据前接收连接和接收数据，不大懂，先存疑
	receive_first = sys.argv[5]
	if 'True' in receive_first:
		receive_first = True
	else:
		receive_first = False
	#开始监听，然后代理开始工作！
	server_loop(local_host,local_port,remote_host,remote_port,receive_first)

main()