proxy.py

#!/usr/bin/env python3

import sys
import socket
import threading

HEX_FILTER = ''.join(
	[(len(repr(chr(i))) == 3) and chr(i) or '.' for i in range (256)])

def hexdump(src, length=16, show=True):
	if isinstance(src, bytes):
		src = src.decode()

	results = list()
	for i in range(0, len(src), length):
		word = str(src[i:i+length])

		printable = word.translate(HEX_FILTER)
		hexa = ' '.join([f'{ord(c):02x}' for c in word])
		hexwidth = length*3
		results.append(f'{i:04x} {hexa:<{hexwidth}} {printable}')
	if show:
		for line in results:
			print(line)
	else:
		return results

# hexdump("python rocks\n and proxies roll\n")

def receive_from(connection):
	buffer = b""
	connection.settimeout(5)
	try:
		while True:
			data = connection.recv(4096)
			if not data:
				break
			buffer += data
	except Exception as e:
		pass
	return buffer

def request_handler(buffer):
	# perform packet modifications
	return buffer

def response_handler(buffer):
	# perform packet modifications
	return buffer

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

	if receive_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):
			line = ("[==>] Received %d bytes from localhost." % len(local_buffer))
			print(line)
			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 localhost.")

		if not len(local_buffer) or not len(remote_buffer):
			client_socket.close()
			remote_socket.close()
			print("[*] No more data. Closing conenctions.")
			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 Exception as e:
		print("problem on bind: %r" % e)
		
		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 out the local connection information
		line ="> Received incoming connection from %s:%d" %(addr[0],addr[1])
		print(line)
		# Start the thread to talk to the remote host
		proxy_thread = threading.Thread(
			target=proxy_handler,
			args=(client_socket, remote_host, remote_port, receive_first))
		proxy_thread.start()

def main():
	if len(sys.argv[1:]) !=5:
		print("Usage: ./proxy.py [localhost] [localport] ", end='')
		print("[remotehost] [remoteport] [receive_first]")
		print("Example: ./proxy.py 127.0.0.1 9000 10.12.132.1 900 True ")
		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)

if __name__ == '__main__':
	main()