proxy.py

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
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("[==>] Send 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 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 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 a 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 9000 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()