Python 100 project #23: NC with Python3

This project is a starting point for networking tweak with python3. I found there are quite a good tutorial and books around python2 regarding network wrangling, but I thought lots of them are not updated for the use with python3. At first, I just made a small modification of netcat on python2, and made it run with python3.


Output Example:

$ python3 -t localhost -p 9999
<BHP:#> pwd

<BHP:#> curl
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    12  100    12    0     0  10869      0 --:--:-- --:--:-- --:--:-- 12000 


Here is the code:

# this is the practice from "Blackk Hat Python"
import sys
import socket
import getopt
import threading
import subprocess

listen = False
command = False
upload = False
execute = ""
target = ""
upload_destination = ""
port = 0

def usage():
    print("BHP Net Tool\n"
          "Usage: -t target_host -p port\n"
          "-l --listen               - listen on [host]:[port] for incoming connections\n"
          "-e --execute=file_to_run  - execute the given file upon receiving a connection\n"
          "-c --command              - initialize a command shell\n"
          "-u --upload=destination   - upon receiving connection upload file and write to [destination]\n"
          "Example: "
          " -t -p 5555 -l -c\n"
          " -t -p 5555 -l -u=c:\\target.exe\n"
          " -t -p 5555 -l -e=\"cat /etc/passwd\"\n"
          "echo 'ABCDEFGHI' | ./ -t -p 135\n"

def main():
    global listen
    global port
    global execute
    global command
    global upload_destination
    global target

    if not len(sys.argv[1:]):

        opts, args = getopt.getopt(sys.argv[1:], "hle:t:p:cu",
                                   ["help", "listen", "execute", "target", "port", "command", "upload"])
    except getopt.GetoptError as err:

    for o,a in opts:
        if o in ("-h", "--help"):
        elif o in ("-l", "--listen"):
            listen = True
        elif o in ("-e", "--execute"):
            execute = a
        elif o in ("-c", "--commandshell"):
            command = True
        elif o in ("-u", "--upload"):
            upload_destination = a
        elif o in ("-t", "--target"):
            target = a
        elif o in ("-p", "--port"):
            port = int(a)
            assert False, "Unhandled Option"

    # are we going to listen or just send data from stdin?
    if not listen and len(target) and port > 0:

        # read in the buffer from the commandline
        # this will block, so send CTRL-D if not sending input
        # to stdin
        buffer =

        # send data off

    # we are going to listen and potentially upload things, execute commands, and drop a shell back
    # depending on our command line options above
    if listen:

def client_sender(buffer):

    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

        # connect to our target host
        client.connect((target, port))

        if len(buffer):

        while True:

            # now wait for data back
            recv_len = 1
            response = b""

            while recv_len:

                data = client.recv(4096)
                recv_len = len(data)
                response += data

                if recv_len < 4096:

            print(str(response, 'utf-8'), end="")

            # wait for more input
            buffer = input("").encode('utf-8')
            buffer += b"\n"

            # send it off
        print("[*] Exception! Exiting.")

        # tear down the connection

def server_loop():
    global target

    # if no target is defined, we listen on all interfaces
    if not len(target):
        target = ""

    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server.bind((target, port))

    while True:
        client_socket, addr = server.accept()

        # spin off a thread to handle our new client
        client_thread = threading.Thread(target=client_handler, args=(client_socket,))

def run_command(command):

    # trim the newline
    command = command.rstrip()

    # run the command and get the output back
        output = subprocess.check_output(command, stderr=subprocess.STDOUT, shell=True)
        output = "Failed to execute command.\r\n"

    # send the output back to the client
    return output

def client_handler(client_socket):
    global upload
    global execute
    global command

    # check for upload
    if len(upload_destination):

        # read in all of the bytes and write to our destination
        file_buffer = ""

        # keep reading data until none is available
        while True:
            data = client_socket.recv(1024)

            if not data:
                file_buffer += data

        # now we take these bytes and try to write them out
            file_descriptor = open(upload_destination, "wb")

            # acknowledge that we wrote the file out
            client_socket.send(b"Successfully saved file to %s\r\n" % upload_destination)
            client_socket.send(b"Failsed to save file to %s\r\n" % upload_destination)

    # check for command execution
    if len(execute):

        # run the command
        output = run_command(execute)


    # now we go into another loop if a command shell was requested
    if command:

        while True:
            # show a simple prompt
            client_socket.send(b"<BHP:#> ")

            # now we receive until we see a linefeed
            cmd_buffer = b""
            while b"\n" not in cmd_buffer:
                cmd_buffer += client_socket.recv(1024)

            # send back the command output
            response = run_command(cmd_buffer)

            # send back the response