Probelms: Recreating Netcat in Python3 using the Blackhat Python Book - python-3.x

Question

help I am a beginner, I am running kali on AWS free tier, i am trying to recreate netcat using python. I was able to compile it but only the -h command works when i run it, its not listening(-l). please help. am adding some random text because its not letting me submit this question. i am using the book blackhat python and a you-tube series on it
import argparse
import socket
import shlex
import subprocess
import sys
import textwrap
import threading
def execute(cmd):
cmd = cmd.strip()
if not cmd:
return
output = subprocess.check_output(shlex.split(cmd),stderr=subprocess.STDOUT)
return output.decode()
# the engine of netcat
class Netcat:
def __init__(self,args,buffer=None):
self.args = args
self.buffer = buffer
self.socket = socket.socket(socket.AF_INET, sock.SOCK_STREAM)
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
def run(self):
if self.args.listen:
self.listen()
else:
self.send()
#if we are not running a listener
def send(self):
self.socket.connect((self.args.target , self.args.port))
if self.buffer:
self.socket.send(self.buffer)
try:
while True:
recv_len = 1
response = ''
while recv_len:
data = self.socket.recv(4096)
recv_len = len(data)
response += data.decode()
if recv_len < 4096:
break
if response:
print(response)
buffer = input('>')
buffer += '\n'
self.socket.send(buffer.encode())
except KeyboardInterrupt:
print('User terminated.')
self.socket.close()
sys.exit()
#if we are running a listener
def listen(self):
self.socket.bind((self.args.target, self.args.port))
self.socket.listen(5)
while True:
client_socket, _ = self.socket.accept()
client_threading = threading.Thread(target=self.handle,args=(client_socket,))
client_threading.start()
def handle(self, client_socket):
if self.args.execute:
output = execute(self.args.execute)
client_socket.send(output.encode())
#if argument for file upload is passed
elif self.args.upload:
file_buffer = b''
while True:
data = client_socket.recv(4096)
if data:
file_buffer += data
print(len(file_buffer))
else:
break
with open(self.args.upload, 'wb') as f:
f.write(file_buffer)
message = f'Saved file {self.args.upload}'
client_socket.send(message.encode())
elif self.args.command:
cmd_buffer = b''
while True:
try:
client.socket.send(b' #> ' )
while '\n' not in cmd_buffer.decode():
cmd_buffer += client_socket.recv(64)
response = execute(cmd_buffer.decode())
if response:
client_socket.send(response.encode())
cmd_buffer = b''
except Exception as e:
print(f'server killed {e}')
self.socket.close()
sys.exit()
if __name__ == '__main__':
parser = argparse.ArgumentParser(
description='BHP Net Tool',
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=textwrap.dedent('''Example:
netcat.py -t 192.16.1.108 -p 5555 -l -c #command shell
netcat.py -t 192.16.1.108 -p 5555 -l -u=mytest.text #uplod file
netcat.py -t 192.16.1.108 -p 5555 -l -e=\"cat /etc/passwd\" #execute command
echo 'ABC' | ./netcat.py -t 192.16.1.108 -p 135 #echo text to server port 135
netcat.py -t 192.16.1.108 -p 5555 #connect to server
'''))
parser.add_argument('-c', '--command', action='store_true', help='command shell')
parser.add_argument('-e', '--execute', help='execute specified command')
parser.add_argument('-l', '--listen', action='store_true', help='listen')
parser.add_argument('-p', '--port', type=int,default=5555, help='specified port')
parser.add_argument('-t', '--target', default='192.168.1.203', help='specified IP')
parser.add_argument('-u', '--upload', help='upload file')
args = parser.parse_args()
if args.listen:
buffer = ''
else:
buffer = sys.stdin.read()
nc = NetCat(args, buffer.encode())

Answer 1

You don't call the run function at any point of the script.
Also here you made a simple syntax error:
[...]
elif self.args.command:
cmd_buffer = b''
while True:
try:
client.socket.send(b' #> ' )
while '\n' not in cmd_buffer.decode():
cmd_buffer += client_socket.recv(64)
response = execute(cmd_buffer.decode())
if response:
client_socket.send(response.encode())
cmd_buffer = b''
except Exception as e:
print(f'server killed {e}')
self.socket.close()
sys.exit()
It's client_socket.send(b' #> ' ) not client.socket.send(b' #> ' ).
Hope I've been helpful!