CTF-Writeups/HackTheBox/Knife.md
2021-08-28 21:16:19 +05:00

2.4 KiB

HackTheBox-Knife

NMAP

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
80/tcp open  http    Apache httpd 2.4.41 ((Ubuntu))
|_http-server-header: Apache/2.4.41 (Ubuntu)
|_http-title:  Emergent Medical Idea
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

PORT 80 (HTTP)

On the webserver we only get a static web page

I didn't find anything on the site, it's a php page so I tried default parameters but it didn't work too so I ran a nikto scan which is useful for identifying vulnerabilites on web server

Nikto

On running nikto , I came to know the version of php it's using which is PHP/8.1.0-dev

On march 2021 this version was implanted with a backdoor which is discovered and removed the github repo,attacker can execute arbitrary code by sending the User-Agentt header

https://github.com/vulhub/vulhub/blob/master/php/8.1-backdoor/README.zh-cn.md

So let's test this by following what's in the github repo

https://www.zdnet.com/article/official-php-git-server-targeted-in-attempt-to-bury-malware-in-code-base/

This works, according to the finidngs ,the User-Agnett header needs zerodium and after that we can supply php commands so we could execute commands and get RCE

We can grab the id_rsa from james's home folder

But the ssh key doesn't work, so replace the public ssh key

Also add that public key to authorized_keys

Doing sudo -l we can see what we can run as sudo

Let's see the help menu for knife

If we scroll down a little we can that we can execute ruby scripts meaning we can run shell commands

So I added my public ssh key in /root/.ssh/authorized_keys/ . we could have gotten a reverse shell or made bash SUID

Getting a reverse shell