Paper
Gaining Access
Nmap scan:
We can append paper.htb to our /etc/hosts file, as per standard HTB stuff. The web pages don't reveal much and have the default pages loaded.
When proxying requests through Burp, we can see this custom X-Backend-Server header.
We can add the office.paper header to our hosts file and enumerate that.
Office Paper
The new domain was some kind of company website.
At the very bottom, it says this was Powered By Wordpress. When looking at some of the recent posts, we can see this one that highlights there are secret posts.
Because there were hints to view a private post of some sort, we can try appending ?static=1 to the URL and see what we get.
We now have a new URL to head to.
Recyclops
Within this new URL, we can register as a new user and login to find a Rocket.Chat instance.
Within the chats tab, we can see that there is a recyclops bot that has some documentation.
I tested it out and it seems to execute code on the machine remotely.
Basic directory traversal works on this machine due to a lack of input validation for the directory entered.
The user is dwight, and we can see that within this directory, there is a hubot directory. Hubot is an open source chat robot that could be the one used for this user. I could not read the .ssh files, so this was the next best thing.
We can see that within the hubot/ directory, there's a .env file. This could contain some interesting content.
We can test this password with the user dwight and attempt to SSH in, which works!
Privilege Escalation
Running a LinPEAS, we find that CVE-2021-3560 works on this machine because of an outdated sudo version.
CVE-2021-3560 is an authentication bypass on polkit, which allows for users to carry out privileged actions using DBus. This repo here works on this machine to get root:
