GamingServer (Easy) – SAwkNerd Blog

An Easy Boot2Root box for beginners.

Enumeration

As always, start with an nmap scan.

Nmap

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
80/tcp open  http    Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: House of danak
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kerne

Website is some kind of gaming website. Found an uploads directory with a dict.lst file that was what appear to be some password options in it. Also found an html comment on the index.html page that gives a potential username:

<!-- john, please add some actual content to the site! lorem ipsum is horrible to look at. -->

Gobuster

A little gobuster to see if we can find anything special.

===============================================================
Gobuster v3.6
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://10.10.120.179
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.6
[+] Timeout:                 10s
===============================================================
Starting gobuster in directory enumeration mode
===============================================================
/uploads              (Status: 301) [Size: 316] [--> http://10.10.120.179/uploads/]
/secret               (Status: 301) [Size: 315] [--> http://10.10.120.179/secret/]

The /secret/ path reveals a secretKey file which is an encrypted private key.

Used JohnTheRipper to crack the private key password.

ssh2john secretKey > secretKey.hash
john --wordlist=/usr/share/wordlists/rockyou.txt secretKey.hash
# Using default input encoding: UTF-8
# Loaded 1 password hash (SSH, SSH private key [RSA/DSA/EC/OPENSSH 32/64])
# Cost 1 (KDF/cipher [0=MD5/AES 1=MD5/3DES 2=Bcrypt/AES]) is 0 for all loaded hashes
# Cost 2 (iteration count) is 1 for all loaded hashes
# Will run 4 OpenMP threads
# Press 'q' or Ctrl-C to abort, almost any other key for status
# letmein          (secretKey)     
# 1g 0:00:00:00 DONE (2024-04-09 23:20) 100.0g/s 51200p/s 51200c/s 51200C/s teiubesc..letmein
# Use the "--show" option to display all of the cracked passwords reliably
# Session completed.
openssl rsa -in secretKey -out secretKey.decrypted

Tried to login to ssh with the john user discovered earlier and the private key, and logged in successfully.

What is the user flag?

********************************

Uploaded and ran linpeas.sh, but nothing of real substance was revealed. The john user is a member of the sudo group, but the password is unknown so that’s not useful. I explored some options of messing with polkit, but it was a dead end.

The only other thing that jumped out to me was that john is also a member of the lxc group. It’s interesting that linpeas didn’t offer this up, but there is an interesting privesc via lxc that I found on (https://book.hacktricks.xyz/linux-hardening/privilege-escalation/interesting-groups-linux-pe/lxd-privilege-escalation)

I had to download the Alpine Linux image and build it on my local mahcine, and them upload the filesystem and machine file to the target. I was then able to load the machine, mount the root filesystem into a directory inside the machine, set it to privileged mode, and then run and execute a terminal inside the container.

From inside the container I made /mnt/root/bin/bash setuid and then exited the container and ran /bin/bash -p to become root.

What is the root flag?

********************************

Enumeration

Nmap

Gobuster

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