Hack the Basic Pentesting:2 VM (CTF Challenge)

Basic pentesting 2 is a boot2root VM and is a continuation of the Basic Pentesting series by Josiah Pierce. This series is designed to help newcomers to penetration testing develop pentesting skills and have fun exploring part of the offensive side of security.

VirtualBox is the recommended platform for this challenge (though it should also work with VMware — however, I haven’t tested that).

This VM is a moderate step up in difficulty from the first entry in this series. If you’ve solved the first entry and have tried a few other beginner-oriented challenges, this VM should be a good next step. Once again, this challenge contains multiple initial exploitation vectors and privilege escalation vulnerabilities.

Your goal is to remotely attack the VM, gain root privileges, and read the flag located at /root/flag.txt.

You can download it from here.

Penetrating Methodologies

• Port scanning
• Used enum4linux to enumerate all the users
• SSH bruteforce for the user jan
• Attained SSH .pub file for user kay
• Used ssh2john to convert that pub key into crackable format
• Used john the ripper to crack key and attained a passphrase
• Logged into user kay using the passphrase
• Attained the file pass.bak
• Got root access to the lab using password in pass.bak
• Captured the flag

Let’s start!!

So, let’s begin by first scanning the ports open by using the most popular scanning tool called nmap.

nmap –A 192.168.1.139

Here, we can see that port 22 is open. But we don’t have any users currently. Let’s use enum4linux and try to find the users available.

Here, we have found 2 users jan and kay with us.

Let’s try brute-force for the user jan using hydra tool which comes pre-installed in kali. We will be using the dictionary “rockyou.txt” to brute-force the login of jan

hydra –l jan –P /usr/share/wordlists/rockyou.txt 192.168.1.139 ssh

Amazing! We have found the login details of jan!

Username: jan
Password: armando

Now, let’s try and ssh login using the details we just cracked.

Wow! We have successfully gained a shell here. But jan don’t have sudo rights. Let’s check for any other users and the files and folders in it.

cd /home
ls

We found another folder called kay. Let’s go inside it and run ls –la command.

cd .ssh
ls -la

 

Hmmm… this id_rssa file looks fishy. Let’s read it using: cat id_rsa and copy paste it in the text file.

Now, we are going to use ssh2john to convert this SSH key into a crackable file for john the ripper.

python ssh2john key > ssh_login
john ssh_login

Here, we found the phrase “beeswax.” This could either be a password or any other phrase to unlock something as we move further.

Let’s try and login to user kay using that key.

ssh -i key kay@192.168.1.139

It is asking for a passphrase now. Let’s try and enter “beeswax”

Voila!! We have successfully gained the access to kay. Now let’s try and read that pass.bak file. It looks like it could have something valuable!

cat pass.bak

It gives us a phrase “heresareallystrongpasswordthatfollowsthepasswordpolicy$$”

Now Let’s check sudo rights for him and write sudo –l

It surely asks for a root password. Let us type what we just got in pass.bak file. And you can observe kay has ALL permissions.

sudo su

Voila! It gives us a root access. Let’s check the /root directory by:

cd /root
ls

And we got a flag !!!

Hence, we were able to attain the flag in this challenge. Happy hacking!

Author: Harshit Rajpal is an InfoSec researcher and has a keen interest in technology. contact here

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