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Digitalworld.local: JOY Vulnhub Walkthrough

Today we have another CTF post, one more series of Dgitalworld.local named “joy” and the credits goes to Donavan. This is a boot to root challenge available on vulnhub you can download it from the given below link and the CTF is design for OSCP practices.

Download Link: https://www.vulnhub.com/entry/digitalworldlocal-joy,298/

Level: Intermediate

Task: Obtain root shell

Penetration Testing  Methodologies

Scanning

  • Nmap

Enumeration

  • FTP anonymous login

Exploit

  • Exploit proftpd using Metasploit

Privilege Escalation

  • Sudo right

Walkthrough

Scanning

Let’s start off with the scanning process. This target VM took the IP address of 192.168.1.104 automatically from our local wifi network.

Then, as usual, we used our favourite tool Nmap for port scanning. Here we found that so many ports were opened but port 21 for ftp looks more interesting to me as anonymous login was allowed on the running machine for two directories /upload /download.

nmap -A 192.168.1.104

Enumeration

So, we connect to ftp where here I find two directories /download and /upload. The upload directory has read and write permission whereas the /download has read permission.  So, we try to access /download directory and found a file within its named “directory”.

ftp 192.168.1.104
ls
cd download
ls
get directory

Thus, we copied the file named as directories in our local machine.

So, by reading directory file, you will evaluate that, this file gave a brief idea about Patrick’s directory where Patrick should be the user account. In this, we look at a file name “version_control”  it could be considered as a suspect. 

Since the version_control exist inside Patrick’ s directory so we cannot grab the file directly, therefore, I try to transfer version_control file inside /upload directory because it has read/write permission through ftp anonymous login.

telnet 192.168.1.104 21
site cpfr /home/patrick/version_control
site cpto /home/ftp/upload/version_control

Hence you can observe with the help of above command we had copied “version_control” inside /upload folder.

Further, we navigate to /upload/version_control and found a version of ftp service running on host machine moreover we obtained the path for webroot i.e. /var/www/tryingharderisjoy.

Exploit

So, we search for an exploit for proftpd and found a Metasploit module thus we execute the following command to get a session of the host machine.

use exploit/unix/ftp/proftpd_modcopy_exec
msf exploit(unix/ftp/proftpd_modcopy_exec) > set rhosts 192.168.1.104
msf exploit(unix/ftp/proftpd_modcopy_exec) > set SITEPATH /var/www/tryingharderisjoy
msf exploit(unix/ftp/proftpd_modcopy_exec) > exploit

We successfully obtained the command shell of the remote machine, now it was time for post enumeration to step towards privilege escalation. Thus, we import python one-liner to access proper tty shell and start with directory traversing.

It feels good when we dig-out credential of Patrick from inside the /ossec/patricsecretofjoy.

credentials for JOY:

patrick:apollo098765
root:howtheheckdoiknowwhattherootpasswordis

Privilege Escalation

Without wasting time, we switch as Patrick and check for its sudo rights if assigned for him. Here we found that Patrick can run /home/patrick/script/test as sudo user. So, when we run the test script, it gave nothing useful as it was a demo to test working bash script thus the file “test” was useless but it own by root user which was doubtful for us.

So we decided to replace /test script with other malicious script but there was no writable permission on /script directory.

Thus, again we decided to use FTP anonymous login for replacing genuine /test file with bogus /test file which will be a backdoor to provide higher privilege shell.

Therefore, we created a malicious file to get bash shell with the help of command given and named as “test” then try to upload it inside /upload directory since it was a writable folder.

echo "awk 'BEGIN {system(\"/bin/bash\")}'" > test

Once again with the help of telnet let’s connect to ftp service running on the host machine and execute the following command to inject malicious script “test” inside /home/Patrick/script.

telnet 192.168.1.104 21
site cpfr /home/ftp/upload/test
site cpto /home/patrick/script/test

So now we have injected the malicious file inside /script and user Patrick has sudo right to execute the /script/test as superuser. Now let’s escalate the privilege by execute following command and finish the task assigned by the author.

sudo /home/patrick/script/test

Hmmmmm!! so we have spawn root shell successfully, now let’s move inside /root directory and grab the proof.txt file and secret file.

cd /root
cat proof.txt
author-secret.txt

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

2 thoughts on “Digitalworld.local: JOY Vulnhub Walkthrough

  1. Thanks for the review (probably the first public one)! 🙂

    A shout-out: There are other methods to root the box (just like Bravery). If you want, you could try the other methods and write them in, too!

    Get in touch with me by e-mail.

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