Monday, April 21st, 2008

CSRF pwns your box?!?!

Before going talking about an interesting set of CSRF vulnerabilities that were released this weekend, I did want to take a few moments to do some “housekeeping” on the recent XSS.  (1) I gave the Google Security Team the details for this particular issue well before talking about it on my blog.  (2) The described issue was fixed by the GST before I even considered publically speaking about the vuln.  (3)  Part of the vulnerability involved a caching flaw in Google’s servers, this issue is specific to Google and it was also fixed…   OK, on to the good stuff…
A few weeks ago, Rob Carter told me about a few interesting CSRF vulnerabilities that he discovered in a uTorrent plugin (he publicly disclosed them this weekend).  Rob was able to chain together the CSRF vulnerabilities and the net result is complete compromise of the victim’s machine!  I think this may be the first PURE CSRF vulnerability that I’ve seen that resulted in compromise of a victims machine (there is an argument amongst some of my colleagues as to whether protocol handling/URI vulnerabilities are actually a form of CSRF, but that’s another story).  The series of vulnerabilities basically follow this flow:
When a user installs the uTorrent Web UI plugin. the plugin essentially starts a locally running web server on your machine (in order to serve the Web UI).  Rob targets the CSRF vulnerabilities associated with this locally running web server.

  • Rob uses a first CSRF to turn on the “Move completed downloads” option on the uTorrent Web UI.  The CSRF looks something like this:




Once the file is placed, the next time the user restarts their machine, the attacker controlled file will be run…  there you have it… compromise of a victim’s system through three CSRFs!  Scary stuff… you can read more about the issue on Robs Blog <robs blog>.

Posted by xssniper | Filed in Security, Web Application Security