In my recent Black Hat Europe 2010 talk I gave an overview of the kernel exploitation prevention mechanisms that exist on FreeBSD. A few people at the conference have subsequently asked me to elaborate on the subject. In this post I will collect all the information from my talk and the various discussions I had in the Black Hat conference hallways.

This article is a followup to our last year’s advisory on canary randomisation for applications of the Debian distribution.

I was recently asked what the currently employed method is for canary randomisation in SSP-armoured Linux applications. I’ve been meaning to write an article on this for some time now, but didn’t have the necessary time. So here it is (albeit a little late).

We have found that Debian packages of the GNU libc library (versions prior to and including 2.7) provide a static (i.e. guessable) canary value to all applications armoured with the gcc SSP mechanism.