Monday, January 5, 2009

Chk B4 U TXT

A moment of technical geek-out: Joanna at Invisible Things Labs has a very exciting attack on Trusted Computing Technology forthcoming at this year's Black Hat Conference in DC this February.

LaGrande, recently renamed Trusted Execution Technology (TXT), is Intel's response to the Trusted Computing trend.

The sole purpose of Intel TXT technology is to provide a trusted way for loading and executing system software, e.g. Operating System kernel or Virtualization Machine Monitor. What is extraordinary here is that TXT doesn't make any assumptions about the state of the system before loading the software, thus making it possible for a user to ensure secure load of an OS or VMM, even in a potentially compromised machine.

In other words, our system can be all full of boot sector viruses and BIOS rootkits, and god-knows-what-else, and still TXT should allow to load a clean VMM (or OS kernel) in a secure way, immune to all those rootkits present in the system in a moment just before the load process. This TXT-supported load process is called Late Launch, and is implemented via a special new CPU instruction called SENTER.

Attacking Intel TXT!
Ok, not in this post today, but rather at the upcoming Black Hat conference in Washington, DC in February. Over the recent months, Rafal and I have been looking at the Intel TXT technology as part of a work done for a customer, to see if this could be used to improve security of a product, from a typical user's perspective. We figured out that it definitely could, but that there are also some issues…

And those "issues" gave us a starting point in developing a proof-of-concept (albeit very reliable) exploit that shows how we can bypass trusted boot process implemented by Intel's tboot.

Tboot, which is also part of (scroll down to the end of the page) the Xen hypervisor, can be though of as a reference implementation of TXT-based system loader, that could be used to securely load either the Xen hypervisor or the Linux kernel, when run on a vPro/TXT compatible hardware.

Press release here.

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