A practical attack on Intel's trusted execution technology (TXT) is due to be demonstrated at a hacking conference next month.
Security researchers from Invisible Things Lab have created a technique for compromising the integrity of software loaded via TXT, a key component in Intel's Safer Computing Initiative and part of the chip giant's vPro brand. Intel's TXT technology - which aims to protect systems against tampering - hooks into CPUs and chipsets as well as featuring use of Trusted Platform Module 1.2 (TPM) technology.
For example, the technology ensures programs running on a virtual machine are free to go about their business without interference from other (potentially malicious) packages loaded onto the same system. It also has applications in Digital Rights Management.
Invisible Things Lab's Rafal Wojtczuk and Joanna Rutkowska, best known for her extensive work on Vista kernel security and rootkits, have created a two-stage approach for defeating this technology.
The first part of the attack relies on exploiting an as-yet unspecified vulnerability in Intel's system software. Part two involves bypassing the TXT technology itself. A demo of the technique is due to take place at a presentation at the Black Hat conference in Washington DC on 18-19 February.
A statement by Invisible Things (extract below) explains the general approach, without going into details.
Our research shows how an attacker can compromise the integrity of a software loaded via an Intel TXT-based loader in a generic way. We have created a proof-of-concept code that demonstrates the successful attack against tboot — Intel's implementation of the trusted boot process for Xen and Linux.
Our attack comprises two stages. The first stage requires an implementation flaw in a specific system software. The second stage of the attack is possible thanks to a certain design decision made in the current TXT release.
Warsaw, Poland-based Invisible Things is working with Intel towards hardening its technology to defend against the attack. Intel has promised to release an updated TXT specification to developers that explains how to armour plate TXT-based loaders so as to thwart potential assaults.
Intel TXT/vPro compatible hardware has been shipping for only a year so the impact of weaknesses in the technology is less than it might be if the technology was already widely deployed. The Xen hypervisor is one of the few currently widely used products to rely on the technology. ®