BIOS Chronomancy: Fixing the Core Root of Trust for Measurement

Abstract

(The first appearance at NoSuchCon in May 2013 did not include a discussion of VU#912156, but subsequent talks did.) Discussed how the S-CRTM is supposed to provide trustworthy reporting to detect the presence of BIOS level attackers. First showed a way that an attacker could exploit their way into a BIOS, even if all security mechanisms were properly configured (VU#912156). Then showed “The Tick”, which is BIOS-resident malware that subverts the S-CRTM by lying to the TPM to replay or recalculate a clean measurement. Then showed “The Flea”, which was BIOS malware that could survive attempts to remove it through a reflash, by infecting the new BIOS as it is about to be written. To defense against such attacks, and build a stronger S-CRTM, we used our existing work on Timing-Based Attestation to create “BIOS Chronomancy”. This defensive technique allows for the customization of the BIOS to provide timing side-channel tamper-evidence to allow for the detection of BIOS malware. Also released “Copernicus”, a free Windows tool for inspecting the BIOS vulnerability/integrity state. This talk was effectively 3 talks crammed into one, so that we could guarantee we would get into BlackHat. ;)

Xeno Kovah

Dark Mentor Level X

Hacking firmware like it’s no big deal.