BIOS Chronomancy: Fixing the Core Root of Trust for Measurement
Abstract
In this paper we look at the implementation of the Core Root of Trust for Measurement (CRTM) from a Dell Latitude E6400 laptop. We describe how the implementation of the CRTM on this system doesn't meet the requirements set forth by either the Trusted Platform Module (TPM) PC client specification [12] or NIST 800-155[20] guidance. We show how novel tick malware, a 51 byte patch to the CRTM, can replay a forged measurement to the TPM, falsely indicating that the BIOS is pristine. This attack is broadly applicable, because all CRTMs we have seen to date are rooted in mutable firmware. We also show how flea malware can survive attempts to reach infected firmware with a clean image. To fix the un-trustworthy CRTM we ported an open source \TPM-timing-based attestation" implementation [17] from running in the Windows kernel, to running in an OEM's BIOS and SMRAM. This created a new, stronger CRTM that detects tick, flea, and other malware embedded in the BIOS. We call our system\BIOS Chronomancy", and we will show that it works in a real vendor BIOS, with all the associated complexity, rather than in a simplified research environment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2013
- Accession Number
- AD1107242
Entities
People
- Amy Herzog
- Corey Kallenberg
- John Butterworth
- Xeno Kovah
Organizations
- MITRE Corporation