Extreme Privilege Escalation On Windows 8/UEFI Systems

Presented at DEF CON 22 (2014), Aug. 8, 2014, 2 p.m. (Unknown duration)

It has come to light that state actors install implants in the BIOS. Let no one ever again question whether BIOS malware is practical or present in the wild. However, in practice attackers can install such implants without ever having physical access to the box. Exploits against the BIOS can allow an attacker to inject arbitrary code into the platform firmware. This talk will describe two such exploits we developed against the latest UEFI firmware. The UEFI specification has more tightly coupled the bonds of the operating system and the platform firmware by providing the well-defined "runtime services" interface between the OS and the firmware. This interface is more expansive than the interface that existed in the days of conventional BIOS, which has inadvertently increased the attack surface against the platform firmware. Furthermore, Windows 8 has introduced APIs that allow accessing this UEFI interface from a userland process. Vulnerabilities in this interface can potentially allow a userland process to escalate its privileges from "ring 3" all the way up to that of the platform firmware, which includes permanently attaining control of the very-powerful System Management Mode (SMM). This talk will disclose two vulnerabilities that were discovered in the Intel provided UEFI reference implementation, and detail the unusual techniques needed to successfully exploit them. Special thanks to the contributing researchers for their help in co-authoring: John Butterworth is a security researcher at The MITRE Corporation who currently specializes in Intel firmware security. In 2012 he co-authored the whitepaper "New Results for Timing-Based Attestation" which used timing based attestation to detect Windows kernel hooks. This research was presented at DEF CON and the 2012 IEEE Symposium on Security and Policy. In 2013 he and his colleagues authored "BIOS Chronomancy:Fixing the Static Root of Trust for Measurement" which proposed using Timing-Based Attestation during the BIOS boot process to resolve critical problems which they had found with current implementations of the Trusted Computing Group's "Static Root of Trust for Measurement". He has presented this research at NoSuchCon, Black Hat USA, SecTor, SEC-T, Breakpoint, and Ruxcon. Following this he has created a tool called Copernicus designed to determine just how prevalent vulnerable BIOS is in industry. John is currently continuing to research the security of BIOS/UEFI and the Intel architecture. Sam Cornwell is a Sr. InfoSec Engineer at The MITRE Corporation, a not-for-profit company that runs 6 federally funded research and development centers (FFRDCs) as well as manages CVE. Since 2011 he has been working on projects such as Checkmate (a kernel and userspace memory integrity verification & timing-based attestation tool), Copernicus, a (BIOS extractor and configuration checker), and several other private security sensors designed to combat sophisticated threats. He has also researched and developed attacks against UEFI SecureBoot.

Presenters:

  • Xeno Kovah - MITRE
    Xeno Kovah is a Lead InfoSec Engineer at The MITRE Corporation, a non-profit company that runs 6 federally funded research and development centers (FFRDCs) as well as manages CVE. He is the team lead for the BIOS Analysis for Detection of Advanced System Subversion project. On the predecessor project, Checkmate, he investigated kernel/userspace memory integrity verification & timing-based attestation. Both projects have a special emphasis on how to make it so that the measurement agent can't just be made to lie by an attacker. Xeno is also the founder and leading contributor to OpenSecurityTraining.info. twitter: @xenokovah
  • Corey Kallenberg - MITRE
    Corey Kallenberg is a security researcher for The MITRE Corporation who has spent several years investigating operating system and firmware security on Intel computers. In 2012 he coauthored work presented at DEF CON and IEEE S&P on using timing based attestation to detect Windows kernel hooks. In 2013 he helped discover critical problems with current implementations of the Trusted Computing Group's "Static Root of Trust for Measurement" and co-presented this work at NoSuchCon and Blackhat USA. Later, he discovered several vulnerabilities which allowed bypassing of "signed BIOS enforcement" on a number of systems, allowing an attacker to make malicious modifications to the platform firmware. These attacks were presented at EkoParty, HITB, and PacSec. Recently, Corey has presented attacks against the UEFI "Secure Boot" feature. Corey is currently continuing to research the security of UEFI and the Intel architecture. twitter: @coreykal

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