DEF CON 22 - Kallenberg and Kovah - Extreme Privilege Escalation On Windows 8/UEFI Systems

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Extreme Privilege Escalation On Windows 8/UEFI Systems
Corey Kallenberg MITRE
Xeno Kovah MITRE
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.

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

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