TCG EFI Platform Specification Version 1.22 Copyright © TCG 2014
Introduction to this Document
Start of informative comment:
This document is about the processes that boot an Extensible Firmware Interface (EFI) platform
and load an OS on that platform. Specifically, this specification contains the requirements for
measuring EFI unique events into TPM PCRs and adding boot event entries into the Event Log.
In this document, “EFI” refers to either EFI platforms (as defined by the Extensible Firmware
Interface Main Specification), or UEFI platforms (as defined by the Unified Extensible Firmware
Interface Specifications). See section 1.2.
Software on the platform uses PCR values to seal secrets into blobs and then unseal those
secrets if the PCR values are the same as when the secret was sealed.
Software on the platform uses PCR values together with the Event Log entries to reconstruct boot
events, which requires a complete Event Log.
Software on other platforms uses the PCR values, together with the Event Log entries, for remote
attestation of the EFI platform that holds the PCR values and Event Log.
Structure of this document
The scope of this specification is limited to what EFI can measure.
This document only describes events specific to an EFI or UEFI implementation. Therefore, this
specification does not duplicate measurements defined in other TCG documents. The rationale is
that the EFI and UEFI Specifications are pure interface specifications that do not imply the
specifics of the implementation (other than some behavior in the boot manager chapter). The
underlying implementation of a UEFI or EFI system can be based upon the Intel Framework,
UEFI Platform Initialization (PI) or other infrastructure code.
Both the TCG PC Client Specific Implementation Specification for Conventional BIOS and this
specification are needed to gain a full understanding of an EFI or UEFI platform. In the event of
conflicts between this specification and the Conventional Bios Specification, then the
Conventional Bios Specification applies, unless otherwise stated.
In addition to the measurements defined in this specification, EFI systems also perform
measurements defined in other TCG documents, including mandatory as well as optional
measurements.
Events from the TCG PC Client Implementation Specification for Conventional BIOS include, but
are not limited to: EV_S_CRTM_VERSION, EV_POST_CODE “ACPI DATA” and
EV_CPU_MICROCODE.
Events from the TCG Generic Server Specification include, but are not limited to:
EV_TABLE_OF_DEVICES (for processor physical location).
This specification contains nine other sections.
• Section 2 defines the meaning of three fundamental TCG concepts on an EFI platform: Static
Locality, Static CRTM, and the static transitive chain of trust.
• Section 3 is an overview of the platform boot process and the OS boot process on an EFI
platform and provides the model for PCR usage and for adding events to the Event Log. If the
user of this specification reads this section first, the details in section 4 through 7 will be
easier to understand.
• Section 4 contains the requirements for measuring PE/COFF image files.
• Section 5 is the detailed specification for measuring the platform boot process on an EFI
platform.
Revision 15 Page 5 of 43 January 27, 2014
TCG Published