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3.1 BIOS Update Authentication

NIST platform security: roots of trust, firmware and secure enclaves SP 800-147B
All changes in this version
first version loaded 3 BIOS Security Principles part of 3

Title

BIOS Update Authentication

Control

Authenticated BIOS update mechanisms shall be implemented in an RTU (see Section 2.5). These mechanisms employ digital signatures to ensure the authenticity and integrity of BIOS update images. The Verification Component of the RTU shall contain the digital signature verification algorithm and a key store. The key store shall include the public key needed to verify the signature of the BIOS update image or an approved cryptographic hash [FIPS180-4] of the key. In the latter case, the update mechanism shall hash the public key provided with the BIOS update image and ensure that it matches a hash which appears in the key store before using the provided public key to verify the signature on the BIOS update image.

BIOS images shall be signed in conformance with NIST SP 800-89, Recommendation for Obtaining Assurances for Digital Signature Applications [SP800-89], using an approved digital signature algorithm as specified in NIST FIPS 186-4, Digital Signature Standard (DSS) [FIPS186-4], that provides at least 112 bits of security strength, in accordance with NIST SP 800-131A, Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths [SP800-131A].

Authenticated update mechanisms shall ensure that BIOS update images have been digitally signed and that the digital signature can be verified using a key stored or verified by the RTU before updating the BIOS. These mechanisms may also verify digital signatures over BIOS code in flash memory prior to execution, particularly if the BIOS flash is not protected (see Section 3.3). Recovery mechanisms should also use an authenticated update mechanism, unless the recovery process meets the guidelines for a secure local update.

The system should provide mechanisms capable of preventing unauthorized update of the BIOS to an earlier authentic version. This limitation of the rollback mechanism may be accomplished, for example, by verifying that the version number of the BIOS image is higher than the currently installed BIOS image’s version number. Appropriate rollback protections will depend upon the environment in which the server is used and the security and availability needs of the organization operating the server. The system may allow administrators to authorize rollback to an earlier version, disable these mechanisms, or otherwise configure these mechanisms based on their needs.