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3.4 Non-Bypassability

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

Non-Bypassability

Control

The design of the system and accompanying system components and firmware shall ensure that there are no mechanisms to install and execute unauthenticated BIOS code, except through physical intervention and the secure local update mechanism.

In particular, the authenticated update mechanisms shall be the exclusive mechanisms for modifying the RTU absent physical intervention through the secure local update mechanism. The design of the system and accompanying system components and firmware shall ensure that there are no mechanisms that allow the host processor or any other system component to bypass the authenticated update mechanism for updating the RTU, except for the secure local update mechanism.

A modern platform includes design features that give system components direct access to the RTU or system BIOS for performance and management improvements, such as shadowing the BIOS in RAM or for system management mode operations. A system component may have read access to system flash memory, but it shall not be able to directly modify the RTU unless that component serves as an extension to the RTU or as an RTU itself.