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Method to create event logs before memory is available

IP.com Disclosure Number: IPCOM000231525D
Publication Date: 2013-Oct-04
Document File: 2 page(s) / 62K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to save measurements and create an event log entry for the measurements that Authenticated Code Module (ACM) extended to the Trusted Platform Module (TPM).

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Method to create event logs before memory is available

The Intel* Authenticated Code Module (ACM) is run before Unified Extensible Firmware Interface (UEFI) code from reset vector is run. As part of the ACM, the Trusted Platform Module (TPM) is initialized and measurements (hash) of initial UEFI (starting from reset vector) are extended to the TPM. The purpose of this is to maintain a trust chain starting from the hardware. As per Trusted Computing Group (TCG) specifications, every PCR extend must create a corresponding event entry in the event log area. Event log location is in TCG architected space in the Advanced Configuration and Power Interface (ACPI) space. As no memory is available when ACM is run, this requirement is not met.

The novel contribution is a method to save measurements and create an event log entry for the measurements that ACM extended to the TPM.

To implement the method, as part of the TPM provisioning, create NV_Index with 'D' bit set. The size of NV_index needs to accommodate SHA1 hash, which is 20 bytes long.

The following flow charts document the additional steps (in red blocks) that are performed to create TCG event log entries for the TPM extends that happen as part of ACM.

Figure 1: ACM code (red arrow) runs before any UEFI code gets control

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Figure 2: UEFI code (red arrow) runs starting from reset vector


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