Secure Boot Certificate Use Policy Scope Limitation

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Solution Overview

Problem

Current Secure Boot systems in information handling systems lack the ability to limit the privileges and scope of certificates, making them susceptible to privilege-type attacks as any certificate inserted can verify any firmware or bootloader, leading to potential security vulnerabilities.

Innovation Solution

Implementing certificate use policies (CUPs) that identify and manage the secure boot certificates, determining their permitted use, and allowing verification only if the policy permits, thereby limiting the scope and privilege of certificates through X.509 embedded attributes, integrated policies, and BIOS setup configuration controls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a certificate is inserted into the Secure Boot database without limitations, then the certificate can authenticate any firmware or bootloader on the platform, but this makes the system susceptible to privilege-type attacks

Engineering Contradiction:

Improvecertificate authentication scopeVSAvoidprivilege-type attacks

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by associating specific certificate use policies with individual certificates in the database. Each certificate can have its own policy that defines which firmware image types it can authenticate. This allows different parts of the certificate database to have different authorization levels, preventing a single certificate from having universal privileges while maintaining the ability to authenticate various firmware types with appropriately scoped certificates.

Inventive Principle:

Principle #3Local quality

2Reliability

If a certificate intended for bootloader verification is added to the database, then it can verify bootloader images, but it also gains the same authority to verify low-level UEFI code

Engineering Contradiction:

Improvefirmware verificationVSAvoidcertificate permission management

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the certificate permission system by introducing certificate use policies that divide the authentication authority into distinct categories. Instead of treating all certificates uniformly, the system segments permissions by firmware image type (bootloader, UEFI code, etc.). This segmentation allows a certificate to be reliably used for its intended purpose while preventing it from inadvertently gaining authority over other firmware types.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces certificate use policies as an intermediary layer between certificates and firmware verification. This intermediary mechanism mediates the authentication process by checking whether a certificate's associated policy permits verification of the specific firmware image type being authenticated. This adds a control layer that manages certificate permissions without compromising the reliability of verification for authorized uses.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If certificates are given universal verification authority, then any firmware can be authenticated, but this leaves the system vulnerable to security breaches

Engineering Contradiction:

Improvefirmware authenticationVSAvoidsystem security

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies parameter changes by modifying the authentication process to include policy verification as an additional parameter check. Instead of simply verifying cryptographic signatures, the system now also evaluates the certificate use policy parameters associated with each certificate. This changes the authentication from a binary yes/no based on signature validity to a multi-parameter evaluation that includes permission scope, thereby maintaining ease of operation while improving security reliability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11514165B2Systems and methods for secure certificate use policies

Publication Date: 2022.11.29 DELL PROD LP

AI summary

An information handling system may include a processor and a basic input/output system communicatively coupled to the processor and embodied by executable instructions embodied in non-transitory computer readable media, the instructions configured to, when executed by the processor: identify, for a firmware image, a secure boot certificate; identify, for the secure boot certificate, a certificate use policy; determine whether the certificate use policy permits verification of the firmware image using the secure boot certificate; and allow the firmware image to be verified with the secure boot certificate if the certificate use policy permits verification of the firmware image using the secure boot certificate.