Three-Factor Authorization for Secure Guest HSM Binding
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Solution Overview
Problem
In trusted computing environments, existing methods fail to reliably prevent unauthorized access to cryptographic keys used by virtual machines or software containers, despite the use of hardware security modules (HSMs).
Innovation Solution
A computer-implemented method is introduced that implements a three-factor authorization to control the use of keys protected by a hardware security module (HSM) and generated by a secure guest in a trusted computing environment. This involves triggering the start of a secure guest by a hypervisor, performing an integrity check of the secure guest metadata, blocking sensitive requests to the HSM, and binding each HSM-protected key to a third authorization secret.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptographic keys are protected by hardware security modules in trusted computing environments, then key security is improved, but unauthorized access and misuse of keys by hypervisor or management software remains possible
Solution Approach 1:
The access control for HSM keys is segmented into three independent factors: (1) the HSM hardware itself, (2) the secure guest metadata containing a first authorization secret, and (3) a second authorization secret stored in trusted firmware. This segmentation ensures that compromise of one factor does not lead to unauthorized access, directly addressing the contradiction between key protection and unauthorized access prevention.
Solution Approach 2:
The trusted firmware acts as an intermediary between the hypervisor and the HSM. It receives authorization requests from the hypervisor, validates them against the third authorization secret, and only then permits access to the HSM. This intermediary layer prevents direct unauthorized access by hypervisor or management software while maintaining secure key protection.
2Reliability
If access to HSM keys is restricted to prevent unauthorized usage, then security is improved, but system complexity increases due to multiple authorization checks
Solution Approach 1:
The first authorization secret is embedded in the secure guest metadata during guest initialization, and the second authorization secret is pre-stored in the trusted firmware. These preliminary actions eliminate the need for complex runtime authentication procedures, as the authorization secrets are already in place before any HSM access is required.
Solution Approach 2:
The trusted firmware automatically performs the authorization check using the third authorization secret without requiring manual intervention or complex decision-making. The system self-validates authorization requests against the pre-stored secret and automatically permits or denies access, simplifying the operational complexity while maintaining security.
3Reliability
If multiple authorization secrets are introduced to prevent credential sharing between guests, then access control security is improved, but the difficulty of detecting and measuring unauthorized usage increases
Solution Approach 1:
The system provides feedback by validating each HSM access request against the third authorization secret stored in trusted firmware. This feedback mechanism automatically detects unauthorized usage attempts by rejecting requests that fail the authorization check, making unauthorized usage detection straightforward despite the complex multi-factor authorization structure.
Data Source
AI summary
A method, system, and computer program product implement a three-factor authorization in a trusted computing environment. The method includes triggering, by a hypervisor, a start of a secure guest by passing control regarding an image of the secure guest and metadata of the secure guest to a trusted firmware, where the secure guest is designed to access a hardware security module (HSM). Upon a successful integrity check of the metadata of the secure guest by the trusted firmware, the secure guest is started using the hypervisor and any sensitive request from the secure guest to the HSM is blocked. The secure guest submits a request with a request structure including a third authorization secret and a characterization of a requested HSM to the trusted firmware. The method also includes binding each HSM protected key generated in the requested HSM in response to the request to the third authorization secret.