Trust Zone RAM Disk Attestation for Secure Cloud OS Boot
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Solution Overview
Problem
Secure loading of a service operating system (OS) in cloud-based methods is challenging due to the lack of a root of trust for RAM disks and vulnerabilities in RAM-based boot methods, which can lead to unauthorized tampering and arbitrary code execution.
Innovation Solution
A three-phase solution is implemented to establish trust in the RAM disk, involving configuration of system memory as a trust zone, cumulative hash verification, and handshaking with the embedded controller, followed by migration of the memory identification table to the OS runtime environment for secure access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cloud-based methods are used to boot a service OS with a dynamically-created RAM disk, then boot flexibility and cloud integration are improved, but security vulnerabilities arise enabling unauthorized tampering and arbitrary code execution
Solution Approach 1:
The patent divides the boot process into distinct phases (DXE phase and OS runtime phase) with separate trust establishment mechanisms for each phase. The DXE phase establishes trust for downloading and verifying the SOS, while the OS runtime phase establishes trust for executing from the RAM disk, allowing cloud-based flexibility while maintaining security through phased validation
Solution Approach 2:
The patent performs preliminary trust establishment and cumulative hash verification during the DXE phase before the SOS is executed. The firmware downloads the SOS, verifies its integrity using cumulative hashes, and establishes a root of trust for the RAM disk contents before transferring control to the OS, preventing unauthorized tampering at the execution stage
2Reliability
If secure launch mechanisms like Secure Boot are implemented, then firmware authenticity is ensured, but they are not available in cloud-based boot contexts
Solution Approach 1:
The patent introduces an intermediary cumulative hash verification mechanism that bridges the gap between traditional secure launch requirements and cloud-based boot needs. Instead of relying on Secure Boot, the system uses cumulative hashes of downloaded SOS contents as an intermediary trust anchor, allowing firmware authenticity verification in cloud contexts where traditional mechanisms are unavailable
Solution Approach 2:
The patent changes the trust verification parameter from hardware-based Secure Boot keys to software-based cumulative hash values. This parameter change allows the system to maintain firmware authenticity verification while adapting to cloud-based boot environments where hardware-based secure launch mechanisms cannot be applied
3Speed
If a RAM disk is used for storing downloaded software, then boot speed and flexibility are improved, but no root of trust is established for the RAM disk contents
Solution Approach 1:
The patent performs preliminary cumulative hash verification of all SOS contents before they are executed from the RAM disk. During the DXE phase, the firmware downloads the SOS to the RAM disk, calculates and verifies cumulative hashes, and establishes a root of trust for the RAM disk contents before the OS runtime phase begins, ensuring both fast boot and trusted execution
Solution Approach 2:
The patent creates a trusted copy of the SOS in the RAM disk by verifying its integrity through cumulative hash comparison. The verified copy in the RAM disk is guaranteed to match the original authenticated source, establishing root of trust for the RAM disk contents while maintaining the speed benefits of RAM-based boot
Data Source
AI summary
Disclosed subject matter implements a secure, cloud-based boot sequence for a recovery OS. In at least some embodiments, a three phase solution is employed. The first phase, which may occur during the DXE phase of a boot sequence, establishes trust by configuring at least a portion system memory as a trust zone RAM disk and attesting modules that interact with the RAM disk. The second phase downloads file from the cloud and performs a cumulative hash verification and handshaking with the EC. During the third phase, a memory identification table for the trust zone s migrated to OS runtime environment to enable secured, OS runtime access to the RAM disk contents.