eMMC Command Filtering for Secure Firmware Access Control
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Solution Overview
Problem
The limited capacity of Serial Peripheral Interface (SPI) flash memory in server platforms restricts the storage of firmware for multiple platform devices, and unauthorized access or tampering risks are not adequately addressed in existing update protocols.
Innovation Solution
Implementing a Platform Root of Trust (PRoT) to monitor and filter commands on the eMMC bus, injecting an intentionally invalid integrity check value to prevent unauthorized access and tampering by blocking disallowed operations, ensuring firmware integrity and security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SPI flash memory is used for firmware storage, then the storage device is compact and integrates well with the platform, but the storage capacity is limited and cannot store firmware for multiple platform devices
Solution Approach 1:
The eMMC storage device is configured to serve multiple platform devices by storing firmware images for different devices (CPU, I/O device, management controller) in a single storage medium, replacing the need for separate SPI flash devices for each firmware type
2Quantity of substance
If eMMC storage device is used to increase firmware storage capacity, then more firmware can be stored for multiple platform devices, but the risk of unauthorized access and tampering increases
Solution Approach 1:
The system performs preliminary integrity verification of firmware images before execution by checking cryptographic hashes (SHA-256) against stored expected values, and implements command filtering to prevent unauthorized write operations to firmware partitions, thereby countering potential tampering before it can affect system operation
Solution Approach 2:
A management controller acts as an intermediary between the host and the eMMC storage device, monitoring and filtering commands to prevent unauthorized access to firmware partitions while allowing legitimate read operations and firmware updates through verified channels
3Reliability
If command filtering is implemented to block unauthorized accesses, then firmware integrity is protected, but the system complexity increases due to additional monitoring mechanisms
Solution Approach 1:
The management controller integrates the command filtering and integrity verification functions within the existing platform management infrastructure, allowing the system to self-monitor and self-protect firmware integrity without requiring external security devices or significantly increasing overall system complexity
Data Source
AI summary
Examples described herein relate to: an interface and circuitry to: monitor a bus for a particular message and based on detection of the particular message, replace the particular message with an invalid portion and provide the invalid portion to a receiver, wherein the particular message comprises a command and wherein the receiver comprises an Embedded Multi-Media Card (eMMC). In some examples, the circuitry comprises a platform root of trust (PRoT), a management controller, a multiplexer, or a host system.