Trusted Intermediary Realm Memory Access Control
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Solution Overview
Problem
In privilege-based memory access control schemes, there is a lack of control over memory access by more privileged processes, which can lead to trust issues, especially in multi-tenant environments like data centers where sensitive information needs to be isolated from hypervisors and other virtual machines.
Innovation Solution
A realm-based memory access control approach is introduced, where each memory region is owned by a specific realm, allowing the owner realm to exclude other realms, including those at higher privilege levels, from accessing its data, and a trusted intermediary realm can manage security configuration parameters and provide attestation for secure migration and key management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If privilege-based memory access control is used, then memory access control is simplified, but trust issues arise because more privileged processes can access memory regions without restriction
Solution Approach 1:
The patent segments memory access control into two independent dimensions: privilege levels (traditional hierarchical control) and realm ownership (fine-grained exclusive control). Each memory region is assigned to a specific realm that has exclusive ownership rights, allowing the system to maintain both simplicity through privilege levels and reliability through realm-based segmentation that prevents even high-privilege processes from accessing owned memory regions without permission.
Solution Approach 2:
The patent introduces realm ownership as an intermediary layer between privilege levels and memory access. The realm acts as a mediator that enforces exclusive access rights, preventing direct trust relationships between privileged processes and memory regions. This intermediary mechanism resolves the trust issue by ensuring that even highly privileged processes cannot access memory regions owned by other realms without proper authorization.
2Reliability
If realm-based memory access control is implemented, then trust and security are improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent implements realm-based control through a universal mechanism that serves multiple functions: it provides memory access control, enables secure migration, facilitates key management, and maintains isolation between different execution environments. By designing the realm framework to handle multiple security-related operations through a unified approach, the patent reduces the need for separate complex mechanisms while maintaining high reliability and trust.
3Reliability
If memory access control is distributed among multiple realms, then security isolation is improved, but control overhead increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing realm ownership relationships and memory region assignments before execution begins. The system maintains ownership information in accessible data structures that enable fast verification during memory access, eliminating the need for complex real-time negotiation between realms. This preliminary configuration allows the system to achieve strong security isolation with minimal control overhead during actual memory operations.
Data Source
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AI summary
Memory access circuitry (26) controls access to memory based on ownership information defining, for a given memory region, an owner realm specified from among two or more realms, each realm corresponding to at least a portion of a software processes running on processing circuitry (8). The owner realm has a right to exclude other realms from accessing data stored within the given memory region. When security configuration parameters for a given realm specify that the given realm is associated with a trusted intermediary realm identified by the security configuration parameters, the trusted intermediary realm may be allowed to perform at least one realm management function for the given realm, e.g. provision of secret keys and/or saving/restoring of security configuration parameters. This can enable use cases where multiple instances of the same realm with common parameters need to be established on the same system at different times or on different systems.