[论文解读] SoK: Hardware-supported Trusted Execution Environments

Moritz Schneider, Ramya Jayaram Masti+3 more|arXiv (Cornell University)|May 25, 2022

Security and Verification in Computing被引用 28

一句话总结

本文系统化硬件辅助TEE，分析在不同架构中如何实现可验证启动、运行时隔离、可信输入/输出和安全存储，并提供统一的分类体系和设计空间洞察。

ABSTRACT

The growing complexity of modern computing platforms and the need for strong isolation protections among their software components has led to the increased adoption of Trusted Execution Environments (TEEs). While several commercial and academic TEE architectures have emerged in recent times, they remain hard to compare and contrast. More generally, existing TEEs have not been subject to a holistic systematization to understand the available design alternatives for various aspects of TEE design and their corresponding pros-and-cons. Therefore, in this work, we analyze the design of existing TEEs and systematize the mechanisms that TEEs implement to achieve their security goals, namely, verifiable launch, run-time isolation, trusted IO, and secure storage. More specifically, we analyze the typical architectural building blocks underlying TEE solutions, design alternatives for each of these components and the trade-offs that they entail. We focus on hardware-assisted TEEs and cover a wide range of TEE proposals from academia and the industry. Our analysis shows that although TEEs are diverse in terms of their goals, usage models, and instruction set architectures, they all share many common building blocks in terms of their design.

研究动机与目标

• 为硬件辅助TEE定义对手模型和分类体系。
• 系统化实现可验证启动、运行时隔离、可信IO和安全存储的设计决策。
• 跨架构比较TEE，以识别共同的构件和权衡。
• 强调设计选择如何聚集在TEEs相对较小的设计空间内。

提出的方法

• 按平台控制和能力对对手进行分类。
• 提供隔离策略（时域、空间、时空）和执行手段（逻辑、密码学）
• 对测量类型的信任根（SRTM、DRTM、硬件）及认证机制（本地/远程）进行调查。
• 分析CPU与内存隔离技术及其在不同TEE中的实现。
• 描述跨TEE的可信IO架构与密封实践。
• 总结设计空间结论及对未来TEE的影响。

实验结果

研究问题

• RQ1 硬件辅助TEE防御的常见对手模型有哪些？
• RQ2 可验证启动机制（RTMs、测量、认证）在不同TEE中的实现方式？
• RQ3 CPU与内存使用了哪些隔离策略，它们的权衡是什么？
• RQ4 TEE中的可信IO如何实现，提供/密封选项有哪些？
• RQ5 跨体系结构的可复用设计决策在多大程度上限制了TEE设计空间？

主要发现

• 尽管目标和ISA多样，大多数TEE共享一组共同的构件。
• CPU隔离普遍使用时域分区并在TEE中实施逻辑强制。
• 内存隔离方法多样，可能因对手威胁模型而异。
• 出现两种主要的可信IO模式：逻辑型（可信路径）和密码学型（安全通道）。
• 密封和 provisioning 机制各异；大约三分之一的TEE讨论了密封支持。
• 总体而言，四个目标的TEE设计空间相对较小，并广泛重用设计选择。