Securing TEEs With Verifiable Execution Contracts

Recent works have demonstrated that trusted execution environments, such as Intel Software Guard Extensions, are vulnerable to various attacks from the privileged software, including side-channel attacks. Existing solutions, such as T-SGX, Deja Vu, Cloak and Varys, detect side-channel attacks at runtime. But they are limited by design, because false detection is unavoidable in these detection methods and therefore any security policy developed atop these mechanisms has to tolerate some malicious operations to achieve practical false positive detection rates. In this article, we propose the concept of verifiable execution contracts, which request the privileged software to provide a benign execution environment for enclaves within which launching attacks becomes very difficult, if not impossible. Since the privileged software is untrusted, we design methods for verifying that the execution contracts are observed. With the proposed verifiable execution contracts, we analyzed how existing attacks could be mitigated.