It's time to talk about TEEs

This article examines security vulnerabilities affecting Trusted Execution Environments (TEEs), such as Intel SGX, AMD SEV, and others. Trusted hardware providers like Intel and AMD primarily differentiate themselves through performance, functionality, and developer-friendliness. While they may attempt to compete on security, it is challenging to do so effectively due to the complexity of modern CPU architectures and the prevalence of side-channel attacks.

TEEs are designed to safeguard secrets and computation integrity from various environmental threats, including host OS or physical environments. However, even if the enclave platform remains secure, bugs within the enclave's code can result in disastrous consequences. These attacks have impacted not only Intel SGX but also other TEE platforms like AMD SEV.

A key point highlighted in the post is that remote attestation verifiers, which accept quotes from any Intel CPU in good standing, could be compromised since the attacker's CPU is one of them. The only way to mitigate this vulnerability is to pin your verifier to accept only your own PCK certificates, which effectively excludes the attacker's CPU. This approach, however, requires careful PKI management and is considered a risky "footgun."

The article also discusses the difficulty of reducing attack surfaces for trusted hardware. Although more principled designs like Sanctum can be employed, they often come with trade-offs such as lower performance and reduced functionality. Overall, the text warns against storing valuable secrets in TEEs, especially if physical attacks are considered part of the threat model.