TEE.fail: Breaking Trusted Execution Environments via DDR5 Memory Bus Interposition

With the increasing popularity of remote computation like cloud computing, users are increasingly losing control over their data, uploading it to remote servers that they do not control. Trusted Execution Environments (TEEs) aim to reduce this trust, offering users promises such as privacy and integrity of their data as well as correctness of computation. With the introduction of TEEs and Confidential Computing features to server hardware offered by Intel, AMD, and Nvidia, modern TEE implementations aim to provide hardware-backed integrity and confidentiality to entire virtual machines or GPUs, even when attackers have full control over the system's software, for example via root or hypervisor access. Over the past few years, TEEs have been used to execute confidential cryptocurrency transactions, train proprietary AI models, protect end-to-end encrypted chats, and more.