Salus: A Practical Trusted Execution Environment for CPU-FPGA Heterogeneous Cloud Platforms

CPU-FPGA heterogeneous architectures have become increasingly popular in cloud environments for accelerating compute-intensive tasks. Ensuring the protection of sensitive data processed by these architectures requires the presence of a trusted execution environment (TEE). This work highlights the requirements for designing an FPGA TEE, the challenges faced in deploying existing solutions on commercial-off-the-shelf (COTS) cloud FPGA services, and the limitations of previous works that primarily focus on standalone FPGA TEEs. In response to these challenges, Salus introduces an innovative approach by leveraging an enclave running on the host with a TEE-enabled CPU. This approach aims to protect and attest the bitstream loaded on the FPGA side. By repurposing COTS FPGA bitstream utilities in a novel manner and adopting a proposed security-enhanced FPGA IP, Salus presents a practical design for an FPGA TEE, with minor efforts required.