MI6: Secure Enclaves in a Speculative Out-of-Order Processor
This addresses security vulnerabilities in processors for systems requiring strong isolation, such as cloud computing, though it builds incrementally on prior work like Sanctum.
The paper tackles the problem of microarchitectural side-channel attacks breaking process isolation by proposing MI6, a speculative out-of-order processor that provides secure enclaves, resulting in an average 16.4% slowdown for protected programs as measured with SPEC CINT2006 benchmarks.
Recent attacks have broken process isolation by exploiting microarchitectural side channels that allow indirect access to shared microarchitectural state. Enclaves strengthen the process abstraction to restore isolation guarantees. We propose MI6, an aggressive, speculative out-of-order processor capable of providing secure enclaves under a threat model that includes an untrusted OS and an attacker capable of mounting any software attack currently considered practical, including control flow speculation attacks. MI6 is inspired by Sanctum [16] and extends its isolation guarantee to more realistic memory hierarchies. It also introduces a purge instruction, which is used only when a secure process is scheduled, and implements it for a complex processor microarchitecture. We model the performance impact of enclaves in MI6 through FPGA emulation on AWS F1 FPGAs by running SPEC CINT2006 benchmarks on top of an untrusted Linux OS. Security comes at the cost of approximately 16.4% average slowdown for protected programs.