SecurityCloak: : Protection against cache timing and speculative memory access attacks

Microarchitectural innovations such as deep cache hierarchies, out-of-order execution, branch prediction and speculative execution in modern processors have made possible to meet ever-increasing demands for performance. However, these innovations have inadvertently introduced vulnerabilities that are exploited by cache-side channel attacks such as Flush & Reload, Prime & Probe, Evict & Time, and attacks such as Spectre and Meltdown that exploit speculative executions. These attacks can potentially leak information which should be secured.

Mitigating the attacks while preserving the performance of out-of-order execution has been a challenge. Previous hardware mitigation techniques against cache timing or side-channel attacks include complex cache indexing mechanisms, encrypting addresses, partitioning cache memories, assigning specific ways of a set for each process, or obfuscating cache accesses by using ghost threads. Previous techniques for preventing or at least mitigating attacks based on speculative executions include hiding speculative data accesses using separate buffers or caches, or undoing the effects of speculation throughout program execution. Most techniques address either attacks that exploit speculation such as Spectre or cache side-channel attacks but not both. In many cases, changes to the microarchitecture with additional hardware are needed to implement the security protection. In some cases the mitigations cause performance penalties. In contrast we present very simple designs aimed at preventing both timing based cache side-channel attacks and Spectre style attacks based on speculative executions. Our approach combines obfuscation of cache timing making it more difficult for side-channel attacks to succeed and delaying speculative data accesses that miss in cache until the speculation is resolved. We will show that these approaches prevent both timing attacks such as Flush & Reload, Prime & Probe, Evict & Time as well as speculative attacks such as Spectre. Our technique requires very minimal changes to hardware.