Systematic Prevention of On-Core Timing Channels by Full Temporal Partitioning
Nils Wistoff, Moritz Schneider, Frank K. Gürkaynak, Gernot Heiser, Luca Benini · IEEE Transactions on Computers · 2022
Microarchitectural timing channels enable unwanted information flow across security boundaries, violating fundamental security assumptions. They leverage timing variations of several state-holding microarchitectural components and have been demonstrated across instruction set architectures and hardware implementations. Analogously to memory protection, (Ge et al. 2019) have proposedtime protectionfor preventing information leakage via timing channels. They also showed that time protection calls for hardware support. This work leverages the open and extensible RISC-V instruction set architecture (ISA) to introduce the temporal fence instructionfence.t, which provides the required mechanisms by clearing vulnerable microarchitectural state and guaranteeing a history-independent context-switch latency. We propose and discuss three different implementations offence.tand implement them on an experimental version of the seL4 microkernel (Klein et al. 2014) and CVA6, an open-source, in-order, application class, 64-bit RISC-V core (Zaruba and Benini 2019). We find that a complete, systematic, ISA-supported erasure of all non-architectural core components is the most effective implementation while featuring a low implementation effort, a minimal performance overhead of less than 1%, and negligible hardware costs.