Are Microarchitectural Attacks still possible on Flawless Hardware?

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Presented at RuhrSecBochum 2019 by

Michael Schwarz

Erik Kraft

In recent years, we have seen that optimizations in processors often enable new microarchitectural side channels. The severity of side-channel attacks varies widely, from small annoyances for which developers have to introduce workarounds in software, to highly critical attacks leaking arbitrary memory contents. While new attacks pop up regularly, finding defenses is not a trivial task. In this talk, we first briefly overview the state of the art of microarchitectural attacks and defenses. We then assume that we have a futuristic CPU which magically hides all microarchitectural side effects, rendering all known attacks useless. Even in this thought experiment, we show that such attacks are not dead. In fact, we present ways of mounting well-known microarchitectural attacks without relying on any hardware effects, making these attacks hardware agnostic. We show that attack primitives exploiting the hardware can be shifted to the software level, making these attacks easier to mount and independent of the CPU. The attacks that we present work on Windows, Linux, and Android, both on x86 and ARM processors.