The recent Hertzbleed disclosure demonstrates how remote-timing analysis can reveal secret information previously only accessible to local-power analysis. At worst, this constitutes a fundamental break in the constant-time programming principles and the many deployed programs that rely on them. But all hope is not lost. Hertzbleed relies on a coarse-grained, noisy channel that is difficult to exploit. Indeed, the Hertzbleed paper required a bespoke cryptanalysis to attack a specific cryptosystem (SIKE). Thus, it remains unclear if Hertzbleed represents a threat to the broader security ecosystem.In this paper, we demonstrate that Hertzbleed’s effects are wide ranging, not only affecting cryptosystems beyond SIKE, but also programs beyond cryptography, and even computations occurring outside the CPU cores. First, we demonstrate how latent gadgets in other cryptosystem implementations— specifically "constant-time" ECDSA and Classic McEliece— can be combined with existing cryptanalysis to bootstrap Hertzbleed attacks on those cryptosystems. Second, we demonstrate how power consumption on the integrated GPU influences frequency on the CPU—and how this can be used to perform the first cross-origin pixel stealing attacks leveraging "constant-time" SVG filters on Google Chrome.

Microarchitectural side-channel attacks are enjoying a time of explosive growth, mostly fueled by novel transient execution vulnerabilities. These attacks are capable of leaking arbitrary data, as long as it is possible for the adversary to read that data into the processor core using transient instructions. In this paper, we present the first microarchitectural attack that leaks data at rest in the memory system, i.e., never directly read into the core speculatively or non-speculatively. This technique is enabled by a previously unreported class of prefetcher: a data memory-dependent prefetcher (DMP). These prefetchers are designed to allow prefetching of irregular address patterns such as pointer chases. As such, DMPs examine and use the contents of memory directly to determine which addresses to prefetch. Our experiments demonstrate the existence of a pointer-chasing DMP on recent Apple processors, including the A14 and M1. We then reverse engineer the details of this DMP to determine the opportunities for and restrictions it places on attackers using it. Finally, we demonstrate several basic attack primitives capable of leaking pointer values using the DMP.