ZEN AND THE ART OF MICROCODE HACKING

Summary from the TLDR InfoSec newsletter

This post details the concepts and tools behind EntrySign, the AMD Zen microcode signature validation vulnerability disclosed last month. It delves into microcode fundamentals, AMD's anti-tampering measures, and the specific vulnerability involving the CMAC hash function. It also announces the release of the Zentool suite, which consists of tools for microcode patch examination, including limited disassembly, microcode patch authoring using a limited amount of reverse-engineered assembly, microcode patch signing, and microcode patch loading.