New GoFetch attack on Apple Silicon CPUs can steal crypto keys

A new side-channel attack called "GoFetch" impacts Apple M1, M2, and M3 processors and can be used to steal secret cryptographic keys from data in the CPU's cache. The attack targets constant-time cryptographic implementations using data memory-dependent prefetchers (DMPs) found in modern Apple CPUs. This allows it to recreate the private cryptographic keys for various algorithms, including OpenSSL Diffie-Hellman, Go RSA, CRYSTALS Kyber, and Dilithium from the CPU's cache. GoFetch was developed by a team of seven researchers from various universities in the U.S., who reported their findings to Apple on December 5, 2023. However, as this is a hardware-based vulnerability, there is no way to fix it in impacted CPUs. While it would be possible to mitigate the flaws using software fixes, this would cause a performance hit on these CPUs' cryptographic functions. The GoFetch attack targets data memory-dependent prefetchers, a CPU feature designed to improve computer performance when executing code. A prefetcher is trained by previous accesses to memory when retrieving data, allowing it to predict what data the computer will need next. This data is then fetched in advance from slower parts of memory into faster memory regions, like the CPU cache. If the prediction is accurate, the data is now quickly available, increasing the computer's performance. If the guess was wrong, the CPU simply requests the correct data as usual. The GoFetch attack focuses on a newer prefetcher called a d...