New 'GoFetch' Apple CPU Attack Exposes Crypto Keys

'There is a new side channel attack against Apple 'M' series CPUs that does not appear to be fixable without a major performance hit,' writes Slashdot reader EncryptedSoldier. SecurityWeek reports: A team of researchers representing several universities in the United States has disclosed the details of a new side-channel attack method that can be used to extract secret encryption keys from systems powered by Apple CPUs. The attack method, dubbed GoFetch, has been described as a microarchitectural side-channel attack that allows the extraction of secret keys from constant-time cryptographic implementations. These types of attacks require local access to the targeted system. The attack targets a hardware optimization named data memory-dependent prefetcher (DMP), which attempts to prefetch addresses found in the contents of program memory to improve performance.

The researchers have found a way to use specially crafted cryptographic operation inputs that allow them to infer secret keys, guessing them bits at a time by monitoring the behavior of the DMP. They managed to demonstrate end-to-end key extraction attacks against several crypto implementations, including OpenSSL Diffie-Hellman Key Exchange, Go RSA, and the post-quantum CRYSTALS-Kyber and CRYSTALS-Dilithium. The researchers have conducted successful GoFetch attacks against systems powered by Apple M1 processors, and they have found evidence that the attack could also work against M2 and M3 processors. They have also tested an Intel processor that uses DMP, but found that it's 'more robust' against such attacks.

The experts said Apple is investigating the issue, but fully addressing it does not seem trivial. The researchers have proposed several countermeasures, but they involve hardware changes that are not easy to implement or mitigations that can have a significant impact on performance. Apple told SecurityWeek that it thanks the researchers for their collaboration as this work advances the company's understanding of these types of threats. The tech giant also shared a link to a developer page that outlines one of the mitigations mentioned by the researchers. The researchers have published a paper (PDF) detailing their work.

Ars Technica's Dan Goodin also reported on the vulnerability.

Read more of this story at Slashdot.