A new side-channel attack dubbed “ GoFetch ” affects Apple M1, M2, and M3 processors and can be used to steal secret crypto keys from data in the CPU ’s cache .
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The attack targets implementations of fixed-time cryptographic functions using data memory-dependent prefetchers (DMPs) found in modern Apple processors. This allows it to replicate private crypto keys for various algorithms, including OpenSSL Diffie-Hellman, Go RSA, CRYSTALS Kyber, and Dilithium from the CPU cache.
GoFetch was developed for stealing crypto keys by a team of seven researchers from various universities in the US, who reported their findings to Apple on December 5, 2023.
Unfortunately, since this is a vulnerability , there is no way to patch it on affected processors. While it would be possible to address the flaws using software solutions, this would result in a reduction in the performance of cryptographic functions on these processors.
The GoFetch attack targets prefetchers that depend on data memory, a CPU function designed to improve computer performance when executing code.
A prefetcher is trained by previous memory accesses during data retrieval, allowing it to predict what data the computer will need next. This data is prefetched from slower memory locations to faster memory locations, such as the CPU cache.
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If the prediction is correct, the data is now quickly available, increasing the computer. If the prediction was wrong, the CPU simply requests the correct data as usual.
The GoFetch attack focuses on a newer prefetcher called a data memory-dependent prefetcher (DMP) for stealing crypto keys. This prefetcher can also be trained based on previous memory accesses, but it can also examine data values in memory to determine what should be preloaded into the cache.
DMP is available on Apple silicon and Intel's 13th generation Raptor Lake processors . However, the researchers say Intel 's implementation is more restrictive and prevents the attack .
The attack focuses on cryptographic implementations that require the same execution time regardless of the input (constant time), which is a security measure to prevent leakage of sensitive data.
Specifically, the researchers identified a flaw in Apple's DMP system implementation that violates good fixed-time practices.
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What are the modern techniques for dealing with side-channel attacks?
Modern techniques for dealing with side-channel attacks, such as the GoFetch attack that steals crypto keys, primarily involve the application of cryptographic methods. These methods seek to hide information that could be used to execute a side-channel attack, such as memory usage patterns or power consumption. In addition, the use of secure operating systems and hardware can help protect against side-channel attacks. These systems are designed in such a way that they reduce the possibility of sensitive information leaking through parallel channels. Another technique is the use of redistribution. This means that the information that a system processes is dispersed across different parts of the system, making it difficult to extract useful information from a side-channel attack.
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Source: bleepingcomputer
