Unpatchable vulnerability in Apple chip leaks secret encryption keys

Non mi pare così darmmatico come potrebbe sembrare a prima vista.

Intanto bisogna che l’attaccante stia facendo girare software localmente sulla macchina. E certo, potrebbe essere che forse qualcuno troverà il modo di farlo fare a un browser via javascript.

E si, non è patchable perchè è inscritto nel chip, ma possono essere messi dei controlli software per evitare che sia sfruttabile (risultando in un degrado di performance per certe operazioni)

Source: Ars Technica

A newly discovered vulnerability baked into Apple’s M-series of chips allows attackers to extract secret keys from Macs when they perform widely used cryptographic operations, academic researchers have revealed in a paper published Thursday.

The flaw—a side channel allowing end-to-end key extractions when Apple chips run implementations of widely used cryptographic protocols—can’t be patched directly because it stems from the microarchitectural design of the silicon itself. Instead, it can only be mitigated by building defenses into third-party cryptographic software that could drastically degrade M-series performance when executing cryptographic operations, particularly on the earlier M1 and M2 generations. The vulnerability can be exploited when the targeted cryptographic operation and the malicious application with normal user system privileges run on the same CPU cluster.

Beware of hardware optimizationsThe threat resides in the chips’ data memory-dependent prefetcher, a hardware optimization that predicts the memory addresses of data that running code is likely to access in the near future. By loading the contents into the CPU cache before it’s actually needed, the DMP, as the feature is abbreviated, reduces latency between the main memory and the CPU, a common bottleneck in modern computing.

…Prefetchers usually look at addresses of accessed data (ignoring values of accessed data) and try to guess future addresses that might be useful. The DMP is different in this sense as in addition to addresses it also uses the data values in order to make predictions (predict addresses to go to and prefetch). In particular, if a data value “looks like” a pointer, it will be treated as an “address” (where in fact it’s actually not!) and the data from this “address” will be brought to the cache. The arrival of this address into the cache is visible, leaking over cache side channels.

Continua qui: Unpatchable vulnerability in Apple chip leaks secret encryption keys | Ars Technica

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