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MIT researchers uncover 'unpatchable' flaw in Apple M1 chips – TechCrunch:
Apple's M1 chips have an "unpatchable" hardware vulnerability that could allow attackers to break through its last line of security defenses, MIT researchers have discovered.
The vulnerability lies in a hardware-level security mechanism utilized in Apple M1 chips called pointer authentication codes, or PAC. This feature makes it much harder for an attacker to inject malicious code into a device's memory and provides a level of defense against buffer overflow exploits, a type of attack that forces memory to spill out to other locations on the chip.
Researchers from MIT's Computer Science and Artificial Intelligence Laboratory, however, have created a novel hardware attack, which combines memory corruption and speculative execution attacks to sidestep the security feature. The attack shows that pointer authentication can be defeated without leaving a trace, and as it utilizes a hardware mechanism, no software patch can fix it.
The attack, appropriately called "Pacman," works by "guessing" a pointer authentication code (PAC), a cryptographic signature that confirms that an app hasn't been maliciously altered. This is done using speculative execution — a technique used by modern computer processors to speed up performance by speculatively guessing various lines of computation — to leak PAC verification results, while a hardware side-channel reveals whether or not the guess was correct.
What's more, since there are only so many possible values for the PAC, the researchers found that it's possible to try them all to find the right one.
In a proof of concept, the researchers demonstrated that the attack even works against the kernel — the software core of a device's operating system — which has "massive implications for future security work on all ARM systems with pointer authentication enabled," says Joseph Ravichandran, a PhD student at MIT CSAIL and co-lead author of the research paper.
[Also Covered By]: Gizmodo
[Paper PDF]: PACMAN: Attacking ARM Pointer Authentication with Speculative Execution
(Score: 3, Interesting) by bradley13 on Sunday June 12 2022, @02:41PM (2 children)
Not sure how serious this flaw is, but it is yet another flaw based 9ff of side-channel attacks from speculative execution.
Hete's a thought: maybe speculative execution is just a dumb idea. Drop it, and you also massively simplify (and shrink) the cores, giving you more space for cache. I expect the performance hit would be fairly small.
Everyone is somebody else's weirdo.
(Score: 0) by Anonymous Coward on Monday June 13 2022, @02:04AM
Unless speculative execution was specifically introduced as a feature to enable side channel attacks for exfiltrating encryption keys. America, fuck yeah!
(Score: 2) by fraxinus-tree on Monday June 13 2022, @08:31AM
Speculative execution is an inevitable idea - as long as you don't want to sacrifice half of the performance. It is not that the speculative execution is bad, it is that stupid design shortcuts are bad.