[Slashdot] - MIT Researchers Uncover 'Unpatchable' Flaw in Apple M1 Chips

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. TechCrunch reports: 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.

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