The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Tuesday, August 24, 2021

All your CPUs belong to us

As if writing software without exploits is hard enough, now we have the most popular computer architecture, the Intel x86 line of CPUs, with a potential hole large enough to drive the NSA through. In a DEF CON talk, Christopher Domas shows how he found an exploit on a particular version of the x86 CPU that allowed him to gain total control over the computer without the operating system even knowing about it. All it involved is one undocumented instruction that enables access to a hidden CPU inside the x86 CPU (or rather, perhaps allow direct access to the underlying core that is simply interpreting the x86 ISA) followed by multiple copies of an x86 instruction that actually feeds instructions directly to this inner CPU that bypass all system checks because this inner CPU has access to everything (from user mode, and if you understand that statement, you know how bad it is).

As mentioned, this is only for a particular x86 implementation, but who knows what evils lurk in the heart of CPUs?

Probably the NSA.

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