Re: Google hacks Zen 2 to 4 microcode

Anton Ertl <anton@mips.complang.tuwien.ac.at> schrieb:

mitchalsup@aol.com (MitchAlsup1) writes:

I was an architect at AMD when we put microcode patching in the chips.
We did understand that the encryption and keys were not sufficiently
strong at that instant in time, and there were other driving factors.
>
But, I am surprised that it took this long to break (~22 years).

>
I have heard at least one talk (IIRC at 34C3, 35C3, or 36C3) about
patching microcode for some then-older AMD processors (IIRC Phenoms).
They could not do it for then-current AMD CPUs because of the
encryption, so maybe AMD improved the encryption between your time and
Zen2-Zen4.  But obviously not enough.

They used the default AES key from the original publication :-)

While it's interesting if you can play around with the microcode of
your hardware, the perspective that an attacker might subvert your
hardware at the microcode level is worrying.

Which is why it has a CVE number.

But I liked them modifying the random number instruction so
it always returned 4.  Somebody's been reading the classics...
https://xkcd.com/221/