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AMD CacheWarp Vulnerability Afflicts Previous Gen EPYC Server CPUs, Patch Issued
(www.tomshardware.com)
this post was submitted on 15 Nov 2023
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As the commenter under that article stated, it's odd that AMD designed SEV in a way that the initial value is enough to pass the authentication.
cmon, thats quite normal
- the NSA, probably
This is incorrect, the "default value" is a poorly translated example from the german article - this exploit does NOT rely on resetting any SEV-specific memory or similar.
I re-read the article and the original ComputerBase article, and I think I have a better understanding of it now. You can read my update and let me know if I'm still misunderstanding it.
Yes, you understood correctly.
This is also not a rare occurence, you can programmatically find locations in a binary where un-doing a cached write allows manipulating control flow - there are more examples in the paper.
You will likely find these locations (called gadgets) in just about every binary - not because all devs are stupid and set the default to the "exploitable" case, but because this is how compiler code generation pans out in the grand scheme of things.
It's similar to when Mac OS accepted an empty password at login.
Pretty sure this sub will use the same defense as /r/apple did.
I haven't seen anyone defend AMD with this, so I think we're doing okay for now.