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So what does SEV actually protect against? Something like heartbleed would still happily decrypt and transmit confidential data. Something like speculative si
by eloff 6y ago
So what does SEV actually protect against?
Something like heartbleed would still happily decrypt and transmit confidential data.
Something like speculative side channel attacks would still speculate on the unencrypted memory right?
Rowhammer would still flip bits, but now one bit flipping would turn an entire 128 bit block into garbage when decrypted? It seems like that would at least make rowhammer a lot harder to exploit into a privilege escalation. ECC memory already gave some limited protection here.
- theevilsharpie 6y ago> Something like speculative side channel attacks would still speculate on the unencrypted memory right? This wouldn't prevent a Spectre attack or similar cache-based attack, as the memory would be decrypted at that point. However, it would mitigate attacks like Meltdown or Rowhammer.
- eloff 6y agoI don't see how it protects against meltdown, wouldn't the memory still get decrypted by the escalated access? Edit: If each VM has it's own key, then they couldn't read each other's memory with meltdown. I think that must be the angle.
- theevilsharpie 6y ago> I don't see how it protects against meltdown, wouldn't the memory still get decrypted by the escalated access? No. A particular VM's memory is decrypted by that VM's key. Assuming that AMD's CPUs were vulnerable to a hypothetical attack similar to Meltdown, either a VM or a guest would be able to dump the machine's memory, but the memory contents belonging to other VMs would be encrypted and unintelligible.
- eloff 6y agoI think my edit and your comment passed each other on the wire. That makes sense, it gives hardware protection from privilege escalation between VMs on the same host. Be it through a hardware exploit or hypervisor vulnerability.