Re: [RFC] Randomness on confidential computing platforms

[H. Peter Anvin]

On January 29, 2024 8:41:49 AM PST, "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>On Mon, Jan 29, 2024 at 08:30:11AM -0800, Dave Hansen wrote:
>> On 1/26/24 05:42, Kirill A. Shutemov wrote:
>> > 3. Panic after enough re-tries of RDRAND/RDSEED instructions fail.
>> >    Another DoS variant against the Guest.
>> 
>> I think Sean was going down the same path, but I really dislike the idea
>> of having TDX-specific (or CoCo-specific) policy here.
>> 
>> How about we WARN_ON() RDRAND/RDSEED going bonkers?  The paranoid folks
>> can turn on panic_on_warn, if they haven't already.
>
>Sure, we can do it for kernel, but we have no control on what userspace
>does.
>
>Sensible userspace on RDRAND/RDSEED failure should fallback to kernel
>asking for random bytes, but who knows if it happens in practice
>everywhere.
>
>Do we care?
>

You can't fix what you can't touch.