Re: [RFC net-next 05/15] psp: add op for rotation of secret state

Jakub Kicinski
2024-05-29T17:43:03Z

On Thu, 16 May 2024 15:59:14 -0400 Lance Richardson wrote:
> On Thu, May 9, 2024 at 11:05 PM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > Rotating the secret state is a key part of the PSP protocol design.
> > Some external daemon needs to do it once a day, or so.
> > Add a netlink op to perform this operation.
> > Add a notification group for informing users that key has been
> > rotated and they should rekey (next rotation will cut them off).
> >
> Does this allow for the possibility of NIC firmware or the driver initiating
> a rotation? E.g. during key generation if the SPI space has been
> exhausted a rotation will be required in order to generate a new
> derived key.

I think it should be fine - I was designing with that use case in mind,
but ended up not needing it. We can export a driver facing function
which will basically perform the equivalent of psp_nl_key_rotate_doit().

I added the "key generation", because I worried that if unsynchronized
agents on multiple hosts can rotate the key - the chances of
double-rotation and immediate reuse of a SPI are much higher.
Not sure if the extra key generation bits are really necessary..
it seemed like a good idea at the time :)