Re: [PATCH] tpm: Salt tpm_get_random() result with get_random_bytes()

[Jarkko Sakkinen]

On Wed, Oct 16, 2019 at 10:02:01AM +0300, Janne Karhunen wrote:
> On Tue, Oct 15, 2019 at 3:50 PM Jarkko Sakkinen
> <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> >
> > Salt the result that comes from the TPM RNG with random bytes from the
> > kernel RNG. This will allow to use tpm_get_random() as a substitute for
> > get_random_bytes().  TPM could have a bug (making results predicatable),
> > backdoor or even an inteposer in the bus. Salting gives protections
> > against these concerns.
> 
> The current issue in the randomness from my point of view is that
> encrypted filesystems, ima etc in common deployments require high
> quality entropy just few seconds after the system has powered on for
> the first time. It is likely that people want to keep their keys
> device specific, so the keys need to be generated on the first boot
> before any of the filesystems mount.

This patch does not have the described issue.

Which call sites are you talking about?

/Jarkko