Re: [PATCH v8 2/3] fdt: add support for rng-seed

[Theodore Y. Ts'o]

On Wed, Aug 21, 2019 at 09:39:28AM +0300, Ard Biesheuvel wrote:
> 
> Whether to trust the firmware provided entropy is a policy decision,
> and typically, we try to avoid dictating policy in the kernel, and
> instead, we try to provide a sane default but give the user control
> over it.
> 
> So in this case, we should probably introduce
> add_firmware_randomness() with a Kconfig/cmdline option pair to decide
> whether it should be trusted or not (or reuse the one we have for
> trusting RDRAND etc)

I'd call it add_bootloader_randomness(), since we are trusting the
*bootloader*; it's the bootloader which is vouching for the security /
validity of the passed-in entropy.  Furthermore, the bootloader on
some architectures might be fetching directly from some secure
element.

And for that reason, I'd use a different Kconfig/cmdline option pair
than the one used for trusting CPU-provided randomness.

						- Ted