Re: [PATCH] random: allow writes to /dev/urandom to influence fast init

[Jason A. Donenfeld]

Hi David,

On Wed, Mar 23, 2022 at 8:01 AM David Laight <David.Laight@xxxxxxxxxx> wrote:
>
> From: Jason A. Donenfeld
> > Sent: 23 March 2022 04:48
> ...
> > - Plenty of things are seeding the RNG correctly, and buildroot's
> > shell script is just "doing it wrong".
> >
> > On that last point, I should reiterate that buildroot's shell script
> > still isn't actually initializing the RNG, despite what it says in its
> > echo; there's never been a way to initialize the RNG from a shell
> > script, without calling out to various special purpose ioctl-aware
> > binaries.
>
> Perhaps the very first write after boot could be assumed to
> be valid initialisation data?
> (On top of a few other tests.)

I addressed this already earlier. That approach does not work. Too
many things already pass in garbage, not expecting for it to be
credited, but just contributory. /dev/urandom writes simply has never
had the semantics one would want for credited seeding. Adding a
heuristic like this will break users.

Jason