[Buildroot] [PATCH] initscripts: Make installation of S20urandom optional.

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, Christoph, Al,

On 2020-07-19 10:05 +0200, Thomas Petazzoni spake thusly:
> On Sun, 19 Jul 2020 00:44:44 +0200
> christoph.muellner at theobroma-systems.com wrote:
> 
> > From: Christoph M?llner <christoph.muellner@theobroma-systems.com>
> > 
> > S20urandom is a nice script. However, there are systems, which
> > cannot make use of that script for some reasons (e.g. systems that
> > only have read-only partitions).
> > 
> > So let's install S20urandom only if configured to do so
> > (with default y to keep backwards-compatibility).
> > 
> > Signed-off-by: Christoph M?llner <christoph.muellner@theobroma-systems.com>
> 
> Hm, indeed it saves to /var/lib/random-seed, which we do not seem to
> symlink to a tmpfs place when the rootfs is read-only. I'm not entirely
> sure we want to add yet another option for this, or if we want to fix
> it so that it "works" even in read-only rootfs scenarios. I don't have
> a very clear opinion on how to handle that.

I too don't think that warrants a kconfig option.

I would however believe this script is not interesting at all. In fact,
an ambedded device seldom reboots nicely; instead, it is most often a
hard-reboot (with a power cycle). In that case, the script would have no
chance whatsoever to save the current seed before shutdown, thus on next
boot we would restore a seed that would have already been used, thus
defeating randomness to begin with; worse, it would give people a sense
of security where there would in fact be a hole.

If people do not have a good source of randomness in their kernel and/or
hardware, they should switch to using things like rng-tools with
jitterentropy or the likes, rather than rely on saving and restoring the
seed.

It is my opinion that we should just drop that startup script altogether
and be done with it.

Regards,
Yann E. MORIN.

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