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

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > Very much so, thanks again. What I take away from your results is:
> >
> > - RNDADDTOENTCNT is in active use in a safe way. Sure, RNDADDENTROPY
> > is still much better, but RNDADDTOENTCNT isn't entirely broken in the
> > above configurations either.
> > - This patch would make RNDADDTOENTCNT unsafe for some of the above
> > configurations in a way that it currently isn't unsafe.
> > - 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.
> 
> Based on this, the fact that shell scripts cannot seed the RNG anyway,
> and due to the hazards in trying to retrofit some heuristics onto an
> interface that was never designed to work like this, I'm convinced at
> this point that the right course of action here is to leave this
> alone. There's no combination of /dev/urandom write hacks/heuristics
> that do the right thing without creating some big problem elsewhere.
> It just does not have the right semantics for it, and changing the
> existing semantics will break existing users.
> 
> In light of that conclusion, I'm going to work with every userspace
> downstream I can find to help them fix their file-based seeding, if it
> has bugs. I've started talking with the buildroot folks, and then I'll
> speak with the OpenRC people (being a Gentoo dev, that should be easy
> going). Systemd does the right thing already.
> 
> I wrote a little utility for potential inclusion in
> busybox/util-linux/whatever when it matures beyond its current age of
> being half hour old:
> - https://git.zx2c4.com/seedrng/about/
> - https://git.zx2c4.com/seedrng/tree/seedrng.c
> So I'll see what the buildroot people think of this and take it from there.

You could put it into the kernel into tools/ directory...

Best regards,
									Pavel