[Cryptography] OpenSSL CSPRNG work

[Florian Weimer]

* Theodore Ts'o:

> On Wed, Jul 05, 2017 at 11:18:26PM +0200, Florian Weimer wrote:
>> 
>> I already wrote that we're going to use AT_RANDOM (and reseed using
>> getrandom once it returns data with GRND_NONBLOCK).  If that AT_RANDOM
>> value is not random, it's up to you guys to fix that.
>
> You do know that AT_RANDOM is only present in 2.6.29+ kernels, right?

It's in 2.6.32, which is good enough for me.  The actual limit is 3.2
these days, even.

> Are you planning on supporting kernels older than that?  What happens
> if a user tries calling arc4random() and they are running on a kernel
> which predates AT_RANDOM?

We refuse to start on such kernels anyway because they lack other
critical functionality.

> Super-early in the boot process, there may not be a whole lot that we
> can do on crappy hardware.

I've seen system boot logs where the SSH prints the key generation
message after the kernel message indicating that the pool has been
initialized.  And that was about as non-crappy as gets (x86-64 running
under KVM, where control *everything*, probably even with RDRAND).
Admittedly, it was three years ago:

<https://mail.gnome.org/archives/ostree-list/2014-February/msg00010.html>

Has this changed?

Or are the kernel messages just misleading for modern systems?