cvs commit: src/games/fortune/fortune fortune.c

[Colin Percival]

Pawel Jakub Dawidek wrote:
> On Sun, Jul 24, 2005 at 04:06:02PM +0200, Poul-Henning Kamp wrote:
> +> In message <20050724135738.GM46538 at darkness.comp.waw.pl>, Pawel Jakub Dawidek writes:
> +> >We should probably test entropy quality on boot.
> +> >I've somewhere userland version of /sys/dev/rndtest/ which implements
> +> >FIPS140-2 tests for (P)RNGs. We can use put it into rc.d/ and warn users.
> +> 
> +> Anyway, back in this universe:  We should not stick a lot of stuff into
> +> our boot-time scripts, they are slow enough already.
> 
> I think such a tool will be still useful (even if not turned on by default),
> so one can turn it on when thinks it's needed:
> - on production machines,
> - on first start of rc.d/sshd (when you host keys are generated),
> - when you need to check if PRNG is the thing which makes your fortune
>   not to work properly (or instrument the user how to do it easly).

I think this would be more dangerous than valuable.  "Most" failure modes of
modern PRNGs will result in output which is cryptographically predictable but
passes all known statistical tests.  (To take a trivial example, the sequence
MD5(0), MD5(1), MD5(2) ... looks random, but obviously isn't.)

If we want to determine if the PRNG has been seeded properly, we should be
querying the kernel, not trying to distinguish between "random" and "non-random"
just based on its output.

Colin Percival