Re: [Security] [patch] random: make get_random_int() more random

From: Michael S. Zick
Date: Sat May 16 2009 - 10:00:30 EST


On Sat May 16 2009, Eric W. Biederman wrote:
> Ingo Molnar <mingo@xxxxxxx> writes:
>
> > * Willy Tarreau <w@xxxxxx> wrote:
> >
> >
> > Bad idea IMHO ...
> >
> > It is a bad idea because such sort of tunables do not really help
> > the user as those who tweak are a distinct minority.
> >
> > Also, having a two-way hack _hinders_ your good idea from being
> > adopted for example. Why bother with a faster hash and with using
> > the resulting bits sparingly if we can get an 'easy' tunable in and
> > can have two sub-par solutions instead of one (harder to implement)
> > good solution?
> >
> > So tunables are really counter-productive - and this is a pet peeve
> > of mine.
> >
> > Every time we have such a tunable for something fundamental we've
> > not improved the kernel, we've documented a _failure_ in kernel
> > design and implementation.
> >
> > Sure, we do use tunables for physical constants, limits and other
> > natural parameters - and _sometimes_ we just grudingly admit defeat
> > and admit that something is really impossible to implement. IMHO
> > here we are not at that point yet, at all.
>
> In the lwn comment section there was a suggestion to use a high
> quality stream cipher (AES?) instead of sha1 or the half md4 thing.
> Apparently those should be both stronger and faster.
>
> I don't know enough about it except to say that sounds right in
> principle.
>
> Apparently some of the BSDs do something similar with arc4random.
> arc4 is old and in some case broken so it is unlikely to make a good
> choice at this point, but the overall design of a stream cipher
> that is rekeyed ever 5 minutes seems sound.
>
> Eric
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>

And when building for the VIA processors that have the
hardware rng in the padlock firmware - -
Let the kernel use that for a high quality RNG.

Note: This may require a Kbuild tweak to force the via-rng
driver to be built-in if this solution is selected.

PS: I have two (different) VIA C7-M machines available for testing.

Mike
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