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Date:      Tue, 24 Feb 2015 15:19:21 -0800
From:      John-Mark Gurney <jmg@funkthat.com>
To:        Alfred Perlstein <alfred@freebsd.org>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, Harrison Grundy <harrison.grundy@astrodoggroup.com>, freebsd-arch@freebsd.org
Subject:   Re: locks and kernel randomness...
Message-ID:  <20150224231921.GQ46794@funkthat.com>
In-Reply-To: <54ECEA43.2080008@freebsd.org>
References:  <20150224012026.GY46794@funkthat.com> <20150224015721.GT74514@kib.kiev.ua> <54EBDC1C.3060007@astrodoggroup.com> <20150224024250.GV74514@kib.kiev.ua> <DD06E2EA-68D6-43D7-AA17-FB230750E55A@bsdimp.com> <20150224174053.GG46794@funkthat.com> <54ECBD4B.6000007@freebsd.org> <20150224182507.GI46794@funkthat.com> <54ECEA43.2080008@freebsd.org>

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Alfred Perlstein wrote this message on Tue, Feb 24, 2015 at 16:16 -0500:
> On 2/24/15 1:25 PM, John-Mark Gurney wrote:
> > Alfred Perlstein wrote this message on Tue, Feb 24, 2015 at 13:04 -0500:
> >> On 2/24/15 12:40 PM, John-Mark Gurney wrote:
> >>> Warner Losh wrote this message on Tue, Feb 24, 2015 at 07:56 -0700:
> >>>> Then again, if you want to change random(), provide a weak_random() that???s
> >>>> the traditional non-crypto thing that???s fast and lockless. That would make it easy
> >>>> to audit in our tree. The scheduler doesn???t need cryptographic randomness, it
> >>>> just needs to make different choices sometimes to ensure its notion of fairness.
> >>>
> >>> I do not support having a weak_random...  If the consumer is sure
> >>> enough that you don't need a secure random, then they can pick an LCG
> >>> and implement it themselves and deal (or not) w/ the locking issues...
> >>>
> >>> It appears that the scheduler had an LCG but for some reason the authors
> >>> didn't feel like using it here..
> >>
> >> The way I read this argument is that no low quality sources of
> >> randomness shall be allowed.
> >
> > No, I'm saying that the person who needs the predictable randomness
> > needs to do extra work to get it...  If they care that much about
> > performance/predictability/etc, then a little extra work won't hurt
> > them..  And if they don't know what an LCG is, then they aren't
> > qualified to make the decision that a weaker RNG is correct for their
> > situation..
> >
> >> So we should get rid of rand(3)?  When do we deprecate that?
> >
> > No, we should replace it w/ proper randomness like OpenBSD has...
> > I'm willing to go that far and I think FreeBSD should...  OpenBSD has
> > done a lot of leg work in tracking down ports that correctly use
> > rand(3), and letting them keep their deterministic randomness, while
> > the remaining get real random..
> >
> >> Your argument doesn't hold water.
> >
> > Sorry, you're argument sounds like it's from the 90's when we didn't
> > know any better on how to make secure systems...  Will you promise to
> > audit all new uses of randomness in the system to make sure that they
> > are using the correct, secure API?
> >
> > Considering that it's been recommended that people NOT use
> > read_random(9) for 14 years, yet people continue to use it in new code,
> > demonstrates that people do not know what they are doing (wrt
> > randomness), and the only way to make sure they do the correct, secure
> > thing is to only provide the secure API...
> 
> That speaks to more of the drive-by czars we have in BSD land that take 
> an area with a hard lock and then go away.

It also speaks to the airchair quarterbacking that stops people from
wanting to contribute...  Someone comes along and tries to make an
improvement, then x number of people raise their arms about oh, I
still use grdc (sorry dteske, not trying to pick on you) as tcp keep
alive, and then the person abandons or leaves incomplete the work that
they started...

I was very close to NOT posting the email to -arch, but after various
questions from twitter, and adrian's continued pleas to talk changes
more publicly, I decided to do so...  If people continue to react this
way, it just demonstrates that doing things publicly is NOT a way to
get things to move forward in FreeBSD, and people will continue to do
things in private...  Luckily, I'm consulting, so I have a few more
hours (for now) to fight these fights, but if it continues to be an
issue, we'll continue to have this problem of czars that come in, drop
a bunch of code and then leave, because dealing w/ this becomes too
expensive...

So far, only ONE person has commented on the patch on reviews, and that
is delphij...

> Also, do not want to attempt to be like openbsd, learn from for sure, 
> but to be like, no way.

I'm fine not being like OpenBSD, but as you said, we should learn from
them, and leverage their work...  Though I agree w/ OpenBSD's work to
replace random(3), it also isn't who FreeBSD is, but if we want to
continue to be relevant, we do need to take security seriously, and
IMO, this is one of those steps.

If someone does find a performance issue w/ my patch, I WILL work with
them on a solution, but I will not work w/ people who make unfounded
claims about the impact of this work...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."



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