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From: "adhemerval.zanella at linaro dot org"
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Subject: [Bug libc/29437] arc4random is too slow
Date: Mon, 08 Aug 2022 12:42:46 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29437

--- Comment #11 from Adhemerval Zanella <adhemerval.zanella at linaro dot o=
rg> ---
(In reply to Florian Weimer from comment #8)
> (In reply to Cristian Rodr=C3=ADguez from comment #4)
> > (In reply to Miroslav Lichvar from comment #0)
> >=20
> > > This can be fixed easily in the chrony source code, but I thought it =
might
> > > be a good example of a real-world application impacted by this change=
 and
> > > there could be others.
> >=20
> > You need a PRNG, seeded by a single call to arc4random_buf.. (xoroshiro=
128+?)
> > People are unfortunately rejecting your usecase as invalid because this=
 does
> > not require a csprng. :-( (to me that sums up everything that is wrong,=
 you
> > known you don't need one, but notmal averege joe programmer has no idea=
 of
> > all the subtleties ans is stuck with using random() ..)
>=20
> Absolutely not. The idea behind arc4random is that an entire distribution
> can use this function without worrying performance or properties of the
> generated stream of randomness. It was designed for a search-and-replace =
of
> calls to random, without case-by-case reviews if the change is actually
> required for security reasons. If the glibc implementation does not meet
> that, we have failed.

I disagree that we have failed, the main problem is that arc4random
implementation from OpenBSD (which is copied on multiple systems and librar=
ies)
did not take into consideration the problems Jason has raised, and thus now
callers expect a certain performance on any possible system (even if the
cryptographic secure part can not be safely enforced).

So the question is should we trade performance or correctness?

--=20
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