linux-kernel - Re: [PATCH, RFC] random: introduce getrandom(2) system call

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Message-ID: <CALCETrV3pAFk-a+RrLzwQ0ct0dWoBsVdSVrHCMRD1n564YpUmA@mail.gmail.com>
Date:	Thu, 17 Jul 2014 14:37:34 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"Theodore Ts'o" <tytso@....edu>,
	Andy Lutomirski <luto@...capital.net>,
	Mark Kettenis <mark.kettenis@...all.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-crypto@...r.kernel.org, beck@...nbsd.org
Subject: Re: [PATCH, RFC] random: introduce getrandom(2) system call

On Thu, Jul 17, 2014 at 2:28 PM, Theodore Ts'o <tytso@....edu> wrote:
> On Thu, Jul 17, 2014 at 01:35:15PM -0700, Andy Lutomirski wrote:
>>
>> Can we please have a mode in which getrandom(2) can neither block nor
>> fail?  If that gets added, then this can replace things like AT_RANDOM.
>
> AT_RANDOM has been around for a long time; it's not something we can
> remove.

I'm not suggesting removing AT_RANDOM.  To the contrary, I'm
suggesting that libraries that need to seed some kind of
non-cryptographic, non-security-related RNG could use getrandom(2)
with appropriate flags rather than screwing around with getpid,
clock_gettime, etc.

For example:

unsigned int seed;
getrandom(&seed, sizeof(seed), GRND_BEST_EFFORT); /* Never fails on
new enough kernels */
srand(seed);

No error checking, no weird cases, and if the RNG isn't well seeded,
then I tried my best.

--Andy
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