linux-kernel - Re: [PATCH v2 2/2] random: use BLAKE2s instead of SHA1 in extraction

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Message-ID: <CAMuHMdW+Od70XTNbnNxL3qXgetZ9QDLeett6u5vg9Wr6atxD=w@mail.gmail.com>
Date:   Tue, 11 Jan 2022 13:51:36 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Theodore Tso <tytso@....edu>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>,
        bpf <bpf@...r.kernel.org>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] random: use BLAKE2s instead of SHA1 in extraction

Hi Jason,

CC bpf, netdev

On Tue, Jan 11, 2022 at 1:28 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
> On Tue, Jan 11, 2022 at 12:38 PM Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
> > Unfortunately we cannot get rid of the sha1 code yet (lib/sha1.o is
> > built-in unconditionally), as there are other users...

kernel/bpf/core.c and net/ipv6/addrconf.c
Could they be switched to blake2s, too?

> I think that's just how things go and a price for progress. We're not
> going to stick with sha1, and blake2s has some nice properties that we
> certainly want. In the future hopefully this can decrease in other
> ways based on other future improvements. But that's where we are now.
>
> If you're really quite concerned about m68k code size, I can probably
> do some things to reduce that. For example, blake2s256_hmac is only
> used by wireguard and it could probably be made local there. And with
> some trivial loop re-rolling, I can shave off another 2300 bytes. And
> I bet I can find a few other things too. The question is: how
> important is this to you?

No problem, I just try to report all measurable impact on kernel size,
so there is some record of it.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds