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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
	Netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"Herbert Xu" <herbert@gondor.apana.org.au>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Jean-Philippe Aumasson" <jeanphilippe.aumasson@gmail.com>,
	"Linux Crypto Mailing List" <linux-crypto@vger.kernel.org>,
	"Erik Kline" <ek@google.com>,
	"Fernando Gont" <fgont@si6networks.com>,
	"Lorenzo Colitti" <lorenzo@google.com>,
	"Hideaki Yoshifuji" <hideaki.yoshifuji@miraclelinux.com>
Subject: Re: [PATCH RFC v1 2/3] ipv6: move from sha1 to blake2s in address calculation
Date: Fri, 14 Jan 2022 18:58:09 +0100	[thread overview]
Message-ID: <CAHmME9qy4-qkBAD9fJ6jqHxw2DYtscerZdriMYXw1T4iPD6Y-A@mail.gmail.com> (raw)
In-Reply-To: <3db9c306-ea22-444f-b932-f66f800a7a28@www.fastmail.com>

Hi Hannes,

On Fri, Jan 14, 2022 at 6:44 PM Hannes Frederic Sowa
<hannes@stressinduktion.org> wrote:
> I don't think we can argue our way out of this by stating that there are
> no guarantees anyway, as much as I would like to change the hash
> function as well.

Shucks. Alright then.

> As much as I know about the problems with SHA1 and would like to see it
> removed from the kernel as well, I fear that in this case it seems hard
> to do. I would propose putting sha1 into a compilation unit and
> overwrite the compiler flags to optimize the function optimized for size
> and maybe add another mode or knob to switch the hashing algorithm if
> necessary.

Already on it! :)
https://lore.kernel.org/linux-crypto/20220114154247.99773-3-Jason@zx2c4.com/

> I haven't investigated recent research into breakage of SHA1, I mostly
> remember the chosen-image and collision attacks against it. Given the
> particular usage of SHA1 in this case, do you think switching the
> hashing function increases security?

Considering we're only using 64-bits of SHA-1 output, I don't think
the SHA-1 collision attacks give you that much here. And it seems like
there are other network-level security concerns with the whole scheme
anyway. So it might not be the largest of matters. However...

> I am asking because of the desire
> to decrease the instruction size of the kernel

Indeed this is what I was hoping for.

Jason

  reply	other threads:[~2022-01-14 17:58 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-12 13:12 [PATCH RFC v1 0/3] remove remaining users of SHA-1 Jason A. Donenfeld
2022-01-12 13:12 ` [PATCH RFC v1 1/3] bpf: move from sha1 to blake2s in tag calculation Jason A. Donenfeld
2022-01-12 22:56   ` Toke Høiland-Jørgensen
2022-01-13  1:33     ` Alexei Starovoitov
2022-01-13 12:27       ` Jason A. Donenfeld
2022-01-13 22:45         ` Alexei Starovoitov
2022-01-14  8:33           ` Geert Uytterhoeven
2022-01-14 14:12           ` Jason A. Donenfeld
2022-01-14 15:08             ` Ard Biesheuvel
2022-01-14 15:20               ` Jason A. Donenfeld
2022-01-14 15:36                 ` Geert Uytterhoeven
2022-01-14 15:59                 ` David Laight
2022-01-14 16:19               ` Alexei Starovoitov
2022-01-14 16:34                 ` Jason A. Donenfeld
2022-01-14 23:04     ` Jeffrey Walton
2022-01-12 13:12 ` [PATCH RFC v1 2/3] ipv6: move from sha1 to blake2s in address calculation Jason A. Donenfeld
2022-01-12 15:49   ` Jason A. Donenfeld
2022-01-12 23:05   ` Toke Høiland-Jørgensen
2022-01-12 23:31     ` Jason A. Donenfeld
2022-01-13 11:15       ` Hannes Frederic Sowa
2022-01-13 12:06         ` Ard Biesheuvel
2022-01-13 12:22           ` Jason A. Donenfeld
2022-01-13 12:29             ` Ard Biesheuvel
2022-01-13 13:30           ` Toke Høiland-Jørgensen
2022-01-13 13:40             ` Ard Biesheuvel
2022-01-13 13:45             ` Jason A. Donenfeld
2022-01-13 13:50               ` Ard Biesheuvel
2022-01-13 13:54                 ` Jason A. Donenfeld
2022-01-13 16:18                   ` Toke Høiland-Jørgensen
2022-01-14 16:07         ` Jason A. Donenfeld
2022-01-14 16:57           ` Toke Høiland-Jørgensen
2022-01-14 17:41           ` Hannes Frederic Sowa
2022-01-14 17:58             ` Jason A. Donenfeld [this message]
2022-01-12 13:12 ` [PATCH RFC v1 3/3] crypto: sha1_generic - import lib/sha1.c locally Jason A. Donenfeld
2022-01-12 18:50 ` [PATCH RFC v1 0/3] remove remaining users of SHA-1 David Sterba
2022-01-12 18:57   ` Jason A. Donenfeld
2022-01-13  3:24 ` Sandy Harris
2022-01-13  8:08   ` Ard Biesheuvel
2022-01-13 17:28   ` Theodore Ts'o

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