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Message-ID: <1482421900.2673.3.camel@stressinduktion.org>
Date: Thu, 22 Dec 2016 16:51:40 +0100
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: kernel-hardening@...ts.openwall.com, Theodore Ts'o <tytso@....edu>, Andy
Lutomirski <luto@...capital.net>, Netdev <netdev@...r.kernel.org>, LKML
<linux-kernel@...r.kernel.org>, Linux Crypto Mailing List
<linux-crypto@...r.kernel.org>, David Laight <David.Laight@...lab.com>,
Eric Dumazet <edumazet@...gle.com>, Linus Torvalds
<torvalds@...ux-foundation.org>, Eric Biggers <ebiggers3@...il.com>, Tom
Herbert <tom@...bertland.com>, Andi Kleen <ak@...ux.intel.com>, "David S.
Miller" <davem@...emloft.net>, Jean-Philippe Aumasson
<jeanphilippe.aumasson@...il.com>
Subject: Re: Re: [PATCH v7 3/6] random: use SipHash in
place of MD5
On Thu, 2016-12-22 at 16:41 +0100, Jason A. Donenfeld wrote:
> Hi Hannes,
>
> On Thu, Dec 22, 2016 at 4:33 PM, Hannes Frederic Sowa
> <hannes@...essinduktion.org> wrote:
> > IPv6 you cannot touch anymore. The hashing algorithm is part of uAPI.
> > You don't want to give people new IPv6 addresses with the same stable
> > secret (across reboots) after a kernel upgrade. Maybe they lose
> > connectivity then and it is extra work?
>
> Ahh, too bad. So it goes.
If no other users survive we can put it into the ipv6 module.
> > The bpf hash stuff can be changed during this merge window, as it is
> > not yet in a released kernel. Albeit I would probably have preferred
> > something like sha256 here, which can be easily replicated by user
> > space tools (minus the problem of patching out references to not
> > hashable data, which must be zeroed).
>
> Oh, interesting, so time is of the essence then. Do you want to handle
> changing the new eBPF code to something not-SHA1 before it's too late,
> as part of a new patchset that can fast track itself to David? And
> then I can preserve my large series for the next merge window.
This algorithm should be a non-seeded algorithm, because the hashes
should be stable and verifiable by user space tooling. Thus this would
need a hashing algorithm that is hardened against pre-image
attacks/collision resistance, which siphash is not. I would prefer some
higher order SHA algorithm for that actually.
Bye,
Hannes
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