linux-kernel - Re: [kernel-hardening] Re: [PATCH v7 3/6] random: use SipHash in place of MD5

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Message-ID: <CAHmME9q_NkVVCG8hYw_NMjTLsBUoEq334i+jG+yvXOKR+wY6Xw@mail.gmail.com>
Date:   Thu, 22 Dec 2016 19:13:39 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:     "Theodore Ts'o" <tytso@....edu>,
        kernel-hardening@...ts.openwall.com,
        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: [kernel-hardening] Re: [PATCH v7 3/6] random: use SipHash in
 place of MD5

On Thu, Dec 22, 2016 at 7:08 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> I wasn't concerned about performance but more about DoS resilience. I
> wonder how safe half md4 actually is in terms of allowing users to
> generate long hash chains in the filesystem (in terms of length
> extension attacks against half_md4).

AFAIK, this is a real vulnerability that needs to be addressed.

Judging by Ted's inquiry about my siphash testing suite, I assume he's
probably tinkering around with it as we speak. :)

Meanwhile I've separated things into several trees:

1. chacha20 rng, already submitted:
https://git.zx2c4.com/linux-dev/log/?h=random-next

2. md5 cleanup, not yet submitted:
https://git.zx2c4.com/linux-dev/log/?h=md5-cleanup

3. md4 cleanup, already submitted:
https://git.zx2c4.com/linux-dev/log/?h=ext4-next-md4-cleanup

4. siphash and networking, not yet submitted as a x/4 series:
https://git.zx2c4.com/linux-dev/log/?h=net-next-siphash

I'll submit (4) in a couple of days, waiting for any comments on the
existing patch-set.

Jason