netdev - Re: [PATCH 1/2] net: Toeplitz library functions

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Date:	Tue, 24 Sep 2013 08:54:24 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	David Miller <davem@...hat.com>
Cc:	David Laight <David.Laight@...lab.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: Re: [PATCH 1/2] net: Toeplitz library functions

On Tue, Sep 24, 2013 at 8:39 AM, David Miller <davem@...hat.com> wrote:
> From: Tom Herbert <therbert@...gle.com>
> Date: Tue, 24 Sep 2013 08:22:55 -0700
>
>> We use this value for steering, and could use it for other uses like
>> connection lookup.
>
> For security reasons we absolutely cannot use it for that purpose,
> please stop claiming this.
>
> Any hash function which an attacker can reproduce is attackable.

The Toeplitz function uses a secret key whose length is based on the
input length.  96 bits in IPv4, 320 bits in IPv6.  I don't see how an
attacker can reproduce this if the key is random.  If the problem is
that devices are not being configured with a sufficiently random key
(some actually are using a fixed key :-( ), that's a separate issue
that should be addressed.  It is possible to DoS attack through the
steering mechanism.

Tom
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