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

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Message-ID: <1380046245.2736.52.camel@bwh-desktop.uk.level5networks.com>
Date:	Tue, 24 Sep 2013 19:10:45 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...hat.com>
CC:	<therbert@...gle.com>, <David.Laight@...lab.com>,
	<netdev@...r.kernel.org>, <jesse.brandeburg@...el.com>
Subject: Re: [PATCH 1/2] net: Toeplitz library functions

On Tue, 2013-09-24 at 14:03 -0400, David Miller wrote:
> From: Tom Herbert <therbert@...gle.com>
> Date: Tue, 24 Sep 2013 08:54:24 -0700
> 
> > 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.
> 
> All of them are using a fixed, defined, key.

This is certainly false, as I know sfc randomises the key.  And the
Microsoft RSS spec appears to require that the key is programmable.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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