Re: [TLS] lasgt call comments (st Call: draft-altman-tls-channel-bindings (Channel Bindings for TLS) to Proposed Standard)

Nicolas Williams <Nicolas.Williams@sun.com> Wed, 04 November 2009 20:03 UTC

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Date: Wed, 4 Nov 2009 13:52:08 -0600
From: Nicolas Williams <Nicolas.Williams@sun.com>
To: Simon Josefsson <simon@josefsson.org>
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Cc: channel-binding@ietf.org, tls@ietf.org, sasl@ietf.org
Subject: Re: [TLS] lasgt call comments (st Call: draft-altman-tls-channel-bindings (Channel Bindings for TLS) to Proposed Standard)
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On Wed, Nov 04, 2009 at 08:26:30PM +0100, Simon Josefsson wrote:
> Nicolas Williams <Nicolas.Williams@sun.com>; writes:
> > [...]
> 
> With that definition, one couldn't use tls-unique channel binding to
> bind to the authentication credentials associated with a TLS channel
              ^^^^^^^^^^^^^^^^^^^^^^^^^^
> uniquely -- a TLS re-negotiation doesn't change the channel binding
> data, but it may change the authentication credentials.

The point of channel binding is NOT to bind the authentication
credentials of the channel's end-points.  In fact, the point of channel
binding is to allow authentication to happen at a layer above the
channel, so that the authentication, or lack thereof in that channel,
becomes irrelevant.

Please see RFC5056.

> I believe that problem needs to be explained in the security
> consideration -- it would be easy to think that channel binding data can
> be used to get a cryptographic association with the user credentials
> used for that channel.

There is no problem.

> Otherwise I don't see any problem with this definition.

Thanks.

Nico
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