Re: [TLS] Fwd: New Version Notification for draft-schwartz-tls-lb-00.txt

Stephen Farrell <stephen.farrell@cs.tcd.ie> Fri, 28 June 2019 17:34 UTC

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To: Ben Schwartz <bemasc=40google.com@dmarc.ietf.org>, "<tls@ietf.org>" <tls@ietf.org>
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From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Date: Fri, 28 Jun 2019 18:34:11 +0100
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Subject: Re: [TLS] Fwd: New Version Notification for draft-schwartz-tls-lb-00.txt
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Hi Ben,

Thanks for posting that - good to see a start on plugging
that gap.

On 28/06/2019 17:52, Ben Schwartz wrote:
> Hi TLS,
> 
> This is a proposal for a very simple new protocol whose main purpose is to
> enable ESNI "split mode".  Ultimately, I hope that this protocol can also
> enable more end-to-end TLS, by reducing the need for load-balancers to
> terminate TLS.

I guess an alternative would be to wrap this metadata and
the TLS session in another possibly long-lived TLS session
between the LB and backend. That'd have the benefit of not
requiring a PSK, making correlation of the CH etc from TLS
client to LB with the LB to backend non-trivial(*), but I
guess at the cost of more CPU and per-packet overhead.

The fact that a network observer can so easily correlate
the inbound TLS packets to the LB with those outbound seems
like a fairly major downside of this approach to me.

The PSK would also make it hard to offer ESNI fronting to
random backends without pre-arrangement between the LB and
backend, should that be something someone wanted to do. I
think that would allow less centralised deployment of ESNI,
which I think is a pretty desirable option to preserve.

Also: a diagram would really help make the draft easier to
grok:-)

Cheers,
S.

(*) When I say non-trivial here I don't mean "very hard":-)



> 
> Please discuss.
> 
> Thanks,
> Ben Schwartz
> 
> ---------- Forwarded message ---------
> 
> A new version of I-D, draft-schwartz-tls-lb-00.txt
> has been successfully submitted by Benjamin M. Schwartz and posted to the
> IETF repository.
> 
> Name:           draft-schwartz-tls-lb
> Revision:       00
> Title:          TLS Metadata for Load Balancers
> Document date:  2019-06-28
> Group:          Individual Submission
> Pages:          8
> URL:
> https://www.ietf.org/internet-drafts/draft-schwartz-tls-lb-00.txt
> Status:         https://datatracker.ietf.org/doc/draft-schwartz-tls-lb/
> Htmlized:       https://tools.ietf.org/html/draft-schwartz-tls-lb-00
> Htmlized:       https://datatracker.ietf.org/doc/html/draft-schwartz-tls-lb
> 
> 
> Abstract:
>    A load balancer that does not terminate TLS may wish to provide some
>    information to the backend server, in addition to forwarding TLS
>    data.  This draft proposes a protocol between load balancers and
>    backends that enables secure, efficient delivery of TLS with
>    additional information.  The need for such a protocol has recently
>    become apparent in the context of split mode ESNI.
> 
> 
> 
> 
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
> 
> The IETF Secretariat
> 
> 
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