Re: [TLS] Working Group Last Call for draft-ietf-tls-tls13-18

Ilari Liusvaara <> Fri, 28 October 2016 16:24 UTC

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Date: Fri, 28 Oct 2016 19:24:26 +0300
From: Ilari Liusvaara <>
To: Martin Rex <>
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-tls13-18
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On Fri, Oct 28, 2016 at 06:00:03PM +0200, Martin Rex wrote:
> Joseph Salowey wrote:
> There are two seriously backwards-incompatible changes in the
> current proposal that provide zero value, but completely break
> backwards-compatibility with existing middleware infrastructure.
> (1) hiding of the TLS record content types.
>     Please leave the TLS record types (handshake/AppData/Alert/CCS)
>     clearly visible on the outside of the TLS records, so that
>     middleware protocol parsers (which interface to transport-free
>     TLS protocol stacks) can continue to work, and continue to
>     work efficiently.

Hiding the types does have its benefits (and it is also used for
zero-overhead padding scheme).

And also, TLS 1.3 handshake is so darn different from TLS 1.2, that
you couldn't do anything sane even if you had record types.
> (2) hiding of the TLS extension SNI.
>     Right now it is perferctly fine to implement TLS extensions SNI
>     on the server completely outside the TLS protocol stack to route
>     to single-cert SNI-unaware backends.  The current proposal
>     suggest to move TLS extension SNI into the encrypted part, if
>     my superficial reading of the draft is correct, so TLSv1.3
>     will not fly with existing architectures where spreading of
>     TLS requests on the server-side based on TLS extension SNI
>     is done outside of the TLS protocol stack (i.e. bottleneck-less
>     without having to open TLS).

Who actually cares about server-side SNI? And it wasn't like you
could do anything useful with server-side SNI in TLS 1.2 either.

You can still route connections on SNI, and it even works the
same way it did in TLS 1.2 (so existing code works).