Re: [TLS] Update on TLS 1.3 Middlebox Issues

mrex@sap.com (Martin Rex) Mon, 09 October 2017 17:21 UTC

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To: Ilari Liusvaara <ilariliusvaara@welho.com>
Date: Mon, 9 Oct 2017 19:21:01 +0200 (CEST)
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From: mrex@sap.com (Martin Rex)
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Subject: Re: [TLS] Update on TLS 1.3 Middlebox Issues
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Ilari Liusvaara <ilariliusvaara@welho.com>; wrote:
>
> And even if the changes might not be directly consequential to
> security, the changes to get through some more annoying middleboxes
> might be quite annoying to implement.
> 
> E.g. there probably are several different middeboxes that have a
> configuration that actually checks that the handshake looks valid,
> which includes checks for things like ChangeCipherSpec being
> present in both directions, even for resumption; while the non-
> resumption mode might even verify the authentication signatures in
> the handshake and not letting server send non-handshake messages
> before sending its 2nd flight. Ugh, getting around those would be
> pretty nasty.


Fixing the backwards-incompatibilities in the TLS record layer
would be terribly useful for streaming-optimized IO layers as well,
i.e. ensure the the TLS record properly identifies ContentType,
and that a TLSv1.3 handshake ends with CCS followed by 1 Handshake message.

-Martin