Re: [TLS] Banning implicit CIDs in DTLS

Christopher Wood <caw@heapingbits.net> Fri, 29 May 2020 15:57 UTC

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Date: Fri, 29 May 2020 08:57:01 -0700
From: "Christopher Wood" <caw@heapingbits.net>
To: "Hannes Tschofenig" <Hannes.Tschofenig@arm.com>, "Richard Barnes" <rlb@ipv.sx>
Cc: "TLS@ietf.org" <TLS@ietf.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/LkQsO2LNngwdOrXQBC2gMck5gYg>
Subject: Re: [TLS] Banning implicit CIDs in DTLS
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Thanks, all! It looks like we have consensus on #148, so I merged it. Let's spin a new version with these changes and move forward.

Best,
Chris

On Fri, May 29, 2020, at 8:29 AM, Hannes Tschofenig wrote:
>  
> I also agree. Even without implicit CIDs we can still put multiple 
> handshake messages into a single record. Hence, there is no performance 
> problem. 
> 
> 
> *From:* TLS <tls-bounces@ietf.org> *On Behalf Of * Richard Barnes
> *Sent:* Thursday, May 28, 2020 3:37 PM
> *To:* Christopher Wood <caw@heapingbits.net>
> *Cc:* TLS@ietf.org
> *Subject:* Re: [TLS] Banning implicit CIDs in DTLS
> 
> 
> I agree with EKR that this seems like the most expedient solution to the issue.
> 
> 
> --Richard
> 
> 
> On Thu, May 21, 2020 at 12:00 PM Christopher Wood <caw@heapingbits.net> wrote:
> 
> > PR #148 in the DTLS 1.3 draft (https://github.com/tlswg/dtls13-spec/pull/148) proposes banning implicit CIDs. This comes at an obvious cost in terms of bytes on the wire. However, in discussions on a parallel thread [1 and related], it's noted that this removes header malleability. 
> > 
> >  Given that we don't have backing analysis suggesting that malleability (with the other AAD properties) is safe*, the chairs propose merging this PR as-is. To that end, please respond to the list by May 28, 2020, indicating whether or not you support this PR.
> > 
> >  Thanks,
> >  Chris, on behalf of the chairs
> > 
> >  *One proposal to address this is by extending the AAD to include the pseudo-header. However, the chairs feel this is an unnecessary divergence from QUIC.
> > 
> >  [1]  https://mailarchive.ietf.org/arch/msg/tls/kFnlBW-TmlArcU0lD9UQdf_1t_o/
> > 
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