IETF Logo Mail Archive

Re: [TLS] cTLS transport question

Eric Rescorla <ekr@rtfm.com> Mon, 29 July 2019 12:10 UTC

Return-Path: <ekr@rtfm.com>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 5646212019C for <tls@ietfa.amsl.com>; Mon, 29 Jul 2019 05:10:39 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.897
X-Spam-Level:
X-Spam-Status: No, score=-1.897 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NONE=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=rtfm-com.20150623.gappssmtp.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1NXXDj6vearL for <tls@ietfa.amsl.com>; Mon, 29 Jul 2019 05:10:37 -0700 (PDT)
Received: from mail-lf1-x135.google.com (mail-lf1-x135.google.com [IPv6:2a00:1450:4864:20::135]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id C1EE71200F8 for <TLS@ietf.org>; Mon, 29 Jul 2019 05:10:36 -0700 (PDT)
Received: by mail-lf1-x135.google.com with SMTP id z15so37601973lfh.13 for <TLS@ietf.org>; Mon, 29 Jul 2019 05:10:36 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rtfm-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Ec6mgJZmBPTPgayy1M/t9zsdGaTtTjffJUEmWMTxnlg=; b=udcO1hQgb1APsb2lfhU83UX92ZNaV2chlNjxa7eYrPUVVYbD5ba5fDxmWZt725AlKC m1Pt0aGjz5CoQ+X/qvJptdv0E32ZSB5jVqClTwaOQVhE3BNlYrcOwd5pSKGLSkiKI8R5 0omDoT3hVw8xFpmQcdGwalaxaj5q0r3XJOHyEqIRSmYOOb5DVYx5YfaFQRh0xsjkdFOr JIFFfNBgiNmaoRzOYKjkuxstv8hUGBDbThiXT5P/27XZJh/wiGYfKHGgYwNjU349tFdK 8f4n+Q54Pn6uKHFnCD6t7XdIE/HAogEgnCBYDm0vA/RSqDQ6tmo+3KT9uDf7Y6z/ECfJ dNTQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Ec6mgJZmBPTPgayy1M/t9zsdGaTtTjffJUEmWMTxnlg=; b=ZkclpqnQuMD+HuVdpFdHlQZAnFFtU24WBsd5moSR6lBrbLF4+k3inTfaF7ne0lOLxR R92TNuWOxe42OMyYPdNwc7j/9oJP1A8WW8ZylYE87GXWaBjML63N89AgqElGBHZEdm/e vKf99aJlCnRaVp7b1a2jItTzw1J7KzPa49HyeNdojVJLcpDFtrjHAW4iUNfFJqW7FVC9 voMAkcryUdMkCADZG74uHGMOcOrHMiDECQ/bM+cKybhAOrUNOyMXOvt5tiwuIUf/My/U snWOqFaRdLSZnlZwjGK8RUvWT2+M1PaVGDl8Ovu644eqn9wsHbIXbhOIGmiBmrBze+US EL/w==
X-Gm-Message-State: APjAAAU2CO8Pp8n6WgoJDeVIY1eTA+ZWrHrU/LKUaOJnugk5O/rT1+Z3 vJbOi0E96oynSCT/BXe+K3q3S3+bsGSPJ5OPcuvzOQ==
X-Google-Smtp-Source: APXvYqylEV3AfUb6xLxngRbNx/YP/8UJY8vfOsC/KR8uWYHLwQ99TR2Iw/0D66YxEGXX/NvfB62LOYeP9SAl7fhcyAQ=
X-Received: by 2002:ac2:528e:: with SMTP id q14mr6637797lfm.17.1564402235015; Mon, 29 Jul 2019 05:10:35 -0700 (PDT)
MIME-Version: 1.0
References: <1772330A-AEE4-4510-A261-F2D5AF9762DD@arm.com>
In-Reply-To: <1772330A-AEE4-4510-A261-F2D5AF9762DD@arm.com>
From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 29 Jul 2019 05:09:43 -0700
Message-ID: <CABcZeBMgXQXD-PCsspaKCpoTWTbs+Jtp=V95fCGQzEgvBiZuWg@mail.gmail.com>
To: Thomas Fossati <Thomas.Fossati@arm.com>
Cc: "TLS@ietf.org" <TLS@ietf.org>
Content-Type: multipart/alternative; boundary="0000000000008114f1058ed0c756"
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/utZP8ClZLiiOO6cyH76gzoPMbCY>
Subject: Re: [TLS] cTLS transport question
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <tls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/tls/>
List-Post: <mailto:tls@ietf.org>
List-Help: <mailto:tls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/tls>, <mailto:tls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 29 Jul 2019 12:10:39 -0000

On Thu, Jul 25, 2019 at 9:04 AM Thomas Fossati <Thomas.Fossati@arm.com>
wrote:

> Thanks for presenting this work.  I really like this and I think
>
> it'd be really useful for the use cases we have (IoT, M2M).
>
>
>
> One comment: from a quick skimming of the draft, I'm not sure I
>
> understand what the stated expectations on the transport layer are?
>
>
>
> Since it's cTLS and not cDTLS I'd have thought it's the same as TLS
>
> (in-order & reliable) but then I got confused reading section 3.2 [1]:
>
>
>
>   "The CTLS Record Layer assumes that records are externally framed
>
>    (i.e., that the length is already known because it is carried in
>
>    a UDP datagram or the like)"
>
>
>
> On Jabber Ben suggested that one could put CoAP between UDP and cTLS to
>
> get in-order & reliable delivery with a datagram transport, but then I'm
>
> not sure what the advantage would be since we'd be trading 2 bytes of
>
> TLSPlaintext.length with 4 bytes (minimum) of CoAP header?
>

The idea here was that you might be in a situation where you had external
framing
anyway. I'm sure we can figure out some way to make that optional.

-Ekr



>
> From the Jabber discussion, my current understanding is that there are 2
>
> assumptions: a) the transport is in-order & reliable, and 2) there is
>
> one TLS record per transport layer packet.
>
>
>
> Is that the correct interpretation?  If it is, is it not too restrictive
>
> a requirement?
>



>
>
> Cheers, thanks
>
>
>
> [1] https://tools.ietf.org/html/draft-rescorla-tls-ctls-02#section-3.2
>
>
>
>
> IMPORTANT NOTICE: The contents of this email and any attachments are
> confidential and may also be privileged. If you are not the intended
> recipient, please notify the sender immediately and do not disclose the
> contents to any other person, use it for any purpose, or store or copy the
> information in any medium. Thank you.
> _______________________________________________
> TLS mailing list
> TLS@ietf.org
> https://www.ietf.org/mailman/listinfo/tls
>

v2.23.0 | Report a Bug | By Email