Re: [TLS] Publication of draft-rhrd-tls-tls13-visibility-00

"David A. Cooper" <> Tue, 24 October 2017 22:39 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id E9DA513F876 for <>; Tue, 24 Oct 2017 15:39:19 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -3.477
X-Spam-Status: No, score=-3.477 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HTML_MESSAGE=0.001, MIME_HTML_ONLY=0.723, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id gK_0KuuIsJjr for <>; Tue, 24 Oct 2017 15:39:17 -0700 (PDT)
Received: from ( [IPv6:2610:20:6005:13::151]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 79989138BD2 for <>; Tue, 24 Oct 2017 15:39:17 -0700 (PDT)
Received: from ( by ( with Microsoft SMTP Server (TLS) id 14.3.361.1; Tue, 24 Oct 2017 18:39:09 -0400
Received: from ( by ( with Microsoft SMTP Server id 14.3.361.1; Tue, 24 Oct 2017 18:39:13 -0400
Received: from [] ( []) by (8.13.8/8.13.1) with ESMTP id v9OMcwMD028663 for <>; Tue, 24 Oct 2017 18:38:58 -0400
To: "" <>
References: <> <> <> <> <> <> <> <>
From: "David A. Cooper" <>
Message-ID: <>
Date: Tue, 24 Oct 2017 18:39:05 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/html; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Archived-At: <>
Subject: Re: [TLS] Publication of draft-rhrd-tls-tls13-visibility-00
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 24 Oct 2017 22:39:20 -0000

On 10/24/2017 05:18 PM, Salz, Rich wrote:


  • And, I don't buy the idea that if this extension is standardized that it will be implemented in commonly-used browsers.


And that is a risk you are willing for the entire public Internet to take?

I'm not taking any risk.  The ability for a server to allow a third party to have access to data it is exchanging with a client already exists, and that ability isn't going away whether this proposal (or something similar) is standardized or not. As I've already pointed out, for the scenarios people are concerned about, the "attacks" being described would be much more easily carried out by some means other than draft-rhrd-tls-tls13-visibility.

So, no I am not worried about the "risk" of creating a complicated way for servers and middleboxes to collude to do something that they can already do now in a simpler way.

And what about the fact that it provides a cleartext signal as to whether or not a client is willing to let itself be MiTM’d, does that bother you?

No. As I noted before, servers can already allow middleboxes to MiTM connections with clients with asking the client's permission. Public facing servers that want to allow this (even if as a result of coercion) won't use this extension. They'll just enable it without informing the clients.

There are also other ways a server could allow a middlebox to MiTM the connections that it has with clients that don't require the client's cooperation (or knowledge) and that wouldn't require any changes on the client side; ways that would be easier than trying to use draft-rhrd-tls-tls13-visibility.

If the only way (or the easiest way) these connections could be MiTM'd required getting clients' permission, then this might be a concern, I don't see servers that want to (or are coerced into) allowing connections to be MiTM'd asking clients whether they are willing. Given this, we aren't going to see browsers that are configurable to signal that the client is willing to "allow" the connection to be MiTM'd.

I haven't even gotten into the question of what does it mean for a connection to be MiTM'd. If Company X decides to have its web site operated by Hosting Provider Y is the connection between the client and Company X being MiTM'd? The client might think it has a secure end-to-end connection with Company X, but in reality its data is being intercepted and read by Hosting Provider Y, without the client's permission (and most likely without the client's knowledge). How does TLS, currently, prevent this? Why isn't anyone demanding that TLS cannot be standardized until it can be proven that such a scenario is impossible?