Re: [keyassure] CN/SAN matching (was: End entity certificate matching, trust anchors, and protocol-06)

Paul Wouters <paul@xelerance.com> Mon, 21 March 2011 19:45 UTC

Return-Path: <paul@xelerance.com>
X-Original-To: keyassure@core3.amsl.com
Delivered-To: keyassure@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 2EFD828C0DD for <keyassure@core3.amsl.com>; Mon, 21 Mar 2011 12:45:00 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.59
X-Spam-Level:
X-Spam-Status: No, score=-2.59 tagged_above=-999 required=5 tests=[AWL=0.009, BAYES_00=-2.599]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jp0JHtz58EZO for <keyassure@core3.amsl.com>; Mon, 21 Mar 2011 12:44:59 -0700 (PDT)
Received: from newtla.xelerance.com (newtla.xelerance.com [193.110.157.143]) by core3.amsl.com (Postfix) with ESMTP id 93E0628C0D7 for <keyassure@ietf.org>; Mon, 21 Mar 2011 12:44:58 -0700 (PDT)
Received: from tla.xelerance.com (tla.xelerance.com [193.110.157.130]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by newtla.xelerance.com (Postfix) with ESMTP id 6FB9FC57F; Mon, 21 Mar 2011 15:46:29 -0400 (EDT)
Date: Mon, 21 Mar 2011 15:46:28 -0400 (EDT)
From: Paul Wouters <paul@xelerance.com>
To: Paul Hoffman <paul.hoffman@vpnc.org>
In-Reply-To: <4BC9E139-CBC5-46EE-A18F-E8F16AE108D6@vpnc.org>
Message-ID: <alpine.LFD.1.10.1103211544060.20162@newtla.xelerance.com>
References: <4D7BFB41.4000403@vpnc.org> <20110321092514.GE9247@anguilla.noreply.org> <AFFDB7BB-8749-4638-AB2D-9ACB617204AC@kirei.se> <20110321130430.GG9247@anguilla.noreply.org> <4BC9E139-CBC5-46EE-A18F-E8F16AE108D6@vpnc.org>
User-Agent: Alpine 1.10 (LFD 962 2008-03-14)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
Cc: Peter Palfrader <peter@palfrader.org>, keyassure@ietf.org
Subject: Re: [keyassure] CN/SAN matching (was: End entity certificate matching, trust anchors, and protocol-06)
X-BeenThere: keyassure@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Key Assurance With DNSSEC <keyassure.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/keyassure>, <mailto:keyassure-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/keyassure>
List-Post: <mailto:keyassure@ietf.org>
List-Help: <mailto:keyassure-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/keyassure>, <mailto:keyassure-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 21 Mar 2011 19:45:00 -0000

On Mon, 21 Mar 2011, Paul Hoffman wrote:

>> Why is it needed in the first place?
>
>
> That's a very good question. I don't feel that it is a "need", but it "makes some sense". That is, if I want to go to www.example.com, and I get an A record for www.example.com, and I get a TLSA record for _http._tcp.www.example.com, and I get a certificate that says "this key is associated with www.somethingelse.com"quot;, what does it mean?
>
> I can see both ways: "it doesn't matter what the cert says, we are trusting the binding from the DNS" vs. "the cert needs to mean something"? Jakob and I have that text in because a number of people on the list were in the latter category, but it seems like a reasonable question to ask separately.

This is exactly why bare public keys are good for those who do not wish to deal with
a CA or making up arbitrary CN= entries in certificates only used to contain a public
key verified by DNS.

In fact, if forced to use a cert container, I would use a self signed *.xelerance.com,
but I definitely not add a *.xelerance.com wildcard in DNS.

Demanding information that will be filled in with bogus or unvalidatable information
makes no sense from a security point of view.

Paul