Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert

Martin Rex <mrex@sap.com> Fri, 04 June 2010 16:47 UTC

Return-Path: <mrex@sap.com>
X-Original-To: tls@core3.amsl.com
Delivered-To: tls@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id 6B0F13A67AD for <tls@core3.amsl.com>; Fri, 4 Jun 2010 09:47:31 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -7.656
X-Spam-Level:
X-Spam-Status: No, score=-7.656 tagged_above=-999 required=5 tests=[AWL=0.179, BAYES_40=-0.185, HELO_EQ_DE=0.35, RCVD_IN_DNSWL_HI=-8]
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 O+8n9mrj0BvR for <tls@core3.amsl.com>; Fri, 4 Jun 2010 09:47:30 -0700 (PDT)
Received: from smtpde02.sap-ag.de (smtpde02.sap-ag.de [155.56.68.140]) by core3.amsl.com (Postfix) with ESMTP id CB2553A659B for <tls@ietf.org>; Fri, 4 Jun 2010 09:47:29 -0700 (PDT)
Received: from mail.sap.corp by smtpde02.sap-ag.de (26) with ESMTP id o54Gl5PC015614 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 4 Jun 2010 18:47:05 +0200 (MEST)
From: Martin Rex <mrex@sap.com>
Message-Id: <201006041647.o54Gl4iH024692@fs4113.wdf.sap.corp>
To: mike-list@pobox.com (Michael D'Errico)
Date: Fri, 4 Jun 2010 18:47:04 +0200 (MEST)
In-Reply-To: <4C092737.2060604@pobox.com> from "Michael D'Errico" at Jun 4, 10 09:17:59 am
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Scanner: Virus Scanner virwal08
X-SAP: out
Cc: tls@ietf.org
Subject: Re: [TLS] RFC-4366-bis and the unrecognized_name(112) alert
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
Reply-To: mrex@sap.com
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/listinfo/tls>, <mailto:tls-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/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: Fri, 04 Jun 2010 16:47:31 -0000

Michael D'Errico wrote:
> 
> I would like to see text that says a peer SHOULD ignore warning alerts
> that it doesn't otherwise handle.  Clearly the peer that sent the alert
> with a warning level doesn't think it's a showstopper -- if it was a
> problem, the alert level would have been fatal.
> 
> Peers that escalate a warning to fatal are not playing nice; they are
> causing other software to abandon the practice of sending warnings even
> though they could prove useful.  Just because you can't imagine why a
> warning alert would be useful, today, doesn't mean that a use will never
> be found for it.

I think we are talking past each other.

I do not have any problems with the existence of warning level alerts.

But defining only the situation when one peer can send a particular
warning level alert is entirely insufficient.  The definition of
a warning-level alert _MUST_ describe how the receiving peer is
supposed to react to this.  In most cases, a warning-level alert
indicates that something unusal happend on the last protocol
exchange, and there is no means _within_ the TLS handshake to resend
a previous handshake message with different properties -- which means
that we will may have to specify application/API semantics. 

For the warning-level unrecognized_name alert, I believe we have to specify
application/API semantics for the receiver.

-Martin