Re: [TLS] Update spec to match current practices for certificate chain order

Viktor Dukhovni <ietf-dane@dukhovni.org> Tue, 12 May 2015 16:44 UTC

Return-Path: <ietf-dane@dukhovni.org>
X-Original-To: tls@ietfa.amsl.com
Delivered-To: tls@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 7C9011A8ACC for <tls@ietfa.amsl.com>; Tue, 12 May 2015 09:44:49 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9] autolearn=ham
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 kXrw7glft2Pz for <tls@ietfa.amsl.com>; Tue, 12 May 2015 09:44:48 -0700 (PDT)
Received: from mournblade.imrryr.org (mournblade.imrryr.org [38.117.134.19]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 15B0D1A898D for <tls@ietf.org>; Tue, 12 May 2015 09:44:48 -0700 (PDT)
Received: by mournblade.imrryr.org (Postfix, from userid 1034) id DF80B283031; Tue, 12 May 2015 16:44:46 +0000 (UTC)
Date: Tue, 12 May 2015 16:44:46 +0000
From: Viktor Dukhovni <ietf-dane@dukhovni.org>
To: tls@ietf.org
Message-ID: <20150512164446.GP17272@mournblade.imrryr.org>
References: <20150509032036.072AD1B2E2@ld9781.wdf.sap.corp> <a46388945a43eb199f843e505fcea6d9.squirrel@webmail.dreamhost.com> <20150512162405.GM17272@mournblade.imrryr.org> <CACsn0c=qR6YiL63EhSCwAg10erPoUPQ8XLJMczMMtgTjAWD9Ew@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CACsn0c=qR6YiL63EhSCwAg10erPoUPQ8XLJMczMMtgTjAWD9Ew@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Archived-At: <http://mailarchive.ietf.org/arch/msg/tls/ATxh9xUTo5BccBc9sfqcrEOTJJA>
Subject: Re: [TLS] Update spec to match current practices for certificate chain order
X-BeenThere: tls@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
Reply-To: tls@ietf.org
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: <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: Tue, 12 May 2015 16:44:49 -0000

On Tue, May 12, 2015 at 09:31:15AM -0700, Watson Ladd wrote:

> > FWIW, OpenSSL does no path discovery.  Whatever certificates the
> > server sends, there is a linearly ordered subset[1] of these that
> > achieves the same validation result as the original heap of certs
> > for all OpenSSL-based clients.  So sending something other than a
> > linearly ordered list has no value.
> >
> > With OpenSSL 1.0.2 recently tweaked to do trust-store look-asides
> > for nodes in the middle of the provided linear list, as also noted
> > by Martin cross-signing with SHA256 or RSA 2048, ... works just
> > fine.
> 
> So the actual requirement is for a linearization of the DAG of certs,
> and this will produce the same results as considering all chains in
> the DAG? Or am I misunderstanding you?

OpenSSL only constructs one candidate path through the supplied
heap (with lookaside into a trust store at each link).  Therefore,
with respect to OpenSSL clients, supplying anything that is not
the lexically first chain is a waste of bandwidth.

If that lexically first linear chain does not work (possibly
truncated if an intermediate element is signed by a local trust
anchor), validation fails.

-- 
	Viktor.