[TLS] SNI as authorization token?

Benjamin Kaduk <bkaduk@akamai.com> Tue, 04 May 2021 23:20 UTC

Return-Path: <bkaduk@akamai.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 777543A1993 for <tls@ietfa.amsl.com>; Tue, 4 May 2021 16:20:25 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.8
X-Spam-Level:
X-Spam-Status: No, score=-2.8 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=akamai.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 8wWp41R2jXlG for <tls@ietfa.amsl.com>; Tue, 4 May 2021 16:20:21 -0700 (PDT)
Received: from mx0b-00190b01.pphosted.com (mx0b-00190b01.pphosted.com [IPv6:2620:100:9005:57f::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 04B103A1990 for <tls@ietf.org>; Tue, 4 May 2021 16:20:20 -0700 (PDT)
Received: from pps.filterd (m0122331.ppops.net [127.0.0.1]) by mx0b-00190b01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 144NJHkf006549 for <tls@ietf.org>; Wed, 5 May 2021 00:20:19 +0100
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=akamai.com; h=date : from : to : subject : message-id : mime-version : content-type; s=jan2016.eng; bh=JFIXhqjqjwhYvLssIGg4lGdULqUOsnokFfd03NQ2CJk=; b=hVy55aFI2nk5+MNKNo2OpAcV0dYAul6T24x4kWFe9EedQA6JUKYXAODUxkOVarpqFOV9 83T9JPPZxiUg7K1/+QmtiJ8HE6+Cj+7Hn2ACYi3U36zG0dZ0Ch1xNOXV0q968fjWlgKs RyuULDb617vHnZGewMXTA5Brcc7KhF67pyR+ZeEEpulWFzlbHUFw+tgvEkkgEA1qW7hn PZ4RTNbN4I9y/BPphGRy56FQAubBu4fiNurae6NX4pJLyWp9qtCSRU2mpAgLg/pB8TKe sPY9gCuvphlU3HfsCL05Q4GB/i1VWY+JuohrGwKTswjmVM1IgHFdg6eOtrh2tagFqrrc eg==
Received: from prod-mail-ppoint7 (a72-247-45-33.deploy.static.akamaitechnologies.com [72.247.45.33] (may be forged)) by mx0b-00190b01.pphosted.com with ESMTP id 38bec3anka-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for <tls@ietf.org>; Wed, 05 May 2021 00:20:19 +0100
Received: from pps.filterd (prod-mail-ppoint7.akamai.com [127.0.0.1]) by prod-mail-ppoint7.akamai.com (8.16.1.2/8.16.1.2) with SMTP id 144N4Yu9013732 for <tls@ietf.org>; Tue, 4 May 2021 19:20:18 -0400
Received: from prod-mail-relay19.dfw02.corp.akamai.com ([172.27.165.173]) by prod-mail-ppoint7.akamai.com with ESMTP id 38bebh0kny-1 for <tls@ietf.org>; Tue, 04 May 2021 19:20:18 -0400
Received: from akamai.com (sea-lp9yo.bos01.corp.akamai.com [172.19.16.134]) by prod-mail-relay19.dfw02.corp.akamai.com (Postfix) with ESMTP id C8DED6063D for <tls@ietf.org>; Tue, 4 May 2021 23:20:17 +0000 (GMT)
Date: Tue, 4 May 2021 16:20:16 -0700
From: Benjamin Kaduk <bkaduk@akamai.com>
To: tls@ietf.org
Message-ID: <20210504232015.GO25665@akamai.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.9.4 (2018-02-28)
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-04_15:2021-05-04, 2021-05-04 signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=1 suspectscore=0 spamscore=1 mlxlogscore=190 phishscore=0 adultscore=0 bulkscore=0 mlxscore=1 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2105040157
X-Proofpoint-GUID: r7S-CoCWbR5R57rB3pE6bXCqW7aW8BST
X-Proofpoint-ORIG-GUID: r7S-CoCWbR5R57rB3pE6bXCqW7aW8BST
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.761 definitions=2021-05-04_15:2021-05-04, 2021-05-04 signatures=0
X-Proofpoint-Spam-Details: rule=notspam policy=default score=8 impostorscore=0 mlxscore=8 mlxlogscore=105 malwarescore=0 phishscore=0 suspectscore=0 lowpriorityscore=0 spamscore=8 priorityscore=1501 bulkscore=0 clxscore=1011 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2105040159
X-Agari-Authentication-Results: mx.akamai.com; spf=${SPFResult} (sender IP is 72.247.45.33) smtp.mailfrom=bkaduk@akamai.com smtp.helo=prod-mail-ppoint7
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/ZIPo1mF_wnOXkgS7Uv_wzIBFmR8>
Subject: [TLS] SNI as authorization token?
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: Tue, 04 May 2021 23:20:25 -0000

Hi all,

I'm reviewing draft-ietf-dprive-xfr-over-tls for this week's IESG telechat, and
in https://datatracker.ietf.org/doc/html/draft-ietf-dprive-xfr-over-tls-11#appendix-A.3
it seems to suggest that a TLS server might only choose to allow connections that
include a specific (secret-ish) SNI value.  Given that the "as above" listed "con"
seems to indicate that there are no relevant implementations of this functionality,
I plan to push back on its inclusion in the document; a PSK mode (with cert,
per RFC 8773) would seem to be universally superior.

Am I correct to do so?  Do we know of any cases where the SNI value is being
(ab)used as an authorization token in this manner?

Thanks,

Ben