Encrypted Server Name Indication for TLS 1.3
draft-ietf-tls-esni-01
tls E. Rescorla
Internet-Draft RTFM, Inc.
Intended status: Experimental K. Oku
Expires: March 22, 2019 Fastly
N. Sullivan
Cloudflare
C. Wood
Apple, Inc.
September 18, 2018
Encrypted Server Name Indication for TLS 1.3
draft-ietf-tls-esni-01
Abstract
This document defines a simple mechanism for encrypting the Server
Name Indication for TLS 1.3.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 22, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Rescorla, et al. Expires March 22, 2019 [Page 1]
Internet-Draft TLS 1.3 SNI Encryption September 2018
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Topologies . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. SNI Encryption . . . . . . . . . . . . . . . . . . . . . 5
4. Publishing the SNI Encryption Key . . . . . . . . . . . . . . 5
5. The "encrypted_server_name" extension . . . . . . . . . . . . 8
5.1. Client Behavior . . . . . . . . . . . . . . . . . . . . . 8
5.2. Client-Facing Server Behavior . . . . . . . . . . . . . . 10
5.3. Shared Mode Server Behavior . . . . . . . . . . . . . . . 11
5.4. Split Mode Server Behavior . . . . . . . . . . . . . . . 11
6. Compatibility Issues . . . . . . . . . . . . . . . . . . . . 12
6.1. Misconfiguration . . . . . . . . . . . . . . . . . . . . 12
6.2. Middleboxes . . . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7.1. Why is cleartext DNS OK? . . . . . . . . . . . . . . . . 13
7.2. Comparison Against Criteria . . . . . . . . . . . . . . . 13
7.2.1. Mitigate against replay attacks . . . . . . . . . . . 13
7.2.2. Avoid widely-deployed shared secrets . . . . . . . . 13
7.2.3. Prevent SNI-based DoS attacks . . . . . . . . . . . . 14
7.2.4. Do not stick out . . . . . . . . . . . . . . . . . . 14
7.2.5. Forward secrecy . . . . . . . . . . . . . . . . . . . 14
7.2.6. Proper security context . . . . . . . . . . . . . . . 14
7.2.7. Split server spoofing . . . . . . . . . . . . . . . . 14
7.2.8. Supporting multiple protocols . . . . . . . . . . . . 14
7.3. Misrouting . . . . . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. Update of the TLS ExtensionType Registry . . . . . . . . 15
8.2. Update of the DNS Underscore Global Scoped Entry Registry 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Communicating SNI and Nonce to Backend Server . . . 17
Appendix B. Alternative SNI Protection Designs . . . . . . . . . 17
B.1. TLS-layer . . . . . . . . . . . . . . . . . . . . . . . . 17
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