Encrypted Server Name Indication for TLS 1.3
draft-ietf-tls-esni-02

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tls                                                          E. Rescorla
Internet-Draft                                                RTFM, Inc.
Intended status: Experimental                                     K. Oku
Expires: April 25, 2019                                           Fastly
                                                             N. Sullivan
                                                              Cloudflare
                                                                 C. Wood
                                                             Apple, Inc.
                                                        October 22, 2018

              Encrypted Server Name Indication for TLS 1.3
                         draft-ietf-tls-esni-02

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 http://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 April 25, 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
   (http://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 April 25, 2019                 [Page 1]
Internet-Draft           TLS 1.3 SNI Encryption             October 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 . . . . . . . . . . . . . . . . . . . . .   9
     5.2.  Client-Facing Server Behavior . . . . . . . . . . . . . .  11
     5.3.  Shared Mode Server Behavior . . . . . . . . . . . . . . .  12
     5.4.  Split Mode Server Behavior  . . . . . . . . . . . . . . .  12
   6.  Compatibility Issues  . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Misconfiguration  . . . . . . . . . . . . . . . . . . . .  12
     6.2.  Middleboxes . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
     7.1.  Why is cleartext DNS OK?  . . . . . . . . . . . . . . . .  13
     7.2.  Comparison Against Criteria . . . . . . . . . . . . . . .  14
       7.2.1.  Mitigate against replay attacks . . . . . . . . . . .  14
       7.2.2.  Avoid widely-deployed shared secrets  . . . . . . . .  14
       7.2.3.  Prevent SNI-based DoS attacks . . . . . . . . . . . .  14
       7.2.4.  Do not stick out  . . . . . . . . . . . . . . . . . .  14
       7.2.5.  Forward secrecy . . . . . . . . . . . . . . . . . . .  15
       7.2.6.  Proper security context . . . . . . . . . . . . . . .  15
       7.2.7.  Split server spoofing . . . . . . . . . . . . . . . .  15
       7.2.8.  Supporting multiple protocols . . . . . . . . . . . .  15
     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  16
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  17
     A.1.  Since draft-ietf-tls-esni-01  . . . . . . . . . . . . . .  18
     A.2.  Since draft-ietf-tls-esni-00  . . . . . . . . . . . . . .  18