TLS Resumption across Server Name Indications for TLS 1.3
draft-sy-tls-resumption-group-00

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tls                                                                E. Sy
Internet-Draft                                     University of Hamburg
Intended status: Experimental                             March 01, 2019
Expires: September 2, 2019

       TLS Resumption across Server Name Indications for TLS 1.3
                    draft-sy-tls-resumption-group-00

Abstract

   This document defines a mechanism for resuming a TLS 1.3 session
   across different Server Name Indications.

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
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   This Internet-Draft will expire on September 2, 2019.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Sy                      Expires September 2, 2019               [Page 1]
Internet-Draft          TLS 1.3 Resumption Group              March 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Overview on Resumptions across SNI values . . . . . . . . . .   3
   4.  The "resumption_group" Extension  . . . . . . . . . . . . . .   3
     4.1.  Client Behavior . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Server Behavior . . . . . . . . . . . . . . . . . . . . .   4
   5.  Expectations on Certificates  . . . . . . . . . . . . . . . .   5
   6.  Compatibility Issues with Middleboxes . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Most web transactions are short transfers that are significantly
   delayed by the TLS connection establishment.  To accelerate the
   connection establishment, TLS 1.3 [RFC8446] and its predecessors
   provide session resumption mechanisms.  They abbreviate the TLS
   handshake based on a shared secret exchanged during a prior TLS
   session between client and server.  In total, these resumption
   handshakes significantly reduce computational overhead for
   cryptographic operations and save up to one round-trip compared to
   the full TLS connection establishment.

   TLS 1.3 [RFC8446] allows resumption handshakes across Server Name
   Indications (SNIs) when they share the same TLS certificate.
   However, TLS 1.3 recommends not to use TLS resumptions across SNIs to
   avoid loosing a single-use ticket in case of a failed resumption
   attempt.  This practice requires costly full TLS connection
   establishments in situations where a performance-optimized resumption
   handshake across SNI values would be possible.  To illustrate this
   performance limitation, we describe the common situation of a
   redirected web request.  We assume that the hostname example.com
   redirects to www.example.com and both hostnames are operated by the
   same entity and use the same certificate for their authentication.  A
   client requesting www.example.com via this redirect requires two full
   TLS handshakes following the recommendation of TLS 1.3 [RFC8446].
   Using resumption across SNI values, the later full handshake can be
   converted to a performance-optimized resumed handshake.  A
   comprehensive study of the performance benefits of resumptions across
   SNI values for popular websites can be found in [PERF].

Sy                      Expires September 2, 2019               [Page 2]
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