Issues and Requirements for SNI Encryption in TLS
draft-ietf-tls-sni-encryption-09

Document Type Active Internet-Draft (tls WG)
Last updated 2019-10-28
Replaces draft-huitema-tls-sni-encryption
Stream IETF
Intended RFC status Informational
Formats plain text xml pdf htmlized bibtex
Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Joseph Salowey
Shepherd write-up Show (last changed 2019-01-22)
IESG IESG state RFC Ed Queue
Consensus Boilerplate Yes
Telechat date
Responsible AD Benjamin Kaduk
Send notices to Sean Turner <sean@sn3rd.com>, Joseph Salowey <joe@salowey.net>
IANA IANA review state IANA OK - No Actions Needed
IANA action state No IANA Actions
RFC Editor RFC Editor state EDIT
Network Working Group                                         C. Huitema
Internet-Draft                                      Private Octopus Inc.
Intended status: Informational                               E. Rescorla
Expires: April 30, 2020                                       RTFM, Inc.
                                                        October 28, 2019

           Issues and Requirements for SNI Encryption in TLS
                    draft-ietf-tls-sni-encryption-09

Abstract

   This draft describes the general problem of encrypting the Server
   Name Identification (SNI) TLS parameter.  The proposed solutions hide
   a Hidden Service behind a fronting service, only disclosing the SNI
   of the fronting service to external observers.  The draft lists known
   attacks against SNI encryption, discusses the current "co-tenancy
   fronting" solution, and presents requirements for future TLS layer
   solutions.

   In practice, it may well be that no solution can meet every
   requirement, and that practical solutions will have to make some
   compromises.

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 April 30, 2020.

Copyright Notice

   Copyright (c) 2019 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

Huitema & Rescorla       Expires April 30, 2020                 [Page 1]
Internet-Draft       TLS-SNI Encryption Requirements        October 2019

   (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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  History of the TLS SNI extension  . . . . . . . . . . . . . .   3
     2.1.  Unanticipated usage of SNI information  . . . . . . . . .   4
     2.2.  SNI encryption timeliness . . . . . . . . . . . . . . . .   4
     2.3.  End-to-end alternatives . . . . . . . . . . . . . . . . .   5
   3.  Security and Privacy Requirements for SNI Encryption  . . . .   5
     3.1.  Mitigate Replay Attacks . . . . . . . . . . . . . . . . .   6
     3.2.  Avoid Widely Shared Secrets . . . . . . . . . . . . . . .   6
     3.3.  Prevent SNI-based Denial of Service Attacks . . . . . . .   6
     3.4.  Do not stick out  . . . . . . . . . . . . . . . . . . . .   7
     3.5.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Multi-Party Security Contexts . . . . . . . . . . . . . .   7
     3.7.  Supporting multiple protocols . . . . . . . . . . . . . .   8
       3.7.1.  Hiding the Application Layer Protocol Negotiation . .   8
       3.7.2.  Support other transports than TCP . . . . . . . . . .   9
   4.  HTTP Co-Tenancy Fronting  . . . . . . . . . . . . . . . . . .   9
     4.1.  HTTPS Tunnels . . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  Delegation Control  . . . . . . . . . . . . . . . . . . .  10
     4.3.  Related work  . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Historically, adversaries have been able to monitor the use of web
   services through three primary channels: looking at DNS requests,
   looking at IP addresses in packet headers, and looking at the data
   stream between user and services.  These channels are getting
   progressively closed.  A growing fraction of Internet communication
   is encrypted, mostly using Transport Layer Security (TLS) [RFC5246].
   Progressive deployment of solutions like DNS in TLS [RFC7858] and DNS
   over HTTPS [RFC8484] mitigates the disclosure of DNS information.
Show full document text