The "SNI" Alt-Svc Parameter
draft-bishop-httpbis-sni-altsvc-02

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HTTPbis                                                        M. Bishop
Internet-Draft                                                    Akamai
Intended status: Standards Track                            May 24, 2018
Expires: November 25, 2018

                      The "SNI" Alt-Svc Parameter
                   draft-bishop-httpbis-sni-altsvc-02

Abstract

   HTTP Alternative Services provides a mechanism for an origin to
   declare that its content is accessible via some other combination of
   host, port, and protocol.  In the process of using such an
   alternative, an observer can identify that the client is requesting
   resources from a particular hostname.

   This document extends HTTP Alternative Services, in combination with
   Secondary Certificate Authentication, to enable clients not to
   disclose the origin to which they intend to connect.

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 November 25, 2018.

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

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   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
     1.1.  Usage . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  The "sni" Alt-Svc Extension . . . . . . . . . . . . . . . . .   3
   3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  SNI of Colocated Domain . . . . . . . . . . . . . . . . .   4
     3.2.  Wildcard Subdomains . . . . . . . . . . . . . . . . . . .   5
     3.3.  Omitting SNI  . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  SNI of Unrelated Domain . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
     6.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Confidentiality and authentication during communication are primary
   goals of using TLS to secure traffic on the Internet.  However, due
   to the nature of TLS, certain information is inherently not
   confidential - notably, the hostname and the corresponding
   certificate of the origin to which the client is connecting are
   transferred unencrypted in the Server Name Indication extension [SNI]
   and the server's Certificate message [TLS12].

   While the client identity can be obscured by using TLS renegotiation
   immediately after the handshake (in TLS 1.2) or by using TLS 1.3
   [TLS13], the server is not afforded such privacy considerations.

   Servers may also have wildcard certificates which do not enumerate
   specific subdomains, but clients will disclose the first subdomain
   used on a connection via the SNI extension when establishing the
   connection.

   [SNIEncryption] discusses a potential solution to these issues in
   Section 3, HTTP Co-Tenancy Fronting, but notes both discoverability
   and server authentication issues with that approach.  This document
   provides a mechanism to address both limitations.

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