Opportunistic Security for HTTP/2
RFC 8164

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Internet Engineering Task Force (IETF)                     M. Nottingham
Request for Comments: 8164
Category: Experimental                                        M. Thomson
ISSN: 2070-1721                                                  Mozilla
                                                                May 2017

                   Opportunistic Security for HTTP/2

Abstract

   This document describes how "http" URIs can be accessed using
   Transport Layer Security (TLS) and HTTP/2 to mitigate pervasive
   monitoring attacks.  This mechanism not a replacement for "https"
   URIs; it is vulnerable to active attacks.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8164.

Copyright Notice

   Copyright (c) 2017 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Nottingham & Thomson          Experimental                      [Page 1]
RFC 8164              Opportunistic HTTP/2 Security             May 2017

Table of Contents

   1. Introduction ....................................................2
      1.1. Goals and Non-goals ........................................3
      1.2. Notational Conventions .....................................3
   2. Using HTTP URIs over TLS ........................................3
      2.1. Alternative Server Opt-In ..................................4
      2.2. Interaction with "https" URIs ..............................5
      2.3. The "http-opportunistic" Well-Known URI ....................5
   3. IANA Considerations .............................................6
   4. Security Considerations .........................................7
      4.1. Security Indicators ........................................7
      4.2. Downgrade Attacks ..........................................7
      4.3. Privacy Considerations .....................................7
      4.4. Confusion regarding Request Scheme .........................7
      4.5. Server Controls ............................................8
   5. References ......................................................8
      5.1. Normative References .......................................8
      5.2. Informative References .....................................9
   Acknowledgements ...................................................9
   Authors' Addresses ................................................10

1.  Introduction

   This document describes a use of HTTP Alternative Services [RFC7838]
   to decouple the URI scheme from the use and configuration of
   underlying encryption.  It allows an "http" URI [RFC7230] to be
   accessed using HTTP/2 and Transport Layer Security (TLS) [RFC5246]
   with Opportunistic Security [RFC7435].

   This document describes a usage model whereby sites can serve "http"
   URIs over TLS, thereby avoiding the problem of serving Mixed Content
   (described in [W3C.CR-mixed-content-20160802]) while still providing
   protection against passive attacks.

   Opportunistic Security does not provide the same guarantees as using
   TLS with "https" URIs, because it is vulnerable to active attacks,
   and does not change the security context of the connection.
   Normally, users will not be able to tell that it is in use (i.e.,
   there will be no "lock icon").

Nottingham & Thomson          Experimental                      [Page 2]
RFC 8164              Opportunistic HTTP/2 Security             May 2017

1.1.  Goals and Non-goals

   The immediate goal is to make the use of HTTP more robust in the face
   of pervasive passive monitoring [RFC7258].

   A secondary (but significant) goal is to provide for ease of
   implementation, deployment, and operation.  This mechanism is