[Docs] [txt|pdf|xml] [Tracker] [Email] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12

Network Working Group                                         J. Reschke
Internet-Draft                                                greenbytes
Intended status: Standards Track                               S. Loreto
Expires: December 6, 2015                                       Ericsson
                                                            June 4, 2015


                 'Out-Of-Band' Content Coding for HTTP
                   draft-reschke-http-oob-encoding-00

Abstract

   This document describes an Hypertext Transfer Protocol (HTTP) content
   coding that can be used to describe the location of a secondary
   resource that contans the payload.

Editorial Note (To be removed by RFC Editor before publication)

   Distribution of this document is unlimited.  Although this is not a
   work item of the HTTPbis Working Group, comments should be sent to
   the Hypertext Transfer Protocol (HTTP) mailing list at
   ietf-http-wg@w3.org [1], which may be joined by sending a message
   with subject "subscribe" to ietf-http-wg-request@w3.org [2].

   Discussions of the HTTPbis Working Group are archived at
   <http://lists.w3.org/Archives/Public/ietf-http-wg/>.

   XML versions, latest edits, and issue tracking for this document are
   available from <https://github.com/reschke/oobencoding> and
   <http://greenbytes.de/tech/webdav/#draft-reschke-http-oob-encoding>.

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 December 6, 2015.




Reschke & Loreto        Expires December 6, 2015                [Page 1]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


Copyright Notice

   Copyright (c) 2015 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.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  3
   3.  'Out-Of-Band' Content Coding . . . . . . . . . . . . . . . . .  3
     3.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  4
     3.3.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .  5
       3.3.1.  Basic Example  . . . . . . . . . . . . . . . . . . . .  5
       3.3.2.  Example involving an encryted resource . . . . . . . .  7
   4.  Feature Discovery  . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
     5.1.  Use in Requests  . . . . . . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Alternatives, or: why not a new Status Code?  . . . . 10
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . . . 10
     B.1.  Range Requests . . . . . . . . . . . . . . . . . . . . . . 10
   Appendix C.  Acknowledgements  . . . . . . . . . . . . . . . . . . 10















Reschke & Loreto        Expires December 6, 2015                [Page 2]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


1.  Introduction

   This document describes an Hypertext Transfer Protocol (HTTP) content
   coding (Section 3.1.2.1 of [RFC7231]) that can be used to describe
   the location of a secondary resource that contans the payload.

   The primary use case for this content coding is to enable origin
   servers to delegate the delivery of content to a secondary server
   that might be "closer" to the client (with respect to network
   topology) and/or able to cache content, leveraging content encrytion,
   as described in [ENCRYPTENC].

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This document reuses terminology used in the base HTTP
   specifications, namely Section 2 of [RFC7230] and Section 3 of
   [RFC7231].

3.  'Out-Of-Band' Content Coding

3.1.  Overview

   The 'Out-Of-Band' content coding is used to direct the recipient to
   retrieve the actual message representation (Section 3 of [RFC7231])
   from a secondary resource, such as a public cache:

   1.  Client performs GET request

   2.  Received response specifies the 'out-of-band' content coding; the
       payload of the response contains additional meta data, plus the
       location of the secondary resource

   3.  Client performs GET request on secondary resource (usually again
       via HTTP(s))

   4.  Secondary server provides wrapped HTTP message

   5.  Client unwraps that representation (obtaining a full HTTP
       message)

   6.  Client combines above representation with additional
       representation metadata obtained from the primary resource





Reschke & Loreto        Expires December 6, 2015                [Page 3]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


     Client                  Secondary Server           Origin Server

        sends GET request with Accept-Encoding: out-of-band
   (1) |---------------------------------------------------------\
                      status 200 and Content-Coding: out-of-band |
   (2) <---------------------------------------------------------/

        GET to secondary server
   (3) |---------------------------\
              wrapped HTTP message |
   (4) <---------------------------/

   (5, 6)
      Client and combines HTTP message received in (4)
      with metadata received in (2).

3.2.  Definitions

   The name of the content coding is "out-of-band".

   The payload format uses JavaScript Object Notation (JSON, [RFC7159]),
   describing an array of objects describing secondary resources, each
   containing some of the members below:

   'URI'  A REQUIRED string containing the URI reference (Section 4.1 of
      [RFC3986]) of the secondary resource.

   'metadata'  An OPTIONAL object containing additional members,
      representing header field values to be recombined with the
      metadata from the secondary resource and which can not appear as
      header fields in the response message itself (header fields that
      occur multiple times need to be combined into a single field value
      as per Section 3.2.2 of [RFC7230]; header field names are lower-
      cased).

   The payload format uses a JSON array so that the origin server can
   specify multiple secondary resources.  When a client receives a
   response containing multiple entries, it is free to choose which of
   these to use.

   The representation of the secondary resource needs to use a media
   type capable of representing a full HTTP message.  For now the only
   supported type is "application/http" (Section 8.3.2 of [RFC7230]).

   The client then obtains the original message by:






Reschke & Loreto        Expires December 6, 2015                [Page 4]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


   1.  Unwrap the encapsulated HTTP message by removing any transfer and
       content codings.

       The latter might require additional metadata that could be
       present in the "metadata" object, such as the "Encryption-Key"
       header field described in Section 4 of [ENCRYPTENC].

   2.  Replacing/setting any response header fields from the primary
       response except for framing-related information such as Content-
       Length, Transfer-Encoding and Content-Encoding.

   3.  Replacing/setting any header fields with those present as members
       in the "metadata" object. [[anchor3: Do we have a use case for
       this?]]

   Note that although this mechanism causes the inclusion of external
   content, it will not affect the application-level security properties
   of the reconstructed message, such as its web origin ([RFC6454]).

   The cacheability of the response for the secondary resource does not
   affect the cacheability of the reconstructed response message, which
   is the same as for the origin server's response.

3.3.  Examples

3.3.1.  Basic Example

   Client request of primary resource:

     GET /test HTTP/1.1
     Host: www.example.com
     Accept-Encoding: gzip, out-of-band



















Reschke & Loreto        Expires December 6, 2015                [Page 5]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


   Response:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:00 GMT
     Content-Type: text/plain
     Cache-Control: max-age=10, public
     Content-Encoding: out-of-band
     Content-Length: 76

     [{
       "URI": "http://example.net/bae27c36-fa6a-11e4-ae5d-00059a3c7a00"
     }]

   (note that the Content-Type header field describes the media type of
   the secondary's resource representation)

   Client request for secondary resource:

     GET /bae27c36-fa6a-11e4-ae5d-00059a3c7a00 HTTP/1.1
     Host: example.net


   Response:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:10 GMT
     Content-Type: application/http
     Cache-Control: private
     Content-Length: 115

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 17:00:00 GMT
     Content-Length: 15
     Content-Language: en

     Hello, world.















Reschke & Loreto        Expires December 6, 2015                [Page 6]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


   Final message after recombining header fields:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:00 GMT
     Content-Length: 15
     Cache-Control: max-age=10, public
     Content-Type: text/plain
     Content-Language: en

     Hello, world.

   In this example, Cache-Control, Content-Length, and Date have been
   set/overwritten with data from the primary resource's representation.

3.3.2.  Example involving an encryted resource

   Given the example HTTP message from Section 5.4 of [ENCRYPTENC], a
   primary resource could use the "out-of-band" encoding to specify just
   the location of the secondary resource plus the contents of the
   "Encryption-Key" header field needed to decrypt the payload:

   Response:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:00 GMT
     Content-Encoding: out-of-band
     Content-Type: text/plain
     Content-Length: 192

     [{
       "URI": "http://example.net/bae27c36-fa6a-11e4-ae5d-00059a3c7a00"
       "metadata": {
         "encryption-key": "keyid=\"a1\";
                            key=\"9Z57YCb3dK95dSsdFJbkag\""
       }
     }]

   (note that the Content-Type header field describes the media type of
   the secondary's resource representation)












Reschke & Loreto        Expires December 6, 2015                [Page 7]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


   Response for secondary resource:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:10 GMT
     Content-Type: application/http
     Content-Length: ...
     Cache-Control: private

     HTTP/1.1 200 OK
     Content-Length: 31
     Content-Encoding: aesgcm-128
     Encryption: keyid="a1"; salt="ibZx1RNz537h1XNkRcPpjA"

     zK3kpG__Z8whjIkG6RYgPz11oUkTKcxPy9WP-VPMfuc
   (payload body shown in base64 here)

   Final message after recombining header fields:

     HTTP/1.1 200 OK
     Date: Thu, 14 May 2015 18:52:00 GMT
     Content-Length: 15
     Content-Type: text/plain

     I am the walrus

4.  Feature Discovery

   New content codings can be deployed easily, as the client can use the
   "Accept-Encoding" header field (Section 5.3.4 of [RFC7231]) to signal
   which content codings are supported.

5.  Security Considerations

   [[tbd.security: Such as: how is the secondary resource safe from
   being modified without knowledge of the primary resource?]]

5.1.  Use in Requests

   In general, content codings can be used in both requests and
   responses.  This particular content coding has been designed for
   responses.  When supported in requests, it creates a new attack
   vector where the receiving server can be tricked into including
   content that the client might not have access to otherwise (such as
   HTTP resources behind a firewall).







Reschke & Loreto        Expires December 6, 2015                [Page 8]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


6.  IANA Considerations

   The IANA "HTTP Content Coding Registry", located at
   <http://www.iana.org/assignments/http-parameters>, needs to be
   updated with the registration below:

   Name:  out-of-band

   Description:  Payload needs to be retrieved from a secondary resource

   Reference:  Section 3 of this document

7.  References

7.1.  Normative References

   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
                 RFC2119, March 1997,
                 <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3986]     Berners-Lee, T., Fielding, R., and L. Masinter,
                 "Uniform Resource Identifier (URI): Generic Syntax",
                 STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005,
                 <http://www.rfc-editor.org/info/rfc3986>.

   [RFC7159]     Bray, T., "The JavaScript Object Notation (JSON) Data
                 Interchange Format", RFC 7159, DOI 10.17487/RFC7159,
                 March 2014, <http://www.rfc-editor.org/info/rfc7159>.

   [RFC7230]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
                 Transfer Protocol (HTTP/1.1): Message Syntax and
                 Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014,
                 <http://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
                 Transfer Protocol (HTTP/1.1): Semantics and Content",
                 RFC 7231, DOI 10.17487/RFC7231, June 2014,
                 <http://www.rfc-editor.org/info/rfc7231>.

7.2.  Informative References

   [ENCRYPTENC]  Thomson, M., "Encrypted Content-Encoding for HTTP",
                 draft-thomson-http-encryption-00 (work in progress),
                 May 2015.

   [RFC6454]     Barth, A., "The Web Origin Concept", RFC 6454,
                 DOI 10.17487/RFC6454, December 2011,



Reschke & Loreto        Expires December 6, 2015                [Page 9]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


                 <http://www.rfc-editor.org/info/rfc6454>.

URIs

   [1]  <mailto:ietf-http-wg@w3.org>

   [2]  <mailto:ietf-http-wg-request@w3.org?subject=subscribe>

Appendix A.  Alternatives, or: why not a new Status Code?

   A plausible alternative approach would be to implement this
   functionality one level up, using a new redirect status code (Section
   6.4 of [RFC7231]).  However, this would have several drawbacks:

   o  Servers will need to know whether a client understands the new
      status code; thus some additional signal to opt into this protocol
      would always be needed.

   o  In redirect messages, representation metadata (Section 3.1 of
      [RFC7231]), namely "Content-Type", applies to the response
      message, not the redirected-to resource.

Appendix B.  Open Issues

B.1.  Range Requests

   We probably need to handle Range Requests.  How would this work?
   Passing down the Range request header field to the secondary
   resource?

   What about codes other than 200 and 206?

Appendix C.  Acknowledgements

   Thanks to Goran Eriksson, Mark Nottingham, and Martin Thomson for
   feedback on this document.

Authors' Addresses

   Julian F. Reschke
   greenbytes GmbH
   Hafenweg 16
   Muenster, NW  48155
   Germany

   EMail: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/




Reschke & Loreto        Expires December 6, 2015               [Page 10]


Internet-Draft    'Out-Of-Band' Content Coding for HTTP        June 2015


   Salvatore Loreto
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   EMail: salvatore.loreto@ericsson.com












































Reschke & Loreto        Expires December 6, 2015               [Page 11]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/