HTTP Working Group
Internet Engineering Task Force (IETF)                           T. Bray
Internet-Draft
Request for Comments: 7725                                    Textuality
Intended status:
Category: Standards Track                       November 10, 2015
Expires: May 13,                                  February 2016
ISSN: 2070-1721

             An HTTP Status Code to Report Legal Obstacles
            draft-ietf-httpbis-legally-restricted-status-04

Abstract

   This document specifies a Hypertext Transfer Protocol (HTTP) status
   code for use when resource access is denied as a consequence of legal
   demands.

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

   Discussion of this draft takes place on the HTTPBIS working group
   mailing list (ietf-http-wg@w3.org), which is archived at [1].

   Working Group information can be found at [2] and [3]; source code
   and issues list for this draft can be found at [4].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on May 13, 2016.
   http://www.rfc-editor.org/info/rfc7725.

Copyright Notice

   Copyright (c) 2015 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  451 Unavailable For Legal Reasons . . . . . . . . . . . . . .   3   2
   4.  Identifying Blocking Entities . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Appendix A.   4
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   This document specifies a Hypertext Transfer Protocol (HTTP) status
   code for use when a server operator has received a legal demand to
   deny access to a resource or to a set of resources which that includes the
   requested resource.

   This status code can be used to provide transparency in circumstances
   where issues of law or public policy affect server operations.  This
   transparency may be beneficial both to these operators and to end
   users.

   [RFC4924] discusses the forces working against transparent operation
   of the Internet; these clearly include legal interventions to
   restrict access to content.  As that document notes, and as Section 4
   of [RFC4084] states, such restrictions should be made explicit.

   Feedback should occur on the ietf-http-wg@w3.org mailing list.

2.  Requirements

   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].

3.  451 Unavailable For Legal Reasons

   This status code indicates that the server is denying access to the
   resource as a consequence of a legal demand.

   The server in question might not be an origin server.  This type of
   legal demand typically most directly affects the operations of ISPs
   and search engines.

   Responses using this status code SHOULD include an explanation, in
   the response body, of the details of the legal demand: the party
   making it, the applicable legislation or regulation, and what classes
   of person and resource it applies to.  For example:

   HTTP/1.1 451 Unavailable For for Legal Reasons
   Link: <https://spqr.example.org/legislatione>; rel="blocked-by"
   Content-Type: text/html

   <html>
    <head><title>Unavailable For for Legal Reasons</title></head>
    <body>
     <h1>Unavailable For for Legal Reasons</h1>
     <p>This request may not be serviced in the Roman Province
     of Judea due to the Lex Julia Majestatis, which disallows
     access to resources hosted on servers deemed to be
     operated by the People's Front of Judea.</p>
    </body>
   </html>

   The use of the 451 status code implies neither the existence nor non-
   existence
   nonexistence of the resource named in the request.  That is to say,
   it is possible that if the legal demands were removed, a request for
   the resource still might not succeed.

   Note that in many cases clients can still access the denied resource
   by using technical countermeasures such as a VPN or the Tor network.

   A 451 response is cacheable by default; default, i.e., unless otherwise
   indicated by the method definition or explicit cache controls; see
   [RFC7234].

4.  Identifying Blocking Entities

   As noted above, when an attempt to access a resource fails with
   status 451, the entity blocking access might or might not be the
   origin server.  There are a variety of entities in the resource-
   access path which that could choose to deny access, access -- for example example, ISPs,
   cache providers, and DNS servers.

   It is useful, when legal blockages occur, to be able to identify the
   entities actually implementing the blocking.

   When an entity blocks access to a resource and returns status 451, it
   SHOULD include a "Link" HTTP header field [RFC5988] whose value is a
   URI reference [RFC3986] identifying itself.  When used for this
   purpose, the "Link" header field MUST have a "rel" parameter whose
   value is "blocked-by".

   The intent is that the header be used to identify the entity actually
   implementing blockage, not any other entity mandating it.  A human human-
   readable response body, as discussed above, is the appropriate
   location for discussion of administrative and policy issues.

5.  Security Considerations

   Clients cannot rely upon the use of the 451 status code.  It is
   possible that certain legal authorities might wish to avoid
   transparency, and not only demand the restriction of access to
   certain resources, but also avoid disclosing that the demand was
   made.

6.  IANA Considerations

   The HTTP Status Codes Registry should be has been updated with the following
   entry:

   o  Code: 451

   o  Description: Unavailable for Legal Reasons

   o  Specification: [ this document ] RFC 7725

   The Link Relation Type Registry should has been updated with the following
   entry:

   o  Relation Name: blocked-by

   o  Description: Identifies the entity blocking access to a resource
      folllowing
      following on receipt of a legal demand.

   o  Reference: This document RFC 7725

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, 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>.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/
              RFC5988, 10.17487/RFC5988, October 2010,
              <http://www.rfc-editor.org/info/rfc5988>.

   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              RFC 7234, DOI 10.17487/RFC7234, June 2014,
              <http://www.rfc-editor.org/info/rfc7234>.

7.2.  Informative References

   [RFC4084]  Klensin, J., "Terminology for Describing Internet
              Connectivity", BCP 104, RFC 4084, DOI 10.17487/RFC4084,
              May 2005, <http://www.rfc-editor.org/info/rfc4084>.

   [RFC4924]  Aboba, B., Ed. and E. Davies, "Reflections on Internet
              Transparency", RFC 4924, DOI 10.17487/RFC4924, July 2007,
              <http://www.rfc-editor.org/info/rfc4924>.

Appendix A.

Acknowledgements

   Thanks to Terence Eden, who observed that the existing status code
   403 was not really suitable for this situation, and suggested the
   creation of a new status code.

   Thanks also to Ray Bradbury.

Author's Address

   Tim Bray
   Textuality

   Email: tbray@textuality.com
   URI:   http://www.tbray.org/ongoing/