HTTP Working Group T. Bray Internet-Draft Textuality Intended status: Standards Track November 5, 2015 Expires: May 8, 2016 An HTTP Status Code to Report Legal Obstacles draft-ietf-httpbis-legally-restricted-status-03 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 (, 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. 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 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 May 8, 2016. 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 ( in effect on the date of Bray Expires May 8, 2016 [Page 1] Internet-Draft HTTP-status-451 November 2015 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. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 2 3. 451 Unavailable For Legal Reasons . . . . . . . . . . . . . . 3 4. Identifying Blocking Entities . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 Appendix A. 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 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 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]. Bray Expires May 8, 2016 [Page 2] Internet-Draft HTTP-status-451 November 2015 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 Legal Reasons Link: ; rel="blocked-by" Content-Type: text/html Unavailable For Legal Reasons

Unavailable For Legal Reasons

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.

The use of the 451 status code implies neither the existence nor non- existence 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; 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- Bray Expires May 8, 2016 [Page 3] Internet-Draft HTTP-status-451 November 2015 access path which could choose to deny access, for 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 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 updated with the following entry: o Code: 451 o Description: Unavailable for Legal Reasons o Specification: [ this document ] The Link Relation Type Registry should updated with the following entry: o Relation Name: blocked-by o Description: Identifies the entity blocking access to a resource folllowing on receipt of a legal demand. o Reference: This document Bray Expires May 8, 2016 [Page 4] Internet-Draft HTTP-status-451 November 2015 7. 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, . [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, . [RFC4084] Klensin, J., "Terminology for Describing Internet Connectivity", BCP 104, RFC 4084, DOI 10.17487/RFC4084, May 2005, . [RFC4924] Aboba, B., Ed. and E. Davies, "Reflections on Internet Transparency", RFC 4924, DOI 10.17487/RFC4924, July 2007, . [RFC5988] Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/ RFC5988, October 2010, . [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, . 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: URI: Bray Expires May 8, 2016 [Page 5]