HTTP Working Group S. Sahib Internet-Draft October 27, 2017 Intended status: Informational Expires: April 30, 2018 New protocol elements for HTTP Status Code 451 draft-451-new-protocol-elements-01 Abstract This draft recommends protocol updates to Hypertext Transfer Protocol (HTTP) status code 451 (defined by RFC7725) based on an examination of how the new status code is being used by parties involved in denial of Internet resources because of legal demands. Discussion of this draft is at https://www.irtf.org/mailman/listinfo/ hrpc and https://lists.ghserv.net/mailman/listinfo/statuscode451. 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/. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Sahib Expires April 30, 2018 [Page 1] Internet-Draft New elements for HTTP 451 October 2017 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. Existing Protocol Elements . . . . . . . . . . . . . . . . . 2 4. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 7. Normative References . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction [RFC7725] was standardized by the IETF in February 2016. It defined HTTP status code 451 - to be used when a "a server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource". The intention was to provide a uniform mechanism to indicate online censorship. Subsequently, an effort was made to investigate usage of 451 status code and evaluate if it fulfills its mandate of providing "transparency in circumstances where issues of law or public policy affect server operations" [IMPL_REPORT_DRAFT]. This draft attempts to explicate the protocol recommendations arising out of that investigation. 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. Existing Protocol Elements The status code as standardized by the IETF specifies the following elements [RFC7725] - - A server can return status code 451 to indicate that it is denying access to a resource or multiple resources on account of a legal demand. - Responses using the status code SHOULD include an explanation in the response body of the details of the legal demand. Sahib Expires April 30, 2018 [Page 2] Internet-Draft New elements for HTTP 451 October 2017 - Responses SHOULD include a "Link" HTTP header field [RFC8288] whose value is a URI reference [RFC3986] identifying itself. 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. 4. Recommendations - In addition to the "blocked-by" header, an HTTP response with status code 451 SHOULD include another "Link" HTTP header field which has a "rel" parameter whose value is "blocking-authority". It's important to distinguish between the implementer of the block, and the authority that mandated the block in the first place. This is because these two organizations might not be the same - a government (the blocking authority) could force an Internet Service Provider (the implementer of the block) to deny access to a certain resource. - HTTP status code 451 is increasingly being used to deny access to resources based on geographical IP. The scope of this denial is sometimes as finely scoped as a city or a province. The response SHOULD contain a provisional header with geographical scope of block. 5. Security Considerations This document does not add additional security considerations to [RFC7725]. 6. IANA Considerations The Link Relation Type Registry should be updated with the following entry [TBD]: - Relation Name: blocking-authority - Description: Identifies the authority that has issued the block. - Reference: This document In addition, IANA should be updated with the following provisional header [TBD]: - Header field name: geo-scope-block - Applicable protocol: http Sahib Expires April 30, 2018 [Page 3] Internet-Draft New elements for HTTP 451 October 2017 - Status: provisional - Specification document(s): this document 7. Normative References [IMPL_REPORT_DRAFT] Abraham, S., Canales, MP., Hall, J., Khrustaleva, O., ten Oever, N., Runnegar, C., and S. Sahib, "Implementation Report for HTTP Status Code 451", 2017, . [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, . [RFC7725] Bray, T., "An HTTP Status Code to Report Legal Obstacles", RFC 7725, DOI 10.17487/RFC7725, February 2016, . [RFC8288] Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, October 2017, . Author's Address Shivan Kaul Sahib EMail: shivankaulsahib@gmail.com Sahib Expires April 30, 2018 [Page 4]