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Versions: (draft-451-new-protocol-elements) 00 01 02 03 Draft is active
In: Waiting_for_Writeup
Network Working Group                                           S. Sahib
Internet-Draft                                             June 29, 2018
Intended status: Informational
Expires: December 31, 2018


             New protocol elements for HTTP Status Code 451
                draft-sahib-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.  Also included
   is an analysis of HTTP 451 from a human rights perspective using
   guidelines from RFC8280.

   Discussion of this draft is at https://www.irtf.org/mailman/listinfo/
   hrpc [1] and https://lists.ghserv.net/mailman/listinfo/statuscode451
   [2].

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 https://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 31, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Existing Protocol Elements  . . . . . . . . . . . . . . . . .   3
   4.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Human Rights Considerations . . . . . . . . . . . . . . . . .   5
     7.1.  Connectivity  . . . . . . . . . . . . . . . . . . . . . .   5
     7.2.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.3.  Content Agnosticism . . . . . . . . . . . . . . . . . . .   5
     7.4.  Security  . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.5.  Internationalization  . . . . . . . . . . . . . . . . . .   5
     7.6.  Censorship Resistance . . . . . . . . . . . . . . . . . .   6
     7.7.  Open Standards  . . . . . . . . . . . . . . . . . . . . .   6
     7.8.  Heterogeneity Support . . . . . . . . . . . . . . . . . .   6
     7.9.  Anonymity . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.10. Pseudonymity  . . . . . . . . . . . . . . . . . . . . . .   6
     7.11. Accessibility . . . . . . . . . . . . . . . . . . . . . .   6
     7.12. Localization  . . . . . . . . . . . . . . . . . . . . . .   6
     7.13. Decentralization  . . . . . . . . . . . . . . . . . . . .   6
     7.14. Reliability . . . . . . . . . . . . . . . . . . . . . . .   7
     7.15. Confidentiality . . . . . . . . . . . . . . . . . . . . .   7
     7.16. Integrity . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.17. Authenticity  . . . . . . . . . . . . . . . . . . . . . .   7
     7.18. Adaptability  . . . . . . . . . . . . . . . . . . . . . .   7
     7.19. Outcome Transparency  . . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

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".





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   Subsequently, an effort was made to investigate usage of HTTP 451 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.  In
   addition, specific recommendations are made in order to disambiguate
   cases where the status code may or may not be used.

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.  Note that while the introduction of [RFC7725] mentions
      that the legal demand for denial of access should be related to
      the resource being requested, the RFC's description does not make
      it clear that the resource being denied access to must be directly
      mentioned in the legal demand.

   -  Responses using the status code SHOULD include an explanation in
      the response body of the details of the legal demand.

   -  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

   -  HTTP 451 SHOULD NOT be used by an operator to deny access to a
      resource on the basis of a legal demand that is not specific to
      the requested resource.

   -  HTTP 451 SHOULD NOT be used by an operator to deny access to a
      resource on the basis of a policy specified by the operator (as
      opposed to a legal demand being placed on the operator).





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   -  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.  [IMPL_REPORT_DRAFT] notes that
      there is confusion amongst implementors of [RFC7725] about the
      meaning of the term "blocked-by", perhaps in part because of the
      example given [ERRATA_ID-5181] - it would be useful to explicitly
      include space for both, as both provide essential information
      about the legal block.

   -  HTTP status code 451 is increasingly being used to deny access to
      resources based on geographical IP.  The response SHOULD contain a
      provisional header with geographical scope of block.  This scope
      SHOULD correspond to comma-separated list of alpha-2 country codes
      defined in [ISO.3166-1].  The rationale for keeping the
      geographical scope to country-level granularity is that most
      blocks are mandated by national governments [IMPL_REPORT_DRAFT].
      In addition, as the serving of this status code is voluntary,
      there is value in not complicating the specification.

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:

   -  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:

   -  Header field name: geo-scope-block

   -  Applicable protocol: http




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   -  Status: provisional

   -  Specification document(s): this document

7.  Human Rights Considerations

   The use of HTTP 451 has implications for human rights, and is thus
   worth examining under the guidelines for developing human rights
   considerations for protocols [RFC8280].

7.1.  Connectivity

   HTTP 451 status code response can be sent by the server hosting the
   blocked resource (end node) or an intermediary node that implements
   the block.  If a resource is "blocked-by" a particular ISP then the
   ISP will be the one serving the status code.

7.2.  Privacy

   HTTP 451 is used as a response when the client requests a resource
   that's unavailable because of legal reasons.  Consequentially, there
   are potential privacy (and anonymity) ramifications if there is
   leakage of who accessed what resource.

   HTTP status code 451 is cacheable by default [RFC7725].  Caching
   status code 451 on users' devices means that there will be a record
   of their attempt to access the blocked content stored on their
   devices.  If caching is used, the software used to access the web
   resource should notify users that the HTTP 451 response has been
   received and cached.

7.3.  Content Agnosticism

   The scope of the blocking order may be geographical in nature.  This
   results in an issue related to content agnosticism.  This is not a
   protocol issue, but rather an artefact of the blocking order.

7.4.  Security

   Refer to section 5, Security Considerations, of [RFC7725].

7.5.  Internationalization

   [RFC7725] does not require the use of any particular language for
   user-facing strings such as the response body or the value of the
   header fields.  The header field names, however, are in English.
   This is a common attribute of protocol elements within the IETF
   [RFC2277].



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7.6.  Censorship Resistance

   While HTTP 451 status code cannot prevent censorship, it can help
   make some kinds of censorship (i.e. where the censorer is interested
   and able to provide information about the block) more transparent and
   make its assessment easier by providing information about the block
   in a parseable manner.

7.7.  Open Standards

   [RFC7725] is an open standard.

7.8.  Heterogeneity Support

   An HTTP 451 status code response can be used for any web resource and
   for any software that is capable of understanding HTTP header
   responses.

7.9.  Anonymity

   HTTP 451 is an HTTP status code.  If the connection between the
   client and the server is not over HTTPS, then there is potential for
   a network observer to identify what a particular user is accessing.
   Even with HTTPS, meta-data might be available that could be used to
   identify a user.

7.10.  Pseudonymity

   HTTP 451 does not involve pseudonyms or nicknames.

7.11.  Accessibility

   HTTP 451, being an HTTP status code, does not prescribe how the
   client should parse the information contained in the response fields.
   Depending on the software that is used to access the resource, there
   could be accessibility concerns related to understanding this
   information.

7.12.  Localization

   The values of the header fields and the response body can be
   localized by the blocker to suit the geographical scope of the block.

7.13.  Decentralization

   HTTP 451 is used to provide information about a block mandated by a
   (centralized) blocking authority.  The status code itself does not
   add any additional centralization.



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7.14.  Reliability

   HTTP 451 does not by itself prevent the misuse of the status code or
   wrong tagging of resources.  The informational requirement as part of
   the protocol address this concern to some extent, but commonly it
   will be difficult for the end user to verify if the code has been
   correctly used.  Objective of this draft is to increase reliability
   by making it clearer what a good HTTP 451 response looks like.

7.15.  Confidentiality

   HTTP 451 status code use implies sharing of information by the
   reporter that make it easier to identify where censorship is taking
   place.  See section on Privacy and Anonymity.

7.16.  Integrity

   HTTP 451 does not prescribe the use of any encryption to transport
   it, and is thus susceptible to leakage through man-in-the-middle
   attacks.

7.17.  Authenticity

   Authenticity of the server implementing HTTP 451 is dependent on the
   connection being over HTTPS.

7.18.  Adaptability

   HTTP 451 does not have any legal or technical limitations which
   prevents the development of other standards / protocols.

7.19.  Outcome Transparency

   The assumption behind the development of the status code 451 is that
   transparency has a chilling effect on censorship and that
   transparency will allow acts of censorship to be challenged.  In some
   countries, blocks orders are unevenly implemented by ISPs either
   because it does not serve their bottom-lines or they are resisting
   censorship - governments in those countries could mandate the
   implementation of status code 451 which will make it easier for them
   to monitor the implementation of their block orders.  Surveillance
   systems in some countries could be updated to watch out for the 451
   error code on unencrypted traffic making it easier to identify those
   trying to access prohibited content.  Before the implementation of
   this standard there would be no uniformity in which websites would
   implement a block order increasing the number of false positives for
   any automated monitoring systems.




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Acknowledgements

   Thanks to Alp Toker, Christine Runnegar, Niels ten Oever, Stephane
   Bortzmeyer, Corinne Cath and many others on the HRPC mailing list
   (linked above) for reviewing and brainstorming.

9.  References

9.1.  Normative References

   [ERRATA_ID-5181]
              Bortzmeyer, S., "[Technical Errata Reported] RFC7725
              (5181)", 2017,
              <https://www.rfc-editor.org/errata/eid5181>.

   [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,
              <https://tools.ietf.org/html/draft-451-imp-report-00>.

   [ISO.3166-1]
              International Organization for Standardization, "Codes for
              the representation of names of countries and their
              subdivisions - Part 1: Country code", ISO Standard 3166-
              1:1997 , 1997.

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

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277,
              January 1998, <https://www.rfc-editor.org/info/rfc2277>.

   [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,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC7725]  Bray, T., "An HTTP Status Code to Report Legal Obstacles",
              RFC 7725, DOI 10.17487/RFC7725, February 2016,
              <https://www.rfc-editor.org/info/rfc7725>.

   [RFC8280]  ten Oever, N. and C. Cath, "Research into Human Rights
              Protocol Considerations", RFC 8280, DOI 10.17487/RFC8280,
              October 2017, <https://www.rfc-editor.org/info/rfc8280>.



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   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/info/rfc8288>.

9.2.  URIs

   [1] https://www.irtf.org/mailman/listinfo/hrpc

   [2] https://lists.ghserv.net/mailman/listinfo/statuscode451

Author's Address

   Shivan Kaul Sahib

   EMail: shivankaulsahib@gmail.com




































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