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The IP Geolocation HTTP Client Hint
draft-pauly-httpbis-geoip-hint-00

Document Type Active Internet-Draft (candidate for httpbis WG)
Authors Tommy Pauly , David Schinazi
Last updated 2022-09-04 (Latest revision 2022-03-30)
Replaces draft-pauly-httpbis-geohash-hint
Stream Internet Engineering Task Force (IETF)
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draft-pauly-httpbis-geoip-hint-00
Network Working Group                                           T. Pauly
Internet-Draft                                                Apple Inc.
Intended status: Experimental                                D. Schinazi
Expires: 1 October 2022                                       Google LLC
                                                           30 March 2022

                  The IP Geolocation HTTP Client Hint
                   draft-pauly-httpbis-geoip-hint-00

Abstract

   This documents defines an HTTP Client Hint that allows a client to
   share information about its IP Geolocation.  This helps ensure that
   servers have information about location that is consistent with what
   a client expects and what other servers use.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/tfpauly/privacy-proxy.

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 1 October 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  IP Geo Header . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Server Behavior . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  HTTP Headers  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   HTTP Client Hints [RFC8942] defines a convention for HTTP headers to
   communicate optional information from clients to servers as hints.
   This can be done conditionally based on if a server claims supports
   for a particular hint.

   This document defines a client hint that can be used to send a IP
   geolocation entry that maps to the client's IP address.  This
   location can be used to influence server behavior, such as by causing
   the server to return responses relevant to the client's location.
   The format of the IP geolocation entry is the same as that defined
   for IP geolocation feeds in [GEOFEED].

   This header is intended to be used to provide rough geolocation hints
   to servers that do not already have accurate or authoritative
   mappings for the IP addresses of clients.  This can be particularly
   useful for cases where IP geolocation mappings have changed recently,
   or a client is using a VPN or proxy that may not be commonly
   recognized by servers.

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   The mechanism for how a client learns the IP geolocation mapping to
   send is beyond the scope of this document.  [RFC9092] defines some
   mechanisms for discovery, but clients can also have other mechanisms
   (such as coordinating with a VPN or proxy that is assigning the
   client a tunnelled or proxied address) to learn what hint to sent.

1.1.  Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  IP Geo Header

   The "Sec-CH-IP-Geo" is an Item Structured Field [STRUCTURED-FIELDS].
   The field's value is a String.  The string uses the format defined in
   Section 2.1.1 of [GEOFEED], with the IP Prefix element removed.
   Thus, this contains a comma-separated list of Alpha2code, Region, and
   City.  The value SHOULD NOT contain a Postal Code.

   For example, the header for an entry "192.0.2.5,US,US-AL,Alabaster"
   would be:

       Sec-CH-IP-Geo = "US,US-AL,Alabaster"

   This field also defines a parameter, "feed", that contains the URI of
   the IP geolocation feed that is authoritative for this entry.  For
   example:

    Sec-CH-IP-Geo = "SG,SG-01,Singapore"; feed="https://noc.ietf.org/geo/google.csv"

   Servers that can provide different content based on Geohash hints
   SHOULD include the headers in their "Accept-CH" list.

       Accept-CH: Sec-CH-IP-Geo

   Servers also SHOULD indicate for any cacheable content if the IP geo
   hints will influence the cached content, using the "Vary" header.

       Vary: Sec-CH-IP-Geo

3.  Server Behavior

   Upon receiving a IP Geolocation Client Hint, a server can use the
   information to influence its behavior in various ways, such as
   determining the content of HTTP responses.

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   Many servers have existing IP geolocation feeds that they use to
   identify client locations.  Servers can choose to use the hint value
   in one of several ways:

   *  Use the client hint information instead of consulting another
      geolocation feed.

   *  Check the value of the "feed" parameter on the header and
      determine if it is a trusted feed.  If this feed is trusted, but
      is not the default feed used by the server, the server can choose
      to prefer the feed indicated by the client.

   *  Check the value of the "feed" parameter on the header and fetch a
      copy of the feed to verify the mapping, if a copy of the feed has
      not been fetched recently.

   *  If the feed indicated in the "feed" parameter is unknown or
      untrusted, but starts becoming common, the server can flag this
      feed as one to be manually checked and added, if appropriate.
      This allows servers to automatically discover when new feeds and
      services are brought up..

   If the server is acting as a forward proxy, such as a CONNECT proxy,
   it can use the hint to determine an appropriate geo-mapped IP address
   to use for outbound connections, or a client subnet to present in the
   EDNS0 Client Subnet extension for DNS queries [RFC6891] [RFC7871].

4.  Security Considerations

   The use of the IP Geolocation Client Hint MUST use the Sec- header
   prefix as recommended in [RFC8942].

   Servers MUST NOT use IP Geolocation Client Hints for making security
   or access-control decisions, as the value can be spoofed by a client.
   The hint is intended only for use in optimizing behavior.

   The value contained in this hint SHOULD be based only on a IP
   Geolocation feed value for an IP address the client is already
   presenting to a server.  In order to avoid disclosing any private
   information, this value MUST not be based on geolocation of the
   client determined by other means, such as physical latitude and
   longitude coordinates.

5.  IANA Considerations

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5.1.  HTTP Headers

   This document registers the "Sec-CH-IP-Geo" header in the "Permanent
   Message Header Field Names" registry
   <https://www.iana.org/assignments/message-headers>.

     +----------------------+----------+--------+---------------+
     | Header Field Name    | Protocol | Status |   Reference   |
     +----------------------+----------+--------+---------------+
     | Sec-CH-IP-Geo        |   http   |  exp   | This document |
     +----------------------+----------+--------+---------------+

6.  References

6.1.  Normative References

   [GEOFEED]  Kline, E., Duleba, K., Szamonek, Z., Moser, S., and W.
              Kumari, "A Format for Self-Published IP Geolocation
              Feeds", RFC 8805, DOI 10.17487/RFC8805, August 2020,
              <https://www.rfc-editor.org/info/rfc8805>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8942]  Grigorik, I. and Y. Weiss, "HTTP Client Hints", RFC 8942,
              DOI 10.17487/RFC8942, February 2021,
              <https://www.rfc-editor.org/info/rfc8942>.

   [STRUCTURED-FIELDS]
              Nottingham, M. and P-H. Kamp, "Structured Field Values for
              HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
              <https://www.rfc-editor.org/info/rfc8941>.

6.2.  Informative References

   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891,
              DOI 10.17487/RFC6891, April 2013,
              <https://www.rfc-editor.org/info/rfc6891>.

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   [RFC7871]  Contavalli, C., van der Gaast, W., Lawrence, D., and W.
              Kumari, "Client Subnet in DNS Queries", RFC 7871,
              DOI 10.17487/RFC7871, May 2016,
              <https://www.rfc-editor.org/info/rfc7871>.

   [RFC9092]  Bush, R., Candela, M., Kumari, W., and R. Housley,
              "Finding and Using Geofeed Data", RFC 9092,
              DOI 10.17487/RFC9092, July 2021,
              <https://www.rfc-editor.org/info/rfc9092>.

Authors' Addresses

   Tommy Pauly
   Apple Inc.
   One Apple Park Way
   Cupertino, California 95014,
   United States of America
   Email: tpauly@apple.com

   David Schinazi
   Google LLC
   Email: dschinazi.ietf@gmail.com

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