The Geohash HTTP Client Hint
draft-geohash-hint-00

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Network Working Group                                           T. Pauly
Internet-Draft                                                Apple Inc.
Intended status: Experimental                           19 February 2021
Expires: 23 August 2021

                      The Geohash HTTP Client Hint
                         draft-geohash-hint-00

Abstract

   This documents defines an HTTP Client Hint for sharing a client's
   rough location using the Geohash format.

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
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   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 23 August 2021.

Copyright Notice

   Copyright (c) 2021 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 carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components

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   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
     1.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Geohash Header  . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Server Behavior . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Proxy Behavior  . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  HTTP Headers  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

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
   location that the client wants to use for influencing server
   behavior.  It uses the Geohash algorithm [GEOHASH] to encode latitude
   and longitude coordinates into an alphanumeric token that can be
   truncated to provide a less specific location.

   This header is intended to be used to provide rough geolocation hints
   to servers in situations where the server cannot directly ascertain
   the location of the client.  For example, a client that is accessing
   a server through a proxy or a VPN might provide a rough hint to a
   server when looking up information that may vary depending on
   location.

   This document also defines a how forward proxies can use proxy status
   fields to inform clients about the result of their Geohash hints.

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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.  Geohash Header

   The "Sec-CH-Geohash" is an Item Structured Header [RFC8941].  Its
   value MUST be a String, and MUST have at least 1 character and no
   more than 12 characters.  The ABNF is:

      Sec-CH-Geohash = sf-string

   The string itself is an encoded Geohash, which uses the 32 different