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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-08) exists of draft-ietf-httpbis-proxy-status-06 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Pauly 3 Internet-Draft Apple Inc. 4 Intended status: Experimental D. Schinazi 5 Expires: 3 April 2022 Google LLC 6 30 September 2021 8 The Geohash HTTP Client Hint 9 draft-pauly-httpbis-geohash-hint-00 11 Abstract 13 This documents defines an HTTP Client Hint for sharing a client's 14 rough location using the Geohash format. 16 Discussion Venues 18 This note is to be removed before publishing as an RFC. 20 Source for this draft and an issue tracker can be found at 21 https://github.com/tfpauly/privacy-proxy. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on 3 April 2022. 40 Copyright Notice 42 Copyright (c) 2021 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 47 license-info) in effect on the date of publication of this document. 48 Please review these documents carefully, as they describe your rights 49 and restrictions with respect to this document. Code Components 50 extracted from this document must include Simplified BSD License text 51 as described in Section 4.e of the Trust Legal Provisions and are 52 provided without warranty as described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Geohash Header . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. Server Behavior . . . . . . . . . . . . . . . . . . . . . . . 3 60 3.1. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . 4 61 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 62 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 63 5.1. HTTP Headers . . . . . . . . . . . . . . . . . . . . . . 4 64 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 66 6.2. Informative References . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 69 1. Introduction 71 HTTP Client Hints [RFC8942] defines a convention for HTTP headers to 72 communicate optional information from clients to servers as hints. 73 This can be done conditionally based on if a server claims supports 74 for a particular hint. 76 This document defines a client hint that can be used to send a 77 location that the client wants to use for influencing server 78 behavior. It uses the Geohash algorithm [GEOHASH] to encode latitude 79 and longitude coordinates into an alphanumeric token that can be 80 truncated to provide a less specific location. 82 This header is intended to be used to provide rough geolocation hints 83 to servers in situations where the server cannot directly ascertain 84 the location of the client. For example, a client that is accessing 85 a server through a proxy or a VPN might provide a rough hint to a 86 server when looking up information that may vary depending on 87 location. 89 This document also defines a how forward proxies can use proxy status 90 fields to inform clients about the result of their Geohash hints. 92 1.1. Requirements 94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 95 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 96 "OPTIONAL" in this document are to be interpreted as described in 97 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 98 capitals, as shown here. 100 2. Geohash Header 102 The "Sec-CH-Geohash" is an Item Structured Header [RFC8941]. Its 103 value MUST be a String, and MUST have at least 1 character and no 104 more than 12 characters. The ABNF is: 106 Sec-CH-Geohash = sf-string 108 The string itself is an encoded Geohash, which uses the 32 different 109 characters from the "Geohash alphabet" [GEOHASH]. 111 The following example shows an encoding of the coordinates 112 57.64911,10.40744: 114 Sec-CH-Geohash: "u4pruydqqvj" 116 Servers that can provide different content based on Geohash hints 117 SHOULD include the headers in their "Accept-CH" list. 119 Accept-CH: Sec-CH-Geohash 121 Servers also SHOULD indicate for any cacheable content if the Geohash 122 hint will influence the cached content, using the "Vary" header. 124 Vary: Sec-CH-Geohash 126 3. Server Behavior 128 Upon receiving a Geohash Client Hint, a server can use the 129 information to influence its behavior in various ways. 131 The server can use the Geohash to determine the content of HTTP 132 responses, as a replacement for inferring location from client IP 133 addresses. 135 If the server is acting as a forward proxy, such as a CONNECT proxy, 136 it can use the Geohash to determine an appropriate geo-mapped IP 137 address to use for outbound connections, or a client subnet to 138 present in the EDNS0 Client Subnet extension for DNS queries 139 [RFC6891] [RFC7871]. 141 3.1. Proxy Behavior 143 If a proxy receiving the Geohash hint cannot respect the location 144 indicated by the hint, it SHOULD include a Proxy-Status header 145 [I-D.ietf-httpbis-proxy-status] in its response, with the "details" 146 parameter containing the string "invalid geohash". 148 Proxy-Status: ExampleProxy; details="invalid geohash" 150 4. Security Considerations 152 The use of the Geohash Client Hint MUST use the Sec- header prefix as 153 recommended in [RFC8942]. 155 Client location can be used to fingerprint and tracker users, so 156 clients MUST have a default policy around when to allow use of the 157 Geohash Client Hint, as well as a default length of Geohash. 158 Shorter, truncated Geohashes provide less specific locality. 160 Servers MUST NOT use Geohash Client Hints for making security or 161 access-control decisions, as the value can be spoofed by a client. 162 The hint is intended only for use in optimizing behavior. 164 5. IANA Considerations 166 5.1. HTTP Headers 168 This document registers the "Sec-CH-Geohash" header in the "Permanent 169 Message Header Field Names" registry 170 . 172 +----------------------+----------+--------+---------------+ 173 | Header Field Name | Protocol | Status | Reference | 174 +----------------------+----------+--------+---------------+ 175 | Sec-CH-Geohash | http | exp | This document | 176 +----------------------+----------+--------+---------------+ 178 6. References 180 6.1. Normative References 182 [I-D.ietf-httpbis-proxy-status] 183 Nottingham, M. and P. Sikora, "The Proxy-Status HTTP 184 Response Header Field", Work in Progress, Internet-Draft, 185 draft-ietf-httpbis-proxy-status-06, 16 August 2021, 186 . 189 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 190 Requirement Levels", BCP 14, RFC 2119, 191 DOI 10.17487/RFC2119, March 1997, 192 . 194 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 195 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 196 May 2017, . 198 [RFC8941] Nottingham, M. and P-H. Kamp, "Structured Field Values for 199 HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021, 200 . 202 [RFC8942] Grigorik, I. and Y. Weiss, "HTTP Client Hints", RFC 8942, 203 DOI 10.17487/RFC8942, February 2021, 204 . 206 6.2. Informative References 208 [GEOHASH] "Geohash", 2020, . 210 [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms 211 for DNS (EDNS(0))", STD 75, RFC 6891, 212 DOI 10.17487/RFC6891, April 2013, 213 . 215 [RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W. 216 Kumari, "Client Subnet in DNS Queries", RFC 7871, 217 DOI 10.17487/RFC7871, May 2016, 218 . 220 Authors' Addresses 222 Tommy Pauly 223 Apple Inc. 224 One Apple Park Way 225 Cupertino, California 95014, 226 United States of America 228 Email: tpauly@apple.com 230 David Schinazi 231 Google LLC 233 Email: dschinazi.ietf@gmail.com