Internet DRAFT - draft-pauly-httpbis-geohash-hint
draft-pauly-httpbis-geohash-hint
Network Working Group T. Pauly
Internet-Draft Apple Inc.
Intended status: Experimental D. Schinazi
Expires: 3 April 2022 Google LLC
30 September 2021
The Geohash HTTP Client Hint
draft-pauly-httpbis-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
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This Internet-Draft will expire on 3 April 2022.
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
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and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
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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
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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
characters from the "Geohash alphabet" [GEOHASH].
The following example shows an encoding of the coordinates
57.64911,10.40744:
Sec-CH-Geohash: "u4pruydqqvj"
Servers that can provide different content based on Geohash hints
SHOULD include the headers in their "Accept-CH" list.
Accept-CH: Sec-CH-Geohash
Servers also SHOULD indicate for any cacheable content if the Geohash
hint will influence the cached content, using the "Vary" header.
Vary: Sec-CH-Geohash
3. Server Behavior
Upon receiving a Geohash Client Hint, a server can use the
information to influence its behavior in various ways.
The server can use the Geohash to determine the content of HTTP
responses, as a replacement for inferring location from client IP
addresses.
If the server is acting as a forward proxy, such as a CONNECT proxy,
it can use the Geohash 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].
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3.1. Proxy Behavior
If a proxy receiving the Geohash hint cannot respect the location
indicated by the hint, it SHOULD include a Proxy-Status header
[I-D.ietf-httpbis-proxy-status] in its response, with the "details"
parameter containing the string "invalid geohash".
Proxy-Status: ExampleProxy; details="invalid geohash"
4. Security Considerations
The use of the Geohash Client Hint MUST use the Sec- header prefix as
recommended in [RFC8942].
Client location can be used to fingerprint and tracker users, so
clients MUST have a default policy around when to allow use of the
Geohash Client Hint, as well as a default length of Geohash.
Shorter, truncated Geohashes provide less specific locality.
Servers MUST NOT use Geohash 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.
5. IANA Considerations
5.1. HTTP Headers
This document registers the "Sec-CH-Geohash" header in the "Permanent
Message Header Field Names" registry
<https://www.iana.org/assignments/message-headers>.
+----------------------+----------+--------+---------------+
| Header Field Name | Protocol | Status | Reference |
+----------------------+----------+--------+---------------+
| Sec-CH-Geohash | http | exp | This document |
+----------------------+----------+--------+---------------+
6. References
6.1. Normative References
[I-D.ietf-httpbis-proxy-status]
Nottingham, M. and P. Sikora, "The Proxy-Status HTTP
Response Header Field", Work in Progress, Internet-Draft,
draft-ietf-httpbis-proxy-status-06, 16 August 2021,
<https://www.ietf.org/archive/id/draft-ietf-httpbis-proxy-
status-06.txt>.
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[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>.
[RFC8941] 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>.
[RFC8942] Grigorik, I. and Y. Weiss, "HTTP Client Hints", RFC 8942,
DOI 10.17487/RFC8942, February 2021,
<https://www.rfc-editor.org/info/rfc8942>.
6.2. Informative References
[GEOHASH] "Geohash", 2020, <https://en.wikipedia.org/wiki/Geohash>.
[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>.
[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>.
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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