Internet DRAFT - draft-pauly-masque-dns-proxy-status
draft-pauly-masque-dns-proxy-status
Network Working Group T. Pauly
Internet-Draft Apple, Inc.
Intended status: Standards Track 4 October 2022
Expires: 7 April 2023
HTTP Proxy-Status Parameter for DNS Information
draft-pauly-masque-dns-proxy-status-00
Abstract
This document defines an HTTP Proxy-Status Parameter that contains
the IP address and CNAME chain received over DNS that was used to
establish the connection to the next hop.
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 7 April 2023.
Copyright Notice
Copyright (c) 2022 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 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. dns-used Parameter . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Proxy-Status HTTP response field [PROXY-STATUS] allows proxies to
convey information about how a proxied request was handled in HTTP
responses sent to clients. It defines a set of parameters that
provide information, such as the name of the next hop.
The Proxy-Status field can be sent by both forward proxies and
gateways (or "reverse proxies"). In the case of forward proxies,
clients are requesting to establish TCP connections (using the
CONNECT method [HTTP]) and UDP connections (using UDP proxying
[CONNECT-UDP]) to a target server. This target server can be
specified using either a hostname or an IP address. When using a
name instead of an IP address, the forward proxy locally performs DNS
resolution to resolve the name to an IPv4 or IPv6 address using A or
AAAA queries.
Clients of forward proxies currently don't have visibility into the
DNS resolution that is performed on the proxy. If available, this
information could be used by clients to help make various decisions
that are influenced by IP addresses and CNAME chains. For example,
some clients classify specific names and IP addresses as being used
for collecting data to track users (which can be used to influence
policies for HTTP cookies), or can recognize them as endpoints that
ought to be blocked for features like ad blocking or malware
blocking. Without this information, proxying using a forward proxy
means that clients lose the ability to fully recognize servers based
on IP addresses and CNAME chains.
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It is possible for clients to perform DNS resolution before using a
forward proxy, and proxy using IP addresses, but this has several
drawbacks: performing DNS without using the proxy can lead a privacy
regression, or a performance regression if the addresses selected are
not optimal for connectivity from the proxy; proxying by IP address
prevents the proxy from selecting the best address
([HAPPY-EYEBALLS]); and if clients try to resolve via the proxy using
DNS over HTTPS ([DOH]), they can incur a performance hit by requiring
an extra round trip before being able to establish a connection.
This document allows clients to receive the IP address and CNAME
chain received from DNS, without needing to perform DNS on the
client, by including the information in a Proxy-Status parameter
(Section 2).
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. dns-used Parameter
The dns-used parameter's value is a String that contains one or more
IP addresses and/or DNS names in a comma-separated list. The first
item in the list SHOULD be the IP address that was resolved using DNS
and was used to open connectivity to the next hop. The remaining
items in the list SHOULD include all names received in CNAME records
[DNS] or AliasMode SVCB or HTTPS records [SVCB] during the course of
resolving the address. Since DNS names can include comma (,)
characters in them, any commas that appear in a DNS names MUST be
represented using a percent-encoded %2C value instead.
For example:
Proxy-Status: proxy.example.net; next-hop=target.example.com
dns-used="2001:db8::1,tracker.example.com."
indicates that proxy.example.net, which used target.example.com as
the next hop for this request, used the IP address "2001:db8::1" to
connect to the target, and encountered the CNAME
"tracker.example.com." in DNS resolution chain. Note that while this
example includes both the next-hop and dns-used parameters, dns-used
can be included without including next-hop.
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The dns-used parameter only applies when DNS was used to resolve the
next hop's name, and does not apply in all situations. Clients can
use the information in this parameter to determine how to use the
connection established through the proxy, but need to gracefully
handle situations in which this parameter is not present.
3. Security Considerations
The dns-used parameter does not include any DNSSEC information or
imply that DNSSEC was used. The information included in the
parameter can only be trusted to be valid insofar as the client
trusts its proxy to provide accurate information. This information
is intended to be used as a hint, and SHOULD NOT be used for making
security decisions about the identity resource access through the
proxy.
4. IANA Considerations
This document registers the "dns-used" parameter in the "HTTP Proxy-
Status Parameters" registry <https://www.iana.org/assignments/http-
proxy-status>.
Name: dns-used
Description: A string containing the IP address used to establish
the proxied connection and the chain of CNAMEs that led to this IP
address.
Reference: This document
5. References
5.1. Normative References
[CONNECT-UDP]
Schinazi, D., "Proxying UDP in HTTP", RFC 9298,
DOI 10.17487/RFC9298, August 2022,
<https://www.rfc-editor.org/rfc/rfc9298>.
[DNS] Barr, D., "Common DNS Operational and Configuration
Errors", RFC 1912, DOI 10.17487/RFC1912, February 1996,
<https://www.rfc-editor.org/rfc/rfc1912>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
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[PROXY-STATUS]
Nottingham, M. and P. Sikora, "The Proxy-Status HTTP
Response Header Field", RFC 9209, DOI 10.17487/RFC9209,
June 2022, <https://www.rfc-editor.org/rfc/rfc9209>.
[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/rfc/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/rfc/rfc8174>.
[SVCB] Schwartz, B. M., Bishop, M., and E. Nygren, "Service
binding and parameter specification via the DNS (DNS SVCB
and HTTPS RRs)", Work in Progress, Internet-Draft, draft-
ietf-dnsop-svcb-https-10, 24 May 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-
svcb-https-10>.
5.2. Informative References
[DOH] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/rfc/rfc8484>.
[HAPPY-EYEBALLS]
Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/rfc/rfc8305>.
Author's Address
Tommy Pauly
Apple, Inc.
Email: tpauly@apple.com
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