Internet DRAFT - draft-pauly-httpbis-alias-proxy-status
draft-pauly-httpbis-alias-proxy-status
Network Working Group T. Pauly
Internet-Draft Apple, Inc.
Intended status: Standards Track 30 November 2022
Expires: 3 June 2023
HTTP Proxy-Status Parameter for Next-Hop Aliases
draft-pauly-httpbis-alias-proxy-status-00
Abstract
This document defines an HTTP Proxy-Status Parameter that contains a
list of aliases received over DNS when establishing a 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 3 June 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3
2. next-hop-aliases Parameter . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3
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.
[PROXY-STATUS] defines a next-hop parameter, which can contain a
hostname, IP address, or alias of the next hop. This parameter can
contain only one such item, so it cannot be used to communicate a
chain of aliases encountered during DNS resolution when connecting to
the next hop.
Knowing the full chain of aliases that were used during DNS
resolution is particularly useful for clients of forward proxies, in
which the client is requesting to connect to a specific target
hostname using the CONNECT method [HTTP] or UDP proxying
[CONNECT-UDP]. DNS aliases can be used to "cloak" hosts that perform
tracking or malicious activity behind more innocuous hostnames, and
clients such as web browsers use the chain of DNS aliases to
influence behavior like cookie usage policies [COOKIES] or blocking
of malicious hosts.
This document allows clients to receive the chain of DNS aliases for
the next hop by including the list of names in a new next-hop-aliases
Proxy-Status parameter.
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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. next-hop-aliases Parameter
The next-hop-aliases parameter's value is a String that contains one
or more DNS names in a comma-separated list. The items in the list
include all names received in CNAME records [DNS] or AliasMode SVCB
or HTTPS records [SVCB] during the course of resolving the next hop's
hostname using DNS. 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=2001:db8::1
next-hop-aliases="tracker.example.com.,service1.example-cdn.com."
indicates that proxy.example.net, which used the IP address
"2001:db8::1" as the next hop for this request, encountered the
CNAMEs "tracker.example.com." and "service1.example-cdn.com" in the
DNS resolution chain. Note that while this example includes both the
next-hop and next-hop-aliases parameters, next-hop-aliases can be
included without including next-hop.
The next-hop-aliases 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 next-hop-aliases 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.
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4. IANA Considerations
This document registers the "next-hop-aliases" parameter in the "HTTP
Proxy-Status Parameters" registry <https://www.iana.org/assignments/
http-proxy-status>.
Name: next-hop-aliases
Description: A string containing one or more DNS alises used to
establish a proxied connection to the next hop.
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>.
[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-
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ietf-dnsop-svcb-https-11, 11 October 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-
svcb-https-11>.
5.2. Informative References
[COOKIES] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/rfc/rfc6265>.
Author's Address
Tommy Pauly
Apple, Inc.
Email: tpauly@apple.com
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