Internet DRAFT - draft-proxied-svcb-headers
draft-proxied-svcb-headers
Network Working Group T. Pauly
Internet-Draft Apple, Inc.
Intended status: Standards Track 19 February 2021
Expires: 23 August 2021
HTTP Header Fields for Proxied SVCB Metadata
draft-proxied-svcb-headers-00
Abstract
This document defines HTTP header fields for the passing Service
Binding (SVCB) DNS metadata in HTTP responses.
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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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. SVCB Request Header Field . . . . . . . . . . . . . . . . . . 3
3. SVCB Response Header Fields . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. HTTP Headers . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
CONNECT [RFC7231] and CONNECT-UDP [I-D.ietf-masque-connect-udp] are
HTTP methods that clients may use to establish TCP or UDP flows to
target servers. Once proxy servers establish these flows, proxy
servers treat allocated flows as opaque byte or datagram streams
respectively. Clients specify the target in authority-form
(Section 5.3 of [RFC7230]), including the name or IP address of the
server along with a port number. When using a name instead of an IP
address, the proxy server locally resolves the name to an IPv4 or
IPv6 address with A or AAAA queries. The client does not see these A
or AAAA answers, as they are only relevant to the proxy in
establishing a connection to the target.
In some circumstances, some DNS metadata may be useful to clients.
This is especially true for information contained in Service Binding
(SVCB or HTTPS) records [I-D.ietf-dnsop-svcb-https]. These records
can influence client behavior even when clients are not directly
interacting with target IP addresses. The records can be used to
determine which application-level protocols are supported by an
endpoint. These records also can include a TLS Encrypted Client
Hello [I-D.ietf-tls-esni] configuration, which can be used in
protecting the end-to-end TLS handshake.
This document specifies HTTP header fields that proxy servers may use
to relay information retrieved from SVCB records from proxy servers
to clients when using CONNECT or CONNECT-UDP.
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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. SVCB Request Header Field
Clients can request SVCB parameters with the Structured Header
[RFC8941] "DNS-SVCB-Keys". Its value MUST be an sf-list whose
members are sf-integer items that MUST NOT contain parameters. Its
ABNF is:
DNS-SVCB-Keys = sf-list
Each list member corresponds to the numeric version of an
SvcParamKey.
For example, a client wanting to receive ALPN and ECH Config
parameters would send a request for 1 (alpn) and 5 (echconfig):
HEADERS
:method = CONNECT
:authority = svc.example.com:443
dns-svcb-keys = 1, 5
3. SVCB Response Header Fields
A proxy server that receives a request with "DNS-SVCB-Keys" MAY
respond with the Structured Header "DNS-SVCB-Params" response header
fields. The value of "DNS-SVCB-Params" MUST be an sf-list whose
members are sf-string, each of which MUST contain parameters.
DNS-SVCB-Params = sf-list
Each list member is an sf-string that represents the TargetName of a
single received SVCB or HTTPS record. The Parameters associated with
each list member correspond to the SvcParam key-value pairs for that
record, the priority of the record, and the TTL of the record.
The priority of the record MUST be a parameter with the key
"priority", and a value as an sf-integer. Alias forms, with priority
0, MUST NOT be included.
The TTL of the record MUST be a parameter with the key "ttl", and a
value as an sf-integer.
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Each SvcParam that matches a key requested by the client is a
parameters with a key that is the character "p" followed by the
numeric version of the SvcParamKey. For example, the ALPN
SvcParamKey, with the numeric value 1, would have a parameter key
"p1". The value of each parameter MUST be an sf-binary item that
contains the bytes of the SvcParamValue.
Proxy servers MUST NOT include the "DNS-SVCB-Params" response header
field if the corresponding request did not include a "DNS-SVCB-Keys".
Servers MAY include specific SvcParamKey values that were not
requested. Specifically, servers SHOULD include the "mandatory"
parameter if present, which would be presented as "p0", along with
any parameters that are defined as mandatory for that record.
As an example, assume that the server received the following
"svc.example.com" SVCB records:
svc.example.com. 3600 IN HTTPS 1 svc2.example.com. alpn=h2,h3 echconfig="123..."
svc.example.com. 3600 IN HTTPS 2 . alpn=h2 echconfig="abc..."
A successful CONNECT response would include the following headers, if
the client requested both "alpn" and "echconfig":
HEADERS
:method = CONNECT
:status = 200
dns-svcb-params = "svc2.example.com.";priority=1;ttl=3600;p1=:aDIsaDM=:;p5=:MTIzLi4u:,
"svc.example.com.";priority=2;ttl=3600;p1=:aDI=:;p5=:YWJjLi4u:
4. IANA Considerations
4.1. HTTP Headers
This document registers the "DNS-SVCB-Keys" and "DNS-SVCB-Params",
headers in the "Permanent Message Header Field Names"
<https://www.iana.org/assignments/message-headers>.
+----------------------+----------+--------+---------------+
| Header Field Name | Protocol | Status | Reference |
+----------------------+----------+--------+---------------+
| DNS-SVCB-Keys | http | exp | This document |
+----------------------+----------+--------+---------------+
| DNS-SVCB-Params | http | exp | This document |
+----------------------+----------+--------+---------------+
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5. Security Considerations
The "DNS-SVCB-Params" header in Section 3 does not include any DNSSEC
information. Clients that depend on the contents of the SVCB record
being DNSSEC-validated MUST NOT use this metadata without otherwise
fetching the record and its corresponding RRSIG record and locally
verifying its contents.
6. Normative References
[I-D.ietf-dnsop-svcb-https]
Schwartz, B., 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-02, 2 November 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-dnsop-
svcb-https-02.txt>.
[I-D.ietf-masque-connect-udp]
Schinazi, D., "The CONNECT-UDP HTTP Method", Work in
Progress, Internet-Draft, draft-ietf-masque-connect-udp-
03, 5 January 2021, <http://www.ietf.org/internet-drafts/
draft-ietf-masque-connect-udp-03.txt>.
[I-D.ietf-tls-esni]
Rescorla, E., Oku, K., Sullivan, N., and C. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-09, 16 December 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-tls-esni-
09.txt>.
[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>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
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[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>.
Author's Address
Tommy Pauly
Apple, Inc.
Email: tpauly@apple.com
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