Internet DRAFT - draft-pp-add-resinfo
draft-pp-add-resinfo
Network Working Group P. Sood
Internet-Draft Google
Intended status: Standards Track P. Hoffman
Expires: December 29, 2020 ICANN
June 27, 2020
DNS Resolver Information Self-publication
draft-pp-add-resinfo-02
Abstract
This document describes methods for DNS resolvers to self-publish
information about themselves. The information is returned as a JSON
object. The names in this object are defined in an IANA registry
that allows for light-weight registration. Applications and
operating systems can use the methods defined here to get the
information from resolvers in order to make choices about how to send
future queries to those resolvers.
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 December 29, 2020.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
2. Retrieving Resolver Information by DNS . . . . . . . . . . . 3
3. Contents of the Returned I-JSON Object . . . . . . . . . . . 4
3.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. RESINFO RRtype . . . . . . . . . . . . . . . . . . . . . 4
4.2. Registry for DNS Resolver Information . . . . . . . . . . 5
4.3. resolver-info.arpa Special-Use Domain Name . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Ideas From Earlier Work that was Abandoned . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Historically, DNS stub resolvers typically communicated with the
recursive resolvers in their configuration without needing to know
anything about the features of the recursive resolvers. More
recently, recursive resolvers have different features that may cause
stub resolvers to make choices about which configured resolver from
its configuration to use, and also how to communicate with the
recursive resolver (such as over different transports). Thus stub
resolvers need a way to get information from recursive resolvers
about features that might affect the communication.
This document specifies a method for stub resolvers to ask recursive
resolvers for such information. In short, a new RRtype is defined
for stub resolvers to query using the DNS to a special-use domain
name.
The response from this method is a JSON object. The JSON object MUST
use the I-JSON message format defined in [RFC7493]. Note that
[RFC7493] was based on RFC 7159, but RFC 7159 was replaced by
[RFC8259]. Requiring the use of I-JSON instead of more general JSON
format greatly increases the likelihood of interoperability.
The information that a resolver might want to give to a recursive
resolver is not defined in this document; instead other documents
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will follow that will specify that information and the format that it
comes in.
In nearly every common scenario today, a DNS stub resolver gets the
IP addresses of the recursive resolvers that it will use in an
insecure fashion, such as from DHCP. Because these addresses were
obtained insecurely, the protocol specified here does not try to use
authenticated communication. If, in the future, more stub resolvers
get the addresses of their recursive resolvers in a secure fashion,
this protocol can be enhanced to include authenticated ways of
getting information from the resolver.
1.1. Definitions
In the rest of this document, the term "resolver" without
qualification means "recursive resolver" as defined in [RFC8499].
Also, the term "stub" is used to mean "stub resolver".
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. Retrieving Resolver Information by DNS
A stub that wants to use the DNS to get information about a resolver
can use the DNS query defined here. The query a stub resolver uses
is resolver-info.arpa/IN/RESINFO. The RRtype "RESINFO" is defined in
this document, and the IANA assignment is given in Section 4.1. The
contents of the Rdata in the response to this query is defined in
Section 3. If the resolver understands the RESINFO RRtype, the RRset
in the Answer section MUST have exactly one record.
The name resolver-info.arpa is defined in this document, and the IANA
assignment is given in Section 4.3. As described in Section 4.3, the
zone resolver-info.arpa is not actually delegated and never will be.
The resolver that receives this query acts as if it is delegated, and
responds with its own RESINFO data in the Answer section.
A resolver that receives a query with the RRtype of RESINFO with a
QNAME of resolver-info.arpa acts as if it is delegated, and responds
with its own RESINFO data in the Answer section.
A resolver MAY be configured to respond to queries for the RESINFO
RRtype on names other than resolver-info.arpa. For example, a
resolver might be known to some of its clients by both an IP address
and a few domain names, and be configured to be authoritative for
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those names. For all names other than resolver-info.arpa or names
that the resolver is configured to be authoritative for, a query for
the RESINFO RRtype is meaningless and MUST result in a NODATA or
NXDOMAIN response.
3. Contents of the Returned I-JSON Object
The JSON object returned by a DNS query or an HTTPS query MAY contain
any name/value pairs.
All names in the returned object MUST either be defined in the IANA
registry or, if for local use only, begin with the substring "temp-".
The IANA registry (Section 4.2) will never register names that begin
with "temp-".
All names MUST consist only of lower-case ASCII characters, digits,
and hyphens (that is, Unicode characters U+0061 through 007A, U+0030
through U+0039, and U+002D), and MUST be 63 characters or shorter.
As defined in Section 4.2, the IANA registry will not register names
that begin with "temp-", so these names can be used freely by any
implementer.
Note that the message returned by the resolver MUST be in I-JSON
format. I-JSON requires that the message MUST be encoded in UTF8.
3.1. Example
The I-JSON object that a resolver returns might look like the
following:
{
"temp-field2": 42
}
As specified in [RFC7493], the I-JSON object is encoded as UTF8.
[RFC7493] explicitly allows the returned objects to be in any order.
4. IANA Considerations
4.1. RESINFO RRtype
This document defines a new DNS RR type, RESINFO, whose value TBD
will be allocated by IANA from the "Resource Record (RR) TYPEs" sub-
registry of the "Domain Name System (DNS) Parameters" registry:
Type: RESINFO
Value: TBD
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Meaning: Information self-published by a resolver as an I-JSON (RFC
7493) object
Reference: This document
4.2. Registry for DNS Resolver Information
IANA will create a new registry titled "DNS Resolver Information"
that will contain definitions of the names that can be used with the
protocols defined in this document. The registration procedure is by
Expert Review and Specification Required, as defined in [RFC8126].
The specification that is required for registration can be either an
Internet-Draft or an RFC. The reviewer for this registry is
instructed to generally be liberal in what they accept into the
registry: as long as the specification that comes with the
registration request is reasonably understandable, the registration
should be accepted.
The registry has the following fields for each element:
Name: The name to be used in the JSON object. This name MUST NOT
begin with "temp-". This name MUST conform to the definition of
"string" in I-JSON [RFC7493] message format.
Value type: The type of data to be used in the JSON object.
Specification: The name of the specification for the registered
element.
4.3. resolver-info.arpa Special-Use Domain Name
IANA will record the domain name "resolver-info.arpa" in the
"Special-Use Domain Names" registry [SUDN]. IANA MUST NOT delegate
resolver-info.arpa in the .arpa zone.
5. Security Considerations
Unless a DNS request for resolver-info.arpa/IN/RESINFO as described
in Section 2 is sent over DNS-over-TLS (DoT) [RFC7858] or DNS-over-
HTTPS (DoH) [RFC8484], the response is susceptible to forgery. Given
that one of the first expected uses for the protocol in this document
is to find out whether DoT or DoH is available for the resolver, it
is thus expected that most if not all such DNS requests will be sent
without any chance of authentication. Stubs and resolvers SHOULD use
normal DNS methods for avoiding forgery such as query ID
randomization and source port randomization.
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6. References
6.1. Normative References
[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>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/info/rfc7493>.
[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>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[SUDN] "Special-Use Domain Names", n.d.,
<https://www.iana.org/assignments/
special-use-domain-names/>.
6.2. Informative References
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
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Appendix A. Ideas From Earlier Work that was Abandoned
This document is based on work done earlier in the DNSOP working
group, and personal drafts before that.
In that earlier work, "<reverse-ip>.{in-addr,ip6}.arpa" was proposed
as the domain name to allow for the possibility of DNSSEC-signed
responses. However, it was pointed out that people often do not
control their reverse IP names and thus their ISP (or their ISP's
ISP) could spoof responses and make them look legitimate by signing
with DNSSEC.
In an earlier version of this draft, a second way to get the resolver
information was specified: using a query to a well-known URI over
HTTPS, possibly with authentication. Many participants in the ADD
Working Group in early 2020 disagreed with specifying this transport
because the IP address being used was most likely obtained by the
stub resolver in an insecure fashion, so using an authenticated
method could lead to inappropriate assumptions about the security of
the answer.
Acknowledgments
The idea of various types of servers publishing information about
themselves has been around for decades. However this idea has not
been used in the DNS. This document aims to fix this omission.
Roy Arends contributed many ideas to an earlier version of this draft
before it was moved to the ADD working group.
Authors' Addresses
Puneet Sood
Google
Email: puneets@google.com
Paul Hoffman
ICANN
Email: paul.hoffman@icann.org
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