DNS Resolver Information
draft-reddy-add-resolver-info-00
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Tirumaleswar Reddy.K , Mohamed Boucadair | ||
| Last updated | 2021-03-29 | ||
| Stream | (None) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
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| Send notices to | (None) |
draft-reddy-add-resolver-info-00
ADD WG T. Reddy
Internet-Draft McAfee
Intended status: Standards Track M. Boucadair
Expires: September 29, 2021 Orange
March 28, 2021
DNS Resolver Information
draft-reddy-add-resolver-info-00
Abstract
This document describes methods for DNS resolvers to publish
information about themselves. Applications and operating systems can
use the resolver information to identify the capabilities of the
resolver.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on September 29, 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Retrieving Resolver Information . . . . . . . . . . . . . . . 3
4. Format of the Resolver Information . . . . . . . . . . . . . 3
5. Resolver Information . . . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7.1. RESINFO RRtype . . . . . . . . . . . . . . . . . . . . . 5
7.2. DNS Resolver Information Registration . . . . . . . . . . 5
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Historically, DNS stub resolvers typically communicated with the
recursive resolvers without needing to know anything about the
features of the recursive resolvers. More recently, recursive
resolvers have different features that may help the stub resolvers
identify the capabilities of the resolver. Thus stub resolvers can
discover and authenticate encrypted DNS servers provided by a local
network, for example using the techniques proposed in [I-D.ietf-add-
dnr] and [I-D.ietf-add-ddr]. Thus stub resolvers need a way to get
information from the discovered recursive resolvers about its
capabilities.
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 the recursive resolvers. The information
that a resolver might want to give is defined in Section 5.
2. Terminology
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.
This document makes use of the terms defined in [RFC8499] and
[I-D.ietf-dnsop-terminology-ter].
'Encrypted DNS' refers to a DNS protocol that provides an encrypted
channel between a DNS client and server (e.g., DoT, DoH, or DoQ).
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3. Retrieving Resolver Information
A stub resolver that wants to get information about a resolver can
use the RRtype "RESINFO" defined in this document, and the IANA
assignment is given in Section 7.1. The contents of the RDATA in the
response to this query are defined in Section 5. If the resolver
understands the RESINFO RRtype, the RRset in the Answer section MUST
have exactly one record.
The client can retrieve the resolver information using the RESINFO
RRtype and QNAME of the domain name that is used to authenticate the
DNS server (referred to as ADN in [I-D.ietf-add-dnr]). If the
special use domain name "resolver.arpa" defined in [I-D.ietf-add-ddr]
is used to discover the Encrypted DNS server, the client can first
retrieve a CNAME that aliases `_dns.resolver.arpa` to
`_dns.$HOSTNAME` and then retrieve the resolver information using the
RESINFO RRtype and QNAME of the `$HOSTNAME`.
4. Format of the Resolver Information
The resolver information is returned as a JSON object. The JSON
object MUST use the I-JSON message format defined in [RFC7493]. Note
that [RFC7493] was based on [RFC7159], but [RFC7159] was replaced by
[RFC8259]. Requiring the use of I-JSON instead of more general JSON
format greatly increases the likelihood of interoperability.
The names in this object are defined in an IANA registry. The JSON
object returned by a DNS 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 7.2 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. 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.
5. Resolver Information
The resolver information includes the following attributes:
qnameminimization: If the DNS server supports QNAME minimisation
[RFC7816] to improve DNS privacy, the parameter value is set to
true. This is a mandatory attribute.
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extendeddnserror: If the DNS server supports extended DNS error
(EDE) [RFC8914] to return additional information about the cause
of DNS errors, the parameter lists the possible extended DNS error
codes that can be returned by the DNS server. This is an optional
attribute.
* Note that the extended error code "Blocked" defined in
Section 4.16 of [RFC8914] identifies access to domains is
blocked due to an policy by the operator of the DNS server,
extended error code "Censored" defined in Section 4.17 of
[RFC8914] identifies access to domains is blocked based on a
requirement from an external entity and the extended error code
"Filtered" defined in Section 4.18 of [RFC8914] identifies
access to domains is blocked based on the request from the
client to blacklist domains.
clientauth: If the DNS server requires client authentication, the
parameter value is set to true. For example, when not on the
enterprise network (e.g., at home or coffee shop) yet needing to
access the enterprise Encrypted DNS server, roaming users can use
client authentication to access the Enterprise provided Encrypted
DNS server. This is an optional attribute.
resinfourl: A URL that points to the generic unstructured resolver
information (e.g., DoH APIs supported, possible HTTP status codes
returned by the DoH server, how to report a problem, etc.) for
troubleshooting purpose. This is an optional attribute.
identityurl: A URL that points to a human-friendly description of
the resolver identity to display to the end-user.
Figure 1 shows an example of resolver information.
{
"qnameminimization":true,
"extendeddnserror": [15, 16, 17],
"clientauth": false,
"resinfourl": "https://resolver.example.com/guide",
"identityurl": "https://resolver.example.com/user-friendly-name"
}
Figure 1: An Example of Resolver Information
As specified in [RFC7493], the I-JSON object is encoded as UTF8.
[RFC7493] explicitly allows the returned objects to be in any order.
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6. Security Considerations
Unless a DNS request to retrieve the resolver information is sent
over DNS-over-TLS (DoT) [RFC7858] or DNS-over- HTTPS (DoH) [RFC8484],
the response is susceptible to forgery. The DNS resolver information
can be retrieved after the encrypted connection is established to the
DNS server. If the client wishes to retrieve the resolver
information before the encryption connection is established to the
DNS resolver, the client MUST use local DNSSEC validation.
7. IANA Considerations
7.1. 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
Meaning: Resolver Information as an I-JSON
7.2. DNS Resolver Information Registration
IANA will create a new registry titled "DNS Resolver Information"
that will contain definitions of the names that can be used to
provide the resolver information. The registration procedure is by
Specification Required, as defined in [RFC8126]. 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 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.
IANA will add the names "resinfourl", "identityurl",
"extendeddnserror" and "qnameminimization" to the DNS Resolver
Information registry.
8. Acknowledgments
This specification leverages the work that has been done in
[I-D.pp-add-resinfo]. Thanks to Tommy Jensen, Vittorio Bertola,
Vinny Parla, Chris Box, Ben Schwartz and Shashank Jain for the
discussion and comments.
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9. References
9.1. 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>.
[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>.
[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>.
[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>.
[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>.
9.2. Informative References
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-02 (work in
progress), August 2020.
[I-D.pp-add-resinfo]
Sood, P. and P. Hoffman, "DNS Resolver Information Self-
publication", draft-pp-add-resinfo-02 (work in progress),
June 2020.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
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[RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve
Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016,
<https://www.rfc-editor.org/info/rfc7816>.
[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>.
[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>.
[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018,
<https://www.rfc-editor.org/info/rfc8310>.
[RFC8914] Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", RFC 8914,
DOI 10.17487/RFC8914, October 2020,
<https://www.rfc-editor.org/info/rfc8914>.
Authors' Addresses
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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