Internet DRAFT - draft-ietf-dnsop-rfc7958bis
draft-ietf-dnsop-rfc7958bis
Network Working Group J. Abley
Internet-Draft Cloudflare
Obsoletes: 7958 (if approved) J. Schlyter
Intended status: Informational Kirei AB
Expires: 5 September 2024 G. Bailey
Independent
P. Hoffman
ICANN
4 March 2024
DNSSEC Trust Anchor Publication for the Root Zone
draft-ietf-dnsop-rfc7958bis-01
Abstract
The root zone of the Domain Name System (DNS) has been
cryptographically signed using DNS Security Extensions (DNSSEC).
In order to obtain secure answers from the root zone of the DNS using
DNSSEC, a client must configure a suitable trust anchor. This
document describes the format and publication mechanisms IANA uses to
distribute the DNSSEC trust anchors.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-dnsop-rfc7958bis/.
Source for this draft and an issue tracker can be found at
https://github.com/paulehoffman/draft-bash-rfc7958bis.
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
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 5 September 2024.
Copyright Notice
Copyright (c) 2024 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/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Changes from RFC 7958 . . . . . . . . . . . . . . . . . . 4
2. IANA DNSSEC Root Zone Trust Anchor Format and Semantics . . . 4
2.1. XML Syntax . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. XML Semantics . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Converting from XML to DS Records . . . . . . . . . . . . 7
2.4. Converting from XML to DNSKEY Records . . . . . . . . . . 7
2.5. XML Example . . . . . . . . . . . . . . . . . . . . . . . 8
3. Root Zone Trust Anchor Retrieval . . . . . . . . . . . . . . 8
3.1. Retrieving Trust Anchors with HTTPS and HTTP . . . . . . 8
3.2. Accepting DNSSEC Trust Anchors . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Normative References . . . . . . . . . . . . . . . . . . 10
5.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Historical Note . . . . . . . . . . . . . . . . . . 11
Appendix B. Acknowledgemwents . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The Domain Name System (DNS) is described in [RFC1034] and [RFC1035].
DNS Security Extensions (DNSSEC) are described in [RFC9364].
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In the DNSSEC protocol, Resource Record Sets (RRSets) are signed
cryptographically. This means that a response to a query contains
signatures that allow the integrity and authenticity of the RRSet to
be verified. DNSSEC signatures are validated by following a chain of
signatures to a "trust anchor". The reason for trusting a trust
anchor is outside the DNSSEC protocol, but having one or more trust
anchors is required for the DNSSEC protocol to work.
The publication of trust anchors for the root zone of the DNS is an
IANA function performed by ICANN, through its affiliate Public
Technical Identifiers (PTI). A detailed description of corresponding
key management practices can be found in [DPS].
This document describes the formats and distribution methods of
DNSSEC trust anchors that have been used by IANA for the root zone of
the DNS since 2010. Other organizations might have different formats
and mechanisms for distributing DNSSEC trust anchors for the root
zone; however, most operators and software vendors have chosen to
rely on the IANA trust anchors.
The formats and distribution methods described in this document are a
complement to, not a substitute for, the automated DNSSEC trust
anchor update protocol described in [RFC5011]. That protocol allows
for secure in-band succession of trust anchors when trust has already
been established. This document describes one way to establish an
initial trust anchor that can be used by RFC 5011.
1.1. Definitions
The term "trust anchor" is used in many different contexts in the
security community. Many of the common definitions conflict because
they are specific to a specific system, such as just for DNSSEC or
just for S/MIME messages.
In cryptographic systems with hierarchical structure, a trust anchor
is an authoritative entity for which trust is assumed and not
derived. The format of the entity differs in different systems, but
the basic idea, that trust is assumed and not derived, is common to
all the common uses of the term "trust anchor".
The root zone trust anchor formats published by IANA are defined in
Section 2. [RFC4033] defines a trust anchor as "A configured DNSKEY
RR or DS RR hash of a DNSKEY RR". Note that the formats defined here
do not match the definition of "trust anchor" from [RFC4033];
however, a system that wants to convert the trusted material from
IANA into a Delegation Signer (DS) RR can do so.
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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.
1.2. Changes from RFC 7958
This version of the document includes the following changes:
* There is a signficant technical change from erratum 5932
<https://www.rfc-editor.org/errata/eid5932>. This is in the
seventh paragraph of Section 2.2.
* Added the optional public key element.
* Removed the certificates and certificate signing mechanisms.
* Removed the detached OpenPGP signature mechanism.
* The reference to the DNSSEC Practice Statement [DPS] was updated.
* Say explicitly that the XML documents might have XML comments in
them.
2. IANA DNSSEC Root Zone Trust Anchor Format and Semantics
IANA publishes trust anchors for the root zone as an XML document
that contains the hashes of the DNSKEY records and optionally the
keys from the DNSKEY records.
This format and the semantics associated are described in the rest of
this section.
Note that the XML document can have XML comments. For example, IANA
might use these comments to add pointers to important information on
the IANA web site. XML comments are only used as human-readable
commentary, not extensions to the grammar.
The XML document contains a set of hashes for the DNSKEY records that
can be used to validate the root zone. The hashes are consistent
with the defined presentation format of DS resource.
The XML document also can contain the keys from the DNSKEY records.
The keys are consistent with the defined presentation format of
DNSKEY resource.
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Note that the hashes are mandatory in the syntax, but the keys are
optional.
2.1. XML Syntax
A RELAX NG Compact Schema [RELAX-NG] for the documents used to
publish trust anchors is given in Figure 1.
datatypes xsd = "http://www.w3.org/2001/XMLSchema-datatypes"
start = element TrustAnchor {
attribute id { xsd:string },
attribute source { xsd:string },
element Zone { xsd:string },
keydigest+
}
keydigest = element KeyDigest {
attribute id { xsd:string },
attribute validFrom { xsd:dateTime },
attribute validUntil { xsd:dateTime }?,
element KeyTag {
xsd:nonNegativeInteger { maxInclusive = "65535" } },
element Algorithm {
xsd:nonNegativeInteger { maxInclusive = "255" } },
element DigestType {
xsd:nonNegativeInteger { maxInclusive = "255" } },
element Digest { xsd:hexBinary },
element PublicKey { xsd:base64Binary }?
}
Figure 1
2.2. XML Semantics
The TrustAnchor element is the container for all of the trust anchors
in the file.
The id attribute in the TrustAnchor element is an opaque string that
identifies the set of trust anchors. Its value has no particular
semantics. Note that the id element in the TrustAnchor element is
different than the id element in the KeyDigest element, described
below.
The source attribute in the TrustAnchor element gives information
about where to obtain the TrustAnchor container. It is likely to be
a URL and is advisory only.
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The Zone element in the TrustAnchor element states to which DNS zone
this container applies. The root zone is indicated by a single
period (.) character without any quotation marks.
The TrustAnchor element contains one or more KeyDigest elements.
Each KeyDigest element represents the digest of a DNSKEY record in
the zone defined in the Zone element.
The id attribute in the KeyDigest element is an opaque string that
identifies the hash. Note that the id element in the KeyDigest
element is different than the id element in the TrustAnchor element
described above.
The validFrom and validUntil attributes in the KeyDigest element
specify the range of times that the KeyDigest element can be used as
a trust anchor. Note that the validUntil attribute of the KeyDigest
element is optional. If the relying party is using a trust anchor
that has a KeyDigest element that does not have a validUntil
attribute, it can change to a trust anchor with a KeyDigest element
that does have a validUntil attribute, as long as that trust anchor's
validUntil attribute is in the future and the DNSKEY elements of the
KeyDigest are the same as the previous trust anchor. Relying parties
SHOULD NOT use a KeyDigest outside of the time range given in the
validFrom and validUntil attributes.
The KeyTag element in the KeyDigest element contains the key tag for
the DNSKEY record represented in this KeyDigest.
The Algorithm element in the KeyDigest element contains the signing
algorithm identifier for the DNSKEY record represented in this
KeyDigest.
The DigestType element in the KeyDigest element contains the digest
algorithm identifier for the DNSKEY record represented in this
KeyDigest.
The Digest element in the KeyDigest element contains the hexadecimal
representation of the hash for the DNSKEY record represented in this
KeyDigest.
The PublicKey element in the KeyDigest element contains the base64
representation of the public key represented in this KeyDigest. The
PublicKey is optional and is new in this version of the
specification.
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2.3. Converting from XML to DS Records
The display format for the DS record that is the equivalent of a
KeyDigest element can be constructed by marshaling the KeyTag,
Algorithm, DigestType, and Digest elements. For example, assume that
the TrustAnchor element contains:
<?xml version="1.0" encoding="UTF-8"?>
<TrustAnchor
id="AD42165F-3B1A-4778-8F42-D34A1D41FD93"
source="http://data.iana.org/root-anchors/root-anchors.xml">
<Zone>.</Zone>
<KeyDigest id="Kjqmt7v" validFrom="2010-07-15T00:00:00+00:00">
<KeyTag>19036</KeyTag>
<Algorithm>8</Algorithm>
<DigestType>2</DigestType>
<Digest>
49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5
</Digest>
<PublicKey>
AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=
</PublicKey>
</KeyDigest>
</TrustAnchor>
The DS record would be:
. IN DS 19036 8 2
49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5
2.4. Converting from XML to DNSKEY Records
The display format for the DNSKEY record that is the equivalent of a
KeyDigest element can be constructed by marshaling the Algorithm and
PublicKey elements with some constants. For example, assume that the
TrustAnchor element is the same as in Section 2.3. The DNSKEY record
would be:
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. IN DNSKEY 257 3 8
AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=
2.5. XML Example
Figure 2 describes two fictitious trust anchors for the root zone.
<?xml version="1.0" encoding="UTF-8"?>
<!-- Note that these trust anchors are fictitious. -->
<TrustAnchor
id="AD42165F-B099-4778-8F42-D34A1D41FD93"
source="http://data.iana.org/root-anchors/root-anchors.xml">
<Zone>.</Zone>
<KeyDigest id="42"
validFrom="2010-07-01T00:00:00-00:00"
validUntil="2010-08-01T00:00:00-00:00"> <!-- This key
is no longer valid, since validUntil is in the past -->
<KeyTag>34291</KeyTag>
<Algorithm>5</Algorithm>
<DigestType>1</DigestType>
<Digest>c8cb3d7fe518835490af8029c23efbce6b6ef3e2</Digest>
</KeyDigest>
<KeyDigest id="53"
validFrom="2010-08-01T00:00:00-00:00">
<KeyTag>12345</KeyTag>
<Algorithm>5</Algorithm>
<DigestType>1</DigestType>
<Digest>a3cf809dbdbc835716ba22bdc370d2efa50f21c7</Digest>
</KeyDigest>
</TrustAnchor>
Figure 2
3. Root Zone Trust Anchor Retrieval
3.1. Retrieving Trust Anchors with HTTPS and HTTP
Trust anchors are available for retrieval using HTTPS and HTTP.
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In this section, all URLs are given using the "https:" scheme. If
HTTPS cannot be used, replace the "https:" scheme with "http:".
The URL for retrieving the set of hashes in the XML file described in
Section 2 is <https://data.iana.org/root-anchors/root-anchors.xml>.
3.2. Accepting DNSSEC Trust Anchors
A validator operator can choose whether or not to accept the trust
anchors described in this document using whatever policy they want.
In order to help validator operators verify the content and origin of
trust anchors they receive, IANA uses digital signatures that chain
to an ICANN-controlled Certificate Authority (CA) over the trust
anchor data.
It is important to note that the ICANN CA is not a DNSSEC trust
anchor. Instead, it is an optional mechanism for verifying the
content and origin of the XML and certificate trust anchors.
The content and origin of the XML file can be verified using a
digital signature on the file. IANA provides a detached
Cryptographic Message Syntax (CMS) [RFC5652] signature that chains to
the ICANN CA with the XML file. The URL for a detached CMS signature
for the XML file is <https://data.iana.org/root-anchors/root-
anchors.p7s>.
Another method IANA uses to help validator operators verify the
content and origin of trust anchors they receive is to use the
Transport Layer Security (TLS) protocol for distributing the trust
anchors. Currently, the CA used for data.iana.org is well known,
that is, one that is a WebTrust-accredited CA. If a system
retrieving the trust anchors trusts the CA that IANA uses for the
"data.iana.org" web server, HTTPS SHOULD be used instead of HTTP in
order to have assurance of data origin.
4. Security Considerations
This document describes how DNSSEC trust anchors for the root zone of
the DNS are published. Many DNSSEC clients will only configure IANA-
issued trust anchors for the DNS root to perform validation. As a
consequence, reliable publication of trust anchors is important.
This document aims to specify carefully the means by which such trust
anchors are published, with the goal of making it easier for those
trust anchors to be integrated into user environments.
5. References
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5.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/rfc/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/rfc/rfc1035>.
[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>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/rfc/rfc4033>.
[RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC)
Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,
September 2007, <https://www.rfc-editor.org/rfc/rfc5011>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/rfc/rfc5652>.
[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>.
[RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237,
RFC 9364, DOI 10.17487/RFC9364, February 2023,
<https://www.rfc-editor.org/rfc/rfc9364>.
5.2. Informative References
[DPS] Root Zone KSK Operator Policy Management Authority,
"DNSSEC Practice Statement for the Root Zone KSK
Operator", 2020, <https://www.iana.org/dnssec/procedures>.
[RELAX-NG] Clark, J., "RELAX NG Compact Syntax", 2002,
<https://www.oasis-open.org/committees/relax-ng/compact-
20021121.html>.
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Appendix A. Historical Note
The first KSK for use in the root zone of the DNS was generated at a
key ceremony at the ICANN Key Management Facility (KMF) in Culpeper,
Virginia, USA on 2010-06-16. This key entered production during a
second key ceremony held at an ICANN KMF in El Segundo, California,
USA on 2010-07-12. The resulting trust anchor was first published on
2010-07-15.
The second KSK for use in the root zone of the DNS was generated at
key ceremony #27 at the ICANN KMF in Culpeper, Virginia, USA on
2016-10-27. This key entered production during key ceremony #28 held
at the ICANN KMF in El Segundo, California, USA on 2017-02-02. The
resulting trust anchor was first published on 2018-11-11.
More information about the key ceremonies, including full records of
previous ceremonies and plans for future ceremonies, can be found at
<https://www.iana.org/dnssec/ceremonies>.
Appendix B. Acknowledgemwents
Many pioneers paved the way for the deployment of DNSSEC in the root
zone of the DNS, and the authors hereby acknowledge their substantial
collective contribution.
RFC 7958 incorporated suggestions made by Alfred Hoenes and Russ
Housley, whose contributions are appreciated.
Authors' Addresses
Joe Abley
Cloudflare
Amsterdam
Netherlands
Email: jabley@cloudflare.com
Jakob Schlyter
Kirei AB
Email: jakob@kirei.se
Guillaume Bailey
Independent
Email: guillaumebailey@outlook.com
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Paul Hoffman
ICANN
Email: paul.hoffman@icann.org
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