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rfc:rfc7344

Internet Engineering Task Force (IETF) W. Kumari Request for Comments: 7344 Google Category: Informational O. Gudmundsson ISSN: 2070-1721 OGUD Consulting

                                                            G. Barwood
                                                        September 2014
           Automating DNSSEC Delegation Trust Maintenance

Abstract

 This document describes a method to allow DNS Operators to more
 easily update DNSSEC Key Signing Keys using the DNS as a
 communication channel.  The technique described is aimed at
 delegations in which it is currently hard to move information from
 the Child to Parent.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7344.

Copyright Notice

 Copyright (c) 2014 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
 (http://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 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.

Kumari, et al. Informational [Page 1] RFC 7344 Delegation Trust Maintenance September 2014

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   1.2.  Requirements Notation . . . . . . . . . . . . . . . . . .   4
 2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.1.  DNS Delegations . . . . . . . . . . . . . . . . . . . . .   5
   2.2.  Relationship between Parent and Child DNS Operators . . .   5
     2.2.1.  Solution Space  . . . . . . . . . . . . . . . . . . .   6
     2.2.2.  DNSSEC Key Change Process . . . . . . . . . . . . . .   7
 3.  CDS (Child DS) and CDNSKEY (Child DNSKEY) Record Definitions    7
   3.1.  CDS Resource Record Format  . . . . . . . . . . . . . . .   8
   3.2.  CDNSKEY Resource Record Format  . . . . . . . . . . . . .   8
 4.  Automating DS Maintenance with CDS/CDNSKEY Records  . . . . .   8
   4.1.  CDS and CDNSKEY Processing Rules  . . . . . . . . . . . .   9
 5.  CDS/CDNSKEY Publication . . . . . . . . . . . . . . . . . . .   9
 6.  Parent-Side CDS/CDNSKEY Consumption . . . . . . . . . . . . .   9
   6.1.  Detecting a Changed CDS/CDNSKEY . . . . . . . . . . . . .  10
     6.1.1.  CDS/CDNSKEY Polling . . . . . . . . . . . . . . . . .  10
     6.1.2.  Polling Triggers  . . . . . . . . . . . . . . . . . .  11
   6.2.  Using the New CDS/CDNSKEY Records . . . . . . . . . . . .  11
     6.2.1.  Parent Calculates DS  . . . . . . . . . . . . . . . .  12
 7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
 8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  12
 9.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
 10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
 11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
   11.1.  Normative References . . . . . . . . . . . . . . . . . .  15
   11.2.  Informative References . . . . . . . . . . . . . . . . .  15
 Appendix A.  RRR Background . . . . . . . . . . . . . . . . . . .  17
 Appendix B.  CDS Key Rollover Example . . . . . . . . . . . . . .  17

Kumari, et al. Informational [Page 2] RFC 7344 Delegation Trust Maintenance September 2014

1. Introduction

 The first time a DNS Operator signs a zone, they need to communicate
 the keying material to their Parent through some out-of-band method
 to complete the chain of trust.  Depending on the desires of the
 Parent, the Child might send their DNSKEY record, a DS record, or
 both.
 Each time the Child changes the key that is represented in the
 Parent, the updated and/or deleted key information has to be
 communicated to the Parent and published in the Parent's zone.  How
 this information is sent to the Parent depends on the relationship
 the Child has with the Parent.  In many cases this is a manual
 process -- and not an easy one.  For each key change, there may be up
 to two interactions with the Parent.  Any manual process is
 susceptible to mistakes and/or errors.  In addition, due to the
 annoyance factor of the process, Operators may avoid changing keys or
 skip needed steps to publish the new DS at the Parent.
 DNSSEC provides data integrity to information published in DNS; thus,
 DNS publication can be used to automate maintenance of delegation
 information.  This document describes a method to automate
 publication of subsequent DS records after the initial one has been
 published.
 Readers are expected to be familiar with DNSSEC, including [RFC4033],
 [RFC4034], [RFC4035], [RFC5011], and [RFC6781].
 This document outlines a technique in which the Parent periodically
 (or upon request) polls its signed Children and automatically
 publishes new DS records.  To a large extent, the procedures this
 document follows are as described in [RFC6781], Section 4.1.2.
 This technique is designed to be friendly both to fully automated
 tools and humans.  Fully automated tools can perform all the actions
 needed without human intervention and thus can monitor when it is
 safe to move to the next step.
 The solution described in this document only allows transferring
 information about DNSSEC keys (DS and DNSKEY) from the Child to the
 Parental Agent.  It lists exactly what the Parent should publish and
 allows for publication of standby keys.  A different protocol,
 [CPSYNC-DNS], can be used to maintain other important delegation
 information, such as NS and glue records.  These two protocols have
 been kept as separate solutions because the problems are
 fundamentally different and a combined solution is overly complex.

Kumari, et al. Informational [Page 3] RFC 7344 Delegation Trust Maintenance September 2014

 This document describes a method for automating maintenance of the
 delegation trust information and proposes a polled/periodic trigger
 for simplicity.  Some users may prefer a different trigger, for
 example, a button on a web page, a REST interface, or a DNS NOTIFY.
 These alternate additional triggers are not discussed in this
 document.
 This proposal does not include all operations needed for the
 maintenance of DNSSEC key material, specifically the initial
 introduction or complete removal of all keys.  Because of this,
 alternate communications mechanisms must always exist, potentially
 introducing more complexity.

1.1. Terminology

 The terminology we use is defined in this section.  The highlighted
 roles are as follows:
 o  Child: The entity on record that has the delegation of the domain
    from the Parent.
 o  Parent: The domain in which the Child is registered.
 o  Child DNS Operator: The entity that maintains and publishes the
    zone information for the Child DNS.
 o  Parental Agent: The entity that the Child has a relationship with
    to change its delegation information.
 o  Provisioning System: A system that the Operator of the master DNS
    server operates to maintain the information published in the DNS.
    This includes the systems that sign the DNS data.
 o  CDS/CDNSKEY: This notation refers to CDS and/or CDNSKEY, i.e., one
    or both.

1.2. Requirements Notation

 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
 [RFC2119].

Kumari, et al. Informational [Page 4] RFC 7344 Delegation Trust Maintenance September 2014

2. Background

2.1. DNS Delegations

 DNS operation consists of delegations of authority.  For each
 delegation, there are (most of the time) two parties: the Parent and
 the Child.
 The Parent publishes information about the delegations to the Child;
 for the name servers, it publishes an NS [RFC1035] Resource Record
 Set (RRset) that lists a hint for name servers that are authoritative
 for the Child.  The Child also publishes an NS RRset, and this set is
 the authoritative list of name servers to the Child zone.
 The second RRset the Parent sometimes publishes is the DS [RFC4034]
 set.  The DS RRset provides information about the DNSKEY(s) that the
 Child has told the Parent it will use to sign its DNSKEY RRset.  In
 DNSSEC, a trust relationship between zones is provided by the
 following chain:
 Parent DNSKEY --> DS --> Child DNSKEY.
 A prior proposal [AUTO-CPSYNC] suggested that the Child send an
 "update" to the Parent via a mechanism similar to DNS UPDATE.  The
 main issue became: how does the Child find the actual Parental Agent/
 server to send the update to?  While that could have been solved via
 technical means, it failed to reach consensus.  There is also a
 similar proposal in [PARENT-ZONES].
 As the DS record can only be present at the Parent [RFC4034], some
 other method is needed to automate which DNSKEYs are picked to be
 represented in the Parent zone's DS records.  One possibility is to
 use flags in the DNSKEY record.  If the Secure Entry Point (SEP) bit
 is set, this indicates that the DNSKEY is intended for use as a
 secure entry point.  This DNSKEY signs the DNSKEY RRset, and the
 Parental Agent can calculate DS records based on that.  But this
 fails to meet some operating needs, including the Child having no
 influence on what DS digest algorithms are used and DS records that
 can only be published for keys that are in the DNSKEY RRset; thus,
 this technique would not be compatible with Double-DS rollover
 [RFC6781].

2.2. Relationship between Parent and Child DNS Operators

 In practical application, there are many different relationships
 between the Parent and Child DNS Operators.  The type of relationship
 affects how the Child DNS Operator communicates with the Parent.

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 This section will highlight some of the different situations but is
 by no means a complete list.
 Different communication paths:
 o  Direct/API: The Child can change the delegation information via
    automated/scripted means.  The Extensible Provisioning Protocol
    (EPP) [RFC5730], used by many Top-Level Domains (TLDs), is an
    example of this.  Other examples are web-based programmatic
    interfaces that Registrars make available to their Resellers.
 o  User Interface: The Child uses a web site set up by the Parental
    Agent for updating delegation information.
 o  Indirect: The communication has to be transmitted via an out-of-
    band mechanism between two parties, such as by email or telephone.
    This is common when the Child DNS Operator is neither the Child
    itself nor the Registrar for the domain, but a third party.
 o  Multi-step Combinations: The information flows through an
    intermediary.  It is possible, but unlikely, that all the steps
    are automated via APIs and there are no humans involved.
 A domain name holder (Child) may operate its own DNS servers or
 outsource the operation.  While we use the word "Parent" as singular,
 a Parent can consist of a single entity or a composite of many
 discrete parts that have rules and roles.  We refer to the entity
 that the Child corresponds with as the Parent.
 An organization (such as an enterprise) may delegate parts of its
 name-space to be operated by a group that is not the same as that
 which operates the organization's DNS servers.  In some of these
 cases, the flow of information is handled either in an ad hoc manner
 or via some corporate mechanism; this can range from email to a fully
 automated operation.

2.2.1. Solution Space

 This document is aimed at the cases in which there is a separation
 between the Child and Parent.
 A further complication is when the Child DNS Operator is not the
 Child.  There are two common cases of this:
 a)  The Parental Agent (e.g., Registrar) handles the DNS operation.
 b)  A third party takes care of the DNS operation.

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 If the Parental Agent is the DNS Operator, life is much easier; the
 Parental Agent can inject any delegation changes directly into the
 Parent's provisioning system.  The techniques described below are not
 needed in the case when the Parental Agent is the DNS Operator.
 In the case of a third-party DNS Operator, the Child either needs to
 relay changes in DNS delegation or give the Child DNS Operator access
 to its delegation/registration account.
 Some Parents want the Child to express their DNSKEYs in the form of
 DS records, while others want to receive the DNSKEY records and
 calculate the DS records themselves.  There is no consensus on which
 method is better; both have good reasons to exist.  This solution is
 DS vs. DNSKEY agnostic and allows operation with either.

2.2.2. DNSSEC Key Change Process

 After a Child DNS Operator first signs the zone, there is a need to
 interact with the Parent, for example, via a delegation account
 interface to upload or paste in the zone's DS information.  This
 action of logging in through the delegation account user interface
 authenticates that the user is authorized to change delegation
 information for the Child published in the Parent zone.  In the case
 where the Child DNS Operator does not have access to the registration
 account, the Child needs to perform the action.
 At a later date, the Child DNS Operator may want to publish a new DS
 record in the Parent, either because they are changing keys or
 because they want to publish a standby key.  This involves performing
 the same process as before.  Furthermore, when this is a manual
 process with cut and paste, operational mistakes will happen -- or
 worse, the update action will not be performed at all.
 The Child DNS Operator may also introduce new keys and can do so when
 old keys exist and can be used.  The Child may also remove old keys,
 but this document does not support removing all keys.  This is to
 avoid making signed zones unsigned.  The Child may not enroll the
 initial key or introduce a new key when there are no old keys that
 can be used (without some additional out-of-band validation of the
 keys) because there is no way to validate the information.

3. CDS (Child DS) and CDNSKEY (Child DNSKEY) Record Definitions

 This document specifies two new DNS resource records, CDS and
 CDNSKEY.  These records are used to convey, from one zone to its
 Parent, the desired contents of the zone's DS resource record set
 residing in the Parent zone.

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 The CDS and CDNSKEY resource records are published in the Child zone
 and give the Child control of what is published for it in the
 parental zone.  The Child can publish these manually, or they can be
 automatically maintained by DNS provisioning tools.  The CDS/CDNSKEY
 RRset expresses what the Child would like the DS RRset to look like
 after the change; it is a "replace" operation, and it is up to the
 software that consumes the records to translate that into the
 appropriate add/delete operations in the provisioning systems (and in
 the case of CDNSKEY, to generate the DS from the DNSKEY).  If neither
 CDS nor CDNSKEY RRset is present in the Child, this means that no
 change is needed.

3.1. CDS Resource Record Format

 The wire and presentation format of the Child DS (CDS) resource
 record is identical to the DS record [RFC4034].  IANA has allocated
 RR code 59 for the CDS resource record via Expert Review
 [DNS-TRANSPORT].  The CDS RR uses the same registries as DS for its
 fields.
 No special processing is performed by authoritative servers or by
 resolvers, when serving or resolving.  For all practical purposes,
 CDS is a regular RR type.

3.2. CDNSKEY Resource Record Format

 The wire and presentation format of the CDNSKEY ("Child DNSKEY")
 resource record is identical to the DNSKEY record.  IANA has
 allocated RR code 60 for the CDNSKEY resource record via Expert
 Review.  The CDNSKEY RR uses the same registries as DNSKEY for its
 fields.
 No special processing is performed by authoritative servers or by
 resolvers, when serving or resolving.  For all practical purposes,
 CDNSKEY is a regular RR type.

4. Automating DS Maintenance with CDS/CDNSKEY Records

 CDS/CDNSKEY resource records are intended to be "consumed" by
 delegation trust maintainers.  The use of CDS/CDNSKEY is OPTIONAL.
 If the Child publishes either the CDS or the CDNSKEY resource record,
 it SHOULD publish both.  If the Child knows which the Parent
 consumes, it MAY choose to only publish that record type (for
 example, some Children wish the Parent to publish a DS, but they wish
 to keep the DNSKEY "hidden" until needed).  If the Child publishes
 both, the two RRsets MUST match in content.

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4.1. CDS and CDNSKEY Processing Rules

 If there is neither CDS nor CDNSKEY RRset in the Child, this signals
 that no change should be made to the current DS set.  This means
 that, once the Child and Parent are in sync, the Child DNS Operator
 MAY remove all CDS and CDNSKEY resource records from the zone.  The
 Child DNS Operator may choose to do this to decrease the size of the
 zone or to decrease the workload for the Parent (if the Parent
 receives no CDS/CDNSKEY records, it can go back to sleep).  If it
 does receive a CDS or CDNSKEY RRset, it needs to check them against
 what is currently published (see Section 5).
 The following acceptance rules are placed on the CDS and CDNSKEY
 resource records as follows:
 o  Location: MUST be at the Child zone apex.
 o  Signer: MUST be signed with a key that is represented in both the
    current DNSKEY and DS RRsets, unless the Parent uses the CDS or
    CDNSKEY RRset for initial enrollment; in that case, the Parent
    validates the CDS/CDNSKEY through some other means (see
    Section 6.1 and the Security Considerations).
 o  Continuity: MUST NOT break the current delegation if applied to DS
    RRset.
 If any these conditions fail, the CDS or CDNSKEY resource record MUST
 be ignored, and this error SHOULD be logged.

5. CDS/CDNSKEY Publication

 The Child DNS Operator publishes CDS/CDNSKEY RRset(s).  In order to
 be valid, the CDS/CDNSKEY RRset(s) MUST be compliant with the rules
 in Section 4.1.  When the Parent DS is in sync with the CDS/CDNSKEY
 RRset(s), the Child DNS Operator MAY delete the CDS/CDNSKEY RRset(s);
 the Child can determine if this is the case by querying for DS
 records in the Parent.

6. Parent-Side CDS/CDNSKEY Consumption

 The CDS/CDNSKEY RRset(s) SHOULD be used by the Parental Agent to
 update the DS RRset in the Parent zone.  The Parental Agent for this
 uses a tool that understands the CDS/CDNSKEY signing rules in
 Section 4.1, so it might not be able to use a standard validator.

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 The Parent MUST choose to use either CDNSKEY or CDS resource records
 as its default updating mechanism.  The Parent MAY only accept either
 CDNSKEY or CDS, but it MAY also accept both so it can use the other
 in the absence of the default updating mechanism; it MUST NOT expect
 there to be both.

6.1. Detecting a Changed CDS/CDNSKEY

 How the Parental Agent gets the CDS/CDNSKEY RRset may differ.  Below
 are two examples of how this can take place.
 Polling:  The Parental Agent operates a tool that periodically checks
       each of the Children that has a DS record to see if there is a
       CDS or CDNSKEY RRset.
 Pushing:  The delegation user interface has a button {Fetch DS} that,
       when pushed, performs the CDS/CDNSKEY processing.  If the
       Parent zone does not contain DS for this delegation, then the
       "push" SHOULD be ignored.  If the Parental Agent displays the
       contents of the CDS/CDNSKEY to the user and gets confirmation
       that this represents their key, the Parental Agent MAY use this
       for initial enrollment (when the Parent zone does not contain
       the DS for this delegation).
 In either case, the Parental Agent MAY apply additional rules that
 defer the acceptance of a CDS/CDNSKEY change.  These rules may
 include a condition that the CDS/CDNSKEY remains in place and valid
 for some time period before it is accepted.  It may be appropriate in
 the "Pushing" case to assume that the Child is ready and thus accept
 changes without delay.

6.1.1. CDS/CDNSKEY Polling

 This is the only defined use of CDS/CDNSKEY resource records in this
 document.  There are limits to the scalability of polling techniques;
 thus, some other mechanism is likely to be specified later that
 addresses CDS/CDNSKEY resource record usage in the situation where
 polling runs into scaling issues.  Having said that, polling will
 work in many important cases such as enterprises, universities, and
 smaller TLDs.  In many regulatory environments, the Registry is
 prohibited from talking to the Registrant.  In most of these cases,
 the Registrant has a business relationship with the Registrar, so the
 Registrar can offer this as a service.
 If the CDS/CDNSKEY RRset(s) do not exist, the Parental Agent MUST
 take no action.  Specifically, it MUST NOT delete or alter the
 existing DS RRset.

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6.1.2. Polling Triggers

 It is assumed that other mechanisms will be implemented to trigger
 the Parent to look for an updated CDS/CDNSKEY RRset.  As the CDS/
 CDNSKEY resource records are validated with DNSSEC, these mechanisms
 can be unauthenticated.  As an example, a Child could telephone its
 Parent and request that it process the new CDS or CDNSKEY resource
 records, or an unauthenticated POST could be made to a web server
 (with rate-limiting).
 Other documents can specify the trigger conditions.

6.2. Using the New CDS/CDNSKEY Records

 Regardless of how the Parental Agent detected changes to a CDS/
 CDNSKEY RRset, the Parental Agent SHOULD use a DNSSEC validator to
 obtain a validated CDS/CDNSKEY RRset from the Child zone.  A NOT
 RECOMMENDED exception to this is if the Parent performs some
 additional validation on the data to confirm that it is the "correct"
 key.
 The Parental Agent MUST ensure that previous versions of the CDS/
 CDNSKEY RRset do not overwrite more recent versions.  This MAY be
 accomplished by checking that the signature inception in the Resource
 Record Signature (RRSIG) for CDS/CDNSKEY RRset is later and/or that
 the serial number on the Child's Start of Authority (SOA) is greater.
 This may require the Parental Agent to maintain some state
 information.
 The Parental Agent MAY take extra security measures.  For example, to
 mitigate the possibility that a Child's Key Signing Key (KSK) has
 been compromised, the Parental Agent may inform (by email or other
 methods) the Child DNS Operator of the change.  However, the precise
 out-of-band measures that a Parent zone takes are outside the scope
 of this document.
 Once the Parental Agent has obtained a valid CDS/CDNSKEY RRset it
 MUST check the publication rules from Section 4.1.  In particular,
 the Parental Agent MUST check the Continuity rule and do its best not
 to invalidate the Child zone.  Once checked, if the information in
 the CDS/CDNSKEY and DS differ, it may apply the changes to the Parent
 zone.  If the Parent consumes CDNSKEY, the Parent should calculate
 the DS before doing this comparison.

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6.2.1. Parent Calculates DS

 There are cases where the Parent wants to calculate the DS record due
 to policy reasons.  In this case, the Child publishes CDNSKEY
 records, and the Parent calculates the DS records on behalf of the
 Children.
 When a Parent operates in "calculate DS" mode, it can operate in one
 of two sub-modes:
 full:  The Parent only publishes DS records it calculates from DNSKEY
    records.
 augment:  The Parent will make sure there are DS records for the
    digest algorithm(s) it requires(s).
 In the case where the Parent fetches the CDNSKEY RRset and calculates
 the DS, the resulting DS can differ from the CDS published by the
 Child.  It is expected that the differences are only due to the
 different set of digest algorithms used.

7. IANA Considerations

 IANA has assigned RR Type code 59 for the CDS resource record.  This
 was done for a draft version whose content was later incorporated
 into this document [DNS-TRANSPORT].  This document is the reference
 for CDS RRtype.
 IANA has assigned an RR Type for the CDNSKEY as described below:
 Type:  CDNSKEY
 Value:  60
 Meaning:  DNSKEY(s) the Child wants reflected in DS
 Reference:  This document

8. Privacy Considerations

 All of the information handled or transmitted by this protocol is
 public information published in the DNS.

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9. Security Considerations

 This work is for the normal case; when things go wrong there is only
 so much that automation can fix.
 If the Child breaks DNSSEC validation by removing all the DNSKEYs
 that are represented in the DS set, its only repair actions are to
 contact the Parent or restore the DNSKEYs in the DS set.
 In the event of a compromise of the server or system generating
 signatures for a zone, an attacker might be able to generate and
 publish new CDS/CDNSKEY resource records.  The modified CDS/CDNSKEY
 records will be picked up by this technique and may allow the
 attacker to extend the effective time of his attack.  If there is a
 delay in accepting changes to DS, as in [RFC5011], then the attacker
 needs to hope his activity is not detected before the DS in the
 Parent is changed.  If this type of change takes place, the Child
 needs to contact the Parent (possibly via a Registrar web interface)
 and remove any compromised DS keys.
 A compromise of the account with the Parent (e.g., Registrar) will
 not be mitigated by this technique, as the "new Registrant" can
 delete or modify the DS records at will.
 While it may be tempting, the techniques specified in this document
 SHOULD NOT be used for initial enrollment of keys since there is no
 way to ensure that the initial key is the correct one.  If it is
 used, strict rules for inclusion of keys -- such as hold-down times,
 challenge data inclusion, or similar -- MUST be used along with some
 kind of challenge mechanism.  A Child cannot use this mechanism to go
 from signed to unsigned (publishing an empty CDS/CDNSKEY RRset means
 no change should be made in the Parent).
 The CDS RR type should allow for enhanced security by simplifying the
 process.  Since key change is automated, updating a DS RRset by other
 means may be regarded as unusual and subject to extra security
 checks.
 As this introduces a new mechanism to update information in the
 Parent, it MUST be clear who is fetching the records and creating the
 appropriate records in the Parent zone.  Specifically, some
 operations may use mechanisms other than what is described here.  For
 example, a Registrar may assume that it is maintaining the DNSSEC key
 information in the Registry and may have this cached.  If the
 Registry is fetching the CDS/CDNSKEY RRset, then the Registry and
 Registrar may have different views of the DNSSEC key material; the

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 result of such a situation is unclear.  Therefore, this mechanism
 SHOULD NOT be used to bypass intermediaries that might cache
 information and, because of that, get the wrong state.
 If there is a failure in applying changes in the Child zone to all
 DNS servers listed in either Parent or Child NS set, it is possible
 that the Parental Agent may get confused either because it gets
 different answers on different checks or CDS RR validation fails.  In
 the worst case, the Parental Agent performs an action reversing a
 prior action after the Child signing system decides to take the next
 step in the key change process, resulting in a broken delegation.
 DNS is a loosely coherent distributed database with local caching;
 therefore, it is important to allow old information to expire from
 caches before deleting DS or DNSKEY records.  Similarly, it is
 important to allow new records to propagate through the DNS before
 use (see [RFC6781]).
 It is common practice for users to outsource their DNS hosting to a
 third-party DNS provider.  In order for that provider to be able to
 maintain the DNSSEC information, some users give the provider their
 Registrar login credentials (which obviously has negative security
 implications).  Deploying the solution described in this document
 allows third-party DNS providers to maintain the DNSSEC information
 without Registrants giving their Registrar credentials, thereby
 improving security.
 By automating the maintenance of the DNSSEC key information (and
 removing humans from the process), we expect to decrease the number
 of DNSSEC related outages, which should increase DNSSEC deployment.

10. Acknowledgements

 We would like to thank a large number of folk, including Mark
 Andrews, Joe Abley, Jaap Akkerhuis, Roy Arends, Doug Barton, Brian
 Dickson, Paul Ebersman, Tony Finch, Jim Galvin, Paul Hoffman, Samir
 Hussain, Tatuya Jinmei, Olaf Kolkman, Stephan Lagerholm, Cricket Liu,
 Matt Larson, Marco Sanz, Antoin Verschuren, Suzanne Woolf, Paul
 Wouters, John Dickinson, Timothe Litt, and Edward Lewis.
 Special thanks to Wes Hardaker for contributing significant text and
 creating the complementary (CSYNC) solution, and to Patrik Faltstrom,
 Paul Hoffman, Matthijs Mekking, Mukund Sivaraman, and Jeremy C. Reed
 for text and in-depth review.  Brian Carpenter provided a good
 Gen-ART review.
 There were a number of other folk with whom we discussed this
 document; apologies for not remembering everyone.

Kumari, et al. Informational [Page 14] RFC 7344 Delegation Trust Maintenance September 2014

11. References

11.1. Normative References

 [RFC1035]  Mockapetris, P., "Domain names - implementation and
            specification", STD 13, RFC 1035, November 1987.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
            Rose, "DNS Security Introduction and Requirements", RFC
            4033, March 2005.
 [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
            Rose, "Resource Records for the DNS Security Extensions",
            RFC 4034, March 2005.
 [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
            Rose, "Protocol Modifications for the DNS Security
            Extensions", RFC 4035, March 2005.
 [RFC5011]  StJohns, M., "Automated Updates of DNS Security (DNSSEC)
            Trust Anchors", STD 74, RFC 5011, September 2007.
 [RFC6781]  Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
            Operational Practices, Version 2", RFC 6781, December
            2012.

11.2. Informative References

 [AUTO-CPSYNC]
            Mekking, W., "Automated (DNSSEC) Child Parent
            Synchronization using DNS UPDATE", Work in Progress,
            December 2010.
 [CPSYNC-DNS]
            Hardaker, W., "Child To Parent Synchronization in DNS",
            Work in Progress, July 2014.
 [DNS-TRANSPORT]
            Barwood, G., "DNS Transport", Work in Progress, June 2011.
 [PARENT-ZONES]
            Andrews, M., "Updating Parent Zones", Work in Progress,
            November 2013.

Kumari, et al. Informational [Page 15] RFC 7344 Delegation Trust Maintenance September 2014

 [RFC5730]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
            STD 69, RFC 5730, August 2009.
 [RFC5910]  Gould, J. and S. Hollenbeck, "Domain Name System (DNS)
            Security Extensions Mapping for the Extensible
            Provisioning Protocol (EPP)", RFC 5910, May 2010.

Kumari, et al. Informational [Page 16] RFC 7344 Delegation Trust Maintenance September 2014

Appendix A. RRR Background

 RRR is our shorthand for the Registry/Registrar/Registrant model of
 Parent-Child relationships.
 In the RRR world, the different parties are frequently from different
 organizations.  In the single enterprise world, there are also
 organizational, geographical, and cultural separations that affect
 how information flows from a Child to the Parent.
 Due to the complexity of the different roles and interconnections,
 automation of delegation information has not yet occurred.  There
 have been proposals to automate this, in order to improve the
 reliability of the DNS.  These proposals have not gained enough
 traction to become standards.
 For example, in many of the TLD cases, there is the RRR model
 (Registry/Registrar/Registrant).  The Registry operates DNS for the
 TLD, and the Registrars accept registrations and place information
 into the Registry's database.  The Registrant only communicates with
 the Registrar; frequently, the Registry is not allowed to communicate
 with the Registrant.  In that case, as far as the Registrant is
 concerned, the Registrar is the same entity as the Parent.
 In many RRR cases, the Registrar and Registry communicate via EPP
 [RFC5730] and use the EPP DNSSEC extension [RFC5910].  In a number of
 Country Code TLDs (ccTLDs), there are other mechanisms in use as well
 as EPP, but in general, there seems to be a movement towards EPP
 usage when DNSSEC is enabled in the TLD.

Appendix B. CDS Key Rollover Example

 This section shows an example on how CDS is used when performing a
 KSK rollover.  This example will demonstrate the Double-DS rollover
 method from Section 4.1.2 of [RFC6781].  Other rollovers using
 CDNSKEY and double KSK are left as an exercise to the reader.  The
 table below does not reflect the Zone Signing Keys (ZSKs) as they do
 not matter during KSK rollovers.  The wait steps highlight what RRset
 needs to expire from caches before progressing to the next step.

Kumari, et al. Informational [Page 17] RFC 7344 Delegation Trust Maintenance September 2014

 +------+---------------+---------+---------+--------------+---------+
 | Step | State         |  Parent |  Child  |  DNSKEY and  |  Child  |
 |      |               |    DS   |   KSK   |  CDS signer  |   CDS   |
 +------+---------------+---------+---------+--------------+---------+
 |      | Beginning     |    A    |    A    |      A       |         |
 | 1    | Add CDS       |    A    |    A    |      A       |    AB   |
 | Wait | for DS change |    A    |    A    |      A       |    AB   |
 | 2    | Updated DS    |    AB   |    A    |      A       |    AB   |
 | Wait | > DS TTL      |    AB   |    A    |      A       |    AB   |
 | 3    | Actual        |    AB   |    B    |      B       |    AB   |
 |      | Rollover      |         |         |              |         |
 | Wait | > DNSKEY TTL  |    AB   |    B    |      B       |    AB   |
 | 4    | Child Cleanup |    AB   |    B    |      B       |    B    |
 | 5    | Parent cleans |    B    |    B    |      B       |    B    |
 | 6    | Optional CDS  |    B    |    B    |      B       |         |
 |      | delete        |         |         |              |         |
 +------+---------------+---------+---------+--------------+---------+
                            Table 1: States

Authors' Addresses

 Warren Kumari
 Google
 1600 Amphitheatre Parkway
 Mountain View, CA  94043
 US
 EMail: warren@kumari.net
 Olafur Gudmundsson
 OGUD Consulting
 3821 Village Park Dr.
 Chevy Chase, MD  20815
 US
 EMail: ogud@ogud.com
 George Barwood
 33 Sandpiper Close
 Gloucester  GL2 4LZ
 United Kingdom
 EMail: george.barwood@blueyonder.co.uk

Kumari, et al. Informational [Page 18]

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