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Automating DNSSEC Delegation Trust Maintenance

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7344.
Authors Warren "Ace" Kumari , Ólafur Guðmundsson , George Barwood
Last updated 2017-03-11 (Latest revision 2014-06-10)
Replaces draft-kumari-ogud-dnsop-cds
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Tim Wicinski
Shepherd write-up Show Last changed 2014-05-05
IESG IESG state Became RFC 7344 (Proposed Standard)
Action Holders
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Joel Jaeggli
Send notices to (None)
IANA IANA review state IANA OK - Actions Needed
IANA action state RFC-Ed-Ack
dnsop                                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Informational                            O. Gudmundsson
Expires: December 12, 2014                                 Shinkuro Inc.
                                                              G. Barwood

                                                           June 10, 2014

             Automating DNSSEC Delegation Trust Maintenance


   This document describes a method to allow DNS operators to more
   easily update DNSSEC Key Signing Keys using the DNS as 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 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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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 12, 2014.

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
   ( 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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Requirements Notation . . . . . . . . . . . . . . . . . .   4
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  DNS Delegations . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Relationship Between Parent and Child DNS Operator  . . .   5
       2.2.1.  Solution Space  . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  DNSSEC key change process . . . . . . . . . . . . . .   6
   3.  CDS / CDNSKEY (Child DS / 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 / CDNSKEY Processing Rules  . . . . . . . . . . . . .   8
   5.  CDS / CDNSKEY Publication . . . . . . . . . . . . . . . . . .   9
   6.  Parent Side CDS / CDNSKEY Consumption . . . . . . . . . . . .   9
     6.1.  Detecting a Changed CDS / CDNSKEY . . . . . . . . . . . .   9
       6.1.1.  CDS / CDNSKEY Polling . . . . . . . . . . . . . . . .  10
       6.1.2.  Polling Triggers  . . . . . . . . . . . . . . . . . .  10
     6.2.  Using the New CDS / CDNSKEY Records . . . . . . . . . . .  11
       6.2.1.  Parent Calculates DS  . . . . . . . . . . . . . . . .  11
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  12
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     11.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  RRR background . . . . . . . . . . . . . . . . . . .  15
   Appendix B.  CDS key rollover example . . . . . . . . . . . . . .  16
   Appendix C.  Changes / Author Notes.  . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

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

   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

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   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

   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 stand-by keys.  A different protocol,
   [I-D.csync], can be used to maintain other important delegation
   information, such as NS and glue.  These two protocols have been kept
   as separate solutions because the problems are fundamentally
   different, and a combined solution is overly complex.

   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 webpage, a REST interface or a DNS NOTIFY.
   These alternate / additional triggers are not discussed in this

   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.

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1.1.  Terminology

   The terminology we use is defined in this section.

   Highlighted roles:

   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 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"

1.2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in

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] RRset that lists a
   hint for name servers that are authoritative for the child.  The
   child also publishes a 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 trust relationship between zones is provided by the following

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   parent DNSKEY --> DS --> child DNSKEY.

   A prior proposal [] suggested that the child send an
   "update" to the parent via a mechanism similar to Dynamic 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 [I-D.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 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 what DS
   digest algorithms are used and DS records can only be published for
   keys that are in the DNSKEY RRset, and thus this technique would not
   be compatible with Double-DS ( [RFC6781] ) key rollover.

2.2.  Relationship Between Parent and Child DNS Operator

   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.
   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.  EPP[RFC5730], used by many 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 out-of-band
      between two parties, such as by email or telephone.  This is
      common when the Child's 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 API's and there are no humans involved.

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   A domain name holder (Child) may operate its own DNS servers or
   outsource the operation.  While we use the word parent as a singular,
   parent can consist of 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 in either an ad hoc manner
   or via some corporate mechanism; this can range from email to 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.

   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 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 / 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

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   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 stand-by 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 is not 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 / CDNSKEY (Child DS / 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.

   The CDS / CDNSKEY resource records are published in the child zone
   and gives 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 no CDS
   / CDNSKEY RRset is present in child, this means that no change is

   [[RFC Editor: Please remove this paragraph before publication]
   Version -04 of the ID that became this working group document
   ( defined
   a new record (CTA) that could hold either a DS or a DNSKEY record
   (with a selector to differentiate between them).  In a shocking
   development, there was almost full consensus that this was horrid :-)

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3.1.  CDS Resource Record Format

   The wire and presentation format of the CDS ("Child DS") resource
   record is identical to the DS record [RFC4034].  IANA has allocated
   RR code 59 for the CDS resource record via expert review
   [I-D.ds-publish].  The CDS RR uses the same registries as DS for its

   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 TBA1 for the CDNSKEY resource record via expert
   review.  The CDNSKEY RR uses the same registries as DNSKEY for its

   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.

4.1.  CDS / CDNSKEY Processing Rules

   If there are no CDS / 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.

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   Following acceptance rules are placed on the CDS / CDNSKEY resource
   records as follows:

   o  Location: the CDS / CDNSKEY resource records 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 /
      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

   If any these conditions fail the CDS / CDNSKEY resource record MUST
   be ignored, and this error SHOULD be logged.

5.  CDS / CDNSKEY Publication

   The Child DNS Operator publishes CDS and / or CDNSKEY resource
   records.  In order to be valid, the CDS / CDNSKEY RRset MUST be
   compliant with the rules in Section 4.1.  When the Parent DS is "in
   sync" with the CDS / CDNSKEY resource records, the Child DNS Operator
   MAY delete the CDS / CDNSKEY record(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 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 from
   Section 4.1 so it might not be able to use a standard validator.

   The parent MUST choose to use either CDNSKEY or CDS resource records
   as their 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, but 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 as 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.

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   Pushing  The delegation user interface has a button {Fetch DS} 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 / CDSNKEY 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 does not scale to.  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, and so the
   registrar can offer this as a service.

   If the CDS / CDNSKEY RRset does not exist, the Parental Agent MUST
   take no action.  Specifically it MUST NOT delete or alter the
   existing DS RRset.

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 RRsets.  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 they process the new CDS or CDNSKEY resource
   records or an unauthenticated POST could be made to a webserver (with

   Other documents can specify the trigger conditions.

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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"

   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 RRSIG
   for CDS / CDNSKEY RRset is later and / or the serial number on the
   child's 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 has been
   compromised, the Parental Agent may, for example, 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 and 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.

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:  it only publishes DS records it calculates from DNSKEY

   augment:  it 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

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   child.  It is expected that the differences are only due 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 an earlier version of this document[I-D.ds-publish] This
   document is to become the reference for CDS RRtype.

   IANA is requested to assign an RR Type for the CDNSKEY, see below

   Type:  CDNSKEY

   Value:  TBD1 (60 suggested)

   Meaning:  DNSKEY(s) the child wants reflected in DS

   Reference:  This document

8.  Privacy Considerations

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

9.  Security Considerations

   This work is for the normal case; when things go wrong there is only
   so much that automation can fix.

   If 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 so 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 /
   modify the DS records at will.

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   While it may be tempting, this 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 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

   The CDS RR type should allow for enhanced security by simplifying
   process.  Since key change is automated, updating a DS RRset by other
   means may be regarded as unusual and subject to extra security

   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 other mechanisms 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 and the
   result of such a situation is unclear.  Therefore, this mechanism
   SHOULD NOT be use 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 but after the child signing system decides to take the
   next step in the key change process, resulting in a broken

   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 the 3rd party DNS provider to maintain the DNSSEC information

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   without giving them the registrar credentials, thereby improving

   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 Carpender provided a good Gen-
   Art review.

   There were a number of other folk with whom we discussed this,
   apologies for not remembering everyone.

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.

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   [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

11.2.  Informative References

              Mekking, W., "Automated (DNSSEC) Child Parent
              Synchronization using DNS UPDATE", draft-mekking-dnsop-
              auto-cpsync-01 (work in progress), December 2010.

              Hardaker, W., "Child To Parent Synchronization in DNS",
              draft-hardaker-dnsop-csync-02 (work in progress), July

              Barwood, G., "DNS Transport", draft-barwood-dnsop-ds-
              publish-02 (work in progress), June 2011.

              Andrews, M., "Updating Parent Zones", draft-andrews-dnsop-
              update-parent-zones-04 (work in progress), November 2013.

   [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.

Appendix A.  RRR background

   RRR is our shorthand for Registry/Registrar/Registrant model of
   parent child relationship.

   In the RRR world, the different parties are frequently from different
   organizations.  In the single enterprise world there are also
   organizational / geographical / 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

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   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 and Registrant).  The Registry operates DNS for
   the TLD, the Registrars accept registrations and place information
   into the Registries 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 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 the double DS
   rollover method from section 4.1.2 in [RFC6781].  Other rollovers
   using CDNSKEY and double KSK are left as an exercise to the reader.
   The table below does not reflect the ZSK keys they just do not matter
   during KSK rollovers.  The wait states below highlight what RRset
   needs to expire from caches before progressing to the next step.

   | 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

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Appendix C.  Changes / Author Notes.

   [RFC Editor: Please remove this section before publication ]

   WG-13 to WG-14 IETF Last call and IESG processing

   o  Applied text fixes from Phil Pennock

   o  Addressed comments from Brian Carpender GEN-ART review.

   o  Barry Leiba wanted better IANA considerations and suggested some
      text changes in 6.1 and 6.2.1

   o  Reformatted the Appendix B table to be clearer.

   WG-12 to WG-13

   o  Added appendix B showing Key rollover using CDS.

   WG-11 to WG-12

   o  Many nits and helpful grammar fixes from Jeremy C.  Reed.

   WG-10 to WG-11

   o  More useful text from Matthijs.

   o  Explained why the child might want to remove the CDS / CDNSKEY

   WG-09 to WG-10

   o  Incorporated off list comments from Stephan Lagerholm.  Largest
      change is fixing discrepancy between parent MAY perform OOB
      validation and the Signer rule in 4.1.  Clarified by updating
      signer rule to allow enrolment if validation is performed OOB.

   WG-08 to WG-09

   o  New text from Paul Hoffman for the first paragraph of the intro.

   o  And a modification from Jaap.

   WG-07 to WG-08

   o  Incorporated text from Antoin Verschuren at the end of Section 6.

   o  Comments from Paul Hoffman and Tim W

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   WG-06 to WG-07

   o  Incorporated nits / editorial comments from Tim Wicinski.


      *  Reference for Mark's draft was incorrect, Wes Hardaker doesn't
         work for ISC :-P

      *  Normalized CDS record / CDS resource record / records / etc.

      *  Language cleanup / nits / poor grammar.

      *  removed "punted" colloquialism.

   WG-05 to WG-06

   o  Consensus (according to me!) was that mail thread said "Child MAY
      remove the CDS record".  Changed to accommodate.

   o  "The proposal below can operate with both models, but the child
      needs to be aware of the parental policies." - removed "but the
      child needs to be aware of the parental policies.".  This is no
      longer true, as we suggest publishing both CDS and CDSNKEY.

   o  Added: "without some additional out of band process" to "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."

   o  Added a bit to the IANA section, requesting that TBA1 be replaced
      with the IANA allocated code.

   o  Removed: "Some parents prefer to accept DNSSEC key information in
      DS format, some parents prefer to accept it in DNSKEY format, and
      calculate the DS record on the child's behalf.  Each method has
      pros and cons, both technical and policy.  This solution is DS vs
      DNSKEY agnostic, and allows operation with either." from Section 4
      as it is covered in Section 2.2.1

   o  Remove a bunch of comments from the XML.  I was getting tired of
      scrolling past them.  If the authors need them back, they are in
      SVN commit 47.

   WG-04 to WG-05

   o  More comments from Patrik, Paul and Ed.

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   o  Many nits and fixes from Matthijs Mekking.

   o  Outstanding question: Should we remove the "Child SHOULD remove
      the CDS record" text?  Mail sent to list.

   WG-03 to WG-04

   o  Large number of comments and changes from Patrik.

   WG-02 to WG-03

   o  Fixed some references to RFC 5011 - from Samir Hussain.

   o  Fixed some spelling / typos - from Samir Hussain.

   o  A number of clarifications on the meaning on an empty / non-
      existant CDS RRset - thanks to JINMEI, Tatuya

   o  Be consistent in mentioning both CDS and CDNSKEY throughout the

   WG-01 to WG-02

   o  Many nits and suggestions from Mukund.

   o  Matthijs: " I still think that it is too strong that the Child DNS
      Operator SHOULD/MUST delete the CDS RRset when the Parent DS is
      "in sync".  This should be a MAY"

   WG-00 to WG-01

   o  Addressed Vancouver: "Paul Hoffmann: NOT ready for WGLC.  None of
      the 2 documents explain why there is a split between the two
      strategies."  Thanks to Paul for providing text.

   From -05 to WG-00:

   o  Nothing changed, resubmit under new name.

   From 04 to 05

   o  Renamed the record back to CDS.

   From 03 to 04.

   o  Added text explaining that CDS and CSYNC complement each other,
      not replace or compete.

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   o  Changed format of record to be <selector> <data> to allow the
      publication of DS **or** DNSKEY.

   o  Bunch of text changed to cover the above.

   o  Added a bit more text on the polling scaling stuff, expectation
      that other triggers will be documented.

   From 02 to 03

   o  Applied comments by Matthijs Mekking

   o  Incorporated suggestions from Edward Lewis about structure

   o  Reworked structure to be easier for implementors to follow

   o  Applied many suggestions from a wonderful thorough review by John

   o  Removed the going Unsigned option

   From 01 to 02

   o  Major restructuring to facilitate easier discussion

   o  Lots of comments from DNSOP mailing list incorporated, including
      making draft DNSKEY/DS neutral, explain different relationships
      that exists,

   o  added more people to acks.

   o  added description of enterprise situations

   o  Unified on using Parental Agent over Parental Representative

   o  Removed redundant text when possible

   o  Added text to explain what can go wrong if not all child DNS
      servers are in sync.

   o  Reference prior work by Matthijs Mekking

   o  Added text when parent calculates DS from DNSKEY

   From - to -1.

   o  Removed from section .1: "If a child zone has gone unsigned, i.e.
      no DNSKEY and no RRSIG in the zone, the parental representative

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      MAY treat that as intent to go unsigned.  (NEEDS DISCUSSION)."
      Added new text at end. -- suggestion by Scott Rose 20/Feb/13.

   o  Added some background on the different DNS Delegation operating
      situations and how they affect interaction of parties.  This moved
      some blocks of text from later sections into here.

   o  Number of textual improvements from Stephan Lagerholm

   o  Added motivation why CDS is needed in CDS definition section

   o  Unified terminology in the document.

   o  Much more background

Authors' Addresses

   Warren Kumari
   1600 Amphitheatre Parkway
   Mountain View, CA  94043


   Olafur Gudmundsson
   Shinkuro Inc.
   4922 Fairmont Av, Suite 250
   Bethesda, MD  20814


   George Barwood
   33 Sandpiper Close
   Gloucester  GL2 4LZ
   United Kingdom


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