dnsop                                                     O. Gudmundsson
Internet-Draft                                                CloudFlare
Intended status: Standards Track                              P. Wouters
Expires: December 12, 2016 May 4, 2017                                             Red Hat
                                                           June 10,
                                                        October 31, 2016

            Managing DS records from parent via CDS/CDNSKEY
                    draft-ietf-dnsop-maintain-ds-03
                    draft-ietf-dnsop-maintain-ds-04

Abstract

   RFC7344 specifies how DNS trust can be partially maintained across key
   rollovers in-band between parent and child.  There are two features missing in that
   specification:  This document elevates
   RFC7344 from informational to standards track and adds a standard
   track method for initial trust setup and removal of trust anchor.  This
   document addresses both these omissions. secure entry
   point.

   Changing a domain's DNSSEC status can be a complicated matter
   involving multiple unrelated parties.  Some of these parties, such as
   the DNS operator, might not even be known by all the organizations
   involved.  The inability to disable DNSSEC via in-band signalling signaling is
   seen as a problem or liability that prevents some DNSSEC adoption at
   large scale.  This document adds a method for in-band signalling signaling of
   these DNSSEC status changes.

   Initial trust

   This document describes reasonable policies to ease deployment of the
   initial acceptance of new secure entry points (DS records)

   It is preferable that operators collaborate on the transfer or move
   of a domain.  The best method is considered in general to be perform a hard technical
   problem, Key Signing Key ("KSK")
   plus Zone Signing Key ("ZSK") rollover.  If that is not possible, the
   method using an unsigned intermediate state described in this
   document sets forth reasonable policies that clarify can be used to move the domain between two parties.  This
   leaves the domain temporarily unsigned and simplify vulnerable to DNS
   spoofing, but that is preferred over the initial acceptance policy. alternative of validation
   failures due to a mismatched DS and DNSKEY record.

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
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   This Internet-Draft will expire on December 12, 2016. May 4, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2   3
     1.1.  Introducing a DS record . . . . . . . . . . . . . . . . .   3
     1.2.  Removing a DS Record  . . . . . . . . . . . . . . . . . .   3
     1.3.  Notation  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.4.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  The Three Uses of CDS . . . . . . . . . . . . . . . . . . . .   4
     2.1.  The meaning of the CDS RRset  . . . . . . . . . . . . . .   5
   3.  Enabling DNSSEC via CDS/CDNSKEY . . . . . . . . . . . . . . .   5
     3.1.  Accept policy via authenticated channel . . . . . . . . .   5   6
     3.2.  Accept with extra checks  . . . . . . . . . . . . . . . .   5   6
     3.3.  Accept after delay  . . . . . . . . . . . . . . . . . . .   6
     3.4.  Accept with challenge . . . . . . . . . . . . . . . . . .   6
     3.5.  Accept from inception . . . . . . . . . . . . . . . . . .   7
   4.  DNSSEC Delete Algorithm . . . . . . . . . . . . . . . . . . .   6   7
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   7   8
   6.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   7   8
     6.1.  Promoting RFC7344 to standards track  . . . . . . . . . .   8   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8   9
   Appendix A.  Acknowledgements  Acknowledgments  . . . . . . . . . . . . . . . . . .   8   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8   9

1.  Introduction

   CDS/CDNSKEY [RFC7344] records are used to signal changes in trust
   anchors. secure
   entry points.  This is one method to maintain delegations that can be
   used when the DNS operator has no other way to inform the parent that
   changes are needed.  This document elevates [RFC7344] from
   informational to standards track RFC.

   In addition, [RFC7344] is lacking two different options for full
   automated operation to be possible.  Firstly it  It did not define a method for
   the Initial Trust establishment and left establishment, leaving it open to each parent to
   come up with an acceptance policy.  Secondly it  Additionally, [RFC7344] did not
   provide a "delete" signal for the child to tell inform the parent that it wants to remove the
   DNSSEC security for its domain. domain must be removed.

1.1.  Introducing a DS record

   The big issue is how a child domain instructs

   Automated insertion of DS records has been limited for many zones by
   the parent requirement that it
   wants to have a DS record added.  This problem can be solved using all changes pass through a
   few simplifying assumptions.  This document makes "registry" of the assumption that
   there are reasonable policies that can be applied and will allow
   automation
   child zone's parent.  This has significantly hindered deployment of trust introduction.

   Not being able to enable trust via an easily automated mechanism is
   hindering
   DNSSEC at large scale for DNS hosters that do not have automated
   access to the "registry" of hosters, as the child zone's parent. zone owner is
   often not aware or able to update DNS records such as the DS record.

   This document describes a few possible methods for the parent to
   accept a request by the child to add a DS record to its zone.  These
   methods have different security properties that addresses different
   deployment scenarios, all resulting in an automated method of trust
   introduction.

1.2.  Removing a DS Record

   This document introduces the delete option for both CDS and CDNSKEY,
   allowing a child to signal to the parent to turn off DNSSEC.  When a
   domain is moved from one DNS operator to another one, another, sometimes it is
   necessary to turn off DNSSEC to facilitate the change of DNS
   operator.  Common scenarios include:

   1  alternative  Alternative to doing a proper DNSSEC algorithm rollover due to
      operational limitations such as software limitations.

   2  moving  Moving from a DNSSEC operator to a non-DNSSEC capable operator.

   3  moving  Moving to an operator that cannot/does-not-want to do a proper
      DNSSEC rollover.

   4  when  When moving between two DNS operators that use disjoint sets of
      algorithms to sign the zone, thus an algorithm rollover can not be
      performed.

   5  the  The domain holder no longer wants DNSSEC enabled.

   The lack of a "remove my DNSSEC" option is cited as a reason why some
   operators cannot deploy DNSSEC, as this is seen as an operational
   risk.

   Turning off DNSSEC reduces the security of the domain and thus should
   only be done carefully, and that decision SHOULD should be fully under the
   child domain's control.

1.3.  Notation

   When this document uses the word

   Signaling can happen via CDS it implies that the same applies
   to or CDNSKEY and vice verse. records.  The only
   differences between the two records is how information is
   represented, and who calculates the DS
   digiest.

   We use RRR digest.  For clarity, this
   document uses the term "CDS" throughout the document to mean Registry Registrar Registrant in the context of
   DNS domain markets. "either
   CDS or CDNSKEY".

   When the document uses the word "parent" it implies an entity that is
   authorized to insert DS records into the parent zone on behalf of the
   child domain.  Which entity this exactly is does not matter.  It
   could be the Registrar or Reseller that the child domain was
   purchased from.  It could be the Registry that the domain is
   registered in when allowed.  It  Or it could be some other entity when the
   RRR framework is not used. entity.

1.4.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  The Three Uses of CDS

   In general there are three operations that a domain wants to
   influence on its parent: instruct
   their parent to perform:

   1  Enable DNSSEC validation, i.e. place an initial DS RRset in the
      parent.

   2  Roll over KSK, the Key Signing Key ("KSK"), this means updating the DS
      records in the parent to reflect the new set of KSK's at the
      child.  This could be an ADD operation, a DELETE operation on one
      or more records while keeping at least one DS RR, or a full
      REPLACE operation.

   3  Turn off DNSSEC validation, i.e. delete all the DS records.

   Operation 2

   Rolling the KSK is covered in [RFC7344], operations 1 [RFC7344].  It is considered the safest
   use case of a CDS/CDNSKEY record as it makes no change to the trust
   relationship between parent and 3 child.  Introduction and removal of
   DS records are defined in this document.  In many people's minds, those two operations carry
   more risk than  As these CDS/CDNSKEY use
   cases create or end the first one.  This document argues that 3 is
   identical to 2 and trust relationship between the first one is different (but not that
   different). parent and
   child, these use cases should be carefully implemented and monitored.

2.1.  The meaning of the CDS RRset

   The semantic meaning of publishing a CDS RRset is interpreted to
   mean:

   "Publishing a CDS or CDNSKEY record signals to the parent that the
   child desires that the corresponding DS records be synchronized.
   Every parent or parental agent should have an acceptance policy of
   these records for the three different use cases involved: Initial DS
   publication, Key rollover, and Returning to Insecure."

   In short, the CDS RRset is an instruction to the parent to modify the
   DS RRset if the CDS and DS Reset's differ.

   The acceptance policy for CDS in the rollover case is "seeing"
   according to [RFC7344].  The acceptance policy in the Delete case is
   seeing a (validly signed) CDS RRset with the delete operation
   specified in this document.

3.  Enabling DNSSEC via CDS/CDNSKEY

   There are number of different models for managing initial trust, but
   in the general case, the child wants to enable global validation for
   the future.  Thus during the period from the time validation.  As
   long as the child publishes
   the CDS until the corresponding DS is published at the parent is the
   period that insecure, DNS answers for the child could can be forged.  The goal
   is to keep this promote the child from insecure to secure as soon as reasonably
   possible by the parent.  This means that the period from the child's
   publication of CDS/CDNSKEY RRset to the parent publishing the
   synchronized DS RRset should be as short as possible.

   One important use case is how a third party DNS operator can upload
   its DNSSEC information to the parent, so the parent can publish a DS
   record for the child.  In this case there is a possibility of setting
   up some kind of authentication mechanism and submission mechanism
   that is outside the scope of this document.

   Below are some policies that parents can use.  These policies assume
   that the notifications can be verified or authenticated.

3.1.  Accept policy via authenticated channel

   In this case the parent is notified via authenticated channel UI/API
   that a CDS/CDNSKEY RRset exists.  In the case of a CDS RRset the
   parent retrieves the CDS RRset and inserts the corresponding DS RRset
   as requested.  In the case of CDNSKEY the parent retrieves the
   CDNSKEY RRset and calculates the DS record(s).

3.2.  Accept with extra checks

   In this case  Parents may limit the parent checks
   DS record type based on local policy.  Parents SHOULD NOT refuse CDS/
   CDNSKEY updates that do not (yet) have a matching DNSKEY in the child
   zone.  This will allow the child to prepublish a spare (and
   potentially offline) DNSKEY.

3.2.  Accept with extra checks

   In this case the parent checks that the source of the notification is
   allowed to request the DS insertion.  The checks could include
   whether this is a trusted entity, whether the nameservers correspond
   to the requester, whether there have been any changes in registration
   in the last few days, etc.  The parent can also send a notification
   requesting a confirmation, for example by sending email to the
   registrant requesting a confirmation.  The end result is that the CDS
   RRset is accepted at the end of the checks or when the out-of-band
   confirmation is received.  Any extra checks should have proper rate
   limiting in place to prevent abuse.

3.3.  Accept after delay

   In this case, if the parent deems the request valid, it starts
   monitoring the CDS RRset at the child nameservers over period of time
   to make sure nothing changes.  After some time or after a number of
   checks, preferably from different vantage points in the network, the
   parent accepts the CDS RRset as a valid signal to update its DS RRset
   for this child.

3.4.  Accept with challenge

   In this case the parent instructs the requester to insert some record
   into the child domain to prove it has the ability to do so (i.e., it
   is the operator of the zone).

4.  DNSSEC Delete Algorithm  This method imposes a new task on the
   parent to monitor the child zone to see if the challenge has been
   added to the zone.  The DNSKEY algorithm registry contains two reserved values: 0 parent should verify the challenge is
   published by all the child's nameservers and
   255[RFC4034].  The CERT record [RFC4398] defines should test for this
   challenge from various diverse network locations to increase the value 0
   security of this method as much as possible.

3.5.  Accept from inception

   If a parent is adding a new child domain that is not currently
   delegated at all, it could use the child CDS/CDNSKEY RRset to mean
   immediately publish a DS RRset along with the algorithm in new NS RRset.  This
   would ensure that the CERT record new child domain is not defined never active in DNSSEC.

   For this reason, using an insecure
   state.

4.  DNSSEC Delete Algorithm

   This document defines the previously reserved DNS Security Algorithm
   Number of value 0 in CDS/CDNSKEY delete operations
   is potentially problematic, but we propose it here anyway as the risk
   is minimal.  The alternative is context of CDS and CDNSKEY records to reserve a DNSSEC algorithm number mean
   that the entire DS RRset at the parent must be removed.  The value 0
   remains reserved for this purpose.

   Right now, no the DS and DNSKEY records.

   No DNSSEC validator understands can treat algorithm 0 as a valid signature
   algorithm.  If a validator sees a DNSKEY or DS record with this
   algorithm value, it MUST must treat it as unknown.  Accordingly, the zone
   is treated as unsigned unless there are other algorithms present.  In
   general the value 0 should never be used in the context of DNSKEY and
   DS records.

   In

   The CERT record [RFC4398] defines the context of CDS and CDNSKEY records, DNSSEC algorithm value 0 is
   defined similarly to mean that the entire DS RRset MUST be removed.
   algorithm in the CERT record is not defined in DNSSEC.

   The contents of the CDS or CDNSKEY RRset MUST contain one RR and only
   contain the exactly the fields as shown below.

   1  CDS 0 0 0

   2  CDNSKEY 0 3 0

   The keying material payload is represented by a single 0.  This
   record is signed in the same way as regular CDS/CDNSKEY RRset's RRsets are
   signed.  This is a change in format from strict interpretation of
   [RFC7344] and may cause problems with some deployed software.

   Strictly speaking the CDS record could be "CDS X 0 X" as only the
   DNSKEY algorithm is what signals the DELETE operation, but for
   clarity the "0 0 0" notation is mandated - this is not a definition
   of DS Digest algorithm 0.  The same argument applies to "CDNSKEY 0 3
   0", the value 3 in second field is mandated by RFC4034 [RFC4034] section
   2.1.2.

   Once the parent has verified the CDS/CDNSKEY RRset and it has passed
   other acceptance tests, the parent MUST remove the DS RRset.  After
   waiting a sufficient amount of time - depending on the parental TTL's
   - the child can start the process of turning off DNSSEC.

5.  Security considerations

   This document's main goal is to avoid validation failures when a
   domain moves from one DNS operator to another.

   Turning off DNSSEC reduces the security of the domain and thus should
   only be done as a last resort.

   In most cases it is preferable that operators collaborate on the
   rollover by doing a KSK+ZSK rollover as part of the hand-off, but
   that is not always possible.  This document addresses the case where
   unsigned state is needed resort in preventing DNSSEC validation errors
   due to complete a rollover. mismatched DS and DNSKEY records.

   Users SHOULD should keep in mind that re-establishing trust in delegation
   can be hard and takes a long time.  Before deciding to complete the rollover
   via an unsigned state, all other options SHOULD should be considered. considered first.

   A parent SHOULD ensure that when it is allowing a child to become
   securely delegated, that it has a reasonable assurance that the CDS/
   CDNSKEY RRset that is used to bootstrap the security is visible from
   a geographically and topologically diverse view.  It SHOULD also
   ensure that the zone validates correctly if the parent publishes the
   DS record.  A parent zone might also consider sending an email to its
   contact addresses to give the child zone a warning that security will
   be enabled after a certain amount of wait time - thus allowing a
   child administrator to cancel the request.

   This document describes a few possible acceptance criteria for the
   Initial Trust establishment.  Due to a large variety of legal
   frameworks surrounding parent domains (TLDs in particular) this
   document cannot give a definitive list of valid acceptance criteria.
   Parental zones should look at the listed methods and pick the most
   secure method possible within their legal and technical scenario,
   possibly further securing the acceptance criteria, as long as the
   deployed method still enables a fully automated method for non-direct
   parties such as third party DNS hosters.

6.  IANA considerations

   This document updates entry number 0 of the following IANA registries: "DNS Security Algorithm
   Numbers"

   Algorithm IANA Registry as follows:

   +------+---------+-------+-------+-------+--------------------------+
   | Numb | Descrip | Mnemo | Zone  | Trans | Reference                |
   | er   | tion    | nic   | Signi | .     |                          |
   |      |         |       | ng    | Sec.  |                          |
   +------+---------+-------+-------+-------+--------------------------+
   | 0 adds a reference to this document.    | Delete  | DELET | N     | N     | [RFC4034][RFC4398]RFC-   |
   |      | DS      | E     |       |       | THIS-DOCUMENT]           |
   +------+---------+-------+-------+-------+--------------------------+

6.1.  Promoting RFC7344 to standards track

   Experience has shown that CDS/CDNSKEY are useful in the deployment of
   DNSSEC.  [RFC7344] was published as Informational, this document
   elevates RFC7344 to standards track.

7.  References

7.1.  Normative References

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <http://www.rfc-editor.org/info/rfc4034>.

   [RFC7344]  Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
              DNSSEC Delegation Trust Maintenance", RFC 7344,
              DOI 10.17487/RFC7344, September 2014,
              <http://www.rfc-editor.org/info/rfc7344>.

7.2.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/
              RFC2119, 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4398]  Josefsson, S., "Storing Certificates in the Domain Name
              System (DNS)", RFC 4398, DOI 10.17487/RFC4398, March 2006,
              <http://www.rfc-editor.org/info/rfc4398>.

Appendix A.  Acknowledgements  Acknowledgments

   This document is generated using the mmark tool that Miek Gieben has
   developed.  We thank number of people that have provided feedback and
   useful comments including Bob Harold, John Levine, Matthijs Mekking,
   Dan York, Shane Kerr, Jacques Latour.

Authors' Addresses

   Olafur Gudmundsson
   CloudFlare

   Email: olafur+ietf@cloudflare.com
   Paul Wouters
   Red Hat

   Email: pwouters@redhat.com