wdiff draft-ietf-dnsop-maintain-ds-03.txt draft-ietf-dnsop-maintain-ds-04.txt

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
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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, 2016. May 4, 2017.

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
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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 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.

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