Network Working Group O. Gudmundsson
Internet-Draft CloudFlare
Intended status: Informational August 25, 2015
Expires: February 26, 2016
Removing DS records from parent via CDS/CDNSKEY
draft-ogud-dnsop-ds-remove-00
Abstract
RFC7344 specifies how trust can be maintained in-band between parent
and child. There are two features missing in that specification:
initial trust setup and removal of trust anchor. This document
addresses the second omission.
There are many reasons why a domain may want to go unsigned. Some of
them are related to DNS operator changes, others are related to
DNSSEC signing system changes. The inability to turn off DNSSEC via
in-band signalling is seen as a liability in some circles. This
document addresses the issue in a sane way.
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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 26, 2016.
Copyright Notice
Copyright (c) 2015 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
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. DNSSEC Delete Algorithm . . . . . . . . . . . . . . . . . . . 3
3. Security considerations . . . . . . . . . . . . . . . . . . . 3
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
CDS/CDNSKEY [RFC7344] records are used to signal changes in trust
anchors, this is a great way to maintain delegations when the DNS
operator has no other way to notify parent that changes are needed.
The original versions of the draft that became RFC7344 contained a
"delete" signal, the DNSOP working group at the time did not want
that feature, thus it was removed.
This document re-introduces the delete option for both CDS and
CDNSKEY. The reason is simply that it is necessary to be able to
turn off DNSSEC. The main reason has to do with when a domain is
moved from one DNS operator to another one. Common scenarios
include:
(I) moving from a DNSSEC operator to a non-DNSSEC capable one
(II) moving to one that cannot/does-not-want to do a proper DNSSEC
rollover
(III) user does not want DNSSEC
Whatever the reason, the lack of a "remove my DS" option is turning
into the latest excuse as why DNSSEC cannot be deployed.
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1.1. 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. DNSSEC Delete Algorithm
The DNSKEY algorithm registry contains two reserved values: 0 and
255[RFC4034]. The CERT record [RFC4398] defines the value 0 to mean
the algorithm in the CERT record is not defined in DNSSEC.
For this reason, using the value 0 in CDS/CDNSKEY delete operations
is potentially problematic, but we propose that here anyway as the
risk is minimal. The alternative is to reserve one DNSSEC algorithm
number for this purpose.
Right now, no DNSSEC validator understands algorithm 0 as a valid
signature algorithm, thus if the validator sees a DNSKEY or DS record
with this value, it will treat it as unknown. Accordingly, the zone
is treated as unsigned unless there are other algorithms present.
In the context of CDS and CDNSKEY records, DNSSEC algorithm 0 is
defined and means delete the DS set. The contents of the records
MUST contain only the fixed fields as show below.
(I) CDS 0 0 0
(II) CDNSKEY 0 3 0
The there is no keying information in the records, just the command
to delete all DS records. This record is signed in the same way as
CDS/CDNSKEY is signed.
Once the parent has verified the CDS/CDNSKEY record and it has passed
other acceptance tests, the DS record MUST be removed. At this point
the child can start the process of turning DNSSEC off.
3. Security considerations
This document is about avoiding validation failures when a domain
moves from one DNS operator to another one. In most cases it is
preferable that operators collaborate on the rollover by doing a
KSK+ZSK rollover as part of the handoff, but that is not always
possible. This document addresses the case where unsigned state is
needed.
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This document does not introduce any new problems, but like Negative
Trust Anchor[I-D.ietf-dnsop-negative-trust-anchors], it addresses
operational reality.
4. IANA considerations
This document updates the following IANA registries: "DNS Security
Algorithm Numbers"
Algorithm 0 adds a reference to this document.
5. References
5.1. 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>.
5.2. Informative References
[I-D.ietf-dnsop-negative-trust-anchors]
Ebersman, P., Kumari, W., Griffiths, C., Livingood, J.,
and R. Weber, "Definition and Use of DNSSEC Negative Trust
Anchors", draft-ietf-dnsop-negative-trust-anchors-13 (work
in progress), August 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 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
This document is generated using the mmark tool that Miek Gieben has
developed.
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The kick in the rear to finally write this draft came from Jacques
LaTour and Paul Wouters.
Author's Address
Olafur Gudmundsson
CloudFlare
Email: olafur+ietf@cloudflare.com
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