One document matched: draft-ogud-dnsop-maintain-ds-00.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM 'rfc2629.dtd' []>
<rfc ipr="trust200902" category="info" docName="draft-ogud-dnsop-maintain-ds-00">
<?rfc toc="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<front>
<title abbrev="DS-maintain-ds">Managing DS records from parent via CDS/CDNSKEY</title>

<author initials="O." surname="Gudmundsson" fullname="Olafur Gudmundsson">
<organization>CloudFlare</organization>
<address>
<postal>
<street></street>
<city></city>
<code></code>
<country></country>
</postal>
<email>olafur+ietf@cloudflare.com</email>
<uri></uri>
</address>
</author>
<author initials="P." surname="Wouters" fullname="Paul Wouters">
<organization>Red Hat</organization>
<address>
<postal>
<street></street>
<city></city>
<code></code>
<country></country>
</postal>
<email>pwouters@redhat.com</email>
<uri></uri>
</address>
</author>
<date year="2015" month="October" day="15"/>

<area>Operations</area>
<workgroup></workgroup>
<keyword>dnssec</keyword>
<keyword>trust maintainance</keyword>


<abstract>
<t>RFC7344 specifies how DNS 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 both these omissions.
</t>
<t>Changing a domain's DNSSEC status can be a complicated matter involving
many parties. Some of these parties, such as the DNS operator, might
not even be known by all organisations involved. The inability to
enable or disable DNSSEC via in-band signalling is seen as a problem
or liability that prevents DNSSEC adoption at large scale. This
document adds a method for in-band signalling of DNSSEC status changes.
</t>
<t>Initial trust is considered a much harder problem, this document will
seek to clarify and simplify the initial acceptance policy.
</t>
</abstract>

</front>

<middle>

<section anchor="introduction" title="Introduction">
<t>CDS/CDNSKEY <xref target="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 inform the parent that changes are
needed. RFC7344 contains no "delete" signal for the child to tell the parent
that it wants to change the DNSSEC security of its domain.
</t>
<t><xref target="RFC7344"/> punted the Initial Trust establishment question and
left it to each parent to come up with an acceptance policy.
</t>

<section anchor="removing-ds" title="Removing DS">
<t>This document introduces the delete option for both CDS and CDNSKEY.
to allow a child to signal the parent to turn off DNSSEC.
When a domain is moved from one DNS operator to another one, sometimes
it is necessary to turn off DNSSEC to facilitate the change of DNS
operator. Common scenarios include:
<vspace/>

</t>
<t>
<list style="format %d">
<t>moving from a DNSSEC operator to a non-DNSSEC capable one or one
that does not support the same algorithms as the old one.</t>
<t>moving to one that cannot/does-not-want to do a proper DNSSEC rollover.</t>
<t>the domain holder does not want DNSSEC.</t>
<t>when moving between two DNS operators that use disjoint sets of
algorithms to sign the zone, thus algorithm roll can not be performed.</t>
</list>
</t>
<t>Whatever the reason, the lack of a "remove my DNSSEC" option is turning
into the latest excuse as why DNSSEC cannot be deployed.
</t>
<t>Turing off DNSSEC reduces the security of the domain and thus should
only be done carefully, and that decision should be fully under the
child domain's control.
</t>
</section>

<section anchor="introducing-ds" title="Introducing DS">
<t>The converse issue is how does a child domain instruct the parent it
wants to have a DS record added. This problem is not as hard as many
have assumed, given a few simplifying assumptions. This document makes
the assumption that there are reasonable policies that can be applied
and will allow automation of trust introduction.
</t>
<t>Not being able to enable trust via an easily automated mechanism is
hindering DNSSEC at scale by anyone that does not have automated access to
its parent's "registry".
</t>
</section>

<section anchor="notation" title="Notation">
<t>When this document uses the word CDS it implies that the same applies
to CDNSKEY and vice versa, the only difference between the two
records is how information is represented.
</t>
<t>When the document uses the word "parent" it implies an entity that is
authorized to insert into parent zone information about this child
domain. Which entity this is exactly 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 could be some other entity when the RRR framework is not
used.
</t>
<t>We use RRR to mean Registry Registrar Reseller in the context of DNS domain markets.
</t>
</section>

<section anchor="terminology" title="Terminology">
<t>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 <xref target="RFC2119"/>.
</t>
</section>
</section>

<section anchor="the-three-uses-of-cds" title="The Three Uses of CDS">
<t>In general there are three operations that a domain wants to influence
on its parent:

</t>
<t>
<list style="format %d">
<t>Roll over 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</t>
<t>Turn off DNSSEC validation, i.e. delete all the DS records</t>
<t>Enable DNSSEC validation, i.e. place initial DS RRset in the parent.</t>
</list>
</t>
<t>Operation 1 is covered in <xref target="RFC7344"/>, operations 2 and 3 are defined in this
document. In many people's minds, those two later operations carry more
risk than the first one. This document argues that 2 is identical to 1
and the final one is different (but not that different).
</t>

<section anchor="the-meaning-of-cds-" title="The meaning of CDS ?">
<t>The fundamental question is what is the semantic meaning of publishing
a CDS RRset in a zone? We offer the following interpretation:
</t>
<t>"Publishing a CDS or CDNSKEY record signifies to the parent that the
child is ready for the corresponding DS records to 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."
</t>
<t>In short, the CDS RRset is an instruction to the parent to modify DS RRset if
the CDS and DS RRsets differ. The acceptance policy for CDS in the rollover
case is "seeing" according to <xref target="RFC7344"/>. The acceptance policy in the Delete
case is just seeing a CDS RRset with the delete operation specified in this
document.
</t>
</section>
</section>

<section anchor="enabling-dnssec-via-cdscdnskey" title="Enabling DNSSEC via CDS/CDNSKEY">
<t>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 the child publishes the CDS until the
corresponding DS is published is the period that DNS answers for the
child could be forged. The goal is to keep this period as short as
possible.
</t>
<t>One important case is how a 3rd 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.
</t>
<t>Below are some policies that parents can use. These policies assume that
the notifications are can be authenticated and/or identified.
</t>

<section anchor="accept-policy-via-authenticated-channel" title="Accept policy via authenticated channel">
<t>In this case the parent is notified via UI/API that CDS exists, the parent
retrieves the CDS and inserts the DS record as requested, if the request
comes over an authenticated channel.
</t>
</section>

<section anchor="accept-with-extra-checks" title="Accept with extra checks">
<t>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 requestor, whether
there have been any changes in registration in the last few days, etc, or
the parent can send a notification requesting an confirmation.
</t>
<t>The end result is that the CDS is accepted at the end of the checks or when the
out-of-band confirmation is received.
</t>
</section>

<section anchor="accept-after-delay" title="Accept after delay">
<t>In this case, if the parent deems the request valid, it starts
monitoring the CDS records at the child nameservers over period of
time to make sure nothing changes. After number of checks, preferably
from different vantage points, the parent accepts the CDS records as
a valid signal to update.
</t>
</section>

<section anchor="accept-with-challenge" title="Accept with challenge">
<t>In this case the parent instructs the requestor 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).
</t>
</section>
</section>

<section anchor="dnssec-delete-algorithm" title="DNSSEC Delete Algorithm">
<t>The DNSKEY algorithm registry contains two reserved values: 0 and 255<xref target="RFC4034"/>.
The CERT record <xref target="RFC4398"/> defines the value 0 to mean the algorithm
in the CERT record is not defined in DNSSEC.
</t>
<t>[rfc-editor remove before publication]
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.
[rfc-editor end remove]
</t>
<t>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.
</t>
<t>In the context of CDS and CDNSKEY records, DNSSEC algorithm 0 is
defined and means the entire DS set MUST be removed. The contents of the records MUST
contain only the fixed fields as show below.

</t>
<t>
<list style="format %d">
<t>CDS 0 0 0</t>
<t>CDNSKEY 0 3 0</t>
</list>
</t>
<t>There is no keying material payload in the records, just the command to
delete all DS records. This record is signed in the same way as
CDS/CDNSKEY is signed.
</t>
<t>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. Same argument applies to "CDNSKEY 0 3 0".
</t>
<t>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.
</t>
</section>

<section anchor="security-considerations" title="Security considerations">
<t>This document is about avoiding validation failures when a domain moves from
one DNS operator to another one. Turing off DNSSEC reduces the security of the
domain and thus should only be done as a last resort.
</t>
<t>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.
</t>
<t>Users SHOULD keep in mind that re-establishing trust in delegation can be
hard and take a long time thus before going to unsigned all options
SHOULD be considered.
</t>
<t>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 that is used to bootstrap the security on is visible
from a geographically and network topology diverse view. It should
also ensure the the zone would validate if the parent published the
DS record. A parent zone might also consider sending an email to
its contact addresses to give the child a warning that security
will be enabled after a certain about of wait time - thus allowing
a child administrator to cancel the request.
</t>
<t>This document does not introduce any new problems, but like Negative
Trust Anchor<xref target="I-D.ietf-dnsop-negative-trust-anchors"/>, it addresses
operational reality.
</t>
</section>

<section anchor="iana-considerations" title="IANA considerations">
<t>This document updates the following IANA registries: "DNS Security
Algorithm Numbers"
</t>
<t>Algorithm 0 adds a reference to this document.
</t>
</section>

</middle>
<back>
<references title="Normative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4034.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.7344.xml"?>
</references>
<references title="Informative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4398.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-ietf-dnsop-negative-trust-anchors-13.xml"?>
</references>

<section anchor="acknowledgements" title="Acknowledgements">
<t>This document is generated using the mmark tool that Miek Gieben has developed.
</t>
</section>

</back>
</rfc>