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xmlns:xi="http://www.w3.org/2001/XInclude"
submissionType="IETF" consensus="true"
ipr="trust200902" docName="draft-ietf-dnsop-dnssec-bootstrapping-11" submissionType="IETF" number="9615"  category="std" xml:lang="en" xmlns:xi="http://www.w3.org/2001/XInclude" updates="7344, 8078" indexInclude="true"> tocInclude="true" symRefs="true"
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<front>
  <title abbrev="dnssec-bootstrapping">Automatic abbrev="DNSSEC Bootstrapping">Automatic DNSSEC Bootstrapping using Using Authenticated Signals from the Zone's Operator</title><seriesInfo value="draft-ietf-dnsop-dnssec-bootstrapping-11" stream="IETF" status="standard" name="Internet-Draft"></seriesInfo> Operator</title>
  <seriesInfo name="RFC" value="9615"/>
  <author initials="P." surname="Thomassen" fullname="Peter Thomassen"><organization>deSEC, Thomassen">
    <organization>deSEC, Secure Systems Engineering</organization><address><postal><street></street> Engineering (SSE)</organization>
    <address>
      <postal>
	<city>Berlin</city>
	<country>Germany</country>
</postal><email>peter@desec.io</email>
</address></author><author
      </postal>
      <email>peter@desec.io</email>
    </address>
  </author>
  <author initials="N." surname="Wisiol" fullname="Nils Wisiol"><organization>deSEC, Wisiol">
    <organization>deSEC, Technische Universität Berlin</organization><address><postal><street></street> Berlin</organization>
    <address>
      <postal>
	<city>Berlin</city>
	<country>Germany</country>
</postal><email>nils@desec.io</email>
</address></author><date
      </postal>
      <email>nils@desec.io</email>
    </address>
  </author>
  <date year="2024" month="May" day="28"></date>
<area>Internet</area>
<workgroup>DNSOP Working Group</workgroup> month="July"/>

  <area>OPS</area>
  <workgroup>dnsop</workgroup>

<keyword>DNSSEC</keyword>
<keyword>bootstrapping</keyword>
<keyword>DS</keyword>
<keyword>CDS</keyword>
<keyword>CDNSKEY</keyword>

<abstract>
<t>This document introduces an in-band method for DNS operators to
publish arbitrary information about the zones for which they are authoritative
for, authoritative, in an authenticated fashion and on a per-zone basis.
The mechanism allows managed DNS operators to securely announce
DNSSEC key parameters for zones under their management, including for
zones that are not currently securely delegated.</t>
<t>Whenever DS records are absent for a zone's delegation, this signal
enables the parent's registry or registrar to cryptographically
validate the CDS/CDNSKEY records found at the child's apex.
The parent can then provision DS records for the delegation without
resorting to out-of-band validation or weaker types of cross-checks
such as &quot;Accept "Accept after Delay&quot;.</t> Delay".</t>
<t>This document establishes the DS enrollment method described in
<xref target="dnssec-bootstrapping"></xref>
Section 4 of this document as the preferred method over
those from Section 3 of RFC 8078. It also updates RFC 7344.</t>
<t>[ Ed note: This document is being collaborated on at
<eref target="https://github.com/desec-io/draft-ietf-dnsop-dnssec-bootstrapping/">https://github.com/desec-io/draft-ietf-dnsop-dnssec-bootstrapping/</eref>.
The authors gratefully accept pull requests. ]</t>

</abstract>

</front>

<middle>

<section anchor="introduction"><name>Introduction</name>
<t>Securing a DNS delegation for the first time requires that the
child's DNSSEC parameters be conveyed to the parent through some
trusted channel.
While the communication conceptually has to occur between the parent
registry and the DNSSEC key holder, what exactly that means exactly and how
the
communication is coordinated traditionally depends on the
relationship the child has with the parent.</t>
<t>A typical situation is that the key is held by the child DNS
operator; thus, the communication thus often involves this entity.
In addition, depending on the circumstances, it may also involve the
registrar, possibly via the registrant (for details, see <xref target="RFC7344"></xref>,
Appendix A).</t> target="RFC7344" sectionFormat="of" section="A"></xref>.</t>

<t>As observed in <xref target="RFC7344"></xref>, these dependencies often result in a manual
process that is susceptible to mistakes and/or errors.
In addition, due to the annoyance factor of the process, involved
parties may avoid the process of getting a DS resource record set (RRset)
published in the first place.</t>
<t>To alleviate these problems, automated provisioning of DS records has
been specified in (<xref target="RFC8078"></xref>). <xref target="RFC8078"></xref>.
It is based on the parental agent (registry or registrar) fetching
DNSSEC key parameters from the CDS and CDNSKEY records (<xref target="RFC7344"></xref>)
located at the child zone's apex, and validating them somehow.
This validation can be done using the child's existing DNSSEC chain of
trust if the objective is to update an existing DS RRset (such as
during key rollover).
However, when bootstrapping a DNSSEC delegation, the child zone has
no existing DNSSEC validation path, and so other means to ensure the
CDS/CDNSKEY records' legitimacy must be found.</t>
<t>Due to the lack of a comprehensive DNS-innate solution, either
out-of-band methods have been used so far to complete the chain of
trust, or cryptographic validation has been entirely dispensed with, in
exchange for weaker types of cross-checks such as &quot;Accept "Accept after
Delay&quot;
Delay" (<xref target="RFC8078"></xref> Section 3.3). target="RFC8078" sectionFormat="of" section="3.3"></xref>).
<xref target="RFC8078"></xref> does not define an in-band validation method for enabling
DNSSEC.</t>
<t>This document aims to close this gap by introducing an in-band method
for DNS operators to publish arbitrary information about the zones
for which they are authoritative for, authoritative, in an authenticated manner and on a
per-zone basis.
The mechanism allows managed DNS operators to securely announce
DNSSEC key parameters for zones under their management.
The parent can then use this signal to cryptographically validate the
CDS/CDNSKEY RRsets found at an insecure child zone's apex and, upon
success, secure the delegation.</t>
<t>While applicable to the vast majority of domains, the protocol does
not support certain edge cases, such as excessively long child zone
names, or DNSSEC bootstrapping for domains with in-domain nameservers
only (see <xref target="limitations"></xref>).</t>
<t>DNSSEC bootstrapping is just one application of the generic signaling
mechanism specified in this document.
Other applications might arise in the future, such as publishing
operational metadata or auxiliary information which that the DNS operator
likes to make known (e.g., API endpoints for third-party interaction).</t>
<t>Readers are expected to be familiar with DNSSEC <xref target="BCP237"></xref>.</t>

<section anchor="terminology"><name>Terminology</name>
<t>This section defines the terminology used in this document.</t>

<dl spacing="compact">
<dt>CDS/CDNSKEY</dt> spacing="normal">
<dt>CDS/CDNSKEY:</dt>
<dd>This notation refers to CDS and/or CDNSKEY, i.e., one or both.</dd>
<dt>Child</dt>
<dd>see
<dt>Child:</dt>
<dd>See <xref target="RFC9499"></xref> Section 7</dd> target="RFC9499" sectionFormat="of" section="7"></xref>.</dd>
<dt>Child DNS operator</dt> operator:</dt>
<dd>The entity that maintains and publishes the zone information for
the child DNS.</dd>
<dt>Parent</dt>
<dd>see
<dt>Parent:</dt>
<dd>See <xref target="RFC9499"></xref> Section 7</dd> target="RFC9499" sectionFormat="of" section="7"></xref>.</dd>
<dt>Parental agent</dt> agent:</dt>
<dd>The entity that has the authority to insert DS records into the
parent zone on behalf of the child.
(It could be the registry, registrar, a reseller, or some other
authorized entity.)</dd>

<dt>Signaling domain</dt> domain:</dt>
<dd>A domain name constructed by prepending the label <tt>_signal</tt> to a
hostname taken from the child's a delegation's NS RRSet. RRset.
There are as many signaling domains as there are distinct NS
targets.</dd>
<dt>Signaling name</dt> name:</dt>
<dd>The labels that are prefixed to a signaling domain in order to
identify a signaling type and a child zone's name (see
<xref target="signalingnames"></xref>).</dd>
<dt>Signaling record</dt> record:</dt>
<dd>A DNS record located at a signaling name under a signaling domain.
Signaling records are used by the child DNS operator to publish
information about the child.</dd>
<dt>Signaling type</dt> type:</dt>
<dd>A signal type identifier, such as <tt>_dsboot</tt> for DNSSEC bootstrapping.</dd>
<dt>Signaling zone</dt> zone:</dt>
<dd>The zone which that is authoritative for a given signaling record.</dd>
</dl>
</section>

<section anchor="requirements-notation"><name>Requirements Notation</name>
<t>The
        <t>
    The key words &quot;<bcp14>MUST</bcp14>&quot;, &quot;<bcp14>MUST NOT</bcp14>&quot;, &quot;<bcp14>REQUIRED</bcp14>&quot;,
&quot;<bcp14>SHALL</bcp14>&quot;, &quot;<bcp14>SHALL NOT</bcp14>&quot;, &quot;<bcp14>SHOULD</bcp14>&quot;, &quot;<bcp14>SHOULD NOT</bcp14>&quot;,
&quot;<bcp14>RECOMMENDED</bcp14>&quot;, &quot;<bcp14>NOT RECOMMENDED</bcp14>&quot;, &quot;<bcp14>MAY</bcp14>&quot;, "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>",
    "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and
&quot;<bcp14>OPTIONAL</bcp14>&quot; "<bcp14>OPTIONAL</bcp14>" in this document are to be
    interpreted as described in
BCP 14 BCP&nbsp;14 <xref target="RFC2119"></xref> target="RFC2119"/> <xref target="RFC8174"></xref>
    target="RFC8174"/> when, and only when, they appear in all capitals, as
    shown here.</t> here.
        </t>
</section>
</section>

<section anchor="updates-to-rfcs"><name>Updates to RFCs</name>
<t>The DS enrollment methods described in Section 3 of <xref target="RFC8078"></xref> target="RFC8078" sectionFormat="of" section="3"></xref> are less
secure than the method described in <xref target="dnssec-bootstrapping"></xref> of this
document.
Child
Therefore, child DNS operators and parental agents wishing to use CDS/CDNSKEY
records for initial DS enrollment SHOULD therefore <bcp14>SHOULD</bcp14> support the
authentication protocol described here.</t>
<t>In order to facilitate publication of signaling records for the purpose
of DNSSEC bootstrapping (see <xref target="signalingrecords"></xref>), the first bullet
(&quot;Location&quot;)
("Location") of <xref target="RFC7344"></xref> Section 4.1 target="RFC7344" sectionFormat="of" section="4.1"></xref> is removed.</t>
</section>

<section anchor="signaling"><name>Signaling</name>
<t>This section describes the general mechanism by which a child DNS
operator can publish an authenticated signal about a child zone.
Parental agents (or any other party) can then discover and process the
signal.
Authenticity is ensured through standard DNSSEC validation.</t>

<section anchor="chain-of-trust"><name>Chain of Trust</name>
<t>If a child DNS operator implements this specification, each signaling
zone MUST <bcp14>MUST</bcp14> be signed and be validatable by the parental agent (i.e., have
a valid publicly resolvable DNSSEC chain of trust).
This is typically achieved by securely delegating each signaling zone.</t>
<t>For example, when publishing a signal that relates to a child zone
with NS records <tt>ns1.example.net</tt> and <tt>ns2.example.org</tt>, the child
DNS operator needs to ensure that the parental agent has a valid DNSSEC
chain of trust for the zone(s) that are authoritative for the signaling
domains <tt>_signal.ns1.example.net</tt> and <tt>_signal.ns2.example.org</tt>.</t>
</section>

<section anchor="signalingnames"><name>Signaling Names</name>
<t>To publish information about the child zone in an
authenticated fashion, the child DNS operator MUST <bcp14>MUST</bcp14> publish one or
more signaling records at a signaling name under each signaling domain.</t>
<t>Signaling records MUST <bcp14>MUST</bcp14> be accompanied by RRSIG records created with
the corresponding signaling zone's key(s).
The type and contents of these signaling records depend on the type of
signal.</t>
<t>The signaling name identifies the child and the signaling type.
It is identical to the child name (with the final root label removed),
prefixed with a label containing the signaling type.</t>
</section>
</section>

<section anchor="dnssec-bootstrapping"><name>Bootstrapping a DNSSEC Delegation</name>
<t>When the child zone's CDS/CDNSKEY RRsets are used for setting up initial
trust, they need to be authenticated.
This is achieved by co-publishing copublishing the child's CDS/CDNSKEY RRsets as an
authenticated signal as described in <xref target="signaling"></xref>.
The parent can discover and validate it, thus transferring trust from
the child DNS operator nameservers' chain of trust to the child zone.</t>
<t>This protocol is not intended for updating an existing DS RRset.
For this purpose, the parental agent can validate the child's
CDS/CDNSKEY RRsets directly, using the chain of trust established by
the existing DS RRset (<xref target="RFC7344"></xref> Section 4).</t> target="RFC7344" sectionFormat="of" section="4"></xref>).</t>

<section anchor="signalingrecords"><name>Signaling Consent to Act as the Child's Signer</name>
<t>To confirm its willingness to act as the child's delegated signer and
authenticate the child's CDS/CDNSKEY RRsets, the child DNS operator
MUST co-publish
<bcp14>MUST</bcp14> copublish them at the corresponding signaling name under each
signaling domain, excluding those that would fall within the child
domain (<xref target="signalingnames"></xref>).
For simplicity, the child DNS operator MAY <bcp14>MAY</bcp14> also co-publish copublish the child's
CDS/CDNSKEY RRsets under signaling domains within the child domain,
although those signaling domains are not used for validation
(<xref target="cds-auth"></xref>).</t>
<t>Unlike the CDS/CDNSKEY RRsets at the child's apex, a signaling
record set MUST
RRset <bcp14>MUST</bcp14> be signed with the corresponding signaling zone's
key(s).  Its contents MUST <bcp14>MUST</bcp14> be identical to the corresponding
RRset published at the child's apex.</t>
<t>Existing use of CDS/CDNSKEY records was specified at the child apex
only (<xref target="RFC7344"></xref>, Section 4.1). target="RFC7344" sectionFormat="of" section="4.1"></xref>).  This protocol extends the use of
these record types to non-apex owner names for the purpose of DNSSEC
bootstrapping.  To exclude the possibility of semantic collision,
there MUST NOT <bcp14>MUST NOT</bcp14> be a zone cut at a signaling name.</t>

<section anchor="example"><name>Example</name>
<t>For the purposes of bootstrapping the child zone <tt>example.co.uk</tt> with NS
records <tt>ns1.example.net</tt>, <tt>ns2.example.org</tt>, and <tt>ns3.example.co.uk</tt>,
the required signaling domains are <tt>_signal.ns1.example.net</tt> and
<tt>_signal.ns2.example.org</tt>.</t>
<t>In the zones containing these domains, the child DNS operator
authenticates the CDS/CDNSKEY RRsets found at the child's apex by
co-publishing
copublishing them as CDS/CDNSKEY RRsets at the names:</t>

<artwork><![CDATA[_dsboot.example.co.uk._signal.ns1.example.net
_dsboot.example.co.uk._signal.ns2.example.org
]]>
_dsboot.example.co.uk._signal.ns2.example.org]]>
</artwork>
<t>These RRsets are signed with DNSSEC just like any other zone data.</t>
<t>Publication of signaling records under the in-domain name
<tt>_signal.ns3.example.co.uk</tt> is not required.</t>
</section>
</section>

<section anchor="cds-auth"><name>Validating CDS/CDNSKEY Records for DNSSEC Bootstrapping</name>
<t>To validate a child's CDS/CDNSKEY RRset for DNSSEC bootstrapping, the
parental agent, knowing both the child zone name and its NS
hostnames, MUST <bcp14>MUST</bcp14> execute the following steps:</t>

<ol>
<li><t>verify

<ol type="Step %d:">
<li anchor="s1"><t>verify that the child has no DS records published at the parent and
that at least one of its nameservers is outside the child domain;</t>
</li>
<li><t>query
<li anchor="s2"><t>query the CDS/CDNSKEY RRset at the child zone apex directly from
each of the authoritative servers as determined by the delegation's
(parent-side) NS RRset, without caching;</t>
</li>
<li><t>query
<li anchor="s3"><t>query the CDS/CDNSKEY RRset located at the signaling name under
each signaling domain (except those falling within the child domain)
using a trusted DNS resolver and enforce DNSSEC validation;</t>
</li>
<li><t>check
<li anchor="s4"><t>check (separately by record type) that all RRsets retrieved
in Steps 2 and 3 have equal contents;</t>
</li>
</ol>
<t>If the above steps succeed without error, the CDS/CDNSKEY RRsets are
successfully verified, and the parental agent can proceed with the
publication of the DS RRset under the precautions described in
<xref target="RFC8078"></xref>, Section 5.</t> target="RFC8078" sectionFormat="of" section="5"></xref>.</t>
<t>The parental agent MUST <bcp14>MUST</bcp14> abort the procedure if an error
condition occurs, in particular:</t>

<ul>
<li><t>in Step 1: <xref target="s1" format="none">Step 1</xref>: the child is already securely delegated or has in-domain
nameservers only;</t>
</li>
<li><t>in Step 2: <xref target="s2" format="none">Step 2</xref>: any failure during the retrieval of the CDS/CDNSKEY
RRset located at the child apex from any of the authoritative
nameservers;</t>
</li>
<li><t>in Step 3: <xref target="s3" format="none">Step 3</xref>: any failure to retrieve the CDS/CDNSKEY RRsets located
at the signaling name under any signaling domain, including failure
of DNSSEC validation, or unauthenticated data (AD bit not set);</t>
</li>
<li><t>in Step 4: <xref target="s4" format="none">Step 4</xref>: inconsistent responses (for at least one of the types),
including an RRset that is empty in one of Steps 2 <xref target="s2" format="none">2</xref> or 3, <xref target="s3" format="none">3</xref>, but
non-empty in the other.</t>
</li>
</ul>

<section anchor="example-1"><name>Example</name>
<t>To verify the CDS/CDNSKEY RRsets for the child <tt>example.co.uk</tt>, the
parental agent (assuming that the child delegation's NS records are
<tt>ns1.example.net</tt>, <tt>ns2.example.org</tt>, and <tt>ns3.example.co.uk</tt>)</t>

<ol>
<li><t>checks that the child domain is not yet securely delegated;</t>
</li>
<li><t>queries the CDS/CDNSKEY RRsets for <tt>example.co.uk</tt> directly from
<tt>ns1.example.net</tt>, <tt>ns2.example.org</tt>, and <tt>ns3.example.co.uk</tt>
(without caching);</t>
</li>
<li><t>queries and validates the CDS/CDNSKEY RRsets located at (see
<xref target="signalingnames"></xref>; <tt>ns3.example.co.uk</tt> is ignored because it is
in-domain)</t>
</li>
</ol>
<artwork><![CDATA[_dsboot.example.co.uk._signal.ns1.example.net
_dsboot.example.co.uk._signal.ns2.example.org
]]>
_dsboot.example.co.uk._signal.ns2.example.org]]>
</artwork>

<ol spacing="compact" start="4">
</li>

<li>checks that the CDS/CDNSKEY RRsets retrieved in Steps 2 <xref target="s2" format="none">2</xref>
and 3 <xref target="s3" format="none">3</xref> agree across responses.</li>
</ol>
<t>If all of these steps succeed, the parental agent can proceed to publish
a DS RRset as indicated by the validated CDS/CDNSKEY RRset.</t>
<t>As in-domain signaling names do not have a chain of trust at
bootstrapping time, the parental agent does not consider them during
validation.
Consequently, if all NS hostnames are in-domain, validation cannot be
completed,
completed and DS records are not published.</t>
</section>
</section>

<section anchor="triggers"><name>Triggers</name>
<t>Parental agents SHOULD <bcp14>SHOULD</bcp14> trigger the procedure described in <xref target="cds-auth"></xref>
once one of the following conditions is fulfilled:</t>

<ul>
<li><t>The parental agent receives a new or updated NS RRset for a
child;</t>
</li>
<li><t>The parental agent receives a notification indicating that the child
wishes to have its CDS/CDNSKEY RRset processed;</t>
</li>
<li><t>The parental agent encounters a signaling record during a proactive,
opportunistic scan (e.g., daily queries of signaling records for
some or all of its delegations);</t>
</li>
<li><t>The parental agent encounters a signaling record during an NSEC walk
or when parsing a signaling zone (e.g., when made available via AXFR
by the child DNS operator);</t>
</li>
<li><t>Any other condition as deemed appropriate by local policy.</t>
</li>
</ul>
<t>Timer-based trigger mechanisms (such as scans) exhibit undesirable
properties with respect to processing delay and scaling; on-demand
triggers (like notifications) are preferable. Whenever possible, child
DNS operators and parental agents are thus encouraged to use them,
reducing both delays and the amount of scanning traffic.</t>
<t>Most types of discovery (such as daily scans of delegations) are based
directly on the delegation's NS RRset.
In this case, these NS names can be used as is by the bootstrapping
algorithm (<xref target="cds-auth"></xref>) for querying signaling records.</t>
<t>Some discovery methods, however, do not imply reliable knowledge of the
delegation's NS RRset.
For example, when discovering signaling names by performing an NSEC
walk or zone transfer of a signaling zone, the parental agent MUST NOT <bcp14>MUST NOT</bcp14>
assume that a nameserver under whose signaling domain a signaling
record appears is actually authoritative for the corresponding child.</t>
<t>Instead, whenever a list of &quot;bootstrappable domains&quot; "bootstrappable domains" is obtained by means other
than directly from the parent, the parental
agent MUST <bcp14>MUST</bcp14> ascertain that the delegation actually contains the
nameserver hostname seen during discovery, and ensure that signaling
record signaling-record queries are only made against the proper set of nameservers as
listed in the child's delegation from the parent.</t>
</section>

<section anchor="limitations"><name>Limitations</name>
<t>As a consequence of Step 3 <xref target="s3" format="none">Step 3</xref> in <xref target="cds-auth"></xref>, DS bootstrapping does not
work for fully in-domain delegations, as no pre-existing preexisting chain of
trust to the child domain is available during bootstrapping.
(As a workaround, one can add an out-of-domain nameserver to the
initial NS RRset and remove it once bootstrapping is completed.
Automation for this is available via CSYNC records, see <xref target="RFC7477"></xref>.)</t>
<t>Fully qualified signaling names must by valid DNS names.
Label count and length requirements for DNS names (<xref target="RFC1035"></xref> Section
3.1) target="RFC1035" sectionFormat="of" section="3.1"></xref>) imply that the protocol does not work for unusually long child
domain names or NS hostnames.</t>
</section>
</section>

<section anchor="operational-recommendations"><name>Operational Recommendations</name>

<section anchor="child-dns-operator"><name>Child DNS Operator</name>
<t>It is possible to add CDS/CDNSKEY records and corresponding signaling
records to a zone without the domain owner's explicit knowledge.
To spare domain owners from being caught off guard by the ensuing DS
changes, child DNS operators following this practice are advised to make
that transparent, such as by informing the domain owner during zone
creation (e.g., in a GUI), GUI) or by notifying them via email.</t>
<t>When transferring a zone to another DNS operator, the old and new child
DNS operators need to cooperate to achieve a smooth transition, e.g.,
by using the multi-signer protocols described in <xref target="RFC8901"></xref>.
If all else fails, the domain owner might have to request the removal of
all DS records and have the transfer performed insecurely (see
<xref target="I-D.hardaker-dnsop-intentionally-temporary-insec"></xref>).</t>
<t>Signaling domains SHOULD <bcp14>SHOULD</bcp14> be delegated as standalone zones, so
that the signaling zone's apex coincides with the signaling domain (such
as <tt>_signal.ns1.example.net</tt>).
While it is permissible for the signaling domain to be contained
in a signaling zone of fewer labels (such as <tt>example.net</tt>), a
zone cut ensures that bootstrapping activities do not require
modifications of the zone containing the nameserver hostname.</t>
<t>Once a Child child DNS Operator operator determines that specific signaling record sets
have been processed (e.g., by seeing the result in the parent zone),
they are advised to remove them.
This will reduce the size of the signaling zone, zone and facilitate more
efficient bulk processing (such as via zone transfers).</t>
</section>

<section anchor="parental-agent"><name>Parental Agent</name>
<t>In order to ensure timely DNSSEC bootstrapping of insecure domains,
stalemate situations due to mismatch of stale cached records (Step 4 (<xref target="s4" format="none">Step 4</xref> of
<xref target="cds-auth"></xref>) need to be avoided.
  It is thus RECOMMENDED to perform <bcp14>RECOMMENDED</bcp14> that
  queries into signaling domains be performed with an (initially) empty
  resolver cache, or using that some other method for retrieving fresh data
  from authoritative servers.</t> servers be used.</t>
<t>It is also RECOMMENDED to use <bcp14>RECOMMENDED</bcp14> that QNAME minimization <xref target="RFC9156"></xref> be used when
resolving queries for signaling records, records to guard against certain
attacks (see <xref target="security"></xref>).</t>
</section>
</section>

<section anchor="security"><name>Security Considerations</name>
<t>The DNSSEC bootstrapping method introduced in this document is based on
the approaches described in <xref target="RFC8078"></xref> Section 3, target="RFC8078" sectionFormat="of" section="3"></xref>, but
adds authentication to the CDS/CDNSKEY concept.
Its security level is therefore strictly higher than that of existing
approaches described in that document (e.g., &quot;Accept "Accept after Delay&quot;). Delay").
Apart from this general improvement, the same Security Considerations
apply as in <xref target="RFC8078"></xref>.</t>
<t>The level of rigor in <xref target="cds-auth"></xref> is needed to prevent publication of a an
ill-conceived DS RRset (authorized only under a subset of NS hostnames).
This ensures, for example, that an operator in a multi-homed setup
cannot enable DNSSEC unless all other operators agree.</t>
<t>In any case, as the child DNS operator has authoritative knowledge of
the child's CDS/CDNSKEY records, it can readily detect fraudulent
provisioning of DS records.</t>
<t>In order to prevent the parents of nameserver hostnames from becoming a
single point of failure for a delegation (both in terms of resolution
availability and for the trust model of this protocol), it is advisable
to diversify
diversifying the path from the root to the child's nameserver hostnames,
such as by using hostnames is advisable. For example, different and independently operated TLDs may be used for each one.</t>
<t>If QNAME minimization <xref target="RFC9156"></xref> is not used when querying for
signaling records, an upstream parent of a signaling domain will see
those CDS/CDNSKEY queries and could respond with an authoritative answer
signed with its own key, instead of sending the referral.
Enabling QNAME minimization reduces the attack surface for such forgery.</t>
</section>

<section anchor="iana-considerations"><name>IANA Considerations</name>
<t>Per <xref target="RFC8552"></xref>, IANA is requested to add

<t>IANA has added the following entries to the
&quot;Underscored
"Underscored and Globally Scoped DNS Node Names&quot; registry:</t>

<artwork><![CDATA[+---------+------------+------------+
| RR Type | _NODE NAME | Reference  |
+---------+------------+------------+
| CDS     | _signal    | [This RFC] |
| CDNSKEY | _signal    | [This RFC] |
+---------+------------+------------+
]]>
</artwork>
<t><strong>Note to the RFC Editor</strong>: please replace &quot;This RFC&quot; in the above table with a proper reference.</t>
</section>

<section anchor="implementation-status"><name>Implementation Status</name>
<t><strong>Note to the RFC Editor</strong>: please remove this entire section before publication.</t>
<t>In addition to the information in this section, deployment is tracked
by the community at <eref target="https://github.com/oskar456/cds-updates">https://github.com/oskar456/cds-updates</eref>.</t>

<section anchor="child-dns-operator-side"><name>Child DNS Operator-side</name>

<ul>
<li><t>Operator support:</t>

<ul spacing="compact">
<li>Cloudflare has implemented bootstrapping record synthesis for all
signed customer zones.</li>
<li>Glauca HexDNS publishes bootstrapping records for its customer
zones.</li>
<li>deSEC performs bootstrapping record synthesis for its zones using
names <tt>_signal.ns1.desec.io</tt> and <tt>_signal.ns2.desec.org</tt>.</li>
</ul></li>
<li><t>Authoritative nameserver support:</t>

<ul spacing="compact">
<li>Knot DNS supports signaling record synthesis since version 3.3.5.</li>
<li>An implementation of bootstrapping record synthesis in PowerDNS is
available at <eref target="https://github.com/desec-io/desec-ns/pull/46">https://github.com/desec-io/desec-ns/pull/46</eref>.</li>
</ul></li>
</ul>
</section>

<section anchor="parental-agent-side"><name>Parental Agent-side</name>

<ul>
<li><t>ccTLD:</t>

<ul spacing="compact">
<li>SWITCH (.ch, .li) has implemented authentication of consumed CDS
records based on this draft.</li>
<li>.cl is working on an implementation.</li>
</ul></li>
<li><t>gTLD:</t>

<ul spacing="compact">
<li>Knipp has implemented consumption of DNSSEC bootstrapping records
in its TANGO and CORE Names" registry systems.</li>
<li>A deployment of this is running at .swiss.</li>
</ul></li>
<li><t>Registrars:</t>

<ul spacing="compact">
<li>Glauca has implemented authenticated CDS processing.</li>
<li>GoDaddy is working on an implementation.</li>
</ul></li>
<li><t>A tool to retrieve and process signaling records for bootstrapping
purposes, either directly or via zone walking, is available at
<eref target="https://github.com/desec-io/dsbootstrap">https://github.com/desec-io/dsbootstrap</eref>.
The tool outputs the validated DS records which then can be added
to the parent zone.</t>
</li>
</ul>
</section>
</section>

<section anchor="acknowledgements"><name>Acknowledgements</name>
<t>Thanks to Brian Dickson, Ondřej Caletka, John R. Levine, Christian
Elmerot, Oli Schacher, Donald Eastlake, Libor Peltan, Warren Kumari,
Scott Rose, Linda Dunbar, Tim Wicinski, Paul Wouters, Paul Hoffman,
Peter Yee, Benson Muite, Roman Danyliw, Éric Vyncke, and Joe Abley for
reviewing draft proposals and offering comments and suggestions.</t>
<t>Thanks also to Steve Crocker, Hugo Salgado, and Ulrich Wisser for
early-stage brainstorming.</t> <xref target="RFC8552"/>:</t>
<table anchor="iana-table">
  <name></name>
  <thead>
    <tr>
      <th>RR Type</th>
      <th>_NODE NAME</th>
      <th>Reference</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>CDS</td>
      <td>_signal</td>
      <td>RFC 9615</td>
    </tr>
    <tr>
      <td>CDNSKEY</td>
      <td>_signal</td>
      <td>RFC 9615</td>
    </tr>
  </tbody>
</table>

</section>

</middle>

<back>
<references><name>References</name>
<references><name>Normative
<displayreference target="I-D.hardaker-dnsop-intentionally-temporary-insec" to="INSEC"/>
<references>
  <name>References</name>
  <references>
    <name>Normative References</name>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.1035.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7344.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7477.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8078.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8552.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9156.xml"/>
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9499.xml"/>
  </references>
<references><name>Informative
  <references>
    <name>Informative References</name>
    <referencegroup anchor="BCP237" target="https://www.rfc-editor.org/info/bcp237">
      <xi:include href="https://bib.ietf.org/public/rfc/bibxml9/reference.BCP.237.xml"/> href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9364.xml"/>
    </referencegroup>

<!-- [I-D.hardaker-dnsop-intentionally-temporary-insec] IESG state: Expired as of 05/29/24-->
    <xi:include href="https://bib.ietf.org/public/rfc/bibxml3/reference.I-D.hardaker-dnsop-intentionally-temporary-insec.xml"/>

    <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8901.xml"/>
  </references>
</references>

<section anchor="change-history-to-be-removed-before-publication"><name>Change History (to be removed before publication)</name>

<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-11</li>
</ul>
<blockquote><t>Addressed comment by Paul Wouters</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-10</li>
</ul>
<blockquote><t>Editorial nit</t>
<t>Addressed comments by Paul Wouters</t>
<t>Make capitalization of registrar/registrant consistent</t>
<t>Editorial nit by Joe Abley</t>
<t>Addressed comments by Éric Vyncke</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-09</li>
</ul>
<blockquote><t>Addressed comments by Paul Wouters</t>
<t>Editorial nits by Roman Danyliw</t>
<t>Editorial nits by Benson Muite</t>
<t>Editorial nits by Peter Yee</t>
<t>Editorial nit by Scott Rose</t>
<t>Editorial suggestion from John Levine</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-08</li>
</ul>
<blockquote><t>Editorial changes from AD Review</t>
<t>Updated implementation section</t>
<t>Change capitalization of terms from terminology section</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-07</li>
</ul>
<blockquote><t>Add Glauca registrar implementation</t>
<t>Editorial changes to Security Considerations</t>
<t>Add/discuss on-demand triggers (notifications)</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-06</li>
</ul>
<blockquote><t>Add section &quot;Updates to RFCs&quot;</t>
<t>Editorial nits</t>
<t>Editorial changes from Secdir early review</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-05</li>
</ul>
<blockquote><t>Editorial changes</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-04</li>
</ul>
<blockquote><t>Added consent considerations.</t>
<t>Editorial changes.</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-03</li>
</ul>
<blockquote><t>Updated Implementation section.</t>
<t>Typo fix.</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-02</li>
</ul>
<blockquote><t>Clarified that RFC 8078 Section 3 is not replaced, but its methods are
  deprecated.</t>
<t>Added new deployments anchor="acknowledgements" numbered="false"><name>Acknowledgements</name>
<t>Thanks to Implementation section.</t>
<t>Included NSEC walk / AXFR as possible triggers <contact fullname="Brian Dickson"/>, <contact fullname="Ondřej Caletka"/>, <contact fullname="John R. Levine"/>, <contact fullname="Christian
Elmerot"/>, <contact fullname="Oli Schacher"/>, <contact fullname="Donald Eastlake"/>, <contact fullname="Libor Peltan"/>, <contact fullname="Warren Kumari"/>,
<contact fullname="Scott Rose"/>, <contact fullname="Linda Dunbar"/>, <contact fullname="Tim Wicinski"/>, <contact fullname="Paul Wouters"/>, <contact fullname="Paul Hoffman"/>,
<contact fullname="Peter Yee"/>, <contact fullname="Benson Muite"/>, <contact fullname="Roman Danyliw"/>, <contact fullname="Éric Vyncke"/>, and <contact fullname="Joe Abley"/> for DS bootstrapping.</t>
<t>Editorial changes.</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-01</li>
</ul>
<blockquote><t>Allow bootstrapping when some (not all) NS hostnames are in bailiwick.</t>
<t>Clarified Operational Recommendations according to operator feedback.</t>
<t>Turn loose Security Considerations points into coherent text.</t>
<t>Do no longer suggest NSEC-walking Signaling Domains.
  (It does not work well due to the Signaling Type prefix. What's more,
  it's unclear who would do this: Parents know there delegations
reviewing draft proposals and can
  do a targeted scan; others are not interested.)</t>
<t>Editorial changes.</t>
<t>Added IANA request.</t>
<t>Introduced Signaling Type prefix (<tt>_dsboot</tt>), renamed Signaling Name
  infix from <tt>_dsauth</tt> to <tt>_signal</tt>.</t>
</blockquote>
<ul spacing="compact">
<li>draft-ietf-dnsop-dnssec-bootstrapping-00</li>
</ul>
<blockquote><t>Editorial changes.</t>
</blockquote>
<ul spacing="compact">
<li>draft-thomassen-dnsop-dnssec-bootstrapping-03</li>
</ul>
<blockquote><t>Clarified importance of record cleanup by moving paragraph up.</t>
<t>Pointed out limitations.</t>
<t>Replace <xref target="RFC8078"></xref> Section 3 with our <xref target="cds-auth"></xref>.</t>
<t>Changed <tt>_boot</tt> label offering comments and suggestions.</t>
<t>Thanks also to <tt>_dsauth</tt>.</t>
<t>Removed hashing of Child name components in Signaling Names.</t>
<t>Editorial changes.</t>
</blockquote>
<ul spacing="compact">
<li>draft-thomassen-dnsop-dnssec-bootstrapping-02</li>
</ul>
<blockquote><t>Reframed as an authentication mechanism <contact fullname="Steve Crocker"/>, <contact fullname="Hugo Salgado"/>, and <contact fullname="Ulrich Wisser"/> for RFC 8078.</t>
<t>Removed multi-signer use case (focus on RFC 8078 authentication).</t>
<t>Triggers need to fetch NS records (if not implicit from context).</t>
<t>Improved title.</t>
<t>Recognized that hash collisions are dealt with by Child apex check.</t>
</blockquote>
<ul spacing="compact">
<li>draft-thomassen-dnsop-dnssec-bootstrapping-01</li>
</ul>
<blockquote><t>Add section on Triggers.</t>
<t>Clarified title.</t>
<t>Improved abstract.</t>
<t>Require CDS/CDNSKEY records at the Child.</t>
<t>Reworked Signaling Name scheme.</t>
<t>Recommend using cold cache for consumption.</t>
<t>Updated terminology (replace &quot;Bootstrapping&quot; by &quot;Signaling&quot;).</t>
<t>Added NSEC recommendation for Bootstrapping Zones.</t>
<t>Added multi-signer use case.</t>
<t>Editorial changes.</t>
</blockquote>
<ul spacing="compact">
<li>draft-thomassen-dnsop-dnssec-bootstrapping-00</li>
</ul>
<blockquote><t>Initial public draft.</t>
</blockquote></section>
early-stage brainstorming.</t>
</section>
</back>

</rfc>