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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-lamps-rfc6844bis-07" submissionType="IETF"
     category="std" consensus="true" number="9999" ipr="trust200902"
     obsoletes="6844" updates="" submissionType="IETF" xml:lang="en" tocInclude="true"
     symRefs="true" sortRefs="true" version="3">

<!-- xml2rfc v2v3 conversion 2.23.1 2.23.0 -->
    <title abbrev="CAA">DNS Certification Authority Authorization (CAA) Resource Record</title>

    <seriesInfo name="Internet-Draft" value="draft-ietf-lamps-rfc6844bis-07"/> name="RFC" value="9999"/>

    <author initials="P." surname="Hallam-Baker" fullname="Phillip Hallam-Baker">
    <author initials="R." surname="Stradling" fullname="Rob Stradling">
      <organization abbrev="Sectigo">Sectigo Ltd.</organization>
    <author initials="J." surname="Hoffman-Andrews" fullname="Jacob Hoffman-Andrews">
      <organization>Let's Encrypt</organization>
    <date year="2019" month="May" day="30"/> month="June"/>

    <!-- [rfced] Please insert any keywords (beyond those that appear in
the title) for use on https://www.rfc-editor.org/search. -->
      <t>The Certification Authority Authorization (CAA) DNS Resource Record
allows a DNS domain name holder to specify one or more Certification
Authorities (CAs) authorized to issue certificates for that domain name.
CAA Resource Records allow a public Certification Authority to
implement additional controls to reduce the risk of unintended
certificate mis-issue.  This document defines the syntax of the CAA
record and rules for processing CAA records by certificate issuers.</t>
      <t>This document obsoletes RFC 6844.</t>
    <section anchor="introduction" numbered="true" toc="default">
      <t>The Certification Authority Authorization (CAA) DNS Resource Record
allows a DNS domain name holder to specify the Certification
Authorities (CAs) authorized to issue certificates for that domain name.
Publication of CAA Resource Records allows a public Certification
Authority to implement additional controls to reduce the risk of
unintended certificate mis-issue.</t>

      <t>Like the TLSA record defined in DNS-Based Authentication of Named
Entities (DANE) <xref target="RFC6698" format="default"/>, CAA records are used as a part of a
mechanism for checking PKIX <xref target="RFC6698" format="default"/> certificate data.  The distinction
between the two specifications is that CAA records specify an
authorization control to be performed by a certificate issuer before
issue of a certificate and TLSA records specify a verification
control to be performed by a relying party after the certificate is
      <t>Conformance with a published CAA record is a necessary but not
sufficient condition for issuance of a certificate.</t>
      <t>Criteria for inclusion of embedded trust anchor certificates in
applications are outside the scope of this document.  Typically, such
criteria require the CA to publish a Certification Practices Statement
(CPS) that specifies how the requirements of the Certificate Policy
(CP) are achieved.  It is also common for a CA to engage an
independent third-party auditor to prepare an annual audit statement
of its performance against its CPS.</t>
      <t>A set of CAA records describes only current grants of authority to
issue certificates for the corresponding DNS domain name.  Since
certificates are valid for a period of time, it is possible
that a certificate that is not conformant with the CAA records
currently published was conformant with the CAA records published at
the time that the certificate was issued.  Relying parties MUST
<bcp14>MUST NOT</bcp14> use CAA records as part of certificate validation.</t>
      <t>CAA records MAY <bcp14>MAY</bcp14> be used by Certificate Evaluators as a possible
indicator of a security policy violation.  Such use SHOULD <bcp14>SHOULD</bcp14> take
account of the possibility that published CAA records changed between
the time a certificate was issued and the time at which the
certificate was observed by the Certificate Evaluator.</t>
    <section anchor="definitions" numbered="true" toc="default">
      <section anchor="requirements-language" numbered="true" toc="default">
        <name>Requirements Language</name>
        <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", "<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
"<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in
BCP 14 <xref target="RFC2119" format="default"/> <xref target="RFC8174" format="default"/> when, and only when, they appear in all
capitals, as shown here.</t>
      <section anchor="defined-terms" numbered="true" toc="default">
        <name>Defined Terms</name>

        <t>The following terms are used in this document:</t>
        <t>Certificate:  An

<!--Converted plain v2 paragraphs to a v3 definition list: -->

<dl newline="true">
    <dd>An X.509 Certificate, as specified in <xref
     target="RFC5280" format="default"/>.</t>
        <t>Certificate Evaluator:  A format="default"/>.</dd>
  <dt>Certificate Evaluator:</dt>
    <dd>A party other than a Relying Party that
    evaluates the trustworthiness of certificates issued by
    Certification Authorities.</t>
        <t>Certification Authorities.</dd>
  <dt>Certification Authority (CA):  An (CA):</dt>
    <dd>An Issuer that issues certificates in
   accordance with a specified Certificate Policy.</t>
        <t>Certificate Policy.</dd>
  <dt>Certificate Policy (CP):  Specifies (CP):</dt>
    <dd>Specifies the criteria that a Certification
    Authority undertakes to meet in its issue of certificates.  See
    <xref target="RFC3647" format="default"/>.</t>
        <t>Certification format="default"/>.</dd>
  <dt>Certification Practices Statement (CPS):  Specifies (CPS):</dt>
    <dd>Specifies the means by which the criteria of the Certificate
    Policy are met.  In most cases, this will be the document against which
    the operations of the Certification Authority are audited.  See <xref
    target="RFC3647" format="default"/>.</t>
        <t>Domain Name: The format="default"/>.</dd>
  <dt>Domain Name:</dt>
    <dd>The label assigned to a node in the Domain Name System.</t>
        <t>Domain System.</dd>
  <dt>Domain Name System (DNS):  The (DNS):</dt>
    <dd>The Internet naming system specified in
   <xref target="RFC1034" format="default"/> and <xref target="RFC1035" format="default"/>.</t>
        <t>DNS format="default"/>.</dd>
  <dt>DNS Security (DNSSEC):  Extensions (DNSSEC):</dt>
    <dd>Extensions to the DNS that provide
   authentication services as specified in <xref target="RFC4033" format="default"/>, <xref target="RFC4034" format="default"/>,
   <xref target="RFC4035" format="default"/>, <xref target="RFC5155" format="default"/>, and revisions.</t>
        <t>Fully-Qualified revisions.</dd>
  <dt>Fully Qualified Domain Name (FQDN): A (FQDN):</dt>
    <dd>A Domain Name that includes the labels of all
  superior nodes in the Domain Name System.</t>
        <t>Issuer:  An System.</dd>
    <dd>An entity that issues certificates.  See <xref target="RFC5280" format="default"/>.</t>
        <t>Property:  The format="default"/>.</dd>
    <dd>The tag-value portion of a CAA Resource Record.</t>
        <t>Property Tag:  The Record.</dd>
  <dt>Property Tag:</dt>
    <dd>The tag portion of a CAA Resource Record.</t>
        <t>Property Value:  The Record.</dd>
  <dt>Property Value:</dt>
    <dd>The value portion of a CAA Resource Record.</t>
        <t>Resource Record.</dd>
  <dt>Resource Record (RR):  A (RR):</dt>
    <dd>A particular entry in the DNS including the
   owner name, class, type, time to live, and data, as defined in
   <xref target="RFC1034" format="default"/> and <xref target="RFC2181" format="default"/>.</t>
        <t>Resource format="default"/>.</dd>
  <dt>Resource Record Set (RRSet):  A (RRSet):</dt>
    <dd>A set of Resource Records of a
   particular owner name, class, and type.  The time to live on all
   RRs within an RRSet is always the same, but the data may be
   different among RRs in the RRSet.</t>
        <t>Relevant RRSet.</dd>
  <dt>Relevant Resource Record Set (Relevant RRSet):  A RRSet):</dt>
    <dd>A set of CAA Resource Records resulting
   from applying the algorithm in Section 3 <xref target="relevant-resource-record-set"
   format="default"/> to a specific Fully-Qualified Fully Qualified Domain Name or
   Wildcard Domain Name.</t>
        <t>Relying Party:  A Name.</dd>
  <dt>Relying Party:</dt>
    <dd>A party that makes use of an application whose
   operation depends on use of a certificate for making a security
   decision.  See <xref target="RFC5280" format="default"/>.</t>
        <t>Wildcard format="default"/>.</dd>
  <dt>Wildcard Domain Name: A Name:</dt>
    <dd>A Domain Name consisting of a single asterisk
   character followed by a single full stop character ("*.") followed
   by a Fully-Qualified Fully Qualified Domain Name.</t> Name.</dd>


    <section anchor="relevant-resource-record-set" numbered="true" toc="default">
      <name>Relevant Resource Record Set</name>
      <t>Before issuing a certificate, a compliant CA MUST <bcp14>MUST</bcp14> check for
publication of a Relevant RRSet.  If such an RRSet
exists, a CA MUST NOT <bcp14>MUST NOT</bcp14> issue a certificate unless the CA
determines that either (1) the certificate request is consistent with
the applicable CAA Resource Record set or (2) an exception specified
in the relevant Certificate Policy or Certification Practices
Statement applies. If the Relevant RRSet for a Fully-Qualified Fully Qualified Domain Name
or Wildcard Domain Name contains no Property Tags that restrict issuance
(for instance, if it contains only iodef Property Tags, or only Property
Tags unrecognized by the CA), CAA does not restrict issuance.</t>
      <t>A certificate request MAY <bcp14>MAY</bcp14> specify more than one Fully-Qualified Fully Qualified Domain Name and MAY <bcp14>MAY</bcp14>
specify Wildcard Domain Names.  Issuers MUST <bcp14>MUST</bcp14> verify authorization for all
the Fully-Qualified Fully Qualified Domain Names and Wildcard Domain Names specified in the request.</t>
      <t>The search for a CAA RRSet climbs the DNS name tree from the
specified label up to but not including the DNS root '.'
until a CAA RRSet is found.</t>
      <t>Given a request for a specific Fully-Qualified Fully Qualified Domain Name X, or a request for a Wildcard Domain
Name *.X, the Relevant Resource Record Set RelevantCAASet(X) is determined as
      follows (in pseudocode):</t>
      <t>Let the pseudocode below):</t>

<!-- Single-level bullet list -->
        <li>Let CAA(X) be the RRSet returned by performing a CAA record
        query for the
Fully-Qualified Fully Qualified Domain Name X, Name&nbsp;X, according to the
        lookup algorithm specified in RFC 1034 section
        <xref target="RFC1034" sectionFormat="comma" section="4.3.2"/>
       (in particular particular, chasing aliases). Let aliases).</li>
        <li>Let Parent(X) be the Fully-Qualified Fully Qualified Domain Name produced by
	removing the leftmost label of X.</t>
      <artwork name="" type="" align="left" alt=""><![CDATA[ X.</li>

   <sourcecode name="Pseudocode" type="pseudocode"><![CDATA[
  while domain is not ".":
    if CAA(domain) is not Empty:
      return CAA(domain)
    domain = Parent(domain)
  return Empty

      <t>For example, processing CAA for the Fully-Qualified Fully Qualified Domain Name "X.Y.Z" where there are
no CAA records at any level in the tree RelevantCAASet would have the
following steps:</t>
      <artwork name="" type="" align="left" alt=""><![CDATA[
CAA("X.Y.Z.") = Empty; domain = Parent("X.Y.Z.") = "Y.Z."
CAA("Y.Z.")   = Empty; domain = Parent("Y.Z.")   = "Z."
CAA("Z.")     = Empty; domain = Parent("Z.")     = "."
return Empty
      <t>Processing CAA for the Fully-Qualified Fully Qualified Domain Name "A.B.C" where there is a CAA record
"issue example.com" at "B.C" would terminate early upon finding the CAA
      <artwork name="" type="" align="left" alt=""><![CDATA[
CAA("A.B.C.") = Empty; domain = Parent("A.B.C.") = "B.C."
CAA("B.C.")   = "issue example.com"
return "issue example.com"
    <section anchor="mechanism" numbered="true" toc="default">
      <section anchor="syntax" numbered="true" toc="default">
        <t>A CAA Resource Record contains a single Property consisting of a tag-value
pair. A Fully-Qualified Fully Qualified Domain Name MAY <bcp14>MAY</bcp14> have multiple CAA RRs associated with it and a
given Property Tag MAY <bcp14>MAY</bcp14> be specified more than once than&nbsp;once across those RRs.</t>
        <t>The RDATA section for a CAA Resource Record contains one Property. A Property
consists of the following:</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
| Flags          | Tag Length = n |
| Tag char 0     | Tag char 1     |...| Tag char n-1  |
| Value byte 0   | Value byte 1   |.....| Value byte m-1 |
        <t>Where n is the length specified in the Tag length field and m is the
remaining octets in the Value field. They are related by (m = d - n - 2)
where d is the length of the RDATA section.</t>
        <t>The fields are defined as follows:</t>
        <t>Flags:  One octet containing the following field:</t>
        <t>Bit 0, Issuer Critical Flag:  If the value is set to '1', the
Property is critical. A Certification Authority MUST NOT <bcp14>MUST NOT</bcp14> issue
certificates for any FQDN the Relevant RRSet for
that FQDN contains a CAA critical
Property for an unknown or unsupported Property Tag.</t>
        <t>Note that according to the conventions set out in <xref target="RFC1035" format="default"/>, bit 0
is the Most Significant Bit and bit 7 is the Least Significant
Bit. Thus, the Flags value 1 means that bit 7 is set while a value
of 128 means that bit 0 is set according to this convention.</t>
        <t>All other bit positions are reserved for future use.</t>
        <t>To ensure compatibility with future extensions to CAA, DNS records
compliant with this version of the CAA specification MUST <bcp14>MUST</bcp14> clear
(set to "0") all reserved flags bits.  Applications that interpret
CAA records MUST <bcp14>MUST</bcp14> ignore the value of all reserved flag bits.</t>
        <t>Tag Length:  A single octet containing an unsigned integer specifying
the tag length in octets.  The tag length MUST <bcp14>MUST</bcp14> be at least 1.</t>
        <t>Tag:  The Property identifier, a sequence of US-ASCII characters.</t>
        <t>Tags MAY <bcp14>MAY</bcp14> contain US-ASCII characters 'a' through 'z', 'A'
through 'Z', and the numbers 0 through 9.  Tags MUST NOT <bcp14>MUST NOT</bcp14>
contain any other characters.  Matching of tags is case
        <t>Tags submitted for registration by IANA MUST NOT <bcp14>MUST NOT</bcp14> contain any
characters other than the (lowercase) US-ASCII characters 'a'
through 'z' and the numbers 0 through 9.</t>
        <t>Value:  A sequence of octets representing the Property Value.
Property Values are encoded as binary values and MAY <bcp14>MAY</bcp14> employ
        <t>The length of the value field is specified implicitly as the
remaining length of the enclosing RDATA section.</t>
        <section anchor="canonical-presentation-format" numbered="true" toc="default">
          <name>Canonical Presentation Format</name>
          <t>The canonical presentation format of the CAA record is:</t>
          <t>CAA &lt;flags&gt; &lt;tag&gt; &lt;value&gt;</t>

<artwork name="" type="" align="left" alt=""><![CDATA[
CAA <flags> <tag> <value>
          <t>Flags:  Is an unsigned integer between 0 and 255.</t>
          <t>Tag:  Is a non-zero-length sequence of US-ASCII letters and numbers in lower
          <t>Value:  The value field, expressed as a contiguous set of characters
   without interior spaces, or as a quoted string.  See the
   &lt;character-string&gt; format specified in
   <xref target="RFC1035" format="default"/>, Section 5.1, sectionFormat="comma" section="5.1"/>,
   but note that the value field contains no length byte and is not
   limited to 255 characters.</t>
      <section anchor="caa-issue-property" numbered="true" toc="default">
        <name>CAA issue Property</name>
        <t>If the issue Property Tag is present in the Relevant RRSet for a
Fully Qualified Domain Name, it is a request that Issuers</t>
        <ol spacing="normal" type="1">
          <li>Perform CAA issue restriction processing for the FQDN, and</li>
          <li>Grant authorization to issue certificates containing that FQDN
 to the holder of the issuer-domain-name
 or a party acting under the explicit authority of the holder of the
        <t>The CAA issue Property Value has the following sub-syntax (specified
in ABNF as per <xref target="RFC5234" format="default"/>).</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[

        <sourcecode name="CAA Issue Property Value Sub-syntax" type="abnf"><![CDATA[
issue-value = *WSP [issuer-domain-name *WSP] [";" *WSP [parameters *WSP]]

issuer-domain-name = label *("." label)
label = (ALPHA / DIGIT) *( *("-") (ALPHA / DIGIT))

parameters = (parameter *WSP ";" *WSP parameters) / parameter
parameter = tag *WSP "=" *WSP value
tag = (ALPHA / DIGIT) *( *("-") (ALPHA / DIGIT))
value = *(%x21-3A / %x3C-7E)

        <t>For consistency with other aspects of DNS administration, FQDN
values are specified in letter-digit-hyphen Label (LDH-Label) form.</t>
        <t>The following CAA record set requests that no
certificates be issued for the FQDN 'certs.example.com' by any
Issuer other than ca1.example.net or ca2.example.org.</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
certs.example.com         CAA 0 issue "ca1.example.net"
certs.example.com         CAA 0 issue "ca2.example.org"
        <t>Because the presence of an issue Property Tag in the Relevant RRSet
for an FQDN restricts issuance, FQDN owners can use an issue
Property Tag with no issuer-domain-name to request no issuance.</t>
        <t>For example, the following RRSet requests that no
certificates be issued for the FQDN 'nocerts.example.com' by any
        <artwork name="" type="" align="left" alt=""><![CDATA[
nocerts.example.com       CAA 0 issue ";"
        <t>An issue Property Tag where the issue-value does not match the ABNF
grammar MUST <bcp14>MUST</bcp14> be treated the same as one specifying an empty issuer-domain-name. For
example, the following malformed CAA RRSet forbids issuance:</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
malformed.example.com     CAA 0 issue "%%%%%"
        <t>CAA authorizations are additive; thus, the result of specifying both
an empty issuer-domain-name and a non-empty issuer-domain-name  is the
same as specifying just the non-empty issuer-domain-name.</t>
        <t>An Issuer MAY <bcp14>MAY</bcp14> choose to specify parameters that further
constrain the issue of certificates by that Issuer, for example,
specifying that certificates are to be subject to specific validation
polices, billed to certain accounts, or issued under specific trust
        <t>For example, if ca1.example.net has requested its customer
accountable.example.com to specify their account number "230123" in each
of the customer's CAA records using the (CA-defined) "account" parameter,
it would look like this:</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
accountable.example.com   CAA 0 issue "ca1.example.net; account=230123"
        <t>The semantics of parameters to the issue Property Tag are determined by
the Issuer alone.</t>
      <section anchor="caa-issuewild-property" numbered="true" toc="default">
        <name>CAA issuewild Property</name>
        <t>The issuewild Property Tag has the same syntax and semantics as the issue
Property Tag except that it only grants authorization to
issue certificates that specify a Wildcard Domain Name and issuewild
properties take precedence over issue properties when specified.
        <t>issuewild properties MUST <bcp14>MUST</bcp14> be ignored when processing a request for
a Fully-Qualified Fully Qualified Domain Name that is not a Wildcard Domain Name.</t>
        <t>If at least one issuewild Property is specified in the Relevant
RRSet for a Wildcard Domain Name, all issue properties MUST <bcp14>MUST</bcp14>
be ignored when processing a request for that Wildcard Domain Name.</t>
        <t>For example, the following RRSet requests that <em>only</em>
ca1.example.net issue certificates for "wild.example.com" or
"sub.wild.example.com", and that <em>only</em> ca2.example.org issue certificates for
"*.wild.example.com" or "*.sub.wild.example.com). Note that this presumes
there are no CAA RRs for sub.wild.example.com.</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
wild.example.com          CAA 0 issue "ca1.example.net"
wild.example.com          CAA 0 issuewild "ca2.example.org"
        <t>The following RRSet requests that <em>only</em> ca1.example.net issue
certificates for "wild2.example.com", "*.wild2.example.com" or
        <artwork name="" type="" align="left" alt=""><![CDATA[
wild2.example.com         CAA 0 issue "ca1.example.net"
        <t>The following RRSet requests that <em>only</em> ca2.example.org issue
certificates for "*.wild3.example.com" or "*.sub.wild3.example.com". It
does not permit any Issuer to issue for "wild3.example.com" or
        <artwork name="" type="" align="left" alt=""><![CDATA[
wild3.example.com         CAA 0 issuewild "ca2.example.org"
wild3.example.com         CAA 0 issue ";"
        <t>The following RRSet requests that <em>only</em> ca2.example.org issue
certificates for "*.wild3.example.com" or "*.sub.wild3.example.com". It
permits any Issuer to issue for "wild3.example.com" or "sub.wild3.example.com".</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
wild3.example.com         CAA 0 issuewild "ca2.example.org"
      <section anchor="caa-iodef-property" numbered="true" toc="default">
        <name>CAA iodef Property</name>
        <t>The iodef Property specifies a means of reporting certificate issue
requests or cases of certificate issue for domains for which the Property
appears in the Relevant RRSet, when those requests or issuances
violate the security policy of the Issuer or the FQDN holder.</t>
        <t>The Incident Object Description Exchange Format (IODEF) <xref target="RFC7970" format="default"/> is
used to present the incident report in machine-readable form.</t>
        <t>The iodef Property Tag takes a URL as its Property Value.  The URL scheme type
determines the method used for reporting:</t>

        <li>mailto:  The IODEF incident report is reported as a MIME email
   attachment to an SMTP email that is submitted to the mail address
   specified.  The mail message sent SHOULD <bcp14>SHOULD</bcp14> contain a brief text
   message to alert the recipient to the nature of the attachment.</t>
        <t>http attachment.</li>
        <li>http or https:  The IODEF report is submitted as a Web service
   request to the HTTP address specified using the protocol specified
   in <xref target="RFC6546" format="default"/>.</t> format="default"/>.</li>
        <t>These are the only supported URL schemes.</t>
        <t>The following RRSet specifies
that reports may be made by means of email with the IODEF data as an
attachment, a Web service <xref target="RFC6546" format="default"/>, or both:</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
report.example.com         CAA 0 issue "ca1.example.net"
report.example.com         CAA 0 iodef "mailto:security@example.com"
report.example.com         CAA 0 iodef "http://iodef.example.com/"
      <section anchor="critical-flag" numbered="true" toc="default">
        <name>Critical Flag</name>
        <t>The critical flag is intended to permit future versions of CAA to
introduce new semantics that MUST <bcp14>MUST</bcp14> be understood for correct
processing of the record, preventing conforming CAs that do not
recognize the new semantics from issuing certificates for the
indicated FQDNs.</t>
        <t>In the following example, the Property with a Property Tag of
'tbs' is flagged as critical.
Neither the ca1.example.net CA nor any other Issuer is authorized to
issue for "new.example.com" (or any other domains for which this is
the Relevant RRSet) unless the Issuer has implemented the
processing rules for the 'tbs' Property Tag.</t>
        <artwork name="" type="" align="left" alt=""><![CDATA[
new.example.com       CAA 0 issue "ca1.example.net"
new.example.com       CAA 128 tbs "Unknown"
    <section anchor="security-considerations" numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>CAA records assert a security policy that the holder of an FDQN
wishes to be observed by Issuers.  The effectiveness of
CAA records as an access control mechanism is thus dependent on
observance of CAA constraints by Issuers.</t>
      <t>The objective of the CAA record properties described in this document
is to reduce the risk of certificate mis-issue rather than avoid
reliance on a certificate that has been mis-issued.  DANE <xref target="RFC6698" format="default"/>
describes a mechanism for avoiding reliance on mis-issued
      <section anchor="use-of-dns-security" numbered="true" toc="default">
        <name>Use of DNS Security</name>
        <t>Use of DNSSEC to authenticate CAA RRs is strongly RECOMMENDED
<bcp14>RECOMMENDED</bcp14> but not
required.  An Issuer MUST NOT <bcp14>MUST NOT</bcp14> issue certificates if doing so would
conflict with the Relevant RRSet, irrespective of
whether the corresponding DNS records are signed.</t>
        <t>DNSSEC provides a proof of non-existence for both DNS Fully-Qualified Fully Qualified Domain Names and
RRSets within FQDNs.  DNSSEC verification thus enables an Issuer to
determine if the answer to a CAA record query is empty because the RRSet
is empty or if it is non-empty but the response has been
        <t>Use of DNSSEC allows an Issuer to acquire and archive a proof that
they were authorized to issue certificates for the FQDN.
Verification of such archives may be an audit requirement to verify
CAA record processing compliance.  Publication of such archives may
be a transparency requirement to verify CAA record processing
      <section anchor="non-compliance-by-certification-authority" numbered="true" toc="default">
        <name>Non-Compliance by Certification Authority</name>
        <t>CAA records offer CAs a cost-effective means of mitigating the risk
of certificate mis-issue: the cost of implementing CAA checks is very
small and the potential costs of a mis-issue event include the
removal of an embedded trust anchor.</t>
      <section anchor="mis-issue-by-authorized-certification-authority" numbered="true" toc="default">
        <name>Mis-Issue by Authorized Certification Authority</name>
        <t>Use of CAA records does not prevent mis-issue by an authorized
Certification Authority, i.e., a CA that is authorized to issue
certificates for the FQDN in question by CAA records.</t>
        <t>FQDN holders SHOULD <bcp14>SHOULD</bcp14> verify that the CAs they authorize to
issue certificates for their FQDNs employ appropriate controls to
ensure that certificates are issued only to authorized parties within
their organization.</t>
        <t>Such controls are most appropriately determined by the FQDN
holder and the authorized CA(s) directly and are thus out of scope of
this document.</t>
      <section anchor="suppression-or-spoofing-of-caa-records" numbered="true" toc="default">
        <name>Suppression or Spoofing of CAA Records</name>
        <t>Suppression of the CAA record or insertion of a bogus CAA record
could enable an attacker to obtain a certificate from an Issuer that
was not authorized to issue for an affected FQDN.</t>
        <t>Where possible, Issuers SHOULD <bcp14>SHOULD</bcp14> perform DNSSEC validation to detect
missing or modified CAA record sets.</t>
        <t>In cases where DNSSEC is not deployed for a corresponding FQDN, an
Issuer SHOULD <bcp14>SHOULD</bcp14> attempt to mitigate this risk by employing appropriate
DNS security controls.  For example, all portions of the DNS lookup
process SHOULD <bcp14>SHOULD</bcp14> be performed against the authoritative name server.
Data cached by third parties MUST NOT <bcp14>MUST NOT</bcp14> be relied on as the sole source of DNS CAA
information but MAY <bcp14>MAY</bcp14> be used to
support additional anti-spoofing or anti-suppression controls.</t>
      <section anchor="denial-of-service" numbered="true" toc="default">
        <name>Denial of Service</name>
        <t>Introduction of a malformed or malicious CAA RR could in theory
enable a Denial-of-Service (DoS) attack. This could happen by modification of
authoritative DNS records or by spoofing inflight DNS responses.</t>
        <t>This specific threat is not considered to add significantly to the
risk of running an insecure DNS service.</t>
        <t>An attacker could, in principle, perform a DoS attack against an
Issuer by requesting a certificate with a maliciously long DNS name.
In practice, the DNS protocol imposes a maximum name length and CAA
processing does not exacerbate the existing need to mitigate DoS
attacks to any meaningful degree.</t>
      <section anchor="abuse-of-the-critical-flag" numbered="true" toc="default">
        <name>Abuse of the Critical Flag</name>
        <t>A Certification Authority could make use of the critical flag to
trick customers into publishing records that prevent competing
Certification Authorities from issuing certificates even though the
customer intends to authorize multiple providers. This could happen if the
customers were setting CAA records based on data provided by the CA rather than
generating those records themselves.</t>
        <t>In practice, such an attack would be of minimal effect since any
competent competitor that found itself unable to issue certificates
due to lack of support for a Property marked critical should
investigate the cause and report the reason to the customer.  The
customer will thus discover that they had been deceived.</t>
    <section anchor="deployment-considerations" numbered="true" toc="default">
      <name>Deployment Considerations</name>
      <t>A CA implementing CAA may find that they receive errors looking up CAA records.
The following are some common causes of such errors, so that CAs may provide
guidance to their subscribers on fixing the underlying problems.</t>
      <section anchor="blocked-queries-or-responses" numbered="true" toc="default">
        <name>Blocked Queries or Responses</name>
        <t>Some middleboxes, in particular anti-DDoS appliances, may be configured to
drop DNS packets of unknown types, or may start dropping such packets when
they consider themselves under attack. This generally manifests as a timed-out
DNS query, or a SERVFAIL at a local recursive resolver.</t>
      <section anchor="rejected-queries-and-malformed-responses" numbered="true" toc="default">
        <name>Rejected Queries and Malformed Responses</name>
        <t>Some authoritative nameservers respond with REJECTED or NOTIMP when queried
for a Resource Record type they do not recognize. At least one authoritative
resolver produces a malformed response (with the QR bit set to 0) when queried
for unknown Resource Record types.  Per RFC 1034, the correct response for
unknown Resource Record types is NOERROR.</t>
      <section anchor="delegation-to-private-nameservers" numbered="true" toc="default">
        <name>Delegation to Private Nameservers</name>
        <t>Some FQDN administrators make the contents of a subdomain unresolvable on the
public Internet by delegating that subdomain to a nameserver whose IP address is
private. A CA processing CAA records for such subdomains will receive
SERVFAIL from its recursive resolver. The CA MAY <bcp14>MAY</bcp14> interpret that as preventing
issuance. FQDN administrators wishing to issue certificates for private
FQDNs SHOULD <bcp14>SHOULD</bcp14> use split-horizon DNS with a publicly available nameserver, so
that CAs can receive a valid, empty CAA response for those FQDNs.</t>
      <section anchor="bogus-dnssec-responses" numbered="true" toc="default">
        <name>Bogus DNSSEC Responses</name>
        <t>Queries for CAA Resource Records are different from most DNS RR types, because
a signed, empty response to a query for CAA RRs is meaningfully different
from a bogus response. A signed, empty response indicates that there is
definitely no CAA policy set at a given label. A bogus response may mean
either a misconfigured zone, or an attacker tampering with records. DNSSEC
implementations may have bugs with signatures on empty responses that go
unnoticed, because for more common Resource Record types like A and AAAA,
the difference to an end user between empty and bogus is irrelevant; they
both mean a site is unavailable.</t>
        <t>In particular, at least two authoritative resolvers that implement live signing
had bugs when returning empty Resource Record sets for DNSSEC-signed zones, in
combination with mixed-case queries. Mixed-case queries, also known as DNS 0x20,
are used by some recursive resolvers to increase resilience against DNS
poisoning attacks. DNSSEC-signing authoritative resolvers are expected to copy
the same capitalization from the query into their ANSWER section, but sign the
response as if they had used all lowercase. In particular, PowerDNS versions
prior to 4.0.4 had this bug.</t>
    <section anchor="differences-versus-rfc6844" numbered="true" toc="default">
      <name>Differences versus RFC6844</name> RFC 6844</name>
      <t>This document obsoletes RFC6844. RFC&nbsp;6844. The most important change is to
the Certification Authority Processing section. RFC6844 RFC&nbsp;6844 specified an
algorithm that performed DNS tree-climbing not only on the FQDN
being processed, but also on all CNAMEs and DNAMEs encountered along
the way. This made the processing algorithm very inefficient when used
on FQDNs that utilize many CNAMEs, and would have made it difficult
for hosting providers to set CAA policies on their own FQDNs without
setting potentially unwanted CAA policies on their customers' FQDNs.
This document specifies a simplified processing algorithm that only
performs tree climbing on the FQDN being processed, and leaves
processing of CNAMEs and DNAMEs up to the CA's recursive resolver.</t>
      <t>This document also includes a "Deployment Considerations" section
(<xref target="deployment-considerations"/>) detailing experience gained with
practical deployment of CAA enforcement among CAs in the WebPKI.</t>
      <t>This document clarifies the ABNF grammar for the issue and issuewild
      tags and resolves some inconsistencies with the document text. In
      particular, it specifies that parameters are separated with
      semicolons. It also allows hyphens in Property Tags.</t>
      <t>This document also clarifies processing of a CAA RRset that is not
      empty, but contains no issue or issuewild tags.</t> issuewild&nbsp;tags.</t>
      <t>This document removes the section titled "The CAA RR Type," merging
      it with "Mechanism" because the definitions were mainly duplicates. It
      moves the "Use of DNS Security" section
      (now <xref target="use-of-dns-security"/>) into the Security Considerations. Considerations
      section (<xref target="security-considerations"/>). It renames
      "Certification Authority Processing" to "Relevant Resource Record Set," Set"
      (<xref target="relevant-resource-record-set"/>) and emphasizes the use
      of that term to more clearly define which domains are affected by a
      given RRset.</t>
    <section anchor="iana-considerations" numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>IANA is requested to add [[[ RFC Editor: Please replace with this RFC ]]] document as a reference for the
      Certification Authority Restriction Flags and Certification Authority
      Restriction Properties registries, and update references to <xref
      target="RFC6844" format="default"/> within those registries to refer to [[[ RFC Editor: Please
replace with
      this RFC ]]]. document. IANA is also requested to update the CAA TYPE in the DNS
      Parameters registry with a reference to [[[ RFC Editor: Please replace with this RFC ]]].</t>
    <section anchor="acknowledgements" numbered="true" toc="default">
      <t>The authors would like to thank the following people who contributed
to the design and documentation of this work item: Corey Bonnell, Chris Evans,
Stephen Farrell, Jeff Hodges, Paul Hoffman, Tim Hollebeek, Stephen Kent, Adam
Langley, Ben Laurie, James Manger, Chris Palmer, Scott Schmit, Sean Turner, and
Ben Wilson.</t> document.</t>

        <name>Normative References</name>

<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6698.xml"/>

<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>

        <reference anchor="RFC6698" target="https://www.rfc-editor.org/info/rfc6698"> anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8174">
            <title>The DNS-Based Authentication
            <title>Ambiguity of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA</title> Uppercase vs Lowercase in RFC 2119 Key Words</title>
            <seriesInfo name="DOI" value="10.17487/RFC6698"/> value="10.17487/RFC8174"/>
            <seriesInfo name="RFC" value="6698"/>
            <author initials="P." surname="Hoffman" fullname="P. Hoffman">
            </author> value="8174"/>
            <seriesInfo name="BCP" value="14"/>
            <author initials="J." surname="Schlyter" fullname="J. Schlyter"> initials="B." surname="Leiba" fullname="B. Leiba">
            <date year="2012" month="August"/>
              <t>Encrypted communication on the Internet often uses Transport Layer Security (TLS), which depends on third parties to certify the keys used.  This document improves on that situation by enabling the administrators of domain names to specify the keys used in that domain's TLS servers.  This requires matching improvements in TLS client software, but no change in TLS server software.  [STANDARDS-TRACK]</t>
            </abstract> year="2017" month="May"/>

        <reference anchor="RFC2119" target="https://www.rfc-editor.org/info/rfc2119"> anchor="RFC5280" target="https://www.rfc-editor.org/info/rfc5280">
            <title>Key words for use in RFCs to Indicate Requirement Levels</title>
            <title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</title>
            <seriesInfo name="DOI" value="10.17487/RFC2119"/> value="10.17487/RFC5280"/>
            <seriesInfo name="RFC" value="2119"/>
            <seriesInfo name="BCP" value="14"/> value="5280"/>
            <author initials="S." surname="Bradner" fullname="S. Bradner">
            <date year="1997" month="March"/>
              <t>In many standards track documents several words are used to signify the requirements in the specification.  These words are often capitalized. This document defines these words as they should be interpreted in IETF documents.  This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
        <reference anchor="RFC8174" target="https://www.rfc-editor.org/info/rfc8174">
            <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
            <seriesInfo name="DOI" value="10.17487/RFC8174"/>
            <seriesInfo name="RFC" value="8174"/>
            <seriesInfo name="BCP" value="14"/>
            <author initials="B." surname="Leiba" fullname="B. Leiba">
            <date year="2017" month="May"/>
              <t>RFC 2119 specifies common key words that may be used in protocol  specifications.  This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the  defined special meanings.</t>
        <reference anchor="RFC5280" target="https://www.rfc-editor.org/info/rfc5280">
            <title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</title>
            <seriesInfo name="DOI" value="10.17487/RFC5280"/>
            <seriesInfo name="RFC" value="5280"/>
            <author initials="D." surname="Cooper" fullname="D. Cooper"> initials="D." surname="Cooper" fullname="D. Cooper">
            <author initials="S." surname="Santesson" fullname="S. Santesson">
            <author initials="S." surname="Farrell" fullname="S. Farrell">
            <author initials="S." surname="Boeyen" fullname="S. Boeyen">
            <author initials="R." surname="Housley" fullname="R. Housley">
            <author initials="W." surname="Polk" fullname="W. Polk">
            <date year="2008" month="May"/>
              <t>This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet.  An overview of this approach and model is provided as an introduction.  The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms.  Standard certificate extensions are described and two Internet-specific extensions are defined.  A set of required certificate extensions is specified.  The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions.  An algorithm for X.509 certification path validation is described.  An ASN.1 module and examples are provided in the appendices.  [STANDARDS-TRACK]</t>
        <reference anchor="RFC1034" target="https://www.rfc-editor.org/info/rfc1034">
            <title>Domain names - concepts and facilities</title>
            <seriesInfo name="DOI" value="10.17487/RFC1034"/>
            <seriesInfo name="RFC" value="1034"/>
            <seriesInfo name="STD" value="13"/>
            <author initials="P.V." surname="Mockapetris" fullname="P.V. Mockapetris">
            <date year="1987" month="November"/>
              <t>This RFC is the revised basic definition of The Domain Name System.  It obsoletes RFC-882.  This memo describes the domain style names and their used for host address look up and electronic mail forwarding.  It discusses the clients and servers in the domain name system and the protocol used between them.</t>
        <reference anchor="RFC1035" target="https://www.rfc-editor.org/info/rfc1035">
            <title>Domain names - implementation and specification</title>
            <seriesInfo name="DOI" value="10.17487/RFC1035"/>
            <seriesInfo name="RFC" value="1035"/>
            <seriesInfo name="STD" value="13"/>
            <author initials="P.V." surname="Mockapetris" fullname="P.V. Mockapetris">
            <date year="1987" month="November"/>
              <t>This RFC is the revised specification of the protocol and format used in the implementation of the Domain Name System.  It obsoletes RFC-883. This memo documents the details of the domain name client - server communication.</t>
        <reference anchor="RFC4033" target="https://www.rfc-editor.org/info/rfc4033">
            <title>DNS Security Introduction and Requirements</title>
            <seriesInfo name="DOI" value="10.17487/RFC4033"/>
            <seriesInfo name="RFC" value="4033"/>
            <author initials="R." surname="Arends" fullname="R. Arends">
            <author initials="R." surname="Austein" fullname="R. Austein">
            <author initials="M." surname="Larson" fullname="M. Larson">
            <author initials="D." surname="Massey" fullname="D. Massey">
            <author initials="S." surname="Rose" fullname="S. Rose">
            <date year="2005" month="March"/>
              <t>The Domain Name System Security Extensions (DNSSEC) add data origin authentication and data integrity to the Domain Name System.  This document introduces these extensions and describes their capabilities and limitations.  This document also discusses the services that the DNS security extensions do and do not provide.  Last, this document describes the interrelationships between the documents that collectively describe DNSSEC.  [STANDARDS-TRACK]</t>
            <author initials="R." surname="Austein" fullname="R. Austein">
            <author initials="M." surname="Larson" fullname="M. Larson">
            <author initials="D." surname="Massey" fullname="D. Massey">
            <author initials="S." surname="Rose" fullname="S. Rose">
            <date year="2005" month="March"/>
        <reference anchor="RFC4034" target="https://www.rfc-editor.org/info/rfc4034">
            <title>Resource Records for the DNS Security Extensions</title>
            <seriesInfo name="DOI" value="10.17487/RFC4034"/>
            <seriesInfo name="RFC" value="4034"/>
            <author initials="R." surname="Arends" fullname="R. Arends">
            <author initials="R." surname="Austein" fullname="R. Austein">
            <author initials="M." surname="Larson" fullname="M. Larson">
            <author initials="D." surname="Massey" fullname="D. Massey">
            <author initials="S." surname="Rose" fullname="S. Rose">
            <date year="2005" month="March"/>
              <t>This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC).  The DNS Security Extensions are a collection of resource records and protocol modifications that provide source authentication for the DNS.  This document defines the public key (DNSKEY), delegation signer (DS), resource record digital signature (RRSIG), and authenticated denial of existence (NSEC) resource records.  The purpose and format of each resource record is described in detail, and an example of each resource record is given. </t>
              <t> This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535.  [STANDARDS-TRACK]</t>
        <reference anchor="RFC4035" target="https://www.rfc-editor.org/info/rfc4035">
            <title>Protocol Modifications for the DNS Security Extensions</title>
            <seriesInfo name="DOI" value="10.17487/RFC4035"/>
            <seriesInfo name="RFC" value="4035"/>
            <author initials="R." surname="Arends" fullname="R. Arends">
            <author initials="R." surname="Austein" fullname="R. Austein">
            <author initials="M." surname="Larson" fullname="M. Larson">
            <author initials="D." surname="Massey" fullname="D. Massey">
            <author initials="S." surname="Rose" fullname="S. Rose">
            <date year="2005" month="March"/>
              <t>This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC).  The DNS Security Extensions are a collection of new resource records and protocol modifications that add data origin authentication and data integrity to the DNS.  This document describes the DNSSEC protocol modifications.  This document defines the concept of a signed zone, along with the requirements for serving and resolving by using DNSSEC.  These techniques allow a security-aware resolver to authenticate both DNS resource records and authoritative DNS error indications. </t>
              <t> This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535.  [STANDARDS-TRACK]</t>
        <reference anchor="RFC5155" target="https://www.rfc-editor.org/info/rfc5155">
            <title>DNS Security (DNSSEC) Hashed Authenticated Denial of Existence</title>
            <seriesInfo name="DOI" value="10.17487/RFC5155"/>
            <seriesInfo name="RFC" value="5155"/>
            <author initials="B." surname="Laurie" fullname="B. Laurie">
            <author initials="G." surname="Sisson" fullname="G. Sisson">
            <author initials="R." surname="Arends" fullname="R. Arends">
            <author initials="D." surname="Blacka" fullname="D. Blacka">
            <date year="2008" month="March"/>
              <t>The Domain Name System Security (DNSSEC) Extensions introduced the NSEC resource record (RR) for authenticated denial of existence. This document introduces an alternative resource record, NSEC3, which similarly provides authenticated denial of existence.  However, it also provides measures against zone enumeration and permits gradual expansion of delegation-centric zones.  [STANDARDS-TRACK]</t>
        <reference anchor="RFC2181" target="https://www.rfc-editor.org/info/rfc2181">
            <title>Clarifications to the DNS Specification</title>
            <seriesInfo name="DOI" value="10.17487/RFC2181"/>
            <seriesInfo name="RFC" value="2181"/>
            <author initials="R." surname="Elz" fullname="R. Elz">
            <author initials="R." surname="Bush" fullname="R. Bush">
            <date year="1997" month="July"/>
              <t>This document considers some areas that have been identified as problems with the specification of the Domain Name System, and proposes remedies for the defects identified. [STANDARDS-TRACK]</t>
        <reference anchor="RFC5234" target="https://www.rfc-editor.org/info/rfc5234">
            <title>Augmented BNF for Syntax Specifications: ABNF</title>
            <seriesInfo name="DOI" value="10.17487/RFC5234"/>
            <seriesInfo name="RFC" value="5234"/>
            <seriesInfo name="STD" value="68"/>
            <author initials="D." surname="Crocker" fullname="D. Crocker" role="editor">
            <author initials="P." surname="Overell" fullname="P. Overell">
            <date year="2008" month="January"/>
              <t>Internet technical specifications often need to define a formal syntax.  Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications.  The current specification documents ABNF. It balances compactness and simplicity with reasonable representational power.  The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges.  This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications.  [STANDARDS-TRACK]</t>
            </abstract> month="January"/>
        <reference anchor="RFC7970" target="https://www.rfc-editor.org/info/rfc7970">
            <title>The Incident Object Description Exchange Format Version 2</title>
            <seriesInfo name="DOI" value="10.17487/RFC7970"/>
            <seriesInfo name="RFC" value="7970"/>
            <author initials="R." surname="Danyliw" fullname="R. Danyliw">
            <date year="2016" month="November"/>
              <t>The Incident Object Description Exchange Format (IODEF) defines a data representation for security incident reports and indicators commonly exchanged by operational security teams for mitigation and watch and warning.  This document describes an updated information model for the IODEF and provides an associated data model specified with the XML schema.  This new information and data model obsoletes RFCs 5070 and 6685.</t>
        <reference anchor="RFC6546" target="https://www.rfc-editor.org/info/rfc6546">
            <title>Transport of Real-time Inter-network Defense (RID) Messages over HTTP/TLS</title>
            <seriesInfo name="DOI" value="10.17487/RFC6546"/>
            <seriesInfo name="RFC" value="6546"/>
            <author initials="B." surname="Trammell" fullname="B. Trammell">
            <date year="2012" month="April"/>
              <t>The Incident Object Description Exchange Format (IODEF) defines a common XML format for document exchange, and Real-time Inter-network Defense (RID) defines extensions to IODEF intended for the cooperative handling of security incidents within consortia of network operators and enterprises.  This document specifies an application-layer protocol for RID based upon the passing of RID messages over HTTP/TLS.  [STANDARDS-TRACK]</t>
        <reference anchor="RFC6844" target="https://www.rfc-editor.org/info/rfc6844">
            <title>DNS Certification Authority Authorization (CAA) Resource Record</title>
            <seriesInfo name="DOI" value="10.17487/RFC6844"/>
            <seriesInfo name="RFC" value="6844"/>
            <author initials="P." surname="Hallam-Baker" fullname="P. Hallam-Baker">
            <author initials="R." surname="Stradling" fullname="R. Stradling">
            <date year="2013" month="January"/>
              <t>The Certification Authority Authorization (CAA) DNS Resource Record allows a DNS domain name holder to specify one or more Certification Authorities (CAs) authorized to issue certificates for that domain. CAA Resource Records allow a public Certification Authority to implement additional controls to reduce the risk of unintended certificate mis-issue.  This document defines the syntax of the CAA record and rules for processing CAA records by certificate issuers. [STANDARDS-TRACK]</t>
        <name>Informative References</name>
        <reference anchor="RFC3647" target="https://www.rfc-editor.org/info/rfc3647">
            <title>Internet X.509 Public Key Infrastructure Certificate Policy and Certification Practices Framework</title>
            <seriesInfo name="DOI" value="10.17487/RFC3647"/>
            <seriesInfo name="RFC" value="3647"/>
            <author initials="S." surname="Chokhani" fullname="S. Chokhani">
            <author initials="W." surname="Ford" fullname="W. Ford">
            <author initials="R." surname="Sabett" fullname="R. Sabett">
            <author initials="C." surname="Merrill" fullname="C. Merrill">
            <author initials="S." surname="Wu" fullname="S. Wu">
            <date year="2003" month="November"/>
              <t>This document presents a framework

    <section anchor="acknowledgements" numbered="false" toc="default">
      <t>The authors would like to assist thank the writers of certificate policies or certification practice statements for participants within public key infrastructures, such as certification authorities, policy authorities, and communities of interest that wish following people who contributed
to rely on certificates.  In particular, the framework provides a comprehensive list design and documentation of topics that potentially (at the writer's discretion) need to be covered in a certificate policy or a certification practice statement.  This document supersedes RFC 2527.</t>
    </references> this work item: Corey Bonnell, Chris Evans,
Stephen Farrell, Jeff Hodges, Paul Hoffman, Tim Hollebeek, Stephen Kent, Adam
Langley, Ben Laurie, James Manger, Chris Palmer, Scott Schmit, Sean Turner, and
Ben Wilson.</t>

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