draft-ietf-acme-caa-04.txt   draft-ietf-acme-caa-05.txt 
ACME Working Group H. Landau ACME Working Group H. Landau
Internet-Draft May 27, 2018 Internet-Draft June 21, 2018
Intended status: Standards Track Intended status: Standards Track
Expires: November 28, 2018 Expires: December 23, 2018
CAA Record Extensions for Account URI and ACME Method Binding CAA Record Extensions for Account URI and ACME Method Binding
draft-ietf-acme-caa-04 draft-ietf-acme-caa-05
Abstract Abstract
The CAA DNS record allows a domain to communicate issuance policy to The CAA DNS record allows a domain to communicate issuance policy to
CAs, but only allows a domain to define policy with CA-level CAs, but only allows a domain to define policy with CA-level
granularity. However, the CAA specification also provides facilities granularity. However, the CAA specification also provides facilities
for extension to admit more granular, CA-specific policy. This for extension to admit more granular, CA-specific policy. This
specification defines two such parameters, one allowing specific specification defines two such parameters, one allowing specific
accounts of a CA to be identified by URI and one allowing specific accounts of a CA to be identified by URI and one allowing specific
methods of domain control validation as defined by the ACME protocol methods of domain control validation as defined by the ACME protocol
skipping to change at page 1, line 37 skipping to change at page 1, line 37
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 28, 2018. This Internet-Draft will expire on December 23, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Extensions to the CAA Record: account-uri Parameter . . . . . 3 3. Extensions to the CAA Record: accounturi Parameter . . . . . 3
3.1. Use with ACME . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Use with ACME . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Use without ACME . . . . . . . . . . . . . . . . . . . . 4 3.2. Use without ACME . . . . . . . . . . . . . . . . . . . . 4
4. Extensions to the CAA Record: validation-methods Parameter . 4 4. Extensions to the CAA Record: validationmethods Parameter . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5.1. Limited to CAs Processing CAA Records . . . . . . . . . . 5 5.1. Limited to CAs Processing CAA Records . . . . . . . . . . 5
5.2. Restrictions Ineffective without CA Recognition . . . . . 5 5.2. Restrictions Ineffective without CA Recognition . . . . . 5
5.3. Mandatory Consistency in CA Recognition . . . . . . . . . 5 5.3. Mandatory Consistency in CA Recognition . . . . . . . . . 5
5.4. URI Ambiguity . . . . . . . . . . . . . . . . . . . . . . 6 5.4. URI Ambiguity . . . . . . . . . . . . . . . . . . . . . . 6
5.5. Authorization Freshness . . . . . . . . . . . . . . . . . 6 5.5. Authorization Freshness . . . . . . . . . . . . . . . . . 6
5.6. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.6. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.7. Use without DNSSEC . . . . . . . . . . . . . . . . . . . 7 5.7. Use without DNSSEC . . . . . . . . . . . . . . . . . . . 7
5.8. Restrictions Supercedable by DNS Delegation . . . . . . . 8 5.8. Restrictions Supercedable by DNS Delegation . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Normative References . . . . . . . . . . . . . . . . . . . . 8 7. Normative References . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
This specification defines two parameters for the "issue" and This specification defines two parameters for the "issue" and
"issuewild" properties of the Certification Authority Authorization "issuewild" properties of the Certification Authority Authorization
(CAA) DNS resource record [RFC6844]. The first, "account-uri", (CAA) DNS resource record [RFC6844]. The first, "accounturi", allows
allows authorization conferred by a CAA policy to be restricted to authorization conferred by a CAA policy to be restricted to specific
specific accounts of a CA, which are identified by URIs. The second, accounts of a CA, which are identified by URIs. The second,
"validation-methods", allows the set of validation methods supported "validationmethods", allows the set of validation methods supported
by a CA to validate domain control to be limited to a subset of the by a CA to validate domain control to be limited to a subset of the
full set of methods which it supports. full set of methods which it supports.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
[RFC2119] and indicate requirement levels for compliant ACME-CAA [RFC2119] and indicate requirement levels for compliant ACME-CAA
implementations. implementations.
3. Extensions to the CAA Record: account-uri Parameter 3. Extensions to the CAA Record: accounturi Parameter
A CAA parameter "account-uri" is defined for the "issue" and A CAA parameter "accounturi" is defined for the "issue" and
"issuewild" properties defined by [RFC6844]. The value of this "issuewild" properties defined by [RFC6844]. The value of this
parameter, if specified, MUST be a URI [RFC3986] identifying a parameter, if specified, MUST be a URI [RFC3986] identifying a
specific CA account. specific CA account.
"CA account" means an object maintained by a specific CA representing "CA account" means an object maintained by a specific CA representing
a specific entity, or group of related entities, which may request a specific entity, or group of related entities, which may request
the issuance of certificates. the issuance of certificates.
The presence of this parameter constrains the property to which it is The presence of this parameter constrains the property to which it is
attached. Where a CAA property has an "account-uri" parameter, a CA attached. Where a CAA property has an "accounturi" parameter, a CA
MUST NOT consider that property to authorize issuance in the context MUST NOT consider that property to authorize issuance in the context
of a given certificate issuance request unless the CA recognises the of a given certificate issuance request unless the CA recognises the
URI specified as identifying the account making that request. URI specified as identifying the account making that request.
If a certificate issuance request is made to a CA such that no If a certificate issuance request is made to a CA such that no
account URI is available, because the request is made in the absence account URI is available, because the request is made in the absence
of any account or the account has no URI assigned to it, a CA MUST of any account or the account has no URI assigned to it, a CA MUST
NOT consider any property having an "account-uri" parameter as NOT consider any property having an "accounturi" parameter as
authorizing issuance. authorizing issuance.
If a CA finds multiple CAA records pertaining to it (i.e., having If a CA finds multiple CAA records pertaining to it (i.e., having
property "issue" or "issuewild" as applicable and a domain that the property "issue" or "issuewild" as applicable and a domain that the
CA recognises as its own) with different "account-uri" parameters, CA recognises as its own) with different "accounturi" parameters, the
the CA MUST NOT consider the CAA record set to authorize issuance CA MUST NOT consider the CAA record set to authorize issuance unless
unless at least one of the specified account URIs identifies the at least one of the specified account URIs identifies the account of
account of the CA by which issuance is requested. A property without the CA by which issuance is requested. A property without an
an "account-uri" parameter matches any account. A property with an "accounturi" parameter matches any account. A property with an
invalid or unrecognised "account-uri" parameter is unsatisfiable. A invalid or unrecognised "accounturi" parameter is unsatisfiable. A
property with multiple "account-uri" parameters is unsatisfiable. property with multiple "accounturi" parameters is unsatisfiable.
The presence of an "account-uri" parameter does not replace or The presence of an "accounturi" parameter does not replace or
supercede the need to validate the domain name specified in an supercede the need to validate the domain name specified in an
"issue" or "issuewild" record in the manner described in the CAA "issue" or "issuewild" record in the manner described in the CAA
specification. CAs MUST still perform such validation. For example, specification. CAs MUST still perform such validation. For example,
a CAA property which specifies a domain name belonging to CA A and an a CAA property which specifies a domain name belonging to CA A and an
account URI identifying an account at CA B is unsatisfiable. account URI identifying an account at CA B is unsatisfiable.
3.1. Use with ACME 3.1. Use with ACME
An ACME [I-D.ietf-acme-acme] account object MAY be identified by An ACME [I-D.ietf-acme-acme] account object MAY be identified by
setting the "account-uri" parameter to the URI of the ACME account setting the "accounturi" parameter to the URI of the ACME account
object. object.
Implementations of this specification which also implement ACME MUST Implementations of this specification which also implement ACME MUST
recognise such URIs. recognise such URIs.
3.2. Use without ACME 3.2. Use without ACME
The "account-uri" specification provides a general mechanism to The "accounturi" specification provides a general mechanism to
identify entities which may request certificate issuance via URIs. identify entities which may request certificate issuance via URIs.
The use of specific kinds of URI may be specified in future RFCs, and The use of specific kinds of URI may be specified in future RFCs, and
CAs not implementing ACME MAY assign and recognise their own URIs CAs not implementing ACME MAY assign and recognise their own URIs
arbitrarily. arbitrarily.
4. Extensions to the CAA Record: validation-methods Parameter 4. Extensions to the CAA Record: validationmethods Parameter
A CAA parameter "validation-methods" is also defined for the "issue" A CAA parameter "validationmethods" is also defined for the "issue"
and "issuewild" properties. The value of this parameter, if and "issuewild" properties. The value of this parameter, if
specified, MUST be a comma-separated string of challenge method specified, MUST be a comma-separated string of challenge method
names. Each challenge method name MUST be either an ACME challenge names. Each challenge method name MUST be either an ACME challenge
method name or a CA-assigned non-ACME challenge method name. method name or a CA-assigned non-ACME challenge method name.
The presence of this parameter constrains the property to which it is The presence of this parameter constrains the property to which it is
attached. A CA MUST only consider a property with the "validation- attached. A CA MUST only consider a property with the
methods" parameter to authorize issuance where the name of the "validationmethods" parameter to authorize issuance where the name of
challenge method being used is one of the names listed in the comma- the challenge method being used is one of the names listed in the
separated list. comma-separated list.
Where a CA supports both the "validation-methods" parameter and one Where a CA supports both the "validationmethods" parameter and one or
or more non-ACME challenge methods, it MUST assign identifiers to more non-ACME challenge methods, it MUST assign identifiers to those
those methods. These identifiers MUST be chosen to minimise the methods. These identifiers MUST be chosen to minimise the likelihood
likelihood of conflict with any ACME challenge method name; it is of conflict with any ACME challenge method name; it is RECOMMENDED
RECOMMENDED that, at the very least, CAs avoid assigning identifiers that, at the very least, CAs avoid assigning identifiers ending in a
ending in a hyphen and two digits ("-00"). hyphen and two digits ("-00").
A CA SHOULD assign individual identifiers to each of its non-ACME A CA SHOULD assign individual identifiers to each of its non-ACME
challenge methods. However, if it is unable or unwilling to do so, challenge methods. However, if it is unable or unwilling to do so,
it MAY use the fallback identifier of "non-acme" to identify such it MAY use the fallback identifier of "non-acme" to identify such
methods. methods.
5. Security Considerations 5. Security Considerations
This specification describes an extension to the CAA record This specification describes an extension to the CAA record
specification increasing the granularity at which CAA policy can be specification increasing the granularity at which CAA policy can be
skipping to change at page 5, line 34 skipping to change at page 5, line 34
The CAA parameters specified in this specification rely on their The CAA parameters specified in this specification rely on their
being recognised by the CA named by an "issue" or "issuewild" CAA being recognised by the CA named by an "issue" or "issuewild" CAA
property. As such, the parameters are not an effective means of property. As such, the parameters are not an effective means of
control over issuance unless a CA's support for the parameters is control over issuance unless a CA's support for the parameters is
established beforehand. established beforehand.
CAs which implement this specification SHOULD make available CAs which implement this specification SHOULD make available
documentation indicating as such, including explicit statements as to documentation indicating as such, including explicit statements as to
which parameters are supported. Domains configuring CAA records for which parameters are supported. Domains configuring CAA records for
a CA MUST NOT assume that the restrictions implied by the "account- a CA MUST NOT assume that the restrictions implied by the
uri" and "validation-methods" parameters are effective in the absence "accounturi" and "validationmethods" parameters are effective in the
of explicit indication as such from that CA. absence of explicit indication as such from that CA.
CAs SHOULD also document whether they implement DNSSEC validation for CAs SHOULD also document whether they implement DNSSEC validation for
DNS lookups done for validation purposes, as this affects the DNS lookups done for validation purposes, as this affects the
security of the "account-uri" and "validation-methods" parameters. security of the "accounturi" and "validationmethods" parameters.
5.3. Mandatory Consistency in CA Recognition 5.3. Mandatory Consistency in CA Recognition
A CA MUST ensure that its support for the "account-uri" and A CA MUST ensure that its support for the "accounturi" and
"validation-methods" parameters is fully consistent for a given "validationmethods" parameters is fully consistent for a given domain
domain name which a CA recognises as identifying itself in a CAA name which a CA recognises as identifying itself in a CAA "issue" or
"issue" or "issuewild" property. If a CA has multiple issuance "issuewild" property. If a CA has multiple issuance systems (for
systems (for example, an ACME-based issuance system and a non-ACME example, an ACME-based issuance system and a non-ACME based issuance
based issuance system, or two different issuance systems resulting system, or two different issuance systems resulting from a corporate
from a corporate merger), it MUST ensure that all issuance systems merger), it MUST ensure that all issuance systems recognise the same
recognise the same parameters. parameters.
A CA which is unable to do this MAY still implement the parameters by A CA which is unable to do this MAY still implement the parameters by
splitting the CA into two domain names for the purposes of CAA splitting the CA into two domain names for the purposes of CAA
processing. For example, a CA "example.com" with an ACME-based processing. For example, a CA "example.com" with an ACME-based
issuance system and a non-ACME-based issuance system could recognise issuance system and a non-ACME-based issuance system could recognise
only "acme.example.com" for the former and "example.com" for the only "acme.example.com" for the former and "example.com" for the
latter, and then implement support for the "account-uri" and latter, and then implement support for the "accounturi" and
"validation-methods" parameters for "acme.example.com" only. "validationmethods" parameters for "acme.example.com" only.
A CA which is unable to ensure consistent processing of the "account- A CA which is unable to ensure consistent processing of the
uri" or "validation-methods" parameters for a given CA domain name as "accounturi" or "validationmethods" parameters for a given CA domain
specifiable in CAA "issue" or "issuewild" properties MUST NOT name as specifiable in CAA "issue" or "issuewild" properties MUST NOT
implement support for these parameters. Failure to do so will result implement support for these parameters. Failure to do so will result
in an implementation of these parameters which does not provide in an implementation of these parameters which does not provide
effective security. effective security.
5.4. URI Ambiguity 5.4. URI Ambiguity
Suppose that CA A recognises "a.example.com" as identifying itself, Suppose that CA A recognises "a.example.com" as identifying itself,
CA B is a subsidiary of CA A which recognises both "a.example.com" CA B is a subsidiary of CA A which recognises both "a.example.com"
and "b.example.com" as identifying itself. and "b.example.com" as identifying itself.
skipping to change at page 7, line 32 skipping to change at page 7, line 32
In order to facilitate this, a CA validation process must either rely In order to facilitate this, a CA validation process must either rely
solely on information obtained via DNSSEC, or meaningfully bind the solely on information obtained via DNSSEC, or meaningfully bind the
other parts of the validation transaction using material obtained via other parts of the validation transaction using material obtained via
DNSSEC. DNSSEC.
The CAA parameters described in this specification can be used to The CAA parameters described in this specification can be used to
ensure that only validation methods meeting these criteria are used. ensure that only validation methods meeting these criteria are used.
In particular, a domain secured via DNSSEC SHOULD either: In particular, a domain secured via DNSSEC SHOULD either:
1. Use the "account-uri" parameter to ensure that only accounts 1. Use the "accounturi" parameter to ensure that only accounts which
which it controls are authorized to obtain certificates, or it controls are authorized to obtain certificates, or
2. Exclusively use validation methods which rely solely on 2. Exclusively use validation methods which rely solely on
information obtained via DNSSEC, and use the "validation-methods" information obtained via DNSSEC, and use the "validationmethods"
parameter to ensure that only such methods are used. parameter to ensure that only such methods are used.
5.7. Use without DNSSEC 5.7. Use without DNSSEC
Where a domain does not secure its nameservers using DNSSEC, or one Where a domain does not secure its nameservers using DNSSEC, or one
or more of the CAs it authorizes do not perform CAA validation or more of the CAs it authorizes do not perform CAA validation
lookups using a trusted DNSSEC-validating resolver, use of the lookups using a trusted DNSSEC-validating resolver, use of the
"account-uri" or "validation-methods" parameters does not confer "accounturi" or "validationmethods" parameters does not confer
additional security against an attacker capable of performing a man- additional security against an attacker capable of performing a man-
in-the-middle attack against all validation attempts made by a CA, as in-the-middle attack against all validation attempts made by a CA, as
such an attacker could simply fabricate the responses to DNS lookups such an attacker could simply fabricate the responses to DNS lookups
for CAA records. for CAA records.
In this case, the "account-uri" and "validation-methods" parameters In this case, the "accounturi" and "validationmethods" parameters
still provide an effective means of administrative control over still provide an effective means of administrative control over
issuance, except where control over DNS is subdelegated (see below). issuance, except where control over DNS is subdelegated (see below).
5.8. Restrictions Supercedable by DNS Delegation 5.8. Restrictions Supercedable by DNS Delegation
Because CAA records are located during validation by walking up the Because CAA records are located during validation by walking up the
DNS hierarchy until one or more records are found, the use of the DNS hierarchy until one or more records are found, the use of the
"account-uri" and "validation-methods" parameters, or any CAA policy, "accounturi" and "validationmethods" parameters, or any CAA policy,
is not an effective way to restrict or control issuance for is not an effective way to restrict or control issuance for
subdomains of a domain, where control over those subdomains is subdomains of a domain, where control over those subdomains is
delegated to another party (such as via DNS delegation or by delegated to another party (such as via DNS delegation or by
providing limited access to manage subdomain DNS records). providing limited access to manage subdomain DNS records).
6. IANA Considerations 6. IANA Considerations
None. As per the CAA specification, the parameter namespace for the None. As per the CAA specification, the parameter namespace for the
CAA "issue" and "issuewild" properties has CA-defined semantics. CAA "issue" and "issuewild" properties has CA-defined semantics.
This document merely specifies a RECOMMENDED semantic for parameters This document merely specifies a RECOMMENDED semantic for parameters
of the names "account-uri" and "validation-methods". of the names "accounturi" and "validationmethods".
7. Normative References 7. Normative References
[I-D.ietf-acme-acme] [I-D.ietf-acme-acme]
Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment Kasten, "Automatic Certificate Management Environment
(ACME)", draft-ietf-acme-acme-12 (work in progress), April (ACME)", draft-ietf-acme-acme-12 (work in progress), April
2018. 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 9, line 12 skipping to change at page 9, line 12
DOI 10.17487/RFC6844, January 2013, DOI 10.17487/RFC6844, January 2013,
<https://www.rfc-editor.org/info/rfc6844>. <https://www.rfc-editor.org/info/rfc6844>.
Appendix A. Examples Appendix A. Examples
The following shows an example DNS zone file fragment which nominates The following shows an example DNS zone file fragment which nominates
two account URIs as authorized to issue certificates for the domain two account URIs as authorized to issue certificates for the domain
"example.com". Issuance is restricted to the CA "example.net". "example.com". Issuance is restricted to the CA "example.net".
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
account-uri=https://example.net/account/1234" accounturi=https://example.net/account/1234"
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
account-uri=https://example.net/account/2345" accounturi=https://example.net/account/2345"
The following shows a zone file fragment which restricts the ACME The following shows a zone file fragment which restricts the ACME
methods which can be used; only ACME methods "dns-01" and "xyz-01" methods which can be used; only ACME methods "dns-01" and "xyz-01"
can be used. can be used.
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
validation-methods=dns-01,xyz-01" validationmethods=dns-01,xyz-01"
The following shows an equivalent way of expressing the same The following shows an equivalent way of expressing the same
restriction: restriction:
example.com. IN CAA 0 issue "example.net; validation-methods=dns-01" example.com. IN CAA 0 issue "example.net; validationmethods=dns-01"
example.com. IN CAA 0 issue "example.net; validation-methods=xyz-01" example.com. IN CAA 0 issue "example.net; validationmethods=xyz-01"
The following shows a zone file fragment in which one account can be The following shows a zone file fragment in which one account can be
used to issue with the "dns-01" method and one account can be used to used to issue with the "dns-01" method and one account can be used to
issue with the "http-01" method. issue with the "http-01" method.
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
account-uri=https://example.net/account/1234; \ accounturi=https://example.net/account/1234; \
validation-methods=dns-01" validationmethods=dns-01"
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
account-uri=https://example.net/account/2345; \ accounturi=https://example.net/account/2345; \
validation-methods=http-01" validationmethods=http-01"
The following shows a zone file fragment in which only ACME method The following shows a zone file fragment in which only ACME method
"dns-01" can be used, but non-ACME methods of issuance are also "dns-01" can be used, but non-ACME methods of issuance are also
allowed. allowed.
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
validation-methods=dns-01,non-acme" validationmethods=dns-01,non-acme"
Author's Address Author's Address
Hugo Landau Hugo Landau
Email: hlandau@devever.net Email: hlandau@devever.net
 End of changes. 37 change blocks. 
70 lines changed or deleted 70 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/