draft-ietf-acme-caa-06.txt   draft-ietf-acme-caa-07.txt 
ACME Working Group H. Landau ACME Working Group H. Landau
Internet-Draft January 15, 2019 Internet-Draft May 20, 2019
Intended status: Standards Track Intended status: Standards Track
Expires: July 19, 2019 Expires: November 21, 2019
CAA Record Extensions for Account URI and ACME Method Binding CAA Record Extensions for Account URI and ACME Method Binding
draft-ietf-acme-caa-06 draft-ietf-acme-caa-07
Abstract Abstract
The CAA DNS record allows a domain to communicate issuance policy to The Certification Authority Authorization (CAA) DNS record allows a
CAs, but only allows a domain to define policy with CA-level domain to communicate issuance policy to Certification Authorities
(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
to be required. to be required.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on July 19, 2019. This Internet-Draft will expire on November 21, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
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publication of this document. Please review these documents publication of this document. Please review these documents
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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: accounturi 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 . . . . . . . . . . . . . . . . . . . . 3
4. Extensions to the CAA Record: validationmethods 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 . . . . . . . . . . 4 5.1. Limited to CAs Processing CAA Records . . . . . . . . . . 4
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. Use with and without DNSSEC . . . . . . . . . . . . . . . 7 5.6. Use with and without DNSSEC . . . . . . . . . . . . . . . 6
5.7. Restrictions Supercedable by DNS Delegation . . . . . . . 8 5.7. Restrictions Supercedable by DNS Delegation . . . . . . . 7
5.8. Misconfiguration Hazards . . . . . . . . . . . . . . . . 8 5.8. Misconfiguration Hazards . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Normative References . . . . . . . . . . . . . . . . . . . . 8 7. Normative References . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 8
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, "accounturi", allows (CAA) DNS resource record [RFC6844]. The first, "accounturi", allows
authorization conferred by a CAA policy to be restricted to specific authorization conferred by a CAA policy to be restricted to specific
accounts of a CA, which are identified by URIs. The second, accounts of a CA, which are identified by URIs. The second,
"validationmethods", 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", "NOT
and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
[RFC2119] and indicate requirement levels for compliant ACME-CAA described in BCP 14 [RFC2119] [RFC8174] when, and only when, they
implementations. appear in all capitals, as shown here.
3. Extensions to the CAA Record: accounturi Parameter 3. Extensions to the CAA Record: accounturi Parameter
A CAA parameter "accounturi" 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 "accounturi" parameter, a CA attached. Where a CAA property has an "accounturi" parameter, a CA
MUST only consider that property to authorize issuance in the context MUST only consider that property to authorize issuance in the context
of a given certificate issuance request if the CA recognises the URI of a given certificate issuance request if the CA recognises the URI
specified as identifying the account making that request. specified as identifying the account making that request.
If a CA finds multiple CAA records pertaining to it (i.e., having
property "issue" or "issuewild" as applicable and a domain that the
CA recognises as its own) with different "accounturi" parameters, the
CA MUST consider the CAA record set to authorize issuance if and only
if at least one of the specified account URIs identifies the account
of the CA by which issuance is requested.
A property without an "accounturi" parameter matches any account. A A property without an "accounturi" parameter matches any account. A
property with an invalid or unrecognised "accounturi" parameter is property with an invalid or unrecognised "accounturi" parameter is
unsatisfiable. A property with multiple "accounturi" parameters is unsatisfiable. A property with multiple "accounturi" parameters is
unsatisfiable. unsatisfiable.
The presence of an "accounturi" 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 "issue" property which specifies a domain name belonging to CA a CAA "issue" property which specifies a domain name belonging to CA
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[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC6844] Hallam-Baker, P. and R. Stradling, "DNS Certification [RFC6844] Hallam-Baker, P. and R. Stradling, "DNS Certification
Authority Authorization (CAA) Resource Record", RFC 6844, Authority Authorization (CAA) Resource Record", RFC 6844,
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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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; \
accounturi=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; \
accounturi=https://example.net/account/2345" accounturi=https://example.net/account/2345"
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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; \
accounturi=https://example.net/account/1234; \ accounturi=https://example.net/account/1234; \
validationmethods=dns-01" validationmethods=dns-01"
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
accounturi=https://example.net/account/2345; \ accounturi=https://example.net/account/2345; \
validationmethods=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" or a CA-specific method "ca-foo" can be used.
allowed.
example.com. IN CAA 0 issue "example.net; \ example.com. IN CAA 0 issue "example.net; \
validationmethods=dns-01,non-acme" validationmethods=dns-01,ca-foo"
Author's Address Author's Address
Hugo Landau Hugo Landau
Email: hlandau@devever.net Email: hlandau@devever.net
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