Internet Engineering Task Force (IETF) R. Housley
Request for Comments: 9608 Vigil Security
Updates: 5280 T. Okubo
Category: Standards Track DigiCert
ISSN: 2070-1721 J. Mandel
AKAYLA, Inc.
June 2024
No Revocation Available for X.509 Public Key Certificates
Abstract
X.509v3 public key certificates are profiled in RFC 5280. Short-
lived certificates are seeing greater use in the Internet. The
Certification Authority (CA) that issues these short-lived
certificates do not publish revocation information because the
certificate lifespan that is shorter than the time needed to detect,
report, and distribute revocation information. Some long-lived
X.509v3 public key certificates never expire, and they are never
revoked. This specification defines the noRevAvail certificate
extension so that a relying party can readily determine that the CA
does not publish revocation information for the certificate, and it
updates the certification path validation algorithm defined in RFC
5280 so that revocation checking is skipped when the noRevAvail
certificate extension is present.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9608.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction
1.1. Terminology
1.2. ASN.1
1.3. History
2. The noRevAvail Certificate Extension
3. Other X.509 Certificate Extensions
4. Certification Path Validation
5. ASN.1 Module
6. Security Considerations
6.1. Short-Lived Certificates
6.2. Long-Lived Certificates
7. IANA Considerations
8. References
8.1. Normative References
8.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
X.509v3 public key certificates [RFC5280] with short validity periods
are seeing greater use in the Internet. For example, Automatic
Certificate Management Environment (ACME) [RFC8555] provides a
straightforward way to obtain short-lived certificates. In many
cases, no revocation information is made available for short-lived
certificates by the Certification Authority (CA). This is because
short-lived certificates have a validity period that is shorter than
the time needed to detect, report, and distribute revocation
information. As a result, revoking a short-lived certificate that is
used for authentication or key management is unnecessary and
pointless. On the other hand, revoking a certificate associated with
a long-lived signature, such as document signing or code signing,
provides some important information about when a compromise was
discovered.
Some long-lived X.509v3 public key certificates never expire, and
they are never revoked. For example, a factory might include an
IDevID certificate [IEEE802.1AR] to bind the factory-assigned device
identity to a factory-installed public key. This identity might
include the manufacturer, model, and serial number of the device,
which never change. To indicate that a certificate has no well-
defined expiration date, the notAfter date in the certificate
validity period is set to "99991231235959Z" [RFC5280].
This specification defines the noRevAvail certificate extension so
that a relying party can readily determine that the CA does not
publish revocation information for the end-entity certificate, and it
updates the certification path validation algorithm defined in
[RFC5280] so that revocation checking is skipped when the noRevAvail
certificate extension is present.
Note that the noRevAvail certificate extension provides similar
functionality to the ocsp-nocheck certificate extension [RFC6960].
The ocsp-nocheck certificate extension is appropriate for inclusion
only in certificates issued to Online Certificate Status Protocol
(OCSP) responders, whereas the noRevAvail certificate extension is
appropriate in any end-entity certificate for which the CA will not
publish revocation information. To avoid disruption to the OCSP
ecosystem, implementers should not think of the noRevAvail
certificate extension a substitute for the ocsp-nocheck certificate
extension; however, the noRevAvail certificate extension could be
included in certificates issued to OCSP responders in addition to the
ocsp-nocheck certificate extension.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. ASN.1
X.509 certificates are generated using ASN.1 [X.680], using the Basic
Encoding Rules (BER) and the Distinguished Encoding Rules (DER)
[X.690].
1.3. History
In 1988, CCITT defined the X.509v1 certificate [X.509-1988].
In 1997, ITU-T defined the X.509v3 certificate and the attribute
certificate [X.509-1997].
In 1999, the IETF first profiled the X.509v3 certificate for use in
the Internet [RFC2459].
In 2000, ITU-T defined the noRevAvail certificate extension for use
with attribute certificates [X.509-2000].
In 2002, the IETF first profiled the attribute certificate for use in
the Internet [RFC3281], and this profile included support for the
noRevAvail certificate extension.
In 2019, ITU-T published an update to ITU-T Recommendation X.509
[X.509-2019].
With greater use of short-lived certificates in the Internet, the
recent Technical Corrigendum to ITU-T Recommendation X.509
[X.509-2019-TC2] allows the noRevAvail certificate extension to be
used with public key certificates as well as attribute certificates.
2. The noRevAvail Certificate Extension
The noRevAvail extension, defined in [X.509-2019-TC2], allows a CA to
indicate that no revocation information will be made available for
this certificate.
This extension MUST NOT be present in CA public key certificates.
Conforming CAs MUST include this extension in certificates for which
no revocation information will be published. When present,
conforming CAs MUST mark this extension as non-critical.
name id-ce-noRevAvail
OID { id-ce 56 }
syntax NULL (i.e. '0500'H is the DER encoding)
criticality MUST be FALSE
A relying party that does not understand this extension might be able
to find a Certificate Revocation List (CRL) from the CA, but the CRL
will never include an entry for the certificate containing this
extension.
3. Other X.509 Certificate Extensions
Certificates for CAs MUST NOT include the noRevAvail extension.
Certificates that include the noRevAvail extension MUST NOT include
certificate extensions that point to CRL repositories or provide
locations of OCSP responders. If the noRevAvail extension is present
in a certificate, then:
* The certificate MUST NOT also include the basic constraints
certificate extension with the cA BOOLEAN set to TRUE; see
Section 4.2.1.9 of [RFC5280].
* The certificate MUST NOT also include the CRL Distribution Points
certificate extension; see Section 4.2.1.13 of [RFC5280].
* The certificate MUST NOT also include the Freshest CRL certificate
extension; see Section 4.2.1.15 of [RFC5280].
* The Authority Information Access certificate extension, if
present, MUST NOT include an id-ad-ocsp accessMethod; see
Section 4.2.2.1 of [RFC5280].
If any of the above are violated in a certificate, then the relying
party MUST consider the certificate invalid.
4. Certification Path Validation
Section 6.1.3 of [RFC5280] describes basic certificate processing
within the certification path validation procedures. In particular,
Step (a)(3) says:
| At the current time, the certificate is not revoked. This may be
| determined by obtaining the appropriate CRL (Section 6.3), by
| status information, or by out-of-band mechanisms.
If the noRevAvail certificate extension specified in this document is
present or the ocsp-nocheck certificate extension [RFC6960] is
present, then Step (a)(3) is skipped. Otherwise, revocation status
determination of the certificate is performed.
5. ASN.1 Module
This section provides an ASN.1 module [X.680] for the noRevAvail
certificate extension, and it follows the conventions established in
[RFC5912] and [RFC6268].
<CODE BEGINS>
NoRevAvailExtn
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-noRevAvail(110) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
IMPORTS
EXTENSION
FROM PKIX-CommonTypes-2009 -- RFC 5912
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkixCommon-02(57) } ;
-- noRevAvail Certificate Extension
ext-noRevAvail EXTENSION ::= {
SYNTAX NULL
IDENTIFIED BY id-ce-noRevAvail
CRITICALITY { FALSE } }
-- noRevAvail Certificate Extension OID
id-ce OBJECT IDENTIFIER ::= { joint-iso-ccitt(2) ds(5) 29 }
id-ce-noRevAvail OBJECT IDENTIFIER ::= { id-ce 56 }
END
<CODE ENDS>
6. Security Considerations
The Security Considerations in [RFC5280] are relevant.
When the noRevAvail certificate extension is included in a
certificate, all revocation checking is bypassed. CA policies and
practices MUST ensure that the noRevAvail certificate extension is
included only when appropriate, as any misuse or misconfiguration
could result in a relying party continuing to trust a revoked
certificate. When such misuse is discovered, the only possible
remediation is the revocation of the CA.
Some applications may have dependencies on revocation information or
assume its availability. The absence of revocation information may
require modifications or alternative configuration settings to ensure
proper application security and functionality.
The absence of revocation information limits the ability of relying
parties to detect compromise of end-entity keying material or
malicious certificates. It also limits their ability to detect CAs
that are not following the security practices, certificate issuance
policies, and operational controls that are specified in the
Certificate Policy (CP) or the Certification Practices Statement
(CPS) [RFC3647].
Since the absence of revocation information may limit the ability to
detect compromised keying material or malicious certificates, relying
parties need confidence that the CA is following security practices,
implementing certificate issuance policies, and properly using
operational controls. Relying parties may evaluate CA reliability,
monitor CA performance, and observe CA incident response
capabilities.
6.1. Short-Lived Certificates
No revocation information is made available for short-lived
certificates because the certificate validity period is shorter than
the time needed to detect, report, and distribute revocation
information. If the noRevAvail certificate extension is incorrectly
used for a certificate validity period that is not adequately short,
it creates a window of opportunity for attackers to exploit a
compromised private key. Therefore, it is crucial to carefully
assess and set an appropriate certificate validity period before
implementing the noRevAvail certificate extension.
6.2. Long-Lived Certificates
No revocation information is made available for some long-lived
certificates that contain information that never changes. For
example, IDevID certificates [IEEE802.1AR] are included in devices at
the factory, and they are used to obtain LDevID certificates
[IEEE802.1AR] in an operational environment. In this case,
cryptographic algorithms that are expected to remain secure for the
expected lifetime of the device need to be chosen. If the noRevAvail
certificate extension is used, the CA has no means of notifying the
relying party about compromise of the factory-installed keying
material.
7. IANA Considerations
IANA has assigned the following object identifier (OID) for the ASN.1
module (see Section 5) within the "SMI Security for PKIX Module
Identifier" (1.3.6.1.5.5.7.0) registry:
+=========+===================+
| Decimal | Description |
+=========+===================+
| 110 | id-mod-noRevAvail |
+---------+-------------------+
Table 1
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[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>.
[X.509-2019-TC2]
ITU-T, "Information Technology -- Open Systems
Interconnection -- The Directory: Public-key and attribute
certificate frameworks -- Technical Corrigendum 2", ITU-T
Recommendation X.509-2019/Cor.2-2023, October 2023,
<https://www.itu.int/rec/T-REC-X.509-202310-I!Cor2>.
[X.680] ITU-T, "Information technology -- Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, ISO/IEC 8824-1:2021, February 2021,
<https://www.itu.int/rec/T-REC-X.680>.
[X.690] ITU-T, "Information technology -- ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1-2021,
February 2021, <https://www.itu.int/rec/T-REC-X.690>.
8.2. Informative References
[IEEE802.1AR]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks - Secure Device Identity", IEEE 802.1AR-2018,
DOI 10.1109/IEEESTD.2018.8423794, 2 August 2018,
<https://ieeexplore.ieee.org/document/8423794>.
[RFC2459] Housley, R., Ford, W., Polk, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and CRL
Profile", RFC 2459, DOI 10.17487/RFC2459, January 1999,
<https://www.rfc-editor.org/info/rfc2459>.
[RFC3281] Farrell, S. and R. Housley, "An Internet Attribute
Certificate Profile for Authorization", RFC 3281,
DOI 10.17487/RFC3281, April 2002,
<https://www.rfc-editor.org/info/rfc3281>.
[RFC3647] Chokhani, S., Ford, W., Sabett, R., Merrill, C., and S.
Wu, "Internet X.509 Public Key Infrastructure Certificate
Policy and Certification Practices Framework", RFC 3647,
DOI 10.17487/RFC3647, November 2003,
<https://www.rfc-editor.org/info/rfc3647>.
[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
DOI 10.17487/RFC5912, June 2010,
<https://www.rfc-editor.org/info/rfc5912>.
[RFC6268] Schaad, J. and S. Turner, "Additional New ASN.1 Modules
for the Cryptographic Message Syntax (CMS) and the Public
Key Infrastructure Using X.509 (PKIX)", RFC 6268,
DOI 10.17487/RFC6268, July 2011,
<https://www.rfc-editor.org/info/rfc6268>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>.
[X.509-1988]
CCITT, "The Directory - Authentication Framework", CCITT
Recommendation X.509-1988, November 1988,
<https://www.itu.int/rec/T-REC-X.509-198811-S>.
[X.509-1997]
ITU-T, "Information technology -- Open Systems
Interconnection -- The Directory: Authentication
framework", ITU-T Recommendation X.509-1997, August 1997,
<https://www.itu.int/rec/T-REC-X.509-199708-S>.
[X.509-2000]
ITU-T, "Information Technology -- Open Systems
Interconnection -- The Directory: Public-key and attribute
certificate frameworks", ITU-T Recommendation X.509-2000,
March 2000,
<https://www.itu.int/rec/T-REC-X.509-200003-S>.
[X.509-2019]
ITU-T, "Information Technology -- Open Systems
Interconnection -- The Directory: Public-key and attribute
certificate frameworks", ITU-T Recommendation X.509-2019,
October 2019,
<https://www.itu.int/rec/T-REC-X.509-201910-I>.
Acknowledgements
Many thanks to Erik Anderson for his efforts to make the noRevAvail
certificate extension available for use with public key end-entity
certificates as well as attribute certificates.
Many thanks to (in alphabetical order) Corey Bonnell, Hendrik
Brockhaus, Tim Hollebeek, Mike Ounsworth, Seo Suchan, Carl Wallace,
Éric Vyncke, and Paul Wouters for their review and insightful
comments.
Authors' Addresses
Russ Housley
Vigil Security, LLC
Herndon, Virginia
United States of America
Email: housley@vigilsec.com
Tomofumi Okubo
DigiCert, Inc.
Fairfax, Virginia
United States of America
Email: tomofumi.okubo+ietf@gmail.com
Joseph Mandel
AKAYLA, Inc.
Tacoma, Washington
United States of America
Email: joe@akayla.com
