



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   certificates do not publish revocation information because the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
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

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
