No Revocation Available for Short-lived X.509 Certificates

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Table of Contents

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 short-lived certificates is unnecessary and pointless. 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.¶

2. The noRevAvail Certificate Extension

The noRevAvail extension, defined in [X.509-TBD], allows an CA to indicate that no revocation information will be made available for this certificate.¶

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 that include the noRevAvail extension MUST NOT include certificate extensions that point to Certificate Revocation List (CRL) repositories or provide locations of Online Certificate Status Protocol (OCSP) Responders. If the noRevAvail extension is present in a certificate, then:¶

• 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].¶

4. 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(TBD) }

  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>

5. Security Considerations

The Security Considerations in [RFC5280] are relevant.¶

The precondition for applying this mechanism securely is that the certificate's validity period is sufficiently short to enable the timely detection, reporting, and distribution of revocation information. If the certificate validity period 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.¶

When the noRevAvail certificate extension is included in a certificate, all revocation checking is bypassed, even if the CRL Distribution Points, Freshest CRL, or Authority Information Access (pointing to an OCSP Responder) certificate extensions are present. CA policies and practices MUST ensure that the noRevAvail is included only when appropriate, as any misuse or misconfiguration could result in a relying party continuing to trust a revoked certificate.¶

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.¶

Since the absence of revocation information may limit the ability to detect compromised 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, monitoring CA performance, and observe CA incident response capabilities.¶

6. IANA Considerations

For the ASN.1 Module in Section 4, IANA is requested to assign an object identifier (OID) for the module identifier. The OID for the module should be allocated in the "SMI Security for PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).¶

7. Acknowledgements

Many thanks to Erik Anderson for his efforts to make the noRevAvail certificate extension available for use with public key certificates as well as attribute certificates.¶

Authors' Addresses