Online Certificate Status Protocol (OCSP) Nonce Extension

Internet Engineering Task Force (IETF)                    H. Sharma, Ed.
Request for Comments: 9654                                  Netskope Inc
Obsoletes: 8954                                              August 2024
Updates: 6960
Category: Standards Track
ISSN: 2070-1721


       Online Certificate Status Protocol (OCSP) Nonce Extension

Abstract

   RFC 8954 imposed size constraints on the optional Nonce extension for
   the Online Certificate Status Protocol (OCSP).  OCSP is used to check
   the status of a certificate, and the Nonce extension is used to
   cryptographically bind an OCSP response message to a particular OCSP
   request message.

   Some environments use cryptographic algorithms that generate a Nonce
   value that is longer than 32 octets.  This document also modifies the
   "Nonce" section of RFC 6960 to clearly define and differentiate the
   encoding format and values for easier implementation and
   understanding.  This document obsoletes RFC 8954, which includes
   updated ASN.1 modules for OCSP, and updates RFC 6960.

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/rfc9654.

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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   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Requirements Language
   2.  OCSP Extensions
     2.1.  Nonce Extension
   3.  Security Considerations
     3.1.  Replay Attack
   4.  IANA Considerations
   5.  References
     5.1.  Normative References
     5.2.  Informative References
   Appendix A.  ASN.1 Modules
     A.1.  OCSP in ASN.1 - 1998 Syntax
     A.2.  OCSP in ASN.1 - 2008 Syntax
   Acknowledgements
   Author's Address

1.  Introduction

   The Nonce extension was previously defined in Section 4.4.1 of
   [RFC6960].  The Nonce cryptographically binds an OCSP request and a
   response.  It guarantees the freshness of an OCSP response and avoids
   replay attacks.  This extension was updated in [RFC8954].  [RFC8954]
   limits the maximum Nonce length to 32 octets.  To support
   cryptographic algorithms that generate a Nonce that is longer than 32
   octets, this document updates the maximum allowed size of the Nonce
   to 128 octets.  In addition, this document recommends that the OCSP
   requester and responder use a Nonce with a minimum length of 32
   octets.

1.1.  Requirements Language

   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.

2.  OCSP Extensions

   The message formats for OCSP requests and responses are defined in
   [RFC6960] and the Nonce extension was updated in [RFC8954].
   [RFC6960] also defines the standard extensions for OCSP messages
   based on the extension model employed in X.509 version 3 certificates
   (see [RFC5280]).  [RFC8954] replaces Section 4.4.1 of [RFC6960] to
   limit the minimum and maximum length for the Nonce value.  This
   document extends the maximum allowed nonce length to 128 octets and
   does not change the specifications of any of the other extensions
   defined in [RFC6960].

2.1.  Nonce Extension

   The Nonce cryptographically binds a request and a response to prevent
   replay attacks.  The Nonce is included as one of the
   requestExtensions in requests; in responses, it is included as one of
   the responseExtensions.  In both the request and the response, the
   Nonce is identified by the object identifier id-pkix-ocsp-nonce,
   while the extnValue is the encoded value of Nonce.  If the Nonce
   extension is present, then the length of the Nonce MUST be at least 1
   octet and can be up to 128 octets.  Implementations compliant with
   [RFC8954] will not be able to process nonces generated per the new
   specification with sizes in excess of the limit (32 octets) specified
   in [RFC8954].

   An OCSP requester that implements the extension in this document MUST
   use a minimum length of 32 octets for Nonce in the Nonce extension.

   An OCSP responder that supports the Nonce extension MUST accept Nonce
   lengths of at least 16 octets and up to and including 32 octets.  A
   responder MAY choose to respond without the Nonce extension for
   requests in which the length of the Nonce is in between 1 octet and
   15 octets or 33 octets and 128 octets.

   Responders that implement the extension in this document MUST reject
   any OCSP request that has a Nonce with a length of either 0 octets or
   greater than 128 octets, with the malformedRequest OCSPResponseStatus
   as described in Section 4.2.1 of [RFC6960].

   The value of the Nonce MUST be generated using a cryptographically
   strong pseudorandom number generator (see [RFC4086]).  The minimum
   Nonce length of 1 octet is defined to provide backward compatibility
   with older OCSP requesters that follow [RFC6960].

   id-pkix-ocsp           OBJECT IDENTIFIER ::= { id-ad-ocsp }
   id-pkix-ocsp-nonce     OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
   Nonce ::= OCTET STRING(SIZE(1..128))

   The following is an example of an encoded OCSP Nonce extension with a
   32-octet Nonce in hexadecimal format.

      30 2f 06 09 2b 06 01 05 05 07 30 01 02 04 22 04
      20 dd 49 d4 07 2c 44 9d a1 c3 17 bd 1c 1b df fe
      db e1 50 31 2e c4 cd 0a dd 18 e5 bd 6f 84 bf 14
      c8

   Here is the decoded version of the above example.  Offset, Length,
   and Object Identifier are in decimal.


      Offset  Length
      0       47    : SEQUENCE {
      2       9     :  OBJECT IDENTIFIER ocspNonce
                    :   (1 3 6 1 5 5 7 48 1 2)
      13      34    :  OCTET STRING, encapsulates {
      15      32    :   OCTET STRING
                    :    DD 49 D4 07 2C 44 9D A1 C3 17 BD 1C 1B DF FE DB
                    :    E1 50 31 2E C4 CD 0A DD 18 E5 BD 6F 84 BF 14 C8
                    :  }
                    : }

3.  Security Considerations

   The security considerations of OCSP, in general, are described in
   [RFC6960].  During the interval in which the previous OCSP response
   for a certificate is not expired but the responder has a changed
   status for that certificate, a copy of that OCSP response can be used
   to indicate that the status of the certificate is still valid.
   Including a requester's nonce value in the OCSP response ensures that
   the response is the most recent response from the server and not an
   old copy.

3.1.  Replay Attack

   The Nonce extension is used to avoid replay attacks.  Since the OCSP
   responder may choose not to send the Nonce extension in the OCSP
   response even if the requester has sent the Nonce extension in the
   request [RFC5019], an on-path attacker can intercept the OCSP request
   and respond with an earlier response from the server without the
   Nonce extension.  This can be mitigated by configuring the server to
   use a short time interval between the thisUpdate and nextUpdate
   fields in the OCSP response.

4.  IANA Considerations

   For the ASN.1 modules in Appendixes A.1 and A.2, IANA has assigned
   the following object identifiers (OIDs) in the "SMI Security for PKIX
   Module Identifier" registry (1.3.6.1.5.5.7.0):

                      +=======+=====================+
                      | Value | Description         |
                      +=======+=====================+
                      | 111   | id-mod-ocsp-2024-88 |
                      +-------+---------------------+
                      | 112   | id-mod-ocsp-2024-08 |
                      +-------+---------------------+

                                  Table 1

5.  References

5.1.  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>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <https://www.rfc-editor.org/info/rfc4086>.

   [RFC5019]  Deacon, A. and R. Hurst, "The Lightweight Online
              Certificate Status Protocol (OCSP) Profile for High-Volume
              Environments", RFC 5019, DOI 10.17487/RFC5019, September
              2007, <https://www.rfc-editor.org/info/rfc5019>.

   [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>.

   [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>.

   [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>.

   [RFC8954]  Sahni, M., Ed., "Online Certificate Status Protocol (OCSP)
              Nonce Extension", RFC 8954, DOI 10.17487/RFC8954, November
              2020, <https://www.rfc-editor.org/info/rfc8954>.

5.2.  Informative References

   [Err5891]  RFC Errata, Erratum ID 5891, RFC 6960,
              <https://www.rfc-editor.org/errata/eid5891>.

   [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>.

Appendix A.  ASN.1 Modules

   This section includes the ASN.1 modules for OCSP and replaces the
   entirety of Section 5 of [RFC8954].  It addresses Errata ID 5891
   [Err5891] as well.

   Appendix A.1 includes an ASN.1 module that conforms to the 1998
   version of ASN.1 for all syntax elements of OCSP.  This module
   replaces the module in Appendix B.1 of [RFC6960].

   Appendix A.2 includes an ASN.1 module, corresponding to the module
   present in Appendix A.1, that conforms to the 2008 version of ASN.1.
   This module replaces the modules in Section 4 of [RFC5912] and
   Appendix B.2 of [RFC6960].  Although a 2008 ASN.1 module is provided,
   the module in Appendix A.1 remains the normative module per the
   policy of the PKIX Working Group.

A.1.  OCSP in ASN.1 - 1998 Syntax

   <CODE BEGINS>
   OCSP-2024-88
         { iso(1) identified-organization(3) dod(6) internet(1)
           security(5) mechanisms(5) pkix(7) id-mod(0)
           id-mod-ocsp-2024-88(111) }

   DEFINITIONS EXPLICIT TAGS ::=
   BEGIN

   IMPORTS
       AuthorityInfoAccessSyntax, CRLReason, GeneralName
       FROM PKIX1Implicit88 -- From [RFC5280]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-pkix1-implicit(19) }

       Name, CertificateSerialNumber, Extensions,
       id-kp, id-ad-ocsp, Certificate, AlgorithmIdentifier
       FROM PKIX1Explicit88 -- From [RFC5280]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-pkix1-explicit(18) } ;

   OCSPRequest ::= SEQUENCE {
      tbsRequest              TBSRequest,
      optionalSignature   [0] EXPLICIT Signature OPTIONAL }

   TBSRequest ::= SEQUENCE {
      version             [0] EXPLICIT Version DEFAULT v1,
      requestorName       [1] EXPLICIT GeneralName OPTIONAL,
      requestList             SEQUENCE OF Request,
      requestExtensions   [2] EXPLICIT Extensions OPTIONAL }

   Signature ::= SEQUENCE {
      signatureAlgorithm      AlgorithmIdentifier,
      signature               BIT STRING,
      certs               [0] EXPLICIT SEQUENCE OF
                              Certificate OPTIONAL }

   Version ::= INTEGER { v1(0) }

   Nonce ::= OCTET STRING (SIZE(1..128))

   Request ::= SEQUENCE {
      reqCert                     CertID,
      singleRequestExtensions [0] EXPLICIT
                                  Extensions OPTIONAL }

   CertID ::= SEQUENCE {
      hashAlgorithm   AlgorithmIdentifier,
      issuerNameHash  OCTET STRING, -- Hash of issuer's DN
      issuerKeyHash   OCTET STRING, -- Hash of issuer's public key
      serialNumber    CertificateSerialNumber }

   OCSPResponse ::= SEQUENCE {
      responseStatus     OCSPResponseStatus,
      responseBytes  [0] EXPLICIT ResponseBytes OPTIONAL }

   OCSPResponseStatus ::= ENUMERATED {
      successful       (0),  -- Response has valid confirmations
      malformedRequest (1),  -- Illegal confirmation request
      internalError    (2),  -- Internal error in issuer
      tryLater         (3),  -- Try again later
                             -- (4) is not used
      sigRequired      (5),  -- Must sign the request
      unauthorized     (6)   -- Request unauthorized
   }

   ResponseBytes ::= SEQUENCE {
      responseType            OBJECT IDENTIFIER,
      response                OCTET STRING }

   BasicOCSPResponse ::= SEQUENCE {
     tbsResponseData          ResponseData,
     signatureAlgorithm       AlgorithmIdentifier,
     signature                BIT STRING,
     certs                [0] EXPLICIT SEQUENCE OF
                              Certificate OPTIONAL }

   ResponseData ::= SEQUENCE {
      version             [0] EXPLICIT Version DEFAULT v1,
      responderID             ResponderID,
      producedAt              GeneralizedTime,
                              -- The format for GeneralizedTime is
                              -- as specified in Section 4.1.2.5.2
                              -- [RFC5280]
      responses               SEQUENCE OF SingleResponse,
      responseExtensions  [1] EXPLICIT Extensions OPTIONAL }

   ResponderID ::= CHOICE {
      byName              [1] Name,
      byKey               [2] KeyHash }

   KeyHash ::= OCTET STRING
               -- SHA-1 hash of responder's public key (i.e., the
               -- SHA-1 hash of the value of the BIT STRING
               -- subjectPublicKey [excluding the tag, length, and
               -- number of unused bits] in the responder's
               -- certificate)

   SingleResponse ::= SEQUENCE {
      certID                  CertID,
      certStatus              CertStatus,
      thisUpdate              GeneralizedTime,
      nextUpdate          [0] EXPLICIT GeneralizedTime OPTIONAL,
      singleExtensions    [1] EXPLICIT Extensions OPTIONAL }

   CertStatus ::= CHOICE {
      good                [0] IMPLICIT NULL,
      revoked             [1] IMPLICIT RevokedInfo,
      unknown             [2] IMPLICIT UnknownInfo }

   RevokedInfo ::= SEQUENCE {
      revocationTime        GeneralizedTime,
      revocationReason  [0] EXPLICIT CRLReason OPTIONAL }

   UnknownInfo ::= NULL

   ArchiveCutoff ::= GeneralizedTime

   AcceptableResponses ::= SEQUENCE OF OBJECT IDENTIFIER

   ServiceLocator ::= SEQUENCE {
      issuer       Name,
      locator      AuthorityInfoAccessSyntax }

   CrlID ::= SEQUENCE {
       crlUrl     [0] EXPLICIT IA5String OPTIONAL,
       crlNum     [1] EXPLICIT INTEGER OPTIONAL,
       crlTime    [2] EXPLICIT GeneralizedTime OPTIONAL }

   PreferredSignatureAlgorithms ::= SEQUENCE OF
                                    PreferredSignatureAlgorithm

   PreferredSignatureAlgorithm ::= SEQUENCE {
      sigIdentifier   AlgorithmIdentifier,
      certIdentifier  AlgorithmIdentifier OPTIONAL }


   -- Object Identifiers

   id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
   id-pkix-ocsp                 OBJECT IDENTIFIER ::= { id-ad-ocsp }
   id-pkix-ocsp-basic           OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }
   id-pkix-ocsp-nonce           OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
   id-pkix-ocsp-crl             OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
   id-pkix-ocsp-response        OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
   id-pkix-ocsp-nocheck         OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }
   id-pkix-ocsp-archive-cutoff  OBJECT IDENTIFIER ::= { id-pkix-ocsp 6 }
   id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= { id-pkix-ocsp 7 }
   id-pkix-ocsp-pref-sig-algs   OBJECT IDENTIFIER ::= { id-pkix-ocsp 8 }
   id-pkix-ocsp-extended-revoke OBJECT IDENTIFIER ::= { id-pkix-ocsp 9 }

   END
   <CODE ENDS>

A.2.  OCSP in ASN.1 - 2008 Syntax

   <CODE BEGINS>
   OCSP-2024-08
        { iso(1) identified-organization(3) dod(6) internet(1)
          security(5) mechanisms(5) pkix(7) id-mod(0)
          id-mod-ocsp-2024-08(112) }

   DEFINITIONS EXPLICIT TAGS ::=
   BEGIN

   IMPORTS
       Extensions{}, EXTENSION
       FROM PKIX-CommonTypes-2009 -- From [RFC5912]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-mod-pkixCommon-02(57) }

       AlgorithmIdentifier{}, DIGEST-ALGORITHM,
       SIGNATURE-ALGORITHM, PUBLIC-KEY
       FROM AlgorithmInformation-2009 -- From [RFC5912]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-mod-algorithmInformation-02(58) }

       AuthorityInfoAccessSyntax, GeneralName,
       CrlEntryExtensions, CRLReason
       FROM PKIX1Implicit-2009 -- From [RFC5912]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-mod-pkix1-implicit-02(59) }

       Name, Certificate, CertificateSerialNumber,
       id-kp, id-ad-ocsp
       FROM PKIX1Explicit-2009 -- From [RFC5912]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7)
         id-mod(0) id-mod-pkix1-explicit-02(51) }

       sa-dsaWithSHA1, sa-rsaWithMD2,
       sa-rsaWithMD5, sa-rsaWithSHA1
       FROM PKIXAlgs-2009 -- From [RFC5912]
       { iso(1) identified-organization(3) dod(6)
       internet(1) security(5) mechanisms(5) pkix(7)
       id-mod(0) id-mod-pkix1-algorithms2008-02(56) } ;

   OCSPRequest ::= SEQUENCE {
      tbsRequest             TBSRequest,
      optionalSignature  [0] EXPLICIT Signature OPTIONAL }

   TBSRequest ::= SEQUENCE {
      version            [0] EXPLICIT Version DEFAULT v1,
      requestorName      [1] EXPLICIT GeneralName OPTIONAL,
      requestList             SEQUENCE OF Request,
      requestExtensions  [2] EXPLICIT Extensions
                             {{ re-ocsp-nonce | re-ocsp-response |
                             re-ocsp-preferred-signature-algorithms,
                             ... }} OPTIONAL }

   Signature ::= SEQUENCE {
      signatureAlgorithm   AlgorithmIdentifier
                               { SIGNATURE-ALGORITHM, {...}},
      signature            BIT STRING,
      certs            [0] EXPLICIT SEQUENCE OF
                           Certificate OPTIONAL }

   Version ::= INTEGER  {  v1(0) }

   Nonce ::= OCTET STRING (SIZE(1..128))

   Request ::= SEQUENCE {
      reqCert                      CertID,
      singleRequestExtensions  [0] EXPLICIT Extensions
                                   {{ re-ocsp-service-locator,
                                   ... }} OPTIONAL }

   CertID ::= SEQUENCE {
      hashAlgorithm   AlgorithmIdentifier
                          { DIGEST-ALGORITHM, {...}},
      issuerNameHash  OCTET STRING, -- Hash of issuer's DN
      issuerKeyHash   OCTET STRING, -- Hash of issuer's public key
      serialNumber    CertificateSerialNumber }

   OCSPResponse ::= SEQUENCE {
     responseStatus       OCSPResponseStatus,
     responseBytes    [0] EXPLICIT ResponseBytes OPTIONAL }

   OCSPResponseStatus ::= ENUMERATED {
      successful        (0), -- Response has valid confirmations
      malformedRequest  (1), -- Illegal confirmation request
      internalError     (2), -- Internal error in issuer
      tryLater          (3), -- Try again later
                             -- (4) is not used
      sigRequired       (5), -- Must sign the request
      unauthorized      (6)  -- Request unauthorized
   }

   RESPONSE ::= TYPE-IDENTIFIER

   ResponseSet RESPONSE ::= { basicResponse, ... }

   ResponseBytes ::= SEQUENCE {
      responseType  RESPONSE.&id ({ResponseSet}),
      response      OCTET STRING (CONTAINING RESPONSE.
                        &Type({ResponseSet}{@responseType}))}

   basicResponse RESPONSE ::=
      { BasicOCSPResponse IDENTIFIED BY id-pkix-ocsp-basic }

   BasicOCSPResponse ::= SEQUENCE {
     tbsResponseData      ResponseData,
     signatureAlgorithm   AlgorithmIdentifier
                              { SIGNATURE-ALGORITHM,
                                  { sa-dsaWithSHA1 |
                                    sa-rsaWithSHA1 |
                                    sa-rsaWithMD5  |
                                    sa-rsaWithMD2,
                                    ... }},
     signature            BIT STRING,
     certs            [0] EXPLICIT SEQUENCE OF
                          Certificate OPTIONAL }

   ResponseData ::= SEQUENCE {
     version             [0] EXPLICIT Version DEFAULT v1,
     responderID             ResponderID,
     producedAt              GeneralizedTime,
     responses               SEQUENCE OF SingleResponse,
     responseExtensions  [1] EXPLICIT Extensions
                                 {{ re-ocsp-nonce |
                                    re-ocsp-extended-revoke,
                                    ... }} OPTIONAL }

   ResponderID ::= CHOICE {
     byName   [1] Name,
     byKey    [2] KeyHash }

   KeyHash ::= OCTET STRING
               -- SHA-1 hash of responder's public key
               -- (excluding the tag and length and number
               -- of unused bits)

   SingleResponse ::= SEQUENCE {
     certID                CertID,
     certStatus            CertStatus,
     thisUpdate            GeneralizedTime,
     nextUpdate        [0] EXPLICIT GeneralizedTime OPTIONAL,
     singleExtensions  [1] EXPLICIT Extensions
                           {{ re-ocsp-crl |
                              re-ocsp-archive-cutoff |
                              CrlEntryExtensions,
                              ... }} OPTIONAL }

   CertStatus ::= CHOICE {
      good     [0] IMPLICIT NULL,
      revoked  [1] IMPLICIT RevokedInfo,
      unknown  [2] IMPLICIT UnknownInfo }

   RevokedInfo ::= SEQUENCE {
      revocationTime        GeneralizedTime,
      revocationReason  [0] EXPLICIT CRLReason OPTIONAL }

   UnknownInfo ::= NULL

   ArchiveCutoff ::= GeneralizedTime

   AcceptableResponses ::= SEQUENCE OF RESPONSE.&id({ResponseSet})

   ServiceLocator ::= SEQUENCE {
      issuer    Name,
      locator   AuthorityInfoAccessSyntax }

   CrlID ::= SEQUENCE {
      crlUrl   [0] EXPLICIT IA5String OPTIONAL,
      crlNum   [1] EXPLICIT INTEGER OPTIONAL,
      crlTime  [2] EXPLICIT GeneralizedTime OPTIONAL }

   PreferredSignatureAlgorithms ::= SEQUENCE OF
                                    PreferredSignatureAlgorithm

   PreferredSignatureAlgorithm ::= SEQUENCE {
      sigIdentifier  AlgorithmIdentifier
                         { SIGNATURE-ALGORITHM, {...} },
      certIdentifier AlgorithmIdentifier {PUBLIC-KEY, {...}}
                         OPTIONAL }


   -- Certificate Extensions

   ext-ocsp-nocheck EXTENSION ::= {
       SYNTAX NULL IDENTIFIED BY id-pkix-ocsp-nocheck }


   -- Request Extensions

   re-ocsp-nonce EXTENSION ::= {
       SYNTAX Nonce IDENTIFIED BY id-pkix-ocsp-nonce }

   re-ocsp-response EXTENSION ::= {
       SYNTAX AcceptableResponses IDENTIFIED BY
       id-pkix-ocsp-response }

   re-ocsp-service-locator EXTENSION ::= {
       SYNTAX ServiceLocator IDENTIFIED BY
       id-pkix-ocsp-service-locator }

   re-ocsp-preferred-signature-algorithms EXTENSION ::= {
       SYNTAX PreferredSignatureAlgorithms IDENTIFIED BY
       id-pkix-ocsp-pref-sig-algs  }


   -- Response Extensions

   re-ocsp-crl EXTENSION ::= {
       SYNTAX CrlID IDENTIFIED BY id-pkix-ocsp-crl }

   re-ocsp-archive-cutoff EXTENSION ::= {
       SYNTAX ArchiveCutoff IDENTIFIED BY
       id-pkix-ocsp-archive-cutoff }

   re-ocsp-extended-revoke EXTENSION ::= {
       SYNTAX NULL IDENTIFIED BY id-pkix-ocsp-extended-revoke }


   -- Object Identifiers

   id-kp-OCSPSigning            OBJECT IDENTIFIER ::= { id-kp 9 }
   id-pkix-ocsp                 OBJECT IDENTIFIER ::= id-ad-ocsp
   id-pkix-ocsp-basic           OBJECT IDENTIFIER ::= { id-pkix-ocsp 1 }
   id-pkix-ocsp-nonce           OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
   id-pkix-ocsp-crl             OBJECT IDENTIFIER ::= { id-pkix-ocsp 3 }
   id-pkix-ocsp-response        OBJECT IDENTIFIER ::= { id-pkix-ocsp 4 }
   id-pkix-ocsp-nocheck         OBJECT IDENTIFIER ::= { id-pkix-ocsp 5 }
   id-pkix-ocsp-archive-cutoff  OBJECT IDENTIFIER ::= { id-pkix-ocsp 6 }
   id-pkix-ocsp-service-locator OBJECT IDENTIFIER ::= { id-pkix-ocsp 7 }
   id-pkix-ocsp-pref-sig-algs   OBJECT IDENTIFIER ::= { id-pkix-ocsp 8 }
   id-pkix-ocsp-extended-revoke OBJECT IDENTIFIER ::= { id-pkix-ocsp 9 }

   END
   <CODE ENDS>

Acknowledgements

   The authors of this document thank Mohit Sahni for his work to
   produce [RFC8954].

   The authors also thank Russ Housley, Corey Bonnell, Michael StJohns,
   Tomas Gustavsson, and Carl Wallace for their feedback and
   suggestions.

Author's Address

   Himanshu Sharma (editor)
   Netskope Inc
   2445 Augustine Dr 3rd floor
   Santa Clara, California 95054
   United States of America
   Email: himanshu@netskope.com
   URI:   www.netskope.com