RFC 9654 | OCSP Nonce Extension | August 2024 |
Sharma | Standards Track | [Page] |
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 updates the maximum allowed length of Nonce to 128 octets. This document also modifies the Nonce section to clearly define the encoding format and values distinctively for easier implementation and understanding. This document obsoletes RFC 8954 and provides updated ASN.1 modules for OCSP, updates RFC 6960.¶
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 (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 Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
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.¶
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.¶
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 this section 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].¶
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 : } : }¶
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.¶
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.¶
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 |
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.¶
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 -- PKIX Certificate Extensions AuthorityInfoAccessSyntax, CRLReason, GeneralName FROM PKIX1Implicit88 { 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 { 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 of [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¶
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, CertificateSerialNumber, id-kp, id-ad-ocsp, Certificate 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 fields) 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¶
The authors of this document thank Mohit Sahni for his work to produce [RFC8954].¶
The authors also thank Russ Housley, Corey Bonnell, Michael StJohns, and Carl Wallace for their feedback and suggestions.¶