Internet Engineering Task Force H. Sharma, Ed. Internet-Draft Netskope Inc Updates: 8954 (if approved) 1 January 2024 Intended status: Standards Track Expires: 4 July 2024 Online Certificate Status Protocol (OCSP) Nonce Extension draft-hsharma-lamps-ocsp-nonce-update-02 Abstract This document updates the Nonce extension section of RFC-8954. Nonce extension is an optional extension for Online Certificate Status Protocol (OCSP) request and response messages. OCSP is used for checking the status of a certificate, and the Nonce extension is used to cryptographically bind an OCSP response message to a particular OCSP request message. This document updates OCSP responder behavior for the OCSP requests that have Nonce length longer than the maximum length limit defined in [RFC8954], So that it won't impact the existing OCSP clients. This update removes the disparity between the behavior of responders that supports or ignores Nonce. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 4 July 2024. 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 Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Sharma Expires 4 July 2024 [Page 1] Internet-Draft draft-hsharma-lamps-ocsp-nonce-update-02 January 2024 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. OCSP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Nonce Extension . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 3.1. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction This document updates the OCSP server behavior for the OCSP requests, which have Nonce length that exceeds the maximum length limit defined in [RFC8954]. This extension was previously defined in Section 4.4.1 of [RFC6960] and updated in [RFC8954]. [RFC6960] defines OCSP extensions as an optional extension that provides the freedom to OCSP responders to ignore the Nonce extension regardless of its existence or value in OCSP request, whereas [RFC8954] language directs the OCSP responders to MUST take action based on the Nonce value in OCSP requests. For example, [RFC8954] directs OCSP responder to MUST reject all the OCSP requests that have NONCE longer than 32 OCTET string and MUST respond with the malformedRequest OCSPResponseStatus. The OCSP responder SHOULD be able to ignore the Nonce values (valid or invalid) as it is an optional extension. Ignoring the longer Nonce value helps the OCSP responder achieve better backward compatibility, as it won't impact the existing OCSP clients that have already been using longer Nonce values. This document updates the [RFC8954] by replacing the section 2.1 of [RFC8954]. This document updates the OCSP responder's behavior in case of Nonce length presented in OCSP request exceeds the maximum Nonce length of 32 OCTETS. This update also provides an example of Nonce value in OCTET string. Sharma Expires 4 July 2024 [Page 2] Internet-Draft draft-hsharma-lamps-ocsp-nonce-update-02 January 2024 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 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 enforce the minimum and maximum length for the Nonce value. This document adds flexibility to OCSP servers to either reject or ignore the OCSP request that has Nonce longer than 32 OCTETS. This document doesn't change the length requirement for Nonce value and does not change the specifications of any of the other standard extensions defined in [RFC6960] or [RFC8954]. 2.1. Nonce Extension This section replaces the entirety of Section 2.1 of [RFC8954], which describes the OCSP 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 would be included as one of the responseExtensions.In both the request and the response, the Nonce will be identified by the object identifier id-pkix-ocsp-Nonce, while the extnValue is the value of the Nonce. If the Nonce extension is present, then the length of the Nonce MUST be at least 1 octet and can be up to 32 octets. A server MUST either reject any OCSP request that has a Nonce in the Nonce extension with a length of either 0 octets or more than 32 octets with the malformedRequest OCSPResponseStatus, as described in Section 4.2.1 of [RFC6960], or the server MAY choose to ignore the Nonce extension with a length of more than 32 octets and in that case MUST leave out the Nonce extension in the response. 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 clients that follow [RFC6960]. Sharma Expires 4 July 2024 [Page 3] Internet-Draft draft-hsharma-lamps-ocsp-nonce-update-02 January 2024 id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp } id-pkix-ocsp-Nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 } Nonce ::= OCTET STRING(SIZE(1..32)) Raw Nonce Example: 1FA16041C0E2D739898EC69972A4B967DFD3488148E6DA61CF3AF2DC32383383 OCSP Nonce Octet String: 04201FA16041C0E2D739898EC69972A4B967DFD3488148E6DA61CF3AF2DC32383383 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 client's nonce value in the OCSP response makes sure that the response is the latest 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 client 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 This memo includes no request to IANA. 5. Security Considerations This document should not affect the security of the Internet. 6. References 6.1. Normative References Sharma Expires 4 July 2024 [Page 4] Internet-Draft draft-hsharma-lamps-ocsp-nonce-update-02 January 2024 [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, . [RFC8954] Sahni, M., Ed., "Online Certificate Status Protocol (OCSP) Nonce Extension", RFC 8954, DOI 10.17487/RFC8954, November 2020, . [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, . [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . 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 Sharma Expires 4 July 2024 [Page 5]