Internet-Draft draft-hsharma-lamps-ocsp-nonce-05 November 2023
Sharma Expires 11 May 2024 [Page]
Internet Engineering Task Force
8954 (if approved)
Intended Status:
H. Sharma, Ed.
Netskope Inc

Online Certificate Status Protocol (OCSP) Nonce Extension


This document updates the Nonce extension section of RFC-8954. Nonce extension is a 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 RFC 8954.

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

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 11 May 2024.

Table of Contents

1. Introduction

This document updates the usage of the Nonce extension in OCSP request and response messages. This extension was previously defined in Section 4.4.1 of [RFC6960] and updated in [RFC8954]. [RFC6960] defines OCSP extensions as optional extension, and defines condition for different extension options. [RFC6960] Nonce extension is defined as an optional extension and 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 Nonce value in OCSP requests. For example it directs OCSP responder to MUST respond with the malformedRequest OCSPResponseStatus in case of zero or longer Nonce values.

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 OCSP responder to achieve the better backward compatibility as it wont impact the existing OCSP client that has already been sending longer Nonce values. This document updates the Nonce extension section of [RFC8954] by removing the instruction to OCSP responder to reject the OCSP response that violates the Nonce length requirment, provides an example of Nonce value and reinstate the backward compatibility while clearly differentiating the OCSP client and responder expectations.

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 minimum and maximum length for Nonce value. This document updates the Nonce extension section of [RFC8954] with clearly define the behavior of OCSP responder and client under precondition of support of Nonce extension while ignoring the OCSP request with longer Nonce length of 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 updates the 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.

OCSP client that supports Nonce extension MUST use the length of 32 octets. OCSP responder that supports the Nonce extension MUST support the Nonce value with minimum length of 16 octets to maximum length of 32 octets. OCSP responder MAY choose to ignore Nonces that are less than 16 octets or violates Nonce length defined in [RFC8954], and 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].

    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:

OCSP Nonce Octet String:

3. IANA Considerations

This memo includes no request to IANA.

4. Security Considerations

This document should not affect the security of the Internet.

5. References

5.1. Normative References

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, , <>.
Sahni, M., Ed., "Online Certificate Status Protocol (OCSP) Nonce Extension", RFC 8954, DOI 10.17487/RFC8954, , <>.
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, , <>.
Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, , <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.

Author's Address

Himanshu Sharma (editor)
Netskope Inc
2445 Augustine Dr 3rd floor
Santa Clara, California 95054
United States of America