LAMPS

Internet Engineering Task Force (IETF)                     M. Sahni, Ed.
Internet-Draft
Request for Comments: 8954                            Palo Alto Networks
Updates: 6960 (if approved)                           September 10,                                              November 2020
Intended status:
Category: Standards Track
Expires: March 14, 2021

                          OCSP
ISSN: 2070-1721

       Online Certificate Status Protocol (OCSP) Nonce Extension
                     draft-ietf-lamps-ocsp-nonce-05

Abstract

   This document specifies the updated format of the Nonce extension in
   the Online Certificate Status Protocol (OCSP) request and response
   messages.  OCSP is used to check the status of a certificate certificate, and the
   Nonce extension is used to cryptographically bind an OCSP response
   message to a particular OCSP request message.  This document updates
   RFC 6960.

Status of This Memo

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   This Internet-Draft will expire on March 14, 2021.
   https://www.rfc-editor.org/info/rfc8954.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  OCSP Extensions . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Nonce Extension . . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
     3.1.  Replay Attack . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Nonce Collision . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Changes to Appendix B. B of RFC 6960  . . . . . . . . . . . . .   4
     5.1.  Changes to Appendix B.1. B.1 OCSP in ASN.1 - 1998 Syntax  . .   4
     5.2.  Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This document updates the usage and format of the Nonce extension
   used in
   OCSP request and response messages.  This extension was previously
   defined in section Section 4.4.1 of [RFC6960].  [RFC6960] does not mention
   any minimum and or maximum length of the nonce in the Nonce extension.
   Lacking limits on the length of the nonce in the Nonce extension, an
   OCSP responders that follow [RFC6960] may be vulnerable to various attacks
   attacks, like Denial of Service Denial-of-Service attacks [RFC4732], chosen
   prefix [RFC4732] or chosen-prefix
   attacks to (to get a desired signature, signature), and possible evasions using the
   Nonce extension data.  This document specifies a lower limit of 1 and
   an upper limit of 32 to for the length of the nonce in the Nonce
   extension.  This document updates [RFC6960].

1.1.  Terminology

   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 format formats for OCSP request requests and response is responses are defined in
   [RFC6960].  [RFC6960] also defines the standard extensions for OCSP
   messages based on the extension model employed in X.509 version 3
   certificates (see [RFC5280]).  This document only specifies the new
   format for the Nonce extension and does not change specification the specifications
   of any of the other standard extensions defined in [RFC6960].

2.1.  Nonce Extension

   This section replaces the entirety of the Section 4.4.1 of [RFC6960] [RFC6960],
   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, while requests; in responses 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, id-pkix-ocsp-
   nonce, while the extnValue is the value of the nonce.  If the Nonce
   extension is present present, then the length of the nonce MUST be at least 1
   octet and can be up to 32 octets.

   A server MUST reject any OCSP request having that has a nonce in the Nonce
   extension with a length of either 0 octets or more than 32 octets
   with the malformedRequest OCSPResponseStatus OCSPResponseStatus, as described in section
   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 clients that follow [RFC6960].  Newer OCSP clients that
   support this document MUST use a length of 32 octets for the nonce in
   the Nonce extension.  OCSP responders MUST accept lengths of at least
   16
   octets, octets and MAY choose to ignore the Nonce extension for requests
   where the length of the nonce is less than 16 octets octets.

      id-pkix-ocsp           OBJECT IDENTIFIER ::= { id-ad-ocsp }
      id-pkix-ocsp-nonce     OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }

      Nonce ::= OCTET STRING(SIZE(1..32))

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 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 to 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.

3.2.  Nonce Collision

   If the value of the nonce used by a client in the OCSP request is
   predictable, then an attacker may prefetch responses with the
   predicted nonce and can replay them, thus defeating the purpose of
   using the nonce.  Therefore  Therefore, the value of the Nonce extension in the
   OCSP request MUST contain cryptographically strong randomness and
   MUST be freshly generated at the time of creating the creation of the OCSP
   request.  Also  Also, if the length of the nonce is too small e.g. (e.g., 1 octet
   octet), then an on-path attacker can prefetch responses with all the
   possible values of the nonce and replay a matching nonce.

4.  IANA Considerations

   This document does not call for any has no IANA actions.

5.  Changes to Appendix B. B of RFC 6960

   This section updates the ASN.1 definitions of the OCSP Nonce
   extension in Appendix Appendices B.1 and Appendix B.2 of [RFC6960] The [RFC6960].  Appendix B.1
   defines OCSP using ASN.1 - 1998 Syntax and Syntax; Appendix B.2 defines OCSP
   using ASN.1 - 2008 Syntax Syntax.

5.1.  Changes to Appendix B.1. B.1 OCSP in ASN.1 - 1998 Syntax

   OLD Syntax:

   The definition of OCSP Nonce Extension extension is not provided in
   Appendix B.1 of [RFC6960] for the ASN.1 - 1998 Syntax.

   NEW Syntax:

       Nonce ::= OCTET STRING(SIZE(1..32))

5.2.  Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax

   OLD Syntax:

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

   NEW Syntax:

       re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING(SIZE(1..32))
           IDENTIFIED BY id-pkix-ocsp-nonce }

6.  References

6.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", DOI 10.17487/RFC8174, RFC 8174, BCP 14,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.
              <https://www.rfc-editor.org/info/rfc2119>.

   [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>.

6.2.  Informative References

   [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>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732,
              DOI 10.17487/RFC4732, December 2006,
              <https://www.rfc-editor.org/info/rfc4732>.

   [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>.

Author's Address

   Mohit Sahni (editor)
   Palo Alto Networks
   3000 Tannery Way
   Santa Clara, CA 95054
   US
   United States of America

   Email: msahni@paloaltonetworks.com