draft-ietf-lamps-ocsp-nonce-05.txt   rfc8954.txt 
LAMPS M. Sahni, Ed. Internet Engineering Task Force (IETF) M. Sahni, Ed.
Internet-Draft Palo Alto Networks Request for Comments: 8954 Palo Alto Networks
Updates: 6960 (if approved) September 10, 2020 Updates: 6960 November 2020
Intended status: Standards Track Category: Standards Track
Expires: March 14, 2021 ISSN: 2070-1721
OCSP Nonce Extension Online Certificate Status Protocol (OCSP) Nonce Extension
draft-ietf-lamps-ocsp-nonce-05
Abstract Abstract
This document specifies the updated format of the Nonce extension in This document specifies the updated format of the Nonce extension in
the Online Certificate Status Protocol (OCSP) request and response the Online Certificate Status Protocol (OCSP) request and response
messages. OCSP is used to check the status of a certificate and the messages. OCSP is used to check the status of a certificate, and the
Nonce extension is used to cryptographically bind an OCSP response Nonce extension is used to cryptographically bind an OCSP response
message to a particular OCSP request message. This document updates message to a particular OCSP request message. This document updates
RFC 6960. RFC 6960.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on March 14, 2021. 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/rfc8954.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology
2. OCSP Extensions . . . . . . . . . . . . . . . . . . . . . . . 2 2. OCSP Extensions
2.1. Nonce Extension . . . . . . . . . . . . . . . . . . . . . 3 2.1. Nonce Extension
3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations
3.1. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Replay Attack
3.2. Nonce Collision . . . . . . . . . . . . . . . . . . . . . 4 3.2. Nonce Collision
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations
5. Changes to Appendix B. of RFC 6960 . . . . . . . . . . . . . 4 5. Changes to Appendix B of RFC 6960
5.1. Changes to Appendix B.1. OCSP in ASN.1 - 1998 Syntax . . 4 5.1. Changes to Appendix B.1 OCSP in ASN.1 - 1998 Syntax
5.2. Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax . . . 5 5.2. Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. References
6.1. Normative References . . . . . . . . . . . . . . . . . . 5 6.1. Normative References
6.2. Informative References . . . . . . . . . . . . . . . . . 5 6.2. Informative References
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address
1. Introduction 1. Introduction
This document updates the usage and format of the Nonce extension This document updates the usage and format of the Nonce extension in
used in OCSP request and response messages. This extension was OCSP request and response messages. This extension was previously
previously defined in section 4.4.1 of [RFC6960]. [RFC6960] does not defined in Section 4.4.1 of [RFC6960]. [RFC6960] does not mention
mention any minimum and maximum length of nonce in the Nonce any minimum or maximum length of the nonce in the Nonce extension.
extension. Lacking limits on the length of nonce in the Nonce Lacking limits on the length of the nonce in the Nonce extension,
extension, an OCSP responders that follow [RFC6960] may be vulnerable OCSP responders that follow [RFC6960] may be vulnerable to various
to various attacks like Denial of Service attacks [RFC4732], chosen attacks, like Denial-of-Service attacks [RFC4732] or chosen-prefix
prefix attacks to get a desired signature, and possible evasions attacks (to get a desired signature), and possible evasions using the
using the Nonce extension data. This document specifies a lower Nonce extension data. This document specifies a lower limit of 1 and
limit of 1 and an upper limit of 32 to the length of nonce in the an upper limit of 32 for the length of the nonce in the Nonce
Nonce extension. This document updates [RFC6960]. extension. This document updates [RFC6960].
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. OCSP Extensions 2. OCSP Extensions
The message format for OCSP request and response is defined in The message formats for OCSP requests and responses are defined in
[RFC6960]. [RFC6960] also defines the standard extensions for OCSP [RFC6960]. [RFC6960] also defines the standard extensions for OCSP
messages based on the extension model employed in X.509 version 3 messages based on the extension model employed in X.509 version 3
certificates (see [RFC5280]). This document only specifies the new certificates (see [RFC5280]). This document only specifies the new
format for Nonce extension and does not change specification of any format for the Nonce extension and does not change the specifications
of the other standard extensions defined in [RFC6960]. of any of the other standard extensions defined in [RFC6960].
2.1. Nonce Extension 2.1. Nonce Extension
This section replaces the entirety of the Section 4.4.1 of [RFC6960] This section replaces the entirety of Section 4.4.1 of [RFC6960],
which describes the OCSP Nonce extension. which describes the OCSP Nonce extension.
The nonce cryptographically binds a request and a response to prevent The nonce cryptographically binds a request and a response to prevent
replay attacks. The nonce is included as one of the replay attacks. The nonce is included as one of the
requestExtensions in requests, while in responses it would be requestExtensions in requests; in responses, it would be included as
included as one of the responseExtensions. In both the request and one of the responseExtensions. In both the request and the response,
the response, the nonce will be identified by the object identifier the nonce will be identified by the object identifier id-pkix-ocsp-
id-pkix-ocsp-nonce, while the extnValue is the value of the nonce. nonce, while the extnValue is the value of the nonce. If the Nonce
If Nonce extension is present then the length of nonce MUST be at extension is present, then the length of the nonce MUST be at least 1
least 1 octet and can be up to 32 octets. octet and can be up to 32 octets.
A server MUST reject any OCSP request having a nonce in the Nonce A server MUST reject any OCSP request that has a nonce in the Nonce
extension with length of 0 octets or more than 32 octets with the extension with a length of either 0 octets or more than 32 octets
malformedRequest OCSPResponseStatus as described in section 4.2.1 of with the malformedRequest OCSPResponseStatus, as described in
[RFC6960]. Section 4.2.1 of [RFC6960].
The value of the nonce MUST be generated using a cryptographically The value of the nonce MUST be generated using a cryptographically
strong pseudorandom number generator (see [RFC4086]). The minimum strong pseudorandom number generator (see [RFC4086]). The minimum
nonce length of 1 octet is defined to provide backward compatibility nonce length of 1 octet is defined to provide backward compatibility
with older clients that follow [RFC6960]. Newer OCSP clients that with older clients that follow [RFC6960]. Newer OCSP clients that
support this document MUST use a length of 32 octets for the nonce in support this document MUST use a length of 32 octets for the nonce in
Nonce extension. OCSP responders MUST accept lengths of at least 16 the Nonce extension. OCSP responders MUST accept lengths of at least
octets, and MAY choose to ignore the Nonce extension for requests 16 octets and MAY choose to ignore the Nonce extension for requests
where the length of the nonce is less than 16 octets where the length of the nonce is less than 16 octets.
id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp } id-pkix-ocsp OBJECT IDENTIFIER ::= { id-ad-ocsp }
id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 } id-pkix-ocsp-nonce OBJECT IDENTIFIER ::= { id-pkix-ocsp 2 }
Nonce ::= OCTET STRING(SIZE(1..32)) Nonce ::= OCTET STRING(SIZE(1..32))
3. Security Considerations 3. Security Considerations
The security considerations of OCSP, in general, are described in The security considerations of OCSP, in general, are described in
[RFC6960]. During the interval in which the previous OCSP response [RFC6960]. During the interval in which the previous OCSP response
for a certificate is not expired but the responder has a changed 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 status for that certificate, a copy of that OCSP response can be used
to indicate that the status of the certificate is still valid. to indicate that the status of the certificate is still valid.
Including client's Nonce value in the OCSP response makes sure that 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 the response is the latest response from the server and not an old
copy. copy.
3.1. Replay Attack 3.1. Replay Attack
The Nonce extension is used to avoid replay attacks. Since the OCSP The Nonce extension is used to avoid replay attacks. Since the OCSP
responder may choose to not send the Nonce extension in 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 response even if the client has sent the Nonce extension in the
request [RFC5019], an on-path attacker can intercept the OCSP request request [RFC5019], an on-path attacker can intercept the OCSP request
and respond with an earlier response from the server without the and respond with an earlier response from the server without the
Nonce extension. This can be mitigated by configuring the server to Nonce extension. This can be mitigated by configuring the server to
use a short time interval between the thisUpdate and nextUpdate use a short time interval between the thisUpdate and nextUpdate
fields in the OCSP response. fields in the OCSP response.
3.2. Nonce Collision 3.2. Nonce Collision
If the value of nonce used by a client in OCSP request is If the value of the nonce used by a client in the OCSP request is
predictable, then an attacker may prefetch responses with the predictable, then an attacker may prefetch responses with the
predicted nonce and can replay them, thus defeating the purpose of predicted nonce and can replay them, thus defeating the purpose of
using nonce. Therefore the value of Nonce extension in the OCSP using the nonce. Therefore, the value of the Nonce extension in the
request MUST contain cryptographically strong randomness and MUST be OCSP request MUST contain cryptographically strong randomness and
freshly generated at the time of creating the OCSP request. Also if MUST be freshly generated at the time of the creation of the OCSP
the length of nonce is too small e.g. 1 octet then an on-path request. Also, if the length of the nonce is too small (e.g., 1
attacker can prefetch responses with all the possible values of nonce octet), then an on-path attacker can prefetch responses with all the
and replay a matching nonce. possible values of the nonce and replay a matching nonce.
4. IANA Considerations 4. IANA Considerations
This document does not call for any IANA actions. This document has no IANA actions.
5. Changes to Appendix B. of RFC 6960 5. Changes to Appendix B of RFC 6960
This section updates the ASN.1 definitions of the OCSP Nonce This section updates the ASN.1 definitions of the OCSP Nonce
extension in Appendix B.1 and Appendix B.2 of [RFC6960] The extension in Appendices B.1 and B.2 of [RFC6960]. Appendix B.1
Appendix B.1 defines OCSP using ASN.1 - 1998 Syntax and Appendix B.2 defines OCSP using ASN.1 - 1998 Syntax; Appendix B.2 defines OCSP
defines OCSP using ASN.1 - 2008 Syntax using ASN.1 - 2008 Syntax.
5.1. Changes to Appendix B.1. OCSP in ASN.1 - 1998 Syntax 5.1. Changes to Appendix B.1 OCSP in ASN.1 - 1998 Syntax
OLD Syntax: OLD Syntax:
The definition of OCSP Nonce Extension is not provided in The definition of OCSP Nonce extension is not provided in
Appendix B.1 of [RFC6960] for the ASN.1 - 1998 Syntax. Appendix B.1 of [RFC6960] for the ASN.1 - 1998 Syntax.
NEW Syntax: NEW Syntax:
Nonce ::= OCTET STRING(SIZE(1..32)) Nonce ::= OCTET STRING(SIZE(1..32))
5.2. Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax 5.2. Changes to Appendix B.2 OCSP in ASN.1 - 2008 Syntax
OLD Syntax: OLD Syntax:
skipping to change at page 5, line 24 skipping to change at line 205
re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING(SIZE(1..32)) re-ocsp-nonce EXTENSION ::= { SYNTAX OCTET STRING(SIZE(1..32))
IDENTIFIED BY id-pkix-ocsp-nonce } IDENTIFIED BY id-pkix-ocsp-nonce }
6. References 6. References
6.1. Normative References 6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <https://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>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP", Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013, RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>. <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 6.2. Informative References
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>. <https://www.rfc-editor.org/info/rfc4086>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732, Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006, DOI 10.17487/RFC4732, December 2006,
skipping to change at page 6, line 20 skipping to change at line 245
[RFC5019] Deacon, A. and R. Hurst, "The Lightweight Online [RFC5019] Deacon, A. and R. Hurst, "The Lightweight Online
Certificate Status Protocol (OCSP) Profile for High-Volume Certificate Status Protocol (OCSP) Profile for High-Volume
Environments", RFC 5019, DOI 10.17487/RFC5019, September Environments", RFC 5019, DOI 10.17487/RFC5019, September
2007, <https://www.rfc-editor.org/info/rfc5019>. 2007, <https://www.rfc-editor.org/info/rfc5019>.
Author's Address Author's Address
Mohit Sahni (editor) Mohit Sahni (editor)
Palo Alto Networks Palo Alto Networks
3000 Tannery Way 3000 Tannery Way
Santa Clara, CA 95054 Santa Clara, CA 95054
US United States of America
Email: msahni@paloaltonetworks.com Email: msahni@paloaltonetworks.com
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