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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	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		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.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	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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