draft-ietf-lamps-ocsp-nonce-02.txt		draft-ietf-lamps-ocsp-nonce-03.txt
	LAMPS M. Sahni, Ed.		LAMPS M. Sahni, Ed.
	Internet-Draft Palo Alto Networks		Internet-Draft Palo Alto Networks
	Updates: 6960 (if approved) May 15, 2020		Updates: 6960 (if approved) August 14, 2020
	Intended status: Standards Track		Intended status: Standards Track
	Expires: November 16, 2020		Expires: February 15, 2021
	OCSP Nonce Extension		OCSP Nonce Extension
	draft-ietf-lamps-ocsp-nonce-02		draft-ietf-lamps-ocsp-nonce-03
	Abstract		Abstract
	This document specifies the updated format of the Nonce extension in		This document specifies the updated format of the Nonce extension in
	Online Certificate Status Protocol (OCSP) request and response		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 in the OCSP request and response messages to		Nonce extension is used in the OCSP request and response messages to
	avoid replay attacks. This document updates the RFC 6960		avoid replay attacks. This document updates the RFC 6960
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 35 ¶		skipping to change at page 1, line 35 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on November 16, 2020.		This Internet-Draft will expire on February 15, 2021.
	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
	skipping to change at page 2, line 18 ¶		skipping to change at page 2, line 18 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
	2. OCSP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3		2. OCSP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3
	2.1. Nonce Extension . . . . . . . . . . . . . . . . . . . . . 3		2.1. Nonce Extension . . . . . . . . . . . . . . . . . . . . . 3
	3. Security Considerations . . . . . . . . . . . . . . . . . . . 4		3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	3.1. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 4		3.1. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 4
	3.2. Nonce Collision . . . . . . . . . . . . . . . . . . . . . 4		3.2. Nonce Collision . . . . . . . . . . . . . . . . . . . . . 4
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	5. Changes to Appendix B. of RFC 6960 . . . . . . . . . . . . . 4		5. Changes to Appendix B. of RFC 6960 . . . . . . . . . . . . . 4
	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
	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 . . . 5
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	6.1. Normative References . . . . . . . . . . . . . . . . . . 5		6.1. Normative References . . . . . . . . . . . . . . . . . . 5
	6.2. Informative References . . . . . . . . . . . . . . . . . 5		6.2. Informative References . . . . . . . . . . . . . . . . . 6
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
	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
	used in OCSP request and response messages. This extension was		used in OCSP request and response messages. This extension was
	previously defined in section 4.1.1 of [RFC6960]. The [RFC6960] does		previously defined in section 4.1.1 of [RFC6960]. The [RFC6960] does
	not mention any minimum and maximum length of the nonce extension.		not mention any minimum and maximum length of the nonce extension.
	Due to not having an upper or lower limit of the length of the Nonce		Due to not having an upper or lower limit of the length of the Nonce
	extension, the OCSP responders that follow [RFC6960] may be		extension, the OCSP responders that follow [RFC6960] may be
	skipping to change at page 3, line 10 ¶		skipping to change at page 3, line 10 ¶
	"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 BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all		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 the OCSP request and response is defined in		The message format for the OCSP request and response is defined in
	the [RFC6960]. It also defines the standard extensions for OCSP		the [RFC6960]. It 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]). Following is the list of standard		certificates (see [RFC5280]). The following is a list of standard
	extensions that can be used in the OCSP messages by the OCSP		extensions that can be used in the OCSP messages by the OCSP
	responder and OCSP client.		responder and OCSP client.
	* Nonce		* Nonce
	* CRL References		* CRL References
	* Acceptable Response Types		* Acceptable Response Types
	* Archive Cutoff		* Archive Cutoff
	* CRL Entry Extensions		* CRL Entry Extensions
	* Service Locator		* Service Locator
	* Preferred Signature Algorithms		* Preferred Signature Algorithms
	* Extended Response Definition		* Extended Response Definition
	This document only specifies the new format for Nonce extension and		This document only specifies the new format for Nonce extension and
	does not change the specification of any of the other standard		does not change the specification of any of the other standard
	extensions.		extensions.
	2.1. Nonce Extension		2.1. Nonce Extension
	This section updates the Section 4.4.1 of [RFC6960] which describes		This section replaces the entirety of the Section 4.4.1 of [RFC6960]
	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, while in responses it would be
	included as one of the responseExtensions. In both the request and		included as one of the responseExtensions. In both the request and
	the response, the nonce will be identified by the object identifier		the response, the nonce will be identified by the object identifier
	id-pkix-ocsp-nonce, while the extnValue is the value of the nonce.		id-pkix-ocsp-nonce, while the extnValue is the value of the nonce.
	If Nonce extension is present then the length of nonce MUST be at		If Nonce extension is present then the length of nonce MUST be at
	least 1 octet and can be up to 32 octets.		least 1 octet and can be up to 32 octets.
	A server MUST reject any OCSP request having a Nonce extension with		A server MUST reject any OCSP request having a Nonce extension with
	length of more than 32 octets with the malformedRequest		length of more than 32 octets with the malformedRequest
	OCSPResponseStatus as described in section 4.2.1 of [RFC6960]		OCSPResponseStatus as described in section 4.2.1 of [RFC6960]
	The minimum nonce length of 1 octet is defined to provide the		The value of the nonce MUST be generated using a cryptographically
	backward compatibility with clients following [RFC6960]. However the		strong pseudorandom number generator. The OCSP clients SHOULD use a
	newer OCSP clients MUST use length of at least 16 octets for Nonce		length of 32 octets for the Nonce extension. The minimum nonce
	extension and the value of the nonce MUST be generated using a		length of 1 octet is defined to provide the backward compatibility
	cryptographically strong pseudorandom number generator.		with older clients following [RFC6960] however, the newer OCSP
			clients MUST use a length of at least 16 octets for Nonce extension.
			The OCSP responder MAY choose to ignore Nonce extension for the
			requests where length of the Nonce extension is less than 16 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))		Nonce ::= OCTET STRING(SIZE(1..32))
	3. Security Considerations		3. Security Considerations
	The security considerations of OCSP, in general, are described in the		The security considerations of OCSP, in general, are described in the
	[RFC6960]. The Nonce extension is used to avoid replay attacks		[RFC6960]. The Nonce extension is used to avoid replay attacks
	during the interval in which the previous OCSP response for a		during the interval in which the previous OCSP response for a
	certificate is not expired but the responder has a changed status for		certificate is not expired but the responder has a changed status for
	that certificate. Including client's Nonce value in the OCSP		that certificate. Including client's Nonce value in the OCSP
	response makes sure that the response is the latest response from the		response makes sure that the response is the latest response from the
	server and not an old copy.		server and not an old 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 to not 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], a man in the middle (MITM) entity can intercept		request [RFC5019], an on-path attacker can intercept the OCSP request
	the OCSP request and respond with an earlier response from the server		and respond with an earlier response from the server without the
	without the Nonce extension. This can be mitigated by the server		Nonce extension. This can be mitigated by configuring the server to
	using a closer nextUpdate value in the OCSP response.		use a short time interval between thisUpdate and nextUpdate fields in
			the OCSP response.
	3.2. Nonce Collision		3.2. Nonce Collision
	If the value of the nonce used by a client is not random enough, then		If the value of the nonce used by a client in OCSP request is not
	an attacker may prefetch responses with the predicted nonce and can		random enough, then an attacker may prefetch responses with the
	replay them, thus defeating the purpose of using nonce. Therefore		predicted nonce and can replay them, thus defeating the purpose of
	the client MUST use a nonce value that contains cryptographically		using nonce. Therefore the value of Nonce extension in the OCSP
	strong randomness and is freshly generated. Also if the length of		request MUST contain cryptographically strong randomness and MUST be
	the nonce is very small e.g. 1 octet then an attacker can prefetch		freshly generated at the time of creating the OCSP request. Also if
	responses with all the possible values of the nonce and replay a		the length of the nonce extension is too small e.g. 1 octet then an
	matching nonce. A client SHOULD use 32 octets for the nonce length.		on-path attacker can prefetch responses with all the 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 does not call for any 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 the Appendix B.1 and Appendix B.2 of the [RFC6960] The		extension in the Appendix B.1 and Appendix B.2 of the [RFC6960] The
	Appendix B.1 defines OCSP using ASN.1 - 1998 Syntax and Appendix B.2		Appendix B.1 defines OCSP using ASN.1 - 1998 Syntax and Appendix B.2
End of changes. 11 change blocks.
	26 lines changed or deleted		34 lines changed or added
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