< draft-ietf-lamps-documentsigning-eku-00.txt		draft-ietf-lamps-documentsigning-eku-01.txt >
	LAMPS Working Group T. Ito		LAMPS Working Group T. Ito
	Internet-Draft SECOM CO., LTD.		Internet-Draft SECOM CO., LTD.
	Intended status: Standards Track T. Okubo		Intended status: Standards Track T. Okubo
	Expires: 17 July 2022 DigiCert, Inc.		Expires: 3 September 2022 DigiCert, Inc.
	S. Turner		S. Turner
	sn3rd		sn3rd
	13 January 2022		2 March 2022
	General Purpose Extended Key Usage (EKU) for Document Signing X.509		General Purpose Extended Key Usage (EKU) for Document Signing X.509
	Certificates		Certificates
	draft-ietf-lamps-documentsigning-eku-00		draft-ietf-lamps-documentsigning-eku-01
	Abstract		Abstract
	[RFC5280] specifies several extended key usages for X.509		RFC 5280 specifies several extended key usages for X.509
	certificates. This document defines a general purpose document		certificates. This document defines a general purpose document
	signing extended key usage for X.509 public key certificates which		signing extended key usage for X.509 public key certificates which
	restricts the usage of the certificates for document signing.		restricts the usage of the certificates for document signing.
	About This Document		About This Document
	This note is to be removed before publishing as an RFC.		This note is to be removed before publishing as an RFC.
	Status information for this document may be found at		Status information for this document may be found at
	https://datatracker.ietf.org/doc/draft-ietf-lamps-documentsigning-		https://datatracker.ietf.org/doc/draft-ietf-lamps-documentsigning-
	skipping to change at page 2, line 10 ¶		skipping to change at page 2, line 10 ¶
	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 17 July 2022.		This Internet-Draft will expire on 3 September 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2022 IETF Trust and the persons identified as the		Copyright (c) 2022 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 36 ¶		skipping to change at page 2, line 36 ¶
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3		2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
	3. Extended Key usage for DocumentSigning . . . . . . . . . . . 3		3. Extended Key usage for DocumentSigning . . . . . . . . . . . 3
	3.1. Extended Key Usage Values for Document Signing . . . . . 4		3.1. Extended Key Usage Values for Document Signing . . . . . 4
	4. Using the Document Signing EKU in a Certificate . . . . . . . 4		4. Using the Document Signing EKU in a Certificate . . . . . . . 4
	5. Implications for a Certification Authority . . . . . . . . . 5		5. Implications for a Certification Authority . . . . . . . . . 5
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 6		6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	8. Normative References . . . . . . . . . . . . . . . . . . . . 6		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
			8.1. Normative References . . . . . . . . . . . . . . . . . . 6
			8.2. Informative References . . . . . . . . . . . . . . . . . 7
	Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 7		Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 7
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7		Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	[RFC5280] specifies several extended key usages for X.509		[RFC5280] specifies several extended key usages for X.509
	certificates. In addition, several extended key usage had been		certificates. In addition, several extended key usage had been added
	added[RFC7299] as public OID under the IANA repository. While usage		[RFC7299] as public Object Identifier (OID) under the IANA
	of any extended key usage is bad practice for publicly trusted		repository. While usage of any extended key usage is bad practice
	certificates, there are no public and general extended key usage		for publicly trusted certificates, there are no public and general
	explicitly assigned for Document Signing certificates. The current		extended key usage explicitly assigned for Document Signing
	practice is to use id-kp-emailProtection, id-kp-codeSigning or vendor		certificates. The current practice is to use id-kp-emailProtection,
	defined Object ID for general document signing purposes.		id-kp-codeSigning or vendor defined OID for general document signing
			purposes.
	In circumstances where code signing and S/MIME certificates are also		In circumstances where code signing and S/MIME certificates are also
	widely used for document signing, the technical or policy changes		widely used for document signing, the technical or policy changes
	that are made to code signing and S/MIME certificates may cause		that are made to code signing and S/MIME certificates may cause
	unexpected behaviors or have an adverse impact such as decreased		unexpected behaviors or have an adverse impact such as decreased
	cryptographic agility on the document signing ecosystem and vice		cryptographic agility on the document signing ecosystem and vice
	versa.		versa.
	There is no issue if the vendor defined OIDs are used in a PKI (or a		There is no issue if the vendor defined OIDs are used in a PKI (or a
	trust program) governed by the vendor. However, if the OID is used		trust program) governed by the vendor. However, if the OID is used
	skipping to change at page 3, line 26 ¶		skipping to change at page 3, line 27 ¶
	they might want to ask that vendor about use of the certificate,		they might want to ask that vendor about use of the certificate,
	however, the vendor may not know about the particular use. - If the		however, the vendor may not know about the particular use. - If the
	issuance of the cert is not under the control of the OID owner, there		issuance of the cert is not under the control of the OID owner, there
	is no way for the OID owner to know what the impact will be if any		is no way for the OID owner to know what the impact will be if any
	change is made to the OID in question, and it would restrict vendor's		change is made to the OID in question, and it would restrict vendor's
	choice of OID management. etc.).		choice of OID management. etc.).
	Therefore, it is not favorable to use a vendor defined EKU for		Therefore, it is not favorable to use a vendor defined EKU for
	signing a document that is not governed by the vendor.		signing a document that is not governed by the vendor.
	This document defines a general Document Signing extended key usage.		This document defines a general Document Signing extended key purpose
			identifier.
	2. Conventions and Definitions		2. Conventions and Definitions
	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		"OPTIONAL" in this document are to be interpreted as described in
	BCP 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.
	3. Extended Key usage for DocumentSigning		3. Extended Key usage for DocumentSigning
	skipping to change at page 4, line 16 ¶		skipping to change at page 4, line 16 ¶
	[RFC5280] specifies the EKU X.509 certificate extension for use in		[RFC5280] specifies the EKU X.509 certificate extension for use in
	the Internet. The extension indicates one or more purposes for which		the Internet. The extension indicates one or more purposes for which
	the certified public key is valid. The EKU extension can be used in		the certified public key is valid. The EKU extension can be used in
	conjunction with the key usage extension, which indicates how the		conjunction with the key usage extension, which indicates how the
	public key in the certificate is used, in a more basic cryptographic		public key in the certificate is used, in a more basic cryptographic
	way.		way.
	The EKU extension syntax is repeated here for convenience:		The EKU extension syntax is repeated here for convenience:
	ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId		ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
	KeyPurposeId ::= OBJECT IDENTIFIER
			KeyPurposeId ::= OBJECT IDENTIFIER
	This specification defines the KeyPurposeId id-kp-documentSigning.		This specification defines the KeyPurposeId id-kp-documentSigning.
	Inclusion of this KeyPurposeId in a certificate indicates that the		Inclusion of this KeyPurposeId in a certificate indicates that the
	use of any Subject names in the certificate is restricted to use by a		use of any Subject names in the certificate is restricted to use by a
	document signing service or a software (along with any usages allowed		document signing service or a software (along with any usages allowed
	by other EKU values).		by other EKU values).
	id-kp OBJECT IDENTIFIER ::=		id-kp OBJECT IDENTIFIER ::=
	{ iso(1) identified-organization(3) dod(6) internet(1)		{ iso(1) identified-organization(3) dod(6) internet(1)
	security(5) mechanisms(5) pkix(7) 3 }		security(5) mechanisms(5) pkix(7) 3 }
	id-kp-documentSigning OBJECT IDENTIFIER ::= { id-kp XX }
			id-kp-documentSigning OBJECT IDENTIFIER ::= { id-kp XX }
	4. Using the Document Signing EKU in a Certificate		4. Using the Document Signing EKU in a Certificate
	[RFC8358] specifies the conventions for digital signatures on		[RFC8358] specifies the conventions for digital signatures on
	Internet-Drafts. This is one of the intended use cases for the		Internet-Drafts. This is one of the intended use cases for the
	general document signing EKU described in this document. [RFC8358]		general document signing EKU described in this document. [RFC8358]
	uses CMS to digitally sign a wide array of files such as ASCII, PDF,		uses CMS to digitally sign a wide array of files such as ASCII, PDF,
	EPUB, HTML etc. Currently, there are no specification regarding EKU		EPUB, HTML etc. Currently, there are no specification regarding EKU
	for certificates signing those files except those which are defined		for certificates signing those files except those which are defined
	by the software vendor.		by the software vendor.
	The signed contents of Internet-Drafts are primarily intended to be		The signed contents of Internet-Drafts are primarily intended to be
	consumed by human. To be more precise, contents are intended to be		consumed by people. To be more precise, contents are intended to be
	shown to human in a printable or displayable form by means of		shown to a person in a printable or displayable form by means of
	services or software, rather than processed by machines. To validate		services or software, rather than processed by machines. To validate
	the digital signature which is signed to contents intended to be		the digital signature on the contents that is intended to be consumed
	consumed by human, implementations MAY perform the steps below as a		by people, implementations MAY perform the steps below as a
	certificate validation:		certificate validation.
	The implementation MAY examine the Extended Key Usage value(s):		The implementation MAY examine the Extended Key Usage value(s):
	1. If there are no restrictions set for the relying party and the		1. If there are no restrictions set for the relying party and the
	relying party software, the certificate is acceptable.		relying party software, the certificate is acceptable.
	2. If there are restrictions set for the replying party and relying		2. If there are restrictions set for the replying party and relying
	party software, proceed as following.		party software, proceed as following.
	Each Restriction on the EKUs can be "Excluded EKU" or "Permitted EKU"		Each Restriction on the EKUs can be "Excluded EKU" or "Permitted
	and handled.		EKU" and handled.
	The procedure is intended to permit or prohibit presence of a certain		The procedure is intended to permit or prohibit presence of a
	EKU or complete absence of EKUs. It is outside the scope of this		certain EKU or complete absence of EKUs. It is outside the scope
	document, but the relying party can permit or prohibit conbinations		of this document, but the relying party can permit or exclude
	of EKU. A consideration on prohibiting combination of EKUs is		combinations of EKU. A consideration on prohibiting combination
	described in the security consideration section of this document.		of EKUs is described in the security consideration section of
			this document.
	2.1. Excluded EKUs procedure "Excluded EKU" is an EKU which the		Excluded EKUs procedure: "Excluded EKU" is an EKU which the
	relying party or the relying party software prohibits. Examples of		relying party or the relying party software prohibits.
	"Excluded EKU" are, presence of anyEKU or complete absence of EKU		Examples of "Excluded EKU" are, presence of
	extension on a certificate. If an EKU of the certificate meets the		anyExtendedKeyUsage or complete absence of EKU extension on a
	conditions set by the "Excluded EKU" restriction, the relying party		certificate. If an EKU of the certificate meets the
	or the relying party software rejects the certificate.		conditions set by the "Excluded EKU" restriction, the relying
			party or the relying party software rejects the certificate.
	2.2. Permitted EKU procedure "Permitted EKU" is an EKU which the		Permitted EKU procedure: "Permitted EKU" is an EKU which the
	relying party or the relying party software accepts. Examples of		relying party or the relying party software accepts. Examples
	"Permitted EKU" are, presence of this general document signing EKU		of "Permitted EKU" are, presence of this general document
	and/or protocol specific document signing-type EKUs. If an EKU of		signing EKU and/or protocol specific document signing-type
	the certificate meets the condition set by a "Permitted EKU"		EKUs. If an EKU of the certificate meets the condition set by
	restriction, the certificate is acceptable. Otherwise, relying party		a "Permitted EKU" restriction, the certificate is acceptable.
	or the relying party software rejects the certificate.		Otherwise, relying party or the relying party software rejects
			the certificate.
	When a single software has capability to process various data		When a single software has capability to process various data
	formats, the software may choose to make the excluded and permitted		formats, the software may choose to make the excluded and permitted
	decisions separately in accordance with the format it is handling		decisions separately in accordance with the format it is handling
	(e.g. text, pdf, etc).		(e.g. text, pdf, etc).
	5. Implications for a Certification Authority		5. Implications for a Certification Authority
	The procedures and practices employed by a certification authority		The procedures and practices employed by a certification authority
	MUST ensure that the correct values for the EKU extension are		MUST ensure that the correct values for the EKU extension are
	skipping to change at page 6, line 8 ¶		skipping to change at page 6, line 9 ¶
	governed by a vendor specific PKI (or trust program), certificates		governed by a vendor specific PKI (or trust program), certificates
	that indicate usage for document signing MAY include the id-kp-		that indicate usage for document signing MAY include the id-kp-
	documentSigning EKU extension. This does not encompass the mandatory		documentSigning EKU extension. This does not encompass the mandatory
	usage of the id-kp-documentSigning EKU in conjunction with the vendor		usage of the id-kp-documentSigning EKU in conjunction with the vendor
	specific EKU. However, this does not restrict the CA from including		specific EKU. However, this does not restrict the CA from including
	multiple EKUs related to document signing.		multiple EKUs related to document signing.
	6. Security Considerations		6. Security Considerations
	The usage of id-kp-documentSigning EKU intends to prevent id-kp-		The usage of id-kp-documentSigning EKU intends to prevent id-kp-
	emailProtection from being used for none-email purposes and id-kp-		emailProtection from being used for purposes other than email and id-
	codeSigning used to sign objects other than binary codes. This EKU		kp-codeSigning used to sign objects other than binary codes. This
	does not introduce new security risks but instead reduces existing		EKU does not introduce new security risks but instead reduces
	security risks by providing means to separate other EKUs used for		existing security risks by providing means to separate other EKUs
	communication protocols namely, TLS or S/MIME etc. in order to		used for communication protocols namely, TLS or S/MIME etc. in order
	minimize the risk of cross protocol attacks.		to minimize the risk of cross protocol attacks.
	To reduce the risk of specific cross protocol attacks, the relying		To reduce the risk of specific cross protocol attacks, the relying
	party or relying party software may additionaly prohibit use of		party or relying party software may additionaly prohibit use of
	specific combination of EKUs.		specific combination of EKUs.
	While a specific protocol or signing scheme may choose to come up		While a specific protocol or signing scheme may choose to come up
	with their own EKU, some may not have significant motive or resource		with their own EKU, some may not have significant motive or resource
	to set up and manage thier own EKU. This general document signing		to set up and manage thier own EKU. This general document signing
	EKU may be used as a stop gap for those that intend to set up their		EKU may be used as a stop gap for those that intend to set up their
	own EKU or those who do not intend to set up an EKU but still would		own EKU or those who do not intend to set up an EKU but still would
	skipping to change at page 6, line 39 ¶		skipping to change at page 6, line 40 ¶
	7. IANA Considerations		7. IANA Considerations
	This document requests that IANA make two assignments. One for the		This document requests that IANA make two assignments. One for the
	id-kp-documentSigning object identifier (OID), as defined in		id-kp-documentSigning object identifier (OID), as defined in
	Section 3.1, for the EKU from the "SMI Security for PKIX Extended Key		Section 3.1, for the EKU from the "SMI Security for PKIX Extended Key
	Purpose" (1.3.6.1.5.5.7.3) registry. Another for the id-mod-docsign-		Purpose" (1.3.6.1.5.5.7.3) registry. Another for the id-mod-docsign-
	eku, as defined in Appendix A, for the ASN.1 module [X.680] from the		eku, as defined in Appendix A, for the ASN.1 module [X.680] from the
	in the "SMI Security for PKIX Module Identifier" (1.3.6.1.5.5.7.0)		in the "SMI Security for PKIX Module Identifier" (1.3.6.1.5.5.7.0)
	registry. No further action is necessary by IANA.		registry. No further action is necessary by IANA.
	8. Normative References		8. References
			8.1. 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,
	<https://www.rfc-editor.org/rfc/rfc2119>.		<https://www.rfc-editor.org/rfc/rfc2119>.
	[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/rfc/rfc5280>.		<https://www.rfc-editor.org/rfc/rfc5280>.
	[RFC7299] Housley, R., "Object Identifier Registry for the PKIX
	Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014,
	<https://www.rfc-editor.org/rfc/rfc7299>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.		May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
	[RFC8358] Housley, R., "Update to Digital Signatures on Internet-
	Draft Documents", RFC 8358, DOI 10.17487/RFC8358, March
	2018, <https://www.rfc-editor.org/rfc/rfc8358>.
	[X.680] ITU-T, "Information technology - Abstract Syntax Notation		[X.680] ITU-T, "Information technology - Abstract Syntax Notation
	One (ASN.1): Specification of basic notation", ISO/		One (ASN.1): Specification of basic notation", ISO/
	IEC 8824-1:2015, November 2015.		IEC 8824-1:2015, November 2015.
			8.2. Informative References
			[RFC7299] Housley, R., "Object Identifier Registry for the PKIX
			Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014,
			<https://www.rfc-editor.org/rfc/rfc7299>.
			[RFC8358] Housley, R., "Update to Digital Signatures on Internet-
			Draft Documents", RFC 8358, DOI 10.17487/RFC8358, March
			2018, <https://www.rfc-editor.org/rfc/rfc8358>.
	Appendix A. ASN.1 Module		Appendix A. ASN.1 Module
	The following ASN.1 module provides the complete definition of the		The following ASN.1 module provides the complete definition of the
	Document Signing EKU.		Document Signing EKU.
	DocSignEKU { iso(1) identified-organization(3) dod(6) internet(1)		DocSignEKU { iso(1) identified-organization(3) dod(6) internet(1)
	security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-docsign-eku(TBD1) }		security(5) mechanisms(5) pkix(7) id-mod(0)
			id-mod-docsign-eku(TBD1) }
	DEFINITIONS EXPLICIT TAGS ::=		DEFINITIONS EXPLICIT TAGS ::=
	BEGIN		BEGIN
	-- EXPORTS ALL --		-- EXPORTS ALL --
	-- IMPORTS NOTHING --		-- IMPORTS NOTHING --
	-- OID Arc --		-- OID Arc --
	id-kp OBJECT IDENTIFIER ::= {		id-kp OBJECT IDENTIFIER ::= {
	iso(1) identified-organization(3) dod(6) internet(1)		iso(1) identified-organization(3) dod(6) internet(1)
	security(5) mechanisms(5) pkix(7) kp(3) }		security(5) mechanisms(5) pkix(7) kp(3) }
	-- Document Signing Extended Key Usage --		-- Document Signing Extended Key Usage --
	id-kp-documentSigning OBJECT IDENTIFIER ::= { id-kp TBD2 }		id-kp-documentSigning OBJECT IDENTIFIER ::= { id-kp TBD2 }
	END		END
	Acknowledgments		Acknowledgments
	We would like to thank Russ Housley for verifying the ASN.1 module.		We would like to thank Russ Housley for verifying the ASN.1 module.
	Authors' Addresses		Authors' Addresses
	Tadahiko Ito		Tadahiko Ito
	SECOM CO., LTD.		SECOM CO., LTD.
	Email: tadahiko.ito.public@gmail.com		Email: tadahiko.ito.public@gmail.com
	Tomofumi Okubo		Tomofumi Okubo
	DigiCert, Inc.		DigiCert, Inc.
	Email: tomofumi.okubo+ietf@gmail.com		Email: tomofumi.okubo+ietf@gmail.com
	Sean Turner		Sean Turner
	sn3rd		sn3rd
	Email: sean@sn3rd.com		Email: sean@sn3rd.com
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