< draft-ietf-lamps-cms-update-alg-id-protect-02.txt		draft-ietf-lamps-cms-update-alg-id-protect-03.txt >
	Network Working Group R. Housley		Network Working Group R. Housley
	Internet-Draft Vigil Security		Internet-Draft Vigil Security
	Updates: 5652 (if approved) May 28, 2020		Updates: 5652 (if approved) August 07, 2020
	Intended status: Standards Track		Intended status: Standards Track
	Expires: November 29, 2020		Expires: February 8, 2021
	Update to the Cryptographic Message Syntax (CMS) for Algorithm		Update to the Cryptographic Message Syntax (CMS) for Algorithm
	Identifier Protection		Identifier Protection
	draft-ietf-lamps-cms-update-alg-id-protect-02		draft-ietf-lamps-cms-update-alg-id-protect-03
	Abstract		Abstract
	This document updates the Cryptographic Message Syntax (CMS)		This document updates the Cryptographic Message Syntax (CMS)
	specified in RFC 5652 to ensure that algorithm identifiers in signed-		specified in RFC 5652 to ensure that algorithm identifiers in signed-
	data and authenticated-data content types are adequately protected.		data and authenticated-data content types are adequately protected.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	skipping to change at page 1, line 34 ¶		skipping to change at page 1, line 34 ¶
	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 29, 2020.		This Internet-Draft will expire on February 8, 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
	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 . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Require use the same hash algorithm . . . . . . . . . . . . . 3		3. Required use the same hash algorithm . . . . . . . . . . . . 3
	3.1. RFC 5652, Section 5.3 . . . . . . . . . . . . . . . . . . 3		3.1. RFC 5652, Section 5.3 . . . . . . . . . . . . . . . . . . 3
	3.2. RFC 5652, Section 5.4 . . . . . . . . . . . . . . . . . . 4		3.2. RFC 5652, Section 5.4 . . . . . . . . . . . . . . . . . . 4
	3.3. RFC 5652, Section 5.6 . . . . . . . . . . . . . . . . . . 4		3.3. RFC 5652, Section 5.6 . . . . . . . . . . . . . . . . . . 4
	3.4. Backward Compatibility Considerations . . . . . . . . . . 5		3.4. Backward Compatibility Considerations . . . . . . . . . . 5
	3.5. Timestamp Compatibility Considerations . . . . . . . . . 5		3.5. Timestamp Compatibility Considerations . . . . . . . . . 5
	4. Recommend inclusion of the CMSAlgorithmProtection attribute . 5		4. Recommend inclusion of the CMSAlgorithmProtection attribute . 5
	4.1. RFC 5652, Section 14 . . . . . . . . . . . . . . . . . . 6		4.1. RFC 5652, Section 14 . . . . . . . . . . . . . . . . . . 6
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 6		6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	8.1. Normative References . . . . . . . . . . . . . . . . . . 6		8.1. Normative References . . . . . . . . . . . . . . . . . . 7
	8.2. Informative References . . . . . . . . . . . . . . . . . 7		8.2. Informative References . . . . . . . . . . . . . . . . . 7
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	This document updates the Cryptographic Message Syntax (CMS)		This document updates the Cryptographic Message Syntax (CMS)
	[RFC5652] to ensure that algorithm identifiers in signed-data and		[RFC5652] to ensure that algorithm identifiers in signed-data and
	authenticated-data content types are adequately protected.		authenticated-data content types are adequately protected.
	The CMS signed-data Content Type [RFC5652], unlike X.509 certificates		The CMS signed-data Content Type [RFC5652], unlike X.509 certificates
	skipping to change at page 3, line 34 ¶		skipping to change at page 3, line 34 ¶
	originator include the CMSAlgorithmProtection attribute [RFC6211].		originator include the CMSAlgorithmProtection attribute [RFC6211].
	2. Terminology		2. 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		"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. Require use the same hash algorithm		3. Required use the same hash algorithm
	This section updates [RFC5652] to require the originator to use the		This section updates [RFC5652] to require the originator to use the
	same hash algorithm to compute the digest of the message content and		same hash algorithm to compute the digest of the message content and
	the digest of signed attributes.		the digest of signed attributes.
	3.1. RFC 5652, Section 5.3		3.1. RFC 5652, Section 5.3
	Change the paragraph describing the digestAlgorithm as follows:		Change the paragraph describing the digestAlgorithm as follows:
	OLD:		OLD:
	skipping to change at page 4, line 14 ¶		skipping to change at page 4, line 14 ¶
	Implementations MAY fail to validate signatures that use a digest		Implementations MAY fail to validate signatures that use a digest
	algorithm that is not included in the SignedData digestAlgorithms		algorithm that is not included in the SignedData digestAlgorithms
	set.		set.
	NEW:		NEW:
	digestAlgorithm identifies the message digest algorithm, and any		digestAlgorithm identifies the message digest algorithm, and any
	associated parameters, used by the signer. The message digest is		associated parameters, used by the signer. The message digest is
	computed on either the content being signed or the content		computed on either the content being signed or the content
	together with the signed attributes using the process described in		together with the signedAttrs using the process described in
	Section 5.4. The message digest algorithm SHOULD be among those		Section 5.4. The message digest algorithm SHOULD be among those
	listed in the digestAlgorithms field of the associated SignerData.		listed in the digestAlgorithms field of the associated SignerData.
	If signedAttrs are present in the SignerInfo, then the same digest		If signedAttrs field is present in the SignerInfo, then the same
	algorithm MUST be used to compute the digest of the SignedData		digest algorithm MUST be used to compute both the digest of the
	encapContentInfo eContent, which is carried in the message-digest		SignedData encapContentInfo eContent, which is carried in the
	attribute, and to compute the digest of the DER-encoded SET OF		message-digest attribute, and the digest of the DER-encoded
	signed attributes, which is passed to the signature algorithm.		signedAttrs, which is passed to the signature algorithm.
	Implementations MAY fail to validate signatures that use a digest		Implementations MAY fail to validate signatures that use a digest
	algorithm that is not included in the SignedData digestAlgorithms		algorithm that is not included in the SignedData digestAlgorithms
	set.		set.
	3.2. RFC 5652, Section 5.4		3.2. RFC 5652, Section 5.4
	Add the following paragraph as the second paragraph in Section 5.4:		Add the following paragraph as the second paragraph in Section 5.4:
	ADD:		ADD:
	When the signedAttrs field is present, the same digest algorithm		When the signedAttrs field is present, the same digest algorithm
	MUST be used to compute the digest of the the encapContentInfo		MUST be used to compute the digest of the encapContentInfo
	eContent OCTET STRING, which is carried in the message-digest		eContent OCTET STRING, which is carried in the message-digest
	attribute, and the collection of attributes that are signed.		attribute, and the collection of attributes that are signed.
	3.3. RFC 5652, Section 5.6		3.3. RFC 5652, Section 5.6
	Change the paragraph discussing the signedAttributes as follows:		Change the paragraph discussing the signed attributes as follows:
	OLD:		OLD:
	The recipient MUST NOT rely on any message digest values computed		The recipient MUST NOT rely on any message digest values computed
	by the originator. If the SignedData signerInfo includes		by the originator. If the SignedData signerInfo includes
	signedAttributes, then the content message digest MUST be		signedAttributes, then the content message digest MUST be
	calculated as described in Section 5.4. For the signature to be		calculated as described in Section 5.4. For the signature to be
	valid, the message digest value calculated by the recipient MUST		valid, the message digest value calculated by the recipient MUST
	be the same as the value of the messageDigest attribute included		be the same as the value of the messageDigest attribute included
	in the signedAttributes of the SignedData signerInfo.		in the signedAttributes of the SignedData signerInfo.
	NEW:		NEW:
	The recipient MUST NOT rely on any message digest values computed		The recipient MUST NOT rely on any message digest values computed
	by the originator. If the SignedData signerInfo includes		by the originator. If the SignedData signerInfo includes the
	signedAttributes, then the content message digest MUST be		signedAttrs field, then the content message digest MUST be
	calculated as described in Section 5.4, using the same digest		calculated as described in Section 5.4, using the same digest
	algorithm to compute the digest of the the encapContentInfo		algorithm to compute the digest of the encapContentInfo eContent
	eContent OCTET STRING and the message-digest attribute. For the		OCTET STRING and the message-digest attribute. For the signature
	signature to be valid, the message digest value calculated by the		to be valid, the message digest value calculated by the recipient
	recipient MUST be the same as the value of the messageDigest		MUST be the same as the value of the messageDigest attribute
	attribute included in the signedAttributes of the SignedData		included in the signedAttrs field of the SignedData signerInfo.
	signerInfo.
	3.4. Backward Compatibility Considerations		3.4. Backward Compatibility Considerations
	The new requirement introduced above might lead to compatibility with		The new requirement introduced above might lead to incompatibility
	an implementation that allowed different digest algorithms to be used		with an implementation that allowed different digest algorithms to be
	to compute the digest of the message content and the digest of signed		used to compute the digest of the message content and the digest of
	attributes. The signatures produced by such an implementation when		signed attributes. The signatures produced by such an implementation
	two different digest algorithms are used will be considered invalid		when two different digest algorithms are used will be considered
	by an implementation that follows this specification. However, most,		invalid by an implementation that follows this specification.
	if not all, implementations already require the originator to use the		However, most, if not all, implementations already require the
	same digest algorithm for both operations.		originator to use the same digest algorithm for both operations.
	3.5. Timestamp Compatibility Considerations		3.5. Timestamp Compatibility Considerations
	The new requirement introduced above might lead to compatibility		The new requirement introduced above might lead to compatibility
	issues for timestamping systems when the originator does not wish to		issues for timestamping systems when the originator does not wish to
	share the message content with the Time Stamp Authority (TSA)		share the message content with the Time Stamp Authority (TSA)
	[RFC3161]. In this situation, the originator sends a TimeStampReq to		[RFC3161]. In this situation, the originator sends a TimeStampReq to
	the TSA that includes a MessageImprint, which consists of a digest		the TSA that includes a MessageImprint, which consists of a digest
	algorithm identifier and a digest value, then the TSA uses the		algorithm identifier and a digest value, then the TSA uses the
	originator-provided digest in the MessageImprint.		originator-provided digest in the MessageImprint.
	skipping to change at page 6, line 28 ¶		skipping to change at page 6, line 28 ¶
	originator of an authenticated-data content type that includes		originator of an authenticated-data content type that includes
	authenticated attributes SHOULD include the CMSAlgorithmProtection		authenticated attributes SHOULD include the CMSAlgorithmProtection
	attribute [RFC6211] as one of the authenticated attributes.		attribute [RFC6211] as one of the authenticated attributes.
	5. IANA Considerations		5. IANA Considerations
	This document makes no requests of the IANA.		This document makes no requests of the IANA.
	6. Security Considerations		6. Security Considerations
	The security considerations of [RFC5652] are updated ensure that		The security properties of the CMS [RFC5652] signed-data and
	algorithm identifiers are adequately protected, which makes algorithm		authenticated-data content types are updated to ensure that algorithm
			identifiers are adequately protected, which makes algorithm
	substitution attacks significantly more difficult.		substitution attacks significantly more difficult.
			For the signed-data content type, the improvements specified in this
			document force an attacker to mount a hash algorithm substitution
			attack on the overall signature, not just on the message digest of
			the encapContentInfo eContent.
			Some digital signature algorithms have prevented hash function
			substitutions by including a digest algorithm identifier as an input
			to the signature algorithm. As discussed in [HASHID], such a
			"firewall" may not be effective or even possible with newer signature
			algorithms. For example, RSASSA-PKCS1-v1_5 [RFC8017] protects the
			digest algorithm identifier, but RSASSA-PSS [RFC8017] does not.
			Therefore, it remains important that a signer have a way to signal to
			a recipient which digest algorithms are allowed to be used in
			conjunction with the verification of an overall signature. This
			signalling can be done as part of the specification of the signature
			algorithm in an X.509v3 certificate extension [RFC5280], or some
			other means. The Digital Signature Standard (DSS) [DSS] takes the
			first approach by requiring the use of an "approved" one-way hash
			algorithm.
			For the authenticated-data content type, the improvements specified
			in this document force an attacker to mount a MAC algorithm
			substitution attack, which is difficult because the attacker does not
			know the authentication key.
	The CMSAlgorithmProtection attribute [RFC6211] offers protection for		The CMSAlgorithmProtection attribute [RFC6211] offers protection for
	the algorithm identifiers used in the signed-data and authenticated-		the algorithm identifiers used in the signed-data and authenticated-
	data content types. There is not currently protection mechanism for		data content types. However, no protection is provided for the
	the algorithm identifiers used in the enveloped-data, digested-data,		algorithm identifiers in the enveloped-data, digested-data, or
	or encrypted-data content types. Likewise there is not currently a		encrypted-data content types. Likewise, The CMSAlgorithmProtection
	protection mechanism for the algorithm identifiers used in the		attribute provides no protection for the algorithm identifiers used
	authenticated-enveloped-data content type defined in [RFC5083].		in the authenticated-enveloped-data content type defined in
			[RFC5083].
	7. Acknowledgements		7. Acknowledgements
	Many thanks to Jim Schaad and Peter Gutmann; without knowing it, they		Many thanks to Jim Schaad and Peter Gutmann; without knowing it, they
	motivated me to write this document.		motivated me to write this document. Thanks to Roman Danyliw for
			careful review and editorial suggestions.
	8. References		8. References
	8.1. Normative 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/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	skipping to change at page 7, line 22 ¶		skipping to change at page 7, line 51 ¶
	<https://www.rfc-editor.org/info/rfc6211>.		<https://www.rfc-editor.org/info/rfc6211>.
	[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/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	8.2. Informative References		8.2. Informative References
	[DSS] National Institute of Standards and Technology (NIST),		[DSS] National Institute of Standards and Technology (NIST),
	"Digital Signature Standard (DSS)", FIPS		"Digital Signature Standard (DSS)", FIPS
	Publication 186-3, June 2009.		Publication 186-4, July 2013.
			[HASHID] Kaliski, B., "On Hash Function Firewalls in Signature
			Schemes", Lecture Notes in Computer Science, Volume 2271,
			DOI 10.1007/3-540-45760-7_1, February 2002.
	[RFC3161] Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,		[RFC3161] Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,
	"Internet X.509 Public Key Infrastructure Time-Stamp		"Internet X.509 Public Key Infrastructure Time-Stamp
	Protocol (TSP)", RFC 3161, DOI 10.17487/RFC3161, August		Protocol (TSP)", RFC 3161, DOI 10.17487/RFC3161, August
	2001, <https://www.rfc-editor.org/info/rfc3161>.		2001, <https://www.rfc-editor.org/info/rfc3161>.
	[RFC5083] Housley, R., "Cryptographic Message Syntax (CMS)		[RFC5083] Housley, R., "Cryptographic Message Syntax (CMS)
	Authenticated-Enveloped-Data Content Type", RFC 5083,		Authenticated-Enveloped-Data Content Type", RFC 5083,
	DOI 10.17487/RFC5083, November 2007,		DOI 10.17487/RFC5083, November 2007,
	<https://www.rfc-editor.org/info/rfc5083>.		<https://www.rfc-editor.org/info/rfc5083>.
	skipping to change at page 7, line 45 ¶		skipping to change at page 8, line 30 ¶
	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>.
	[RFC6210] Schaad, J., "Experiment: Hash Functions with Parameters in		[RFC6210] Schaad, J., "Experiment: Hash Functions with Parameters in
	the Cryptographic Message Syntax (CMS) and S/MIME",		the Cryptographic Message Syntax (CMS) and S/MIME",
	RFC 6210, DOI 10.17487/RFC6210, April 2011,		RFC 6210, DOI 10.17487/RFC6210, April 2011,
	<https://www.rfc-editor.org/info/rfc6210>.		<https://www.rfc-editor.org/info/rfc6210>.
			[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
			"PKCS #1: RSA Cryptography Specifications Version 2.2",
			RFC 8017, DOI 10.17487/RFC8017, November 2016,
			<https://www.rfc-editor.org/info/rfc8017>.
	[SHS] National Institute of Standards and Technology (NIST),		[SHS] National Institute of Standards and Technology (NIST),
	"Secure Hash Standard", FIPS Publication 180-3, October		"Secure Hash Standard", FIPS Publication 180-4, August
	2008.		2015.
	Author's Address		Author's Address
	Russ Housley		Russ Housley
	Vigil Security, LLC		Vigil Security, LLC
	516 Dranesville Road		516 Dranesville Road
	Herndon, VA 20170		Herndon, VA 20170
	US		US
	Email: housley@vigilsec.com		Email: housley@vigilsec.com
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