< draft-ietf-dnsext-dnssec-algo-signal-09.txt		draft-ietf-dnsext-dnssec-algo-signal-10.txt >
	DNS Extensions Working Group S. Crocker		DNS Extensions Working Group S. Crocker
	Internet-Draft Shinkuro Inc.		Internet-Draft Shinkuro Inc.
	Intended status: Standards Track S. Rose		Intended status: Standards Track S. Rose
	Expires: March 28, 2013 NIST		Expires: October 10, 2013 NIST
	September 24, 2012		April 08, 2013
	Signaling Cryptographic Algorithm Understanding in DNSSEC		Signaling Cryptographic Algorithm Understanding in DNSSEC
	draft-ietf-dnsext-dnssec-algo-signal-09		draft-ietf-dnsext-dnssec-algo-signal-10
	Abstract		Abstract
	The DNS Security Extensions (DNSSEC) were developed to provide origin		The DNS Security Extensions (DNSSEC) were developed to provide origin
	authentication and integrity protection for DNS data by using digital		authentication and integrity protection for DNS data by using digital
	signatures. These digital signatures can be generated using		signatures. These digital signatures can be generated using
	different algorithms. This draft sets out to specify a way for		different algorithms. This draft sets out to specify a way for
	validating end-system resolvers to signal to a server which digital		validating end-system resolvers to signal to a server which digital
	signature and hash algorithms they support.		signature and hash algorithms they support. The proposed extensions
			allow the signaling of new algorithm uptake in client code to allow
			zone administrators to know when it is possible to complete an
			algorithm rollover in a DNSSEC signed zone.
	Requirements Language		Requirements Language
	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 RFC		"OPTIONAL" in this document are to be interpreted as described in RFC
	2119 [RFC2119].		2119 [RFC2119].
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 43 ¶		skipping to change at page 1, line 46 ¶
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 March 28, 2013.		This Internet-Draft will expire on October 10, 2013.
	Copyright Notice		Copyright Notice
			Copyright (c) 2013 IETF Trust and the persons identified as the
	Copyright (c) 2012 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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 . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash		2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash
	Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . . 3		Understood (DHU) and NSEC3 Hash Understood (N3U) Using EDNS . 3
			3. Client Considerations . . . . . . . . . . . . . . . . . . . . 4
	3. Client Considerations . . . . . . . . . . . . . . . . . . . . . 5		3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . 5
	3.1. Stub Resolvers . . . . . . . . . . . . . . . . . . . . . . 5		3.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . 5
	3.1.1. Validating Stub Resolvers . . . . . . . . . . . . . . . 5		3.1.2. Non-Validating Stub Resolvers . . . . . . . . . . . . 5
	3.1.2. Non-Validating Stub Resolvers . . . . . . . . . . . . . 5		3.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . 5
	3.2. Recursive Resolvers . . . . . . . . . . . . . . . . . . . . 5		3.2.1. Validating Recursive Resolvers . . . . . . . . . . . 5
	3.2.1. Validating Recursive Resolvers . . . . . . . . . . . . 5		3.2.2. Non-validating Recursive Resolvers . . . . . . . . . 6
	3.2.2. Non-validating Recursive Resolvers . . . . . . . . . . 6		4. Intermediate System Considerations . . . . . . . . . . . . . 6
			5. Server Considerations . . . . . . . . . . . . . . . . . . . . 6
	4. Intermediate System Considerations . . . . . . . . . . . . . . 6		6. Traffic Analysis Considerations . . . . . . . . . . . . . . . 6
			7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
	5. Server Considerations . . . . . . . . . . . . . . . . . . . . . 6		8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
			9. Normative References . . . . . . . . . . . . . . . . . . . . 8
	6. Traffic Analysis Considerations . . . . . . . . . . . . . . . . 6		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
	8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
	9. Normative References . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	The DNS Security Extensions (DNSSEC) [RFC4033], [RFC4034] and		The DNS Security Extensions (DNSSEC) [RFC4033], [RFC4034] and
	[RFC4035] were developed to provide origin authentication and		[RFC4035] were developed to provide origin authentication and
	integrity protection for DNS data by using digital signatures. Each		integrity protection for DNS data by using digital signatures. Each
	digital signature RR (RRSIG) contains an algorithm code number.		digital signature RR (RRSIG) contains an algorithm code number.
	These algorithm codes tell validators which cryptographic algorithm		These algorithm codes tell validators which cryptographic algorithm
	was used to generate the digital signature.		was used to generate the digital signature.
	Likewise, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value		Likewise, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value
	as part of their RDATA and, like digital signature algorithms, these		as part of their RDATA and, like digital signature algorithms, these
	hash algorithms have code numbers. All three algorithm codes (RRSIG/		hash algorithms have code numbers. All three algorithm codes (RRSIG/
	DNSKEY, DS and NSEC3) are maintained in unique IANA registries.		DNSKEY, DS and NSEC3) are maintained in unique IANA registries.
	This draft sets out to specify a way for validating end-system		This draft sets out to specify a way for validating end-system
	resolvers to tell a server in a DNS query which digital signature		resolvers to tell a server in a DNS query which digital signature and
	and/or hash algorithms they support. This is done using the new EDNS		/or hash algorithms they support. This is done using the new EDNS
	options specified below in Section 2 for use in the OPT meta-RR		options specified below in Section 2 for use in the OPT meta-RR
	[I-D.ietf-dnsext-rfc2671bis-edns0]. These three new EDNS option		[I-D.ietf-dnsext-rfc2671bis-edns0]. These three new EDNS option
	codes are all OPTIONAL to implement and use.		codes are all OPTIONAL to implement and use.
	These proposed EDNS options serve to measure the acceptance and use		These proposed EDNS options serve to measure the acceptance and use
	of new digital signing algorithms. These signaling options can be		of new digital signing algorithms. These signaling options can be
	used by zone administrators as a gauge to measure the successful		used by zone administrators as a gauge to measure the successful
	deployment of code that implements newly deployed digital signature		deployment of code that implements newly deployed digital signature
	algorithm, DS hash and NSEC3 hash algorithm used with DNSSEC. A zone		algorithm, DS hash and NSEC3 hash algorithm used with DNSSEC. A zone
	administrator is able to determine when to stop signing with a		administrator is able to determine when to stop signing with a
	skipping to change at page 4, line 46 ¶		skipping to change at page 4, line 40 ¶
	algorithms, DS hash algorithms, or NSEC3 hash algorithms (depending		algorithms, DS hash algorithms, or NSEC3 hash algorithms (depending
	on the OPTION-CODE in use) that the client declares to be supported.		on the OPTION-CODE in use) that the client declares to be supported.
	The order of the code values can be arbitrary and MUST NOT be used to		The order of the code values can be arbitrary and MUST NOT be used to
	infer preference.		infer preference.
	If all three options are included in the OPT RR, there is a potential		If all three options are included in the OPT RR, there is a potential
	for the OPT RR to take up considerable size in the DNS message.		for the OPT RR to take up considerable size in the DNS message.
	However, in practical terms, including all three options is likely to		However, in practical terms, including all three options is likely to
	take up 22-32 octets (average of 6-10 digital signature algorithms,		take up 22-32 octets (average of 6-10 digital signature algorithms,
	3-5 DS hash algorithms and 1-5 NSEC3 hash algorithms) including the		3-5 DS hash algorithms and 1-5 NSEC3 hash algorithms) including the
	EDNS option codes and option lengths in a potential future example.		EDNS option codes and option lengths in potential future examples.
	3. Client Considerations		3. Client Considerations
	A validating end-system resolver sets the DAU, DHU and/or N3U option,		A validating end-system resolver sets the DAU, DHU and/or N3U option,
	or combination thereof in the OPT meta-RR when sending a query. The		or combination thereof in the OPT meta-RR when sending a query. The
	validating end-system resolver MUST also set the DNSSEC-OK bit		validating end-system resolver MUST also set the DNSSEC-OK bit
	[RFC4035] to indicate that it wishes to receive DNSSEC RRs in the		[RFC4035] to indicate that it wishes to receive DNSSEC RRs in the
	response.		response.
	Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) digital		Note that the PRIVATEDNS (253) and/or the PRIVATEOID (254) digital
	signature codes both cover a potentially wide range of algorithms and		signature codes both cover a potentially wide range of algorithms and
	are likely not useful to a server. There is no compelling reason for		are likely not useful to a server. There is no compelling reason for
	a client to include these codes in its list of the DAU. Likewise,		a client to include these codes in its list of the DAU. Likewise,
	clients MUST NOT include RESERVED codes in any of the options.		clients MUST NOT include RESERVED codes in any of the options.
			Likewise, a client is under no obligation to list every algorithm it
			implements and MAY choose to only list algorithms the client wishes
			to signal as understood.
			Since the DAU, DHU and/or N3U options are only set in the query, if a
			client sees these options in the response, no action needs to be
			taken and the client MUST ignore the option values.
	3.1. Stub Resolvers		3.1. Stub Resolvers
	Typically, stub resolvers rely on an upstream recursive server (or		Typically, stub resolvers rely on an upstream recursive server (or
	cache) to provide a response. So optimal setting of the DAU, DSU and		cache) to provide a response. So optimal setting of the DAU, DSU and
	N3U options depends on whether the stub resolver elects to perform		N3U options depends on whether the stub resolver elects to perform
	its own validation.		its own validation.
	3.1.1. Validating Stub Resolvers		3.1.1. Validating Stub Resolvers
	skipping to change at page 5, line 47 ¶		skipping to change at page 5, line 46 ¶
	validating stub resolvers.		validating stub resolvers.
	3.2. Recursive Resolvers		3.2. Recursive Resolvers
	3.2.1. Validating Recursive Resolvers		3.2.1. Validating Recursive Resolvers
	A validating recursive resolver sets the DAU, DHU and/or N3U		A validating recursive resolver sets the DAU, DHU and/or N3U
	option(s) when performing recursion based on its list of algorithms		option(s) when performing recursion based on its list of algorithms
	and any DAU, DHU and/or N3U option lists in the stub client query.		and any DAU, DHU and/or N3U option lists in the stub client query.
	When the recursive server receives a query with one or more of the		When the recursive server receives a query with one or more of the
	options set, the recursive server MUST set the algorithm list to a		options set, the recursive server MUST set the algorithm list for any
	union of the stub client's list and the validating recursive		outgoing iterative queries for that resolution chain to a union of
	resolver's list. For example, if the recursive resolver's algorithm		the stub client's list and the validating recursive resolver's list.
	list for the DAU option is (3, 5, 7) and the stub's algorithm list is		For example, if the recursive resolver's algorithm list for the DAU
	(7, 8), the final DAU algorithm list would be (3, 5, 7, 8).		option is (3, 5, 7) and the stub's algorithm list is (7, 8), the
			final DAU algorithm list would be (3, 5, 7, 8).
	If the client did include the DO and CD bits, but did not include the		If the client did include the DO and CD bits, but did not include the
	DAU, DHU and/or N3U option(s) in the query, the validating recursive		DAU, DHU and/or N3U option(s) in the query, the validating recursive
	resolver MAY include the option(s) with its own list in full. If one		resolver MAY include the option(s) with its own list in full. If one
	or more of the options are missing, the validating recursive resolver		or more of the options are missing, the validating recursive resolver
	MAY include the missing options with its own list in full.		MAY include the missing options with its own list in full.
			Validating recursive resolvers MUST NOT set the DAU, DHU and/or N3U
			option(s) in the final response to the stub client.
	3.2.2. Non-validating Recursive Resolvers		3.2.2. Non-validating Recursive Resolvers
	Recursive resolvers that do not do validation MUST copy the DAU, DHU		Recursive resolvers that do not do validation MUST copy the DAU, DHU
	and/or N3U option(s) seen in received queries as they represent the		and/or N3U option(s) seen in received queries as they represent the
	wishes of the validating downstream resolver that issued the original		wishes of the validating downstream resolver that issued the original
	query.		query.
	4. Intermediate System Considerations		4. Intermediate System Considerations
	Intermediate proxies [RFC5625] that understand DNS are RECOMMENDED to		Intermediate proxies [RFC5625] (Section 4.4.2) that understand DNS
	behave like a comparable recursive resolver when dealing with the		are RECOMMENDED to behave like a comparable recursive resolver when
	DAU, DHU and N3U options.		dealing with the DAU, DHU and N3U options.
	5. Server Considerations		5. Server Considerations
	When an authoritative server sees the DAU, DHU and/or N3U option(s)		When an authoritative server sees the DAU, DHU and/or N3U option(s)
	in the OPT meta-RR in a request the normal algorithm for servicing		in the OPT meta-RR in a request the normal algorithm for servicing
	requests is followed. The options MUST NOT trigger any special		requests is followed. The options MUST NOT trigger any special
	processing (e.g. RRSIG filtering in responses) on the server side.		processing (e.g. RRSIG filtering in responses) on the server side.
	If the options are present but the DNSSEC-OK (OK) bit is not set, the		If the options are present but the DNSSEC-OK (OK) bit is not set, the
	server does not do any DNSSEC processing, including any recording of		server does not do any DNSSEC processing, including any recording of
	the option(s).		the option(s).
	6. Traffic Analysis Considerations		If the server sees one (or more) of the options set with RESERVED
			values, the server MAY ignore recoding of those values.
			Authoritative servers MUST NOT set the DAU, DHU and/or N3U option(s)
			on any responses. These values are only set in queries.
			6. Traffic Analysis Considerations
	Zone administrators that are planning or are in the process of a		Zone administrators that are planning or are in the process of a
	cryptographic algorithm rollover operation should monitor DNS query		cryptographic algorithm rollover operation should monitor DNS query
	traffic and record the number of queries, the presence of the OPT RR		traffic and record the number of queries, the presence of the OPT RR
	in queries and the values of the DAU/DHU/N3U option(s) (if present).		in queries and the values of the DAU/DHU/N3U option(s) (if present).
	This monitoring can be used to measure the deployment of client code		This monitoring can be used to measure the deployment of client code
	that implements (and signals) specific algorithms. Description of		that implements (and signals) specific algorithms. Description of
	the techniques used to capture DNS traffic and measure new algorithm		the techniques used to capture DNS traffic and measure new algorithm
	adoption is beyond the scope of this document.		adoption is beyond the scope of this document.
	Zone administrators that need to comply with changes to their		Zone administrators that need to comply with changes to their
	skipping to change at page 7, line 42 ¶		skipping to change at page 8, line 10 ¶
	There is a possibility that an eavesdropper or server could infer the		There is a possibility that an eavesdropper or server could infer the
	validator in use by a client by the presence of the AU options and/or		validator in use by a client by the presence of the AU options and/or
	algorithm code list. This information leakage in itself is not very		algorithm code list. This information leakage in itself is not very
	useful to a potential attacker but it could be used to identify the		useful to a potential attacker but it could be used to identify the
	validator or narrow down the possible validator implementations in		validator or narrow down the possible validator implementations in
	use by a client, which could have a known vulnerability that could be		use by a client, which could have a known vulnerability that could be
	exploited by the attacker.		exploited by the attacker.
	9. Normative References		9. Normative References
	[I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P.		[I-D.ietf-dnsext-rfc2671bis-edns0]
	Vixie, "Extension Mechanisms for		Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
	DNS (EDNS0)", draft-ietf-dnsext-		for DNS (EDNS(0))", draft-ietf-dnsext-rfc2671bis-edns0-10
	rfc2671bis-edns0-09 (work in		(work in progress), December 2012.
	progress), August 2012.
	[RFC2119] Bradner, S., "Key words for use		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	in RFCs to Indicate Requirement		Requirement Levels", BCP 14, RFC 2119, March 1997.
	Levels", BCP 14, RFC 2119,
	March 1997.
	[RFC4033] Arends, R., Austein, R., Larson,		[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	M., Massey, D., and S. Rose, "DNS		Rose, "DNS Security Introduction and Requirements", RFC
	Security Introduction and		4033, March 2005.
	Requirements", RFC 4033,
	March 2005.
	[RFC4034] Arends, R., Austein, R., Larson,		[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	M., Massey, D., and S. Rose,		Rose, "Resource Records for the DNS Security Extensions",
	"Resource Records for the DNS		RFC 4034, March 2005.
	Security Extensions", RFC 4034,
	March 2005.
	[RFC4035] Arends, R., Austein, R., Larson,		[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
	M., Massey, D., and S. Rose,		Rose, "Protocol Modifications for the DNS Security
	"Protocol Modifications for the		Extensions", RFC 4035, March 2005.
	DNS Security Extensions",
	RFC 4035, March 2005.
	[RFC5625] Bellis, R., "DNS Proxy		[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines", BCP
	Implementation Guidelines",		152, RFC 5625, August 2009.
	BCP 152, RFC 5625, August 2009.
	Authors' Addresses		Authors' Addresses
	Steve Crocker		Steve Crocker
	Shinkuro Inc.		Shinkuro Inc.
	5110 Edgemoor Lane		5110 Edgemoor Lane
	Bethesda, MD 20814		Bethesda, MD 20814
	USA		USA
	EMail: steve@shinkuro.com		EMail: steve@shinkuro.com
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