< draft-ietf-dnsext-dnssec-algo-signal-06.txt		draft-ietf-dnsext-dnssec-algo-signal-07.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: November 2, 2012 NIST		Expires: December 16, 2012 NIST
	May 1, 2012		June 14, 2012
	Signaling Cryptographic Algorithm Understanding in DNSSEC		Signaling Cryptographic Algorithm Understanding in DNSSEC
	draft-ietf-dnsext-dnssec-algo-signal-06		draft-ietf-dnsext-dnssec-algo-signal-07
	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		validating end-system resolvers to signal to a server which digital
	cryptographic algorithms and hash algorithms they support.		signature and hash algorithms they support.
	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", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	document are to be interpreted as described in RFC 2119 [RFC2119].		"OPTIONAL" in this document are to be interpreted as described in RFC
			2119 [RFC2119].
	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
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 November 2, 2012.		This Internet-Draft will expire on December 16, 2012.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 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
	skipping to change at page 3, line 11 ¶		skipping to change at page 3, line 11 ¶
	8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7		8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
	9. Normative References . . . . . . . . . . . . . . . . . . . . . 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 tells 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) RR's and NSEC3 RR's use a hashed		Likewise, Delegation Signer (DS) RRs and NSEC3 RRs use a hashed value
	value as part of their RDATA and, like digital signature algorithms,		as part of their RDATA and, like digital signature algorithms, these
	these hash algorithms have code numbers. All three algorithm codes		hash algorithms have code numbers. All three algorithm codes (RRSIG/
	(RRSIG/DNSKEY, DS and NSEC3) are maintained in unique IANA		DNSKEY, DS and NSEC3) are maintained in unique IANA registries.
	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/or hash algorithms they support. This is done using the new EDNS		and/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].		[I-D.ietf-dnsext-rfc2671bis-edns0].
	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 a 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 may be able to determine when to stop signing with a		administrator is able to determine when to stop signing with a
	superseded algorithm when the server sees that a significant number		superseded algorithm when the server sees that a significant number
	of its clients signal that they are able to accept the new algorithm.		of its clients signal that they are able to accept the new algorithm.
	Note that this survey may be conducted over the period of years		Note that this survey may be conducted over the period of years
	before a tipping point is seen.		before a tipping point is seen.
	This draft does not seek to introduce another process for including		This draft does not seek to introduce another process for including
	new algorithms for use with DNSSEC. It also does not address the		new algorithms for use with DNSSEC. It also does not address the
	question of which algorithms are to be included in any official list		question of which algorithms are to be included in any official list
	of mandatory or recommended cryptographic algorithms for use with		of mandatory or recommended cryptographic algorithms for use with
	DNSSEC. Rather, this document specifies a means by which a client		DNSSEC. Rather, this document specifies a means by which a client
	query can signal a set of algorithms and hashes it implements.		query can signal the set of algorithms and hashes which it
			implements.
	2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood		2. Signaling DNSSEC Algorithm Understood (DAU), DS Hash Understood
	(DHU) and NSEC3 Hash Understood (N3U) Using EDNS		(DHU) and NSEC3 Hash Understood (N3U) Using EDNS
	The ENDS0 specification outlined in		The EDNS0 specification outlined in
	[I-D.ietf-dnsext-rfc2671bis-edns0] defines a way to include new		[I-D.ietf-dnsext-rfc2671bis-edns0] defines a way to include new
	options using a standardized mechanism. These options are contained		options using a standardized mechanism. These options are contained
	in the RDATA of the OPT meta-RR. This document defines three new		in the RDATA of the OPT meta-RR. This document defines three new
	EDNS options for a client to signal which digital signature and/or		EDNS options for a client to signal which digital signature and/or
	hash algorithms the client supports. These options can be used		hash algorithms the client supports. These options can be used
	independently of each other and MAY appear in any order in the OPT		independently of each other and MAY appear in any order in the OPT
	RR.		RR.
	The figure below shows how each option is defined in the RDATA of the		The figure below shows how each option is defined in the RDATA of the
	OPT RR specified in [I-D.ietf-dnsext-rfc2671bis-edns0]:		OPT RR specified in [I-D.ietf-dnsext-rfc2671bis-edns0]:
	skipping to change at page 4, line 37 ¶		skipping to change at page 4, line 37 ¶
	o NSEC3 Hash Understood (N3U) option for NSEC3 hash algorithms. Its		o NSEC3 Hash Understood (N3U) option for NSEC3 hash algorithms. Its
	value is fixed at TBD3.		value is fixed at TBD3.
	LIST-LENGTH is the length of the list of digital signature or hash		LIST-LENGTH is the length of the list of digital signature or hash
	algorithm codes in octets. Each algorithm code occupies a single		algorithm codes in octets. Each algorithm code occupies a single
	octet.		octet.
	ALG-CODE is the list of assigned values of DNSSEC zone signing		ALG-CODE is the list of assigned values of DNSSEC zone signing
	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 values SHOULD be in descending order of preference, with the most		The values are listed in descending order of preference, with the
	preferred algorithm first. For example, if a validating client		most preferred algorithm first. For example, if a validating client
	signals the DAU option and RSA/SHA-1, RSA/SHA-256 and prefers the		signals the DAU option and RSA/SHA-1, RSA/SHA-256 and prefers the
	latter, the values of ALG-CODE would be: 8 (RSA/SHA-256), 5 (RSA/		latter, the values of ALG-CODE would be: 8 (RSA/SHA-256), 5 (RSA/
	SHA-1).		SHA-1).
	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 22-34 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 reasonable potential future		EDNS option codes and option lengths in a potential future example.
	example.
	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 sets the value(s) in the order of		validating end-system resolver sets the value(s) in the order of
	preference, with the most preferred algorithm(s) first as described		preference, with the most preferred algorithm(s) first as described
	in section 2. The end-system resolver SHOULD also set the DNSSEC-OK		in section 2. The validating end-system resolver MUST also set the
	bit [RFC4035] to indicate that it wishes to receive DNSSEC RRs in the		DNSSEC-OK bit [RFC4035] to indicate that it wishes to receive DNSSEC
	response.		RRs in the 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.
	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
	A validating stub resolver already (usually) sets the DO bit		A validating stub resolver already (usually) sets the DO bit
	[RFC4035] to indicate that it wishes to receive additional DNSSEC RRs		[RFC4035] to indicate that it wishes to receive additional DNSSEC RRs
	(i.e. RRSIG RR's) in the response. Such validating resolvers SHOULD		(i.e. RRSIG RRs) in the response. Such validating resolvers SHOULD
	include the DAU, DHU and/or the N3U option(s) in the OPT RR when		include the DAU, DHU and/or the N3U option(s) in the OPT RR when
	sending a query. This way the validating stub resolver indicates		sending a query. The way the validating stub resolver indicates
	which cryptographic algorithm(s) it supports by setting the values in		which cryptographic algorithm(s) it supports by setting the values in
	the order of preference, with the most preferred algorithm first as		the order of preference, with the most preferred algorithm first as
	described in Section 2.		described in Section 2.
	3.1.2. Non-Validating Stub Resolvers		3.1.2. Non-Validating Stub Resolvers
	The DAU, DHU and N3U EDNS options are NOT RECOMMENDED for non-		The DAU, DHU and N3U EDNS options are NOT RECOMMENDED for non-
	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 the DO and CD flags in		option(s) when performing recursion based on the DO and CD flags in
	the client request [RFC4035]. If the client of the recursive		the client request [RFC4035]. If the client of the recursive
	resolver did not include the DO bit in the query the recursive		resolver did not include the DO bit in the query the recursive
	resolver SHOULD include the option(s) according to its own local		resolver MAY include the option(s) according to its own local policy.
	policy.
	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 SHOULD NOT include the option(s) to avoid conflicts.		resolver MUST NOT include the option(s) to avoid conflicts.
	If the client did set the DO bit and the option(s) in the query, the		If the client did set the DO bit and the option(s) in the query, the
	validating recursive resolver SHOULD include the option(s) based on		validating recursive resolver MUST include the option(s) based on the
	the setting of the CD bit. If the CD bit is set, the validating		setting of the CD bit. If the CD bit is set, the validating
	recursive resolver SHOULD include the option(s) based on the client		recursive resolver MUST include the option(s) based on the client
	query or a superset of the client option(s) list and the validator's		query or a superset of the client option(s) list and the validator's
	own list (if different). If the CD bit is not set, the validating		own list (if different). If the CD bit is not set, the validating
	recursive resolver MAY copy the client option(s) or substitute its		recursive resolver MAY copy the client option(s) or substitute its
	own option list.		own option list.
	3.2.2. Non-validating Recursive Resolvers		3.2.2. Non-validating Recursive Resolvers
	Recursive resolvers that do not do validation SHOULD copy the DAU,		Recursive resolvers that do not do validation MUST copy the DAU, DHU
	DHU and/or N3U option(s) seen in received queries as they represent		and/or N3U option(s) seen in received queries as they represent the
	the wishes of the validating downstream resolver that issued the		wishes of the validating downstream resolver that issued the original
	original query.		query.
	4. Intermediate System Considerations		4. Intermediate System Considerations
	Intermediate proxies [RFC5625] that understand DNS SHOULD behave like		Intermediate proxies [RFC5625] that understand DNS are RECOMMENDED to
	a comparable recursive resolver when dealing with the DAU, DHU and		behave like a comparable recursive resolver when dealing with the
	N3U options.		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
	skipping to change at page 7, line 33 ¶		skipping to change at page 7, line 32 ¶
	The algorithm codes used to identify DNSSEC algorithms, DS RR hash		The algorithm codes used to identify DNSSEC algorithms, DS RR hash
	algorithms and NSEC3 hash algorithms have already been established by		algorithms and NSEC3 hash algorithms have already been established by
	IANA. This document does not seek to alter that registry in any way.		IANA. This document does not seek to alter that registry in any way.
	This draft seeks to update the "DNS EDNS Options" registry by adding		This draft seeks to update the "DNS EDNS Options" registry by adding
	the DAU, DHU and N3U options and referencing this document. The code		the DAU, DHU and N3U options and referencing this document. The code
	for these options are TBD1, TBD2 and TBD3 respectively.		for these options are TBD1, TBD2 and TBD3 respectively.
	8. Security Considerations		8. Security Considerations
	This document specifies a way for a client to signal its		This document specifies a way for a client to signal its digital
	cryptographic and hash algorithm knowledge to a cache or server. It		signature and hash algorithm knowledge to a cache or server. It is
	is not meant to be a discussion on algorithm superiority. The		not meant to be a discussion on algorithm superiority. The signals
	signals are optional codes contained in the OPT meta-RR used with		are optional codes contained in the OPT meta-RR used with EDNS. The
	EDNS. The goal of these options are to signal new algorithm uptake		goal of these options are to signal new algorithm uptake in client
	in client code to allow zone administrators to know when it is		code to allow zone administrators to know when it is possible to
	possible to complete an algorithm rollover in a DNSSEC signed zone.		complete an algorithm rollover in a DNSSEC signed zone.
	9. Normative References		9. Normative References
	[I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P.		[I-D.ietf-dnsext-rfc2671bis-edns0] Damas, J., Graff, M., and P.
	Vixie, "Extension Mechanisms for		Vixie, "Extension Mechanisms for
	DNS (EDNS0)", draft-ietf-dnsext-		DNS (EDNS0)", draft-ietf-dnsext-
	rfc2671bis-edns0-08 (work in		rfc2671bis-edns0-08 (work in
	progress), February 2012.		progress), February 2012.
	[RFC2119] Bradner, S., "Key words for use		[RFC2119] Bradner, S., "Key words for use
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