draft-ietf-lamps-eai-addresses-18.txt		rfc8398.txt
	LAMPS A. Melnikov, Ed.		Internet Engineering Task Force (IETF) A. Melnikov, Ed.
	Internet-Draft Isode Ltd		Request for Comments: 8398 Isode Ltd
	Updates: 5280 (if approved) W. Chuang, Ed.		Updates: 5280 W. Chuang, Ed.
	Intended status: Standards Track Google, Inc.		Category: Standards Track Google, Inc.
	Expires: September 5, 2018 March 4, 2018		ISSN: 2070-1721 May 2018
	Internationalized Email Addresses in X.509 certificates		Internationalized Email Addresses in X.509 Certificates
	draft-ietf-lamps-eai-addresses-18
	Abstract		Abstract
	This document defines a new name form for inclusion in the otherName		This document defines a new name form for inclusion in the otherName
	field of an X.509 Subject Alternative Name and Issuer Alternative		field of an X.509 Subject Alternative Name and Issuer Alternative
	Name extension that allows a certificate subject to be associated		Name extension that allows a certificate subject to be associated
	with an Internationalized Email Address.		with an internationalized email address.
	This document updates RFC 5280.		This document updates RFC 5280.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This is an Internet Standards Track document.
	provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any		(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference		received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."		Internet Engineering Steering Group (IESG). Further information on
			Internet Standards is available in Section 2 of RFC 7841.
	This Internet-Draft will expire on September 5, 2018.		Information about the current status of this document, any errata,
			and how to provide feedback on it may be obtained at
			https://www.rfc-editor.org/info/rfc8398.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 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. Conventions Used in This Document . . . . . . . . . . . . . . 2		2. Conventions Used in This Document . . . . . . . . . . . . . . 2
	3. Name Definitions . . . . . . . . . . . . . . . . . . . . . . 2		3. Name Definitions . . . . . . . . . . . . . . . . . . . . . . 3
	4. IDNA2008 . . . . . . . . . . . . . . . . . . . . . . . . . . 4		4. IDNA2008 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	5. Matching of Internationalized Email Addresses in X.509		5. Matching of Internationalized Email Addresses in X.509
	certificates . . . . . . . . . . . . . . . . . . . . . . . . 4		Certificates . . . . . . . . . . . . . . . . . . . . . . . . 4
	6. Name constraints in path validation . . . . . . . . . . . . . 5		6. Name Constraints in Path Validation . . . . . . . . . . . . . 6
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
	9.1. Normative References . . . . . . . . . . . . . . . . . . 8		9.1. Normative References . . . . . . . . . . . . . . . . . . 8
	9.2. Informative References . . . . . . . . . . . . . . . . . 9		9.2. Informative References . . . . . . . . . . . . . . . . . 9
	Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 9		Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 10
	Appendix B. Example of SmtpUTF8Mailbox . . . . . . . . . . . . . 10		Appendix B. Example of SmtpUTF8Mailbox . . . . . . . . . . . . . 11
	Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 11		Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	[RFC5280] defines the rfc822Name subjectAltName name type for		[RFC5280] defines the rfc822Name subjectAltName name type for
	representing [RFC5321] email addresses. The syntax of rfc822Name is		representing email addresses as described in [RFC5321]. The syntax
	restricted to a subset of US-ASCII characters and thus can't be used		of rfc822Name is restricted to a subset of US-ASCII characters and
	to represent Internationalized Email addresses [RFC6531]. This		thus can't be used to represent internationalized email addresses
	document defines a new otherName variant to represent		[RFC6531]. This document defines a new otherName variant to
	Internationalized Email addresses. In addition this document		represent internationalized email addresses. In addition this
	requires all email address domains in X.509 certificates to conform		document requires all email address domains in X.509 certificates to
	to IDNA2008 [RFC5890].		conform to IDNA2008 [RFC5890].
	2. Conventions Used in This Document		2. Conventions Used in This Document
	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 [RFC2119].		"OPTIONAL" in this document are to be interpreted as described in
			BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
			capitals, as shown here.
	The formal syntax uses the Augmented Backus-Naur Form (ABNF)		The formal syntax uses the Augmented Backus-Naur Form (ABNF)
	[RFC5234] notation.		[RFC5234] notation.
	3. Name Definitions		3. Name Definitions
	The GeneralName structure is defined in [RFC5280], and supports many		The GeneralName structure is defined in [RFC5280] and supports many
	different name forms including otherName for extensibility. This		different name forms including otherName for extensibility. This
	section specifies the SmtpUTF8Mailbox name form of otherName, so that		section specifies the SmtpUTF8Mailbox name form of otherName so that
	Internationalized Email addresses can appear in the subjectAltName of		internationalized email addresses can appear in the subjectAltName of
	a certificate, the issuerAltName of a certificate, or anywhere else		a certificate, the issuerAltName of a certificate, or anywhere else
	that GeneralName is used.		that GeneralName is used.
	id-on-SmtpUTF8Mailbox OBJECT IDENTIFIER ::= { id-on 9 }		id-on-SmtpUTF8Mailbox OBJECT IDENTIFIER ::= { id-on 9 }
	SmtpUTF8Mailbox ::= UTF8String (SIZE (1..MAX))		SmtpUTF8Mailbox ::= UTF8String (SIZE (1..MAX))
	-- SmtpUTF8Mailbox conforms to Mailbox as specified		-- SmtpUTF8Mailbox conforms to Mailbox as specified
	-- in Section 3.3 of RFC 6531.		-- in Section 3.3 of RFC 6531.
	When the subjectAltName (or issuerAltName) extension contains an		When the subjectAltName (or issuerAltName) extension contains an
	Internationalized Email address with a non-ASCII local-part, the		internationalized email address with a non-ASCII local-part, the
	address MUST be stored in the SmtpUTF8Mailbox name form of otherName.		address MUST be stored in the SmtpUTF8Mailbox name form of otherName.
	The format of SmtpUTF8Mailbox is defined as the ABNF rule		The format of SmtpUTF8Mailbox is defined as the ABNF rule
	SmtpUTF8Mailbox. SmtpUTF8Mailbox is a modified version of the		SmtpUTF8Mailbox. SmtpUTF8Mailbox is a modified version of the
	Internationalized Mailbox which was defined in Section 3.3 of		internationalized Mailbox that was defined in Section 3.3 of
	[RFC6531] which was itself derived from SMTP Mailbox from		[RFC6531], which was derived from Mailbox as defined in Section 4.1.2
	Section 4.1.2 of [RFC5321]. [RFC6531] defines the following ABNF		of [RFC5321]. [RFC6531] defines the following ABNF rules for Mailbox
	rules for Mailbox whose parts are modified for internationalization:		whose parts are modified for internationalization: <Local-part>,
	<Local-part>, <Dot-string>, <Quoted-string>, <QcontentSMTP>,		<Dot-string>, <Quoted-string>, <QcontentSMTP>, <Domain>, and <Atom>.
	<Domain>, and <Atom>. In particular, <Local-part> was updated to		In particular, <Local-part> was updated to also support UTF8-non-
	also support UTF8-non-ascii. UTF8-non-ascii was described by		ascii. UTF8-non-ascii was described by Section 3.1 of [RFC6532].
	Section 3.1 of [RFC6532]. Also, domain was extended to support		Also, domain was extended to support U-labels, as defined in
	U-labels, as defined in [RFC5890].		[RFC5890].
	This document further refines Internationalized [RFC6531] Mailbox		This document further refines internationalized Mailbox ABNF rules as
	ABNF rules and calls this SmtpUTF8Mailbox. In SmtpUTF8Mailbox,		described in [RFC6531] and calls this SmtpUTF8Mailbox. In
	labels that include non-ASCII characters MUST be stored in U-label		SmtpUTF8Mailbox, labels that include non-ASCII characters MUST be
	(rather than A-label) [RFC5890] form. This restriction removes the		stored in U-label (rather than A-label) form [RFC5890]. This
	need to determine which label encoding A- or U-label is present in		restriction removes the need to determine which label encoding, A- or
	the Domain. As per Section 2.3.2.1 of [RFC5890], U-label are encoded		U-label, is present in the domain. As per Section 2.3.2.1 of
	as UTF-8 [RFC3629] in Normalization Form C and other properties		[RFC5890], U-labels are encoded as UTF-8 [RFC3629] in Normalization
	specified there. In SmtpUTF8Mailbox, domain labels that solely use		Form C and other properties specified there. In SmtpUTF8Mailbox,
	ASCII characters (meaning not A- nor U-labels) SHALL use NR-LDH		domain labels that solely use ASCII characters (meaning neither A-
	restrictions as specified by Section 2.3.1 of [RFC5890] and SHALL be		nor U-labels) SHALL use NR-LDH restrictions as specified by
	restricted to lower case letters. NR-LDH stands for "Non-Reserved		Section 2.3.1 of [RFC5890] and SHALL be restricted to lowercase
	Letters Digits Hyphen" and is the set of LDH labels that do not have		letters. NR-LDH stands for "Non-Reserved Letters Digits Hyphen" and
	"--" characters in the third and forth character position, which		is the set of LDH labels that do not have "--" characters in the
	excludes "tagged domain names" such as A-labels. Consistent with the		third and forth character position, which excludes "tagged domain
	treatment of rfc822Name in [RFC5280], SmtpUTF8Mailbox is an envelope		names" such as A-labels. Consistent with the treatment of rfc822Name
	<Mailbox> and has no phrase (such as a common name) before it, has no		in [RFC5280], SmtpUTF8Mailbox is an envelope <Mailbox> and has no
	comment (text surrounded in parentheses) after it, and is not		phrase (such as a common name) before it, has no comment (text
	surrounded by "<" and ">".		surrounded in parentheses) after it, and is not surrounded by "<" and
			">" characters.
	Due to name constraint compatibility reasons described in Section 6,		Due to name constraint compatibility reasons described in Section 6,
	SmtpUTF8Mailbox subjectAltName MUST NOT be used unless the local-part		SmtpUTF8Mailbox subjectAltName MUST NOT be used unless the local-part
	of the email address contains non-ASCII characters. When the local-		of the email address contains non-ASCII characters. When the local-
	part is ASCII, rfc822Name subjectAltName MUST be used instead of		part is ASCII, rfc822Name subjectAltName MUST be used instead of
	SmtpUTF8Mailbox. This is compatible with legacy software that		SmtpUTF8Mailbox. This is compatible with legacy software that
	supports only rfc822Name (and not SmtpUTF8Mailbox). The appropriate		supports only rfc822Name (and not SmtpUTF8Mailbox). The appropriate
	usage of rfc822Name and SmtpUTF8Mailbox is summarized in Table 1		usage of rfc822Name and SmtpUTF8Mailbox is summarized in Table 1
	below.		below.
	SmtpUTF8Mailbox is encoded as UTF8String. The UTF8String encoding		SmtpUTF8Mailbox is encoded as UTF8String. The UTF8String encoding
	MUST NOT contain a Byte-Order- Mark (BOM) [RFC3629] to aid		MUST NOT contain a Byte-Order-Mark (BOM) [RFC3629] to aid consistency
	consistency across implementations particularly for comparison.		across implementations, particularly for comparison.
	+-----------------+-------------+--------------+-----------------+		+-----------------+-------------+--------------+-----------------+
	| local-part char | domain char | domain label | subjectAltName |		| local-part char | domain char | domain label | subjectAltName |
	+-----------------+-------------+--------------+-----------------+		+-----------------+-------------+--------------+-----------------+
	| ASCII-only | ASCII-only | NR-LDH label | rfc822Name |		| ASCII-only | ASCII-only | NR-LDH label | rfc822Name |
	| non-ASCII | ASCII-only | NR-LDH label | SmtpUTF8Mailbox |		| non-ASCII | ASCII-only | NR-LDH label | SmtpUTF8Mailbox |
	| ASCII-only | non-ASCII | A-label | rfc822Name |		| ASCII-only | non-ASCII | A-label | rfc822Name |
	| non-ASCII | non-ASCII | U-label | SmtpUTF8Mailbox |		| non-ASCII | non-ASCII | U-label | SmtpUTF8Mailbox |
	+-----------------+-------------+--------------+-----------------+		+-----------------+-------------+--------------+-----------------+
	non-ASCII may additionally include ASCII characters.		Non-ASCII may additionally include ASCII characters.
	Table 1: Email address formatting		Table 1: Email Address Formatting
	4. IDNA2008		4. IDNA2008
	To facilitate comparison between email addresses, all email address		To facilitate comparison between email addresses, all email address
	domains in X.509 certificates MUST conform to IDNA2008 [RFC5890] (and		domains in X.509 certificates MUST conform to IDNA2008 [RFC5890] (and
	avoid any "mappings" mentioned in that document). Use of non-		avoid any "mappings" mentioned in that document). Use of
	conforming email address domains introduces the possibility of		non-conforming email address domains introduces the possibility of
	conversion errors between alternate forms. This applies to		conversion errors between alternate forms. This applies to
	SmtpUTF8Mailbox and rfc822Name in subjectAltName, issuerAltName and		SmtpUTF8Mailbox and rfc822Name in subjectAltName, issuerAltName, and
	anywhere else that these are used.		anywhere else that these are used.
	5. Matching of Internationalized Email Addresses in X.509 certificates		5. Matching of Internationalized Email Addresses in X.509 Certificates
	In equivalence comparison with SmtpUTF8Mailbox, there may be some		In equivalence comparison with SmtpUTF8Mailbox, there may be some
	setup work on one or both inputs depending of whether the input is		setup work on one or both inputs depending on whether the input is
	already in comparison form. Comparing SmtpUTF8Mailboxs consists of a		already in comparison form. Comparing SmtpUTF8Mailboxes consists of
	domain part step and a local-part step. The comparison form for		a domain part step and a local-part step. The comparison form for
	local-parts is always UTF-8. The comparison form for domain parts		local-parts is always UTF-8. The comparison form for domain parts
	depends on context. While some contexts such as certificate path		depends on context. While some contexts such as certificate path
	validation in [RFC5280] specify transforming domain to A-label		validation in [RFC5280] specify transforming domain to A-label
	(Section 7.5 and 7.2 in [RFC5280] as updated by		(Sections 7.2 and 7.5 in [RFC5280] as updated by [RFC8399]), this
	[ID-lamps-rfc5280-i18n-update]), this document recommends		document recommends transforming to UTF-8 U-label instead. This
	transforming to UTF-8 U-label instead. This reduces the likelihood		reduces the likelihood of errors by reducing conversions as more
	of errors by reducing conversions as more implementations natively		implementations natively support U-label domains.
	support U-label domains.
	Comparison of two SmtpUTF8Mailbox is straightforward with no setup		Comparison of two SmtpUTF8Mailboxes is straightforward with no setup
	work needed. They are considered equivalent if there is an exact		work needed. They are considered equivalent if there is an exact
	octet-for-octet match. Comparison with email addresses such as		octet-for-octet match. Comparison with email addresses such as
	Internationalized email address or rfc822Name requires additional		internationalized email address or rfc822Name requires additional
	setup steps for domain part and local-part. The initial preparation		setup steps for domain part and local-part. The initial preparation
	for the email addresses is to remove any phrases or comments, as well		for the email addresses is to remove any phrases, comments, and "<"
	as "<" and ">" present. This document calls for comparison of domain		or ">" characters. This document calls for comparison of domain
	labels that include non-ASCII characters be transformed to U-label if		labels that include non-ASCII characters to be transformed to
	not already in that form. The first step is to detect use of the		U-labels if not already in that form. The first step is to detect
	A-label by using Section 5.1 of [RFC5891]. Next if necessary,		use of the A-label by using Section 5.1 of [RFC5891]. Next, if
	transform any A-labels to U-labels Unicode as specified in		necessary, transform any A-labels (US-ASCII) to U-labels (Unicode) as
	Section 5.2 of [RFC5891]. Finally if necessary convert the Unicode		specified in Section 5.2 of [RFC5891]. Finally, if necessary,
	to UTF-8 as specified in Section 3 of [RFC3629]. For ASCII NR-LDH		convert the Unicode to UTF-8 as specified in Section 3 of [RFC3629].
	labels, upper case letters are converted to lower case letters. In		For ASCII NR-LDH labels, uppercase letters are converted to lowercase
	setup for SmtpUTF8Mailbox, the email address local-part MUST conform		letters. In setup for SmtpUTF8Mailbox, the email address local-part
	to the requirements of [RFC6530] and [RFC6531], including being a		MUST conform to the requirements of [RFC6530] and [RFC6531],
	string in UTF-8 form. In particular, the local-part MUST NOT be		including being a string in UTF-8 form. In particular, the local-
	transformed in any way, such as by doing case folding or		part MUST NOT be transformed in any way, such as by doing case
	normalization of any kind. The <Local-part> part of an		folding or normalization of any kind. The <Local-part> part of an
	Internationalized email address is already in UTF-8. For rfc822Name		internationalized email address is already in UTF-8. For rfc822Name,
	the local-part, which is IA5String (ASCII), trivially maps to UTF-8		the local-part, which is IA5String (ASCII), trivially maps to UTF-8
	without change. Once setup is complete, they are again compared		without change. Once setup is complete, they are again compared
	octet-for-octet.		octet for octet.
	To summarize non-normatively, the comparison steps including setup		To summarize non-normatively, the comparison steps, including setup,
	are:		are:
	1. If the domain contains A-labels, transform them to U-labels.		1. If the domain contains A-labels, transform them to U-labels.
	2. If the domain contains ASCII NR-LDH labels, lowercase them.		2. If the domain contains ASCII NR-LDH labels, lowercase them.
	3. Compare strings octet-for-octet for equivalence.		3. Compare strings octet for octet for equivalence.
	This specification expressly does not define any wildcard characters		This specification expressly does not define any wildcard characters,
	and SmtpUTF8Mailbox comparison implementations MUST NOT interpret any		and SmtpUTF8Mailbox comparison implementations MUST NOT interpret any
	character as wildcards. Instead, to specify multiple email addresses		characters as wildcards. Instead, to specify multiple email
	through SmtpUTF8Mailbox, the certificate MUST use multiple		addresses through SmtpUTF8Mailbox, the certificate MUST use multiple
	subjectAltNames or issuerAltNames to explicitly carry any additional		subjectAltNames or issuerAltNames to explicitly carry any additional
	email addresses.		email addresses.
	6. Name constraints in path validation		6. Name Constraints in Path Validation
	This section updates Section 4.2.1.10 of [RFC5280] to extend		This section updates Section 4.2.1.10 of [RFC5280] to extend
	rfc822Name name constraints to SmtpUTF8Mailbox subjectAltNames. A		rfc822Name name constraints to SmtpUTF8Mailbox subjectAltNames.
	SmtpUTF8Mailbox aware path validators will apply name constraint		SmtpUTF8Mailbox-aware path validators will apply name constraint
	comparison to the subject distinguished name and both forms of		comparison to the subject distinguished name and both forms of
	subject alternative name rfc822Name and SmtpUTF8Mailbox.		subject alternative names rfc822Name and SmtpUTF8Mailbox.
	Both rfc822Name and SmtpUTF8Mailbox subject alternative names		Both rfc822Name and SmtpUTF8Mailbox subject alternative names
	represent the same underlying email address namespace. Since legacy		represent the same underlying email address namespace. Since legacy
	CAs constrained to issue certificates for a specific set of domains		CAs constrained to issue certificates for a specific set of domains
	would lack corresponding UTF-8 constraints,		would lack corresponding UTF-8 constraints, [RFC8399] updates,
	[ID-lamps-rfc5280-i18n-update] updates modifies and extends		modifies, and extends rfc822Name name constraints defined in
	rfc822Name name constraints defined in [RFC5280] to cover		[RFC5280] to cover SmtpUTF8Mailbox subject alternative names. This
	SmtpUTF8Mailbox subject alternative names. This ensures that the		ensures that the introduction of SmtpUTF8Mailbox does not violate
	introduction of SmtpUTF8Mailbox does not violate existing name		existing name constraints. Since it is not valid to include
	constraints. Since it is not valid to include non-ASCII UTF-8		non-ASCII UTF-8 characters in the local-part of rfc822Name name
	characters in the local-part of rfc822Name name constraints, and		constraints, and since name constraints that include a local-part are
	since name constraints that include a local-part are rarely, if at		rarely, if at all, used in practice, name constraints updated in
	all, used in practice, name constraints updated in		[RFC8399] allow the forms that represent all addresses at a host or
	[ID-lamps-rfc5280-i18n-update] admit the forms that represent all		all mailboxes in a domain and deprecates rfc822Name name constraints
	addresses at a host or all mailboxes in a domain, and deprecates		that represent a particular mailbox. That is, rfc822Name constraints
	rfc822Name name constraints that represent a particular mailbox.		with a local-part SHOULD NOT be used.
	That is, rfc822Name constraints with a local-part SHOULD NOT be used.
	Constraint comparison with SmtpUTF8Mailbox subjectAltName starts with		Constraint comparison with SmtpUTF8Mailbox subjectAltName starts with
	the setup steps defined by Section 5. Setup converts the inputs of		the setup steps defined by Section 5. Setup converts the inputs of
	the comparison which is one of a subject distinguished name or a		the comparison (which is one of a subject distinguished name, an
	rfc822Name or SmtpUTF8Mailbox subjectAltName, and one of a rfc822Name		rfc822Name, or an SmtpUTF8Mailbox subjectAltName, and one of an
	name constraint, to constraint comparison form. For rfc822Name name		rfc822Name name constraint) to constraint comparison form. For an
	constraint, this will convert any domain A-labels to U-labels. For		rfc822Name name constraint, this will convert any domain A-labels to
	both the name constraint and the subject, this will lower case any		U-labels. For both the name constraint and the subject, this will
	domain NR-LDH labels. Strip the local-part and "@" separator from		lowercase any domain NR-LDH labels. Strip the local-part and "@"
	each rfc822Name and SmtpUTF8Mailbox, leaving just the domain-part.		separator from each rfc822Name and SmtpUTF8Mailbox, leaving just the
	After setup, this follows the comparison steps defined in 4.2.1.10 of		domain part. After setup, this follows the comparison steps defined
	[RFC5280] as follows. If the resulting name constraint domain starts		in Section 4.2.1.10 of [RFC5280] as follows. If the resulting name
	with a "." character, then for the name constraint to match, a suffix		constraint domain starts with a "." character, then for the name
	of the resulting subject alternative name domain MUST match the name		constraint to match, a suffix of the resulting subject alternative
	constraint (including the leading ".") octet for octet. If the		name domain MUST match the name constraint (including the leading
	resulting name constraint domain does not start with a "." character,		".") octet for octet. If the resulting name constraint domain does
	then for the name constraint to match, the entire resulting subject		not start with a "." character, then for the name constraint to
	alternative name domain MUST match the name constraint octet for		match, the entire resulting subject alternative name domain MUST
	octet.		match the name constraint octet for octet.
	Certificate Authorities that wish to issue CA certificates with email		Certificate Authorities that wish to issue CA certificates with email
	address name constraint MUST use rfc822Name subject alternative names		address name constraints MUST use rfc822Name subject alternative
	only. These MUST be IDNA2008 conformant names with no mappings, and		names only. These MUST be IDNA2008-conformant names with no mappings
	with non-ASCII domains encoded in A-labels only.		and with non-ASCII domains encoded in A-labels only.
	The name constraint requirement with SmtpUTF8Mailbox subject		The name constraint requirement with SmtpUTF8Mailbox subject
	alternative name is illustrated in the non-normative diagram		alternative name is illustrated in the non-normative diagram in
	Figure 1. The first example (1) illustrates a permitted rfc822Name		Figure 1. The first example (1) illustrates a permitted rfc822Name
	ASCII only hostname name constraint, and the corresponding valid		ASCII-only host name name constraint and the corresponding valid
	rfc822Name subjectAltName and SmtpUTF8Mailbox subjectAltName email		rfc822Name subjectAltName and SmtpUTF8Mailbox subjectAltName email
	addresses. The second example (2) illustrates a permitted rfc822Name		addresses. The second example (2) illustrates a permitted rfc822Name
	hostname name constraint with A-label, and the corresponding valid		host name name constraint with A-label, and the corresponding valid
	rfc822Name subjectAltName and SmtpUTF8Mailbox subjectAltName email		rfc822Name subjectAltName and SmtpUTF8Mailbox subjectAltName email
	addresses. Note that an email address with ASCII only local-part is		addresses. Note that an email address with ASCII-only local-part is
	encoded as rfc822Name despite also having unicode present in the		encoded as rfc822Name despite also having Unicode present in the
	domain.		domain.
	+-------------------------------------------------------------------+		+-------------------------------------------------------------------+
	| Root CA Cert |		| Root CA Cert |
	+-------------------------------------------------------------------+		+-------------------------------------------------------------------+
	|		|
	v		v
	+-------------------------------------------------------------------+		+-------------------------------------------------------------------+
	| Intermediate CA Cert |		| Intermediate CA Cert |
	| Permitted |		| Permitted |
	skipping to change at page 7, line 34 ¶		skipping to change at page 7, line 44 ¶
	| SubjectAltName Extension |		| SubjectAltName Extension |
	| rfc822Name: student@elemenary.school.example.com (1) |		| rfc822Name: student@elemenary.school.example.com (1) |
	| SmtpUTF8Mailbox: u+5B66u+751F@elementary.school.example.com |		| SmtpUTF8Mailbox: u+5B66u+751F@elementary.school.example.com |
	| (1) |		| (1) |
	| |		| |
	| rfc822Name: student@xn--pss25c.example.com (2) |		| rfc822Name: student@xn--pss25c.example.com (2) |
	| SmtpUTF8Mailbox: u+533Bu+751F@u+5927u+5B66.example.com (2) |		| SmtpUTF8Mailbox: u+533Bu+751F@u+5927u+5B66.example.com (2) |
	| |		| |
	+-------------------------------------------------------------------+		+-------------------------------------------------------------------+
	Name constraints with SmtpUTF8Name and rfc822Name		Figure 1: Name Constraints with SmtpUTF8Name and rfc822Name
	Figure 1
	7. Security Considerations		7. Security Considerations
	Use of SmtpUTF8Mailbox for certificate subjectAltName (and		Use of SmtpUTF8Mailbox for certificate subjectAltName (and
	issuerAltName) will incur many of the same security considerations as		issuerAltName) will incur many of the same security considerations as
	in Section 8 in [RFC5280], but introduces a new issue by permitting		in Section 8 in [RFC5280], but it introduces a new issue by
	non-ASCII characters in the email address local-part. This issue, as		permitting non-ASCII characters in the email address local-part.
	mentioned in Section 4.4 of [RFC5890] and in Section 4 of [RFC6532],		This issue, as mentioned in Section 4.4 of [RFC5890] and in Section 4
	is that use of Unicode introduces the risk of visually similar and		of [RFC6532], is that use of Unicode introduces the risk of visually
	identical characters which can be exploited to deceive the recipient.		similar and identical characters that can be exploited to deceive the
	The former document references some means to mitigate against these		recipient. The former document references some means to mitigate
	attacks. See [WEBER] for more background on security issues with		against these attacks. See [WEBER] for more background on security
	Unicode.		issues with Unicode.
	8. IANA Considerations		8. IANA Considerations
	In Section 3 and the ASN.1 module identifier defined in Appendix A.		As described in Section 3 and the ASN.1 module identifier defined in
	IANA is kindly requested to make the following assignments for:		Appendix A, IANA has assigned the values described here.
	The LAMPS-EaiAddresses-2016 ASN.1 module in the "SMI Security for		o For the LAMPS-EaiAddresses-2016 ASN.1 module, IANA has registered
	PKIX Module Identifier" registry (1.3.6.1.5.5.7.0).		value 92 for "id-mod-lamps-eai-addresses-2016" in the "SMI
			Security for PKIX Module Identifier" (1.3.6.1.5.5.7.0) registry.
	The SmtpUTF8Mailbox otherName in the "PKIX Other Name Forms"		o For the SmtpUTF8Mailbox otherName, IANA has registered value 9 for
	registry (1.3.6.1.5.5.7.8). {{ Note to IANA: id-on-smtputf8Name		id-on-SmtpUTF8Mailbox in the "SMI Security for PKIX Other Name
	was assigned based on an earlier version of this document. Please		Forms" (1.3.6.1.5.5.7.8) registry.
	change that entry to id-on-SmtpUTF8Mailbox. }}
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[ID-lamps-rfc5280-i18n-update]
	Housley, R., "Internationalization Updates to RFC 5280",
	June 2017, <https://datatracker.ietf.org/doc/
	draft-housley-rfc5280-i18n-update/>.
	[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>.
	[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO		[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
	10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November		10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
	2003, <https://www.rfc-editor.org/info/rfc3629>.		2003, <https://www.rfc-editor.org/info/rfc3629>.
	[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax		[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
	skipping to change at page 9, line 27 ¶		skipping to change at page 9, line 27 ¶
	February 2012, <https://www.rfc-editor.org/info/rfc6530>.		February 2012, <https://www.rfc-editor.org/info/rfc6530>.
	[RFC6531] Yao, J. and W. Mao, "SMTP Extension for Internationalized		[RFC6531] Yao, J. and W. Mao, "SMTP Extension for Internationalized
	Email", RFC 6531, DOI 10.17487/RFC6531, February 2012,		Email", RFC 6531, DOI 10.17487/RFC6531, February 2012,
	<https://www.rfc-editor.org/info/rfc6531>.		<https://www.rfc-editor.org/info/rfc6531>.
	[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized		[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized
	Email Headers", RFC 6532, DOI 10.17487/RFC6532, February		Email Headers", RFC 6532, DOI 10.17487/RFC6532, February
	2012, <https://www.rfc-editor.org/info/rfc6532>.		2012, <https://www.rfc-editor.org/info/rfc6532>.
			[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
			[RFC8399] Housley, R., "Internationalization Updates to RFC 5280",
			RFC 8399, DOI 10.17487/RFC8399, May 2018,
			<https://www.rfc-editor.org/info/rfc8399>.
	9.2. Informative References		9.2. Informative References
	[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the		[RFC5912] Hoffman, P. and J. Schaad, "New ASN.1 Modules for the
	Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,		Public Key Infrastructure Using X.509 (PKIX)", RFC 5912,
	DOI 10.17487/RFC5912, June 2010,		DOI 10.17487/RFC5912, June 2010,
	<https://www.rfc-editor.org/info/rfc5912>.		<https://www.rfc-editor.org/info/rfc5912>.
	[WEBER] Weber, C., "Attacking Software Globalization", March 2010,		[WEBER] Weber, C., "Attacking Software Globalization", March 2010,
	<https://www.lookout.net/files/		<https://www.lookout.net/files/
	Chris_Weber_Character%20Transformations%20v1.7_IUC33.pdf>.		Chris_Weber_Character%20Transformations%20v1.7_IUC33.pdf>.
	skipping to change at page 10, line 8 ¶		skipping to change at page 10, line 15 ¶
	Appendix A. ASN.1 Module		Appendix A. ASN.1 Module
	The following ASN.1 module normatively specifies the SmtpUTF8Mailbox		The following ASN.1 module normatively specifies the SmtpUTF8Mailbox
	structure. This specification uses the ASN.1 definitions from		structure. This specification uses the ASN.1 definitions from
	[RFC5912] with the 2002 ASN.1 notation used in that document.		[RFC5912] with the 2002 ASN.1 notation used in that document.
	[RFC5912] updates normative documents using older ASN.1 notation.		[RFC5912] updates normative documents using older ASN.1 notation.
	LAMPS-EaiAddresses-2016		LAMPS-EaiAddresses-2016
	{ iso(1) identified-organization(3) dod(6)		{ iso(1) identified-organization(3) dod(6)
	internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)		internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
	id-mod-lamps-eai-addresses-2016(TBD) }		id-mod-lamps-eai-addresses-2016(92) }
	DEFINITIONS IMPLICIT TAGS ::=		DEFINITIONS IMPLICIT TAGS ::=
	BEGIN		BEGIN
	IMPORTS		IMPORTS
	OTHER-NAME		OTHER-NAME
	FROM PKIX1Implicit-2009		FROM PKIX1Implicit-2009
	{ iso(1) identified-organization(3) dod(6) internet(1) security(5)		{ iso(1) identified-organization(3) dod(6) internet(1) security(5)
	mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-implicit-02(59) }		mechanisms(5) pkix(7) id-mod(0) id-mod-pkix1-implicit-02(59) }
	skipping to change at page 11, line 23 ¶		skipping to change at page 11, line 29 ¶
	16 18: UTF8String '..@example.com'		16 18: UTF8String '..@example.com'
	: }		: }
	: }		: }
	Figure 2		Figure 2
	The example was encoded on the OSS Nokalva ASN.1 Playground and the		The example was encoded on the OSS Nokalva ASN.1 Playground and the
	above text decoding is an output of Peter Gutmann's "dumpasn1"		above text decoding is an output of Peter Gutmann's "dumpasn1"
	program.		program.
	Appendix C. Acknowledgements		Acknowledgements
	Thank you to Magnus Nystrom for motivating this document. Thanks to		Thank you to Magnus Nystrom for motivating this document. Thanks to
	Russ Housley, Nicolas Lidzborski, Laetitia Baudoin, Ryan Sleevi, Sean		Russ Housley, Nicolas Lidzborski, Laetitia Baudoin, Ryan Sleevi, Sean
	Leonard, Sean Turner, John Levine, and Patrik Falstrom for their		Leonard, Sean Turner, John Levine, and Patrik Falstrom for their
	feedback. Also special thanks to John Klensin for his valuable input		feedback. Also special thanks to John Klensin for his valuable input
	on internationalization, Unicode and ABNF formatting, to Jim Schaad		on internationalization, Unicode, and ABNF formatting; to Jim Schaad
	for his help with the ASN.1 example and his helpful feedback, and		for his help with the ASN.1 example and his helpful feedback; and
	especially to Viktor Dukhovni for helping us with name constraints		especially to Viktor Dukhovni for helping us with name constraints
	and his many detailed document reviews.		and his many detailed document reviews.
	Authors' Addresses		Authors' Addresses
	Alexey Melnikov (editor)		Alexey Melnikov (editor)
	Isode Ltd		Isode Ltd
	14 Castle Mews		14 Castle Mews
	Hampton, Middlesex TW12 2NP		Hampton, Middlesex TW12 2NP
	UK		United Kingdom
	Email: Alexey.Melnikov@isode.com		Email: Alexey.Melnikov@isode.com
	Weihaw Chuang (editor)		Weihaw Chuang (editor)
	Google, Inc.		Google, Inc.
	1600 Amphitheater Parkway		1600 Amphitheater Parkway
	Mountain View, CA 94043		Mountain View, CA 94043
	US		United States of America
	Email: weihaw@google.com		Email: weihaw@google.com
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