draft-ietf-uta-email-tls-certs-05.txt		draft-ietf-uta-email-tls-certs-06.txt
	Network Working Group A. Melnikov		Network Working Group A. Melnikov
	Internet-Draft Isode Ltd		Internet-Draft Isode Ltd
	Updates: 2595, 3207, 3501, 5804 (if September 20, 2015		Updates: 2595, 3207, 3501, 5804 (if December 4, 2015
	approved)		approved)
	Intended status: Standards Track		Intended status: Standards Track
	Expires: March 23, 2016		Expires: June 6, 2016
	Updated TLS Server Identity Check Procedure for Email Related Protocols		Updated TLS Server Identity Check Procedure for Email Related Protocols
	draft-ietf-uta-email-tls-certs-05		draft-ietf-uta-email-tls-certs-06
	Abstract		Abstract
	This document describes TLS server identity verification procedure		This document describes TLS server identity verification procedure
	for SMTP Submission, IMAP, POP and ManageSieve clients. It replaces		for SMTP Submission, IMAP, POP and ManageSieve clients. It replaces
	Section 2.4 of RFC 2595, updates Section 4.1 of RFC 3207, updates		Section 2.4 of RFC 2595, updates Section 4.1 of RFC 3207, updates
	Section 11.1 of RFC 3501, updates Section 2.2.1 of RFC 5804.		Section 11.1 of RFC 3501, updates Section 2.2.1 of RFC 5804.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 35		skipping to change at page 1, line 35
	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 23, 2016.		This Internet-Draft will expire on June 6, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 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 2, line 12		skipping to change at page 2, line 12
	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 . . . . . . . . . . . . . . 3		2. Conventions Used in This Document . . . . . . . . . . . . . . 3
	3. Email Server Certificate Verification Rules . . . . . . . . . 3		3. Email Server Certificate Verification Rules . . . . . . . . . 3
	4. Compliance Checklist for Certification Authorities . . . . . 4		4. Compliance Checklist for Certification Authorities . . . . . 5
			4.1. Notes on handling of SRV-ID by Certificate Authorities . 5
	5. Compliance Checklist for Mail Service Providers and		5. Compliance Checklist for Mail Service Providers and
	Certificate Signing Request generation tools . . . . . . . . 4		Certificate Signing Request generation tools . . . . . . . . 5
	6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5		5.1. Notes on hosted domains . . . . . . . . . . . . . . . . . 6
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 6		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	9.1. Normative References . . . . . . . . . . . . . . . . . . 6		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	9.2. Informative References . . . . . . . . . . . . . . . . . 7		9.1. Normative References . . . . . . . . . . . . . . . . . . 7
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9		9.2. Informative References . . . . . . . . . . . . . . . . . 8
	Appendix B. Changes since draft-ietf-uta-email-tls-certs-00 . . 9		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 10
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9		Appendix B. Changes since draft-ietf-uta-email-tls-certs-00 . . 10
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Introduction		1. Introduction
	Use of TLS by SMTP Submission, IMAP, POP and ManageSieve clients is		Use of TLS by SMTP Submission, IMAP, POP and ManageSieve clients is
	described in [RFC3207], [RFC3501], [RFC2595] and [RFC5804]		described in [RFC3207], [RFC3501], [RFC2595] and [RFC5804]
	respectively. Each of the documents describes slightly different		respectively. Each of the documents describes slightly different
	rules for server certificate identity verification (or doesn't define		rules for server certificate identity verification (or doesn't define
	any rules at all). In reality, email client and server developers		any rules at all). In reality, email client and server developers
	implement many of these protocols at the same time, so it would be		implement many of these protocols at the same time, so it would be
	good to define modern and consistent rules for verifying email server		good to define modern and consistent rules for verifying email server
	identities using TLS.		identities using TLS.
	This document describes the updated TLS server identity verification		This document describes the updated TLS server identity verification
	procedure for SMTP Submission [RFC6409] [RFC3207], IMAP [RFC3501],		procedure for SMTP Submission [RFC6409] [RFC3207], IMAP [RFC3501],
	POP [RFC1939] and ManageSieve [RFC5804] clients. It replaces		POP [RFC1939] and ManageSieve [RFC5804] clients. It replaces
	Section 2.4 of RFC 2595.		Section 2.4 of RFC 2595.
	Note that this document doesn't apply to use of TLS in MTA-to-MTA		Note that this document doesn't apply to use of TLS in MTA-to-MTA
	SMTP.		SMTP.
	The main goal of the document is to provide consistent TLS server		This document provides a consistent TLS server identity verification
	identity verification procedure across multiple email related		procedure across multiple email related protocols. This should make
	protocols. This should make it easier for Certification Authorities		it easier for Certification Authorities and ISPs to deploy TLS for
	and ISPs to deploy TLS for email use, and would enable email client		email use, and would enable email client developers to write more
	developers to write more secure code.		secure code.
	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", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	The following terms or concepts are used through the document:		The following terms or concepts are used through the document:
	reference identifier: (as defined in [RFC6125]) One of the domain		reference identifier: (as defined in [RFC6125]) One of the domain
	names associated by the email (i.e., an SMTP, IMAP, POP3 or		names associated by the email (i.e., an SMTP, IMAP, POP3 or
	ManageSieve) client with the destination email server and		ManageSieve) client with the target email server and optionally an
	optionally an application service type for performing name checks		application service type for performing name checks on the server
	on the server certificate. When name checks are applicable, at		certificate. When name checks are applicable, at least one of the
	least one of the reference identifiers MUST match an [RFC6125]		reference identifiers MUST match an [RFC6125] DNS-ID or SRV-ID (or
	DNS-ID or SRV-ID (or if none are present the [RFC6125] CN-ID) of		if none are present the [RFC6125] CN-ID) of the server
	the server certificate.		certificate.
			CN-ID, DNS-ID, SRV-ID and URI-ID are identifier types (see [RFC6125]
			for details). For convenience, their short definitions from
			[RFC6125] are listed below:
			CN-ID = a Relative Distinguished Name (RDN) in the certificate
			subject field that contains one and only one attribute-type-and-
			value pair of type Common Name (CN), where the value matches the
			overall form of a domain name (informally, dot- separated letter-
			digit-hyphen labels).
			DNS-ID = a subjectAltName entry of type dNSName
			SRV-ID = a subjectAltName entry of type otherName whose name form
			is SRVName
			URI-ID = a subjectAltName entry of type uniformResourceIdentifier
			whose value includes both (i) a "scheme" and (ii) a "host"
			component (or its equivalent) that matches the "reg-name" rule
			(where the quoted terms represent the associated [RFC5234]
			productions from [RFC3986]).
	3. Email Server Certificate Verification Rules		3. Email Server Certificate Verification Rules
	During a TLS negotiation, an email client (i.e., an SMTP, IMAP, POP3		During a TLS negotiation, an email client (i.e., an SMTP, IMAP, POP3
	or ManageSieve client) MUST check its understanding of the server		or ManageSieve client) MUST check its understanding of the server
	hostname against the server's identity as presented in the server		hostname against the server's identity as presented in the server
	Certificate message, in order to prevent man-in-the-middle attacks.		Certificate message, in order to prevent man-in-the-middle attacks.
			This check is only performed after the server certificate passes
			certification path validation as described in Section 6 of [RFC5280].
	Matching is performed according to the rules specified in Section 6		Matching is performed according to the rules specified in Section 6
	of [RFC6125], including "certificate pinning" and the procedure on		of [RFC6125], including "certificate pinning" and the procedure on
	failure to match. The following inputs are used by the verification		failure to match. The following inputs are used by the verification
	procedure used in [RFC6125]:		procedure used in [RFC6125]:
	1. For DNS-ID and CN-ID identifier types the client MUST use one or		1. For DNS-ID and CN-ID identifier types the client MUST use one or
	more of the following as "reference identifiers": (a) the right		more of the following as "reference identifiers": (a) the domain
	hand side of the email address, (b) the hostname it used to open		portion of the user's email address, (b) the hostname it used to
	the connection (without CNAME canonicalization). The client MAY		open the connection (without CNAME canonicalization). The client
	also use (c) a value securely derived from (a) or (b), such as		MAY also use (c) a value securely derived from (a) or (b), such
	using "secure" DNSSEC validated lookup.		as using "secure" DNSSEC validated lookup.
	2. When using email service discovery procedure specified in		2. When using email service discovery procedure specified in
	[RFC6186] the client MUST also use the right hand side of the		[RFC6186] the client MUST also use the domain portion of the
	email address as another "reference identifier" to compare		user's email address as another "reference identifier" to compare
	against SRV-ID identifier in the server certificate.		against SRV-ID identifier in the server certificate.
	The rules and guidelines defined in [RFC6125] apply to an email		The rules and guidelines defined in [RFC6125] apply to an email
	server certificates, with the following supplemental rules:		server certificate, with the following supplemental rules:
	1. Support for the DNS-ID identifier type (subjectAltName of dNSName		1. Support for the DNS-ID identifier type (subjectAltName of dNSName
	type [RFC5280]) is REQUIRED in Email client software		type [RFC5280]) is REQUIRED in Email client software
	implementations.		implementations.
	2. Support for the SRV-ID identifier type (subjectAltName of SRVName		2. Support for the SRV-ID identifier type (subjectAltName of SRVName
	type [RFC4985]) is REQUIRED for email client software		type [RFC4985]) is REQUIRED for email client software
	implementations that support [RFC6186]. List of SRV-ID types for		implementations that support [RFC6186]. List of SRV-ID types for
	email services is specified in [RFC6186]. For the ManageSieve		email services is specified in [RFC6186]. For the ManageSieve
	protocol the service name "sieve" is used.		protocol the service name "sieve" is used.
	skipping to change at page 4, line 36		skipping to change at page 5, line 12
	as a fragment of the left-most name component (e.g.,		as a fragment of the left-most name component (e.g.,
	*oo.example.com, f*o.example.com, or foo*.example.com).		*oo.example.com, f*o.example.com, or foo*.example.com).
	4. Compliance Checklist for Certification Authorities		4. Compliance Checklist for Certification Authorities
	1. CA MUST support issuance of server certificates with DNS-ID		1. CA MUST support issuance of server certificates with DNS-ID
	identifier type (subjectAltName of dNSName type [RFC5280]).		identifier type (subjectAltName of dNSName type [RFC5280]).
	2. CA MUST support issuance of server certificates with SRV-ID		2. CA MUST support issuance of server certificates with SRV-ID
	identifier type (subjectAltName of SRVName type [RFC4985]) for		identifier type (subjectAltName of SRVName type [RFC4985]) for
	each type of email service.		each type of email service. See Section 4.1 for more discussion
			on what this means for Certification Authorities.
	3. For backward compatibility with deployed client base, CA MUST		3. For backward compatibility with deployed client base, CA MUST
	support issuance of server certificates with CN-ID identifier		support issuance of server certificates with CN-ID identifier
	type (CN attribute from the subject name, see [RFC6125]).		type (CN attribute from the subject name, see [RFC6125]).
	4. CA MAY allow "*" (wildcard) as the left-most name component of		4. CA MAY allow "*" (wildcard) as the left-most name component of
	DNS-ID or CN-ID in server certificates it issues.		DNS-ID or CN-ID in server certificates it issues.
			4.1. Notes on handling of SRV-ID by Certificate Authorities
			TBD. List some possible recommendations and limitations of different
			approaches.
	5. Compliance Checklist for Mail Service Providers and Certificate		5. Compliance Checklist for Mail Service Providers and Certificate
	Signing Request generation tools		Signing Request generation tools
	1. SHOULD include the DNS-ID identifier type (subjectAltName of		1. MUST include the DNS-ID identifier type in Certificate Signing
	dNSName type [RFC5280]) in Certificate Signing Requests for both		Requests for the host name(s) where the email server(s) are
	the right hand side of served email addresses, as well as for the		running. SHOULD include the DNS-ID identifier type in
	host name where the email server(s) are running.		Certificate Signing Requests for the domain portion of served
			email addresses.
	2. If the email services provided are discoverable using DNS SRV as		2. If the email services provided are discoverable using DNS SRV as
	specified in [RFC6186], the Mail Service Provider MUST include		specified in [RFC6186], the Mail Service Provider MUST include
	the SRV-ID identifier type (subjectAltName of SRVName type		the SRV-ID identifier type for each type of email service in
	[RFC4985]) for each type of email service in Certificate Signing		Certificate Signing Requests.
	Requests.
	3. SHOULD include CN-ID identifier type (CN attribute from the		3. SHOULD include CN-ID identifier type for the host name where the
	subject name, see [RFC6125]) for the host name where the email		email server(s) is running in Certificate Signing Requests for
	server(s) is running in Certificate Signing Requests for backward		backward compatibility with deployed email clients. (Note, a
	compatibility with deployed email clients. (Note, a certificate		certificate can only include a single CN-ID, so if a mail service
	can only include a single CN-ID, so if a mail service is running		is running on multiple hosts, either each host has to use
	on multiple hosts, either each host has to use different		different certificate with its own CN-ID, a single certificate
	certificate with its own CN-ID, a single certificate with		with multiple DNS-IDs, or a single certificate with wildcard in
	multiple DNS-IDs, or a single certificate with wildcard in CN-ID		CN-ID can be used).
	can be used).
	4. MAY include "*" (wildcard) as the left-most name component of		4. MAY include "*" (wildcard) as the left-most name component of
	DNS-ID or CN-ID in Certificate Signing Requests.		DNS-ID or CN-ID in Certificate Signing Requests.
			5.1. Notes on hosted domains
			TBD. Compare one certificate that contains all hosted domains versa
			use of SNI or separate IPs for each hosted domain with its own
			certificate.
	6. Examples		6. Examples
	Consider an IMAP-accessible email server which supports both IMAP and		Consider an IMAP-accessible email server which supports both IMAP and
	IMAPS (IMAP-over-TLS) at the host "mail.example.net" servicing email		IMAPS (IMAP-over-TLS) at the host "mail.example.net" servicing email
	addresses of the form "user@example.net". A certificate for this		addresses of the form "user@example.net". A certificate for this
	service needs to include DNS-IDs of "example.net" (because it is the		service needs to include DNS-IDs of "example.net" (because it is the
	right hand side of emails) and "mail.example.net" (this is what a		domain portion of emails) and "mail.example.net" (this is what a user
	user of this server enters manually, if not using [RFC6186]). It		of this server enters manually, if not using [RFC6186]). It might
	might also include CN-IDs of "mail.example.net" for backward		also include CN-ID of "mail.example.net" for backward compatibility
	compatibility with deployed infrastructure.		with deployed infrastructure.
	Consider the IMAP-accessible email server from the previous paragraph		Consider the IMAP-accessible email server from the previous paragraph
	which is additionally discoverable via DNS SRV lookups in domain		which is additionally discoverable via DNS SRV lookups in domain
	"example.net" (DNS SRV records "_imap._tcp.example.net" and		"example.net" (DNS SRV records "_imap._tcp.example.net" and
	"_imaps._tcp.example.net"). In addition to DNS-ID/CN-ID identity		"_imaps._tcp.example.net"). In addition to DNS-ID/CN-ID identity
	types specified above, a certificate for this service also needs to		types specified above, a certificate for this service also needs to
	include SRV-IDs of "_imap.example.net" (when STARTTLS is used on the		include SRV-IDs of "_imap.example.net" (when STARTTLS is used on the
	IMAP port) and "_imaps.example.net" (when TLS is used on IMAPS port).		IMAP port) and "_imaps.example.net" (when TLS is used on IMAPS port).
	See [RFC6186] for more details. (Note that unlike DNS SRV there is		See [RFC6186] for more details. (Note that unlike DNS SRV there is
	no "_tcp" component in SRV-IDs).		no "_tcp" component in SRV-IDs).
			Consider the IMAP-accessible email server from the first paragraph
			which is running on a host also known as "mycompany.example.com". In
			addition to DNS-ID identity types specified above, a certificate for
			this service also needs to include DNS-ID of "mycompany.example.com"
			(this is what a user of this server enters manually, if not using
			[RFC6186]). It might also include CN-ID of "mycompany.example.com"
			instead of the CN-ID "mail.example.net" for backward compatibility
			with deployed infrastructure. (This is so, because a certificate can
			only include a single CN-ID)
	Consider an SMTP Submission server at the host "submit.example.net"		Consider an SMTP Submission server at the host "submit.example.net"
	servicing email addresses of the form "user@example.net" and		servicing email addresses of the form "user@example.net" and
	discoverable via DNS SRV lookups in domain "example.net" (DNS SRV		discoverable via DNS SRV lookups in domain "example.net" (DNS SRV
	records "_submission._tcp.example.net"). A certificate for this		records "_submission._tcp.example.net"). A certificate for this
	service needs to include SRV-IDs of "_submission.example.net" (see		service needs to include SRV-IDs of "_submission.example.net" (see
	[RFC6186]) along with DNS-IDs of "example.net" and		[RFC6186]) along with DNS-IDs of "example.net" and
	"submit.example.net". It might also include CN-IDs of		"submit.example.net". It might also include CN-ID of
	"submit.example.net" for backward compatibility with deployed		"submit.example.net" for backward compatibility with deployed
	infrastructure.		infrastructure.
	Consider a host "mail.example.net" servicing email addresses of the		Consider a host "mail.example.net" servicing email addresses of the
	form "user@example.net" and discoverable via DNS SRV lookups in		form "user@example.net" and discoverable via DNS SRV lookups in
	domain "example.net", which runs SMTP Submission, IMAPS and POP3S		domain "example.net", which runs SMTP Submission, IMAPS and POP3S
	(POP3-over-TLS) and ManageSieve services. Each of the servers can		(POP3-over-TLS) and ManageSieve services. Each of the servers can
	use their own certificate specific to their service (see examples		use their own certificate specific to their service (see examples
	above). Alternatively they can all share a single certificate that		above). Alternatively they can all share a single certificate that
	would include SRV-IDs of "_submission.example.net",		would include SRV-IDs of "_submission.example.net",
	"_imaps.example.net", "_pop3s.example.net" and "_sieve.example.net"		"_imaps.example.net", "_pop3s.example.net" and "_sieve.example.net"
	along with DNS-IDs of "example.net" and "mail.example.net". It might		along with DNS-IDs of "example.net" and "mail.example.net". It might
	also include CN-IDs of "mail.example.net" for backward compatibility		also include CN-ID of "mail.example.net" for backward compatibility
	with deployed infrastructure.		with deployed infrastructure.
	7. IANA Considerations		7. IANA Considerations
	This document doesn't require any action from IANA.		This document doesn't require any action from IANA.
	8. Security Considerations		8. Security Considerations
	The goal of this document is to improve interoperability and thus		The goal of this document is to improve interoperability and thus
	security of email clients wishing to access email servers over TLS		security of email clients wishing to access email servers over TLS
	skipping to change at page 6, line 46		skipping to change at page 7, line 44
	if they are a target of a DNS SRV lookup) or derived using a secure		if they are a target of a DNS SRV lookup) or derived using a secure
	third party service (e.g. DNSSEC-protected SRV records which are		third party service (e.g. DNSSEC-protected SRV records which are
	verified by the client or trusted local resolver). Future work in		verified by the client or trusted local resolver). Future work in
	this area might benefit from integration with DANE [RFC6698], but it		this area might benefit from integration with DANE [RFC6698], but it
	is not covered by this document.		is not covered by this document.
	9. References		9. References
	9.1. Normative References		9.1. Normative References
			[RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
			STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,
			<http://www.rfc-editor.org/info/rfc1939>.
	[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,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC6409] Gellens, R. and J. Klensin, "Message Submission for Mail",
	STD 72, RFC 6409, DOI 10.17487/RFC6409, November 2011,
	<http://www.rfc-editor.org/info/rfc6409>.
	[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over		[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over
	Transport Layer Security", RFC 3207, DOI 10.17487/RFC3207,		Transport Layer Security", RFC 3207, DOI 10.17487/RFC3207,
	February 2002, <http://www.rfc-editor.org/info/rfc3207>.		February 2002, <http://www.rfc-editor.org/info/rfc3207>.
	[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION		[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
	4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,		4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
	<http://www.rfc-editor.org/info/rfc3501>.		<http://www.rfc-editor.org/info/rfc3501>.
	[RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",		[RFC4985] Santesson, S., "Internet X.509 Public Key Infrastructure
	STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,		Subject Alternative Name for Expression of Service Name",
	<http://www.rfc-editor.org/info/rfc1939>.		RFC 4985, DOI 10.17487/RFC4985, August 2007,
			<http://www.rfc-editor.org/info/rfc4985>.
	[RFC5804] Melnikov, A., Ed. and T. Martin, "A Protocol for Remotely		[RFC5804] Melnikov, A., Ed. and T. Martin, "A Protocol for Remotely
	Managing Sieve Scripts", RFC 5804, DOI 10.17487/RFC5804,		Managing Sieve Scripts", RFC 5804, DOI 10.17487/RFC5804,
	July 2010, <http://www.rfc-editor.org/info/rfc5804>.		July 2010, <http://www.rfc-editor.org/info/rfc5804>.
	[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
	Verification of Domain-Based Application Service Identity
	within Internet Public Key Infrastructure Using X.509
	(PKIX) Certificates in the Context of Transport Layer
	Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
	2011, <http://www.rfc-editor.org/info/rfc6125>.
	[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,		[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
	Housley, R., and W. Polk, "Internet X.509 Public Key		Housley, R., and W. Polk, "Internet X.509 Public Key
	Infrastructure Certificate and Certificate Revocation List		Infrastructure Certificate and Certificate Revocation List
	(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,		(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
	<http://www.rfc-editor.org/info/rfc5280>.		<http://www.rfc-editor.org/info/rfc5280>.
	[RFC4985] Santesson, S., "Internet X.509 Public Key Infrastructure		[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
	Subject Alternative Name for Expression of Service Name",		Verification of Domain-Based Application Service Identity
	RFC 4985, DOI 10.17487/RFC4985, August 2007,		within Internet Public Key Infrastructure Using X.509
	<http://www.rfc-editor.org/info/rfc4985>.		(PKIX) Certificates in the Context of Transport Layer
			Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
			2011, <http://www.rfc-editor.org/info/rfc6125>.
	[RFC6186] Daboo, C., "Use of SRV Records for Locating Email		[RFC6186] Daboo, C., "Use of SRV Records for Locating Email
	Submission/Access Services", RFC 6186,		Submission/Access Services", RFC 6186,
	DOI 10.17487/RFC6186, March 2011,		DOI 10.17487/RFC6186, March 2011,
	<http://www.rfc-editor.org/info/rfc6186>.		<http://www.rfc-editor.org/info/rfc6186>.
			[RFC6409] Gellens, R. and J. Klensin, "Message Submission for Mail",
			STD 72, RFC 6409, DOI 10.17487/RFC6409, November 2011,
			<http://www.rfc-editor.org/info/rfc6409>.
	9.2. Informative References		9.2. Informative References
	[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP",		[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP",
	RFC 2595, DOI 10.17487/RFC2595, June 1999,		RFC 2595, DOI 10.17487/RFC2595, June 1999,
	<http://www.rfc-editor.org/info/rfc2595>.		<http://www.rfc-editor.org/info/rfc2595>.
			[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
			Resource Identifier (URI): Generic Syntax", STD 66,
			RFC 3986, DOI 10.17487/RFC3986, January 2005,
			<http://www.rfc-editor.org/info/rfc3986>.
			[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
			Specifications: ABNF", STD 68, RFC 5234,
			DOI 10.17487/RFC5234, January 2008,
			<http://www.rfc-editor.org/info/rfc5234>.
	[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication		[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
	of Named Entities (DANE) Transport Layer Security (TLS)		of Named Entities (DANE) Transport Layer Security (TLS)
	Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August		Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
	2012, <http://www.rfc-editor.org/info/rfc6698>.		2012, <http://www.rfc-editor.org/info/rfc6698>.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	Thank you to Chris Newman, Viktor Dukhovni and Sean Turner for		Thank you to Chris Newman, Viktor Dukhovni, Sean Turner, Russ Housley
	comments on this document.		and Alessandro Vesely for comments on this document.
	The editor of this document copied lots of text from RFC 2595 and RFC		The editor of this document copied lots of text from RFC 2595 and RFC
	6125, so the hard work of editors of these document is appreciated.		6125, so the hard work of editors of these document is appreciated.
	Appendix B. Changes since draft-ietf-uta-email-tls-certs-00		Appendix B. Changes since draft-ietf-uta-email-tls-certs-00
	[[Note to RFC Editor: Please delete this section before publication]]		[[Note to RFC Editor: Please delete this section before publication]]
	Added another example, clarified that subjectAltName and DNS SRV are		Added another example, clarified that subjectAltName and DNS SRV are
	using slightly different syntax.		using slightly different syntax.
End of changes. 30 change blocks.
	77 lines changed or deleted		133 lines changed or added
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