draft-ietf-uta-email-tls-certs-00.txt		draft-ietf-uta-email-tls-certs-01.txt
	Network Working Group A. Melnikov		Network Working Group A. Melnikov
	Internet-Draft Isode Ltd		Internet-Draft Isode Ltd
	Updates: 2595, 3207 (if approved) September 11, 2014		Updates: 2595, 3207, 3501, 5804 (if March 5, 2015
			approved)
	Intended status: Standards Track		Intended status: Standards Track
	Expires: March 15, 2015		Expires: September 6, 2015
	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-00		draft-ietf-uta-email-tls-certs-01
	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.		Section 2.4 of RFC 2595.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	skipping to change at page 1, line 33		skipping to change at page 1, line 34
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at 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 15, 2015.		This Internet-Draft will expire on September 6, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2014 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
	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. Email Server Certificate Verification Rules . . . . . . . . . 2		3. Email Server Certificate Verification Rules . . . . . . . . . 3
	4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3		4. Compliance Checklist for Certificate Authorities . . . . . . 4
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		5. Compliance Checklist for Mail Service Providers and
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 4		Certificate Signing Request generation tools . . . . . . . . 4
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4		6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	7.1. Normative References . . . . . . . . . . . . . . . . . . 4		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	7.2. Informative References . . . . . . . . . . . . . . . . . 5		8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
			9.1. Normative References . . . . . . . . . . . . . . . . . . 6
			9.2. Informative References . . . . . . . . . . . . . . . . . 6
			Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 7
			Appendix B. Changes since draft-ietf-uta-email-tls-certs-00 . . 7
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
			Use of TLS by SMTP Submission, IMAP, POP and ManageSieve clients is
			described in [RFC3207], [RFC3501], [RFC2595] and [RFC5804]
			respectively. Each of the documents describes slightly different
			rules for server certificate identity verification (or doesn't define
			any rules at all). In reality, email client and server developers
			implement many of these protocols at the same time, so it would be
			good to define modern and consistent rules for verifying email server
			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 [RFC4409] [RFC3207], IMAP [RFC3501],		procedure for SMTP Submission [RFC4409] [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		The main goal of the document is to provide consistent TLS server
	identity verification procedure across multiple email related		identity verification procedure across multiple email related
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	expressed in the server certificate (the reference identity).		expressed in the server certificate (the reference identity).
	The client MUST NOT use any form of the server hostname derived		The client MUST NOT use any form of the server hostname derived
	from an insecure remote source (e.g., insecure DNS lookup).		from an insecure remote source (e.g., insecure DNS lookup).
	CNAME canonicalization is not done.		CNAME canonicalization is not done.
	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 certificates, 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. Certification authorities that issue Email-		implementations.
	specific certificates MUST support the DNS-ID identifier type.
	Service providers SHOULD include the DNS-ID identifier type in
	Certificate Signing Requests.
	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. Certification authorities that issue email-		implementations. List of SRV-ID types for email services is
	specific certificates MUST support the SRV-ID identifier type.		specified in [RFC6186]. For ManageSieve the value "sieve" is
	Service providers SHOULD include the SRV-ID identifier type in		used.
	Certificate Signing Requests. List of SRV-ID types for email
	services is specified in [RFC6186]. For ManageSieve the value
	"sieve" is used.
	3. URI-ID identifier type (subjectAltName of		3. URI-ID identifier type (subjectAltName of
	uniformResourceIdentifier type [RFC5280]) MUST NOT be used by		uniformResourceIdentifier type [RFC5280]) MUST NOT be used by
	clients for server verification.		clients for server verification, as
	4. For backward compatibility with deployed software CN-ID		4. For backward compatibility with deployed software CN-ID
	identifier type (CN attribute from the subject name, see		identifier type (CN attribute from the subject name, see
	[RFC6125]) MAY be used for server identity verification.		[RFC6125]) MAY be used for server identity verification.
	5. Email protocols allow use of certain wilcards in identifiers		5. Email protocols allow use of certain wilcards in identifiers
	presented by email servers. The "*" wildcard character MAY be		presented by email servers. The "*" wildcard character MAY be
	used as the left-most name component of DNS-ID or CN-ID in the		used as the left-most name component of DNS-ID or CN-ID in the
	certificate. For example, a DNS-ID of *.example.com would match		certificate. For example, a DNS-ID of *.example.com would match
	a.example.com, foo.example.com, etc. but would not match		a.example.com, foo.example.com, etc. but would not match
	example.com. Note that the wildcard character MUST NOT be used		example.com. Note that the wildcard character MUST NOT be used
	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. Examples		4. Compliance Checklist for Certificate Authorities
			1. CA MUST support issuance of server certificates with DNS-ID
			identifier type (subjectAltName of dNSName type [RFC5280]).
			2. CA MUST support issuance of server certificates with SRV-ID
			identifier type (subjectAltName of SRVName type [RFC4985]) for
			each type of email service.
			3. For backward compatibility with deployed client base, CA MUST
			support issuance of server certificates with CN-ID identifier
			type (CN attribute from the subject name, see [RFC6125]).
			4. CA MAY allow "*" (wildcard) as the left-most name component of
			DNS-ID or CN-ID in server certificates it issues.
			5. Compliance Checklist for Mail Service Providers and Certificate
			Signing Request generation tools
			1. SHOULD include the DNS-ID identifier type (subjectAltName of
			dNSName type [RFC5280]) in Certificate Signing Requests for both
			the right hand side of served email addresses, as well as for the
			host name where the email server(s) are running.
			2. If the email services provided are discoverable using DNS SRV as
			specified in [RFC6186], MSP MUST include the SRV-ID identifier
			type (subjectAltName of SRVName type [RFC4985]) for each type of
			email service in Certificate Signing Requests.
			3. SHOULD include CN-ID identifier type (CN attribute from the
			subject name, see [RFC6125]) for the host name where the email
			server(s) is running in Certificate Signing Requests for backward
			compatibility with deployed email clients. (Note, a certificate
			can only include a single CN-ID, so if a mail service is running
			on multiple hosts, either each host has to use different
			certificate with its own CN-ID, a single certificate with
			multiple DNS-IDs, or a single certificate with wildcard in CN-ID
			can be used).
			4. MAY include "*" (wildcard) as the left-most name component of
			DNS-ID or CN-ID in Certificate Signing Requests.
			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" and discoverable via DNS SRV		addresses of the form "user@example.net" and discoverable via DNS SRV
	lookups on the application service name of "example.net". A		lookups in domain "example.net" (DNS SRV records
			"_imap._tcp.example.net" and "_imaps._tcp.example.net"). A
	certificate for this service needs to include SRV-IDs of		certificate for this service needs to include SRV-IDs of
	"_imap.example.net" and "_imaps.example.net" (see [RFC6186]) along		"_imap.example.net" and "_imaps.example.net" (see [RFC6186]. Note
			that unlike DNS SRV there is no "_tcp" component in SRV-IDs) along
	with DNS-IDs of "example.net" and "mail.example.net". It might also		with DNS-IDs of "example.net" and "mail.example.net". It might also
	include CN-IDs of "example.net" and "mail.example.net" for backward		include CN-IDs of "mail.example.net" for backward compatibility with
	compatibility with deployed infrastructure.		deployed infrastructure.
	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 on the application service name of		discoverable via DNS SRV lookups in domain "example.net" (DNS SRV
	"example.net". A certificate for this service needs to include SRV-		records "_submission._tcp.example.net"). A certificate for this
	IDs of "_submission.example.net" (see [RFC6186]) along with DNS-IDs		service needs to include SRV-IDs of "_submission.example.net" (see
	of "example.net" and "submit.example.net". It might also include CN-		[RFC6186]) along with DNS-IDs of "example.net" and
	IDs of "example.net" and "submit.example.net" for backward		"submit.example.net". It might also include CN-IDs of
	compatibility with deployed infrastructure.		"submit.example.net" for backward compatibility with deployed
			infrastructure.
	5. IANA Considerations		Consider a host "mail.example.net" servicing email addresses of the
			form "user@example.net" and discoverable via DNS SRV lookups in
			domain "example.net", which runs SMTP Submission, IMAPS and POP3S
			(POP3-over-TLS) and ManageSieve services. Each of the servers can
			use their own certificate specific to their service (see examples
			above). Alternatively they can all share a single certificate that
			would include SRV-IDs of "_submission.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
			also include CN-IDs of "mail.example.net" for backward compatibility
			with deployed infrastructure.
			7. IANA Considerations
	This document doesn't require any action from IANA.		This document doesn't require any action from IANA.
	6. 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
	protected email protocols, by specifying a consistent set of rules		protected email protocols, by specifying a consistent set of rules
	that email service providers, email client writers and certificate		that email service providers, email client writers and certificate
	authorities can use when creating server certificates.		authorities can use when creating server certificates.
	7. References		9. References
			9.1. Normative References
	7.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,		[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
	October 2008.		October 2008.
	[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",		[RFC4409] Gellens, R. and J. Klensin, "Message Submission for Mail",
	RFC 4409, April 2006.		RFC 4409, April 2006.
	skipping to change at page 5, line 23		skipping to change at page 6, line 42
	[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, May 2008.		(CRL) Profile", RFC 5280, May 2008.
	[RFC4985] Santesson, S., "Internet X.509 Public Key Infrastructure		[RFC4985] Santesson, S., "Internet X.509 Public Key Infrastructure
	Subject Alternative Name for Expression of Service Name",		Subject Alternative Name for Expression of Service Name",
	RFC 4985, August 2007.		RFC 4985, August 2007.
	7.2. Informative References		9.2. Informative References
	[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC		[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
	2595, June 1999.		2595, June 1999.
	[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, March 2011.		Submission/Access Services", RFC 6186, March 2011.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	Thank you to Chris Newman for comments on this document.		Thank you to Chris Newman 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
			[[Note to RFC Editor: Please delete this section before publication]]
			Added another example, clarified that subjectAltName and DNS SRV are
			using slightly different syntax.
			As any certificate can only include one CN-ID, corrected examples.
			Split rules to talk seperately about requirements on MUAs, CAs and
			MSPs/CSR generation tools.
			Updated Introduction section.
	Author's Address		Author's Address
	Alexey Melnikov		Alexey Melnikov
	Isode Ltd		Isode Ltd
	14 Castle Mews		14 Castle Mews
	Hampton, Middlesex TW12 2NP		Hampton, Middlesex TW12 2NP
	UK		UK
	EMail: Alexey.Melnikov@isode.com		EMail: Alexey.Melnikov@isode.com
End of changes. 20 change blocks.
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