< draft-ietf-uta-xmpp-02.txt		draft-ietf-uta-xmpp-03.txt >
	Network Working Group P. Saint-Andre		Network Working Group P. Saint-Andre
	Internet-Draft &yet		Internet-Draft &yet
	Updates: 6120 (if approved) T. Alkemade		Updates: 6120 (if approved) T. Alkemade
	Intended status: Standards Track		Intended status: Standards Track
	Expires: March 26, 2015 September 22, 2014		Expires: May 15, 2015 November 11, 2014
	Use of Transport Layer Security (TLS) in the Extensible Messaging and		Use of Transport Layer Security (TLS) in the Extensible Messaging and
	Presence Protocol (XMPP)		Presence Protocol (XMPP)
	draft-ietf-uta-xmpp-02		draft-ietf-uta-xmpp-03
	Abstract		Abstract
	This document provides recommendations for the use of Transport Layer		This document provides recommendations for the use of Transport Layer
	Security (TLS) in the Extensible Messaging and Presence Protocol		Security (TLS) in the Extensible Messaging and Presence Protocol
	(XMPP). This document updates RFC 6120.		(XMPP). This document updates RFC 6120.
	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 34 ¶		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 26, 2015.		This Internet-Draft will expire on May 15, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2014 IETF Trust and the persons identified as the		Copyright (c) 2014 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 11 ¶		skipping to change at page 2, line 11 ¶
	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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3		3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3
	3.1. Support for TLS . . . . . . . . . . . . . . . . . . . . . 3		3.1. Support for TLS . . . . . . . . . . . . . . . . . . . . . 3
	3.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 3		3.2. Compression . . . . . . . . . . . . . . . . . . . . . . . 3
	3.3. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 3		3.3. Session Resumption . . . . . . . . . . . . . . . . . . . 3
	3.4. Public Key Length . . . . . . . . . . . . . . . . . . . . 3		3.4. Authenticated Connections . . . . . . . . . . . . . . . . 3
	3.5. Compression . . . . . . . . . . . . . . . . . . . . . . . 3		3.5. Unauthenticated Connections . . . . . . . . . . . . . . . 4
	3.6. Session Resumption . . . . . . . . . . . . . . . . . . . 4		3.6. Server Name Indication . . . . . . . . . . . . . . . . . 4
	3.7. Authenticated Connections . . . . . . . . . . . . . . . . 4		3.7. Human Factors . . . . . . . . . . . . . . . . . . . . . . 4
	3.8. Unauthenticated Connections . . . . . . . . . . . . . . . 4		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	3.9. Server Name Indication . . . . . . . . . . . . . . . . . 4
	3.10. Human Factors . . . . . . . . . . . . . . . . . . . . . . 5
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 5		5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	6.1. Normative References . . . . . . . . . . . . . . . . . . 6		6.1. Normative References . . . . . . . . . . . . . . . . . . 5
	6.2. Informative References . . . . . . . . . . . . . . . . . 6		6.2. Informative References . . . . . . . . . . . . . . . . . 6
	Appendix A. Implementation Notes . . . . . . . . . . . . . . . . 7		Appendix A. Implementation Notes . . . . . . . . . . . . . . . . 7
	Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 7		Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 7
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	The Extensible Messaging and Presence Protocol (XMPP) [RFC6120]		The Extensible Messaging and Presence Protocol (XMPP) [RFC6120]
	(along with its precursor, the so-called "Jabber protocol") has used		(along with its precursor, the so-called "Jabber protocol") has used
	Transport Layer Security (TLS) [RFC5246] (along with its precursor,		Transport Layer Security (TLS) [RFC5246] (along with its precursor,
	Secure Sockets Layer or SSL) since 1999. Both [RFC6120] and its		Secure Sockets Layer or SSL) since 1999. Both [RFC6120] and its
	predecessor [RFC3920] provided recommendations regarding the use of		predecessor [RFC3920] provided recommendations regarding the use of
	TLS in XMPP. In order to address the evolving threat model on the		TLS in XMPP. In order to address the evolving threat model on the
	Internet today, this document provides stronger recommendations based		Internet today, this document provides stronger recommendations.
	on [I-D.ietf-uta-tls-bcp]. This document updates [RFC6120].
			NOTE: Unless explicitly noted otherwise, all of the
			recommendations specified in [I-D.ietf-uta-tls-bcp] apply to XMPP.
			In the main, this document merely provides supplementary
			information; those who implement and deploy XMPP technologies are
			expected to follow the recommendations of [I-D.ietf-uta-tls-bcp].
			This document updates [RFC6120].
	2. Terminology		2. Terminology
	Various security-related terms are to be understood in the sense		Various security-related terms are to be understood in the sense
	defined in [RFC4949].		defined in [RFC4949].
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	[RFC2119].		[RFC2119].
	3. Recommendations		3. Recommendations
	3.1. Support for TLS		3.1. Support for TLS
	Support for TLS (specifically, the XMPP profile of STARTTLS) is		Support for TLS (specifically, the XMPP profile of STARTTLS) is
	mandatory for XMPP implementations, as already specified in [RFC6120]		mandatory for XMPP implementations, as already specified in [RFC6120]
	and its predecessor [RFC3920].		and its predecessor [RFC3920].
	If the server to which a client or peer server connects does not		The server (i.e., the XMPP receiving entity) to which a client or
			peer server (i.e., the XMPP initiating entity) connects might not
	offer a stream feature of <starttls xmlns='urn:ietf:params:xml:ns		offer a stream feature of <starttls xmlns='urn:ietf:params:xml:ns
	:xmpp-tls'/> (thus indicating that it is an XMPP 1.0 server that		:xmpp-tls'/>. Although in general this stream feature indicates that
	supports TLS), the initiating entity MUST NOT proceed with the stream		the server supports XMPP 1.0 and therefore supports TLS, it is
	negotiation and MUST instead abort the connection attempt. Although		possible that this stream feature might be stripped out by an
	XMPP servers SHOULD include the <required/> child element to indicate		attacker (see Section 2.1 of [I-D.ietf-uta-tls-attacks]). Therefore,
	that negotiation of TLS is mandatory, clients and peer servers MUST		the initiating entity SHOULD proceed with the stream negotiation even
	NOT depend on receiving the <required/> flag in determining whether		if the receiving entity does not advertise support for TLS.
	TLS will be enforced for the stream.		Similarly, although a receiving entity SHOULD include the <required/>
			child element to indicate that negotiation of TLS is mandatory, an
	3.2. Protocol Versions		initiating entity MUST NOT depend on receiving the <required/> flag
			in determining whether TLS will be enforced for the stream.
	Implementations MUST follow the recommendations in Section 4.1 of
	[I-D.ietf-uta-tls-bcp] as to supporting various TLS versions and
	avoiding fallback to SSL.
	3.3. Cipher Suites
	Implementations MUST follow the recommendations in Section 5 of
	[I-D.ietf-uta-tls-bcp].
	3.4. Public Key Length
	Implementations MUST follow the recommendations in Section 5.4 of
	[I-D.ietf-uta-tls-bcp].
	3.5. Compression
	Implementations MUST follow the recommendations in Section 4.5 of
	[I-D.ietf-uta-tls-bcp].
	XMPP supports an application-layer compression technology [XEP-0138],		3.2. Compression
	which might have slightly stronger security properties than TLS (at
	least because it is enabled after SASL authentication, as described
	in [XEP-0170]).
	3.6. Session Resumption		XMPP supports an application-layer compression technology [XEP-0138].
			Although this XMPP extension might have slightly stronger security
			properties than TLS-layer compression (since it is enabled after SASL
			authentication, as described in [XEP-0170]), this document neither
			encourages nor discourages use of XMPP-layer compression.
	Implementations MUST follow the recommendations in Section 4.6 of		3.3. Session Resumption
	[I-D.ietf-uta-tls-bcp].
	Use of session IDs [RFC5246] is RECOMMENDED instead of session		Use of session IDs [RFC5246] is RECOMMENDED instead of session
	tickets [RFC5077], since XMPP does not in general use state		tickets [RFC5077], since XMPP does not in general use state
	management technologies such as tickets or "cookies" [RFC6265].		management technologies such as tickets or "cookies" [RFC6265].
	In XMPP, TLS session resumption can be used in concert with the XMPP		In XMPP, TLS session resumption can be used in concert with the XMPP
	Stream Management extension; see [XEP-0198] for further details.		Stream Management extension; see [XEP-0198] for further details.
	3.7. Authenticated Connections		3.4. Authenticated Connections
	Both the core XMPP specification [RFC6120] and the "CertID"		Both the core XMPP specification [RFC6120] and the "CertID"
	specification [RFC6125] provide recommendations and requirements for		specification [RFC6125] provide recommendations and requirements for
	certificate validation in the context of authenticated connections.		certificate validation in the context of authenticated connections.
	This document does not supersede those specifications. Wherever		This document does not supersede those specifications. Wherever
	possible, it is best to prefer authenticated connections (along with		possible, it is best to prefer authenticated connections (along with
	SASL [RFC4422]), as already stated in the core XMPP specification		SASL [RFC4422]), as already stated in the core XMPP specification
	[RFC6120]. In particular, clients MUST authenticate servers.		[RFC6120]. In particular, clients MUST authenticate servers.
	3.8. Unauthenticated Connections		3.5. Unauthenticated Connections
	Given the pervasiveness of passive eavesdropping, even an		Given the pervasiveness of passive eavesdropping, even an
	unauthenticated connection might be better than an unencrypted		unauthenticated connection might be better than an unencrypted
	connection (this is similar to the "better than nothing security"		connection (this is similar to the "better than nothing security"
	approach for IPsec [RFC5386]). In particular, because of current		approach for IPsec [RFC5386]). In particular, because of current
	deployment challenges for authenticated connections between XMPP		deployment challenges for authenticated connections between XMPP
	servers (see [I-D.ietf-xmpp-dna] for details), it might be reasonable		servers (see [I-D.ietf-xmpp-dna] and [I-D.ietf-xmpp-posh] for
	for XMPP server implementations to accept unauthenticated connections		details), it might be reasonable for XMPP server implementations to
	when the Server Dialback protocol [XEP-0220] is used for weak		accept unauthenticated connections when the Server Dialback protocol
	identity verification; this will at least enable encryption of		[XEP-0220] is used for weak identity verification; this will at least
	server-to-server connections. Unauthenticated connections include		enable encryption of server-to-server connections. Unauthenticated
	connections negotiated using anonymous Diffie-Hellman algorithms or		connections include connections negotiated using anonymous Diffie-
	using self-signed certificates, among other scenarios.		Hellman algorithms or using self-signed certificates, among other
			scenarios.
	3.9. Server Name Indication		3.6. Server Name Indication
	Although there is no harm in supporting the TLS Server Name		Although there is no harm in supporting the TLS Server Name
	Indication (SNI) extension [RFC6066], this is not necessary since the		Indication (SNI) extension [RFC6066], this is not necessary since the
	same function is served in XMPP by the 'to' address of the initial		same function is served in XMPP by the 'to' address of the initial
	stream header as explained in Section 4.7.2 of [RFC6120].		stream header as explained in Section 4.7.2 of [RFC6120].
	3.10. Human Factors		3.7. Human Factors
	It is strongly encouraged that XMPP clients provide ways for end		It is strongly encouraged that XMPP clients provide ways for end
	users (and that XMPP servers provide ways for administrators) to		users (and that XMPP servers provide ways for administrators) to
	complete the following tasks:		complete the following tasks:
	o Determine if a client-to-server or server-to-server connection is		o Determine if a client-to-server or server-to-server connection is
	encrypted and authenticated.		encrypted and authenticated.
	o Determine the version of TLS used for a client-to-server or		o Determine the version of TLS used for a client-to-server or
	server-to-server connection.		server-to-server connection.
	skipping to change at page 6, line 14 ¶		skipping to change at page 5, line 40 ¶
	encryption technologies will serve to protect XMPP communications to		encryption technologies will serve to protect XMPP communications to
	a measurable degree, compared to the alternatives.		a measurable degree, compared to the alternatives.
	6. References		6. References
	6.1. Normative References		6.1. Normative References
	[I-D.ietf-uta-tls-bcp]		[I-D.ietf-uta-tls-bcp]
	Sheffer, Y., Holz, R., and P. Saint-Andre,		Sheffer, Y., Holz, R., and P. Saint-Andre,
	"Recommendations for Secure Use of TLS and DTLS", draft-		"Recommendations for Secure Use of TLS and DTLS", draft-
	ietf-uta-tls-bcp-03 (work in progress), September 2014.		ietf-uta-tls-bcp-07 (work in progress), November 2014.
	[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.
	[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC		[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
	4949, August 2007.		4949, August 2007.
	[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,		[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
	"Transport Layer Security (TLS) Session Resumption without		"Transport Layer Security (TLS) Session Resumption without
	Server-Side State", RFC 5077, January 2008.		Server-Side State", RFC 5077, January 2008.
	skipping to change at page 6, line 40 ¶		skipping to change at page 6, line 19 ¶
	Protocol (XMPP): Core", RFC 6120, March 2011.		Protocol (XMPP): Core", RFC 6120, March 2011.
	[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and		[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
	Verification of Domain-Based Application Service Identity		Verification of Domain-Based Application Service Identity
	within Internet Public Key Infrastructure Using X.509		within Internet Public Key Infrastructure Using X.509
	(PKIX) Certificates in the Context of Transport Layer		(PKIX) Certificates in the Context of Transport Layer
	Security (TLS)", RFC 6125, March 2011.		Security (TLS)", RFC 6125, March 2011.
	6.2. Informative References		6.2. Informative References
			[I-D.ietf-uta-tls-attacks]
			Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
			Current Attacks on TLS and DTLS", draft-ietf-uta-tls-
			attacks-05 (work in progress), October 2014.
	[I-D.ietf-xmpp-dna]		[I-D.ietf-xmpp-dna]
	Saint-Andre, P. and M. Miller, "Domain Name Associations		Saint-Andre, P. and M. Miller, "Domain Name Associations
	(DNA) in the Extensible Messaging and Presence Protocol		(DNA) in the Extensible Messaging and Presence Protocol
	(XMPP)", draft-ietf-xmpp-dna-06 (work in progress), June		(XMPP)", draft-ietf-xmpp-dna-08 (work in progress),
	2014.		October 2014.
			[I-D.ietf-xmpp-posh]
			Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP
			(POSH)", draft-ietf-xmpp-posh-02 (work in progress),
			October 2014.
	[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence		[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
	Protocol (XMPP): Core", RFC 3920, October 2004.		Protocol (XMPP): Core", RFC 3920, October 2004.
	[RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and		[RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
	Security Layer (SASL)", RFC 4422, June 2006.		Security Layer (SASL)", RFC 4422, June 2006.
	[RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing		[RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing
	Security: An Unauthenticated Mode of IPsec", RFC 5386,		Security: An Unauthenticated Mode of IPsec", RFC 5386,
	November 2008.		November 2008.
	skipping to change at page 7, line 40 ¶		skipping to change at page 7, line 30 ¶
	Dialback", XSF XEP 0220, September 2013.		Dialback", XSF XEP 0220, September 2013.
	Appendix A. Implementation Notes		Appendix A. Implementation Notes
	Some governments enforce legislation prohibiting the export of strong		Some governments enforce legislation prohibiting the export of strong
	cryptographic technologies. Nothing in this document ought to be		cryptographic technologies. Nothing in this document ought to be
	taken as advice to violate such prohibitions.		taken as advice to violate such prohibitions.
	Appendix B. Acknowledgements		Appendix B. Acknowledgements
	Thanks to the following individuals for their input: Dave Cridland,		The authors would like to thank the following individuals for their
	Philipp Hancke, Olle Johansson, Steve Kille, Tobias Markmann, Matt		input: Dave Cridland, Philipp Hancke, Olle Johansson, Steve Kille,
	Miller, and Rene Treffer.		Tobias Markmann, Matt Miller, and Rene Treffer.
	Authors' Addresses		Authors' Addresses
	Peter Saint-Andre		Peter Saint-Andre
	&yet		&yet
	P.O. Box 787
	Parker, CO 80134
	USA
	Email: peter@andyet.net		Email: peter@andyet.com
			URI: https://andyet.com/
	Thijs Alkemade		Thijs Alkemade
	Email: me@thijsalkema.de		Email: me@thijsalkema.de
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