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
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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
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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.
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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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