idnits 2.17.1
draft-ietf-uta-xmpp-02.txt:
Checking boilerplate required by RFC 5378 and the IETF Trust (see
https://trustee.ietf.org/license-info):
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt:
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/checklist :
----------------------------------------------------------------------------
No issues found here.
Miscellaneous warnings:
----------------------------------------------------------------------------
== The copyright year in the IETF Trust and authors Copyright Line does not
match the current year
-- The document date (September 22, 2014) is 3501 days in the past. Is
this intentional?
Checking references for intended status: Proposed Standard
----------------------------------------------------------------------------
(See RFCs 3967 and 4897 for information about using normative references
to lower-maturity documents in RFCs)
== Outdated reference: A later version (-11) exists of
draft-ietf-uta-tls-bcp-03
** Downref: Normative reference to an Informational RFC: RFC 4949
** Obsolete normative reference: RFC 5077 (Obsoleted by RFC 8446)
** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446)
** Obsolete normative reference: RFC 6125 (Obsoleted by RFC 9525)
== Outdated reference: A later version (-11) exists of
draft-ietf-xmpp-dna-06
-- Obsolete informational reference (is this intentional?): RFC 3920
(Obsoleted by RFC 6120)
Summary: 4 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--).
Run idnits with the --verbose option for more detailed information about
the items above.
--------------------------------------------------------------------------------
2 Network Working Group P. Saint-Andre
3 Internet-Draft &yet
4 Updates: 6120 (if approved) T. Alkemade
5 Intended status: Standards Track
6 Expires: March 26, 2015 September 22, 2014
8 Use of Transport Layer Security (TLS) in the Extensible Messaging and
9 Presence Protocol (XMPP)
10 draft-ietf-uta-xmpp-02
12 Abstract
14 This document provides recommendations for the use of Transport Layer
15 Security (TLS) in the Extensible Messaging and Presence Protocol
16 (XMPP). This document updates RFC 6120.
18 Status of This Memo
20 This Internet-Draft is submitted in full conformance with the
21 provisions of BCP 78 and BCP 79.
23 Internet-Drafts are working documents of the Internet Engineering
24 Task Force (IETF). Note that other groups may also distribute
25 working documents as Internet-Drafts. The list of current Internet-
26 Drafts is at http://datatracker.ietf.org/drafts/current/.
28 Internet-Drafts are draft documents valid for a maximum of six months
29 and may be updated, replaced, or obsoleted by other documents at any
30 time. It is inappropriate to use Internet-Drafts as reference
31 material or to cite them other than as "work in progress."
33 This Internet-Draft will expire on March 26, 2015.
35 Copyright Notice
37 Copyright (c) 2014 IETF Trust and the persons identified as the
38 document authors. All rights reserved.
40 This document is subject to BCP 78 and the IETF Trust's Legal
41 Provisions Relating to IETF Documents
42 (http://trustee.ietf.org/license-info) in effect on the date of
43 publication of this document. Please review these documents
44 carefully, as they describe your rights and restrictions with respect
45 to this document. Code Components extracted from this document must
46 include Simplified BSD License text as described in Section 4.e of
47 the Trust Legal Provisions and are provided without warranty as
48 described in the Simplified BSD License.
50 Table of Contents
52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
53 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
54 3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 3
55 3.1. Support for TLS . . . . . . . . . . . . . . . . . . . . . 3
56 3.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 3
57 3.3. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 3
58 3.4. Public Key Length . . . . . . . . . . . . . . . . . . . . 3
59 3.5. Compression . . . . . . . . . . . . . . . . . . . . . . . 3
60 3.6. Session Resumption . . . . . . . . . . . . . . . . . . . 4
61 3.7. Authenticated Connections . . . . . . . . . . . . . . . . 4
62 3.8. Unauthenticated Connections . . . . . . . . . . . . . . . 4
63 3.9. Server Name Indication . . . . . . . . . . . . . . . . . 4
64 3.10. Human Factors . . . . . . . . . . . . . . . . . . . . . . 5
65 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
66 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
67 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
68 6.1. Normative References . . . . . . . . . . . . . . . . . . 6
69 6.2. Informative References . . . . . . . . . . . . . . . . . 6
70 Appendix A. Implementation Notes . . . . . . . . . . . . . . . . 7
71 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 7
72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
74 1. Introduction
76 The Extensible Messaging and Presence Protocol (XMPP) [RFC6120]
77 (along with its precursor, the so-called "Jabber protocol") has used
78 Transport Layer Security (TLS) [RFC5246] (along with its precursor,
79 Secure Sockets Layer or SSL) since 1999. Both [RFC6120] and its
80 predecessor [RFC3920] provided recommendations regarding the use of
81 TLS in XMPP. In order to address the evolving threat model on the
82 Internet today, this document provides stronger recommendations based
83 on [I-D.ietf-uta-tls-bcp]. This document updates [RFC6120].
85 2. Terminology
87 Various security-related terms are to be understood in the sense
88 defined in [RFC4949].
90 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
91 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
92 "OPTIONAL" in this document are to be interpreted as described in
93 [RFC2119].
95 3. Recommendations
97 3.1. Support for TLS
99 Support for TLS (specifically, the XMPP profile of STARTTLS) is
100 mandatory for XMPP implementations, as already specified in [RFC6120]
101 and its predecessor [RFC3920].
103 If the server to which a client or peer server connects does not
104 offer a stream feature of (thus indicating that it is an XMPP 1.0 server that
106 supports TLS), the initiating entity MUST NOT proceed with the stream
107 negotiation and MUST instead abort the connection attempt. Although
108 XMPP servers SHOULD include the child element to indicate
109 that negotiation of TLS is mandatory, clients and peer servers MUST
110 NOT depend on receiving the flag in determining whether
111 TLS will be enforced for the stream.
113 3.2. Protocol Versions
115 Implementations MUST follow the recommendations in Section 4.1 of
116 [I-D.ietf-uta-tls-bcp] as to supporting various TLS versions and
117 avoiding fallback to SSL.
119 3.3. Cipher Suites
121 Implementations MUST follow the recommendations in Section 5 of
122 [I-D.ietf-uta-tls-bcp].
124 3.4. Public Key Length
126 Implementations MUST follow the recommendations in Section 5.4 of
127 [I-D.ietf-uta-tls-bcp].
129 3.5. Compression
131 Implementations MUST follow the recommendations in Section 4.5 of
132 [I-D.ietf-uta-tls-bcp].
134 XMPP supports an application-layer compression technology [XEP-0138],
135 which might have slightly stronger security properties than TLS (at
136 least because it is enabled after SASL authentication, as described
137 in [XEP-0170]).
139 3.6. Session Resumption
141 Implementations MUST follow the recommendations in Section 4.6 of
142 [I-D.ietf-uta-tls-bcp].
144 Use of session IDs [RFC5246] is RECOMMENDED instead of session
145 tickets [RFC5077], since XMPP does not in general use state
146 management technologies such as tickets or "cookies" [RFC6265].
148 In XMPP, TLS session resumption can be used in concert with the XMPP
149 Stream Management extension; see [XEP-0198] for further details.
151 3.7. Authenticated Connections
153 Both the core XMPP specification [RFC6120] and the "CertID"
154 specification [RFC6125] provide recommendations and requirements for
155 certificate validation in the context of authenticated connections.
156 This document does not supersede those specifications. Wherever
157 possible, it is best to prefer authenticated connections (along with
158 SASL [RFC4422]), as already stated in the core XMPP specification
159 [RFC6120]. In particular, clients MUST authenticate servers.
161 3.8. Unauthenticated Connections
163 Given the pervasiveness of passive eavesdropping, even an
164 unauthenticated connection might be better than an unencrypted
165 connection (this is similar to the "better than nothing security"
166 approach for IPsec [RFC5386]). In particular, because of current
167 deployment challenges for authenticated connections between XMPP
168 servers (see [I-D.ietf-xmpp-dna] for details), it might be reasonable
169 for XMPP server implementations to accept unauthenticated connections
170 when the Server Dialback protocol [XEP-0220] is used for weak
171 identity verification; this will at least enable encryption of
172 server-to-server connections. Unauthenticated connections include
173 connections negotiated using anonymous Diffie-Hellman algorithms or
174 using self-signed certificates, among other scenarios.
176 3.9. Server Name Indication
178 Although there is no harm in supporting the TLS Server Name
179 Indication (SNI) extension [RFC6066], this is not necessary since the
180 same function is served in XMPP by the 'to' address of the initial
181 stream header as explained in Section 4.7.2 of [RFC6120].
183 3.10. Human Factors
185 It is strongly encouraged that XMPP clients provide ways for end
186 users (and that XMPP servers provide ways for administrators) to
187 complete the following tasks:
189 o Determine if a client-to-server or server-to-server connection is
190 encrypted and authenticated.
192 o Determine the version of TLS used for a client-to-server or
193 server-to-server connection.
195 o Inspect the certificate offered by an XMPP server.
197 o Determine the cipher suite used to encrypt a connection.
199 o Be warned if the certificate changes for a given server.
201 4. IANA Considerations
203 This document requests no actions of the IANA.
205 5. Security Considerations
207 The use of TLS can help limit the information available for
208 correlation to the network and transport layer headers as opposed to
209 the application layer. As typically deployed, XMPP technologies do
210 not leave application-layer routing data (such as XMPP 'to' and
211 'from' addresses) at rest on intermediate systems, since there is
212 only one hop between any two given XMPP servers. As a result,
213 encrypting all hops (sending client to sender's server, sender's
214 server to recipient's server, recipient's server to recipient's
215 client) can help to limit the amount of "metadata" that might leak.
217 It is possible that XMPP servers themselves might be compromised. In
218 that case, per-hop encryption would not protect XMPP communications,
219 and even end-to-end encryption of (parts of) XMPP stanza payloads
220 would leave addressing information and XMPP roster data in the clear.
221 By the same token, it is possible that XMPP clients (or the end-user
222 devices on which such clients are installed) could also be
223 compromised, leaving users utterly at the mercy of an adversary.
225 This document and related actions to strengthen the security of the
226 XMPP network are based on the assumption that XMPP servers and
227 clients have not been subject to widespread compromise. If this
228 assumption is valid, then ubiquitous use of per-hop TLS channel
229 encryption and more significant deployment of end-to-end object
230 encryption technologies will serve to protect XMPP communications to
231 a measurable degree, compared to the alternatives.
233 6. References
235 6.1. Normative References
237 [I-D.ietf-uta-tls-bcp]
238 Sheffer, Y., Holz, R., and P. Saint-Andre,
239 "Recommendations for Secure Use of TLS and DTLS", draft-
240 ietf-uta-tls-bcp-03 (work in progress), September 2014.
242 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
243 Requirement Levels", BCP 14, RFC 2119, March 1997.
245 [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
246 4949, August 2007.
248 [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
249 "Transport Layer Security (TLS) Session Resumption without
250 Server-Side State", RFC 5077, January 2008.
252 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
253 (TLS) Protocol Version 1.2", RFC 5246, August 2008.
255 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
256 Protocol (XMPP): Core", RFC 6120, March 2011.
258 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
259 Verification of Domain-Based Application Service Identity
260 within Internet Public Key Infrastructure Using X.509
261 (PKIX) Certificates in the Context of Transport Layer
262 Security (TLS)", RFC 6125, March 2011.
264 6.2. Informative References
266 [I-D.ietf-xmpp-dna]
267 Saint-Andre, P. and M. Miller, "Domain Name Associations
268 (DNA) in the Extensible Messaging and Presence Protocol
269 (XMPP)", draft-ietf-xmpp-dna-06 (work in progress), June
270 2014.
272 [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
273 Protocol (XMPP): Core", RFC 3920, October 2004.
275 [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
276 Security Layer (SASL)", RFC 4422, June 2006.
278 [RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing
279 Security: An Unauthenticated Mode of IPsec", RFC 5386,
280 November 2008.
282 [RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
283 Extension Definitions", RFC 6066, January 2011.
285 [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
286 April 2011.
288 [XEP-0138]
289 Hildebrand, J. and P. Saint-Andre, "Stream Compression",
290 XSF XEP 0138, May 2009.
292 [XEP-0170]
293 Saint-Andre, P., "Recommended Order of Stream Feature
294 Negotiation", XSF XEP 0170, January 2007.
296 [XEP-0198]
297 Karneges, J., Saint-Andre, P., Hildebrand, J., Forno, F.,
298 Cridland, D., and M. Wild, "Stream Management", XSF XEP
299 0198, June 2011.
301 [XEP-0220]
302 Miller, J., Saint-Andre, P., and P. Hancke, "Server
303 Dialback", XSF XEP 0220, September 2013.
305 Appendix A. Implementation Notes
307 Some governments enforce legislation prohibiting the export of strong
308 cryptographic technologies. Nothing in this document ought to be
309 taken as advice to violate such prohibitions.
311 Appendix B. Acknowledgements
313 Thanks to the following individuals for their input: Dave Cridland,
314 Philipp Hancke, Olle Johansson, Steve Kille, Tobias Markmann, Matt
315 Miller, and Rene Treffer.
317 Authors' Addresses
319 Peter Saint-Andre
320 &yet
321 P.O. Box 787
322 Parker, CO 80134
323 USA
325 Email: peter@andyet.net
326 Thijs Alkemade
328 Email: me@thijsalkema.de