draft-ietf-xmpp-address-04.txt   draft-ietf-xmpp-address-05.txt 
Network Working Group P. Saint-Andre Network Working Group P. Saint-Andre
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track September 24, 2010 Intended status: Standards Track October 6, 2010
Expires: March 28, 2011 Expires: April 9, 2011
Extensible Messaging and Presence Protocol (XMPP): Address Format Extensible Messaging and Presence Protocol (XMPP): Address Format
draft-ietf-xmpp-address-04 draft-ietf-xmpp-address-05
Abstract Abstract
This document defines the format for addresses used in the Extensible This document defines the format for addresses used in the Extensible
Messaging and Presence Protocol (XMPP), including support for non- Messaging and Presence Protocol (XMPP), including support for non-
ASCII characters. ASCII characters.
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
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This Internet-Draft will expire on March 28, 2011. This Internet-Draft will expire on April 9, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 7
3. Internationalization Considerations . . . . . . . . . . . . . 8 3. Internationalization Considerations . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
4.1. Reuse of Stringprep . . . . . . . . . . . . . . . . . . . 8 4.1. Reuse of Stringprep . . . . . . . . . . . . . . . . . . . 8
4.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 8 4.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 8
4.3. Confusable Characters . . . . . . . . . . . . . . . . . . 8 4.3. Confusable Characters . . . . . . . . . . . . . . . . . . 8
4.4. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9 4.4. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9
4.4.1. Address Forging . . . . . . . . . . . . . . . . . . . 9 4.4.1. Address Forging . . . . . . . . . . . . . . . . . . . 9
4.4.2. Address Mimicking . . . . . . . . . . . . . . . . . . 9 4.4.2. Address Mimicking . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 11 5.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 11
5.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 11 5.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 11
6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 11 6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13 7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . . 14 7.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 15 Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 16
A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 15 A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 16
A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 16 A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 16
A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 16 A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 17
A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 16 A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 17
A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 16 A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 17
A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 17 A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 17
A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 17 A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 18 Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 18
B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 18 B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 18
B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 18 B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 19
B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 18 B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 19
B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 19 B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 19
B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 19 B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 19
B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 19 B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 19
Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 19 Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The Extensible Messaging and Presence Protocol [XMPP] is an The Extensible Messaging and Presence Protocol (XMPP) is an
application profile of the Extensible Markup Language [XML] for application profile of the Extensible Markup Language [XML] for
streaming XML data in close to real time between any two or more streaming XML data in close to real time between any two or more
network-aware entities. The address format for XMPP entities was network-aware entities. The address format for XMPP entities was
originally developed in the Jabber open-source community in 1999, originally developed in the Jabber open-source community in 1999,
first described by [XEP-0029] in 2002, and defined canonically by first described by [XEP-0029] in 2002, and defined canonically by
[RFC3920] in 2004. [RFC3920] in 2004.
As specified in RFC 3920, the XMPP address format re-uses the As specified in RFC 3920, the XMPP address format re-uses the
"stringprep" technology for preparation of non-ASCII characters "stringprep" technology for preparation of non-ASCII characters
[STRINGPREP], including the Nameprep profile for internationalized [STRINGPREP], including the Nameprep profile for internationalized
domain names as specified in [NAMEPREP] and [IDNA2003] along with two domain names as specified in [NAMEPREP] and [IDNA2003] along with two
XMPP-specific profiles for the localpart and resourcepart. However, XMPP-specific profiles for the localpart and resourcepart.
since the publication of RFC 3920, IDNA2003 has been superseded by
IDNA2008 (see [IDNA-PROTO] and related documents). As a result,
other protocols that use stringprep (including XMPP) have begun to
migrate from stringprep toward more "modern" approaches.
Because work on improved handling of internationalized addresses is Since the publication of RFC 3920, IDNA2003 has been superseded by
currently in progress, specifying the XMPP address format in the IDNA2008 (see [IDNA-PROTO] and related documents), which is not based
specification that obsoletes RFC 3920 would unacceptably delay the on stringprep. Following the lead of the IDNA community, other
revision process. Therefore, this specification provides updated technology communities that use stringprep have begun discussions
documentation of the XMPP address format (essentially copied from RFC about migrating away from stringprep toward more "modern" approaches.
3920), with the intent that it can be superseded once work on a new The XMPP community is participating in those discussions in order to
approach to internationalization is complete. find a replacement for the Nodeprep and Resourceprep profiles of
stringprep defined in RFC 3920. However, work on improved handling
of internationalized addresses is currently in progress within the
PRECIS Working Group and at the time of this writing it seems that
such work might take several years to complete. Because all other
aspects of revised documentation for XMPP have been incorporated into
[rfc3920bis], the XMPP Working Group decided to split the XMPP
address format into a separate specification so as not to
significantly delay publication of improved documentation for XMPP
while awaiting the conclusion of work on improved handling of
internationalized addresses.
2. Addresses Therefore, this specification provides corrected documentation of the
XMPP address format using the internationalization technologies
available in 2004 (when RFC 3920 was published), with the intent that
this specification will be superseded as soon as work on a new
approach to preparation and comparison of internationalized strings
has been defined by the PRECIS Working Group and applied to the
specific cases of XMPP localparts and resourceparts.
2.1. Overview 2. Addresses
2.1. Fundamentals
An XMPP entity is anything that is network-addressable and that can An XMPP entity is anything that is network-addressable and that can
communicate using XMPP. For historical reasons, the native address communicate using XMPP. For historical reasons, the native address
of an XMPP entity is called a Jabber Identifier or JID. A valid JID of an XMPP entity is called a Jabber Identifier or JID. A valid JID
is a string of [UNICODE] code points, encoded using [UTF-8], and is a string of [UNICODE] code points, encoded using [UTF-8], and
structured as an ordered sequence of localpart, domainpart, and structured as an ordered sequence of localpart, domainpart, and
resourcepart (where the first two parts are demarcated by the '@' resourcepart (where the first two parts are demarcated by the '@'
character used as a separator, and the last two parts are similarly character used as a separator, and the last two parts are similarly
demarcated by the '/' character). demarcated by the '/' character).
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real JID. real JID.
3. Internationalization Considerations 3. Internationalization Considerations
XMPP servers MUST, and XMPP clients SHOULD, support [IDNA2003] for XMPP servers MUST, and XMPP clients SHOULD, support [IDNA2003] for
domainparts (including the [NAMEPREP] profile of [STRINGPREP]), the domainparts (including the [NAMEPREP] profile of [STRINGPREP]), the
Nodeprep (Appendix A) profile of [STRINGPREP] for localparts, and the Nodeprep (Appendix A) profile of [STRINGPREP] for localparts, and the
Resourceprep (Appendix B) profile of [STRINGPREP] for resourceparts; Resourceprep (Appendix B) profile of [STRINGPREP] for resourceparts;
this enables XMPP addresses to include a wide variety of characters this enables XMPP addresses to include a wide variety of characters
outside the US-ASCII range. Rules for enforcement of the XMPP outside the US-ASCII range. Rules for enforcement of the XMPP
address format are provided in [XMPP]. address format are provided in [rfc3920bis].
4. Security Considerations 4. Security Considerations
4.1. Reuse of Stringprep 4.1. Reuse of Stringprep
The security considerations described in [STRINGPREP] apply to the The security considerations described in [STRINGPREP] apply to the
Nodeprep (Appendix A) and Resourceprep (Appendix B) profiles defined Nodeprep (Appendix A) and Resourceprep (Appendix B) profiles defined
in this document for XMPP localparts and resourceparts. The security in this document for XMPP localparts and resourceparts. The security
considerations described in [STRINGPREP] and [NAMEPREP] apply to the considerations described in [STRINGPREP] and [NAMEPREP] apply to the
Nameprep profile that is re-used here for XMPP domainparts. Nameprep profile that is re-used here for XMPP domainparts.
skipping to change at page 9, line 33 skipping to change at page 9, line 46
entity is able to generate an XML stanza whose 'from' address does entity is able to generate an XML stanza whose 'from' address does
not correspond to the account credentials with which the entity not correspond to the account credentials with which the entity
authenticated onto the network (or an authorization identity provided authenticated onto the network (or an authorization identity provided
during SASL negotiation). For example, address forging occurs if an during SASL negotiation). For example, address forging occurs if an
entity that authenticated as "juliet@im.example.com" is able to send entity that authenticated as "juliet@im.example.com" is able to send
XML stanzas from "nurse@im.example.com" or "romeo@example.net". XML stanzas from "nurse@im.example.com" or "romeo@example.net".
Address forging is difficult in XMPP systems, given the requirement Address forging is difficult in XMPP systems, given the requirement
for sending servers to stamp 'from' addresses and for receiving for sending servers to stamp 'from' addresses and for receiving
servers to verify sending domains via server-to-server authentication servers to verify sending domains via server-to-server authentication
(see [XMPP]). However, address forging is not impossible, since a (see [rfc3920bis]). However, address forging is not impossible,
rogue server could forge JIDs at the sending domain by ignoring the since a rogue server could forge JIDs at the sending domain by
stamping requirement. Therefore, an entity outside the security ignoring the stamping requirement. Therefore, an entity outside the
perimeter of a particular server cannot reliably distinguish between security perimeter of a particular server cannot reliably distinguish
bare JIDs of the form <localpart@domainpart> at that server and thus between bare JIDs of the form <localpart@domainpart> at that server
can authenticate only the domainpart of such JIDs with any level of and thus can authenticate only the domainpart of such JIDs with any
assurance. This specification does not define methods for level of assurance. This specification does not define methods for
discovering or counteracting such rogue servers. discovering or counteracting such rogue servers.
Furthermore, it is possible for an attacker to forge JIDs at other Furthermore, it is possible for an attacker to forge JIDs at other
domains by means of a DNS poisoning attack if DNS security extensions domains by means of a DNS poisoning attack if DNS security extensions
[DNSSEC] are not used. [DNSSEC] are not used.
4.4.2. Address Mimicking 4.4.2. Address Mimicking
Address mimicking occurs when an entity provides legitimate Address mimicking occurs when an entity provides legitimate
authentication credentials for and sends XML stanzas from an account authentication credentials for and sends XML stanzas from an account
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7.1. Normative References 7.1. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[IDNA2003] [IDNA2003]
Faltstrom, P., Hoffman, P., and A. Costello, Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", "Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003. RFC 3490, March 2003.
See Section 1 for an explanation of why the normative
reference to an obsoleted specification is needed.
[KEYWORDS] [KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate 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.
[NAMEPREP] [NAMEPREP]
Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)", Profile for Internationalized Domain Names (IDN)",
RFC 3491, March 2003. RFC 3491, March 2003.
See Section 1 for an explanation of why the normative
reference to an obsoleted specification is needed.
[rfc3920bis]
Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-17 (work
in progress), October 2010.
[STRINGPREP] [STRINGPREP]
Hoffman, P. and M. Blanchet, "Preparation of Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454, Internationalized Strings ("stringprep")", RFC 3454,
December 2002. December 2002.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version [UNICODE] The Unicode Consortium, "The Unicode Standard, Version
3.2.0", 2000. 3.2.0", 2000.
The Unicode Standard, Version 3.2.0 is defined by The The Unicode Standard, Version 3.2.0 is defined by The
Unicode Standard, Version 3.0 (Reading, MA, Addison- Unicode Standard, Version 3.0 (Reading, MA, Addison-
skipping to change at page 14, line 15 skipping to change at page 14, line 41
Standard Annex #28: Unicode 3.2 Standard Annex #28: Unicode 3.2
(http://www.unicode.org/reports/tr28/). (http://www.unicode.org/reports/tr28/).
[UNICODE-SEC] [UNICODE-SEC]
The Unicode Consortium, "Unicode Technical Report #36: The Unicode Consortium, "Unicode Technical Report #36:
Unicode Security Considerations", 2008. Unicode Security Considerations", 2008.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[XMPP] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-16 (work
in progress), September 2010.
7.2. Informative References 7.2. Informative References
[DNS] Mockapetris, P., "Domain names - implementation and [DNS] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[DNSSEC] Arends, R., Austein, R., Larson, M., Massey, D., and S. [DNSSEC] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005. RFC 4033, March 2005.
[IDNA-DEFS] [IDNA-DEFS]
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