Network Working Group P. Saint-Andre
Internet-Draft Cisco
Intended status: Standards Track April 7, 2010
Expires: October 9, 2010
Extensible Messaging and Presence Protocol (XMPP): Address Format
draft-ietf-xmpp-address-00
Abstract
This document defines the format for addresses used in the Extensible
Messaging and Presence Protocol (XMPP), including support for non-
ASCII characters.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 6
3. Internationalization Considerations . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4.1. Stringprep Profiles . . . . . . . . . . . . . . . . . . . 7
4.2. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Address Forging . . . . . . . . . . . . . . . . . . . 8
4.2.2. Address Mimicking . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 10
5.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 10
6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 15
A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 15
A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 15
A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 15
A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 16
A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 16
A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 16
A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 17
B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 17
B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 18
B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 18
B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 18
B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 18
B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 18
Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 18
Appendix D. Copying Conditions . . . . . . . . . . . . . . . . . 19
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
The Extensible Messaging and Presence Protocol [XMPP] is an
application profile of the Extensible Markup Language [XML] for
streaming XML data in close to real time between any two or more
network-aware entities. The address format for such entities was
originally developed in the Jabber open-source community in 1999
(thus for historical reasons the native address of an XMPP entity is
called a Jabber Identifier or JID). In essence, a JID contains up to
three parts, in the arrangement <localpart@domainpart/resourcepart>
(where the localpart and resourcepart are both discretionary and each
part can contain nearly any Unicode code point, encoded according to
[UTF-8]). The JID format was first described by [XEP-0029] in 2002-
2003, then defined canonically by [RFC3920] in 2004. As defined in
RFC 3920, the XMPP address format re-uses the "stringprep" technology
for preparation of non-ASCII characters [STRINGPREP], including the
Nameprep profile for internationalized domain names as specified in
[NAMEPREP] and [IDNA2003] as well as two XMPP-specific profiles for
the localpart and resourcepart. Since the publication of RFC 3920,
IDNA2003 has been superseded by IDNA2008, and other protocols that
use stringprep (including XMPP) have begun to migrate away from that
technology. Because work on improved handling of internationalized
addresses is currently in progress, specifying the XMPP address
format in the revisions to RFC 3920 would unacceptably delay the
revision process. Therefore, this specification provides
documentation of the XMPP address format from RFC 3920, with the
intent that it can be superseded once work on a new approach to
internationalization is complete.
2. Addresses
2.1. Overview
An ENTITY is anything that is network-addressable and that can
communicate using XMPP. For historical reasons, the native address
of an XMPP entity is called a JABBER IDENTIFIER or JID. A valid JID
contains a set of ordered elements formed of an XMPP localpart,
domainpart, and resourcepart.
The syntax for a JID is defined as follows using the Augmented
Backus-Naur Form as specified in [ABNF].
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jid = [ localpart "@" ] domain [ "/" resource ]
localpart = 1*(nodepoint)
; a "nodepoint" is a UTF-8 encoded Unicode code
; point that satisfies the Nodeprep profile of
; stringprep
domain = fqdn / address-literal
fqdn = *(ldhlabel ".") toplabel
ldhlabel = letdig [*61(ldh) letdig]
toplabel = ALPHA *61(ldh) letdig
letdig = ALPHA / DIGIT
ldh = ALPHA / DIGIT / "-"
address-literal = IPv4address / IPv6address
; the "IPv4address" and "IPv6address" rules are
; defined in RFC 3986
resource = 1*(resourcepoint)
; a "resourcepoint" is a UTF-8 encoded Unicode
; code point that satisfies the Resourceprep
; profile of stringprep
All JIDs are based on the foregoing structure. One common use of
this structure is to identify a messaging and presence account, the
server that hosts the account, and a connected resource (e.g., a
specific device) in the form of <localpart@domain/resource>.
However, localparts other than clients are possible; for example, a
specific chat room offered by a multi-user conference service (see
[XEP-0045]) could be addressed as <room@service> (where "room" is the
name of the chat room and "service" is the hostname of the multi-user
conference service) and a specific occupant of such a room could be
addressed as <room@service/nick> (where "nick" is the occupant's room
nickname). Many other JID types are possible (e.g., <domain/
resource> could be a server-side script or service).
Each allowable portion of a JID (localpart, domainpart, and
resourcepart) MUST NOT be more than 1023 bytes in length, resulting
in a maximum total size (including the '@' and '/' separators) of
3071 bytes.
Note: While the format of a JID is consistent with [URI], an
entity's address on an XMPP network MUST be represented as a JID
(without a URI scheme) and not a [URI] or [IRI] as specified in
[XMPP-URI]; the latter specification is provided only for
identification and interaction outside the context of the XMPP
wire protocol itself.
2.2. Domainpart
The DOMAINPART of a JID is that portion after the '@' character (if
any) and before the '/' character (if any); it is the primary
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identifier and is the only REQUIRED element of a JID (a mere
domainpart is a valid JID). Typically a domainpart identifies the
"home" server to which clients connect for XML routing and data
management functionality. However, it is not necessary for an XMPP
domainpart to identify an entity that provides core XMPP server
functionality (e.g., a domainpart can identity an entity such as a
multi-user conference service, a publish-subscribe service, or a user
directory).
Note: A single server can service multiple domainparts, i.e.,
multiple local domains; this is typically referred to as virtual
hosting.
The domainpart for every server or service that will communicate over
a network SHOULD be a fully qualified domain name (see [DNS]); while
the domainpart MAY be either an Internet Protocol (IPv4 or IPv6)
address or a text label that is resolvable on a local network
(commonly called an "unqualified hostname"), it is possible that
domainparts that are IP addresses will not be acceptable to other
services for the sake of interdomain communication. Furthermore,
domainparts that are unqualified hostnames MUST NOT be used on public
networks but MAY be used on private networks.
Note: If the domainpart includes a final character considered to
be a label separator (dot) by [IDNA2003] or [DNS], this character
MUST be stripped from the domainpart before the JID of which it is
a part is used for the purpose of routing an XML stanza, comparing
against another JID, or constructing an [XMPP-URI]; in particular,
the character MUST be stripped before any other canonicalization
steps are taken, such as application of the [NAMEPREP] profile of
[STRINGPREP] or completion of the ToASCII operation as described
in [IDNA2003].
A domainpart MUST be an "internationalized domain name" as defined in
[IDNA2003], that is, "a domain name in which every label is an
internationalized label". When preparing a text label (consisting of
a sequence of Unicode code points) for representation as an
internationalized label in the process of constructing an XMPP
domainpart or comparing two XMPP domainparts, an application MUST
ensure that for each text label it is possible to apply without
failing the ToASCII operation specified in [IDNA2003] with the
UseSTD3ASCIIRules flag set (thus forbidding ASCII code points other
than letters, digits, and hyphens). If the ToASCII operation can be
applied without failing, then the label is an internationalized
label. An internationalized domain name (and therefore an XMPP
domainpart) is constructed from its constituent internationalized
labels by following the rules specified in [IDNA2003].
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Note: The ToASCII operation includes application of the [NAMEPREP]
profile of [STRINGPREP] and encoding using the algorithm specified
in [PUNYCODE]; for details, see [IDNA2003]. Although the output
of the ToASCII operation is not used in XMPP, it MUST be possible
to apply that operation without failing.
In the terms of IDNA2008 [IDNA-DEFS], the domainpart of a JID is a
"domain name slot".
2.3. Localpart
The LOCALPART of a JID is an optional identifier placed before the
domainpart and separated from the latter by the '@' character.
Typically a localpart uniquely identifies the entity requesting and
using network access provided by a server (i.e., a local account),
although it can also represent other kinds of entities (e.g., a chat
room associated with a multi-user conference service). The entity
represented by an XMPP localpart is addressed within the context of a
specific domain.
A localpart MUST NOT be zero bytes in length and, as for all portions
of a JID, MUST NOT be more than 1023 bytes in length.
A localpart MUST be formatted such that the Nodeprep profile of
[STRINGPREP] can be applied without failing (see Appendix A). Before
comparing two localparts, an application MUST first ensure that the
Nodeprep profile has been applied to each identifier (the profile
need not be applied each time a comparison is made, as long as it has
been applied before comparison).
2.4. Resourcepart
The resourcepart of a JID is an optional identifier placed after the
domainpart and separated from the latter by the '/' character. A
resourcepart can modify either a <localpart@domain> address or a mere
<domain> address. Typically a resourcepart uniquely identifies a
specific connection (e.g., a device or location) or object (e.g., a
participant in a multi-user conference room) belonging to the entity
associated with an XMPP localpart at a local domain.
When an XMPP address does not include a resourcepart (i.e., when it
is of the form <domain> or <localpart@domain>), it is referred to as
a BARE JID. When an XMPP address includes a resourcepart (i.e., when
it is of the form <domain/resource> or <localpart@domain/resource>),
is referred to as a FULL JID.
A resourcepart MUST NOT be zero bytes in length and, as for all
portions of a JID, MUST NOT be more than 1023 bytes in length.
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A resourcepart MUST be formatted such that the Resourceprep profile
of [STRINGPREP] can be applied without failing (see Appendix B).
Before comparing two resourceparts, an application MUST first ensure
that the Resourceprep profile has been applied to each identifier
(the profile need not be applied each time a comparison is made, as
long as it has been applied before comparison).
Note: For historical reasons, the term "resource identifier" is
often used in XMPP to refer to the optional portion of an XMPP
address that follows the domainpart and the "/" separator
character; to help prevent confusion between an XMPP "resource
identifier" and the meanings of "resource" and "identifier"
provided in Section 1.1 of [URI], this specification typically
uses the term "resourcepart" instead of "resource identifier" (as
in RFC 3920).
XMPP entities SHOULD consider resourceparts to be opaque strings and
SHOULD NOT impute meaning to any given resourcepart. In particular,
the use of the '/' character as a separator between the domainpart
and the resourcepart does not imply that XMPP addresses are
hierarchical in the way that, say, HTTP addresses are hierarchical;
thus for example an XMPP address of the form
<localpart@domain/foo/bar> does not identify a resource "bar" that
exists below a resource "foo" in a hierarchy of resources associated
with the entity "localpart@domain".
3. Internationalization Considerations
An XMPP server MUST support and enforce [IDNA2003] for domainparts,
the Nodeprep (Appendix A) profile of [STRINGPREP] for localparts, and
the Resourceprep (Appendix B) profile of [STRINGPREP] for
resourceparts; this enables XMPP addresses to include a wide variety
of Unicode characters outside the US-ASCII range.
4. Security Considerations
4.1. Stringprep Profiles
XMPP makes use of the [NAMEPREP] profile of [STRINGPREP] for
processing of domainparts; for security considerations related to
Nameprep, refer to the appropriate section of [NAMEPREP].
In addition, XMPP defines two profiles of [STRINGPREP]: Nodeprep
(Appendix A) for localparts and Resourceprep (Appendix B) for
resourceparts.
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The Unicode and ISO/IEC 10646 repertoires have many characters that
look similar. In many cases, users of security protocols might
perform visual matching, such as when comparing the names of trusted
third parties. Because it is impossible to map similar-looking
characters without a great deal of context (such as knowing the fonts
used), stringprep does nothing to map similar-looking characters
together, nor to prohibit some characters because they look like
others.
A localpart can be employed as one part of an entity's address in
XMPP. One common usage is as the username of an instant messaging
user; another is as the name of a multi-user conference room; and
many other kinds of entities could use localparts as part of their
addresses. The security of such services could be compromised based
on different interpretations of the internationalized localpart; for
example, a user entering a single internationalized localpart could
access another user's account information, or a user could gain
access to a hidden or otherwise restricted chat room or service.
A resourcepart can be employed as one part of an entity's address in
XMPP. One common usage is as the name for an instant messaging
user's connected resource; another is as the nickname of a user in a
multi-user conference room; and many other kinds of entities could
use resourceparts as part of their addresses. The security of such
services could be compromised based on different interpretations of
the internationalized resourcepart; for example, a user could attempt
to initiate multiple connections with the same name, or a user could
send a message to someone other than the intended recipient in a
multi-user conference room.
4.2. Address Spoofing
As discussed in [XEP-0165], there are two forms of address spoofing:
forging and mimicking.
4.2.1. Address Forging
In the context of XMPP technologies, address forging occurs when an
entity is able to generate an XML stanza whose 'from' address does
not correspond to the account credentials with which the entity
authenticated onto the network (or an authorization identity provided
during SASL negotiation). For example, address forging occurs if an
entity that authenticated as "juliet@im.example.com" is able to send
XML stanzas from "nurse@im.example.com" or "romeo@example.net".
Address forging is difficult in XMPP systems, given the requirement
for sending servers to stamp 'from' addresses and for receiving
servers to verify sending domains via server-to-server
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authentication. However, address forging is not impossible, since a
rogue server could forge JIDs at the sending domain by ignoring the
stamping requirement. A rogue server could even forge JIDs at other
domains by means of a DNS poisoning attack if [DNSSEC] is not used.
This specification does not define methods for discovering or
counteracting such rogue servers.
Note: An entity outside the security perimeter of a particular server
cannot reliably distinguish between bare JIDs of the form
<localpart@domain> at that server, since the server could forge any
such JID; therefore only the domainpart can be authenticated or
authorized with any level of assurance.
4.2.2. Address Mimicking
Address mimicking occus when an entity provides legitimate
authentication credentials for and sends XML stanzas from an account
whose JID appears to a human user to be the same as another JID. For
example, in some XMPP clients the address "paypa1@example.org"
(spelled with the number one as the final character of the localpart)
might appear to be the same as "paypal@example.org (spelled with the
lower-case version of the letter "L"), especially on casual visual
inspection; this phenomenon is sometimes called "typejacking". A
more sophisticated example of address mimicking might involve the use
of characters from outside the US-ASCII range, such as the Cherokee
characters U+13DA U+13A2 U+13B5 U+13AC U+13A2 U+13AC U+13D2 instead
of the US-ASCII characters "STPETER".
In some examples of address mimicking, it is unlikely that the
average user could tell the difference between the real JID and the
fake JID. (Naturally, there is no way to distinguish with full
certainty which is the fake JID and which is the real JID; in some
communication contexts, the JID with Cherokee characters might be the
real JID and the JID with US-ASCII characters might thus appear to be
the fake JID.) Because JIDs can contain almost any Unicode
character, it can be relatively easy to mimic some JIDs in XMPP
systems. The possibility of address mimicking introduces security
vulnerabilities of the kind that have also plagued the World Wide
Web, specifically the phenomenon known as phishing.
Mimicked addresses that involve characters from only one character
set or from the character set typically employed by a particular user
are not easy to combat (e.g., the simple typejacking attack
previously described, which relies on a surface similarity between
the characters "1" and "l" in some presentations). However, mimicked
addresses that involve characters from more than one character set,
or from a character set not typically employed by a particular user,
can be mitigated somewhat through intelligent presentation. In
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particular, every human user of an XMPP technology presumably has a
preferred language (or, in some cases, a small set of preferred
languages), which an XMPP application SHOULD gather either explicitly
from the user or implicitly via the operating system of the user's
device. Furthermore, every language has a range (or a small set of
ranges) of characters normally used to represent that language in
textual form. Therefore, an XMPP application SHOULD warn the user
when presenting a JID that uses characters outside the normal range
of the user's preferred language(s). This recommendation is not
intended to discourage communication across language communities;
instead, it recognizes the existence of such language communities and
encourages due caution when presenting unfamiliar character sets to
human users.
For more detailed recommendations regarding prevention of address
mimicking in XMPP systems, refer to [XEP-0165].
5. IANA Considerations
The following sections update the registrations provided in
[RFC3920].
5.1. Nodeprep Profile of Stringprep
The Nodeprep profile of stringprep is defined under Nodeprep
(Appendix A). The IANA has registered Nodeprep in the stringprep
profile registry.
Name of this profile:
Nodeprep
RFC in which the profile is defined:
XXXX
Indicator whether or not this is the newest version of the profile:
This is the first version of Nodeprep
5.2. Resourceprep Profile of Stringprep
The Resourceprep profile of stringprep is defined under Resourceprep
(Appendix B). The IANA has registered Resourceprep in the stringprep
profile registry.
Name of this profile:
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Resourceprep
RFC in which the profile is defined:
XXXX
Indicator whether or not this is the newest version of the profile:
This is the first version of Resourceprep
6. Conformance Requirements
This section describes a protocol feature set that summarizes the
conformance requirements of this specification. This feature set is
appropriate for use in software certification, interoperability
testing, and implementation reports. For each feature, this section
provides the following information:
o A human-readable name
o An informational description
o A reference to the particular section of this document that
normatively defines the feature
o Whether the feature applies to the Client role, the Server role,
or both (where "N/A" signifies that the feature is not applicable
to the specified role)
o Whether the feature MUST or SHOULD be implemented, where the
capitalized terms are to be understood as described in [TERMS]
Note: The feature set specified here attempts to adhere to the
concepts and formats proposed by Larry Masinter within the IETF's
NEWTRK Working Group in 2005, as captured in [INTEROP]. Although
this feature set is more detailed than called for by [REPORTS], it
provides a suitable basis for the generation of implementation
reports to be submitted in support of advancing this specification
from Proposed Standard to Draft Standard in accordance with
[PROCESS].
Feature: address-domain-length
Description: Ensure that the domainpart of an XMPP address is
limited to 1023 bytes in length.
Section: Section 2.2
Roles: Both MUST.
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Feature: address-domain-prep
Description: Ensure that the domainpart of an XMPP address conforms
to the Nameprep profile of Stringprep.
Section: Section 2.2
Roles: Client SHOULD, Server MUST.
Feature: address-localpart-length
Description: Ensure that the localpart of an XMPP address is limited
to 1023 bytes in length.
Section: Section 2.3
Roles: Both MUST.
Feature: address-localpart-prep
Description: Ensure that the localpart of an XMPP address conforms
to the Nodeprep profile of Stringprep.
Section: Section 2.3
Roles: Client SHOULD, Server MUST.
Feature: address-resource-length
Description: Ensure that the resourcepart of an XMPP address is
limited to 1023 bytes in length.
Section: Section 2.4
Roles: Both MUST.
Feature: address-resource-prep
Description: Ensure that the resourcepart of an XMPP address
conforms to the Resourceprep profile of Stringprep.
Section: Section 2.2
Roles: Client SHOULD, Server MUST.
7. References
7.1. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[IDNA2003]
Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
[NAMEPREP]
Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)",
RFC 3491, March 2003.
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[STRINGPREP]
Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[TERMS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
3.2.0", 2000.
The Unicode Standard, Version 3.2.0 is defined by The
Unicode Standard, Version 3.0 (Reading, MA, Addison-
Wesley, 2000. ISBN 0-201-61633-5), as amended by the
Unicode Standard Annex #27: Unicode 3.1
(http://www.unicode.org/reports/tr27/) and by the Unicode
Standard Annex #28: Unicode 3.2
(http://www.unicode.org/reports/tr28/).
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[XMPP] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-06 (work
in progress), March 2010.
7.2. Informative References
[DNS] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[DNSSEC] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[IDNA-DEFS]
Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
draft-ietf-idnabis-defs-13 (work in progress),
January 2010.
[INTEROP] Masinter, L., "Formalizing IETF Interoperability
Reporting", draft-ietf-newtrk-interop-reports-00 (work in
progress), October 2005.
[IRI] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
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[PROCESS] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[PUNYCODE]
Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, March 2003.
[REPORTS] Dusseault, L. and R. Sparks, "Guidance on Interoperation
and Implementation Reports for Advancement to Draft
Standard", BCP 9, RFC 5657, September 2009.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[XEP-0029]
Kaes, C., "Definition of Jabber Identifiers (JIDs)", XSF
XEP 0029, October 2003.
[XEP-0030]
Hildebrand, J., Millard, P., Eatmon, R., and P. Saint-
Andre, "Service Discovery", XSF XEP 0030, June 2008.
[XEP-0045]
Saint-Andre, P., "Multi-User Chat", XSF XEP 0045,
January in progress, last updated 2010.
[XEP-0060]
Millard, P., Saint-Andre, P., and R. Meijer, "Publish-
Subscribe", XSF XEP 0060, September 2008.
[XEP-0165]
Saint-Andre, P., "Best Practices to Prevent JID
Mimicking", XSF XEP 0165, December 2007.
[XEP-0271]
Saint-Andre, P. and R. Meijer, "XMPP Nodes", XSF XEP 0271,
June 2009.
[XML] Paoli, J., Maler, E., Sperberg-McQueen, C., Yergeau, F.,
and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20060816, August 2006,
<http://www.w3.org/TR/2006/REC-xml-20060816>.
Saint-Andre Expires October 9, 2010 [Page 14]
Internet-Draft XMPP Address Format April 2010
[XMPP-URI]
Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)",
RFC 5122, February 2008.
Appendix A. Nodeprep
A.1. Introduction
This appendix defines the "Nodeprep" profile of stringprep. As such,
it specifies processing rules that will enable users to enter
internationalized localparts in the Extensible Messaging and Presence
Protocol (XMPP) and have the highest chance of getting the content of
the strings correct. (An XMPP localpart is the optional portion of
an XMPP address that precedes an XMPP domainpart and the '@'
separator; it is often but not exclusively associated with an instant
messaging username.) These processing rules are intended only for
XMPP localparts and are not intended for arbitrary text or any other
aspect of an XMPP address.
This profile defines the following, as required by [STRINGPREP]:
o The intended applicability of the profile: internationalized
localparts within XMPP
o The character repertoire that is the input and output to
stringprep: Unicode 3.2, specified in Section 2 of this Appendix
o The mappings used: specified in Section 3
o The Unicode normalization used: specified in Section 4
o The characters that are prohibited as output: specified in Section
5
o Bidirectional character handling: specified in Section 6
A.2. Character Repertoire
This profile uses Unicode 3.2 with the list of unassigned code points
being Table A.1, both defined in Appendix A of [STRINGPREP].
A.3. Mapping
This profile specifies mapping using the following tables from
[STRINGPREP]:
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Table B.1
Table B.2
A.4. Normalization
This profile specifies the use of Unicode normalization form KC, as
described in [STRINGPREP].
A.5. Prohibited Output
This profile specifies the prohibition of using the following tables
from [STRINGPREP].
Table C.1.1
Table C.1.2
Table C.2.1
Table C.2.2
Table C.3
Table C.4
Table C.5
Table C.6
Table C.7
Table C.8
Table C.9
In addition, the following additional Unicode characters are also
prohibited:
U+0022 (QUOTATION MARK), i.e., "
U+0026 (AMPERSAND), i.e., &
U+0027 (APOSTROPHE), i.e., '
U+002F (SOLIDUS), i.e., /
U+003A (COLON), i.e., :
U+003C (LESS-THAN SIGN), i.e., <
U+003E (GREATER-THAN SIGN), i.e., >
U+0040 (COMMERCIAL AT), i.e., @
A.6. Bidirectional Characters
This profile specifies checking bidirectional strings, as described
in Section 6 of [STRINGPREP].
A.7. Notes
Because the additional characters prohibited by Nodeprep are
prohibited after normalization, an implementation MUST NOT enable a
human user to input any Unicode code point whose decomposition
includes those characters; such code points include but are not
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necessarily limited to the following (refer to [UNICODE] for complete
information).
o U+2100 (ACCOUNT OF)
o U+2101 (ADDRESSED TO THE SUBJECT)
o U+2105 (CARE OF)
o U+2106 (CADA UNA)
o U+226E (NOT LESS-THAN)
o U+226F (NOT GREATER-THAN)
o U+2A74 (DOUBLE COLON EQUAL)
o U+FE13 (SMALL COLON)
o U+FE60 (SMALL AMPERSAND)
o U+FE64 (SMALL LESS-THAN SIGN)
o U+FE65 (SMALL GREATER-THAN SIGN)
o U+FE6B (SMALL COMMERCIAL AT)
o U+FF02 (FULLWIDTH QUOTATION MARK)
o U+FF06 (FULLWIDTH AMPERSAND)
o U+FF07 (FULLWIDTH APOSTROPHE)
o U+FF0F (FULLWIDTH SOLIDUS)
o U+FF1A (FULLWIDTH COLON)
o U+FF1C (FULLWIDTH LESS-THAN SIGN)
o U+FF1E (FULLWIDTH GREATER-THAN SIGN)
o U+FF20 (FULLWIDTH COMMERCIAL AT)
Appendix B. Resourceprep
B.1. Introduction
This appendix defines the "Resourceprep" profile of stringprep. As
such, it specifies processing rules that will enable users to enter
internationalized resourceparts in the Extensible Messaging and
Presence Protocol (XMPP) and have the highest chance of getting the
content of the strings correct. (An XMPP resourcepart is the
optional portion of an XMPP address that follows an XMPP domainpart
and the '/' separator.) These processing rules are intended only for
XMPP resourceparts and are not intended for arbitrary text or any
other aspect of an XMPP address.
This profile defines the following, as required by [STRINGPREP]:
o The intended applicability of the profile: internationalized
resourceparts within XMPP
o The character repertoire that is the input and output to
stringprep: Unicode 3.2, specified in Section 2 of this Appendix
o The mappings used: specified in Section 3
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o The Unicode normalization used: specified in Section 4
o The characters that are prohibited as output: specified in Section
5
o Bidirectional character handling: specified in Section 6
B.2. Character Repertoire
This profile uses Unicode 3.2 with the list of unassigned code points
being Table A.1, both defined in Appendix A of [STRINGPREP].
B.3. Mapping
This profile specifies mapping using the following tables from
[STRINGPREP]:
Table B.1
B.4. Normalization
This profile specifies the use of Unicode normalization form KC, as
described in [STRINGPREP].
B.5. Prohibited Output
This profile specifies the prohibition of using the following tables
from [STRINGPREP].
Table C.1.2
Table C.2.1
Table C.2.2
Table C.3
Table C.4
Table C.5
Table C.6
Table C.7
Table C.8
Table C.9
B.6. Bidirectional Characters
This profile specifies checking bidirectional strings, as described
in Section 6 of [STRINGPREP].
Appendix C. Differences From RFC 3920
Based on consensus derived from implementation and deployment
experience as well as formal interoperability testing, the following
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substantive modifications were made from RFC 3920.
o Corrected the ABNF syntax for JIDs to prevent zero-length
localparts, domainparts, and resourceparts.
o To avoid confusion with the term "node" as used in [XEP-0030] and
[XEP-0060] (see also [XEP-0271]), changed the term "node
identifier" to "localpart" (but retained the name "Nodeprep" for
backward compatibility).
o To avoid confusion with the terms "resource" and "identifier" as
used in [URI], changed the term "resource identifier" to
"resourcepart".
o Corrected the nameprep processing rules to require use of the
UseSTD3ASCIIRules flag.
Appendix D. Copying Conditions
Regarding this entire document or any portion of it, the author makes
no guarantees and is not responsible for any damage resulting from
its use. The author grants irrevocable permission to anyone to use,
modify, and distribute it in any way that does not diminish the
rights of anyone else to use, modify, and distribute it, provided
that redistributed derivative works do not contain misleading author
or version information. Derivative works need not be licensed under
similar terms.
Index
B
Bare JID 6
D
Domainpart 4
E
Entity 3
F
Full JID 6
J
Jabber Identifier 3
L
Localpart 6
R
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Resourcepart 6
Author's Address
Peter Saint-Andre
Cisco
Email: psaintan@cisco.com
Saint-Andre Expires October 9, 2010 [Page 20]
