XMPP P. Saint-Andre
Internet-Draft Cisco Systems, Inc.
Obsoletes: 6122 (if approved) April 9, 2012
Intended status: Standards Track
Expires: October 11, 2012
Extensible Messaging and Presence Protocol (XMPP): Address Format
draft-ietf-xmpp-6122bis-01
Abstract
This document defines the address format for the Extensible Messaging
and Presence Protocol (XMPP), including support for code points
outside the US-ASCII range. This document obsoletes RFC 6122.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 11, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 7
3. Enforcement in JIDs and JID Parts . . . . . . . . . . . . . . 8
4. Internationalization Considerations . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5.1. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 10
5.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 10
5.3. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 11
5.3.1. Address Forging . . . . . . . . . . . . . . . . . . . 11
5.3.2. Address Mimicking . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6.1. Use of NameClass . . . . . . . . . . . . . . . . . . . . . 13
6.2. Use of FreeClass . . . . . . . . . . . . . . . . . . . . . 13
7. Conformance Requirements . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . . 15
8.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Differences from RFC 6122 . . . . . . . . . . . . . . 19
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
1.1. Overview
The Extensible Messaging and Presence Protocol (XMPP) [RFC6120] 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 XMPP entities was
originally developed in the Jabber open-source community in 1999,
first described by [XEP-0029] in 2002, and then defined canonically
by [RFC3920] in 2004 and [RFC6122] in 2011.
As specified in RFC 3920 and RFC 6122, the XMPP address format used
the "stringprep" technology for preparation of non-ASCII characters
[RFC3454]. Following the migration of internationalized domain names
away from stringprep, this document defines the XMPP address format
in a way that no longer depends on stringprep. Instead, this
document builds upon the internationalization framework defined by
the IETF's PRECIS Working Group [FRAMEWORK].
This document obsoletes RFC 6122.
1.2. Terminology
Many important terms used in this document are defined in
[FRAMEWORK], [RFC5890], [RFC6120], [RFC6365], and [UNICODE].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. Addresses
2.1. Fundamentals
An XMPP 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 ("JID"). A valid JID
is a string of [UNICODE] code points, encoded using UTF-8 [RFC3629],
and structured as an ordered sequence of localpart, domainpart, and
resourcepart (where the first two parts are demarcated by the '@'
character used as a separator, and the last two parts are similarly
demarcated by the '/' character).
The syntax for a JID is defined as follows using the Augmented
Backus-Naur Form (ABNF) as specified in [RFC5234].
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jid = [ localpart "@" ] domainpart [ "/" resourcepart ]
localpart = 1*(localpoint)
;
; a "localpoint" is a UTF-8 encoded Unicode
; code point that conforms to the localpart
; subclass of the "NameClass" string class
; defined in draft-ietf-precis-framework
;
domainpart = IP-literal / IPv4address / ifqdn
;
; the "IPv4address" and "IP-literal" rules are
; defined in RFC 3986, and the first-match-wins
; (a.k.a. "greedy") algorithm described in RFC
; 3986 applies to the matching process
;
; note well that reuse of the IP-literal rule
; from RFC 3986 implies that IPv6 addresses are
; enclosed in square brackets (i.e., beginning
; with '[' and ending with ']')
;
ifqdn = 1*(domainpoint)
;
; a "domainpoint" is a UTF-8 encoded Unicode
; code point that conforms to the "domain name"
; string class effectively defined in RFC 5890
;
resourcepart = 1*(resourcepoint)
;
; a "resourcepoint" is a UTF-8 encoded Unicode
; code point that conforms to the resourcepart
; subclass of the "FreeClass" string class
; defined in draft-ietf-precis-framework
;
All JIDs are based on the foregoing structure.
Each allowable portion of a JID (localpart, domainpart, and
resourcepart) MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length, resulting in a maximum total size
(including the '@' and '/' separators) of 3071 bytes.
Implementation Note: When dividing a JID into its component parts,
an implementation needs to match the separator characters '@' and
'/' before applying any transformation algorithms, which might
decompose certain Unicode code points to the separator characters
(e.g., U+FE6B SMALL COMMERCIAL AT might decompose to U+0040
COMMERCIAL AT).
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This document defines the native format for JIDs; see [RFC5122] for
information about the representation of a JID as a Uniform Resource
Identifier (URI) [RFC3986] or Internationalized Resource Identifier
(IRI) [RFC3987] and the extraction of a JID from an XMPP URI or IRI.
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
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 identify an entity such as a
multi-user chat service [XEP-0045], a publish-subscribe service
[XEP-0060], or a user directory).
The domainpart for every XMPP service MUST be a fully qualified
domain name (FQDN; see [RFC1035]), IPv4 address, IPv6 address, or
unqualified hostname (i.e., a text label that is resolvable on a
local network).
Interoperability Note: Domainparts that are IP addresses might not
be accepted by other services for the sake of server-to-server
communication, and domainparts that are unqualified hostnames
cannot be used on public networks because they are resolvable only
on a local network.
If the domainpart includes a final character considered to be a label
separator (dot) by [RFC1035], 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 [RFC5122]. In particular, the character MUST be
stripped before any other canonicalization steps are taken.
A domainpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points. Naturally, the length
limits of [RFC1035] apply, and nothing in this document is to be
interpreted as overriding those more fundamental limits.
In the terms of IDNA2008 [RFC5890], the domainpart of a JID is a
"domain name slot".
A domainpart consisting of a fully qualified domain name MUST be an
"internationalized domain name" as defined in [RFC5890] and MUST
consist only of Unicode code points that conform to the rules
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specified in [RFC5892].
For the purposes of communication over XMPP, the domainpart of a JID
MUST be treated as follows, where the operations specified MUST be
completed in the order shown:
1. Uppercase and titlecase characters MUST be mapped to their
lowercase equivalents.
2. Additional mappings MAY be applied, such as those defined in
[MAPPINGS].
3. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
4. Each A-label MUST be converted to a U-label.
With regard to directionality, the "Bidi Rule" provided in [RFC5893]
applies.
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 chat service [XEP-0045]). The
entity represented by an XMPP localpart is addressed within the
context of a specific domain (i.e., <localpart@domainpart>).
A localpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points.
A localpart MUST consist only of Unicode code points that conform to
the "NameClass" base string class defined in [FRAMEWORK], with the
exception of the following characters that are explicitly disallowed
in XMPP localparts:
U+0022 (QUOTATION MARK), i.e., "
U+0026 (AMPERSAND), i.e., &
U+0027 (APOSTROPHE), i.e., '
U+002F (SOLIDUS), i.e., /
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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., @
The localpart of a JID MUST be treated as follows, where the
operations specified MUST be completed in the order shown:
1. Uppercase and titlecase characters MUST be mapped to their
lowercase equivalents.
2. Additional mappings MAY be applied, such as those defined in
[MAPPINGS].
3. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
With regard to directionality, the "Bidi Rule" provided in [RFC5893]
applies.
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@domainpart> address or a
mere <domainpart> address. Typically a resourcepart uniquely
identifies a specific connection (e.g., a device or location) or
object (e.g., an occupant in a multi-user chat room [XEP-0045])
belonging to the entity associated with an XMPP localpart at a domain
(i.e., <localpart@domainpart/resourcepart>).
A resourcepart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. This rule is to be enforced after any
mapping or normalization of code points.
A resourcepart MUST consist only of Unicode code points that conform
to the "FreeClass" base string class defined in [FRAMEWORK].
The localpart of a JID MUST be treated as follows, where the
operations specified MUST be completed in the order shown:
1. Uppercase and titlecase characters MAY be mapped to their
lowercase equivalents.
2. Additional mappings MAY be applied, such as those defined in
[MAPPINGS].
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3. All characters MUST be mapped using Unicode Normalization Form C
(NFC).
With regard to directionality, the "Bidi Rule" provided in [RFC5893]
applies.
XMPP entities SHOULD consider resourceparts to be opaque strings and
SHOULD NOT impute meaning to any given resourcepart. In particular:
o 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@domainpart/foo/bar> does not identify a resource "bar"
that exists below a resource "foo" in a hierarchy of resources
associated with the entity "localpart@domainpart".
o The '@' character is allowed in the resourcepart and is often used
in the "nick" shown in XMPP chatrooms [XEP-0045]. For example,
the JID <room@chat.example.com/user@host> describes an entity who
is an occupant of the room <room@chat.example.com> with an
(asserted) nick of <user@host>. However, chatroom services do not
necessarily check such an asserted nick against the occupant's
real JID.
3. Enforcement in JIDs and JID Parts
Enforcement of the XMPP address format rules is the responsibility of
XMPP servers. Although XMPP clients are encouraged to prepare
complete JIDs and parts of JIDs in accordance with these rules before
including them in protocol slots within XMPP streams, XMPP servers
hold the primary responsibility for enforcing the rules.
Enforcement applies to complete JIDs and to parts of JIDs. To
facilitate implementation, this document defines the concepts of "JID
slot", "localpart slot", and "resourcepart slot" (similar to the
concept of a "domain name slot" for IDNA2008 defined in Section
2.3.2.6 of [RFC5890]):
JID Slot: An XML element or attribute explicitly designated in XMPP
or in XMPP extensions for carrying a complete JID.
Localpart Slot: An XML element or attribute explicitly designated in
XMPP or in XMPP extensions for carrying the localpart of a JID.
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Resourcepart Slot: An XML element or attribute explicitly designated
in XMPP or in XMPP extensions for carrying the resourcepart of a
JID.
In general, servers are responsible for enforcing the address format
rules when receiving protocol elements from clients where the server
is expected to process or act on such elements; two examples from
[RFC6120] are the 'to' attribute on XML stanzas (which is a JID slot
used by XMPP servers for routing of outbound stanzas) and the
<resource/> child of the <bind/> element (which is a resourcepart
slot used by XMPP servers for binding of a resource to an account for
routing of stanzas between the server and a particular client).
However, servers are not responsible for enforcing the rules when the
protocol elements are intended for communication among other
entities; two examples are the 'initiator' attribute in the Jingle
extension [XEP-0166] (which is a JID slot used for client-to-client
coordination of multimedia sessions) and the 'nick' attribute in the
Multi-User Chat extension [XEP-0045] (which is a resourcepart slot
used for administrative purposes in the context of XMPP chatrooms).
This document does not provide an exhaustive list of JID slots,
localpart slots, or resourcepart slots. However, implementers of
core XMPP servers are advised to consider as JID slots at least the
following elements and attributes:
o The 'from' and 'to' stream attributes and the 'from' and 'to'
stanza attributes [RFC6120].
o The 'jid' attribute of the roster <item/> element for contact list
management [RFC6121].
o The 'value' attribute of the <item/> element for Privacy Lists
[RFC3921] [XEP-0016] when the value of the 'type' attribute is
"jid".
o The 'jid' attribute of the <item/> element for Service Discovery
defined in [XEP-0030].
o The <value/> element for Data Forms [XEP-0004] when the 'type'
attribute is "jid-single" or "jid-multi".
o The 'jid' attribute of the <conference/> element for Bookmark
Storage [XEP-0048].
o The <JABBERID/> of the <vCard/> element for vCard 3.0 [XEP-0054]
and the <uri/> child of the <impp/> element for vCard 4.0
[XEP-0292] when the XML character data identifies an XMPP URI
[RFC5122].
o The 'from' attribute of the <delay/> element for Delayed Delivery
[XEP-0203].
o The 'jid' attribute of the <item/> element for Simple
Communications Blocking [XEP-0191].
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o The 'from' and 'to' attributes of the <result/> and <verify/>
elements for Server Dialback [RFC3921], [XEP-0220].
o The 'from' and 'to' attributes of the <amp/> element for Advanced
Message Processing [XEP-0079].
o The 'from' and 'to' attributes of the <iq/>, <message/>, and
<presence/> elements for the Jabber Component Protocol [XEP-0114].
Developers of XMPP clients and specialized XMPP components are
advised to check the appropriate specifications for JID slots,
localpart slots, and resourcepart slots in XMPP protocol extensions
such as Multi-User Chat [XEP-0045], Publish-Subscribe [XEP-0060],
SOCKS5 Bytestreams [XEP-0065], In-Band Registration [XEP-0077],
Roster Item Exchange [XEP-0144], and Jingle [XEP-0166].
4. Internationalization Considerations
XMPP applications MUST support IDNA2008 for domainparts, the
"NameClass" string class from [FRAMEWORK] for localparts (with the
exception of certain ASCII characters specified under Section 2.3),
and the "FreeClass" string class from [FRAMEWORK] for resourceparts.
This enables XMPP addresses to include a wide variety of characters
outside the US-ASCII range. Rules for enforcement of the XMPP
address format are provided in [RFC6120] and specifications for
various XMPP extensions.
For backward compatibility, many XMPP applications support IDNA2003
[RFC3490] for domainparts, and the stringprep [RFC3454] profiles
Nodeprep and Resourceprep [RFC3920] for localparts and resourceparts.
5. Security Considerations
5.1. Reuse of PRECIS
The security considerations described in [FRAMEWORK] apply to the
"NameClass" and "FreeClass" base string classes used in this document
for XMPP localparts and resourceparts. The security considerations
described in [RFC5890] apply to internationalized domain names, which
are used here for XMPP domainparts.
5.2. Reuse of Unicode
The security considerations described in [UTR39] apply to the use of
Unicode characters in XMPP addresses.
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5.3. Address Spoofing
There are two forms of address spoofing: forging and mimicking.
5.3.1. 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 negotiation of SASL authentication [RFC4422] as described in
[RFC6120]). 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 authentication
(see [RFC6120]). However, address forging is possible if:
o A poorly implemented server ignores the requirement for stamping
the 'from' address. This would enable any entity that
authenticated with the server to send stanzas from any
localpart@domainpart as long as the domainpart matches the sending
domain of the server.
o An actively malicious server generates stanzas on behalf of any
registered account at the domain or domains hosted at that server.
Therefore, an entity outside the security perimeter of a particular
server cannot reliably distinguish between JIDs of the form
<localpart@domainpart> at that server and thus can authenticate only
the domainpart of such JIDs with any level of assurance. This
specification does not define methods for discovering or
counteracting the kind of poorly implemented or rogue servers just
described. However, the end-to-end authentication or signing of XMPP
stanzas could help to mitigate this risk, since it would require the
rogue server to generate false credentials for signing or encryption
of each stanza, in addition to modifying 'from' addresses.
Furthermore, it is possible for an attacker to forge JIDs at other
domains by means of a DNS poisoning attack if DNS security extensions
[RFC4033] are not used.
5.3.2. Address Mimicking
Address mimicking occurs when an entity provides legitimate
authentication credentials for and sends XML stanzas from an account
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whose JID appears to a human user to be the same as another JID.
Because many characters are visually similar, it is relatively easy
to mimic JIDs in XMPP systems. As one simple example, the localpart
"ju1iet" (using the Arabic numeral one as the third character) might
appear the same as the localpart "juliet" (using lowercase "L" as the
third character).
As explained in [RFC5890], [FRAMEWORK], [UTR36], and [UTR39], there
is no straightforward solution to the problem of visually similar
characters. Furthermore, IDNA and PRECIS technologies do not attempt
to define such a solution. As a result, XMPP domainparts,
localparts, and resourceparts could contain such characters, leading
to security vulnerabilities such as the following:
o A domainpart is always employed as one part of an entity's address
in XMPP. One common usage is as the address of a server or
server-side service, such as a multi-user chat service [XEP-0045].
The security of such services could be compromised based on
different interpretations of the internationalized domainpart; for
example, a user might authorize a malicious entity at a fake
server to view the user's presence information, or a user could
join chatrooms at a fake multi-user chat service.
o 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 chat 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.
o 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 chat 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, two or more
confusable resources could be bound at the same time to the same
account (resulting in inconsistent authorization decisions in an
XMPP application that uses full JIDs), or a user could send a
message to someone other than the intended recipient in a multi-
user chat room.
XMPP services and clients are strongly encouraged to define and
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implement consistent policies regarding the registration, storage,
and presentation of visually similar characters in XMPP systems. In
particular, service providers and software implementers are strongly
encouraged to use the policies recommended in [FRAMEWORK].
6. IANA Considerations
6.1. Use of NameClass
The IANA shall add an entry to the PRECIS Usage Registry for reuse of
the PRECIS NameClass in XMPP, as follows:
Application Protocol: XMPP.
Base Class: NameClass.
Subclassing: Yes. See Section 2.3 of RFC XXXX.
Directionality: If the string contains at least one right-to-left
code point, the entire string is considered to be right-to-left.
Casemapping: Uppercase and titlecase code points are mapped to their
lowercase equivalents.
Normalization: NFC.
Specification: RFC XXXX.
6.2. Use of FreeClass
The IANA shall add an entry to the PRECIS Usage Registry for reuse of
the PRECIS FreeClass in XMPP, as follows:
Application Protocol: XMPP.
Base Class: FreeClass
Subclassing: No.
Directionality: If the string contains at least one right-to-left
code point, the entire string is considered to be right-to-left.
Casemapping: None.
Normalization: NFC.
Specification: RFC XXXX.
7. 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:
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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 [RFC2119]
The feature set specified here provides a basis for interoperability
testing and follows the spirit of a proposal made by Larry Masinter
within the IETF's NEWTRK Working Group in 2005 [INTEROP].
Feature: address-domain-length
Description: Ensure that the domainpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length, and
conforms to the underlying length limits of the DNS.
Section: Section 2.2
Roles: Server MUST, client SHOULD.
Feature: address-domain-prep
Description: Ensure that the domainpart of an XMPP address conforms
to IDNA2008, mapped to lowercase and normalized using NFC.
Section: Section 2.2
Roles: Server MUST, client SHOULD.
Feature: address-localpart-length
Description: Ensure that the localpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length.
Section: Section 2.3
Roles: Server MUST, client SHOULD.
Feature: address-localpart-prep
Description: Ensure that the localpart of an XMPP address conforms
to the "NameClass" base string class from the PRECIS framework,
excluding the eight XMPP prohibited code points (U+0022, U+0026,
U+0027, U+002F, U+003A, U+003C, U+003E, and U+0040), with all code
points mapped to lowercase and normalized using NFC.
Section: Section 2.3
Roles: Server MUST, client SHOULD.
Feature: address-resource-length
Description: Ensure that the resourcepart of an XMPP address is at
least one byte in length and at most 1023 bytes in length.
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Section: Section 2.4
Roles: Server MUST, client SHOULD.
Feature: address-resource-prep
Description: Ensure that the resourcepart of an XMPP address
conforms to the "FreeClass" base string class from the PRECIS
framework, with all code points normalized using NFC.
Section: Section 2.4
Roles: Server MUST, client SHOULD.
8. References
8.1. Normative References
[FRAMEWORK]
Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Handling Internationalized Strings in Protocols",
draft-ietf-precis-framework-02 (work in progress),
March 2012.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010.
[RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, August 2010.
[RFC5892] Faltstrom, P., "The Unicode Code Points and
Internationalized Domain Names for Applications (IDNA)",
RFC 5892, August 2010.
[RFC5893] Alvestrand, H. and C. Karp, "Right-to-Left Scripts for
Internationalized Domain Names for Applications (IDNA)",
RFC 5893, August 2010.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
3.2.0", 2000.
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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/).
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[UTR36] The Unicode Consortium, "Unicode Technical Report #36:
Unicode Security Considerations", 2008,
<http://www.unicode.org/reports/tr36/>.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
8.2. Informative References
[INTEROP] Masinter, L., "Formalizing IETF Interoperability
Reporting", Work in Progress, October 2005.
[MAPPINGS]
Yoneya, Y. and T. NEMOTO, "Mapping characters for PRECIS
classes", draft-yoneya-precis-mappings-01 (work in
progress), February 2012.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
See Section 1 for an explanation of why the normative
reference to an obsoleted specification is needed.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC3921] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence",
RFC 3921, October 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
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RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
Security Layer (SASL)", RFC 4422, June 2006.
[RFC5894] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Background, Explanation, and
Rationale", RFC 5894, August 2010.
[RFC6121] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence",
RFC 6121, March 2011.
[RFC6122] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format", RFC 6122, March 2011.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
September 2011.
[UTR39] The Unicode Consortium, "Unicode Technical Report #39:
Unicode Security Mechanisms", August 2010,
<http://unicode.org/reports/tr39/>.
[XEP-0004]
Eatmon, R., Hildebrand, J., Miller, J., Muldowney, T., and
P. Saint-Andre, "Data Forms", XSF XEP 0004, August 2007.
[XEP-0016]
Millard, P. and P. Saint-Andre, "Privacy Lists", XSF
XEP 0016, February 2007.
[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]
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Saint-Andre, P., "Multi-User Chat", XSF XEP 0045,
July 2008.
[XEP-0048]
Blackman, R., Millard, P., and P. Saint-Andre,
"Bookmarks", XSF XEP 0048, November 2007.
[XEP-0054]
Saint-Andre, P., "vcard-temp", XSF XEP 0054, July 2008.
[XEP-0060]
Millard, P., Saint-Andre, P., and R. Meijer, "Publish-
Subscribe", XSF XEP 0060, July 2010.
[XEP-0065]
Smith, D., Miller, M., Saint-Andre, P., and J. Karneges,
"SOCKS5 Bytestreams", XSF XEP 0065, April in progress,
last updated 2010.
[XEP-0077]
Saint-Andre, P., "In-Band Registration", XSF XEP 0077,
September 2009.
[XEP-0079]
Miller, M. and P. Saint-Andre, "Advanced Message
Processing", XSF XEP 0079, November 2005.
[XEP-0114]
Saint-Andre, P., "Jabber Component Protocol", XSF
XEP 0114, March 2005.
[XEP-0144]
Saint-Andre, P., "Roster Item Exchange", XSF XEP 0144,
August 2005.
[XEP-0165]
Saint-Andre, P., "Best Practices to Discourage JID
Mimicking", XSF XEP 0165, December 2007.
[XEP-0166]
Ludwig, S., Beda, J., Saint-Andre, P., McQueen, R., Egan,
S., and J. Hildebrand, "Jingle", XSF XEP 0166,
December 2009.
[XEP-0191]
Saint-Andre, P., "Simple Communications Blocking", XSF
XEP 0191, February 2007.
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[XEP-0203]
Saint-Andre, P., "Delayed Delivery", XSF XEP 0203,
September 2009.
[XEP-0220]
Miller, J., Saint-Andre, P., and P. Hancke, "Server
Dialback", XSF XEP 0220, March 2010.
[XEP-0292]
Saint-Andre, P. and S. Mizzi, "vCard4 Over XMPP", XSF
XEP 0292, October 2011.
[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>.
[RFC5122] 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. Differences from RFC 6122
Based on consensus derived from working group discussion,
implementation and deployment experience, and formal interoperability
testing, the following substantive modifications were made from RFC
6122.
o Changed domainpart preparation to use IDNA2008 (instead of
IDNA2003).
o Changed localpart preparation to use the PRECIS NameClass (instead
of the Nodeprep profile of Stringprep).
o Changed resourcepart preparation to use the PRECIS FreeClass
(instead of the Resourceprep profile of Stringprep).
o Specified that internationalized labels within domainparts must be
U-labels (instead of should be U-labels).
o Specified that servers must enforce the address formatting rules.
Appendix B. Acknowledgements
Some text in this document was borrowed or adapted from [RFC5890],
[RFC5891], [RFC5894], and [XEP-0165].
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Author's Address
Peter Saint-Andre
Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600
Denver, CO 80202
USA
Phone: +1-303-308-3282
Email: psaintan@cisco.com
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