draft-ietf-xmpp-address-06.txt   draft-ietf-xmpp-address-07.txt 
XMPP P. Saint-Andre XMPP P. Saint-Andre
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track October 25, 2010 Intended status: Standards Track November 17, 2010
Expires: April 28, 2011 Expires: May 21, 2011
Extensible Messaging and Presence Protocol (XMPP): Address Format Extensible Messaging and Presence Protocol (XMPP): Address Format
draft-ietf-xmpp-address-06 draft-ietf-xmpp-address-07
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
skipping to change at page 1, line 32 skipping to change at page 1, line 32
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 28, 2011. This Internet-Draft will expire on May 21, 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
4. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 4
4.1. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 4 2. Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 4
4.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2. Domainpart . . . . . . . . . . . . . . . . . . . . . . . . 6
4.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 7 2.3. Localpart . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Internationalization Considerations . . . . . . . . . . . . . 9 2.4. Resourcepart . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 3. Internationalization Considerations . . . . . . . . . . . . . 9
6.1. Reuse of Stringprep . . . . . . . . . . . . . . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 9 4.1. Reuse of Stringprep . . . . . . . . . . . . . . . . . . . 9
6.3. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9 4.2. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . . 9
6.3.1. Address Forging . . . . . . . . . . . . . . . . . . . 9 4.3. Address Spoofing . . . . . . . . . . . . . . . . . . . . . 9
6.3.2. Address Mimicking . . . . . . . . . . . . . . . . . . 10 4.3.1. Address Forging . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 4.3.2. Address Mimicking . . . . . . . . . . . . . . . . . . 10
7.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 13 5.1. Nodeprep Profile of Stringprep . . . . . . . . . . . . . . 13
8. Conformance Requirements . . . . . . . . . . . . . . . . . . . 13 5.2. Resourceprep Profile of Stringprep . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6. Conformance Requirements . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 16 7.1. Normative References . . . . . . . . . . . . . . . . . . . 15
Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 17 7.2. Informative References . . . . . . . . . . . . . . . . . . 16
A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 17 Appendix A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . 18
A.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 18
A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 18 A.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 18
A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 18 A.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 18
A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 18 A.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 19
A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 18 A.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 19
A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 19 A.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 19
A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 19 A.7. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 20 Appendix B. Resourceprep . . . . . . . . . . . . . . . . . . . . 20
B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 20 B.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 20
B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 20 B.2. Character Repertoire . . . . . . . . . . . . . . . . . . . 21
B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 20 B.3. Mapping . . . . . . . . . . . . . . . . . . . . . . . . . 21
B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 21 B.4. Normalization . . . . . . . . . . . . . . . . . . . . . . 21
B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 21 B.5. Prohibited Output . . . . . . . . . . . . . . . . . . . . 21
B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 21 B.6. Bidirectional Characters . . . . . . . . . . . . . . . . . 21
Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 21 Appendix C. Differences From RFC 3920 . . . . . . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
1.1. Overview
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
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this specification will be superseded as soon as work on a new this specification will be superseded as soon as work on a new
approach to preparation and comparison of internationalized strings approach to preparation and comparison of internationalized strings
has been defined by the PRECIS Working Group and applied to the has been defined by the PRECIS Working Group and applied to the
specific cases of XMPP localparts and resourceparts. In the specific cases of XMPP localparts and resourceparts. In the
meantime, this document normatively references [IDNA2003] and meantime, this document normatively references [IDNA2003] and
[NAMEPREP]; XMPP software implementations are encouraged to begin [NAMEPREP]; XMPP software implementations are encouraged to begin
migrating to IDNA2008 (see [IDNA-PROTO] and related documents) migrating to IDNA2008 (see [IDNA-PROTO] and related documents)
because it is nearly certain that the specification superseding this because it is nearly certain that the specification superseding this
one will re-use IDNA2008. one will re-use IDNA2008.
2. Terminology 1.2. Terminology
Many important terms used in this document are defined in [IDNA2003], Many important terms used in this document are defined in [IDNA2003],
[STRINGPREP], [UNICODE], and [XMPP]. [STRINGPREP], [UNICODE], and [XMPP].
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[KEYWORDS]. [KEYWORDS].
3. Acknowledgements 1.3. Acknowledgements
Thanks to Ben Campbell, Waqas Hussain, Jehan Pages and Florian Zeitz
for their feedback. Thanks also to Richard Barnes for his review on
behalf of the Security Directorate.
The Working Group chairs were Ben Campbell and Joe Hildebrand.
The responsible Area Director was Gonzalo Camarillo.
Some text in this document was borrowed or adapted from [IDNA-DEFS], Some text in this document was borrowed or adapted from [IDNA-DEFS],
[IDNA-PROTO], [IDNA-RATIONALE], and [XEP-0165]. [IDNA-PROTO], [IDNA-RATIONALE], and [XEP-0165].
4. Addresses 2. Addresses
4.1. Fundamentals 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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service) and a specific occupant of such a room could be addressed as service) and a specific occupant of such a room could be addressed as
<room@service/nick> (where "nick" is the occupant's room nickname). <room@service/nick> (where "nick" is the occupant's room nickname).
Many other JID types are possible (e.g., <domainpart/resourcepart> Many other JID types are possible (e.g., <domainpart/resourcepart>
could be a server-side script or service). could be a server-side script or service).
Each allowable portion of a JID (localpart, domainpart, and Each allowable portion of a JID (localpart, domainpart, and
resourcepart) MUST NOT be zero bytes in length and MUST NOT be more resourcepart) MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length, resulting in a maximum total size than 1023 bytes in length, resulting in a maximum total size
(including the '@' and '/' separators) of 3071 bytes. (including the '@' and '/' separators) of 3071 bytes.
An entity's address on an XMPP network MUST be represented as a JID For the purpose of communication over an XMPP network (e.g., in the
(without a URI scheme) and not a [URI] or [IRI] as specified in 'to' or 'from' address of an XMPP stanza), an entity's address MUST
[XMPP-URI]; the latter specification is provided only for be represented as a JID, not as a Uniform Resource Identifier [URI]
identification and interaction outside the context of XMPP itself. or Internationalized Resource Identifier [IRI]. An XMPP URI or IRI
[XMPP-URI] is in essence a JID prepended with 'xmpp:', but the native
addressing format used in XMPP is that of a mere JID without a URI
scheme. [XMPP-URI] is provided only for identification and
interaction outside the context of XMPP itself, for example when
linking to a JID from a web page. See [XMPP-URI] for a description
of the process for securely extracting a JID from an XMPP URI or IRI.
Implementation Note: When dividing a JID into its component parts, Implementation Note: When dividing a JID into its component parts,
an implementation needs to match the separator characters '@' and an implementation needs to match the separator characters '@' and
'/' before applying any transformation algorithms, which might '/' before applying any transformation algorithms, which might
decompose certain Unicode code points to the separator characters decompose certain Unicode code points to the separator characters
(e.g., U+FE6B SMALL COMMERCIAL AT might decompose into U+0040 (e.g., U+FE6B SMALL COMMERCIAL AT might decompose into U+0040
COMMERCIAL AT). COMMERCIAL AT).
4.2. Domainpart 2.2. Domainpart
The DOMAINPART of a JID is that portion after the '@' character (if The DOMAINPART of a JID is that portion after the '@' character (if
any) and before the '/' character (if any); it is the primary any) and before the '/' character (if any); it is the primary
identifier and is the only REQUIRED element of a JID (a mere identifier and is the only REQUIRED element of a JID (a mere
domainpart is a valid JID). Typically a domainpart identifies the domainpart is a valid JID). Typically a domainpart identifies the
"home" server to which clients connect for XML routing and data "home" server to which clients connect for XML routing and data
management functionality. However, it is not necessary for an XMPP management functionality. However, it is not necessary for an XMPP
domainpart to identify an entity that provides core XMPP server domainpart to identify an entity that provides core XMPP server
functionality (e.g., a domainpart can identify an entity such as a functionality (e.g., a domainpart can identify an entity such as a
multi-user chat service, a publish-subscribe service, or a user multi-user chat service, a publish-subscribe service, or a user
directory). directory).
The domainpart for every server or service that will communicate over The domainpart for every XMPP service MUST be a fully qualified
a network SHOULD be a fully qualified domain name or "FQDN" (see domain name ("FQDN"; see [DNS]), IPv4 address, IPv6 address, or
[DNS]); although the domainpart is allowed to be either an Internet unqualifed hostname (i.e., a text label that is resolvable on a local
Protocol (IPv4 or IPv6) address or a text label that is resolvable on network).
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.
Implementation Note: If the domainpart includes a final character Interoperability Note: Domainparts that are IP addresses might not
considered to be a label separator (dot) by [IDNA2003] or [DNS], be accepted by other services for the sake of server-to-server
this character MUST be stripped from the domainpart before the JID communication, and domainparts that are unqualified hostnames
of which it is a part is used for the purpose of routing an XML cannot be used on public networks because they are resolvable only
stanza, comparing against another JID, or constructing an on a local network.
[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 NOT be zero bytes in length and MUST NOT be more A domainpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. than 1023 bytes in length.
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 consisting of a fully qualified domain name MUST be an A domainpart consisting of a fully qualified domain name MUST be an
"internationalized domain name" as defined in [IDNA2003], that is, it "internationalized domain name" as defined in [IDNA2003], that is, it
MUST be "a domain name in which every label is an internationalized MUST be "a domain name in which every label is an internationalized
label" and MUST follow the rules for construction of label" and MUST follow the rules for construction of
internationalized domain names specified in [IDNA2003]. When internationalized domain names specified in [IDNA2003]. When
preparing a text label (consisting of a sequence of UTF-8 encoded preparing a text label (consisting of a sequence of UTF-8 encoded
Unicode code points) for representation as an internationalized label Unicode code points) for representation as an internationalized label
in the process of constructing an XMPP domainpart or comparing two in the process of constructing an XMPP domainpart or comparing two
XMPP domainparts, an application MUST ensure that for each text label XMPP domainparts, an application MUST ensure that for each text label
it is possible to apply without failing the ToASCII operation it is possible to apply without failing the ToASCII operation
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that ACE label to an internationalized label using the ToUnicode that ACE label to an internationalized label using the ToUnicode
operation (see [IDNA2003]) before including the label in an XMPP operation (see [IDNA2003]) before including the label in an XMPP
domainpart that will be communicated over the wire on an XMPP network domainpart that will be communicated over the wire on an XMPP network
(however, instead of converting the label, there are legitimate (however, instead of converting the label, there are legitimate
reasons why an application might instead refuse the input altogether reasons why an application might instead refuse the input altogether
and return an error to the entity that provided the offending data). and return an error to the entity that provided the offending data).
In the terms of IDNA2008 [IDNA-DEFS], the domainpart of a JID is a In the terms of IDNA2008 [IDNA-DEFS], the domainpart of a JID is a
"domain name slot". "domain name slot".
4.3. Localpart 2.3. Localpart
The LOCALPART of a JID is an optional identifier placed before the The LOCALPART of a JID is an optional identifier placed before the
domainpart and separated from the latter by the '@' character. domainpart and separated from the latter by the '@' character.
Typically a localpart uniquely identifies the entity requesting and Typically a localpart uniquely identifies the entity requesting and
using network access provided by a server (i.e., a local account), 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 although it can also represent other kinds of entities (e.g., a chat
room associated with a multi-user chat service). The entity room associated with a multi-user chat service). The entity
represented by an XMPP localpart is addressed within the context of a represented by an XMPP localpart is addressed within the context of a
specific domain. specific domain.
A localpart MUST NOT be zero bytes in length and MUST NOT be more A localpart MUST NOT be zero bytes in length and MUST NOT be more
than 1023 bytes in length. than 1023 bytes in length.
A localpart MUST be formatted such that the Nodeprep profile of A localpart MUST be formatted such that the Nodeprep profile of
[STRINGPREP] can be applied without failing (see Appendix A). Before [STRINGPREP] can be applied without failing (see Appendix A). Before
comparing two localparts, an application MUST first ensure that the comparing two localparts, an application MUST first ensure that the
Nodeprep profile has been applied to each identifier (the profile 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 need not be applied each time a comparison is made, as long as it has
been applied before comparison). been applied before comparison).
4.4. Resourcepart 2.4. Resourcepart
The resourcepart of a JID is an optional identifier placed after the The resourcepart of a JID is an optional identifier placed after the
domainpart and separated from the latter by the '/' character. A domainpart and separated from the latter by the '/' character. A
resourcepart can modify either a <localpart@domainpart> address or a resourcepart can modify either a <localpart@domainpart> address or a
mere <domainpart> address. Typically a resourcepart uniquely mere <domainpart> address. Typically a resourcepart uniquely
identifies a specific connection (e.g., a device or location) or identifies a specific connection (e.g., a device or location) or
object (e.g., an occupant in a multi-user chat room) belonging to the object (e.g., an occupant in a multi-user chat room) belonging to the
entity associated with an XMPP localpart at a local domain. entity associated with an XMPP localpart at a local domain.
When an XMPP address does not include a resourcepart (i.e., when it When an XMPP address does not include a resourcepart (i.e., when it
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associated with the entity "localpart@domain". associated with the entity "localpart@domain".
o The '@' character is allowed in the resourcepart, and is often o The '@' character is allowed in the resourcepart, and is often
used in the "nick" shown in XMPP chatrooms. For example, the JID used in the "nick" shown in XMPP chatrooms. For example, the JID
<room@chat.example.com/user@host> describes an entity who is an <room@chat.example.com/user@host> describes an entity who is an
occupant of the room <room@chat.example.com> with an (asserted) occupant of the room <room@chat.example.com> with an (asserted)
nick of <user@host>. However, chatroom services do not nick of <user@host>. However, chatroom services do not
necessarily check such an asserted nick against the occupant's necessarily check such an asserted nick against the occupant's
real JID. real JID.
5. 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 [XMPP].
6. Security Considerations 4. Security Considerations
6.1. 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.
6.2. Reuse of Unicode 4.2. Reuse of Unicode
The security considerations described in [UNICODE-SEC] apply to the The security considerations described in [UNICODE-SEC] apply to the
use of Unicode characters in XMPP addresses. use of Unicode characters in XMPP addresses.
6.3. Address Spoofing 4.3. Address Spoofing
There are two forms of address spoofing: forging and mimicking. There are two forms of address spoofing: forging and mimicking.
6.3.1. Address Forging 4.3.1. Address Forging
In the context of XMPP technologies, address forging occurs when an In the context of XMPP technologies, address forging occurs when an
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 [XMPP]). However, address forging is possible if:
rogue server could forge JIDs at the sending domain by ignoring the
stamping requirement. Therefore, an entity outside the security o A poorly implemented server ignores the requirement for stamping
perimeter of a particular server cannot reliably distinguish between the 'from' address. This would enable any entity that
bare JIDs of the form <localpart@domainpart> at that server and thus authenticated with the server to send stanzas from any
can authenticate only the domainpart of such JIDs with any level of localpart@domainpart as long as the domainpart matches the sending
assurance. This specification does not define methods for domain of the server.
discovering or counteracting such rogue servers.
o An actively malicious server generates stanzas on behalf of any
registered account.
Therefore, an entity outside the security perimeter of a particular
server cannot reliably distinguish between bare 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 such poorly implemented or rogue servers. 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 in addition to modifying 'from' addresses.
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.
6.3.2. Address Mimicking 4.3.2. 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
whose JID appears to a human user to be the same as another JID. For whose JID appears to a human user to be the same as another JID. For
example, in some XMPP clients the address "ju1iet@example.org" example, in some XMPP clients the address "ju1iet@example.org"
(spelled with the number one as the third character of the localpart) (spelled with the number one as the third character of the localpart)
might appear to be the same as "juliet@example.org (spelled with the might appear to be the same as "juliet@example.org (spelled with the
lower-case version of the letter "L"), especially on casual visual lower-case version of the letter "L"), especially on casual visual
inspection; this phenomenon is sometimes called "typejacking". A inspection; this phenomenon is sometimes called "typejacking". A
more sophisticated example of address mimicking might involve the use more sophisticated example of address mimicking might involve the use
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accounts (localparts) plays a role similar to that of a registry accounts (localparts) plays a role similar to that of a registry
for DNS domain names, such a service SHOULD establish a policy for DNS domain names, such a service SHOULD establish a policy
about the scripts or blocks of characters it will allow in about the scripts or blocks of characters it will allow in
localparts at the service. Such a policy is likely to be localparts at the service. Such a policy is likely to be
informed by the languages and scripts that are used to write informed by the languages and scripts that are used to write
registered account names; in particular, to reduce confusion, the registered account names; in particular, to reduce confusion, the
service MAY forbid registration of XMPP localparts that contain service MAY forbid registration of XMPP localparts that contain
characters from more than one script and to restrict characters from more than one script and to restrict
registrations to characters drawn from a very small number of registrations to characters drawn from a very small number of
scripts (e.g., scripts that are well-understood by the scripts (e.g., scripts that are well-understood by the
administrators of the service). For related considerations in administrators of the service). Such policies are also
the context of domain name registration, refer to Section 4.3 of appropriate for XMPP services that allow temporary or permanent
[IDNA-PROTO] and Section 3.2 of [IDNA-RATIONALE]. Note well that registration of XMPP resourceparts, e.g., during resource binding
methods for enforcing such restrictions are out of scope for this [XMPP] or upon joining an XMPP-based chat room [XEP-0045]. For
document. related considerations in the context of domain name
registration, refer to Section 4.3 of [IDNA-PROTO] and Section
3.2 of [IDNA-RATIONALE]. Note well that methods for enforcing
such restrictions are out of scope for this document.
2. Because every human user of an XMPP client presumably has a 2. Because every human user of an XMPP client presumably has a
preferred language (or, in some cases, a small set of preferred preferred language (or, in some cases, a small set of preferred
languages), an XMPP client SHOULD gather that information either languages), an XMPP client SHOULD gather that information either
explicitly from the user or implicitly via the operating system explicitly from the user or implicitly via the operating system
of the user's device. Furthermore, because most languages are of the user's device. Furthermore, because most languages are
typically represented by a single script (or a small set of typically represented by a single script (or a small set of
scripts) and most scripts are typically contained in one or more scripts) and most scripts are typically contained in one or more
blocks of characters, an XMPP client SHOULD warn the user when blocks of characters, an XMPP client SHOULD warn the user when
presenting a JID that mixes characters from more than one script presenting a JID that mixes characters from more than one script
or block, or that uses characters outside the normal range of the or block, or that uses characters outside the normal range of the
user's preferred language(s). This recommendation is not user's preferred language(s). This recommendation is not
intended to discourage communication across different communities intended to discourage communication across different communities
of language users; instead, it recognizes the existence of such of language users; instead, it recognizes the existence of such
communities and encourages due caution when presenting unfamiliar communities and encourages due caution when presenting unfamiliar
scripts or characters to human users. scripts or characters to human users.
7. IANA Considerations 5. IANA Considerations
The following sections update the registrations provided in The following sections update the registrations provided in
[RFC3920]. [RFC3920].
7.1. Nodeprep Profile of Stringprep 5.1. Nodeprep Profile of Stringprep
The Nodeprep profile of stringprep is defined under Nodeprep The Nodeprep profile of stringprep is defined under Nodeprep
(Appendix A). The IANA has registered Nodeprep in the stringprep (Appendix A). The IANA has registered Nodeprep in the stringprep
profile registry. profile registry.
Name of this profile: Name of this profile:
Nodeprep Nodeprep
RFC in which the profile is defined: RFC in which the profile is defined:
XXXX XXXX
Indicator whether or not this is the newest version of the profile: Indicator whether or not this is the newest version of the profile:
This is the first version of Nodeprep This is the first version of Nodeprep
7.2. Resourceprep Profile of Stringprep 5.2. Resourceprep Profile of Stringprep
The Resourceprep profile of stringprep is defined under Resourceprep The Resourceprep profile of stringprep is defined under Resourceprep
(Appendix B). The IANA has registered Resourceprep in the stringprep (Appendix B). The IANA has registered Resourceprep in the stringprep
profile registry. profile registry.
Name of this profile: Name of this profile:
Resourceprep Resourceprep
RFC in which the profile is defined: RFC in which the profile is defined:
XXXX XXXX
Indicator whether or not this is the newest version of the profile: Indicator whether or not this is the newest version of the profile:
This is the first version of Resourceprep This is the first version of Resourceprep
8. Conformance Requirements 6. Conformance Requirements
This section describes a protocol feature set that summarizes the This section describes a protocol feature set that summarizes the
conformance requirements of this specification. This feature set is conformance requirements of this specification. This feature set is
appropriate for use in software certification, interoperability appropriate for use in software certification, interoperability
testing, and implementation reports. For each feature, this section testing, and implementation reports. For each feature, this section
provides the following information: provides the following information:
o A human-readable name o A human-readable name
o An informational description o An informational description
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formats proposed by Larry Masinter within the IETF's NEWTRK Working formats proposed by Larry Masinter within the IETF's NEWTRK Working
Group in 2005, as captured in [INTEROP]. Although this feature set Group in 2005, as captured in [INTEROP]. Although this feature set
is more detailed than called for by [REPORTS], it provides a suitable is more detailed than called for by [REPORTS], it provides a suitable
basis for the generation of implementation reports to be submitted in basis for the generation of implementation reports to be submitted in
support of advancing this specification from Proposed Standard to support of advancing this specification from Proposed Standard to
Draft Standard in accordance with [PROCESS]. Draft Standard in accordance with [PROCESS].
Feature: address-domain-length Feature: address-domain-length
Description: Ensure that the domainpart of an XMPP address is at Description: Ensure that the domainpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length. least one byte in length and at most 1023 bytes in length.
Section: Section 4.2 Section: Section 2.2
Roles: Both MUST. Roles: Both MUST.
Feature: address-domain-prep Feature: address-domain-prep
Description: Ensure that the domainpart of an XMPP address conforms Description: Ensure that the domainpart of an XMPP address conforms
to the Nameprep profile of Stringprep. to the Nameprep profile of Stringprep.
Section: Section 4.2 Section: Section 2.2
Roles: Client SHOULD, Server MUST. Roles: Client SHOULD, Server MUST.
Feature: address-localpart-length Feature: address-localpart-length
Description: Ensure that the localpart of an XMPP address is at Description: Ensure that the localpart of an XMPP address is at
least one byte in length and at most 1023 bytes in length. least one byte in length and at most 1023 bytes in length.
Section: Section 4.3 Section: Section 2.3
Roles: Both MUST. Roles: Both MUST.
Feature: address-localpart-prep Feature: address-localpart-prep
Description: Ensure that the localpart of an XMPP address conforms Description: Ensure that the localpart of an XMPP address conforms
to the Nodeprep profile of Stringprep. to the Nodeprep profile of Stringprep.
Section: Section 4.3 Section: Section 2.3
Roles: Client SHOULD, Server MUST. Roles: Client SHOULD, Server MUST.
Feature: address-resource-length Feature: address-resource-length
Description: Ensure that the resourcepart of an XMPP address is at Description: Ensure that the resourcepart of an XMPP address is at
least one byte in length and at most 1023 bytes in length. least one byte in length and at most 1023 bytes in length.
Section: Section 4.4 Section: Section 2.4
Roles: Both MUST. Roles: Both MUST.
Feature: address-resource-prep Feature: address-resource-prep
Description: Ensure that the resourcepart of an XMPP address Description: Ensure that the resourcepart of an XMPP address
conforms to the Resourceprep profile of Stringprep. conforms to the Resourceprep profile of Stringprep.
Section: Section 4.2 Section: Section 2.2
Roles: Client SHOULD, Server MUST. Roles: Client SHOULD, Server MUST.
9. References 7. References
9.1. 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 See Section 1 for an explanation of why the normative
skipping to change at page 16, line 6 skipping to change at page 16, line 26
(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 [XMPP] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-18 (work Protocol (XMPP): Core", draft-ietf-xmpp-3920bis-19 (work
in progress), October 2010. in progress), November 2010.
9.2. 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]
Klensin, J., "Internationalized Domain Names for Klensin, J., "Internationalized Domain Names for
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