draft-ietf-xmpp-core-20.txt   draft-ietf-xmpp-core-21.txt 
XMPP Working Group P. Saint-Andre (ed.) XMPP Working Group P. Saint-Andre (ed.)
Internet-Draft Jabber Software Foundation Internet-Draft Jabber Software Foundation
Expires: May 20, 2004 November 20, 2003 Expires: July 6, 2004 January 6, 2004
Extensible Messaging and Presence Protocol (XMPP): Core Extensible Messaging and Presence Protocol (XMPP): Core
draft-ietf-xmpp-core-20 draft-ietf-xmpp-core-21
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
skipping to change at page 1, line 30 skipping to change at page 1, line 30
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on May 20, 2004. This Internet-Draft will expire on July 6, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This memo defines the core features of the Extensible Messaging and This memo defines the core features of the Extensible Messaging and
Presence Protocol (XMPP), a protocol for streaming Extensible Markup Presence Protocol (XMPP), a protocol for streaming Extensible Markup
Language (XML) elements in order to exchange structured information Language (XML) elements in order to exchange structured information
in close to real time between any two network endpoints. While XMPP in close to real time between any two network endpoints. While XMPP
provides a generalized, extensible framework for exchanging XML data, provides a generalized, extensible framework for exchanging XML data,
it is used mainly for the purpose of building instant messaging and it is used mainly for the purpose of building instant messaging and
presence applications that meet the requirements of RFC 2779. presence applications that meet the requirements of RFC 2779.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Generalized Architecture . . . . . . . . . . . . . . . . . . . 4 2. Generalized Architecture . . . . . . . . . . . . . . . . . . . 4
3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . 6 3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . 6
4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . . 26 6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . . 26
7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . . 36 7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . . 36
8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . . 39 8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . . 39
9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 45 9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 46
10. Server Rules for Handling XML Stanzas . . . . . . . . . . . . 54 10. Server Rules for Handling XML Stanzas . . . . . . . . . . . . 55
11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . . 57 11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . . 57
12. Core Compliance Requirements . . . . . . . . . . . . . . . . . 59 12. Core Compliance Requirements . . . . . . . . . . . . . . . . . 60
13. Internationalization Considerations . . . . . . . . . . . . . 61 13. Internationalization Considerations . . . . . . . . . . . . . 61
14. Security Considerations . . . . . . . . . . . . . . . . . . . 61 14. Security Considerations . . . . . . . . . . . . . . . . . . . 61
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 65 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66
Normative References . . . . . . . . . . . . . . . . . . . . . 68 Normative References . . . . . . . . . . . . . . . . . . . . . 69
Informative References . . . . . . . . . . . . . . . . . . . . 70 Informative References . . . . . . . . . . . . . . . . . . . . 71
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 71 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 72
A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . . 73 B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . . 74
C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 75 C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 76
D. Differences Between Core Jabber Protocol and XMPP . . . . . . 82 D. Differences Between Core Jabber Protocol and XMPP . . . . . . 83
E. Revision History . . . . . . . . . . . . . . . . . . . . . . . 84 E. Revision History . . . . . . . . . . . . . . . . . . . . . . . 85
Intellectual Property and Copyright Statements . . . . . . . . 92 Intellectual Property and Copyright Statements . . . . . . . . 94
1. Introduction 1. Introduction
1.1 Overview 1.1 Overview
The Extensible Messaging and Presence Protocol (XMPP) is an open XML The Extensible Messaging and Presence Protocol (XMPP) is an open XML
[XML] protocol for near-real-time messaging, presence, and [XML] protocol for near-real-time messaging, presence, and
request-response services. The basic syntax and semantics were request-response services. The basic syntax and semantics were
developed originally within the Jabber open-source community, mainly developed originally within the Jabber open-source community, mainly
in 1999. In 2002, the XMPP WG was chartered with developing an in 1999. In 2002, the XMPP WG was chartered with developing an
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instant messaging and presence functionality defined in RFC 2779 instant messaging and presence functionality defined in RFC 2779
[IMP-REQS]. [IMP-REQS].
1.2 Terminology 1.2 Terminology
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC "OPTIONAL" in this document are to be interpreted as described in RFC
2119 [TERMS]. 2119 [TERMS].
1.3 Discussion Venue 1.3 Contributors
The authors welcome discussion and comments related to the topics
presented in this document. The preferred forum is the
<xmppwg@jabber.org> mailing list, for which archives and subscription
information are available at <http://www.jabber.org/cgi-bin/mailman/
listinfo/xmppwg/>.
1.4 Intellectual Property Notice
This document is in full compliance with all provisions of Section 10
of RFC 2026. Parts of this specification use the term "jabber" for
identifying namespaces and other protocol syntax. Jabber[tm] is a
registered trademark of Jabber, Inc. Jabber, Inc. grants permission
to the IETF for use of the Jabber trademark in association with this
specification and its successors, if any.
1.5 Contributors
Most of the core aspects of the Extensible Messaging and Presence Most of the core aspects of the Extensible Messaging and Presence
Protocol were developed originally within the Jabber open-source Protocol were developed originally within the Jabber open-source
community in 1999. This community was founded by Jeremie Miller, who community in 1999. This community was founded by Jeremie Miller, who
released source code for the initial version of the jabberd server in released source code for the initial version of the jabberd server in
January 1999. Major early contributors to the base protocol also January 1999. Major early contributors to the base protocol also
included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave
Smith. Work by the XMPP Working Group has concentrated especially on Smith. Work by the XMPP Working Group has concentrated especially on
security and internationalization; in these areas, protocols for the security and internationalization; in these areas, protocols for the
use of TLS and SASL were originally contributed by Rob Norris, and use of TLS and SASL were originally contributed by Rob Norris, and
stringprep profiles were originally contributed by Joe Hildebrand. stringprep profiles were originally contributed by Joe Hildebrand.
The error code syntax was suggested by Lisa Dusseault. The error code syntax was suggested by Lisa Dusseault.
1.6 Acknowledgements 1.4 Acknowledgements
Thanks are due to a number of individuals in addition to the Thanks are due to a number of individuals in addition to the
contributors listed. Although it is difficult to provide a complete contributors listed. Although it is difficult to provide a complete
list, the following individuals were particularly helpful in defining list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo: the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan
Hogg, Craig Kaes, Jacek Konieczny, Alexey Melnikov, Keith Minkler, Hogg, Craig Kaes, Jacek Konieczny, Alexey Melnikov, Keith Minkler,
Julian Missig, Pete Resnick, Marshall Rose, Alexey Shchepin, Julian Missig, Pete Resnick, Marshall Rose, Alexey Shchepin,
Jean-Louis Seguineau, Iain Shigeoka, and David Waite. Thanks also to Jean-Louis Seguineau, Iain Shigeoka, and David Waite. Thanks also to
members of the XMPP Working Group and the IETF community for comments members of the XMPP Working Group and the IETF community for comments
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3. Addressing Scheme 3. Addressing Scheme
3.1 Overview 3.1 Overview
An entity is anything that can be considered a network endpoint An entity is anything that can be considered a network endpoint
(i.e., an ID on the network) and that can communicate using XMPP. (i.e., an ID on the network) and that can communicate using XMPP.
All such entities are uniquely addressable in a form that is All such entities are uniquely addressable in a form that is
consistent with RFC 2396 [URI]. For historical reasons, the address consistent with RFC 2396 [URI]. For historical reasons, the 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
contains a set of ordered elements formed of a domain identifier, contains a set of ordered elements formed of a domain identifier,
node identifier, and resource identifier. The syntax is defined below node identifier, and resource identifier.
using Augmented Backus-Naur Form as defined in RFC 2234 [ABNF], where
the "node", "domain", and "resource" identifiers are as specified in
the following sections:
[ node "@" ] domain [ "/" resource ] The syntax for a JID is defined below using Augmented Backus-Naur
Form as defined in [ABNF]. The IPv4address and IPv6address rules are
defined in Appendix B of [IPv6]; the allowable character sequences
that conform to the node rule are defined by the Nodeprep (Appendix
A) profile of [STRINGPREP] as documented in this memo; the allowable
character sequences that conform to the resource rule are defined by
the Resourceprep (Appendix B) profile of [STRINGPREP] as documented
in this memo; and the sub-domain rule makes reference to the concept
of a domain label as described in [IDNA].
Each allowable portion of a JID (node identifier, domain identifier, jid = [ node "@" ] domain [ "/" resource ]
and resource identifier) MUST NOT be more than 1023 bytes in length, domain = fqdn / address-literal
resulting in a maximum total size (including the '@' and '/' fqdn = (sub-domain 1*("." sub-domain))
separators) of 3071 bytes. sub-domain = ([IDNA] conformant domain label)
address-literal = IPv4address / IPv6address
All JIDs are based on the foregoing structure. The most common use All JIDs are based on the foregoing structure. The most common use
of this structure is to identify an instant messaging user, the of this structure is to identify an instant messaging user, the
server to which the user connects, and the user's active session or server to which the user connects, and the user's connected resource
connection (e.g., a specific client) in the form of <user@host/ (e.g., a specific client) in the form of <user@host/resource>.
resource>. However, node types other than clients are possible; for However, node types other than clients are possible; for example, a
example, a specific chat room offered by a multi-user chat service specific chat room offered by a multi-user chat service could be
could be addressed as <room@service> (where "room" is the name of the addressed as <room@service> (where "room" is the name of the chat
chat room and "service" is the hostname of the multi-user chat room and "service" is the hostname of the multi-user chat service)
service) and a specific occupant of such a room could be addressed as 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., <domain/resource> could be a Many other JID types are possible (e.g., <domain/resource> could be a
server-side script or service). server-side script or service).
3.2 Domain Identifier Each allowable portion of a JID (node identifier, domain identifier,
and resource identifier) MUST NOT be more than 1023 bytes in length,
resulting in a maximum total size (including the '@' and '/'
separators) of 3071 bytes.
3.2 Domain Identifier
The domain identifier is the primary identifier and is the only The domain identifier is the primary identifier and is the only
REQUIRED element of a JID (a mere domain identifier is a valid JID). REQUIRED element of a JID (a mere domain identifier is a valid JID).
It usually represents the network gateway or "primary" server to It usually represents the network gateway or "primary" server to
which other entities connect for XML routing and data management which other entities connect for XML routing and data management
capabilities. However, the entity referenced by a domain identifier capabilities. However, the entity referenced by a domain identifier
is not always a server, and may be a service that is addressed as a is not always a server, and may be a service that is addressed as a
subdomain of a server and that provides functionality above and subdomain of a server and that provides functionality above and
beyond the capabilities of a server (e.g., a multi-user chat service, beyond the capabilities of a server (e.g., a multi-user chat service,
a user directory, or a gateway to a foreign messaging system). a user directory, or a gateway to a foreign messaging system).
The domain identifier for every server or service that will The domain identifier for every server or service that will
communicate over a network SHOULD be a Fully Qualified Domain Name. communicate over a network MAY be an IP address but SHOULD be a fully
A domain identifier MUST be an "internationalized domain name" as qualified domain name (see [DNS]). A domain identifier MUST be an
defined in [IDNA], to which the Nameprep [NAMEPREP] profile of "internationalized domain name" as defined in [IDNA], to which the
stringprep [STRINGPREP] can be applied without failing. Before Nameprep [NAMEPREP] profile of stringprep [STRINGPREP] can be applied
comparing two domain identifiers, a server MUST (and a client SHOULD) without failing. Before comparing two domain identifiers, a server
first apply the Nameprep profile to the labels (as defined in [IDNA]) MUST (and a client SHOULD) first apply the Nameprep profile to the
that make up each identifier. labels (as defined in [IDNA]) that make up each identifier.
3.3 Node Identifier 3.3 Node Identifier
The node identifier is an optional secondary identifier placed before The node identifier is an optional secondary identifier placed before
the domain identifier and separated from the latter by the '@' the domain identifier and separated from the latter by the '@'
character. It usually represents the entity requesting and using character. It usually represents the entity requesting and using
network access provided by the server or gateway (i.e., a client), network access provided by the server or gateway (i.e., a client),
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 a node identifier is addressed within the context of a represented by a node identifier is addressed within the context of a
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The resource identifier is an optional tertiary identifier placed The resource identifier is an optional tertiary identifier placed
after the domain identifier and separated from the latter by the '/' after the domain identifier and separated from the latter by the '/'
character. A resource identifier may modify either a <node@domain> character. A resource identifier may modify either a <node@domain>
or mere <domain> address. It usually represents a specific session, or mere <domain> address. It usually represents a specific session,
connection (e.g., a device or location), or object (e.g., a connection (e.g., a device or location), or object (e.g., a
participant in a multi-user chat room) belonging to the entity participant in a multi-user chat room) belonging to the entity
associated with a node identifier. A resource identifier is opaque associated with a node identifier. A resource identifier is opaque
to both servers and other clients, and is typically defined by a to both servers and other clients, and is typically defined by a
client implementation when it provides the information necessary to client implementation when it provides the information necessary to
complete Resource Binding (Section 7) (although it may be generated complete Resource Binding (Section 7) (although it may be generated
by a server on behalf of a client). An entity MAY maintain multiple by a server on behalf of a client), after which it is referred to as
resources simultaneously, with each resource differentiated by a a "connected resource". An entity MAY maintain multiple connected
distinct resource identifier. resources simultaneously, with each connected resource differentiated
by a distinct resource identifier.
A resource identifier MUST be formatted such that the Resourceprep A resource identifier MUST be formatted such that the Resourceprep
(Appendix B) profile of [STRINGPREP] can be applied to it without (Appendix B) profile of [STRINGPREP] can be applied to it without
failing. Before comparing two resource identifiers, a server MUST failing. Before comparing two resource identifiers, a server MUST
(and a client SHOULD) first apply the Resourceprep profile to each (and a client SHOULD) first apply the Resourceprep profile to each
identifier. identifier.
3.5 Determination of Addresses 3.5 Determination of Addresses
After SASL negotiation (Section 6) and, if appropriate, Resource After SASL negotiation (Section 6) and, if appropriate, Resource
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XML </stream> tag. An XML stream is unidirectional; in order to XML </stream> tag. An XML stream is unidirectional; in order to
enable bidirectional information exchange, the initiating entity enable bidirectional information exchange, the initiating entity
and receiving entity MUST negotiate one stream in each direction and receiving entity MUST negotiate one stream in each direction
(the "initial stream" and the "response stream"), normally over (the "initial stream" and the "response stream"), normally over
the same TCP connection. the same TCP connection.
Definition of XML Stanza: An XML stanza is a discrete semantic unit Definition of XML Stanza: An XML stanza is a discrete semantic unit
of structured information that is sent from one entity to another of structured information that is sent from one entity to another
over an XML stream. An XML stanza exists at the direct child over an XML stream. An XML stanza exists at the direct child
level of the root <stream/> element and is said to be level of the root <stream/> element and is said to be
well-balanced if it matches production [43] content of [XML]). well-balanced if it matches production [43] content of [XML]. The
The start of any XML stanza is denoted unambiguously by the start of any XML stanza is denoted unambiguously by the element
element start tag at depth=1 of the XML stream (e.g., <presence>), start tag at depth=1 of the XML stream (e.g., <presence>), and the
and the end of any XML stanza is denoted unambiguously by the end of any XML stanza is denoted unambiguously by the
corresponding close tag at depth=1 (e.g., </presence>). An XML corresponding close tag at depth=1 (e.g., </presence>). An XML
stanza MAY contain child elements (with accompanying attributes, stanza MAY contain child elements (with accompanying attributes,
elements, and CDATA) as necessary in order to convey the desired elements, and CDATA) as necessary in order to convey the desired
information. The only defined XML stanzas are <message/>, information. The only defined XML stanzas are <message/>,
<presence/>, and <iq/> as defined under XML Stanzas (Section 9); <presence/>, and <iq/> as defined under XML Stanzas (Section 9);
an XML element sent for the purpose of Transport Layer Security an XML element sent for the purpose of Transport Layer Security
(TLS) negotiation (Section 5), Simple Authentication and Security (TLS) negotiation (Section 5), Simple Authentication and Security
Layer (SASL) negotiation (Section 6), or server dialback (Section Layer (SASL) negotiation (Section 6), or server dialback (Section
8) is not considered to be an XML stanza. 8) is not considered to be an XML stanza.
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granting access to the initiating entity. There SHOULD be no granting access to the initiating entity. There SHOULD be no
'from' attribute on the XML stream header sent from the initiating 'from' attribute on the XML stream header sent from the initiating
entity to the receiving entity; however, if a 'from' attribute is entity to the receiving entity; however, if a 'from' attribute is
included, it SHOULD be silently ignored by the receiving entity. included, it SHOULD be silently ignored by the receiving entity.
o id -- The 'id' attribute SHOULD be used only in the XML stream o id -- The 'id' attribute SHOULD be used only in the XML stream
header from the receiving entity to the initiating entity. This header from the receiving entity to the initiating entity. This
attribute is a unique identifier created by the receiving entity attribute is a unique identifier created by the receiving entity
to function as a session key for the initiating entity's streams to function as a session key for the initiating entity's streams
with the receiving entity, and MUST be unique within the receiving with the receiving entity, and MUST be unique within the receiving
application (normally a server). There SHOULD be no 'id' application (normally a server). Note well that the stream ID may
attribute on the XML stream header sent from the initiating entity be security-critical and therefore MUST be both unpredictable and
to the receiving entity; however, if an 'id' attribute is non-repeating. There SHOULD be no 'id' attribute on the XML
included, it SHOULD be silently ignored by the receiving entity. stream header sent from the initiating entity to the receiving
entity; however, if an 'id' attribute is included, it SHOULD be
silently ignored by the receiving entity.
o xml:lang -- An 'xml:lang' attribute (as defined in Section 2.12 of o xml:lang -- An 'xml:lang' attribute (as defined in Section 2.12 of
[XML]) SHOULD be included by the initiating entity on the header [XML]) SHOULD be included by the initiating entity on the header
for the initial stream to specify the default language of any for the initial stream to specify the default language of any
human-readable XML character data it sends over that stream. If human-readable XML character data it sends over that stream. If
the attribute is included, the receiving entity SHOULD remember the attribute is included, the receiving entity SHOULD remember
that value as the default for both the initial stream and the that value as the default for both the initial stream and the
response stream; if the attribute is not included, the receiving response stream; if the attribute is not included, the receiving
entity SHOULD use a configurable default value for both streams, entity SHOULD use a configurable default value for both streams,
which it MUST communicate in the header for the response stream. which it MUST communicate in the header for the response stream.
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| initiating to receiving | receiving to initiating | initiating to receiving | receiving to initiating
---------+---------------------------+----------------------- ---------+---------------------------+-----------------------
to | hostname of receiver | silently ignored to | hostname of receiver | silently ignored
from | silently ignored | hostname of receiver from | silently ignored | hostname of receiver
id | silently ignored | session key id | silently ignored | session key
xml:lang | default language | default language xml:lang | default language | default language
version | signals XMPP 1.0 support | signals XMPP 1.0 support version | signals XMPP 1.0 support | signals XMPP 1.0 support
4.2.1 Version Support 4.2.1 Version Support
The following rules apply to the generation and handling of the The version of XMPP specified herein is "1.0"; in particular, this
'version' attribute: encapsulates the stream-related protocols (Use of TLS (Section 5),
Use of SASL (Section 6), and Stream Errors (Section 4.6)) as well as
1. If the initiating entity complies with the stream-related the semantics of the three defined XML stanza types (<message/>,
protocols defined herein (including Use of TLS (Section 5), Use <presence/>, and <iq/>). The major version number should be
of SASL (Section 6), and Stream Errors (Section 4.6)), it MUST incremented only if the stream and stanza formats or required actions
include the 'version' attribute in the XML stream header it sends have changed so dramatically that an older version entity would not
to the receiving entity, and it MUST set the value of the be able to interoperate with a newer version entity if it simply
'version' attribute to "1.0". ignored the elements and attributes it did not understand and took
the actions specified in the older specification. The minor version
number indicates new capabilities, and MUST be ignored by an entity
with a smaller minor version number, but used for informational
purposes by the node with the larger minor version number. For
example, a minor version number might indicate the ability to process
a newly defined value of the 'type' attribute for message, presence,
or IQ stanzas; the node with the larger minor version number would
simply note that its correspondent would not be able to understand
that value of the 'type' attribute and therefore would not send it.
2. If the initiating entity includes the 'version' attribute set to The following rules apply to the generation and handling by
a value of "1.0" in its stream header and the receiving entity implementations of the 'version' attribute within stream headers:
supports XMPP 1.0, the receiving entity MUST reciprocate by
including the 'version' attribute set to a value of "1.0" in its
stream header response.
3. If the initiating entity does not include the 'version' attribute 1. The initiating entity MUST set the value of the 'version'
in its stream header, the receiving entity still SHOULD include attribute on the initial stream header to the highest version
the 'version' attribute set to a value of "1.0" in its stream number it supports (e.g., if the highest version number it
header response. supports is that defined in this specification, it MUST set the
value to "1.0").
4. If the initiating entity includes the 'version' attribute set to 2. The receiving entity MUST set the value of the 'version'
a value other than "1.0", the receiving entity SHOULD include the attribute on the response stream header to either the value
'version' attribute set to a value of "1.0" in its stream header supplied by the initiating entity or highest version number
response, but MAY at its discretion generate an supported by the receiving entity, whichever is lower. The
<unsupported-version/> stream error and terminate the XML stream receiving entity MUST perform a numeric comparison, not a string
and underlying TCP connection. match.
5. If the receiving entity includes the 'version' attribute set to a 3. If the version number included in the response stream header is
value other than "1.0" in its stream header response, the at least one major version lower than the version number included
in the initial stream header and newer version entities cannot
interoperate with older version entities as described above, the
initiating entity SHOULD generate an <unsupported-version/> initiating entity SHOULD generate an <unsupported-version/>
stream error and terminate the XML stream and underlying TCP stream error and terminate the XML stream and underlying TCP
connection. connection.
4. If either entity receives a stream header with no 'version'
attribute, the entity MUST consider the version supported by the
other entity to be "0.0" and SHOULD NOT include a 'version'
attribute in the stream header it sends in reply.
4.3 Namespace Declarations 4.3 Namespace Declarations
The stream element MUST possess both a streams namespace declaration The stream element MUST possess both a streams namespace declaration
and a default namespace declaration (as "namespace declaration" is and a default namespace declaration (as "namespace declaration" is
defined in the XML namespaces specification [XML-NAMES]). For defined in the XML namespaces specification [XML-NAMES]). For
detailed information regarding the streams namespace and default detailed information regarding the streams namespace and default
namespace, see Namespace Names and Prefixes (Section 11.2). namespace, see Namespace Names and Prefixes (Section 11.2).
4.4 Stream Features 4.4 Stream Features
skipping to change at page 15, line 44 skipping to change at page 1, line 694
o <improper-addressing/> -- a stanza sent between two servers lacks o <improper-addressing/> -- a stanza sent between two servers lacks
a 'to' or 'from' attribute (or the attribute has no value). a 'to' or 'from' attribute (or the attribute has no value).
o <internal-server-error/> -- the server has experienced a o <internal-server-error/> -- the server has experienced a
misconfiguration or an otherwise-undefined internal error that misconfiguration or an otherwise-undefined internal error that
prevents it from servicing the stream. prevents it from servicing the stream.
o <invalid-from/> -- the JID or hostname provided in a 'from' o <invalid-from/> -- the JID or hostname provided in a 'from'
address does not match an authorized JID or validated domain address does not match an authorized JID or validated domain
negotiated between servers via SASL or dialback, or between a negotiated between servers via SASL or dialback, or between a
client and a server via authentication and resource authorization. client and a server via authentication and resource binding.
o <invalid-id/> -- the stream ID or dialback ID is invalid or does o <invalid-id/> -- the stream ID or dialback ID is invalid or does
not match an ID previously provided. not match an ID previously provided.
o <invalid-namespace/> -- the streams namespace name is something o <invalid-namespace/> -- the streams namespace name is something
other than "http://etherx.jabber.org/streams" or the dialback other than "http://etherx.jabber.org/streams" or the dialback
namespace name is something other than "jabber:server:dialback" namespace name is something other than "jabber:server:dialback"
(see XML Namespace Names and Prefixes (Section 11.2)). (see XML Namespace Names and Prefixes (Section 11.2)).
o <invalid-xml/> -- the entity has sent invalid XML over the stream o <invalid-xml/> -- the entity has sent invalid XML over the stream
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the stream has been authenticated, or otherwise is not authorized the stream has been authenticated, or otherwise is not authorized
to perform an action related to stream negotiation; the receiving to perform an action related to stream negotiation; the receiving
entity MUST NOT process the offending stanza before sending the entity MUST NOT process the offending stanza before sending the
stream error. stream error.
o <policy-violation/> -- the entity has violated some local service o <policy-violation/> -- the entity has violated some local service
policy; the server MAY choose to specify the policy in the <text/> policy; the server MAY choose to specify the policy in the <text/>
element. element.
o <remote-connection-failed/> -- the server is unable to properly o <remote-connection-failed/> -- the server is unable to properly
connect to a remote resource that is required for authentication connect to a remote entity that is required for authentication or
or authorization. authorization.
o <resource-constraint/> -- the server lacks the system resources o <resource-constraint/> -- the server lacks the system resources
necessary to service the stream. necessary to service the stream.
o <restricted-xml/> -- the entity has attempted to send restricted o <restricted-xml/> -- the entity has attempted to send restricted
XML features such as a comment, processing instruction, DTD, XML features such as a comment, processing instruction, DTD,
entity reference, or unescaped character (see Restrictions entity reference, or unescaped character (see Restrictions
(Section 11.1)). (Section 11.1)).
o <see-other-host/> -- the server will not provide service to the o <see-other-host/> -- the server will not provide service to the
initiating entity but is redirecting traffic to another host; the initiating entity but is redirecting traffic to another host; the
server SHOULD specify the alternate hostname or IP address in the server SHOULD specify the alternate hostname or IP address (which
CDATA of the <see-other-host/> element. MUST be a valid domain identifier) in the CDATA of the
<see-other-host/> element.
o <system-shutdown/> -- the server is being shut down and all active o <system-shutdown/> -- the server is being shut down and all active
streams are being closed. streams are being closed.
o <undefined-condition/> -- the error condition is not one of those o <undefined-condition/> -- the error condition is not one of those
defined by the other conditions in this list; this error condition defined by the other conditions in this list; this error condition
SHOULD be used only in conjunction with an application-specific SHOULD be used only in conjunction with an application-specific
condition. condition.
o <unsupported-encoding/> -- the initiating entity has encoded the o <unsupported-encoding/> -- the initiating entity has encoded the
skipping to change at page 19, line 27 skipping to change at page 1, line 868
The following rules apply: The following rules apply:
1. An initiating entity that complies with this specification MUST 1. An initiating entity that complies with this specification MUST
include the 'version' attribute set to a value of "1.0" in the include the 'version' attribute set to a value of "1.0" in the
initial stream header. initial stream header.
2. If the TLS negotiation occurs between two servers, 2. If the TLS negotiation occurs between two servers,
communications MUST NOT proceed until the Domain Name System communications MUST NOT proceed until the Domain Name System
(DNS) hostnames asserted by the servers have been resolved (see (DNS) hostnames asserted by the servers have been resolved (see
Server-to-Server Communications (Section 14.3)). Server-to-Server Communications (Section 14.4)).
3. When a receiving entity that complies with this specification 3. When a receiving entity that complies with this specification
receives an initial stream header that includes the 'version' receives an initial stream header that includes the 'version'
attribute set to a value of "1.0", after sending a stream header attribute set to a value of "1.0", after sending a stream header
in reply (including the version flag) it MUST include a in reply (including the version flag) it MUST include a
<starttls/> element (qualified by the <starttls/> element (qualified by the
'urn:ietf:params:xml:ns:xmpp-tls' namespace) along with the list 'urn:ietf:params:xml:ns:xmpp-tls' namespace) along with the list
of other stream features it supports. of other stream features it supports.
4. If the initiating entity chooses to use TLS, TLS negotiation 4. If the initiating entity chooses to use TLS, TLS negotiation
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ensure proper security layer byte precision. ensure proper security layer byte precision.
6. The receiving entity MUST consider the TLS negotiation to have 6. The receiving entity MUST consider the TLS negotiation to have
begun immediately after sending the closing ">" character of the begun immediately after sending the closing ">" character of the
<proceed/> element. The initiating entity MUST consider the TLS <proceed/> element. The initiating entity MUST consider the TLS
negotiation to have begun immediately after receiving the negotiation to have begun immediately after receiving the
closing ">" character of the <proceed/> element from the closing ">" character of the <proceed/> element from the
receiving entity. receiving entity.
7. The initiating entity MUST validate the certificate presented by 7. The initiating entity MUST validate the certificate presented by
the receiving entity; there are two cases: the receiving entity; see Certificate Validation (Section 14.2)
regarding certificate validation procedures.
8.
Case 1 -- The initiating entity has been configured with a set
of trusted root certificates: Normal certificate validation
processing is appropriate, and SHOULD follow the rules
defined for HTTP over TLS [HTTP-TLS]. The trusted roots may
be either a well-known public set or a manually configured
Root CA (e.g., an organization's own Certificate Authority or
a self-signed Root CA for the service as defined under High
Security (Section 14.1)). This case is RECOMMENDED.
Case 2 -- The initiating entity has been configured with the 8. Certificates MUST be checked against the hostname as provided by
receiving entity's self-signed service certificate: Simple the initiating entity (e.g., a user), not the hostname as
comparison of public keys is appropriate. This case is NOT resolved via the Domain Name System; e.g., if the user or
RECOMMENDED (see High Security (Section 14.1) for details). certificate specifies a hostname of "example.com" but a DNS SRV
[SRV] lookup returned "im.example.com", the certificate MUST be
checked as "example.com". If a JID is represented in a
certificate, it SHOULD be encoded using the otherName choice of
the subjectAltName type along with a type-id of "xmpp" (as these
terms are profiled in [X509]).
9. If the above methods fail, the certificate SHOULD be presented 9. Certificates MUST be checked against the hostname as provided by
to a human (e.g., an end user or server administrator) for the initiating entity (e.g., a user), not the hostname as
approval; if presented, the receiver MUST deliver the entire resolved via the Domain Name System; e.g., if the user or
certificate chain to the human, who SHOULD be given the option certificate specifies a hostname of "example.com" but a DNS SRV
to store the Root CA certificate (not the service or End Entity [SRV] lookup returned "im.example.com", the certificate MUST be
certificate) and to not be queried again regarding acceptance of checked as "example.com". If a JID is represented in a
the certificate for some reasonable period of time. Note well certificate, it SHOULD be encoded using the otherName choice of
that certificates MUST be checked against the hostname as the subjectAltName type along with a type-id of "xmpp" (as these
provided by the initiating entity (e.g., a user), not the terms are profiled in [X509]).
hostname as resolved via the Domain Name System; e.g., if a user
typed "example.com" but a DNS SRV [SRV] lookup returned
"im.example.com", the certificate MUST be checked as
"example.com".
10. If the TLS negotiation is successful, the receiving entity MUST 10. If the TLS negotiation is successful, the receiving entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
initiating entity before TLS takes effect. initiating entity before TLS takes effect.
11. If the TLS negotiation is successful, the initiating entity MUST 11. If the TLS negotiation is successful, the initiating entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
receiving entity before TLS takes effect. receiving entity before TLS takes effect.
12. If the TLS negotiation is successful, the receiving entity MUST 12. If the TLS negotiation is successful, the receiving entity MUST
skipping to change at page 21, line 17 skipping to change at page 1, line 944
with the other stream features that are offered when the stream with the other stream features that are offered when the stream
is restarted. is restarted.
13. If the TLS negotiation is successful, the initiating entity MUST 13. If the TLS negotiation is successful, the initiating entity MUST
continue with SASL negotiation. continue with SASL negotiation.
14. If the TLS negotiation results in failure, the receiving entity 14. If the TLS negotiation results in failure, the receiving entity
MUST terminate both the XML stream and the underlying TCP MUST terminate both the XML stream and the underlying TCP
connection. connection.
15. See Mandatory-to-Implement Technologies (Section 14.6) regarding 15. See Mandatory-to-Implement Technologies (Section 14.7) regarding
mechanisms that MUST be supported. mechanisms that MUST be supported.
5.2 Narrative 5.2 Narrative
When an initiating entity secures a stream with a receiving entity, When an initiating entity secures a stream with a receiving entity,
the steps involved are as follows: the steps involved are as follows:
1. The initiating entity opens a TCP connection and initiates the 1. The initiating entity opens a TCP connection and initiates the
stream by sending the opening XML stream header to the receiving stream by sending the opening XML stream header to the receiving
entity, including the 'version' attribute set to a value of entity, including the 'version' attribute set to a value of
skipping to change at page 26, line 22 skipping to change at page 1, line 1188
(SASL) protocol [SASL]. SASL provides a generalized method for (SASL) protocol [SASL]. SASL provides a generalized method for
adding authentication support to connection-based protocols, and XMPP adding authentication support to connection-based protocols, and XMPP
uses a generic XML namespace profile for SASL that conforms to the uses a generic XML namespace profile for SASL that conforms to the
profiling requirements of [SASL]. profiling requirements of [SASL].
The following rules apply: The following rules apply:
1. If the SASL negotiation occurs between two servers, 1. If the SASL negotiation occurs between two servers,
communications MUST NOT proceed until the Domain Name System communications MUST NOT proceed until the Domain Name System
(DNS) hostnames asserted by the servers have been resolved (see (DNS) hostnames asserted by the servers have been resolved (see
Server-to-Server Communications (Section 14.3)). Server-to-Server Communications (Section 14.4)).
2. If the initiating entity is capable of SASL negotiation, it MUST 2. If the initiating entity is capable of SASL negotiation, it MUST
include the 'version' attribute set to a value of "1.0" in the include the 'version' attribute set to a value of "1.0" in the
initial stream header. initial stream header.
3. If the receiving entity is capable of SASL negotiation, it MUST 3. If the receiving entity is capable of SASL negotiation, it MUST
send one or more authentication mechanisms within a <mechanisms/ send one or more authentication mechanisms within a <mechanisms/
> element qualified by the 'urn:ietf:params:xml:ns:xmpp-sasl' > element qualified by the 'urn:ietf:params:xml:ns:xmpp-sasl'
namespace in reply to the opening stream tag received from the namespace in reply to the opening stream tag received from the
initiating entity (if the opening stream tag included the initiating entity (if the opening stream tag included the
skipping to change at page 27, line 32 skipping to change at page 1, line 1246
8. Upon successful SASL negotiation that involves negotiation of a 8. Upon successful SASL negotiation that involves negotiation of a
security layer, the receiving entity MUST discard any knowledge security layer, the receiving entity MUST discard any knowledge
obtained from the initiating entity which was not obtained from obtained from the initiating entity which was not obtained from
the SASL negotiation itself. the SASL negotiation itself.
9. Upon successful SASL negotiation that involves negotiation of a 9. Upon successful SASL negotiation that involves negotiation of a
security layer, the initiating entity MUST discard any knowledge security layer, the initiating entity MUST discard any knowledge
obtained from the receiving entity which was not obtained from obtained from the receiving entity which was not obtained from
the SASL negotiation itself. the SASL negotiation itself.
10. See Mandatory-to-Implement Technologies (Section 14.6) regarding 10. See Mandatory-to-Implement Technologies (Section 14.7) regarding
mechanisms that MUST be supported. mechanisms that MUST be supported.
6.2 Narrative 6.2 Narrative
When an initiating entity authenticates with a receiving entity, the When an initiating entity authenticates with a receiving entity, the
steps involved are as follows: steps involved are as follows:
1. The initiating entity requests SASL authentication by including 1. The initiating entity requests SASL authentication by including
the 'version' attribute in the opening XML stream header sent to the 'version' attribute in the opening XML stream header sent to
the receiving entity, with the value set to "1.0". the receiving entity, with the value set to "1.0".
skipping to change at page 34, line 49 skipping to change at page 1, line 1594
</stream:features> </stream:features>
Step 4: Server1 selects an authentication mechanism: Step 4: Server1 selects an authentication mechanism:
<auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' <auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
mechanism='DIGEST-MD5'/> mechanism='DIGEST-MD5'/>
Step 5: Server2 sends a [BASE64] encoded challenge to Server1: Step 5: Server2 sends a [BASE64] encoded challenge to Server1:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
dXNlcm5hbWU9InNvbWVkb21haW4iLHJlYWxtPSJzb21lcmVhbG0iLG5vbmNl dXNlcm5hbWU9ImV4YW1wbGUuY29tIixyZWFsbT0ic29tZXJlYWxtIixub25j
PSJPQTZNRzl0RVFHbTJoaCIscW9wPSJhdXRoIixjaGFyc2V0PXV0Zi04LGFs ZT0iT0E2TUc5dEVRR20yaGgiLHFvcD0iYXV0aCIsY2hhcnNldD11dGYtOCxh
Z29yaXRobT1tZDUtc2Vzcwo= bGdvcml0aG09bWQ1LXNlc3MK
</challenge> </challenge>
The decoded challenge is: The decoded challenge is:
username="somedomain",realm="somerealm",\ username="example.com",realm="somerealm",\
nonce="OA6MG9tEQGm2hh",qop="auth",\ nonce="OA6MG9tEQGm2hh",qop="auth",\
charset=utf-8,algorithm=md5-sess charset=utf-8,algorithm=md5-sess
Step 5 (alt): Server2 returns error to Server1: Step 5 (alt): Server2 returns error to Server1:
<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<incorrect-encoding/> <incorrect-encoding/>
</failure> </failure>
</stream:stream> </stream:stream>
Step 6: Server1 sends a [BASE64] encoded response to the challenge: Step 6: Server1 sends a [BASE64] encoded response to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
dXNlcm5hbWU9InNvbWVkb21haW4iLHJlYWxtPSJzb21lcmVhbG0iLG5vbmNl dXNlcm5hbWU9ImV4YW1wbGUuY29tIixyZWFsbT0ic29tZXJlYWxtIixub25j
PSJPQTZNRzl0RVFHbTJoaCIsY25vbmNlPSJPQTZNSFhoNlZxVHJSayIsbmM9 ZT0iT0E2TUc5dEVRR20yaGgiLGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLG5j
MDAwMDAwMDEscW9wPWF1dGgsZGlnZXN0LXVyaT0ieG1wcC9leGFtcGxlLmNv PTAwMDAwMDAxLHFvcD1hdXRoLGRpZ2VzdC11cmk9InhtcHAvZXhhbXBsZS5j
bSIscmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcs b20iLHJlc3BvbnNlPWQzODhkYWQ5MGQ0YmJkNzYwYTE1MjMyMWYyMTQzYWY3
Y2hhcnNldD11dGYtOAo= LGNoYXJzZXQ9dXRmLTgK
</response> </response>
The decoded response is: The decoded response is:
username="somedomain",realm="somerealm",\ username="example.com",realm="somerealm",\
nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk",\ nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk",\
nc=00000001,qop=auth,digest-uri="xmpp/example.com",\ nc=00000001,qop=auth,digest-uri="xmpp/example.com",\
response=d388dad90d4bbd760a152321f2143af7,charset=utf-8 response=d388dad90d4bbd760a152321f2143af7,charset=utf-8
Step 7: Server2 sends another [BASE64] encoded challenge to Server1: Step 7: Server2 sends another [BASE64] encoded challenge to Server1:
<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZAo= cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZAo=
</challenge> </challenge>
skipping to change at page 38, line 18 skipping to change at page 1, line 1755
<iq type='set' id='bind_2'> <iq type='set' id='bind_2'>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'> <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<resource>someresource</resource> <resource>someresource</resource>
</bind> </bind>
</iq> </iq>
Once the server has generated a resource identifier for the client or Once the server has generated a resource identifier for the client or
accepted the resource identifier provided by the client, it MUST accepted the resource identifier provided by the client, it MUST
return an IQ stanza of type "result" to the client, which MUST return an IQ stanza of type "result" to the client, which MUST
include a <jid/> child element that specifies the full JID for the include a <jid/> child element that specifies the full JID for the
client as determined by the server: connected resource as determined by the server:
Server informs client of successful resource binding: Server informs client of successful resource binding:
<iq type='result' id='bind_2'> <iq type='result' id='bind_2'>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'> <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<jid>somenode@somedomain/someresource</jid> <jid>somenode@example.com/someresource</jid>
</bind> </bind>
</iq> </iq>
A server is NOT REQUIRED to accept the resource identifier provided A server is NOT REQUIRED to accept the resource identifier provided
by the client, and MAY override it with a resource identifier that by the client, and MAY override it with a resource identifier that
the server generates; in this case, the server SHOULD NOT return a the server generates; in this case, the server SHOULD NOT return a
stanza error (e.g., <forbidden/>) to the client but instead SHOULD stanza error (e.g., <forbidden/>) to the client but instead SHOULD
communicate the generated resource identifier to the client in the IQ communicate the generated resource identifier to the client in the IQ
result as shown above. result as shown above.
When a client supplies a resource identifier, the following stanza When a client supplies a resource identifier, the following stanza
error conditions are possible (see Stanza Errors (Section 9.3)): error conditions are possible (see Stanza Errors (Section 9.3)):
o The provided resource identifier cannot be processed by the server o The provided resource identifier cannot be processed by the server
in accordance with Resourceprep (Appendix B). in accordance with Resourceprep (Appendix B).
o The client is not allowed to bind a resource to the stream (e.g., o The client is not allowed to bind a resource to the stream (e.g.,
because the client has reached a limit on the number of bound because the client has reached a limit on the number of connected
resources allowed). resources allowed).
o The provided resource identifier is already in use but the server o The provided resource identifier is already in use but the server
does not allow binding of multiple resources with the same does not allow binding of multiple connected resources with the
identifier. same identifier.
The protocol for these error conditions is shown below. The protocol for these error conditions is shown below.
Resource identifier cannot be processed: Resource identifier cannot be processed:
<iq type='error' id='bind_2'> <iq type='error' id='bind_2'>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'> <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<resource>someresource</resource> <resource>someresource</resource>
</bind> </bind>
<error type='modify'> <error type='modify'>
skipping to change at page 39, line 43 skipping to change at page 1, line 1828
</error> </error>
</iq> </iq>
8. Server Dialback 8. Server Dialback
8.1 Overview 8.1 Overview
The Jabber protocols from which XMPP was adapted include a "server The Jabber protocols from which XMPP was adapted include a "server
dialback" method for protecting against domain spoofing, thus making dialback" method for protecting against domain spoofing, thus making
it more difficult to spoof XML stanzas (see Server-to-Server it more difficult to spoof XML stanzas (see Server-to-Server
Communications (Section 14.3) regarding this method's security Communications (Section 14.4) regarding this method's security
characteristics). Server dialback also makes it easier to deploy characteristics). Server dialback also makes it easier to deploy
systems in which outbound messages and inbound messages are handled systems in which outbound messages and inbound messages are handled
by different machines for the same domain. The server dialback by different machines for the same domain. Server dialback is not a
method is made possible by the existence of the Domain Name System security mechanism, and domains requiring robust security SHOULD use
(DNS), since one server can (normally) discover the authoritative TLS and SASL; see Server-to-Server Communications (Section 14.4) for
server for a given domain. details.
Because dialback depends on DNS, inter-domain communications MUST NOT The server dialback method is made possible by the existence of the
proceed until the Domain Name System (DNS) hostnames asserted by the Domain Name System (DNS), since one server can (normally) discover
servers have been resolved (see Server-to-Server Communications the authoritative server for a given domain. Because dialback depends
(Section 14.3)). on DNS, inter-domain communications MUST NOT proceed until the Domain
Name System (DNS) hostnames asserted by the servers have been
resolved (see Server-to-Server Communications (Section 14.4)).
The method for generating and verifying the keys used in server The method for generating and verifying the keys used in server
dialback MUST take into account the hostnames being used, the random dialback MUST take into account the hostnames being used, the stream
ID generated for the stream, and a secret known by the authoritative ID generated by the receiving server, and a secret known by the
server's network. authoritative server's network. The stream ID is security-critical in
server dialback and therefore MUST be both unpredictable and
non-repeating.
Any error that occurs during dialback negotiation MUST be considered Any error that occurs during dialback negotiation MUST be considered
a stream error, resulting in termination of the stream and of the a stream error, resulting in termination of the stream and of the
underlying TCP connection. The possible error conditions are underlying TCP connection. The possible error conditions are
specified in the protocol description below. specified in the protocol description below.
The following terminology applies: The following terminology applies:
o Originating Server -- the server that is attempting to establish a o Originating Server -- the server that is attempting to establish a
connection between two domains. connection between two domains.
skipping to change at page 46, line 42 skipping to change at page 1, line 2165
9.1.2 from 9.1.2 from
The 'from' attribute specifies the JID of the sender. The 'from' attribute specifies the JID of the sender.
When a server receives an XML stanza within the context of an When a server receives an XML stanza within the context of an
authenticated stream qualified by the 'jabber:client' namespace, it authenticated stream qualified by the 'jabber:client' namespace, it
MUST do one of the following: MUST do one of the following:
1. validate that the value of the 'from' attribute provided by the 1. validate that the value of the 'from' attribute provided by the
client is that of an authorized resource for the associated client is that of a connected resource for the associated entity
entity
2. add a 'from' address to the stanza whose value is the full JID 2. add a 'from' address to the stanza whose value is the full JID
(<node@domain/resource>) determined by the server for the (<node@domain/resource>) determined by the server for the
connected resource that generated the stanza (see Determination connected resource that generated the stanza (see Determination
of Addresses (Section 3.5)) of Addresses (Section 3.5))
If a client attempts to send an XML stanza for which the value of the If a client attempts to send an XML stanza for which the value of the
'from' attribute does not match one of the connected resources for 'from' attribute does not match one of the connected resources for
that entity, the server SHOULD return an <invalid-from/> stream error that entity, the server SHOULD return an <invalid-from/> stream error
to the client. If a client attempts to send an XML stanza over a to the client. If a client attempts to send an XML stanza over a
stream that is not yet authenticated, the server SHOULD return a stream that is not yet authenticated, the server SHOULD return a
<not-authorized/> stream error to the client. If generated, both of <not-authorized/> stream error to the client. If generated, both of
these conditions MUST result in closing of the stream and termination these conditions MUST result in closing of the stream and termination
of the underlying TCP connection; this helps to prevent a denial of of the underlying TCP connection; this helps to prevent a denial of
service attack launched from a rogue client. service attack launched from a rogue client.
When a server generates a stanza from the server itself for delivery
to a connected client (e.g., in the context of data storage services
provided by the server on behalf of the client), the stanza MUST
either (1) not include a 'from' attribute or (2) include a 'from'
attribute whose value is the account's bare JID (<node@domain>) or
client's full JID (<node@domain/resource>). A server MUST NOT send
to the client a stanza without a 'from' attribute if the stanza was
not generated by the server itself. When a client receives a stanza
that does not include a 'from' attribute, it MUST assume that the
stanza is from the server to which the client is connected.
In the 'jabber:server' namespace, a stanza MUST possess a 'from' In the 'jabber:server' namespace, a stanza MUST possess a 'from'
attribute; if a server receives a stanza that does not meet this attribute; if a server receives a stanza that does not meet this
restriction, it MUST generate an <improper-addressing/> stream error restriction, it MUST generate an <improper-addressing/> stream error
condition. Furthermore, the domain identifier portion of the JID condition. Furthermore, the domain identifier portion of the JID
contained in the 'from' attribute MUST match the hostname (or any contained in the 'from' attribute MUST match the hostname (or any
validated domain) of the sending server as communicated in the SASL validated domain) of the sending server as communicated in the SASL
negotiation or dialback negotiation; if a server receives a stanza negotiation or dialback negotiation; if a server receives a stanza
that does not meet this restriction, it MUST generate an that does not meet this restriction, it MUST generate an
<invalid-from/> stream error condition. Both of these conditions <invalid-from/> stream error condition. Both of these conditions
MUST result in closing of the stream and termination of the MUST result in closing of the stream and termination of the
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7. An IQ stanza of type "result" MUST include zero or one child 7. An IQ stanza of type "result" MUST include zero or one child
elements. elements.
8. An IQ stanza of type "error" SHOULD include the child element 8. An IQ stanza of type "error" SHOULD include the child element
contained in the associated "get" or "set" and MUST include an contained in the associated "get" or "set" and MUST include an
<error/> child; for details, see Stanza Errors (Section 9.3). <error/> child; for details, see Stanza Errors (Section 9.3).
9.3 Stanza Errors 9.3 Stanza Errors
Stanza-related errors are handled in a manner similar to stream Stanza-related errors are handled in a manner similar to stream
errors (Section 4.6). However, stanza errors are not unrecoverable, errors (Section 4.6). However, unlike stream errors, stanza errors
as stream errors are; therefore error stanzas include hints regarding are recoverable; therefore error stanzas include hints regarding
actions that the original sender can take in order to remedy the actions that the original sender can take in order to remedy the
error. error.
9.3.1 Rules 9.3.1 Rules
The following rules apply to stanza-related errors: The following rules apply to stanza-related errors:
o The receiving or processing entity that detects an error condition o The receiving or processing entity that detects an error condition
in relation to a stanza MUST return to the sending entity a stanza in relation to a stanza MUST return to the sending entity a stanza
of the same kind (message, presence, or IQ) whose 'type' attribute of the same kind (message, presence, or IQ) whose 'type' attribute
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The <text/> element is OPTIONAL. If included, it SHOULD be used only The <text/> element is OPTIONAL. If included, it SHOULD be used only
to provide descriptive or diagnostic information that supplements the to provide descriptive or diagnostic information that supplements the
meaning of a defined condition or application-specific condition. It meaning of a defined condition or application-specific condition. It
SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be interpreted programmatically by an application. It
SHOULD NOT be used as the error message presented to a user, but MAY SHOULD NOT be used as the error message presented to a user, but MAY
be shown in addition to the error message associated with the be shown in addition to the error message associated with the
included condition element (or elements). included condition element (or elements).
Finally, to maintain backward compatibility, the schema (specified in Finally, to maintain backward compatibility, the schema (specified in
[XMPP-IM]) allows the optional inclusion of a 'code' attribute on the [XMPP-IM]) allows the optional inclusion of a 'code' attribute on the
<error/&amp;gr; element. <error/&gt; element.
9.3.3 Defined Conditions 9.3.3 Defined Conditions
The following stanza-related error conditions are defined for use in The following stanza-related error conditions are defined for use in
stanza errors. stanza errors.
o <bad-request/> -- the sender has sent XML that is malformed or o <bad-request/> -- the sender has sent XML that is malformed or
that cannot be processed (e.g., an IQ stanza that includes an that cannot be processed (e.g., an IQ stanza that includes an
unrecognized value of the 'type' attribute); the associated error unrecognized value of the 'type' attribute); the associated error
type SHOULD be "modify". type SHOULD be "modify".
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o <jid-malformed/> -- the value of the 'to' attribute in the o <jid-malformed/> -- the value of the 'to' attribute in the
sender's stanza does not adhere to the syntax defined in sender's stanza does not adhere to the syntax defined in
Addressing Scheme (Section 3); the associated error type SHOULD be Addressing Scheme (Section 3); the associated error type SHOULD be
"modify". "modify".
o <not-acceptable/> -- the recipient or server understands the o <not-acceptable/> -- the recipient or server understands the
request but is refusing to process it because it does not meet request but is refusing to process it because it does not meet
criteria defined by the recipient or server (e.g., a local policy criteria defined by the recipient or server (e.g., a local policy
regarding acceptable words in messages); the associated error type regarding acceptable words in messages); the associated error type
SHOULD be "cancel". SHOULD be "modify".
o <not-allowed/> -- the recipient or server does not allow any o <not-allowed/> -- the recipient or server does not allow any
entity to perform the action; the associated error type SHOULD be entity to perform the action; the associated error type SHOULD be
"cancel". "cancel".
o <not-authorized/> -- the sender must provide proper credentials
before being allowed to perform the action, or has provided
improper credentials; the associated error type SHOULD be "auth".
o <payment-required/> -- the requesting entity is not authorized to o <payment-required/> -- the requesting entity is not authorized to
access the requested service because payment is required; the access the requested service because payment is required; the
associated error type SHOULD be "auth". associated error type SHOULD be "auth".
o <recipient-unavailable/> -- the intended recipient is temporarily o <recipient-unavailable/> -- the intended recipient is temporarily
unavailable; the associated error type SHOULD be "wait" (note: an unavailable; the associated error type SHOULD be "wait" (note: an
application MUST NOT return this error if doing so would provide application MUST NOT return this error if doing so would provide
information about the intended recipient's network availability to information about the intended recipient's network availability to
an entity that is not authorized to know such information). an entity that is not authorized to know such information).
o <redirect/> -- the recipient or server is redirecting requests for o <redirect/> -- the recipient or server is redirecting requests for
this information to another entity, usually temporarily (the error this information to another entity, usually temporarily (the error
stanza MAY contain a new address in the CDATA of the <redirect/> stanza SHOULD contain the alternate address, which MUST be a valid
element); the associated error type SHOULD be "modify". JID, in the CDATA of the <redirect/> element); the associated
error type SHOULD be "modify".
o <registration-required/> -- the requesting entity is not o <registration-required/> -- the requesting entity is not
authorized to access the requested service because registration is authorized to access the requested service because registration is
required; the associated error type SHOULD be "auth". required; the associated error type SHOULD be "auth".
o <remote-server-not-found/> -- a remote server or service specified o <remote-server-not-found/> -- a remote server or service specified
as part or all of the JID of the intended recipient does not as part or all of the JID of the intended recipient does not
exist; the associated error type SHOULD be "cancel". exist; the associated error type SHOULD be "cancel".
o <remote-server-timeout/> -- a remote server or service specified o <remote-server-timeout/> -- a remote server or service specified
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the stanza to the foreign domain (subject to local service the stanza to the foreign domain (subject to local service
provisioning and security policies regarding inter-domain provisioning and security policies regarding inter-domain
communication). There are two possible cases: communication). There are two possible cases:
A server-to-server stream already exists between the two domains: The A server-to-server stream already exists between the two domains: The
sender's server routes the stanza to the authoritative server for sender's server routes the stanza to the authoritative server for
the foreign domain over the existing stream the foreign domain over the existing stream
There exists no server-to-server stream between the two domains: The There exists no server-to-server stream between the two domains: The
sender's server (1) resolves the hostname of the foreign domain sender's server (1) resolves the hostname of the foreign domain
(as defined under Server-to-Server Communications (Section 14.3)), (as defined under Server-to-Server Communications (Section 14.4)),
(2) negotiates a server-to-server stream between the two domains (2) negotiates a server-to-server stream between the two domains
(as defined under Use of TLS (Section 5) and Use of SASL (Section (as defined under Use of TLS (Section 5) and Use of SASL (Section
6)), and (3) routes the stanza to the authoritative server for the 6)), and (3) routes the stanza to the authoritative server for the
foreign domain over the newly-established stream foreign domain over the newly-established stream
If routing to the recipient's server is unsuccessful, the sender's If routing to the recipient's server is unsuccessful, the sender's
server MUST return an error to the sender; if the recipient's server server MUST return an error to the sender; if the recipient's server
can be contacted but delivery by the recipient's server to the can be contacted but delivery by the recipient's server to the
recipient is unsuccessful, the recipient's server MUST return an recipient is unsuccessful, the recipient's server MUST return an
error to the sender by way of the sender's server. error to the sender by way of the sender's server.
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10.5 Node in Same Domain 10.5 Node in Same Domain
If the hostname of the domain identifier portion of the JID contained If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches a configured hostname of the server in the 'to' attribute matches a configured hostname of the server
itself and the JID contained in the 'to' attribute is of the form itself and the JID contained in the 'to' attribute is of the form
<node@domain> or <node@domain/resource>, the server SHOULD deliver <node@domain> or <node@domain/resource>, the server SHOULD deliver
the stanza to the intended recipient of the stanza as represented by the stanza to the intended recipient of the stanza as represented by
the JID contained in the 'to' attribute. The following rules apply: the JID contained in the 'to' attribute. The following rules apply:
1. If the JID contains a resource identifier (i.e., is of the form 1. If the JID contains a resource identifier (i.e., is of the form
<node@domain/resource>) and there is an available resource that <node@domain/resource>) and there exists a connected resource
matches the full JID, the recipient's server SHOULD deliver the that matches the full JID, the recipient's server SHOULD deliver
stanza to the stream or session that exactly matches the resource the stanza to the stream or session that exactly matches the
identifier. resource identifier.
2. If the JID contains a resource identifier and there is no 2. If the JID contains a resource identifier and there exists no
available resource that matches the full JID, the recipient's connected resource that matches the full JID, the recipient's
server SHOULD return to the sender a <service-unavailable/> server SHOULD return a <service-unavailable/> stanza error to the
stanza error. sender.
3. If the JID is of the form <node@domain> and there is at least one 3. If the JID is of the form <node@domain> and there exists at least
available resource available for the node, the recipient's server one connected resource for the node, the recipient's server MUST
MUST deliver the stanza to at least one of the available deliver the stanza to at least one of the connected resources,
resources, according to application-specific rules (a set of according to application-specific rules (a set of delivery rules
delivery rules for instant messaging and presence applications is for instant messaging and presence applications is defined in
defined in [XMPP-IM]). [XMPP-IM]).
11. XML Usage within XMPP 11. XML Usage within XMPP
11.1 Restrictions 11.1 Restrictions
XMPP is a simplified and specialized protocol for streaming XML XMPP is a simplified and specialized protocol for streaming XML
elements in order to exchange structured information in close to real elements in order to exchange structured information in close to real
time. Because XMPP does not require the parsing of arbitrary and time. Because XMPP does not require the parsing of arbitrary and
complete XML documents, there is no requirement that XMPP needs to complete XML documents, there is no requirement that XMPP needs to
support the full feature set of [XML]. In particular, the following support the full feature set of [XML]. In particular, the following
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descriptive purposes only. descriptive purposes only.
11.4 Inclusion of Text Declaration 11.4 Inclusion of Text Declaration
Implementations SHOULD send a text declaration before sending a Implementations SHOULD send a text declaration before sending a
stream header. Applications MUST follow the rules in [XML] regarding stream header. Applications MUST follow the rules in [XML] regarding
the circumstances under which a text declaration is included. the circumstances under which a text declaration is included.
11.5 Character Encoding 11.5 Character Encoding
Implementations MUST support the UTF-8 (RFC 2279 [UTF-8]) Implementations MUST support the UTF-8 (RFC 3269 [UTF-8])
transformation of Universal Character Set (ISO/IEC 10646-1 [UCS2]) transformation of Universal Character Set (ISO/IEC 10646-1 [UCS2])
characters, as required by RFC 2277 [CHARSET]. Implementations MUST characters, as required by RFC 2277 [CHARSET]. Implementations MUST
NOT attempt to use any other encoding. NOT attempt to use any other encoding.
12. Core Compliance Requirements 12. Core Compliance Requirements
This section summarizes the specific aspects of the Extensible This section summarizes the specific aspects of the Extensible
Messaging and Presence Protocol that MUST be supported by servers and Messaging and Presence Protocol that MUST be supported by servers and
clients in order to be considered compliant implementations, as well clients in order to be considered compliant implementations, as well
as additional protocol aspects that SHOULD be supported. For as additional protocol aspects that SHOULD be supported. For
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14.1 High Security 14.1 High Security
For the purposes of XMPP communications (client-to-server and For the purposes of XMPP communications (client-to-server and
server-to-server), the term "high security" refers to the use of server-to-server), the term "high security" refers to the use of
security technologies that provide both mutual authentication and security technologies that provide both mutual authentication and
integrity-checking; in particular, when using certificate-based integrity-checking; in particular, when using certificate-based
authentication to provide high security, a chain-of-trust SHOULD be authentication to provide high security, a chain-of-trust SHOULD be
established out-of-band, although a shared certificate authority established out-of-band, although a shared certificate authority
signing certificates could allow a previously unknown certificate to signing certificates could allow a previously unknown certificate to
establish trust in-band. establish trust in-band. See Section 14.2 below regarding certificate
validation procedures.
Standalone, self-signed service certificates SHOULD NOT be used;
rather, an entity that wishes to generate a self-signed service
certificate SHOULD first generate a self-signed Root CA certificate
and then generate a signed service certificate. Entities that
communicate with the service SHOULD be configured with the Root CA
certificate rather than the service certificate; this avoids problems
associated with simple comparison of service certificates. If a
self-signed service certificate is used, an entity SHOULD NOT trust
it if it is changed to another self-signed certificate or a
certificate signed by an unrecognized authority.
Implementations MUST support high security. Service provisioning Implementations MUST support high security. Service provisioning
SHOULD use high security, subject to local security policies. SHOULD use high security, subject to local security policies.
14.2 Client-to-Server Communications 14.2 Certificate Validation
When an XMPP peer communicates with another peer securely, it MUST
validate the peer's certificate. There are three possible cases:
Case #1: The peer contains an End Entity certificate which appears to
be certified by a chain of certificates terminating in a trust
anchor (as described in Section 6.1 of [X509]).
Case #2: The peer certificate is certified by a Certificate Authority
not known to the validating peer.
Case #3: The peer certificate is self-signed.
In Case #1, the validating peer MUST do one of two things:
1. Verify the peer certificate according to the rules of [X509].
The certificate SHOULD then be checked against the expected
identity of the peer following the rules described in [HTTP-TLS],
except that a subjectAltName extension of type "xmpp" MUST be
used as the identity if present. If one of these checks fails,
user-oriented clients MUST either notify the user (clients MAY
give the user the opportunity to continue with the connection in
any case) or terminate the connection with a bad certificate
error. Automated clients SHOULD terminate the connection (with a
bad certificate error) and log the error to an appropriate audit
log. Automated clients MAY provide a configuration setting that
disables this check, but MUST provide a setting which enables it.
2. The peer SHOULD show the certificate to a user for approval,
including the entire certificate chain. The peer MUST Cache the
certificate (or some non-forgeable representation such as a
hash). In future connections, the peer MUST verify that the same
certificate was presented and MUST notify the user if it has
changed.
In Case #2 and Case #3, implementations SHOULD act as in (2) above.
14.3 Client-to-Server Communications
A compliant implementation MUST support both TLS and SASL for A compliant implementation MUST support both TLS and SASL for
connections to a server. connections to a server.
The TLS protocol for encrypting XML streams (defined under Use of TLS The TLS protocol for encrypting XML streams (defined under Use of TLS
(Section 5)) provides a reliable mechanism for helping to ensure the (Section 5)) provides a reliable mechanism for helping to ensure the
confidentiality and data integrity of data exchanged between two confidentiality and data integrity of data exchanged between two
entities. entities.
The SASL protocol for authenticating XML streams (defined under Use The SASL protocol for authenticating XML streams (defined under Use
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hostname asserted by the server has been resolved. Such resolutions hostname asserted by the server has been resolved. Such resolutions
SHOULD first attempt to resolve the hostname using an [SRV] Service SHOULD first attempt to resolve the hostname using an [SRV] Service
of "xmpp-client" and Proto of "tcp", resulting in resource records of "xmpp-client" and Proto of "tcp", resulting in resource records
such as "_xmpp-client._tcp.example.com." (the use of the string such as "_xmpp-client._tcp.example.com." (the use of the string
"xmpp-client" for the service identifier is consistent with the IANA "xmpp-client" for the service identifier is consistent with the IANA
registration). If the SRV lookup fails, the fallback is a normal registration). If the SRV lookup fails, the fallback is a normal
IPv4/IPv6 address record resolution to determine the IP address, IPv4/IPv6 address record resolution to determine the IP address,
using the "xmpp-client" port of 5222 registered with the IANA. using the "xmpp-client" port of 5222 registered with the IANA.
The IP address and method of access of clients MUST NOT be made The IP address and method of access of clients MUST NOT be made
available by a server, nor are any connections other than the public by a server, nor are any connections other than the original
original server connection required. This helps to protect the server connection required. This helps to protect the client's
client's server from direct attack or identification by third server from direct attack or identification by third parties.
parties.
14.3 Server-to-Server Communications 14.4 Server-to-Server Communications
A compliant implementation MUST support both TLS and SASL for A compliant implementation MUST support both TLS and SASL for
inter-domain communications. For historical reasons, a compliant inter-domain communications. For historical reasons, a compliant
implementation SHOULD also support Server Dialback (Section 8). implementation SHOULD also support Server Dialback (Section 8).
Because service provisioning is a matter of policy, it is OPTIONAL Because service provisioning is a matter of policy, it is OPTIONAL
for any given domain to communicate with other domains, and for any given domain to communicate with other domains, and
server-to-server communications MAY be disabled by the administrator server-to-server communications MAY be disabled by the administrator
of any given deployment. If a particular domain enables inter-domain of any given deployment. If a particular domain enables inter-domain
communications, it SHOULD enable high security. communications, it SHOULD enable high security.
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more difficult to spoof XML stanzas. It is not a mechanism for more difficult to spoof XML stanzas. It is not a mechanism for
authenticating, securing, or encrypting streams between servers as is authenticating, securing, or encrypting streams between servers as is
done via SASL and TLS. Furthermore, it is susceptible to DNS done via SASL and TLS. Furthermore, it is susceptible to DNS
poisoning attacks unless DNSSec [DNSSEC] is used, and even if the DNS poisoning attacks unless DNSSec [DNSSEC] is used, and even if the DNS
information is accurate, dialback cannot protect from attacks where information is accurate, dialback cannot protect from attacks where
the attacker is capable of hijacking the IP address of the remote the attacker is capable of hijacking the IP address of the remote
domain. Domains requiring robust security SHOULD use TLS and SASL. domain. Domains requiring robust security SHOULD use TLS and SASL.
If SASL is used for server-to-server authentication, dialback SHOULD If SASL is used for server-to-server authentication, dialback SHOULD
NOT be used since it is unnecessary. NOT be used since it is unnecessary.
14.4 Order of Layers 14.5 Order of Layers
The order of layers in which protocols MUST be stacked is as follows: The order of layers in which protocols MUST be stacked is as follows:
1. TCP 1. TCP
2. TLS 2. TLS
3. SASL 3. SASL
4. XMPP 4. XMPP
The rationale for this order is that [TCP] is the base connection The rationale for this order is that [TCP] is the base connection
layer used by all of the protocols stacked on top of TCP, [TLS] is layer used by all of the protocols stacked on top of TCP, [TLS] is
often provided at the operating system layer, [SASL] is often often provided at the operating system layer, [SASL] is often
provided at the application layer, and XMPP is the application provided at the application layer, and XMPP is the application
itself. itself.
14.5 Lack of SASL Channel Binding to TLS 14.6 Lack of SASL Channel Binding to TLS
The SASL framework does not provide a mechanism to bind SASL The SASL framework does not provide a mechanism to bind SASL
authentication to a security layer providing confidentiality and authentication to a security layer providing confidentiality and
integrity protection that was negotiated at a lower layer. This lack integrity protection that was negotiated at a lower layer. This lack
of a "channel binding" prevents SASL from being able to verify that of a "channel binding" prevents SASL from being able to verify that
the source and destination end points to which the lower layer's the source and destination end points to which the lower layer's
security is bound are equivalent to the end points that SASL is security is bound are equivalent to the end points that SASL is
authenticating. If the end points are not identical, the lower authenticating. If the end points are not identical, the lower
layer's security cannot be trusted to protect data transmitted layer's security cannot be trusted to protect data transmitted
between the SASL authenticated entities. In such a situation, a SASL between the SASL authenticated entities. In such a situation, a SASL
security layer should be negotiated which effectively ignores the security layer should be negotiated which effectively ignores the
presence of the lower layer security. presence of the lower layer security.
14.6 Mandatory-to-Implement Technologies 14.7 Mandatory-to-Implement Technologies
At a minimum, all implementations MUST support the following At a minimum, all implementations MUST support the following
mechanisms: mechanisms:
for authentication: the SASL DIGEST-MD5 mechanism for authentication: the SASL [DIGEST-MD5] mechanism
for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA
cipher) cipher)
for both: TLS plus SASL EXTERNAL(using the for both: TLS plus SASL EXTERNAL(using the
TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side
certificates) certificates)
14.7 Firewalls 14.8 Firewalls
Communications using XMPP normally occur over [TCP] sockets on port Communications using XMPP normally occur over [TCP] sockets on port
5222 (client-to-server) or port 5269 (server-to-server), as 5222 (client-to-server) or port 5269 (server-to-server), as
registered with the IANA (see IANA Considerations (Section 15)). Use registered with the IANA (see IANA Considerations (Section 15)). Use
of these well-known ports allows administrators to easily enable or of these well-known ports allows administrators to easily enable or
disable XMPP activity through existing and commonly-deployed disable XMPP activity through existing and commonly-deployed
firewalls. firewalls.
14.8 Use of base64 in SASL 14.9 Use of base64 in SASL
Both the client and the server MUST verify any [BASE64] data received Both the client and the server MUST verify any [BASE64] data received
during SASL negotiation. An implementation MUST reject (not ignore) during SASL negotiation. An implementation MUST reject (not ignore)
any characters that are not explicitly allowed by the base64 any characters that are not explicitly allowed by the base64
alphabet; this helps to guard against creation of a covert channel alphabet; this helps to guard against creation of a covert channel
that could be used to "leak" information. An implementation MUST NOT that could be used to "leak" information. An implementation MUST NOT
break on invalid input and MUST reject any sequence of base64 break on invalid input and MUST reject any sequence of base64
characters containing the pad ('=') character if that character is characters containing the pad ('=') character if that character is
included as something other than the last character of the data (e.g. included as something other than the last character of the data (e.g.
"=AAA" or "BBBB=CCC"); this helps to guard against buffer overflow "=AAA" or "BBBB=CCC"); this helps to guard against buffer overflow
attacks and other attacks on the implementation. Base encoding attacks and other attacks on the implementation. Base encoding
visually hides otherwise easily recognized information, such as visually hides otherwise easily recognized information, such as
passwords, but does not provide any computational confidentiality. passwords, but does not provide any computational confidentiality.
Base 64 encoding MUST follow the definition in Section 3 of RFC 3548 Base 64 encoding MUST follow the definition in Section 3 of RFC 3548
[BASE64]. [BASE64].
14.9 Stringprep Profiles 14.10 Stringprep Profiles
XMPP makes use of the [NAMEPREP] profile of [STRINGPREP] for XMPP makes use of the [NAMEPREP] profile of [STRINGPREP] for
processing of domain identifiers; for security considerations related processing of domain identifiers; for security considerations related
to Nameprep, refer to the appropriate section of [NAMEPREP]. to Nameprep, refer to the appropriate section of [NAMEPREP].
In addition, XMPP defines two profiles of [STRINGPREP]: Nodeprep In addition, XMPP defines two profiles of [STRINGPREP]: Nodeprep
(Appendix A) for node identifiers and Resourceprep (Appendix B) for (Appendix A) for node identifiers and Resourceprep (Appendix B) for
resource identifiers. resource identifiers.
The Unicode and ISO/IEC 10646 repertoires have many characters that The Unicode and ISO/IEC 10646 repertoires have many characters that
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other kinds of entities could use node identifiers as part of their other kinds of entities could use node identifiers as part of their
addresses. The security of such services could be compromised based addresses. The security of such services could be compromised based
on different interpretations of the internationalized node on different interpretations of the internationalized node
identifier; for example, a user entering a single internationalized identifier; for example, a user entering a single internationalized
node identifier could access another user's account information, or a node identifier could access another user's account information, or a
user could gain access to an otherwise restricted chat room or user could gain access to an otherwise restricted chat room or
service. service.
A resource identifier can be employed as one part of an entity's A resource identifier can be employed as one part of an entity's
address in XMPP. One common usage is as the name for an instant address in XMPP. One common usage is as the name for an instant
messaging user's active session; another is as the nickname of a user messaging user's connected resource (active session); another is as
in a multi-user chat room; and many other kinds of entities could use the nickname of a user in a multi-user chat room; and many other
resource identifiers as part of their addresses. The security of kinds of entities could use resource identifiers as part of their
such services could be compromised based on different interpretations addresses. The security of such services could be compromised based
of the internationalized resource identifier; for example, a user on different interpretations of the internationalized resource
could attempt to initiate multiple sessions with the same name, or a identifier; for example, a user could attempt to initiate multiple
user could send a message to someone other than the intended sessions with the same name, or a user could send a message to
recipient in a multi-user chat room. someone other than the intended recipient in a multi-user chat room.
15. IANA Considerations 15. IANA Considerations
15.1 XML Namespace Name for TLS Data 15.1 XML Namespace Name for TLS Data
A URN sub-namespace for TLS-related data in the Extensible Messaging A URN sub-namespace for TLS-related data in the Extensible Messaging
and Presence Protocol (XMPP) is defined as follows. (This namespace and Presence Protocol (XMPP) is defined as follows. (This namespace
name adheres to the format defined in The IETF XML Registry name adheres to the format defined in The IETF XML Registry
[XML-REG].) [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-tls URI: urn:ietf:params:xml:ns:xmpp-tls
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[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[CHARSET] Alvestrand, H., "IETF Policy on Character Sets and [CHARSET] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998. Languages", BCP 18, RFC 2277, January 1998.
[DIGEST-MD5]
Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", RFC 2831, May 2000.
[DNS] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[GSS-API] Linn, J., "Generic Security Service Application Program [GSS-API] Linn, J., "Generic Security Service Application Program
Interface, Version 2", RFC 2078, January 1997. Interface, Version 2", RFC 2078, January 1997.
[HTTP-TLS] [HTTP-TLS]
Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[IMP-REQS] [IMP-REQS]
Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging / Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
Presence Protocol Requirements", RFC 2779, February 2000. Presence Protocol Requirements", RFC 2779, February 2000.
[IPv6] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[LANGTAGS] [LANGTAGS]
Alvestrand, H., "Tags for the Identification of Alvestrand, H., "Tags for the Identification of
Languages", BCP 47, RFC 3066, January 2001. Languages", BCP 47, RFC 3066, January 2001.
[IDNA] Faltstrom, P., Hoffman, P. and A. Costello, [IDNA] 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.
[NAMEPREP] [NAMEPREP]
Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
skipping to change at page 70, line 8 skipping to change at page 1, line 3313
and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246,
January 1999. January 1999.
[UCS2] International Organization for Standardization, [UCS2] International Organization for Standardization,
"Information Technology - Universal Multiple-octet coded "Information Technology - Universal Multiple-octet coded
Character Set (UCS) - Amendment 2: UCS Transformation Character Set (UCS) - Amendment 2: UCS Transformation
Format 8 (UTF-8)", ISO Standard 10646-1 Addendum 2, Format 8 (UTF-8)", ISO Standard 10646-1 Addendum 2,
October 1996. October 1996.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998. 10646", STD 63, RFC 3629, November 2003.
[X509] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002.
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, [XML] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (2nd ed)", W3C "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C
REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>. REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>.
[XML-NAMES] [XML-NAMES]
Bray, T., Hollander, D. and A. Layman, "Namespaces in Bray, T., Hollander, D. and A. Layman, "Namespaces in
XML", W3C REC-xml-names, January 1999, <http://www.w3.org/ XML", W3C REC-xml-names, January 1999, <http://www.w3.org/
TR/REC-xml-names>. TR/REC-xml-names>.
skipping to change at page 75, line 44 skipping to change at page 1, line 3584
<xs:choice minOccurs='0' maxOccurs='1'> <xs:choice minOccurs='0' maxOccurs='1'>
<xs:any namespace='jabber:client' <xs:any namespace='jabber:client'
minOccurs='0' minOccurs='0'
maxOccurs='unbounded'/> maxOccurs='unbounded'/>
<xs:any namespace='jabber:server' <xs:any namespace='jabber:server'
minOccurs='0' minOccurs='0'
maxOccurs='unbounded'/> maxOccurs='unbounded'/>
</xs:choice> </xs:choice>
<xs:element ref='error' minOccurs='0' maxOccurs='1'/> <xs:element ref='error' minOccurs='0' maxOccurs='1'/>
</xs:sequence> </xs:sequence>
<xs:attribute name='to' type='xs:string' use='optional'/>
<xs:attribute name='from' type='xs:string' use='optional'/> <xs:attribute name='from' type='xs:string' use='optional'/>
<xs:attribute name='id' type='xs:NMTOKEN' use='optional'/> <xs:attribute name='id' type='xs:NMTOKEN' use='optional'/>
<xs:attribute ref='xml:lang' use='optional'/> <xs:attribute name='to' type='xs:string' use='optional'/>
<xs:attribute name='version' type='xs:decimal' use='optional'/> <xs:attribute name='version' type='xs:decimal' use='optional'/>
<xs:attribute ref='xml:lang' use='optional'/>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='features'> <xs:element name='features'>
<xs:complexType> <xs:complexType>
<xs:sequence> <xs:choice minOccurs='0' maxOccurs='unbounded'>
<xs:any <xs:any namespace='urn:ietf:params:xml:ns:xmpp-tls'/>
namespace='##other' <xs:any namespace='urn:ietf:params:xml:ns:xmpp-sasl'/>
minOccurs='0' <xs:any namespace='urn:ietf:params:xml:ns:xmpp-bind'/>
maxOccurs='unbounded'/> <xs:any namespace='urn:ietf:params:xml:ns:xmpp-session'/>
</xs:sequence> <xs:any namespace='##other'/>
</xs:choice>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='error'> <xs:element name='error'>
<xs:complexType> <xs:complexType>
<xs:sequence> <xs:sequence>
<xs:any namespace='urn:ietf:params:xml:ns:xmpp-streams' <xs:any namespace='urn:ietf:params:xml:ns:xmpp-streams'
maxOccurs='2'/> maxOccurs='2'/>
<xs:any <xs:any
namespace='##other' namespace='##other'
skipping to change at page 78, line 44 skipping to change at page 1, line 3726
<xs:sequence> <xs:sequence>
<xs:element ref='mechanism' maxOccurs='unbounded'/> <xs:element ref='mechanism' maxOccurs='unbounded'/>
</xs:sequence> </xs:sequence>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='mechanism' type='xs:string'/> <xs:element name='mechanism' type='xs:string'/>
<xs:element name='auth'> <xs:element name='auth'>
<xs:complexType> <xs:complexType>
<xs:simpleContent>
<xs:extension base='xs:string'>
<xs:attribute name='mechanism' <xs:attribute name='mechanism'
type='xs:NMTOKEN' type='xs:NMTOKEN'
use='optional'/> use='optional'/>
</xs:extension>
</xs:simpleContent>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='challenge' type='xs:NMTOKEN'/> <xs:element name='challenge' type='xs:NMTOKEN'/>
<xs:element name='response' type='xs:NMTOKEN'/> <xs:element name='response' type='xs:NMTOKEN'/>
<xs:element name='abort' type='empty'/> <xs:element name='abort' type='empty'/>
<xs:element name='success' type='empty'/> <xs:element name='success' type='empty'/>
<xs:element name='failure'> <xs:element name='failure'>
<xs:complexType> <xs:complexType>
skipping to change at page 80, line 48 skipping to change at page 1, line 3829
</xs:extension> </xs:extension>
</xs:simpleContent> </xs:simpleContent>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='verify'> <xs:element name='verify'>
<xs:complexType> <xs:complexType>
<xs:simpleContent> <xs:simpleContent>
<xs:extension base='xs:NMTOKEN'> <xs:extension base='xs:NMTOKEN'>
<xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='from' type='xs:string' use='required'/>
<xs:attribute name='to' type='xs:string' use='required'/>
<xs:attribute name='id' type='xs:NMTOKEN' use='required'/> <xs:attribute name='id' type='xs:NMTOKEN' use='required'/>
<xs:attribute name='to' type='xs:string' use='required'/>
<xs:attribute name='type' use='optional'> <xs:attribute name='type' use='optional'>
<xs:simpleType> <xs:simpleType>
<xs:restriction base='xs:NCName'> <xs:restriction base='xs:NCName'>
<xs:enumeration value='invalid'/> <xs:enumeration value='invalid'/>
<xs:enumeration value='valid'/> <xs:enumeration value='valid'/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:attribute> </xs:attribute>
</xs:extension> </xs:extension>
</xs:simpleContent> </xs:simpleContent>
skipping to change at page 84, line 18 skipping to change at page 1, line 3987
headers. XMPP specifies inclusion of that attribute, with a value of headers. XMPP specifies inclusion of that attribute, with a value of
'1.0', as a way to signal support for the stream features '1.0', as a way to signal support for the stream features
(authentication, encryption, etc.) defined under Version Support (authentication, encryption, etc.) defined under Version Support
(Section 4.2.1) herein. (Section 4.2.1) herein.
Appendix E. Revision History Appendix E. Revision History
Note to RFC Editor: please remove this entire appendix, and the Note to RFC Editor: please remove this entire appendix, and the
corresponding entries in the table of contents, prior to publication. corresponding entries in the table of contents, prior to publication.
E.1 Changes from draft-ietf-xmpp-core-19 E.1 Changes from draft-ietf-xmpp-core-20
o Completed changes necessary to address IESG feedback.
E.2 Changes from draft-ietf-xmpp-core-19
o Fixed several typographical errors. o Fixed several typographical errors.
o Restricted values of 'type' attribute for IQ stanzas to those o Restricted values of 'type' attribute for IQ stanzas to those
defined in the schema (i.e., changed SHOULD to MUST) to ensure defined in the schema (i.e., changed SHOULD to MUST) to ensure
consistency with text in XMPP IM. consistency with text in XMPP IM.
o Added reference to RFC 3548. o Added reference to RFC 3548.
o Added the <not-authorized/> stanza error.
o Replaced RFC 2222 reference with reference to o Replaced RFC 2222 reference with reference to
draft-ietf-sasl-rfc2222bis. draft-ietf-sasl-rfc2222bis.
o Further clarified role and usage of user names in SASL mechanisms. o Further clarified role and usage of user names in SASL mechanisms.
o Added mention of 'code' attribute on error element. o Added mention of 'code' attribute on error element.
o Clarified several sentences in the dialback narrative. o Clarified several sentences in the dialback narrative.
o Clarified use of stringprep profiles and added reference to RFC o Clarified use of stringprep profiles and added reference to RFC
3490. 3490.
o Added security consideration regarding lack of SASL channel o Added security consideration regarding lack of SASL channel
binding to TLS per discussion at IETF 58 meeting. binding to TLS per discussion at IETF 58 meeting.
o Adjusted formatting to conform to RFC Editor requirements. o Adjusted formatting to conform to RFC Editor requirements.
E.2 Changes from draft-ietf-xmpp-core-18 E.3 Changes from draft-ietf-xmpp-core-18
o Added the 'xml:lang' attribute to the root <stream/> element per o Added the 'xml:lang' attribute to the root <stream/> element per
previous consensus and list discussion. previous consensus and list discussion.
o Changed "jabber-server" and "jabber-client" service names to o Changed "jabber-server" and "jabber-client" service names to
"xmpp-server" and "xmpp-client". "xmpp-server" and "xmpp-client".
o Added the <gone/>, <not-acceptable/>, and <redirect/> stanza o Added the <gone/>, <not-acceptable/>, and <redirect/> stanza
errors. errors.
skipping to change at page 86, line 5 skipping to change at page 1, line 4073
o Added section on resource binding to compensate for changes to o Added section on resource binding to compensate for changes to
SASL authorization identity text. SASL authorization identity text.
o Specified ABNF for JIDs. o Specified ABNF for JIDs.
o Checked all references. o Checked all references.
o Completed a thorough proofreading and consistency check of the o Completed a thorough proofreading and consistency check of the
entire text. entire text.
E.3 Changes from draft-ietf-xmpp-core-17 E.4 Changes from draft-ietf-xmpp-core-17
o Specified that UTF-8 is the only allowable encoding. o Specified that UTF-8 is the only allowable encoding.
o Added stream errors for <bad-namespace-prefix/>, <invalid-xml/>, o Added stream errors for <bad-namespace-prefix/>, <invalid-xml/>,
and <restricted-xml/>, as well as a <bad-format/> error for and <restricted-xml/>, as well as a <bad-format/> error for
generic XML error conditions. generic XML error conditions.
o Folded Nodeprep and Resourceprep profiles into this document. o Folded Nodeprep and Resourceprep profiles into this document.
o Moved most delivery handling rules from XMPP IM to XMPP Core. o Moved most delivery handling rules from XMPP IM to XMPP Core.
o Moved detailed stanza syntax descriptions from XMPP Core to XMPP o Moved detailed stanza syntax descriptions from XMPP Core to XMPP
IM. IM.
o Moved stanza schemas from XMPP Core to XMPP IM. o Moved stanza schemas from XMPP Core to XMPP IM.
E.4 Changes from draft-ietf-xmpp-core-16 E.5 Changes from draft-ietf-xmpp-core-16
o Added <conflict/> and <unsupported-encoding/> stream errors. o Added <conflict/> and <unsupported-encoding/> stream errors.
o Changed the datatype for the <see-other-host/> and o Changed the datatype for the <see-other-host/> and
<unsupported-version/> stream errors from 'xs:string' to 'empty'. <unsupported-version/> stream errors from 'xs:string' to 'empty'.
o Further clarified server handling of the basic stanza kinds. o Further clarified server handling of the basic stanza kinds.
o Further clarified character encoding rules per list discussion. o Further clarified character encoding rules per list discussion.
skipping to change at page 86, line 44 skipping to change at page 1, line 4112
o Added stream closure to SASL failure cases in order to mirror o Added stream closure to SASL failure cases in order to mirror
handling of TLS failures. handling of TLS failures.
o Added section on compliance requirements for server and client o Added section on compliance requirements for server and client
implementations. implementations.
o Added non-normative section on differences between Jabber usage o Added non-normative section on differences between Jabber usage
and XMPP specifications. and XMPP specifications.
E.5 Changes from draft-ietf-xmpp-core-15 E.6 Changes from draft-ietf-xmpp-core-15
o Added <connection-timeout/> and <policy-violation/> stream errors. o Added <connection-timeout/> and <policy-violation/> stream errors.
o Added <aborted/> SASL error and clarified <bad-protocol/> error. o Added <aborted/> SASL error and clarified <bad-protocol/> error.
o Made 'id' required for IQ stanzas. o Made 'id' required for IQ stanzas.
E.6 Changes from draft-ietf-xmpp-core-14 E.7 Changes from draft-ietf-xmpp-core-14
o Added SRV lookup for client-to-server communications. o Added SRV lookup for client-to-server communications.
o Changed server SRV record to conform to RFC 2782; specifically, o Changed server SRV record to conform to RFC 2782; specifically,
the service identifier was changed from 'jabber' to the service identifier was changed from 'jabber' to
'jabber-server'. 'jabber-server'.
E.7 Changes from draft-ietf-xmpp-core-13 E.8 Changes from draft-ietf-xmpp-core-13
o Clarified stream restart after successful TLS and SASL o Clarified stream restart after successful TLS and SASL
negotiation. negotiation.
o Clarified requirement for resolution of DNS hostnames. o Clarified requirement for resolution of DNS hostnames.
o Clarified text regarding namespaces. o Clarified text regarding namespaces.
o Clarified examples regarding empty <stream:features/> element. o Clarified examples regarding empty <stream:features/> element.
o Added several more SASL error conditions. o Added several more SASL error conditions.
o Changed <invalid-xml/> stream error to <improper-addressing/> and o Changed <invalid-xml/> stream error to <improper-addressing/> and
added to schema. added to schema.
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.8 Changes from draft-ietf-xmpp-core-12 E.9 Changes from draft-ietf-xmpp-core-12
o Moved server dialback to a separate section; clarified its o Moved server dialback to a separate section; clarified its
security characteristics and its role in the protocol. security characteristics and its role in the protocol.
o Adjusted error handling syntax and semantics per list discussion. o Adjusted error handling syntax and semantics per list discussion.
o Further clarified length of node identifiers and total length of o Further clarified length of node identifiers and total length of
JIDs. JIDs.
o Documented message type='normal'. o Documented message type='normal'.
o Corrected several small errors in the TLS and SASL sections. o Corrected several small errors in the TLS and SASL sections.
o Corrected several errors in the schemas. o Corrected several errors in the schemas.
E.9 Changes from draft-ietf-xmpp-core-11 E.10 Changes from draft-ietf-xmpp-core-11
o Corrected several small errors in the TLS and SASL sections. o Corrected several small errors in the TLS and SASL sections.
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.10 Changes from draft-ietf-xmpp-core-10 E.11 Changes from draft-ietf-xmpp-core-10
o Adjusted TLS content regarding certificate validation process. o Adjusted TLS content regarding certificate validation process.
o Specified that stanza error extensions for specific applications o Specified that stanza error extensions for specific applications
are to be properly namespaced children of the relevant descriptive are to be properly namespaced children of the relevant descriptive
element. element.
o Clarified rules for inclusion of the 'id' attribute. o Clarified rules for inclusion of the 'id' attribute.
o Specified that the 'xml:lang' attribute SHOULD be included (per o Specified that the 'xml:lang' attribute SHOULD be included (per
list discussion). list discussion).
o Made small editorial changes and fixed several schema errors. o Made small editorial changes and fixed several schema errors.
E.11 Changes from draft-ietf-xmpp-core-09 E.12 Changes from draft-ietf-xmpp-core-09
o Fixed several dialback error conditions. o Fixed several dialback error conditions.
o Cleaned up rules regarding TLS and certificate processing based on o Cleaned up rules regarding TLS and certificate processing based on
off-list feedback. off-list feedback.
o Changed <stream-condition/> and <stanza-condition/> elements to o Changed <stream-condition/> and <stanza-condition/> elements to
<condition/>. <condition/>.
o Added or modified several stream and stanza error conditions. o Added or modified several stream and stanza error conditions.
o Specified only one child allowed for IQ, or two if type="error". o Specified only one child allowed for IQ, or two if type="error".
o Fixed several errors in the schemas. o Fixed several errors in the schemas.
E.12 Changes from draft-ietf-xmpp-core-08 E.13 Changes from draft-ietf-xmpp-core-08
o Incorporated list discussion regarding addressing, SASL, TLS, TCP, o Incorporated list discussion regarding addressing, SASL, TLS, TCP,
dialback, namespaces, extensibility, and the meaning of 'ignore' dialback, namespaces, extensibility, and the meaning of 'ignore'
for routers and recipients. for routers and recipients.
o Specified dialback error conditions. o Specified dialback error conditions.
o Made small editorial changes to address RFC Editor requirements. o Made small editorial changes to address RFC Editor requirements.
E.13 Changes from draft-ietf-xmpp-core-07 E.14 Changes from draft-ietf-xmpp-core-07
o Made several small editorial changes. o Made several small editorial changes.
E.14 Changes from draft-ietf-xmpp-core-06 E.15 Changes from draft-ietf-xmpp-core-06
o Added text regarding certificate validation in TLS negotiation per o Added text regarding certificate validation in TLS negotiation per
list discussion. list discussion.
o Clarified nature of XML restrictions per discussion with W3C, and o Clarified nature of XML restrictions per discussion with W3C, and
moved XML Restrictions subsection under "XML Usage within XMPP". moved XML Restrictions subsection under "XML Usage within XMPP".
o Further clarified that XML streams are unidirectional. o Further clarified that XML streams are unidirectional.
o Changed stream error and stanza error namespace names to conform o Changed stream error and stanza error namespace names to conform
to the format defined in The IETF XML Registry. to the format defined in The IETF XML Registry.
o Removed note to RFC Editor regarding provisional namespace names. o Removed note to RFC Editor regarding provisional namespace names.
E.15 Changes from draft-ietf-xmpp-core-05 E.16 Changes from draft-ietf-xmpp-core-05
o Added <invalid-namespace/> as a stream error condition. o Added <invalid-namespace/> as a stream error condition.
o Adjusted security considerations per discussion at IETF 56 and on o Adjusted security considerations per discussion at IETF 56 and on
list. list.
E.16 Changes from draft-ietf-xmpp-core-04 E.17 Changes from draft-ietf-xmpp-core-04
o Added server-to-server examples for TLS and SASL. o Added server-to-server examples for TLS and SASL.
o Changed error syntax, rules, and examples based on list o Changed error syntax, rules, and examples based on list
discussion. discussion.
o Added schemas for the TLS, stream error, and stanza error o Added schemas for the TLS, stream error, and stanza error
namespaces. namespaces.
o Added note to RFC Editor regarding provisional namespace names. o Added note to RFC Editor regarding provisional namespace names.
o Made numerous small editorial changes and clarified text o Made numerous small editorial changes and clarified text
throughout. throughout.
E.17 Changes from draft-ietf-xmpp-core-03 E.18 Changes from draft-ietf-xmpp-core-03
o Clarified rules and procedures for TLS and SASL. o Clarified rules and procedures for TLS and SASL.
o Amplified stream error code syntax per list discussion. o Amplified stream error code syntax per list discussion.
o Made numerous small editorial changes. o Made numerous small editorial changes.
E.18 Changes from draft-ietf-xmpp-core-02 E.19 Changes from draft-ietf-xmpp-core-02
o Added dialback schema. o Added dialback schema.
o Removed all DTDs since schemas provide more complete definitions. o Removed all DTDs since schemas provide more complete definitions.
o Added stream error codes. o Added stream error codes.
o Clarified error code "philosophy". o Clarified error code "philosophy".
E.19 Changes from draft-ietf-xmpp-core-01 E.20 Changes from draft-ietf-xmpp-core-01
o Updated the addressing restrictions per list discussion and added o Updated the addressing restrictions per list discussion and added
references to the new Nodeprep and Resourceprep profiles. references to the new Nodeprep and Resourceprep profiles.
o Corrected error in Use of SASL regarding 'version' attribute. o Corrected error in Use of SASL regarding 'version' attribute.
o Made numerous small editorial changes. o Made numerous small editorial changes.
E.20 Changes from draft-ietf-xmpp-core-00 E.21 Changes from draft-ietf-xmpp-core-00
o Added information about TLS from list discussion. o Added information about TLS from list discussion.
o Clarified meaning of "ignore" based on list discussion. o Clarified meaning of "ignore" based on list discussion.
o Clarified information about Universal Character Set data and o Clarified information about Universal Character Set data and
character encodings. character encodings.
o Provided base64-decoded information for examples. o Provided base64-decoded information for examples.
o Fixed several errors in the schemas. o Fixed several errors in the schemas.
o Made numerous small editorial fixes. o Made numerous small editorial fixes.
E.21 Changes from draft-miller-xmpp-core-02 E.22 Changes from draft-miller-xmpp-core-02
o Brought Use of SASL section into line with discussion on list and o Brought Use of SASL section into line with discussion on list and
at IETF 55 meeting. at IETF 55 meeting.
o Added information about the optional 'xml:lang' attribute per o Added information about the optional 'xml:lang' attribute per
discussion on list and at IETF 55 meeting. discussion on list and at IETF 55 meeting.
o Specified that validation is neither required nor recommended, and o Specified that validation is neither required nor recommended, and
that the formal definitions (DTDs and schemas) are included for that the formal definitions (DTDs and schemas) are included for
descriptive purposes only. descriptive purposes only.
skipping to change at page 92, line 29 skipping to change at page 1, line 4365
be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
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The limited permissions granted above are perpetual and will not be
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Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
XMPP Working Group P. Saint-Andre (ed.)
Internet-Draft Jabber Software Foundation
Expires: July 6, 2004 January 6, 2004
Extensible Messaging and Presence Protocol (XMPP): Instant Messaging
and Presence
draft-ietf-xmpp-im-20
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
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
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The list of current Internet-Drafts can be accessed at http://
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This Internet-Draft will expire on July 6, 2004.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This memo describes extensions to and applications of the core
features of the Extensible Messaging and Presence Protocol (XMPP)
that provide the basic instant messaging (IM) and presence
functionality defined in RFC 2779.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Syntax of XML Stanzas . . . . . . . . . . . . . . . . . . . 4
3. Session Establishment . . . . . . . . . . . . . . . . . . . 11
4. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 14
5. Exchanging Presence Information . . . . . . . . . . . . . . 16
6. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 25
7. Roster Management . . . . . . . . . . . . . . . . . . . . . 26
8. Integration of Roster Items and Presence Subscriptions . . . 31
9. Subscription States . . . . . . . . . . . . . . . . . . . . 54
10. Blocking Communication . . . . . . . . . . . . . . . . . . . 59
11. Server Rules for Handling XML Stanzas . . . . . . . . . . . 79
12. IM and Presence Compliance Requirements . . . . . . . . . . 81
13. Internationalization Considerations . . . . . . . . . . . . 82
14. Security Considerations . . . . . . . . . . . . . . . . . . 82
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 83
Normative References . . . . . . . . . . . . . . . . . . . . 84
Informative References . . . . . . . . . . . . . . . . . . . 85
Author's Address . . . . . . . . . . . . . . . . . . . . . . 85
A. vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
B. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 86
C. Differences Between Jabber IM/Presence and XMPP . . . . . . 98
D. Revision History . . . . . . . . . . . . . . . . . . . . . . 99
Intellectual Property and Copyright Statements . . . . . . . 106
1. Introduction
1.1 Overview
The Extensible Messaging and Presence Protocol (XMPP) is a protocol
for streaming XML [XML] elements in order to exchange messages and
presence information in close to real time. The core features of
XMPP are defined in Extensible Messaging and Presence Protocol
(XMPP): Core [XMPP-CORE]. These features -- mainly XML streams, use
of TLS and SASL, and the <message/>, <presence/>, and <iq/> children
of the stream root -- provide the building blocks for many types of
near-real-time applications, which may be layered on top of the core
by sending application-specific data qualified by particular XML
namespaces [XML-NAMES]. This memo describes extensions to and
applications of the core features of XMPP that provide the basic
functionality expected of an instant messaging (IM) and presence
application as defined in RFC 2779 [IMP-REQS].
1.2 Requirements
For the purposes of this memo, the requirements of a basic instant
messaging and presence application are defined by [IMP-REQS], which
at a high level stipulates that a user must be able to complete the
following use cases:
o Exchange messages with other users
o Exchange presence information with other users
o Manage subscriptions to and from other users
o Manage items in a contact list (in XMPP this is called a "roster")
o Block communications to or from specific other users
Detailed definitions of these functionality areas are contained in
[IMP-REQS], and the interested reader is directed to that document
regarding the requirements addressed herein.
[IMP-REQS] also stipulates that presence services must be separable
from instant messaging services; i.e., it must be possible to use the
protocol to provide a presence service, an instant messaging service,
or both. Although the text of this memo assumes that implementations
and deployments will want to offer a unified instant messaging and
presence service, there is no requirement that a service must offer
both a presence service and an instant messaging service, and the
protocol makes it possible to offer separate and distinct services
for presence and for instant messaging.
Note: While XMPP-based instant messaging and presence meets the
requirements of [IMP-REQS], it was not designed explicitly with that
specification in mind, since the base protocol evolved through an
open development process within the Jabber open-source community
before RFC 2779 was written. Note also that although protocols
addressing many other functionality areas have been defined in the
Jabber community, such protocols are not included in this memo
because they are not required by [IMP-REQS].
1.3 Terminology
This memo inherits the terminology defined in [XMPP-CORE].
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [TERMS].
1.4 Contributors
Most of the core aspects of the Extensible Messaging and Presence
Protocol were developed originally within the Jabber open-source
community in 1999. This community was founded by Jeremie Miller, who
released source code for the initial version of the jabberd server in
January 1999. Major early contributors to the base protocol also
included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave
Smith. Work specific to instant messaging and presence by the XMPP
Working Group has concentrated especially on IM session establishment
and communication blocking (privacy rules); the session establishment
protocol was mainly developed by Rob Norris and Joe Hildebrand, and
the privacy rules protocol was originally contributed by Peter
Millard.
1.5 Acknowledgements
Thanks are due to a number of individuals in addition to the
contributors listed. Although it is difficult to provide a complete
list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Schuyler Heath, Jonathan Hogg, Craig
Kaes, Jacek Konieczny, Alexey Melnikov, Keith Minkler, Julian Missig,
Pete Resnick, Marshall Rose, Alexey Shchepin, Jean-Louis Seguineau,
Iain Shigeoka, and David Waite. Thanks also to members of the XMPP
Working Group and the IETF community for comments and feedback
provided throughout the life of this memo.
2. Syntax of XML Stanzas
The basic semantics and common attributes of XML stanzas qualified by
the 'jabber:client' and 'jabber:server' namespaces are defined in
[XMPP-CORE]. However, these namespaces also define various child
elements, as well as values for the common 'type' attribute, that are
specific to instant messaging and presence applications. Thus,
before addressing particular "use cases" for such applications, we
here further describe the syntax of XML stanzas, thereby
supplementing the discussion in [XMPP-CORE].
2.1 Message Syntax
Message stanzas in the 'jabber:client' or 'jabber:server' namespace
are used to "push" information to another entity. Common uses in
instant messaging applications include single messages, messages sent
in the context of a chat conversation, messages sent in the context
of a multi-user chat room, headlines, and errors.
2.1.1 Types of Message
The 'type' attribute of a message stanza is RECOMMENDED; if included,
it specifies the conversational context of the message, thus
providing a hint regarding presentation (e.g., in a GUI). If
included, the 'type' attribute MUST have one of the following values:
o chat -- The message is sent in the context of a one-to-one chat
conversation. A compliant client SHOULD present the message an
interface enabling one-to-one chat between the two parties,
including an appropriate conversation history.
o error -- An error has occurred related to a previous message sent
by the sender (for details regarding stanza error syntax, refer to
[XMPP-CORE]). A compliant client SHOULD present an appropriate
interface informing the sender of the nature of the error.
o groupchat -- The message is sent in the context of a multi-user
chat environment. A compliant client SHOULD present the message
an interface enabling many-to-many chat between the parties,
including a roster of parties in the chatroom and an appropriate
conversation history. Full definition of XMPP-based groupchat
protocols is out of scope for this memo.
o headline -- The message is probably generated by an automated
service that delivers or broadcasts content (news, sports, market
information, RSS feeds, etc.). No reply to the message is
expected, and a compliant client SHOULD present the message an
interface that appropriately differentiates the message from
standalone messages, chat sessions, or groupchat sessions (e.g.,
by not providing the recipient with the ability to reply).
o normal -- The message is a single message that is sent outside the
context of a one-to-one conversation or groupchat, and to which it
is expected that the recipient will reply. A compliant client
SHOULD present the message in an interface enabling the recipient
to reply.
An IM application SHOULD support all of the foregoing message types;
if an application receives a message with no 'type' attribute or the
application does not understand the value of the 'type' attribute
provided, it MUST consider the message to be of type "normal" (i.e.,
"normal" is the default). The "error" type MUST be generated only in
response to an error related to a message received from another
entity.
Although the 'type' attribute is NOT REQUIRED, it is considered
polite to mirror the type in any replies to a message; furthermore,
some specialized applications (e.g., a multi-user chat service) MAY
at their discretion enforce the use of a particular message type
(e.g., type='groupchat').
2.1.2 Child Elements
As described under extended namespaces (Section 2.4), a message
stanza MAY contain any properly-namespaced child element.
In accordance with the default namespace declaration, by default a
message stanza is in the 'jabber:client' or 'jabber:server'
namespace, which defines certain allowable children of message
stanzas. If the message stanza is of type "error", it MUST include
an <error/> child; for details, see [XMPP-CORE]. Otherwise, the
message stanza MAY contain any of the following child elements
without an explicit namespace declaration:
1. <subject/>
2. <body/>
3. <thread/>
2.1.2.1 Subject
The <subject/> element contains XML character data that specifies the
topic of the message. The <subject/> element MUST NOT possess any
attributes, with the exception of the 'xml:lang' attribute. Multiple
instances of the <subject/> element MAY be included for the purpose
of providing alternate versions of the same subject, but only if each
instance possesses an 'xml:lang' attribute with a distinct language
value. The <subject/> element MUST NOT contain mixed content (as
defined in Section 3.2.2 of [XML]).
2.1.2.2 Body
The <body/> element contains XML character data that specifies the
textual contents of the message; this child element is normally
included but NOT REQUIRED. The <body/> element MUST NOT possess any
attributes, with the exception of the 'xml:lang' attribute. Multiple
instances of the <body/> element MAY be included but only if each
instance possesses an 'xml:lang' attribute with a distinct language
value. The <body/> element MUST NOT contain mixed content (as
defined in Section 3.2.2 of [XML]).
2.1.2.3 Thread
The <thread/> element contains XML character data that specifies an
identifier that is used for tracking a conversation thread (sometimes
referred to as an "instant messaging session") between two entities.
The value of the <thread/> element is generated by the sender and
that SHOULD be copied back in any replies. If used, it MUST be
unique to that conversation thread within the stream and MUST be
consistent throughout that conversation (a client that receives a
message from the same full JID but with a different thread ID MUST
assume that the message in question exists outside the context of the
existing conversation thread). The use of the <thread/> element is
OPTIONAL and is not used to identify individual messages, only
conversations. A message stanza MUST NOT contain more than one
<thread/> element. The <thread/> element MUST NOT possess any
attributes. The value of the <thread/> element MUST be treated as
opaque by entities; no semantic meaning may be derived from it, and
only exact comparisons may be made against it. The <thread/> element
MUST NOT contain mixed content (as defined in Section 3.2.2 of
[XML]).
2.2 Presence Syntax
Presence stanzas are used in the 'jabber:client' or 'jabber:server'
namespace to express an entity's current availability status (offline
or online, along with various sub-states of the latter and optional
user-defined descriptive text), and to communicate that status to
other entities. Presence stanzas are also used to negotiate and
manage subscriptions to the presence of other entities.
2.2.1 Types of Presence
The 'type' attribute of a presence stanza is OPTIONAL. A presence
stanza that does not possess a 'type' attribute is used to signal to
the server that the sender is online and available for communication.
If included, the 'type' attribute specifies a lack of availability, a
request to manage a subscription to another entity's presence, a
request for another entity's current presence, or an error related to
a previously-sent presence stanza. If included, the 'type' attribute
MUST have one of the following values:
o unavailable -- Signals that the entity is no longer available for
communication.
o subscribe -- The sender wishes to subscribe to the recipient's
presence.
o subscribed -- The sender has allowed the recipient to receive
their presence.
o unsubscribe -- A notification that an entity is unsubscribing from
another entity's presence.
o unsubscribed -- The subscription request has been denied or a
previously-granted subscription has been cancelled.
o probe -- A request for an entity's current presence; SHOULD be
generated only by a server and SHOULD NOT be generated by a
client.
o error -- An error has occurred regarding processing or delivery of
a previously-sent presence stanza.
For detailed information regarding presence semantics and the
subscription model used in the context of XMPP-based instant
messaging and presence applications, refer to Exchanging Presence
Information (Section 5) and Managing Subscriptions (Section 6).
2.2.2 Child Elements
As described under extended namespaces (Section 2.4), a presence
stanza MAY contain any properly-namespaced child element.
In accordance with the default namespace declaration, by default a
presence stanza is in the 'jabber:client' or 'jabber:server'
namespace, which defines certain allowable children of presence
stanzas. If the presence stanza is of type "error", it MUST include
an <error/> child; for details, see [XMPP-CORE]. If the presence
stanza possesses no 'type' attribute, it MAY contain any of the
following child elements (note that the <status/> child MAY be sent
in a presence stanza of type "unavailable" or, for historical
reasons, "subscribe"):
1. <show/>
2. <status/>
3. <priority/>
2.2.2.1 Show
The OPTIONAL <show/> element contains XML character data that
specifies the particular availability status of an entity or specific
resource. A presence stanza MUST NOT contain more than one <show/>
element. The <show/> element MUST NOT possess any attributes. The
XML character data contained in the <show/> element is not intended
to be human-readable. If provided, the CDATA value MUST be one of
the following (additional availability types could be defined through
a properly-namespaced child element of the presence stanza):
o away -- The entity or resource is temporarily away.
o chat -- The entity or resource is actively interested in chatting.
o xa -- The entity or resource is away for an extended period (xa =
"eXtended Away").
o dnd -- The entity or resource is busy (dnd = "Do Not Disturb").
If no <show/> element is provided, the entity is assumed to be online
and available.
2.2.2.2 Status
The OPTIONAL <status/> element contains a natural-language
description of availability status. It is normally used in
conjunction with the show element to provide a detailed description
of an availability state (e.g., "In a meeting"). The <status/>
element MUST NOT possess any attributes, with the exception of the
'xml:lang' attribute. Multiple instances of the <status/> element
MAY be included but only if each instance possesses an 'xml:lang'
attribute with a distinct language value.
2.2.2.3 Priority
The OPTIONAL <priority/> element contains XML character data that
specifies the priority level of the resource. The value may be any
integer between -128 and +127. A presence stanza MUST NOT contain
more than one <priority/> element. The <priority/> element MUST NOT
possess any attributes. If no priority is provided, a server SHOULD
consider the priority to be zero. For information regarding the
semantics of priority values in stanza routing within instant
messaging and presence applications, refer to Server Rules for
Handling XML Stanzas (Section 11).
2.3 IQ Syntax
IQ stanzas provide a structured request-response mechanism. The
basic semantics of that mechanism are defined in [XMPP-CORE], whereas
the specific semantics required to complete particular use cases are
defined in all cases by an extended namespace (Section 2.4) (note
that the 'jabber:client' and 'jabber:server' namespaces do not define
any children of IQ stanzas). This memo defines two such extended
namespaces, one for Roster Management (Section 7) and the other for
Blocking Communication (Section 10); however, an IQ stanza MAY
contain structured information qualified by any extended namespace.
2.4 Extended Namespaces
While the three XML stanza kinds defined in the "jabber:client" or
"jabber:server" namespace (along with their attributes and child
elements) provide a basic level of functionality for messaging and
presence, XMPP uses XML namespaces to extend the stanzas for the
purpose of providing additional functionality. Thus a message or
presence MAY contain one or more optional child elements containing
content that extends the meaning of the message (e.g., an
XHTML-formatted version of the message body), and an IQ stanza MAY
contain one such child element. This child element MAY have any name
and MUST possess an 'xmlns' namespace declaration (other than
"jabber:client", "jabber:server", or "http://etherx.jabber.org/
streams") that defines all data contained within the child element.
Support for any given extended namespace is OPTIONAL on the part of
any implementation (aside from the extended namespaces defined
herein). If an entity does not understand such a namespace, the
entity's expected behavior depends on whether the entity is (1) the
recipient or (2) an entity that is routing the stanza to the
recipient:
Recipient: If a recipient receives a stanza that contains a child
element it does not understand, it SHOULD ignore that specific XML
data, i.e., it SHOULD not process it or present it to a user or
associated application (if any). In particular:
* If an entity receives a message or presence stanza that
contains XML data qualified by a namespace it does not
understand, the portion of the stanza that is in the unknown
namespace SHOULD be ignored.
* If an entity receives a message stanza whose only child element
is qualified by a namespace it does not understand, it MUST
ignore the entire stanza.
* If an entity receives an IQ stanza of type "get" or "set"
containing a child element qualified by a namespace it does not
understand, the entity SHOULD return an IQ stanza of type
"error" with an error condition of <feature-not-implemented/>.
Router: If a routing entity (usually a server) handles a stanza that
contains a child element it does not understand, it SHOULD ignore
the associated XML data by passing it on untouched to the
recipient.
3. Session Establishment
Most instant messaging and presence applications based on XMPP are
implemented via a client-server architecture that requires a client
to establish a session on a server in order to engage in the expected
instant messaging and presence activities. However, there are
several pre-conditions that MUST be met before a client can establish
an instant messaging and presence session. These are:
1. Stream Authentication -- a client MUST complete stream
authentication as documented in [XMPP-CORE] before attempting to
establish a session or send any XML stanzas.
2. Resource Binding -- after completing stream authentication, a
client MUST bind a resource to the stream so that the client's
address is of the form <user@domain/resource>, after which the
entity is said to be a "connected resource" in the terminology of
[XMPP-CORE].
If a server supports sessions, it MUST include a <session/> element
qualified by the 'urn:ietf:params:xml:ns:xmpp-session' namespace in
the stream features it advertises to a client after the completion of
stream authentication as defined in [XMPP-CORE]:
Server advertises session establishment feature to client:
<stream:stream
xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams'
id='c2s_345'
from='example.com'
version='1.0'>
<stream:features>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'>
</stream:features>
Upon being so informed that session establishment is required (and
after completing resource binding), the client MUST establish a
session if it desires to engage in instant messaging and presence
functionality; it completes this step by sending to the server an IQ
stanza of type "set" containing an empty <session/> child element
qualified by the 'urn:ietf:params:xml:ns:xmpp-session' namespace:
Step 1: Client requests session with server:
<iq from='someuser@example.com'
to='example.com'
type='set'
id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
</iq>
Step 2: Server informs client that session has been created:
<iq from='example.com'
to='someuser@example.com'
type='result'
id='sess_1'/>
Upon establishing a session, a connected resource (in the terminology
of [XMPP-CORE]) is said to be an "active resource".
Several error conditions are possible. For example, the server may
encounter an internal condition that prevents it from creating the
session, the username or authorization identity may lack permissions
to create a session, or there may already be an active resource
associated with a resource identifier of the same name.
If the server encounters an internal condition that prevents it from
creating the session, it MUST return an error.
Step 2 (alt): Server responds with error (internal server error):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='wait'>
<internal-server-error
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If the username or resource is not allowed to create a session, the
server MUST return an error (e.g., forbidden).
Step 2 (alt): Server responds with error (username or resource not
allowed to create session):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='auth'>
<forbidden
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
If there is already an active resource of the same name, the server
MUST either (1) terminate the active resource and allow the
newly-requested session, or (2) disallow the newly-requested session
and maintain the active resource. Which of these the server does is
up to the implementation, although it is RECOMMENDED to implement
case #1. In case #1, the server SHOULD send a <conflict/> stream
error to the active resource, terminate the XML stream and underlying
TCP connection for the active resource, and return a IQ stanza of
type "result" (indicating success) to the newly-requested session. In
case #2, the server SHOULD send a <conflict/> stanza error to the
newly-requested session but maintain the XML stream for that
connection so that the newly-requested session has an opportunity to
negotiate a non-conflicting resource identifier before sending
another request for session establishment.
Step 2 (alt): Server informs active resource of resource conflict
(case #1):
<stream:error>
<conflict xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
</stream:error>
</stream:stream>
Step 2 (alt): Server informs newly-requested session of resource
conflict (case #2):
<iq type='error' id='sess_1'>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
<error type='cancel'>
<conflict xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
After establishing a session, a client SHOULD send initial presence
and request its roster as described below, although these actions are
NOT REQUIRED.
Note: Before allowing the creation of instant messaging and presence
sessions, a server MAY require prior account provisioning. Possible
methods for account provisioning include account creation by a server
administrator as well as in-band account registration using the
'jabber:iq:register' namespace; the latter method is documented by
the Jabber Software Foundation [JSF] at <http://www.jabber.org/
protocol/> but is out of scope for this memo.
4. Exchanging Messages
Exchanging messages is a basic use of XMPP and is brought about when
a user generates a message stanza that is addressed to another
entity. As defined under Server Rules for Handling XML Stanzas
(Section 11), the sender's server is responsible for delivering the
message to the intended recipient (if the recipient is on the same
server) or for routing the message to the recipient's server (if the
recipient is on a different server).
For information regarding the syntax of message stanzas as well as
their defined attributes and child elements, refer to Message Syntax
(Section 2.1).
4.1 Specifying an Intended Recipient
An instant messaging client SHOULD specify an intended recipient for
a message by providing the JID of an entity other than the sender in
the 'to' attribute of the <message/> stanza. If the message is being
sent in reply to a message previously received from an address of the
form <user@domain/resource> (e.g., within the context of a chat
session), the value of the 'to' address SHOULD be the full JID (of
the form <user@domain/resource>) rather than merely of the form
<user@domain> unless the sender has knowledge (via presence) that the
intended recipient's resource is no longer available. If the message
is being sent outside the context of any existing chat session or
received message, the value of the 'to' address SHOULD be of the form
<user@domain> rather than of the form <user@domain/resource>.
4.2 Specifying a Message Type
As noted, it is RECOMMENDED for a message stanza to possess a 'type'
attribute whose value captures the conversational context (if any) of
the message (see Type (Section 2.1.1)).
The following example shows a valid value of the 'type' attribute:
Example: A message of a defined type:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<body>Wherefore art thou, Romeo?</body>
</message>
4.3 Specifying a Message Body
A message stanza MAY (and often will) contain a child <body/> element
whose XML character data specifies the primary meaning of the message
(see Body (Section 2.1.2.2)).
Example: A message with a body:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<body>Wherefore art thou, Romeo?</body>
<body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
</message>
4.4 Specifying a Message Subject
A message stanza MAY contain one or more child <subject/> elements
specifying the topic of the message (see Subject (Section 2.1.2.1)).
Example: A message with a subject:
<message
to='romeo@example.net'
from='juliet@example.com/balcony'
type='chat'
xml:lang='en'>
<subject>I implore you!</subject>
<subject
xml:lang='cz'>&#x00DA;p&#x011B;nliv&#x011B; prosim!</subject>
<body>Wherefore art thou, Romeo?</body>
<body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
</message>
4.5 Specifying a Conversation Thread
A message stanza MAY contain a child <thread/> element specifying the
conversation thread in which the message is situated, for the purpose
of tracking the conversation (see Thread (Section 2.1.2.3)).
Example: A threaded conversation:
<message
to='romeo@example.net/orchard'
from='juliet@example.com/balcony'
type='chat'>
<body>Art thou not Romeo, and a Montague?</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
<message
to='juliet@example.com/balcony'
from='romeo@example.net/orchard'
type='chat'>
<body>Neither, fair saint, if either thee dislike.</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
<message
to='romeo@example.net/orchard'
from='juliet@example.com/balcony'
type='chat'>
<body>How cam'st thou hither, tell me, and wherefore?</body>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
5. Exchanging Presence Information
Exchanging presence information is made relatively straightforward
within XMPP by using presence stanzas. However, we see here a
contrast to the handling of messages: although a client MAY send
directed presence information to another entity, normally presence
information is sent from a client to its server (with no 'to'
address) and then broadcasted by the server to any entities that are
subscribed to the presence of the sending entity (in the terminology
of RFC 2778 [IMP-MODEL], we can say that the only watchers in XMPP
are subscribers). (Note: While presence information MAY be provided
on a user's behalf by an automated service, normally it is provided
by the user's client.)
For information regarding the syntax of presence stanzas as well as
their defined attributes and child elements, refer to [XMPP-CORE].
5.1 Client and Server Presence Responsibilities
After establishing a session, a client SHOULD (but is NOT REQUIRED
to) send initial presence to the server in order to signal its
availability for communications. As defined herein, the initial
presence stanza (1) MUST possess no 'to' address (signalling that it
is meant to be handled by the server on behalf of the client) and (2)
MUST possess no 'type' attribute (signalling the user's
availability). After sending initial presence, an active resource is
said to be an "available resource".
Upon receiving initial presence from a client, the user's server MUST
do the following if there is not already one or more available
resources for the user (if there is already one or more available
resources for the user, the server obviously does not need to send
the presence probes, since it already possesses the requisite
information):
1. Send presence probes (i.e., presence stanzas whose 'type'
attribute is set to a value of "probe") from the full JID (e.g.,
<user@example.com/resource>) of the user to the bare JID (e.g.,
<contact@example.org>) of any contacts to which the user is
subscribed in order to determine if they are available; such
contacts are those which are present in the user's roster with
the 'subscription' attribute set to a value of "to" or "both".
2. Broadcast initial presence from the full JID (e.g.,
<user@example.com/resource>) of the user to the bare JID (e.g.,
<contact@example.org>) of any contacts that are subscribed to the
user's presence; such contacts are those which are present in the
user's roster with the 'subscription' attribute set to a value of
"from" or "both".
In addition, the user's server MUST broadcast initial presence from
the user's new available resource to any of the user's existing
available resources (if any).
Upon receiving a presence probe from the user, the contact's server
SHOULD reply as follows:
1. If the user is not in the contact's roster with a subscription
state of "From", "From + Pending Out", or "Both" (as defined
under Subscription States (Section 9)), the contact's server MUST
return a presence stanza of type "error" in response to the
presence probe (however, if a server receives a presence probe
from a subdomain of the server's hostname or another such trusted
service, it MAY provide presence information about the user to
that entity). Specifically:
* if the user is in the contact's roster with a subscription
state of "None", "None + Pending Out", or "To", the contact's
server MUST return a <forbidden/> stanza error in response to
the presence probe.
* if the user is in the contact's roster with a subscription
state of "None + Pending In", "None + Pending Out/In", or "To
+ Pending In", the contact's server MUST return a
<not-authorized/> stanza error in response to the presence
probe.
2. Else, if the contact is blocking presence notifications to the
user's bare JID or full JID (using either a default list or
active list as defined under Blocking Outbound Presence
Notifications (Section 10.11)), the server MUST NOT reply to the
presence probe.
3. Else, if the contact has no available resources, the server MUST
either (1) reply to the presence probe by sending to the user the
full XML of the last presence stanza of type "unavailable"
received by the server from the contact, or (2) not reply at all.
4. Else, if the contact has at least one available resource, the
server MUST reply to the presence probe by sending to the user
the full XML of the last presence stanza received by the server
from each of the contact's available resources (again, subject to
privacy rules for each session).
Upon receiving initial presence from the user, the contact's server
MUST deliver the user's presence stanza to the full JIDs
(<contact@example.org/resource>) associated with all of the contact's
available resources, but only if the user is in the contact's roster
with a subscription state of "to" or "both" and the contact has not
blocked inbound presence notifications from the user's bare or full
JID (as defined under Blocking Inbound Presence Notifications
(Section 10.10)).
If the user's server receives a presence stanza of type "error" in
response to the initial presence that it sent to a contact on behalf
of the user, it SHOULD NOT send further presence updates to that
contact (until and unless it receives a presence stanza from the
contact).
After sending initial presence, the user MAY update its presence
information for broadcasting at any time during its session by
sending a presence stanza with no 'to' address and either no 'type'
attribute or a 'type' attribute with a value of "unavailable".
(Note: A user's client SHOULD NOT send a presence update to broadcast
information that changes independently of the user's presence and
availability.) If the presence stanza lacks a 'type' attribute (i.e.,
expresses availability), the user's server MUST broadcast the full
XML of that presence stanza to all contacts (1) that are in the
user's roster with a subscription type of "from" or "both", (2) to
whom the user has not blocked outbound presence, and (3) from whom
the server has not received a presence error during the user's
session (as well as to any of the user's other available resources).
If the presence stanza has a 'type' attribute set to a value of
"unavailable", the user's server MUST broadcast the full XML of that
presence stanza to all entities that fit the above description, as
well as to any entities to which the user has sent directed available
presence during the user's session (if the user has not yet sent
directed unavailable presence to that entity).
A user MAY send directed presence to another entity (i.e., a presence
stanza with a 'to' attribute whose value is the JID of the other
entity and with either no 'type' attribute or a 'type' attribute
whose value is "unavailable"). There are three possible cases:
1. If the user sends directed presence to a contact that is in the
user's roster with a subscription type of "from" or "both" after
having sent initial presence and before sending unavailable
presence broadcast, the user's server MUST route or deliver the
full XML of that presence stanza (subject to privacy rules) but
SHOULD NOT otherwise modify the contact's status regarding
presence broadcast (i.e., it SHOULD include the contact's JID in
any subsequent presence broadcasts initiated by the user).
2. If the user sends directed presence to an entity that is not in
the user's roster with a subscription type of "from" or "both"
after having sent initial presence and before sending unavailable
presence broadcast, the user's server MUST route or deliver the
full XML of that presence stanza to the entity but MUST NOT
modify the contact's status regarding available presence
broadcast (i.e., it MUST NOT include the entity's JID in any
subsequent broadcasts of available presence initiated by the
user); however, if the available resource from which the user
sent the directed presence become unavailable, the user's server
MUST broadcast that unavailable presence to the entity (if the
user has not yet sent directed unavailable presence to that
entity).
3. If the user sends directed presence without first sending initial
presence or after having sent unavailable presence broadcast
(i.e., the resource is active but not available), the user's
server MUST treat the entities to which the user sends directed
presence in the same way that it treats the entities listed in
case 2 above.
Before ending its session with a server, a client SHOULD gracefully
become unavailable by sending a final presence stanza that possesses
no 'to' attribute and that possesses a 'type' attribute whose value
is "unavailable" (optionally, the final presence stanza MAY contain
one or more <status/> elements specifying the reason why the user is
no longer available). However, the user's server MUST NOT depend on
receiving final presence from an available resource, since the
resource may become unavailable unexpectedly. If the user's server
detects that one of the user's resources has become unavailable for
any reason (either gracefully or ungracefully), it MUST broadcast
unavailable presence to all contacts (1) that are in the user's
roster with a subscription type of "from" or "both", (2) to whom the
user has not blocked outbound presence, and (3) from whom the server
has not received a presence error during the user's session; the
user's server MUST also send that unavailable presence stanza to any
of the user's other available resources, as well as to any entities
to which the user has sent directed presence during the user's
session for that resource (if the user has not yet sent directed
unavailable presence to that entity). Any presence stanza with no
'type' attribute and no 'to' attribute that is sent after sending
directed unavailable presence or broadcasted unavailable presence
MUST be broadcasted by the server to all subscribers.
5.2 Specifying Availability Status
A client MAY provide further information about its availability
status by using the <show/> element (see Show (Section 2.2.2.1)).
Example: Availability status:
<presence>
<show>dnd</show>
</presence>
5.3 Specifying Detailed Status Information
In conjunction with the <show/> element, a client MAY provide
detailed status information by using the <status/> element (see
Status (Section 2.2.2.2)).
Example: Detailed status information:
<presence xml:lang='en'>
<show>dnd</show>
<status>Wooing Juliet</status>
<status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
</presence>
5.4 Specifying Presence Priority
A client MAY provide a priority for its resource by using the
<priority/> element (see Priority (Section 2.2.2.3)).
Example: Presence priority:
<presence xml:lang='en'>
<show>dnd</show>
<status>Wooing Juliet</status>
<status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
<priority>1</priority>
</presence>
5.5 Presence Examples
The examples in this section illustrate the presence-related
protocols described above. The user is romeo@example.net, he has an
available resource whose resource identifier is "orchard", and he has
the following individuals in his roster:
o juliet@example.com (subscription="both" and she has two available
resources, one whose resource is "chamber" and another whose
resource is "balcony")
o benvolio@example.org (subscription="to")
o mercutio@example.org (subscription="from")
Example 1: User sends initial presence:
<presence/>
Example 2: User's server sends presence probes to contacts with
subscription="to" and subscription="both" on behalf of the user's
available resource:
<presence
type='probe'
from='romeo@example.net/orchard'
to='juliet@example.com'/>
<presence
type='probe'
from='romeo@example.net/orchard'
to='benvolio@example.org'/>
Example 3: User's server sends initial presence to contacts with
subscription="from" and subscription="both" on behalf of the user's
available resource:
<presence
from='romeo@example.net/orchard'
to='juliet@example.com'/>
<presence
from='romeo@example.net/orchard'
to='mercutio@example.org'/>
Example 4: Contacts' server replies to presence probe on behalf of
all of the contact's available resources:
<presence
from='juliet@example.com/balcony'
to='romeo@example.net/orchard'
xml:lang='en'>
<show>away</show>
<status>be right back</status>
<priority>0</priority>
</presence>
<presence
from='juliet@example.com/chamber'
to='romeo@example.net/orchard'>
<priority>1</priority>
</presence>
<presence
from='benvolio@example.org/pda'
to='romeo@example.net/orchard'
xml:lang='en'>
<show>dnd</show>
<status>gallivanting</status>
</presence>
Example 5: Contact's server delivers user's initial presence to all
of the contact's available resources or returns error to user:
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'/>
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/balcony'/>
<presence
type='error'
from='mercutio@example.org'
to='romeo@example.net/orchard'>
<error type='cancel'>
<gone xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</presence>
Example 6: User sends directed presence to another user not in his
roster:
<presence
from='romeo@example.net/orchard'
to='nurse@example.com'
xml:lang='en'>
<show>dnd</show>
<status>courting Juliet</status>
<priority>0</priority>
</presence>
Example 7: User sends updated available presence information for
broadcasting:
<presence xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
Example 8: Updated presence information is delivered only to one
contact (not those from whom an error was received or to whom the
user sent directed presence):
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'
xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
<presence
from='romeo@example.net/orchard'
to='juliet@example.com/balcony'
xml:lang='en'>
<show>away</show>
<status>I shall return!</status>
<priority>1</priority>
</presence>
Example 9: One of the contact's resources sends final presence:
<presence type='unavailable'/>
Example 10: Contact's server sends unavailable presence information
to user:
<presence
type='unavailable'
from='juliet@example.com/balcony'
to='romeo@example.net/orchard'/>
Example 11: User sends final presence:
<presence type='unavailable' xml:lang='en'>
<status>gone home</status>
</presence>
Example 12: Unavailable presence information is delivered to
contact's one remaining resource as well as to the person to whom the
user sent directed presence:
<presence
type='unavailable'
from='romeo@example.net/orchard'
to='juliet@example.com/chamber'
xml:lang='en'>
<status>gone home</status>
</presence>
<presence
from='romeo@example.net/orchard'
to='nurse@example.com'
xml:lang='en'>
<status>gone home</status>
</presence>
6. Managing Subscriptions
In order to protect the privacy of instant messaging users and any
other entities, presence and availability information is disclosed
only to other entities that the user has approved. When a user has
agreed that another entity may view its presence, the entity is said
to have a subscription to the user's presence information. A
subscription lasts across sessions; indeed, it lasts until the
subscriber unsubscribes or the subscribee cancels the
previously-granted subscription. Subscriptions are managed within
XMPP by sending presence stanzas containing specially-defined
attributes.
Note: There are important interactions between subscriptions and
rosters; these are defined under Integration of Roster Items and
Presence Subscriptions (Section 8), and the reader must refer to that
section for a complete understanding of presence subscriptions.
6.1 Requesting a Subscription
A request to subscribe to another entity's presence is made by
sending a presence stanza of type "subscribe".
Example: Sending a subscription request:
<presence to='juliet@example.com' type='subscribe'/>
If the subscription request is being sent to an instant messaging
contact, the JID supplied in the 'to' attribute SHOULD be of the form
<contact@example.org> rather than <contact@example.org/resource>,
since the desired result is normally for the user to receive presence
from all of the contact's resources, not merely the particular
resource specified in the 'to' attribute.
A user's server MUST NOT automatically approve subscription requests
on the user's behalf. All subscription requests MUST be directed to
the user's client, specifically to one or more available resources
associated with the user. If there is no available resource
associated with the user when the subscription request is received by
the user's server, the user's server MUST keep a record of the
subscription request and deliver the request when the user next
creates an available resource, until the user either approves or
denies the request. If there is more than one available resource
associated with the user when the subscription request is received by
the user's server, the user's server MUST broadcast that subscription
request to all available resources in accordance with Server Rules
for Handling XML Stanzas (Section 11). (Note: If an active resource
has not provided initial presence, the server MUST NOT consider it to
be available and therefore MUST NOT send subscription requests to
it.) However, f the user receives a presence stanza of type
"subscribe" from a contact to whom the user has already granted
permission to see the user's presence (e.g., in cases when the
contact is seeking to resynchronize subscription states), the user's
server SHOULD auto-reply on behalf of the user.
6.2 Handling a Subscription Request
When a client receives a subscription request from another entity, it
MUST either approve the request by sending a presence stanza of type
"subscribed" or refuse the request by sending a presence stanza of
type "unsubscribed".
Example: Approving a subscription request:
<presence to='romeo@example.net' type='subscribed'/>
Example: Refusing a presence subscription request:
<presence to='romeo@example.net' type='unsubscribed'/>
6.3 Cancelling a Subscription from Another Entity
If a user would like to cancel a previously-granted subscription
request, it sends a presence stanza of type "unsubscribed".
Example: Cancelling a previously granted subscription request:
<presence to='romeo@example.net' type='unsubscribed'/>
6.4 Unsubscribing from Another Entity's Presence
If a user would like to unsubscribe from the presence of another
entity, it sends a presence stanza of type "unsubscribe".
Example: Unsubscribing from an entity's presence:
<presence to='juliet@example.com' type='unsubscribe'/>
7. Roster Management
In XMPP, one's contact list is called a roster, which consists of any
number of specific roster items, each roster item being identified by
a unique JID (usually of the form <contact@example.org>). A user's
roster is stored by the user's server on the user's behalf so that
the user may access roster information from any resource.
Note: There are important interactions between rosters and
subscriptions; these are defined under Integration of Roster Items
and Presence Subscriptions (Section 8), and the reader must refer to
that section for a complete understanding of roster management.
7.1 Syntax and Semantics
Rosters are managed using IQ stanzas, specifically by means of a
<query/> child element qualified by the 'jabber:iq:roster' namespace.
The <query/> element MAY contain one or more <item/> children, each
describing a unique roster item or "contact".
The "key" or unique identifier for each roster item is a JID,
encapsulated in the required 'jid' attribute of the <item/> element.
The value of the 'jid' attribute SHOULD be of the form <user@domain>,
especially if the item is associated with another (human) instant
messaging user.
The state of the presence subscription in relation to a roster item
is captured in the 'subscription' attribute of the <item/> element.
Allowable values for this attribute are:
o "none" -- the user does not have a subscription to the contact,
and the contact does not have a subscription to the user
o "to" -- the user has a subscription to the contact, but the
contact does not have a subscription to the user
o "from" -- the contact has a subscription to the user, but the user
does not have a subscription to the contact
o "both" -- both the user and the contact have subscriptions to each
other
Each <item/> element MAY contain a 'name' attribute, which sets the
"nickname" to be associated with the JID, as determined by the user
(not the contact). The value of the 'name' attribute is opaque.
Each <item/> element MAY contain one or more <group/> child elements,
for use in collecting roster items into various categories. The
CDATA text of the <group/> element is opaque.
7.2 Business Rules
A server MUST ignore any 'to' address on a roster "set", and MUST
treat any roster "set" as applying to the sender. For added safety,
a client SHOULD check the "from" address of a roster "push" to ensure
that it is from a trusted source; specifically, the stanza MUST
either have no 'from' attribute (i.e., implicitly from the server) or
have a 'from' attribute whose value matches the user's bare JID (of
the form <user@domain>) or full JID (of the form <user@domain/
resource>); otherwise, the client SHOULD ignore the roster "push".
7.3 Retrieving One's Roster on Login
Upon connecting to the server, a client SHOULD request the roster
(however, because receiving the roster may not be desirable for all
resources, e.g., a connection with limited bandwidth, the client's
request for the roster is NOT REQUIRED). If an available resource
does not request the roster during a session, the server MUST NOT
send it presence subscriptions and associated roster updates.
Example: Client requests current roster from server:
<iq from='juliet@example.com/balcony' type='get' id='roster_1'>
<query xmlns='jabber:iq:roster'/>
</iq>
Example: Client receives roster from the server:
<iq to='juliet@example.com/balcony' type='result' id='roster_1'>
<query xmlns='jabber:iq:roster'>
<item jid='romeo@example.net'
name='Romeo'
subscription='both'>
<group>Friends</group>
</item>
<item jid='mercutio@example.org'
name='Mercutio'
subscription='from'>
<group>Friends</group>
</item>
<item jid='benvolio@example.org'
name='Benvolio'
subscription='both'>
<group>Friends</group>
</item>
</query>
</iq>
7.4 Adding a Roster Item
At any time, a user MAY add an item to his or her roster.
Example: Client adds a new item:
<iq from='juliet@example.com/balcony' type='set' id='roster_2'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'>
<group>Servants</group>
</item>
</query>
</iq>
The server MUST update the roster information in persistent storage,
and also push the change out to all of the user's available resources
that have requested the roster. This "roster push" consists of an IQ
set from the server to the client and enables all available resources
to remain in sync with the server-based roster information.
Example: Server (1) pushes the updated roster information to all
available resources that have requested the roster and (2) replies
with an IQ result to the sending resource:
<iq to='juliet@example.com/balcony' type='set'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'
subscription='none'>
<group>Servants</group>
</item>
</query>
</iq>
<iq to='juliet@example.com/chamber' type='set'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com'
name='Nurse'
subscription='none'>
<group>Servants</group>
</item>
</query>
</iq>
<iq to='juliet@example.com/balcony' type='result' id='roster_2'/>
Example: Connected resources reply with an IQ result to the server:
<iq from='juliet@example.com/balcony'
to='example.com'
type='result'/>
<iq from='juliet@example.com/chamber'
to='example.com'
type='result'/>
7.5 Updating a Roster Item
Updating an existing roster item (e.g., changing the group) is done
in the same way as adding a new roster item, i.e., by sending the
roster item in an IQ set to the server.
Example: User updates roster item (added group):
<iq from='juliet@example.com/chamber' type='set' id='roster_3'>
<query xmlns='jabber:iq:roster'>
<item jid='romeo@example.net'
name='Romeo'
subscription='both'>
<group>Friends</group>
<group>Lovers</group>
</item>
</query>
</iq>
As with adding a roster item, when updating a roster item the server
MUST update the roster information in persistent storage, and also
initiate a roster push to all of the user's available resources that
have requested the roster.
7.6 Deleting a Roster Item
At any time, a user MAY delete an item from its roster by doing an IQ
set and making sure that the value of the 'subscription' attribute is
"remove" (a compliant server MUST ignore any other values of the
'subscription' attribute when received from a client).
Example: Client removes an item:
<iq from='juliet@example.com/balcony' type='set' id='roster_4'>
<query xmlns='jabber:iq:roster'>
<item jid='nurse@example.com' subscription='remove'/>
</query>
</iq>
As with adding a roster item, when deleting a roster item the server
MUST update the roster information in persistent storage, initiate a
roster push to all of the user's available resources that have
requested the roster (with the 'subscription' attribute set to a
value of "remove"), and send an IQ result to the initiating resource.
For further information about the implications of this command, see
Removing a Roster Item and Cancelling All Subscriptions (Section
8.6).
8. Integration of Roster Items and Presence Subscriptions
8.1 Overview
Some level of integration between roster items and presence
subscriptions is normally expected by an instant messaging user
regarding the user's subscriptions to and from other contacts. This
section describes the level of integration that MUST be supported
within XMPP instant messaging applications.
There are four primary subscription states:
o None -- Neither the user nor the contact is subscribed to the
other's presence
o To -- The user is subscribed to the contact's presence but there
is no subscription from the contact to the user
o From -- There is a subscription from the contact to the user, but
the user has not subscribed to the contact's presence
o Both -- Both the user and the contact are subscribed to each
other's presence (i.e., the union of 'from' and 'to')
Each of these states is reflected in the roster of both the user and
the contact, thus resulting in durable subscription states.
Narrative explanations of how these subscription states interact with
roster items in order to complete certain defined use cases are
provided in the following sub-sections. Full details regarding
server and client handling of all subscription states (including
pending states between the primary states listed above) is provided
in Subscription States (Section 9).
If an active resource does not both send initial presence and request
the roster, the server MUST NOT send it presence subscription
requests or roster pushes.
The 'from' and 'to' addresses are OPTIONAL in roster pushes; if
included, their values SHOULD be the full JID of the resource for
that session. A client MUST acknowledge each roster push with an IQ
stanza of type "result" (for the sake of brevity, these stanzas are
not shown in the following examples but are required by [XMPP-CORE]).
8.2 User Subscribes to Contact
The process by which a user subscribes to a contact, including the
interaction between roster items and subscription states, is defined
below.
1. In preparation for being able to render the contact in the user's
client interface and for the server to keep track of the
subscription, the user's client SHOULD perform a "roster set" for
the new roster item. This request consists of an IQ stanza of
type='set' containing a <query/> element in the
'jabber:iq:roster' namespace, which in turn contains an <item/>
element that defines the new roster item; the <item/> element
MUST possess a 'jid' attribute, MAY possess a 'name' attribute,
MUST NOT possess a 'subscription' attribute, and MAY contain one
or more <group/> child elements:
<iq type='set' id='set1'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
2. As a result, the user's server (1) MUST initiate a roster push
for the new roster item to all available resources associated
with this user that have requested the roster, setting the
'subscription' attribute to a value of "none"; and (2) MUST reply
with an IQ result related to the roster set:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<iq type='result' id='set1'/>
3. If the user wants to request a subscription to the contact's
presence, the user's client MUST send a presence stanza of
type='subscribe' to the contact:
<presence to='contact@example.org' type='subscribe'/>
4. As a result, the user's server MUST initiate a second roster push
to all of the user's available resources that have requested the
roster, setting the contact to the pending sub-state of the
'none' subscription state; this pending sub-state is denoted by
the inclusion of the ask='subscribe' attribute in the roster
item:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
ask='subscribe'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
Note: If the user did not create a roster item before sending the
subscription request, the server MUST now create one on behalf of
the user with the 'subscription' attribute set to a value of
"none", then send a roster push to all of the user's available
resources that have requested the roster, absent the 'name'
attribute and the <group/> child.
5. The user's server MUST also stamp the presence stanza of type
"subscribe" with the user's bare JID (i.e., <user@example.com>)
as the 'from' address. If the contact is served by a different
host than the user, the user's server MUST route the presence
stanza to the contact's server for delivery to the contact (this
case is assumed throughout; however, if the contact is served by
the same host, then the server can simply deliver the presence
stanza directly):
<presence
from='user@example.com'
to='contact@example.org'
type='subscribe'/>
Note: If the user's server receives a presence stanza of type
"error" from the contact's server in response to the outgoing
presence stanza of type "subscribe", it MUST revert the
subscription state from the new state ("None + Pending Out") to
the previous state ("None"), and MUST deliver the error stanza to
the user.
6. Upon receiving the presence stanza of type "subscribe" addressed
to the contact, the contact's server MUST determine if there is
at least one available resource from which the contact has
requested the roster. If so, it MUST deliver the subscription
request to the contact (if not, the contact's server MUST store
the subscription request offline for delivery when this condition
is next met; normally this is done by adding a roster item for
the contact to the user's roster, with a state of "None + Pending
In" as defined under Subscription States (Section 9), however a
server SHOULD NOT push or deliver roster items in that state to
the user). No matter when the subscription request is delivered,
the contact must decide whether or not to approve it (subject to
configured preferences, the contact's client MAY approve or
refuse the subscription request without presenting it to the
contact). Here we assume the "happy path" that the contact
approves the subscription request (the alternate flow of
declining the subscription request is defined in Section 8.2.1).
In this case, the contact's client (1) SHOULD perform a roster
set specifying the desired nickname and group for the user (if
any); and (2) MUST send a presence stanza of type "subscribed" to
the user in order to approve the subscription request.
<iq type='set' id='set2'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence to='user@example.com' type='subscribed'/>
7. As a result, the contact's server (1) MUST initiate a roster push
to all available resources associated with the contact that have
requested the roster, containing a roster item for the user with
the subscription state set to 'from' (the server MUST send this
even if the contact did not perform a roster set); (2) MUST
return an IQ result related to the roster set; (3) MUST route the
presence stanza of type "subscribed" to the user; and (4) MUST
send available presence from all of the contact's available
resources to the user:
<iq type='set' to='contact@example.org/resource'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<iq type='result' to='contact@example.org/resource' id='set2'/>
<presence
from='contact@example.org/resource'
to='user@example.com'
type='subscribed'/>
<presence
from='contact@example.org/resource'
to='user@example.com'/>
Note: If the contact's server receives a presence stanza of type
"error" from the user's server in response to the outgoing
presence stanza of type "subscribed", it MUST revert the
subscription state from the new state ("From") to the previous
state ("None + Pending In"), and MUST deliver the error stanza to
the contact.
8. Upon receiving the presence stanza of type "subscribed" addressed
to the user, the user's server MUST first verify that the contact
is in the user's roster with either of the following states: (a)
subscription='none' and ask='subscribe' or (b)
subscription='from' and ask='subscribe'. If the contact is not
in the user's roster with either of those states, the user's
server MUST silently ignore the presence stanza of type
"subscribed" (i.e., it MUST NOT route it to the user, modify the
user's roster, or generate a roster push to the user's available
resources). If the contact is in the user's roster with either
of those states, the user's server (1) MUST deliver the presence
stanza of type "subscribed" from the contact to the user; (2)
MUST initiate a roster push to all of the user's available
resources that have requested the roster, containing an updated
roster item for the contact with the 'subscription' attribute set
to a value of "to"; and (3) MUST deliver the available presence
stanza received from each of the contact's available resources to
each of the user's available resources:
<presence
to='user@example.com'
from='contact@example.org'
type='subscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='to'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org/resource'
to='user@example.com/resource'/>
9. Upon receiving the presence stanza of type "subscribed", the user
SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "subscribe" to the contact or "denying" it by
sending a presence stanza of type "unsubscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
From the perspective of the user, there now exists a subscription to
the contact; from the perspective of the contact, there now exists a
subscription from the user. (Note: If at this point the user sends
another subscription request to the contact, the user's server MUST
silently ignore that request.)
8.2.1 Alternate Flow: Contact Declines Subscription Request
The above activity flow represents the "happy path" related to the
user's subscription request to the contact. The main alternate flow
occurs if the contact refuses the user's subscription request.
1. If the contact wants to refuse the request, the contact's client
MUST send a presence stanza of type "unsubscribed" to the user
(instead of the presence stanza of type "subscribed" sent in Step
6 of Section 8.2):
<presence to='user@example.com' type='unsubscribed'/>
2. As a result, the contact's server MUST route the presence stanza
of type "unsubscribed" to the user, first stamping the 'from'
address as the bare JID (<contact@example.org>) of the contact:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
Note: if the contact's server previously added the user to the
contact's roster for tracking purposes, it MUST remove the
relevant item at this time.
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST deliver that
presence stanza to the user and (2) MUST initiate a roster push
to all of the user's available resources that have requested the
roster, containing an updated roster item for the contact with
the 'subscription' attribute set to a value of "none" and with no
'ask' attribute:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
As a result of this activity, the contact is now in the user's roster
with a subscription state of "none", whereas the user is not in the
contact's roster at all.
8.3 Creating a Mutual Subscription
The user and contact can build on the foregoing to create a mutual
subscription (i.e., a subscription of type "both"). The process is
defined below.
1. If the contact wants to create a mutual subscription, the contact
MUST send a subscription request to the user (subject to
configured preferences, the contact's client MAY send this
automatically):
<presence to='user@example.com' type='subscribe'/>
2. As a result, the contact's server (1) MUST initiate a roster push
to all available resources associated with the contact that have
requested the roster, with the user still in the 'from'
subscription state but with a pending 'to' subscription denoted
by the inclusion of the ask='subscribe' attribute in the roster
item; and (2) MUST route the presence stanza of type "subscribe"
to the user, first stamping the 'from' address as the bare JID
(<contact@example.org>) of the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
ask='subscribe'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='subscribe'/>
Note: If the contact's server receives a presence stanza of type
"error" from the user's server in response to the outgoing
presence stanza of type "subscribe", it MUST revert the
subscription state from the new state ("From + Pending Out") to
the previous state ("From"), and MUST deliver the error stanza to
the contact.
3. Upon receiving the presence stanza of type "subscribe" addressed
to the user, the user's server must determine if there is at
least one available resource for which the user has requested the
roster. If so, the user's server MUST deliver the subscription
request to the user (if not, it MUST store the subscription
request offline for delivery when this condition is next met).
No matter when the subscription request is delivered, the user
must then decide whether or not to approve it (subject to
configured preferences, the user's client MAY approve or refuse
the subscription request without presenting it to the user).
Here we assume the "happy path" that the user approves the
subscription request (the alternate flow of declining the
subscription request is defined in Section 8.3.1). In this case,
the user's client MUST send a presence stanza of type
"subscribed" to the contact in order to approve the subscription
request.
<presence to='contact@example.org' type='subscribed'/>
4. As a result, the user's server (1) MUST initiate a roster push to
all of the user's available resources that have requested the
roster, containing a roster item for the contact with the
'subscription' attribute set to a value of "both"; (2) MUST route
the presence stanza of type "subscribed" to the contact, first
stamping the 'from' address as the bare JID (<user@example.com>)
of the user; and (3) MUST send available presence from each of
the user's available resources to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='both'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='subscribed'/>
<presence
from='user@example.com/resource'
to='contact@example.org'/>
Note: If the user's server receives a presence stanza of type
"error" from the contact's server in response to the outgoing
presence stanza of type "subscribed", it MUST revert the
subscription state from the new state ("Both") to the previous
state ("To + Pending In"), and MUST deliver the error stanza to
the user.
5. Upon receiving the presence stanza of type "subscribed" addressed
to the contact, the contact's server MUST first verify that the
user is in the contact's roster with either of the following
states: (a) subscription='none' and ask='subscribe' or (b)
subscription='from' and ask='subscribe'. If the user is not in
the contact's roster with either of those states, the contact's
server MUST silently ignore the presence stanza of type
"subscribed" (i.e., it MUST NOT route it to the contact, modify
the contact's roster, or generate a roster push to the contact's
available resources). If the user is in the contact's roster
with either of those states, the contact's server (1) MUST
deliver the presence stanza of type "subscribed" from the user to
the contact; (2) MUST initiate a roster push to all available
resources associated with the contact that have requested the
roster, containing an updated roster item for the user with the
'subscription' attribute set to a value of "both"; and (3) MUST
deliver the available presence stanza received from each of the
user's available resources to each of the contact's available
resources:
<presence
from='user@example.com'
to='contact@example.org'
type='subscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='both'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com/resource'
to='contact@example.org/resource'/>
6. Upon receiving the presence stanza of type "subscribed", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "subscribe" to the user or "denying" it by sending
a presence stanza of type "unsubscribe" to the user; this step
does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
The user and the contact now have a mutual subscription to each
other's presence -- i.e., the subscription is of type "both". The
user's server MUST now send the user's current presence information
to the contact. (Note: If at this point the user sends a
subscription request to the contact or the contact sends a
subscription request to the user, the sending user's server MUST
silently ignore that request and not route it to the intended
recipient.)
8.3.1 Alternate Flow: User Declines Subscription Request
The above activity flow represents the "happy path" related to the
contact's subscription request to the user. The main alternate flow
occurs if the user refuses the contact's subscription request.
1. If the user wants to refuse the request, the user's client MUST
send a presence stanza of type "unsubscribed" to the contact
(instead of the presence stanza of type "subscribed" sent in Step
3 of Section 8.3):
<presence to='contact@example.org' type='unsubscribed'/>
2. As a result, the user's server MUST route the presence stanza of
type "unsubscribed" to the contact, first stamping the 'from'
address as the bare JID (<user@example.com>) of the user:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the contact, the contact's server (1) MUST deliver
that presence stanza to the contact; and (2) MUST initiate a
roster push to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "from" and with no 'ask' attribute:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='from'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
4. Upon receiving the presence stanza of type "unsubscribed", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the user or "denying" it by
sending a presence stanza of type "subscribe" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
As a result of this activity, there has been no change in the
subscription state; i.e., the contact is in the user's roster with a
subscription state of "to" and the user is in the contact's roster
with a subscription state of "from".
8.4 Unsubscribing
At any time after subscribing to a contact's presence, a user MAY
unsubscribe. While the XML that the user sends to make this happen
is the same in all instances, the subsequent subscription state is
different depending on the subscription state obtaining when the
unsubscribe "command" is sent. Both possible scenarios are defined
below.
8.4.1 Case #1: Unsubscribing When Subscription is Not Mutual
In the first case, the user has a subscription to the contact but the
contact does not have a subscription to the user (i.e., the
subscription is not yet mutual).
1. If the user wants to unsubscribe from the contact's presence, the
user MUST send a presence stanza of type "unsubscribe" to the
contact:
<presence to='contact@example.org' type='unsubscribe'/>
2. As a result, the user's server (1) MUST send a roster push to all
of the user's available resources that have requested the roster,
containing an updated roster item for the contact with the
'subscription' attribute set to a value of "none"; and (2) MUST
route the presence stanza of type "unsubscribe" to the contact,
first stamping the 'from' address as the bare JID
(<user@example.com>) of the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
3. Upon receiving the presence stanza of type "unsubscribe"
addressed to the contact, the contact's server (1) MUST initiate
a roster push to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "none" (if the contact is offline, the contact's
server MUST modify the roster item and send that modified item
the next time the contact requests the roster); and (2) MUST
deliver the "unsubscribe" state change notification to the
contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
4. Upon receiving the presence stanza of type "unsubscribe", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribed" to the user or "denying" it by
sending a presence stanza of type "subscribed" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
5. The contact's server then (1) MUST send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
6. When the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
7. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
8.4.2 Case #2: Unsubscribing When Subscription is Mutual
In the second case, the user has a subscription to the contact and
the contact also has a subscription to the user (i.e., the
subscription is mutual).
1. If the user wants to unsubscribe from the contact's presence, the
user MUST send a presence stanza of type "unsubscribe" to the
contact:
<presence to='contact@example.org' type='unsubscribe'/>
2. As a result, the user's server (1) MUST send a roster push to all
of the user's available resources that have requested the roster,
containing an updated roster item for the contact with the
'subscription' attribute set to a value of "from"; and (2) MUST
route the presence stanza of type "unsubscribe" to the contact,
first stamping the 'from' address as the bare JID
(<user@example.com>) of the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='from'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
3. Upon receiving the presence stanza of type "unsubscribe"
addressed to the contact, the contact's server (1) MUST initiate
a roster push to all available resources associated with the
contact that have requested the roster, containing an updated
roster item for the user with the 'subscription' attribute set to
a value of "to" (if the contact is offline, the contact's server
MUST modify the roster item and send that modified item the next
time the contact requests the roster); and (2) MUST deliver the
"unsubscribe" state change notification to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
4. Upon receiving the presence stanza of type "unsubscribe", the
contact SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribed" to the user or "denying" it by
sending a presence stanza of type "subscribed" to the user; this
step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the contact's server know that it MUST no longer send
notification of the subscription state change to the contact (see
Section 9.4).
5. The contact's server then (1) MUST send a presence stanza of type
"unsubscribed" to the user; and (2) SHOULD send unavailable
presence from the contact to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
6. When the user's server receives a presence stanza of type
"unsubscribed" and/or unavailable presence, it MUST deliver them
to the user:
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
7. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
Note: Obviously this does not result in removal of the roster item
from the user's roster, and the contact still has a subscription to
the user's presence. In order to both completely cancel a mutual
subscription and fully remove the roster item from the user's roster,
the user SHOULD update the roster item with subscription='remove' as
defined under Removing a Roster Item and Cancelling All Subscriptions
(Section 8.6).
8.5 Cancelling a Subscription
At any time after approving a subscription request from a user, a
contact MAY cancel that subscription. While the XML that the contact
sends to make this happen is the same in all instances, the
subsequent subscription state is different depending on the
subscription state obtaining when the cancellation was sent. Both
possible scenarios are defined below.
8.5.1 Case #1: Cancelling When Subscription is Not Mutual
In the first case, the user has a subscription to the contact but the
contact does not have a subscription to the user (i.e., the
subscription is not yet mutual).
1. If the contact wants to cancel the user's subscription, the
contact MUST send a presence stanza of type "unsubscribed" to the
user:
<presence to='user@example.com' type='unsubscribed'/>
2. As a result, the contact's server (1) MUST send a roster push to
all of the contact's available resources that have requested the
roster, containing an updated roster item for the user with the
'subscription' attribute set to a value of "none"; (2) MUST route
the presence stanza of type "unsubscribed" to the user, first
stamping the 'from' address as the bare JID
(<contact@example.org>) of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST initiate a
roster push to all of the user's available resources that have
requested the roster, containing an updated roster item for the
contact with the 'subscription' attribute set to a value of
"none" (if the user is offline, the user's server MUST modify the
roster item and send that modified item the next time the user
requests the roster); (2) MUST deliver the "unsubscribed" state
change notification to the user; and (3) MUST deliver the
unavailable presence to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='none'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
8.5.2 Case #2: Cancelling When Subscription is Mutual
In the second case, the user has a subscription to the contact and
the contact also has a subscription to the user (i.e., the
subscription is mutual).
1. If the contact wants to cancel the user's subscription, the
contact MUST send a presence stanza of type "unsubscribed" to the
user:
<presence to='user@example.com' type='unsubscribed'/>
2. As a result, the contact's server (1) MUST send a roster push to
all of the contact's available resources that have requested the
roster, containing an updated roster item for the user with the
'subscription' attribute set to a value of "to"; (2) MUST route
the presence stanza of type "unsubscribed" to the user, first
stamping the 'from' address as the bare JID
(<contact@example.org>) of the contact; and (3) SHOULD send
unavailable presence from the contact to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
3. Upon receiving the presence stanza of type "unsubscribed"
addressed to the user, the user's server (1) MUST initiate a
roster push to all of the user's available resources that have
requested the roster, containing an updated roster item for the
contact with the 'subscription' attribute set to a value of
"from" (if the user is offline, the user's server MUST modify the
roster item and send that modified item the next time the user
requests the roster); and (2) MUST deliver the "unsubscribed"
state change notification to the user; and (3) MUST deliver the
unavailable presence to the user:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='from'
name='MyContact'>
<group>MyBuddies</group>
</item>
</query>
</iq>
<presence
from='contact@example.org'
to='user@example.com'
type='unsubscribed'/>
<presence
from='contact@example.org'
to='user@example.com'
type='unavailable'/>
4. Upon receiving the presence stanza of type "unsubscribed", the
user SHOULD acknowledge receipt of that subscription state
notification through either "affirming" it by sending a presence
stanza of type "unsubscribe" to the contact or "denying" it by
sending a presence stanza of type "subscribe" to the contact;
this step does not necessarily affect the subscription state (see
Subscription States (Section 9) for details), but instead lets
the user's server know that it MUST no longer send notification
of the subscription state change to the user (see Section 9.4).
Note: Obviously this does not result in removal of the roster item
from the contact's roster, and the contact still has a subscription
to the user's presence. In order to both completely cancel a mutual
subscription and fully remove the roster item from the contact's
roster, the contact should update the roster item with
subscription='remove' as defined under Removing a Roster Item and
Cancelling All Subscriptions (Section 8.6).
8.6 Removing a Roster Item and Cancelling All Subscriptions
Because there may be many steps involved in completely removing a
roster item and cancelling subscriptions in both directions, the
roster management protocol includes a "shortcut" method for doing so.
The process may be initiated no matter what the current subscription
state is by sending a roster set containing an item for the contact
with the 'subscription' attribute set to a value of "remove":
<iq type='set' id='remove1'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='remove'/>
</query>
</iq>
When the user removes a contact from his or her roster by setting the
'subscription' attribute to a value of "remove", the user's server
(1) MUST automatically cancel any existing presence subscription
between the user and the contact (both 'to' and 'from' as
appropriate); (2) MUST remove the roster item from the user's roster
and inform all of the user's available resources that have requested
the roster of the roster item removal; (3) MUST inform the resource
that initiated the removal of success; and (4) SHOULD send
unavailable presence to the contact:
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='contact@example.org'
subscription='remove'/>
</query>
</iq>
<iq type='result' id='remove1'/>
<presence
from='user@example.com'
to='contact@example.org'
type='unavailable'/>
Upon receiving the presence stanza of type "unsubscribe", the
contact's server (1) MUST initiate a roster push to all available
resources associated with the contact that have requested the roster,
containing an updated roster item for the user with the
'subscription' attribute set to a value of "to" (if the contact is
offline, the contact's server MUST modify the roster item and send
that modified item the next time the contact requests the roster);
and (2) MUST also deliver the "unsubscribe" state change notification
to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='to'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribe'/>
Upon receiving the presence stanza of type "unsubscribed", the
contact's server (1) MUST initiate a roster push to all available
resources associated with the contact that have requested the roster,
containing an updated roster item for the user with the
'subscription' attribute set to a value of "none" (if the contact is
offline, the contact's server MUST modify the roster item and send
that modified item the next time the contact requests the roster);
and (2) MUST also deliver the "unsubscribe" state change notification
to the contact:
<iq type='set'>
<query xmlns='jabber:iq:roster'>
<item
jid='user@example.com'
subscription='none'
name='SomeUser'>
<group>SomeGroup</group>
</item>
</query>
</iq>
<presence
from='user@example.com'
to='contact@example.org'
type='unsubscribed'/>
Upon receiving the presence stanza of type "unavailable" addressed to
the contact, the contact's server MUST deliver the unavailable
presence to the user:
<presence
from='user@example.com'
to='contact@example.org'
type='unavailable'/>
Note that when the user removes the contact from the user's roster,
the end state of the contact's roster is that the user is still in
the contact's roster with a subscription state of "none"; in order to
completely remove the roster item for the user, the contact needs to
also send a roster removal request.
9. Subscription States
This section provides detailed information about subscription states
and server handling of subscription-related presence stanzas (i.e.,
presence stanzas of type "subscribe", "subscribed", "unsubscribe",
and "unsubscribed").
9.1 Defined States
There are nine possible subscription states, which are described here
from the user's (not contact's) perspective:
1. "None" = contact and user are not subscribed to each other, and
neither has requested a subscription from the other
2. "None + Pending Out" = contact and user are not subscribed to
each other, and user has sent contact a subscription request but
contact has not replied yet
3. "None + Pending In" = contact and user are not subscribed to each
other, and contact has sent user a subscription request but user
has not replied yet (note: contact's server SHOULD NOT push or
deliver roster items in this state, but instead SHOULD wait until
contact has approved subscription request from user)
4. "None + Pending Out/In" = contact and user are not subscribed to
each other, contact has sent user a subscription request but user
has not replied yet, and user has sent contact a subscription
request but contact has not replied yet
5. "To" = user is subscribed to contact (one-way)
6. "To + Pending In" = user is subscribed to contact, and contact
has send user a subscription request but user has not replied yet
7. "From" = contact is subscribed to user (one-way)
8. "From + Pending Out" = contact is subscribed to user, and user
has sent contact a subscription request but contact has not
replied yet
9. "Both" = user and contact are subscribed to each other (two-way)
9.2 Server Handling of Outbound Presence Subscription Stanzas
Outbound presence subscription stanzas enable the user to manage his
or her subscription to the contact (via the "subscribe" and
"unsubscribe" types), and to manage the contact's access to the
user's presence information (via the "subscribed" and "unsubscribed"
types).
Because it is possible for the user's server and the contact's server
to lose synchronization regarding subscription states, the user's
server MUST route all outbound presence stanzas of type "subscribe"
or "unsubscribe" to the contact so that the user is able to
resynchronize his or her subscription to the contact if needed.
The user's server SHOULD NOT route a presence stanza of type
"subscribed" or "unsubscribed" to the contact if the stanza does not
result in a subscription state change from the user's perspective,
and MUST NOT make a state change. If the stanza results in a
subscription state change, the user's server MUST route the stanza to
the contact and MUST make the appropriate state change. These rules
are summarized in the following tables.
Table 1: Recommended handling of outbound "subscribed" stanzas
+----------------------------------------------------------------+
| EXISTING STATE | ROUTE? | NEW STATE |
+----------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes | "From" |
| "None + Pending Out/In" | yes | "From + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes | "Both" |
| "From" | no | no state change |
| "From + Pending Out" | no | no state change |
| "Both" | no | no state change |
+----------------------------------------------------------------+
Table 2: Recommended handling of outbound "unsubscribed" stanzas
+----------------------------------------------------------------+
| EXISTING STATE | ROUTE? | NEW STATE |
+----------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes | "None" |
| "None + Pending Out/In" | yes | "None + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes | "To" |
| "From" | yes | "None" |
| "From + Pending Out" | yes | "None + Pending Out" |
| "Both" | yes | "To" |
+----------------------------------------------------------------+
9.3 Server Handling of Inbound Presence Subscription Stanzas
Inbound presence subscription stanzas request a subscription-related
action from the user (via the "subscribe" type), inform the user of
subscription-related actions taken by the contact (via the
"unsubscribe" type), or enable the user to manage the contact's
access to the user's presence information (via the "subscribed" and
"unsubscribed" types).
When the user's server receives a subscription request for the user
from the contact (i.e., a presence stanza of type "subscribe"), it
MUST deliver that request to the user for approval if the user has
not already granted the contact access to the user's presence
information and if there is no pending inbound subscription request;
however, the user's server SHOULD NOT deliver the new request if
there is a pending inbound subscription request, since the previous
subscription request will have been recorded. If the user has
already granted the contact access to the user's presence
information, the user's server SHOULD auto-reply to an inbound
presense stanza of type "subscribe" from the contact by sending a
presence stanza of type "subscribed" to the contact on behalf of the
user; this rule enables the contact to resynchronize the subscription
state if needed. These rules are summarized in the following table.
Table 3: Recommended handling of inbound "subscribe" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | yes | "None + Pending In" |
| "None + Pending Out" | yes | "None + Pending Out/In" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | no | no state change |
| "To" | yes | "To + Pending In" |
| "To + Pending In" | no | no state change |
| "From" | no * | no state change |
| "From + Pending Out" | no * | no state change |
| "Both" | no * | no state change |
+------------------------------------------------------------------+
* Server SHOULD auto-reply with "subscribed" stanza
When the user's server receives a presence stanza of type
"unsubscribe" for the user from the contact, if the stanza results in
a subscription state change from the user's perspective then the
user's server SHOULD auto-reply by sending a presence stanza of type
"unsubscribed" to the contact on behalf of the user, MUST deliver the
"unsubscribe" stanza to the user, and MUST change the state. If no
subscription state change results, the user's server SHOULD NOT
deliver the stanza and MUST NOT change the state. These rules are
summarized in the following table.
Table 4: Recommended handling of inbound "unsubscribe" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | no | no state change |
| "None + Pending In" | yes * | "None" |
| "None + Pending Out/In" | yes * | "None + Pending Out" |
| "To" | no | no state change |
| "To + Pending In" | yes * | "To" |
| "From" | yes * | "None" |
| "From + Pending Out" | yes * | "None + Pending Out |
| "Both" | yes * | "To" |
+------------------------------------------------------------------+
* Server SHOULD auto-reply with "unsubscribed" stanza
When the user's server receives a presence stanza of type
"subscribed" for the user from the contact, it MUST NOT deliver the
stanza to the user and MUST NOT change the subscription state if
there is no pending outbound request for access to the contact's
presence information. If there is a pending outbound request for
access to the contact's presence information and the inbound presence
stanza of type "subscribed" results in a subscription state change,
the user's server MUST deliver the stanza to the user and MUST change
the subscription state. If the user already has access to the
contact's presence information, the inbound presence stanza of type
"subscribed" does not result in a subscription state change;
therefore the user's server SHOULD NOT deliver the stanza to the user
and MUST NOT change the subscription state. These rules are
summarized in the following table.
Table 5: Recommended handling of inbound "subscribed" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | yes | "To" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | yes | "To + Pending In" |
| "To" | no | no state change |
| "To + Pending In" | no | no state change |
| "From" | no | no state change |
| "From + Pending Out" | yes | "Both" |
| "Both" | no | no state change |
+------------------------------------------------------------------+
When the user's server receives a presence stanza of type
"unsubscribed" for the user from the contact, it MUST deliver the
stanza to the user and MUST change the subscription state if there is
a pending outbound request for access to the contact's presence
information or if the user currently has access to the contact's
presence information. Otherwise, the user's server SHOULD NOT
deliver the stanza and MUST NOT change the subscription state. These
rules are summarized in the following table.
Table 6: Recommended handling of inbound "unsubscribed" stanzas
+------------------------------------------------------------------+
| EXISTING STATE | DELIVER? | NEW STATE |
+------------------------------------------------------------------+
| "None" | no | no state change |
| "None + Pending Out" | yes | "None" |
| "None + Pending In" | no | no state change |
| "None + Pending Out/In" | yes | "None + Pending In" |
| "To" | yes | "None" |
| "To + Pending In" | yes | "None + Pending In" |
| "From" | no | no state change |
| "From + Pending Out" | yes | "From" |
| "Both" | yes | "From" |
+------------------------------------------------------------------+
9.4 Server Delivery and Client Acknowledgement of Subscription State
Change Notifications
When a server receives an inbound presence stanza of type
"subscribe", "subscribed", "unsubscribe", or "unsubscribed" that
consists of a subscription state change request or notification, in
addition to sending the appropriate roster push (or updated roster
when the roster is next requested), it MUST deliver the request or
notification to the intended recipient at least once. A server MAY
require the recipient to acknowledge receipt of all state change
notifications (and MUST require acknowledgement in the case of
subscription requests, i.e., presence stanzas of type "subscribe").
In order to require acknowledgement, a server SHOULD send the
notification to the recipient each time the recipient logs in, until
the recipient acknowledges receipt of the notification by "affirming"
or "denying" the notification, as shown in the following table:
Table 7: Acknowledgement of subscription state change notifications
+--------------------------------------------------+
| STANZA TYPE | ACCEPT | DENY |
+--------------------------------------------------+
| subscribe | subscribed | unsubscribed |
| subscribed | subscribe | unsubscribe |
| unsubscribe | unsubscribed | subscribed |
| unsubscribed | unsubscribe | subscribe |
+--------------------------------------------------+
Obviously, given the foregoing subscription state charts, some of the
acknowledgement stanzas will be routed to the contact and result in
subscription state changes, while others will not. However, any such
stanzas MUST result in the server's no longer sending the
subscription state notification to the user.
Because a user's server MUST automatically generate outbound presence
stanzas of type "unsubscribe" and "unsubscribed" upon receiving a
roster set with the 'subscription' attribute set to a value of
"remove" (see Removing a Roster Item and Cancelling All Subscriptions
(Section 8.6)), the server MUST treat a roster remove request as
equivalent to sending both of those presence stanzas for purposes of
determining whether to continue sending subscription state change
notifications of type "subscribe" or "subscribed" to the user.
10. Blocking Communication
Most instant messaging systems have found it necessary to implement
some method for users to block communications from particular other
users (this is also required by sections 5.1.5, 5.1.15, 5.3.2, and
5.4.10 of [IMP-REQS]). In XMPP this is done using the
'jabber:iq:privacy' namespace by managing one's privacy lists.
Server-side privacy lists enable successful completion of the
following use cases:
o Retrieving one's privacy lists.
o Adding, removing, and editing one's privacy lists.
o Setting, changing, or declining active lists.
o Setting, changing, or declining the default list (i.e., the list
that is active by default).
o Allowing or blocking messages based on JID, group, or subscription
type (or globally).
o Allowing or blocking inbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or blocking outbound presence notifications based on JID,
group, or subscription type (or globally).
o Allowing or blocking IQs based on JID, group, or subscription type
(or globally).
o Allowing or blocking all communications based on JID, group, or
subscription type (or globally).
Note: presence notifications do not include presence subscriptions,
only presence information that is broadcasted to entities that are
subscribed to a user's presence information. Thus this includes
presence stanzas with no 'type' attribute or of type='unavailable'
only.
10.1 Syntax and Semantics
A user MAY define one or more privacy lists, which are stored by the
user's server. Each <list/> element contains one or more rules in
the form of <item/> elements, and each <item/> element uses
attributes to define a privacy rule type, a specific value to which
the rules applies, the relevant action, and the place of the item in
the processing order.
The syntax is as follows:
<iq>
<query xmlns='jabber:iq:privacy'>
<list name='foo'>
<item
type='[jid|group|subscription]'
value='bar'
action='[allow|deny]'
order='unsignedInt'>
[<message/>]
[<presence-in/>]
[<presence-out/>]
[<iq/>]
</item>
</list>
</query>
</iq>
If the type is "jid", then the 'value' attribute MUST contain a valid
Jabber ID. JIDs are matched in the following order: <user@domain/
resource>, then <user@domain>, then <domain/resource>, then <domain>.
If the value is <user@domain>, then any resource for that user@domain
matches. If the value is <domain/resource>, then only that resource
matches. If the value is <domain>, then any user@domain (or
subdomain) matches.
If the type is "group", then the 'value' attribute SHOULD contain the
name of a group in the user's roster. (If a client attempts to
update, create, or delete a list item with a group that is not in the
user's roster, the server SHOULD return to the client an
<item-not-found/> stanza error.)
If the type is "subscription", then the 'value' attribute MUST be one
of "both", "to", "from", or "none" as defined under Roster Syntax and
Semantics (Section 7.1).
If no 'type' attribute is included, the rule provides the
"fall-through" case.
The 'action' attribute MUST be included and its value MUST be either
"accept" or "deny".
The 'order' attribute MUST be included and its value MUST be a
non-negative integer that is unique among all items in the list. (If
a client attempts to create or update a list with non-unique order
values, the server MUST return to the client a <bad-request/> stanza
error.)
The <item/> element MAY contain one or more child elements that
enable an entity to specify more granular control over which kinds of
stanzas are to be blocked (i.e., rather than blocking all stanzas).
The allowable child elements are:
o <message/> -- blocks incoming message stanzas
o <iq/> -- blocks incoming IQ stanzas
o <presence-in/> -- blocks incoming presence notifications
o <presence-out/> -- blocks outgoing presence notifications
Within the 'jabber:iq:privacy' namespace, the <query/> child of a
client-generated IQ stanza of type "set" MUST NOT include more than
one child element (i.e., the stanza must contain only one <active/>
element, one <default/> element, or one <list/> element); if a client
violates this rule, the server MUST return to the client a
<bad-request/> stanza error.
When a client adds or updates a privacy list, the <list/> element
SHOULD contain at least one <item/> child element; when a client
removes a privacy list, the <list/> element SHOULD contain no <item/>
child element.
When a client updates a privacy list, it must include all of the
desired items (i.e., not a "delta").
10.2 Business Rules
1. If there is an active list set for a session, it affects only
the session for which it is activated, and only for the duration
of the session. The server MUST apply the active list only and
MUST NOT apply the default list.
2. The default list applies to the user as a whole, and is
processed if there is no active list set for the target session/
resource to which a stanza is addressed, or if there are no
current sessions for the user.
3. If there is no active list set for a session (or there are no
current sessions for the user), and there is no default list,
then all stanzas SHOULD BE accepted or appropriately processed
by the server on behalf of the user.
4. Privacy lists MUST be the first rule applied by a server,
superseding (1) the routing and delivery rules specified in
Server Rules for Handling XML Stanzas (Section 11), and (2) the
handling of subscription-related presence stanzas (and
corresponding generation of roster pushes) specified in
Integration of Roster Items and Presence Subscriptions (Section
8).
5. The order in which privacy list items are processed by the
server is important. List items MUST be processed in ascending
order determined by the integer values of the 'order' attribute
for each <item/>.
6. As soon as a stanza is matched against a privacy list, the
server SHOULD appropriately handle the stanza and cease
processing.
7. If no fall-through item is provided in a list, the fall-through
action is assumed to be "accept".