draft-ietf-xmpp-core-07.txt   draft-ietf-xmpp-core-08.txt 
Network Working Group P. Saint-Andre Network Working Group P. Saint-Andre
Internet-Draft J. Miller Internet-Draft J. Miller
Expires: October 1, 2003 Jabber Software Foundation Expires: October 6, 2003 Jabber Software Foundation
April 2, 2003 April 7, 2003
XMPP Core XMPP Core
draft-ietf-xmpp-core-07 draft-ietf-xmpp-core-08
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
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document describes the core features of the Extensible Messaging This document describes the core features of the Extensible Messaging
and Presence Protocol (XMPP), a protocol for streaming XML elements and Presence Protocol (XMPP), a protocol for streaming XML elements
in order to exchange messages and presence information in close to in order to exchange messages and presence information in close to
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Intellectual Property Notice . . . . . . . . . . . . . . . . 5 1.4 Intellectual Property Notice . . . . . . . . . . . . . . . . 5
2. Generalized Architecture . . . . . . . . . . . . . . . . . . 6 2. Generalized Architecture . . . . . . . . . . . . . . . . . . 6
2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Server . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Server . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Client . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 Client . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4 Gateway . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Gateway . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.5 Network . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.5 Network . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . 8 3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . 8
3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Domain Identifier . . . . . . . . . . . . . . . . . . . . . 8 3.2 Domain Identifier . . . . . . . . . . . . . . . . . . . . . 8
3.3 Node Identifier . . . . . . . . . . . . . . . . . . . . . . 8 3.3 Node Identifier . . . . . . . . . . . . . . . . . . . . . . 8
3.4 Resource Identifier . . . . . . . . . . . . . . . . . . . . 9 3.4 Resource Identifier . . . . . . . . . . . . . . . . . . . . 9
4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . 10 4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2 Stream Attributes . . . . . . . . . . . . . . . . . . . . . 11 4.2 Stream Attributes . . . . . . . . . . . . . . . . . . . . . 11
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5.2 Narrative . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.2 Narrative . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.3 Client-to-Server Example . . . . . . . . . . . . . . . . . . 20 5.3 Client-to-Server Example . . . . . . . . . . . . . . . . . . 20
5.4 Server-to-Server Example . . . . . . . . . . . . . . . . . . 21 5.4 Server-to-Server Example . . . . . . . . . . . . . . . . . . 21
6. Stream Authentication . . . . . . . . . . . . . . . . . . . 24 6. Stream Authentication . . . . . . . . . . . . . . . . . . . 24
6.1 SASL Authentication . . . . . . . . . . . . . . . . . . . . 24 6.1 SASL Authentication . . . . . . . . . . . . . . . . . . . . 24
6.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6.1.2 Narrative . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.1.2 Narrative . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.1.3 SASL Definition . . . . . . . . . . . . . . . . . . . . . . 26 6.1.3 SASL Definition . . . . . . . . . . . . . . . . . . . . . . 26
6.1.4 Client-to-Server Example . . . . . . . . . . . . . . . . . . 27 6.1.4 Client-to-Server Example . . . . . . . . . . . . . . . . . . 27
6.1.5 Server-to-Server Example . . . . . . . . . . . . . . . . . . 29 6.1.5 Server-to-Server Example . . . . . . . . . . . . . . . . . . 29
6.2 Dialback Authentication . . . . . . . . . . . . . . . . . . 32 6.2 Dialback Authentication . . . . . . . . . . . . . . . . . . 31
6.2.1 Dialback Protocol . . . . . . . . . . . . . . . . . . . . . 34 6.2.1 Dialback Protocol . . . . . . . . . . . . . . . . . . . . . 34
7. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . 37 7. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . 37
7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.2 Common Attributes . . . . . . . . . . . . . . . . . . . . . 37 7.2 Common Attributes . . . . . . . . . . . . . . . . . . . . . 37
7.2.1 to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.2.1 to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.2.2 from . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.2.2 from . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
7.2.3 id . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7.2.3 id . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.2.4 type . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7.2.4 type . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.2.5 xml:lang . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7.2.5 xml:lang . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7.3 Message Stanzas . . . . . . . . . . . . . . . . . . . . . . 38 7.3 Message Stanzas . . . . . . . . . . . . . . . . . . . . . . 38
7.3.1 Types of Message . . . . . . . . . . . . . . . . . . . . . . 39 7.3.1 Types of Message . . . . . . . . . . . . . . . . . . . . . . 39
7.3.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 39 7.3.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.4 Presence Stanzas . . . . . . . . . . . . . . . . . . . . . . 40 7.4 Presence Stanzas . . . . . . . . . . . . . . . . . . . . . . 40
7.4.1 Types of Presence . . . . . . . . . . . . . . . . . . . . . 41 7.4.1 Types of Presence . . . . . . . . . . . . . . . . . . . . . 41
7.4.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 41 7.4.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 41
7.5 IQ Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 43 7.5 IQ Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 42
7.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 43 7.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 43
7.5.2 Types of IQ . . . . . . . . . . . . . . . . . . . . . . . . 43 7.5.2 Types of IQ . . . . . . . . . . . . . . . . . . . . . . . . 43
7.5.3 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 44 7.5.3 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 44
7.6 Extended Namespaces . . . . . . . . . . . . . . . . . . . . 44 7.6 Extended Namespaces . . . . . . . . . . . . . . . . . . . . 44
7.7 Stanza Errors . . . . . . . . . . . . . . . . . . . . . . . 45 7.7 Stanza Errors . . . . . . . . . . . . . . . . . . . . . . . 45
7.7.1 Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.7.1 Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.7.2 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.7.2 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.7.3 Conditions . . . . . . . . . . . . . . . . . . . . . . . . . 46 7.7.3 Conditions . . . . . . . . . . . . . . . . . . . . . . . . . 46
7.7.4 Extensibility . . . . . . . . . . . . . . . . . . . . . . . 47 7.7.4 Extensibility . . . . . . . . . . . . . . . . . . . . . . . 47
8. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . 48 8. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . 48
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A. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 57 A. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 57
A.1 Streams namespace . . . . . . . . . . . . . . . . . . . . . 57 A.1 Streams namespace . . . . . . . . . . . . . . . . . . . . . 57
A.2 TLS namespace . . . . . . . . . . . . . . . . . . . . . . . 58 A.2 TLS namespace . . . . . . . . . . . . . . . . . . . . . . . 58
A.3 SASL namespace . . . . . . . . . . . . . . . . . . . . . . . 58 A.3 SASL namespace . . . . . . . . . . . . . . . . . . . . . . . 58
A.4 Dialback namespace . . . . . . . . . . . . . . . . . . . . . 59 A.4 Dialback namespace . . . . . . . . . . . . . . . . . . . . . 59
A.5 Client namespace . . . . . . . . . . . . . . . . . . . . . . 60 A.5 Client namespace . . . . . . . . . . . . . . . . . . . . . . 60
A.6 Server namespace . . . . . . . . . . . . . . . . . . . . . . 63 A.6 Server namespace . . . . . . . . . . . . . . . . . . . . . . 63
A.7 Stream error namespace . . . . . . . . . . . . . . . . . . . 66 A.7 Stream error namespace . . . . . . . . . . . . . . . . . . . 66
A.8 Stanza error namespace . . . . . . . . . . . . . . . . . . . 67 A.8 Stanza error namespace . . . . . . . . . . . . . . . . . . . 67
B. Revision History . . . . . . . . . . . . . . . . . . . . . . 69 B. Revision History . . . . . . . . . . . . . . . . . . . . . . 69
B.1 Changes from draft-ietf-xmpp-core-06 . . . . . . . . . . . . 69 B.1 Changes from draft-ietf-xmpp-core-07 . . . . . . . . . . . . 69
B.2 Changes from draft-ietf-xmpp-core-05 . . . . . . . . . . . . 69 B.2 Changes from draft-ietf-xmpp-core-06 . . . . . . . . . . . . 69
B.3 Changes from draft-ietf-xmpp-core-04 . . . . . . . . . . . . 69 B.3 Changes from draft-ietf-xmpp-core-05 . . . . . . . . . . . . 69
B.4 Changes from draft-ietf-xmpp-core-03 . . . . . . . . . . . . 70 B.4 Changes from draft-ietf-xmpp-core-04 . . . . . . . . . . . . 69
B.5 Changes from draft-ietf-xmpp-core-02 . . . . . . . . . . . . 70 B.5 Changes from draft-ietf-xmpp-core-03 . . . . . . . . . . . . 70
B.6 Changes from draft-ietf-xmpp-core-01 . . . . . . . . . . . . 70 B.6 Changes from draft-ietf-xmpp-core-02 . . . . . . . . . . . . 70
B.7 Changes from draft-ietf-xmpp-core-00 . . . . . . . . . . . . 70 B.7 Changes from draft-ietf-xmpp-core-01 . . . . . . . . . . . . 70
B.8 Changes from draft-miller-xmpp-core-02 . . . . . . . . . . . 71 B.8 Changes from draft-ietf-xmpp-core-00 . . . . . . . . . . . . 70
Full Copyright Statement . . . . . . . . . . . . . . . . . . 72 B.9 Changes from draft-miller-xmpp-core-02 . . . . . . . . . . . 71
Intellectual Property and Copyright Statements . . . . . . . 72
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
[1] protocol for near-real-time messaging, presence, and request- [1] protocol for near-real-time messaging, presence, and
response services. The basic syntax and semantics were developed request-response services. The basic syntax and semantics were
originally within the Jabber open-source community, mainly in 1999. developed originally within the Jabber open-source community, mainly
In 2002, the XMPP WG was chartered with developing an adaptation of in 1999. In 2002, the XMPP WG was chartered with developing an
the Jabber protocol that would be suitable as an IETF instant adaptation of the Jabber protocol that would be suitable as an IETF
messaging and presence technology. As a result of work by the XMPP instant messaging and presence technology. As a result of work by the
WG, the current document defines the core features of XMPP; XMPP IM XMPP WG, the current document defines the core features of XMPP; XMPP
[2] defines the extensions required to provide the instant messaging IM [2] defines the extensions required to provide the instant
(IM) and presence functionality defined in RFC 2779 [3]. messaging (IM) and presence functionality defined in RFC 2779 [3].
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 [4]. 2119 [4].
1.3 Discussion Venue 1.3 Discussion Venue
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identifying namespaces and other protocol syntax. Jabber[tm] is a identifying namespaces and other protocol syntax. Jabber[tm] is a
registered trademark of Jabber, Inc. Jabber, Inc. grants permission registered trademark of Jabber, Inc. Jabber, Inc. grants permission
to the IETF for use of the Jabber trademark in association with this to the IETF for use of the Jabber trademark in association with this
specification and its successors, if any. specification and its successors, if any.
2. Generalized Architecture 2. Generalized Architecture
2.1 Overview 2.1 Overview
Although XMPP is not wedded to any specific network architecture, to Although XMPP is not wedded to any specific network architecture, to
this point it has usually been implemented via a typical client- this point it has usually been implemented via a typical
server architecture, wherein a client utilizing XMPP accesses a client-server architecture, wherein a client utilizing XMPP accesses
server over a TCP [5] socket. a server over a TCP [5] socket.
The following diagram provides a high-level overview of this The following diagram provides a high-level overview of this
architecture (where "-" represents communications that use XMPP and architecture (where "-" represents communications that use XMPP and
"=" represents communications that use any other protocol). "=" represents communications that use any other protocol).
C1 - S1 - S2 - C3 C1 - S1 - S2 - C3
/ \ / \
C2 - G1 = FN1 = FC1 C2 - G1 = FN1 = FC1
The symbols are as follows: The symbols are as follows:
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communications. Its primary responsibilities are to manage communications. Its primary responsibilities are to manage
connections from or sessions for other entities (in the form of XML connections from or sessions for other entities (in the form of XML
streams to and from authorized clients, servers, and other entities) streams to and from authorized clients, servers, and other entities)
and to route appropriately-addressed XML data "stanzas" among such and to route appropriately-addressed XML data "stanzas" among such
entities over XML streams. Most XMPP-compliant servers also assume entities over XML streams. Most XMPP-compliant servers also assume
responsibility for the storage of data that is used by clients (e.g., responsibility for the storage of data that is used by clients (e.g.,
contact lists for users of XMPP-based IM applications); in this case, contact lists for users of XMPP-based IM applications); in this case,
the XML data is processed directly by the server itself on behalf of the XML data is processed directly by the server itself on behalf of
the client and is not routed to another entity. Compliant server the client and is not routed to another entity. Compliant server
implementations MUST ensure in-order processing of XML stanzas implementations MUST ensure in-order processing of XML stanzas
received from connected clients, servers, and services. between any two entities.
2.3 Client 2.3 Client
Most clients connect directly to a server over a TCP socket and use Most clients connect directly to a server over a TCP socket and use
XMPP to take full advantage of the functionality provided by a server XMPP to take full advantage of the functionality provided by a server
and any associated services, although it must be noted that there is and any associated services, although it must be noted that there is
no necessary coupling of an XML stream to a TCP socket (e.g., a no necessary coupling of an XML stream to a TCP socket (e.g., a
client COULD connect via HTTP polling or some other mechanism). client COULD connect via HTTP polling or some other mechanism).
Multiple resources (e.g., devices or locations) MAY connect Multiple resources (e.g., devices or locations) MAY connect
simultaneously to a server on behalf of each authorized client, with simultaneously to a server on behalf of each authorized client, with
each resource connecting over a discrete TCP socket and each resource connecting over a discrete TCP socket and
differentiated by the resource identifier of a JID (Section 3) (e.g., differentiated by the resource identifier of a JID (Section 3) (e.g.,
user@domain/home vs. user@domain/work). The port registered with user@domain/home vs. user@domain/work). The port registered with the
the IANA [6] for connections between a Jabber client and a Jabber IANA [6] for connections between a Jabber client and a Jabber server
server is 5222. For further details about client-to-server is 5222. For further details about client-to-server communications
communications expressly for the purpose of instant messaging and expressly for the purpose of instant messaging and presence, refer to
presence, refer to XMPP IM [2]. XMPP IM [2].
2.4 Gateway 2.4 Gateway
A gateway is a special-purpose server-side service whose primary A gateway is a special-purpose server-side service whose primary
function is to translate XMPP into the protocol(s) of another function is to translate XMPP into the protocol(s) of another
messaging system, as well as to translate the return data back into messaging system, as well as to translate the return data back into
XMPP. Examples are gateways to SIMPLE, Internet Relay Chat (IRC), XMPP. Examples are gateways to SIMPLE, Internet Relay Chat (IRC),
Short Message Service (SMS), SMTP, and foreign instant messaging Short Message Service (SMS), SMTP, and foreign instant messaging
networks such as Yahoo!, MSN, ICQ, and AIM. Communications between networks such as Yahoo!, MSN, ICQ, and AIM. Communications between
gateways and servers, and between gateways and the foreign messaging gateways and servers, and between gateways and the foreign messaging
system, are not defined in this document. system, are not defined in this document.
2.5 Network 2.5 Network
Because each server is identified by a network address (typically a Because each server is identified by a network address (typically a
DNS hostname) and because server-to-server communications are a DNS hostname) and because server-to-server communications are a
straightforward extension of the client-to-server protocol, in straightforward extension of the client-to-server protocol, in
practice the system consists of a network of servers that inter- practice the system consists of a network of servers that
communicate. Thus user-a@domain1 is able to exchange messages, inter-communicate. Thus user-a@domain1 is able to exchange messages,
presence, and other information with user-b@domain2. This pattern is presence, and other information with user-b@domain2. This pattern is
familiar from messaging protocols (such as SMTP) that make use of familiar from messaging protocols (such as SMTP) that make use of
network addressing standards. Upon opening a TCP socket on the IANA- network addressing standards. Upon opening a TCP socket on the
registered port 5269, there are two methods for negotiating a IANA-registered port 5269, there are two methods for negotiating a
connection between any two servers: server dialback (Section 6.2) and connection between any two servers: server dialback (Section 6.2) and
SASL authentication (Section 6.1). SASL authentication (Section 6.1).
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
All such entities are uniquely addressable in a form that is such entities are uniquely addressable in a form that is consistent
consistent with RFC 2396 [7]. In particular, a valid Jabber with RFC 2396 [7]. In particular, a valid Jabber Identifier (JID)
Identifier (JID) contains a set of ordered elements formed of a contains a set of ordered elements formed of a domain identifier,
domain identifier, node identifier, and resource identifier in the node identifier, and resource identifier in the following format:
following format: [node@]domain[/resource]. [node@]domain[/resource].
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
of this structure is to identify an IM user, the server to which the this structure is to identify an IM user, the server to which the
user connects, and the user's active session or connection (e.g., a user connects, and the user's active session or connection (e.g., a
specific client) in the form of user@domain/resource. However, node specific client) in the form of user@domain/resource. However, node
types other than clients are possible; for example, a specific chat types other than clients are possible; for example, a specific chat
room offered by a multi-user chat service could be addressed as room offered by a multi-user chat service could be addressed as
<room@service> (where "room" is the name of the chat room and <room@service> (where "room" is the name of the chat room and
"service" is the hostname of the multi-user chat service) and a "service" is the hostname of the multi-user chat service) and a
specific occupant of such a room could be addressed as <room@service/ specific occupant of such a room could be addressed as <room@service/
nick> (where "nick" is the occupant's room nickname). Many other JID nick> (where "nick" is the occupant's room nickname). Many other JID
types are possible (e.g., <domain/resource> could be a server-side types are possible (e.g., <domain/resource> could be a server-side
script or service). script or service).
skipping to change at page 9, line 5 skipping to change at page 9, line 5
Name. A domain identifier MUST conform to RFC 952 [8] and RFC 1123 Name. A domain identifier MUST conform to RFC 952 [8] and RFC 1123
[9]. A domain identifier MUST be no more than 1023 bytes in length [9]. A domain identifier MUST be no more than 1023 bytes in length
and MUST conform to the nameprep [10] profile of stringprep [11]. and MUST conform to the nameprep [10] profile of stringprep [11].
3.3 Node Identifier 3.3 Node Identifier
The node identifier is an optional secondary identifier. It usually The node identifier is an optional secondary identifier. It usually
represents the entity requesting and using network access provided by represents the entity requesting and using network access provided by
the server or gateway (i.e., a client), although it can also the server or gateway (i.e., a client), although it can also
represent other kinds of entities (e.g., a multi-user chat room represent other kinds of entities (e.g., a multi-user chat room
associated with a multi-user chat service). The entity represented associated with a multi-user chat service). The entity represented by
by a node identifier is addressed within the context of a specific a node identifier is addressed within the context of a specific
domain; within IM applications of XMPP this address is called a "bare domain; within IM applications of XMPP this address is called a "bare
JID" and is of the form <user@domain>. JID" and is of the form <user@domain>.
A node identifier MUST be no more than 1023 bytes in length and MUST A node identifier MUST be no more than 1023 bytes in length and MUST
conform to the nodeprep [12] profile of stringprep [11]. conform to the nodeprep [12] profile of stringprep [11].
3.4 Resource Identifier 3.4 Resource Identifier
The resource identifer is an optional tertiary identifier. It The resource identifer is an optional tertiary identifier. It usually
usually represents a specific session, connection (e.g., a device or represents a specific session, connection (e.g., a device or
location), or object (e.g., a participant in a multi-user chat room) location), or object (e.g., a participant in a multi-user chat room)
belonging to the entity associated with a node identifier. An entity belonging to the entity associated with a node identifier. An entity
may maintain multiple resources simultaneously. may maintain multiple resources simultaneously.
A resource identifier MUST be no more than 1023 bytes in length and A resource identifier MUST be no more than 1023 bytes in length and
MUST conform to the resourceprep [13] profile of stringprep [11]. MUST conform to the resourceprep [13] profile of stringprep [11].
4. XML Streams 4. XML Streams
4.1 Overview 4.1 Overview
Two fundamental concepts make possible the rapid, asynchronous Two fundamental concepts make possible the rapid, asynchronous
exchange of relatively small payloads of structured information exchange of relatively small payloads of structured information
between presence-aware entities: XML streams and XML stanzas: between presence-aware entities, XML streams and XML stanzas:
Definition of XML stream: An XML stream is a container for the Definition of XML stream: An XML stream is a container for the
exchange of XML elements between any two entities over a network. exchange of XML elements between any two entities over a network.
An XML stream is negotiated from an initiating entity (usually a An XML stream is negotiated from an initiating entity (usually a
client or server) to a receiving entity (usually a server), client or server) to a receiving entity (usually a server),
normally over a TCP socket. An XML stream corresponds to the normally over a TCP socket. An XML stream corresponds to the
initiating entity's "session" with the receiving entity. The initiating entity's "session" with the receiving entity. The start
start of the XML stream is denoted unambiguously by an opening XML of the XML stream is denoted unambiguously by an opening XML
<stream> tag with appropriate attributes and namespace <stream> tag with appropriate attributes and namespace
declarations, and the end of the XML stream is denoted declarations, and the end of the XML stream is denoted
unambiguously be a closing XML </stream> tag. An XML stream is unambiguously be a closing XML </stream> tag. An XML stream is
unidirectional; in order to enable bidirectional information unidirectional; in order to enable bidirectional information
exchange, one stream must be negotiated from initiating entity to exchange, one stream must be negotiated from initiating entity to
receiving entity and another stream must be negotiated from receiving entity and another stream must be negotiated from
receiving entity to initiating entity. receiving entity to initiating entity.
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
level of the root <stream/> element and is said to be well- of the root <stream/> element and is said to be well-balanced if
balanced if it matches production [43] content of the XML it matches production [43] content of the XML specification [1]).
specification [1]). The start of any XML stanza is denoted The start of any XML stanza is denoted unambiguously by the
unambiguously by the element start tag at depth=1 (e.g., element start tag at depth=1 (e.g., <presence>), and the end of
<presence>), and the end of any XML stanza is denoted any XML stanza is denoted unambiguously by the corresponding close
unambiguously by the corresponding close tag at depth=1 (e.g., </ tag at depth=1 (e.g., </presence>). An XML stanza MAY contain
presence>). An XML stanza MAY contain child elements or CDATA child elements (with accompanying attributes, elements, and CDATA)
sections as necessary in order to convey the desired information. as necessary in order to convey the desired information.
Consider the example of a client's session with a server. In order Consider the example of a client's session with a server. In order to
to connect to a server, a client must initiate an XML stream by connect to a server, a client must initiate an XML stream by sending
sending an opening <stream> tag to the server, optionally preceded by an opening <stream> tag to the server, optionally preceded by a text
a text declaration specifying the XML version supported and the declaration specifying the XML version supported and the character
character encoding. The server SHOULD then reply with a second XML encoding. The server SHOULD then reply with a second XML stream back
stream back to the client, again optionally preceded by a text to the client, again optionally preceded by a text declaration. Once
declaration. Once the client has authenticated with the server (see the client has authenticated with the server (see Section 6), the
Section 6), the client MAY send an unlimited number of XML stanzas client MAY send an unlimited number of XML stanzas over the stream to
over the stream to any recipient on the network. When the client any recipient on the network. When the client desired to close the
desired to close the stream, it simply sends a closing </stream> tag stream, it simply sends a closing </stream> tag to the server
to the server (alternatively, the session may be closed by the (alternatively, the session may be closed by the server).
server).
Thus a client's session with a server can be seen as two open-ended Thus a client's session with a server can be seen as two open-ended
XML documents that are built up through the accumulation of the XML XML documents that are built up through the accumulation of the XML
stanzas sent over the two XML streams (i.e., one from the client to stanzas sent over the two XML streams (i.e., one from the client to
the server and one from the server to the client), and the root the server and one from the server to the client), and the root
<stream/> element can be considered the document entity for each <stream/> element can be considered the document entity for each
document. In essence, then, an XML stream acts as an envelope for document. In essence, then, an XML stream acts as an envelope for all
all the XML stanzas sent during a session. We can represent this the XML stanzas sent during a session. We can represent this
graphically as follows: graphically as follows:
|-------------------| |-------------------|
| <stream> | | <stream> |
|-------------------| |-------------------|
| <message to=''> | | <message to=''> |
| <body/> | | <body/> |
| </message> | | </message> |
|-------------------| |-------------------|
| <presence to=''> | | <presence to=''> |
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o from -- The 'from' attribute SHOULD be used only in the XML stream o from -- The 'from' attribute SHOULD be used only in the XML stream
from the receiving entity to the initiating entity, and MUST be from the receiving entity to the initiating entity, and MUST be
set to the XMPP address of the receiving entity granting access to set to the XMPP address of the receiving entity granting access to
the initiating entity. There SHOULD be no 'from' attribute on the the initiating entity. There SHOULD be no 'from' attribute on the
XML stream sent from the initiating entity to the receiving XML stream sent from the initiating entity to the receiving
entity; however, if a 'from' attribute is included, it SHOULD be entity; however, if a 'from' attribute is included, it SHOULD be
ignored by the receiving entity. 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
from the receiving entity to the initiating entity. This from the receiving entity to the initiating entity. This attribute
attribute is a unique identifier created by the receiving entity is a unique identifier created by the receiving entity to function
to function as a session key for the initiating entity's session as a session key for the initiating entity's session with the
with the receiving entity. There SHOULD be no 'id' attribute on receiving entity. There SHOULD be no 'id' attribute on the XML
the XML stream sent from the initiating entity to the receiving stream sent from the initiating entity to the receiving entity;
entity; however, if an 'id' attribute is included, it SHOULD be however, if an 'id' attribute is included, it SHOULD be ignored by
ignored by the receiving entity. the receiving entity.
o version -- The 'version' attribute MAY be used in the XML stream o version -- The 'version' attribute MAY be used in the XML stream
from the initiating entity to the receiving entity in order signal from the initiating entity to the receiving entity in order signal
compliance with the protocol defined herein; this is done by compliance with the protocol defined herein; this is done by
setting the value of the attribute to "1.0". If the initiating setting the value of the attribute to "1.0". If the initiating
entity includes the version attribute and the receiving entity entity includes the version attribute and the receiving entity
supports XMPP 1.0, the receiving entity MUST reciprocate by supports XMPP 1.0, the receiving entity MUST reciprocate by
including the attribute in its response. including the attribute in its response.
We can summarize these values as follows: We can summarize these values as follows:
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o jabber:server -- this default namespace is declared when the o jabber:server -- this default namespace is declared when the
stream is used for communications between two servers stream is used for communications between two servers
The jabber:client and jabber:server namespaces are nearly identical The jabber:client and jabber:server namespaces are nearly identical
but are used in different contexts (client-to-server communications but are used in different contexts (client-to-server communications
for jabber:client and server-to-server communications for for jabber:client and server-to-server communications for
jabber:server). The only difference between the two is that the 'to' jabber:server). The only difference between the two is that the 'to'
and 'from' attributes are OPTIONAL on stanzas sent within and 'from' attributes are OPTIONAL on stanzas sent within
jabber:client, whereas they are REQUIRED on stanzas sent within jabber:client, whereas they are REQUIRED on stanzas sent within
jabber:server. If a compliant implementation accepts a stream that jabber:server. If a compliant implementation accepts a stream that is
is scoped by the 'jabber:client' or 'jabber:server' namespace, it scoped by the 'jabber:client' or 'jabber:server' namespace, it MUST
MUST support all three core stanza types (message, presence, and IQ) support all three core stanza types (message, presence, and IQ) as
as described herein and defined in the schema. described herein and defined in the schema.
4.4 Stream Features 4.4 Stream Features
The root stream element MAY contain a features child element (e.g., The root stream element MAY contain a features child element (e.g.,
<stream:features/> if the stream namespace prefix is 'stream'). This <stream:features/> if the stream namespace prefix is 'stream'). This
is used to communicate generic stream-level capabilities including is used to communicate generic stream-level capabilities including
stream-level features that can be negotiated as the streams are set stream-level features that can be negotiated as the streams are set
up. If the initiating entity sends a "version='1.0'" flag in its up. If the initiating entity sends a "version='1.0'" flag in its
initiating stream element, the receiving entity MUST send a features initiating stream element, the receiving entity MUST send a features
child element to the initiating entity if there are any capabilities child element to the initiating entity if there are any capabilities
that need to be advertised or features that can be negotiated for the that need to be advertised or features that can be negotiated for the
stream. Currently this is used for SASL and TLS negotiation only, stream. Currently this is used for SASL and TLS negotiation only, but
but it could be used for other negotiable features in the future it could be used for other negotiable features in the future (usage
(usage is defined under Stream Encryption (Section 5) and Stream is defined under Stream Encryption (Section 5) and Stream
Authentication (Section 6) below). If an entity does not understand Authentication (Section 6) below). If an entity does not understand
or support some features, it SHOULD ignore them. or support some features, it SHOULD ignore them.
4.5 Stream Errors 4.5 Stream Errors
The root stream element MAY contain an error child element (e.g., The root stream element MAY contain an error child element (e.g.,
<stream:error/> if the stream namespace prefix is 'stream'). The <stream:error/> if the stream namespace prefix is 'stream'). The
error child MUST be sent by a Jabber entity (usually a server rather error child MUST be sent by a Jabber entity (usually a server rather
than a client) if it perceives that a stream-level error has than a client) if it perceives that a stream-level error has
occurred. occurred.
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o format -- the condition relates to XML format or structure o format -- the condition relates to XML format or structure
o redirect -- the condition relates to a host redirection o redirect -- the condition relates to a host redirection
o server -- the condition relates to the internal state of the o server -- the condition relates to the internal state of the
server server
The <stream-condition/> element MUST contain a child element that The <stream-condition/> element MUST contain a child element that
specifies a particular stream-level error condition, as defined in specifies a particular stream-level error condition, as defined in
the next section. (Note: the XML namespace name the next section. (Note: the XML namespace name
'urn:ietf:params:xml:ns:xmpp-streams' that scopes the <stream- 'urn:ietf:params:xml:ns:xmpp-streams' that scopes the
condition/> element adheres to the format defined in The IETF XML <stream-condition/> element adheres to the format defined in The IETF
Registry [15].) XML Registry [15].)
4.5.3 Conditions 4.5.3 Conditions
The following stream-level error conditions are defined: The following stream-level error conditions are defined:
o <host-gone/> -- the value of the 'to' attribute provided by the o <host-gone/> -- the value of the 'to' attribute provided by the
initiating entity in the stream header corresponds to a hostname initiating entity in the stream header corresponds to a hostname
that is no longer hosted by the server; the associated class is that is no longer hosted by the server; the associated class is
"address". "address".
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MAY contain CDATA specifying the XMPP version(s) supported by the MAY contain CDATA specifying the XMPP version(s) supported by the
server; the associated class is "format". server; the associated class is "format".
o <xml-not-well-formed/> -- the initiating entity has sent XML that o <xml-not-well-formed/> -- the initiating entity has sent XML that
is not well-formed as defined by the XML specification [1]; the is not well-formed as defined by the XML specification [1]; the
associated class is "format". associated class is "format".
4.5.4 Extensibility 4.5.4 Extensibility
If desired, an XMPP application MAY provide custom error information; If desired, an XMPP application MAY provide custom error information;
this MUST be contained in a properly-namespaced child of the <stream- this MUST be contained in a properly-namespaced child of the
condition/> element (i.e., the namespace name MUST NOT be one of the <stream-condition/> element (i.e., the namespace name MUST NOT be one
namespace names defined herein). of the namespace names defined herein).
4.6 Simple Streams Example 4.6 Simple Streams Example
The following is a stream-based session of a client on a server The following is a stream-based session of a client on a server
(where the "C" lines are sent from the client to the server, and the (where the "C" lines are sent from the client to the server, and the
"S" lines are sent from the server to the client): "S" lines are sent from the server to the client):
A basic session: A basic session:
C: <?xml version='1.0'?> C: <?xml version='1.0'?>
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S: </stream:stream> S: </stream:stream>
5. Stream Encryption 5. Stream Encryption
5.1 Overview 5.1 Overview
XMPP includes a method for securing the stream from tampering and XMPP includes a method for securing the stream from tampering and
eavesdropping. This channel encryption method makes use of the eavesdropping. This channel encryption method makes use of the
Transport Layer Security (TLS) [16] protocol, along with a "STARTTLS" Transport Layer Security (TLS) [16] protocol, along with a "STARTTLS"
extension that is modelled on similar extensions for the IMAP [17], extension that is modelled on similar extensions for the IMAP [17],
POP3 [18], and ACAP [19] protocols as described in RFC 2595 [20]. POP3 [18], and ACAP [19] protocols as described in RFC 2595 [20]. The
The namespace identifier for the STARTTLS extension is 'http:// namespace identifier for the STARTTLS extension is 'http://
www.ietf.org/rfc/rfc2595.txt'. TLS SHOULD be used between any www.ietf.org/rfc/rfc2595.txt'. TLS SHOULD be used between any
initiating entity and any receiving entity (e.g., a stream from a initiating entity and any receiving entity (e.g., a stream from a
client to a server or from one server to another). client to a server or from one server to another).
The following rules MUST be observed: The following rules MUST be observed:
1. If the initiating entity is capable of using the STARTTLS 1. If the initiating entity is capable of using the STARTTLS
extension, it MUST include the "version='1.0'" flag in the extension, it MUST include the "version='1.0'" flag in the
initiating stream header. initiating stream header.
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3. If the initiating entity chooses to use TLS for stream 3. If the initiating entity chooses to use TLS for stream
encryption, TLS negotiation MUST be completed before proceeding encryption, TLS negotiation MUST be completed before proceeding
to authenticate the stream using SASL. to authenticate the stream using SASL.
4. The initiating entity MUST validate the certificate presented by 4. The initiating entity MUST validate the certificate presented by
the receiving entity: the receiving entity:
1. If the initiating entity has been configured with a set of 1. If the initiating entity has been configured with a set of
trusted roots, either a well-known public set or a manually trusted roots, either a well-known public set or a manually
configured Certificate Authority (e.g., an organization's configured Certificate Authority (e.g., an organization's own
own Certificate Authority), normal certificate validation Certificate Authority), normal certificate validation
processing is appropriate. processing is appropriate.
2. If the initiating entity has been configured with the 2. If the initiating entity has been configured with the
receiving entity's public key or certificate, a simple receiving entity's public key or certificate, a simple
comparison is appropriate. comparison is appropriate.
If the above methods fail, the certificate MAY be presented to a If the above methods fail, the certificate MAY be presented to a
user for approval; the user SHOULD be given the option to store user for approval; the user SHOULD be given the option to store
the certificate and not ask again for at least some reasonable the certificate and not ask again for at least some reasonable
period of time. period of time.
5. If the TLS negotiation is successful, TLS takes effect 5. If the TLS negotiation is successful, the receiving entity MUST
immediately following the closing ">" character of the
<starttls/> element for the client and immediately following the
closing ">" character of the <proceed> element for the server.
A new stream MUST then be initiated by the initiating entity.
6. If the TLS negotiation is successful, the receiving entity MUST
discard any knowledge obtained from the initiating entity before discard any knowledge obtained from the initiating entity before
TLS takes effect. TLS takes effect.
7. If the TLS negotiation is successful, the initiating entity MUST 6. If the TLS negotiation is successful, the initiating entity MUST
discard any knowledge obtained from the receiving entity before discard any knowledge obtained from the receiving entity before
TLS takes effect. TLS takes effect.
8. If the TLS negotiation is successful, the receiving entity MUST 7. If the TLS negotiation is successful, the receiving entity MUST
NOT offer the STARTTLS extension to the initiating entity along NOT offer the STARTTLS extension to the initiating entity along
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.
9. Whether the TLS negotiation results in success or failure, the 8. Whether the TLS negotiation results in success or failure, the
initiating entity SHOULD continue with SASL negotiation. initiating entity SHOULD continue with SASL negotiation.
10. If TLS is used for stream encryption, SASL MUST NOT be used for
anything but stream authentication (i.e., a security layer MUST
NOT be negotiated using SASL). Conversely, if a security layer
is to be negotiated via SASL, TLS MUST NOT be used.
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. Then initiating entity opens a TCP connection and initiates the 1. Then 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='1.0'" flag. entity, including the "version='1.0'" flag.
2. The receiving entity responds by opening a TCP connection and 2. The receiving entity responds by opening a TCP connection and
sending an XML stream header to then initiating entity. sending an XML stream header to the initiating entity.
3. The receiving entity offers the STARTTLS extension to then 3. The receiving entity offers the STARTTLS extension to the
initiating entity by sending it along with the list of supported initiating entity by sending it along with the list of supported
stream features. stream features.
4. Then initiating entity issues the STARTTLS command to instruct 4. Then initiating entity issues the STARTTLS command to instruct
the receiving entity that it wishes to begin a TLS negotiation to the receiving entity that it wishes to begin a TLS negotiation to
secure the stream. secure the stream.
5. The receiving entity MUST reply with either an empty <proceed/> 5. The receiving entity MUST reply with either an empty <proceed/>
element or an empty <failure/> element, but keep the underlying element or an empty <failure/> element, but keep the underlying
TCP connection open. TCP connection open.
6. Then initiating entity begins a TLS negotiation in accordance 6. Then initiating entity begins a TLS negotiation in accordance
with RFC 2246 [16]. Upon completion of the negotiation, then with RFC 2246 [16]. Upon completion of the negotiation, the
initiating entity initiates a new stream by sending a new opening initiating entity initiates a new stream by sending a new opening
XML stream header to the receiving entity. XML stream header to the receiving entity.
7. The receiving entity responds by sending an XML stream header to 7. The receiving entity responds by sending an XML stream header to
then initiating entity along with the remaining available the initiating entity along with the remaining available features
features (but NOT including the STARTTLS element). (but NOT including the STARTTLS element).
5.3 Client-to-Server Example 5.3 Client-to-Server Example
The following example shows the data flow for a client securing a The following example shows the data flow for a client securing a
stream using STARTTLS. stream using STARTTLS.
Step 1: Client initiates stream to server: Step 1: Client initiates stream to server:
<stream:stream <stream:stream
xmlns='jabber:client' xmlns='jabber:client'
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of XML streams. When one entity is already known to another (i.e., of XML streams. When one entity is already known to another (i.e.,
there is an existing trust relationship between the entities such as there is an existing trust relationship between the entities such as
that established when a user registers with a server or an that established when a user registers with a server or an
administrator configures a server to trust another server), the administrator configures a server to trust another server), the
preferred method for authenticating streams between the two entities preferred method for authenticating streams between the two entities
uses an XMPP adaptation of the Simple Authentication and Security uses an XMPP adaptation of the Simple Authentication and Security
Layer (SASL) [21]. When there is no existing trust relationship Layer (SASL) [21]. When there is no existing trust relationship
between two servers, some level of trust MAY be established based on between two servers, some level of trust MAY be established based on
existing trust in DNS; the authentication method used in this case is existing trust in DNS; the authentication method used in this case is
the server dialback protocol that is native to XMPP (no such ad-hoc the server dialback protocol that is native to XMPP (no such ad-hoc
method is defined between a client and a server). If SASL is used method is defined between a client and a server). If SASL is used for
for server-to-server authentication, the servers MUST NOT use server-to-server authentication, the servers MUST NOT use dialback.
dialback. Both SASL authentication and dialback are described in Both SASL authentication and dialback are described in this section.
this section.
Stream authentication is REQUIRED for all direct communications Stream authentication is REQUIRED for all direct communications
between two entities; if an entity sends a stanza to an between two entities; if an entity sends a stanza to an
unauthenticated stream, the receiving entity SHOULD silently drop the unauthenticated stream, the receiving entity SHOULD silently drop the
stanza and MUST NOT process it. stanza and MUST NOT process it.
6.1 SASL Authentication 6.1 SASL Authentication
6.1.1 Overview 6.1.1 Overview
The Simple Authentication and Security Layer (SASL) provides a The Simple Authentication and Security Layer (SASL) provides a
generalized method for adding authentication support to connection- generalized method for adding authentication support to
based protocols. XMPP uses a generic XML namespace profile for SASL connection-based protocols. XMPP uses a generic XML namespace profile
that conforms to section 4 ("Profiling Requirements") of RFC 2222 for SASL that conforms to section 4 ("Profiling Requirements") of RFC
[21] (the namespace identifier for this protocol is 'http:// 2222 [21] (the namespace identifier for this protocol is 'http://
www.iana.org/assignments/sasl-mechanisms'). www.iana.org/assignments/sasl-mechanisms').
The following rules MUST be observed: The following rules MUST be observed:
1. If TLS is used for stream encryption, SASL MUST NOT be used for 1. If TLS is used for stream encryption, SASL MUST NOT be used for
anything but stream authentication (i.e., a security layer MUST anything but stream authentication (i.e., a security layer MUST
NOT be negotiated using SASL). Conversely, if a security layer NOT be negotiated using SASL). Conversely, if a security layer is
is to be negotiated via SASL, TLS MUST NOT be used. to be negotiated via SASL, TLS MUST NOT be used.
2. If the initiating entity is capable of authenticating via SASL, 2. If the initiating entity is capable of authenticating via SASL,
it it MUST include the "version='1.0'" flag in the initiating it it MUST include the "version='1.0'" flag in the initiating
stream header. stream header.
3. If the receiving entity is capable of accepting authentications 3. If the receiving entity is capable of accepting authentications
via SASL, it MUST send one or more authentication mechanisms via SASL, it MUST send one or more authentication mechanisms
within a <mechanisms/> element in response to the opening stream within a <mechanisms/> element in response to the opening stream
tag received from the initiating entity. tag received from the initiating entity.
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exchange sequence: Challenges and responses are carried through the exchange sequence: Challenges and responses are carried through the
exchange of <challenge/> elements from receiving entity to exchange of <challenge/> elements from receiving entity to
initiating entity and <response/> elements from initiating entity initiating entity and <response/> elements from initiating entity
to receiving entity. The receiving entity reports failure by to receiving entity. The receiving entity reports failure by
sending a <failure/> element and success by sending a <success/> sending a <failure/> element and success by sending a <success/>
element; the initiating entity aborts the exchange by sending an element; the initiating entity aborts the exchange by sending an
<abort/> element. <abort/> element.
security layer negotiation: If a security layer is negotiated, both security layer negotiation: If a security layer is negotiated, both
sides consider the original stream closed and new <stream/> sides consider the original stream closed and new <stream/>
headers are sent by both entities. The security layer takes headers are sent by both entities. The security layer takes effect
effect immediately following the ">" character of the empty immediately following the ">" character of the empty <response/>
<response/> element for the client and immediately following the element for the client and immediately following the closing ">"
closing ">" character of the <succeed/> element for the server. character of the <succeed/> element for the server.
use of the authorization identity: The authorization identity, if use of the authorization identity: The authorization identity, if
present, is unused by xmpp. present, is unused by xmpp.
6.1.4 Client-to-Server Example 6.1.4 Client-to-Server Example
The following example shows the data flow for a client authenticating The following example shows the data flow for a client authenticating
with a server using SASL. with a server using SASL.
Step 1: Client initiates stream to server: Step 1: Client initiates stream to server:
skipping to change at page 28, line 20 skipping to change at page 28, line 20
Step 5: Server sends a base64-encoded challenge to the client: Step 5: Server sends a base64-encoded challenge to the client:
<challenge xmlns='http://www.iana.org/assignments/sasl-mechanisms'> <challenge xmlns='http://www.iana.org/assignments/sasl-mechanisms'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi
xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz
</challenge> </challenge>
The decoded challenge is: The decoded challenge is:
realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\ qop="auth",charset=utf- realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\
8,algorithm=md5-sess qop="auth",charset=utf-8,algorithm=md5-sess
Step 6: Client responds to the challenge: Step 6: Client responds to the challenge:
<response xmlns='http://www.iana.org/assignments/sasl-mechanisms'> <response xmlns='http://www.iana.org/assignments/sasl-mechanisms'>
dXNlcm5hbWU9InJvYiIscmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik dXNlcm5hbWU9InJvYiIscmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik
9BNk1HOXRFUUdtMmhoIixcIGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLG5j 9BNk1HOXRFUUdtMmhoIixcIGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLG5j
PTAwMDAwMDAxLHFvcD1hdXRoLFwgZGlnZXN0LXVyaT0ieG1wcC9jYXRhY2 PTAwMDAwMDAxLHFvcD1hdXRoLFwgZGlnZXN0LXVyaT0ieG1wcC9jYXRhY2
x5c20uY3giLFwgcmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZ x5c20uY3giLFwgcmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZ
jIxNDNhZjcsY2hhcnNldD11dGYtOA== jIxNDNhZjcsY2hhcnNldD11dGYtOA==
</response> </response>
skipping to change at page 30, line 38 skipping to change at page 30, line 38
Step 5: Server2 sends a base64-encoded challenge to Server1: Step 5: Server2 sends a base64-encoded challenge to Server1:
<challenge xmlns='http://www.iana.org/assignments/sasl-mechanisms'> <challenge xmlns='http://www.iana.org/assignments/sasl-mechanisms'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIi
xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz xxb3A9ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz
</challenge> </challenge>
The decoded challenge is: The decoded challenge is:
realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\ qop="auth",charset=utf- realm="cataclysm.cx",nonce="OA6MG9tEQGm2hh",\
8,algorithm=md5-sess qop="auth",charset=utf-8,algorithm=md5-sess
Step 6: Server1 responds to the challenge: Step 6: Server1 responds to the challenge:
<response xmlns='http://www.iana.org/assignments/sasl-mechanisms'> <response xmlns='http://www.iana.org/assignments/sasl-mechanisms'>
cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIixjbm9uY2U9Ik9B cmVhbG09ImNhdGFjbHlzbS5jeCIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIixjbm9uY2U9Ik9B
Nk1IWGg2VnFUclJrIixuYz0wMDAwMDAwMSxxb3A9YXV0aCxkaWdlc3QtdXJpPSJ4bXBwL2Nh Nk1IWGg2VnFUclJrIixuYz0wMDAwMDAwMSxxb3A9YXV0aCxkaWdlc3QtdXJpPSJ4bXBwL2Nh
dGFjbHlzbS5jeCIscmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcs dGFjbHlzbS5jeCIscmVzcG9uc2U9ZDM4OGRhZDkwZDRiYmQ3NjBhMTUyMzIxZjIxNDNhZjcs
Y2hhcnNldD11dGYtOAo= Y2hhcnNldD11dGYtOAo=
</response> </response>
skipping to change at page 32, line 22 skipping to change at page 32, line 18
The purpose of the dialback protocol is to make server spoofing more The purpose of the dialback protocol is to make server spoofing more
difficult, and thus to make it more difficult to forge XML stanzas. difficult, and thus to make it more difficult to forge XML stanzas.
Dialback is not intended as a mechanism for securing or encrypting Dialback is not intended as a mechanism for securing or encrypting
the streams between servers as is done via SASL and TLS, only for the streams between servers as is done via SASL and TLS, only for
helping to prevent the spoofing of a server and the sending of false helping to prevent the spoofing of a server and the sending of false
data from it. Domains requiring more robust security SHOULD use TLS data from it. Domains requiring more robust security SHOULD use TLS
or SASL as defined above. or SASL as defined above.
Server dialback is made possible by the existence of DNS, since one Server dialback is made possible by the existence of DNS, since one
server can verify that another server which is connecting to it is server can verify that another server which is connecting to it is
authorized to represent a given server on the Jabber network. All authorized to represent a given server on the Jabber network. All DNS
DNS hostname resolutions MUST first resolve the hostname using an SRV hostname resolutions MUST first resolve the hostname using an SRV
[23] record of _jabber._tcp.server. If the SRV lookup fails, the [23] record of _jabber._tcp.server. If the SRV lookup fails, the
fallback is a normal A lookup to determine the IP address, using the fallback is a normal A lookup to determine the IP address, using the
jabber-server port of 5269 assigned by the Internet Assigned Numbers jabber-server port of 5269 assigned by the Internet Assigned Numbers
Authority [6]. Authority [6].
Note: the method for generating and verifying the keys used in the Note: the method for generating and verifying the keys used in the
dialback protocol MUST take into account the hostnames being used, dialback protocol MUST take into account the hostnames being used,
along with a secret known only by the receiving server and the random along with a secret known only by the receiving server and the random
ID generated for the stream. Generating unique but verifiable keys ID generated for the stream. Generating unique but verifiable keys is
is important to prevent common man-in-the-middle attacks and server important to prevent common man-in-the-middle attacks and server
spoofing. spoofing.
In the description that follows we use the following terminology: In the description that follows we use the following terminology:
o Originating Server -- the server that is attempting to establish a o Originating Server -- the server that is attempting to establish a
connection between the two servers connection between the two servers
o Receiving Server -- the server that is trying to authenticate that o Receiving Server -- the server that is trying to authenticate that
Originating Server represents the Jabber server which it claims to Originating Server represents the Jabber server which it claims to
be be
skipping to change at page 37, line 17 skipping to change at page 37, line 17
7.1 Overview 7.1 Overview
Once the XML streams in each direction have been authenticated and Once the XML streams in each direction have been authenticated and
(if desired) encrypted, XML stanzas can be sent over the streams. (if desired) encrypted, XML stanzas can be sent over the streams.
Three XML stanza types are defined for the 'jabber:client' and Three XML stanza types are defined for the 'jabber:client' and
'jabber:server' namespaces: <message/>, <presence/>, and <iq/>. 'jabber:server' namespaces: <message/>, <presence/>, and <iq/>.
In essence, the <message/> stanza type can be seen as a "push" In essence, the <message/> stanza type can be seen as a "push"
mechanism whereby one entity pushes information to another entity, mechanism whereby one entity pushes information to another entity,
similar to the communications that occur in a system such as email. similar to the communications that occur in a system such as email.
The <presence/> element can be seen as a basic broadcast or "publish- The <presence/> element can be seen as a basic broadcast or
subscribe" mechanism, whereby multiple entities receive information "publish-subscribe" mechanism, whereby multiple entities receive
(in this case, presence information) about an entity to which they information (in this case, presence information) about an entity to
have subscribed. The <iq/> element can be seen as a "request- which they have subscribed. The <iq/> element can be seen as a
response" mechanism similar to HTTP, whereby two entities can engage "request-response" mechanism similar to HTTP, whereby two entities
in a structured conversation using 'get' or 'set' requests and can engage in a structured conversation using 'get' or 'set' requests
'result' or 'error' responses. and 'result' or 'error' responses.
The syntax for these stanza types is defined below. The syntax for these stanza types is defined below.
7.2 Common Attributes 7.2 Common Attributes
Five attributes are common to message, presence, and IQ stanzas. Five attributes are common to message, presence, and IQ stanzas.
These are defined below. These are defined below.
7.2.1 to 7.2.1 to
The 'to' attribute specifies the JID of the intended recipient for The 'to' attribute specifies the JID of the intended recipient for
the stanza. In the 'jabber:client' namespace, a stanza SHOULD the stanza. In the 'jabber:client' namespace, a stanza SHOULD possess
possess a 'to' attribute, although a stanza sent from a client to a a 'to' attribute, although a stanza sent from a client to a server
server for handling by that server (e.g., presence sent to the server for handling by that server (e.g., presence sent to the server for
for broadcasting to other entities) MAY legitimately lack a 'to' broadcasting to other entities) MAY legitimately lack a 'to'
attribute. In the 'jabber:server' namespace, a stanza MUST possess a attribute. In the 'jabber:server' namespace, a stanza MUST possess a
'to' attribute. 'to' attribute.
7.2.2 from 7.2.2 from
The 'from' attribute specifies the JID of the sender. The 'from' attribute specifies the JID of the sender.
In the 'jabber:client' namespace, a client MUST NOT include a 'from' In the 'jabber:client' namespace, a client MUST NOT include a 'from'
attribute on the stanzas it sends to a server; if a server receives a attribute on the stanzas it sends to a server; if a server receives a
stanza from a client and the stanza possesses a 'from' attribute, it stanza from a client and the stanza possesses a 'from' attribute, it
MUST ignore the value of the 'from' attribute and MAY return an error MUST ignore the value of the 'from' attribute and MAY return an error
to the sender. In addition, a server MUST stamp stanzas received to the sender. In addition, a server MUST stamp stanzas received from
from a client with the user@domain/resource (full JID) of the a client with the user@domain/resource (full JID) of the connected
connected resource that generated the stanza. resource that generated the stanza.
In the 'jabber:server' namespace, a stanza MUST possess a 'from' In the 'jabber:server' namespace, a stanza MUST possess a 'from'
attribute. In particular, a server MUST include a 'from' attribute attribute. In particular, a server MUST include a 'from' attribute on
on stanzas it routes to other servers. The domain identifier of the stanzas it routes to other servers. The domain identifier of the JID
JID contained in the 'from' attribute MUST match the hostname of the contained in the 'from' attribute MUST match the hostname of the
server (or a subdomain thereof) as communicated in the SASL server (or a subdomain thereof) as communicated in the SASL
negotiation or dialback negotiation. negotiation or dialback negotiation.
7.2.3 id 7.2.3 id
The optional 'id' attribute MAY be used to track stanzas sent and The optional 'id' attribute MAY be used to track stanzas sent and
received. The 'id' attribute is generated by the sender. An 'id' received. The 'id' attribute is generated by the sender. An 'id'
attribute included in an IQ request of type "get" or "set" SHOULD be attribute included in an IQ request of type "get" or "set" SHOULD be
returned to the sender in any IQ response of type "result" or "error" returned to the sender in any IQ response of type "result" or "error"
generated by the recipient of the request. A recipient of a message generated by the recipient of the request. A recipient of a message
skipping to change at page 39, line 8 skipping to change at page 39, line 8
Message stanzas in the 'jabber:client' or 'jabber:server' namespace Message stanzas in the 'jabber:client' or 'jabber:server' namespace
are used to "push" information to another entity. Common uses in the are used to "push" information to another entity. Common uses in the
context of instant messaging include single messages, messages sent context of instant messaging include single messages, messages sent
in the context of a chat conversation, messages sent in the context in the context of a chat conversation, messages sent in the context
of a multi-user chat room, headlines, and errors. These messages of a multi-user chat room, headlines, and errors. These messages
types are identified more fully below. types are identified more fully below.
7.3.1 Types of Message 7.3.1 Types of Message
The 'type' attribute of a message stanza is OPTIONAL; if included, it The 'type' attribute of a message stanza is OPTIONAL; if included, it
specifies the conversational context of the message. The sending of specifies the conversational context of the message. The sending of a
a message stanza without a 'type' attribute signals that the message message stanza without a 'type' attribute signals that the message
stanza is a single message. However, the 'type' attribute MAY also stanza is a single message. However, the 'type' attribute MAY also
have one of the following values: have one of the following values:
o chat o chat
o error o error
o groupchat o groupchat
o headline o headline
skipping to change at page 39, line 36 skipping to change at page 39, line 36
As described under extended namespaces (Section 7.6), a message As described under extended namespaces (Section 7.6), a message
stanza MAY contain any properly-namespaced child element as long as stanza MAY contain any properly-namespaced child element as long as
the namespace name is not "jabber:client", "jabber:server", or the namespace name is not "jabber:client", "jabber:server", or
"http://etherx.jabber.org/streams", and as long as the element name "http://etherx.jabber.org/streams", and as long as the element name
does not match that of one of the core data elements, stream does not match that of one of the core data elements, stream
elements, or defined children thereof. elements, or defined children thereof.
In accordance with the default namespace declaration, by default a In accordance with the default namespace declaration, by default a
message stanza is in the 'jabber:client' or 'jabber:server' message stanza is in the 'jabber:client' or 'jabber:server'
namespace, which defines certain allowable children of message namespace, which defines certain allowable children of message
stanzas. If the message stanza is of type "error", it MUST include stanzas. If the message stanza is of type "error", it MUST include an
an <error/> child; for details, see Section 7.7. If the message <error/> child; for details, see Section 7.7. If the message stanza
stanza has no 'type' attribute or has a 'type' attribute with a value has no 'type' attribute or has a 'type' attribute with a value of
of "chat", "groupchat", or "headline", it MAY contain any of the "chat", "groupchat", or "headline", it MAY contain any of the
following child elements without an explicit namespace declaration: following child elements without an explicit namespace declaration:
7.3.2.1 Body 7.3.2.1 Body
The <body/> element contains the textual contents of the message; The <body/> element contains the textual contents of the message;
normally included but NOT REQUIRED. The <body/> element MUST NOT normally included but NOT REQUIRED. The <body/> element MUST NOT
possess any attributes, with the exception of the 'xml:lang' possess any attributes, with the exception of the 'xml:lang'
attribute. Multiple instances of the <body/> element MAY be included attribute. Multiple instances of the <body/> element MAY be included
but only if each instance possesses an 'xml:lang' attribute with a but only if each instance possesses an 'xml:lang' attribute with a
distinct language value. The <body> element MUST NOT contain mixed distinct language value. The <body> element MUST NOT contain mixed
content. content.
7.3.2.2 Subject 7.3.2.2 Subject
The <subject/> element specifies the topic of the message. The The <subject/> element specifies the topic of the message. The
<subject/> element MUST NOT possess any attributes, with the <subject/> element MUST NOT possess any attributes, with the
exception of the 'xml:lang' attribute. Multiple instances of the exception of the 'xml:lang' attribute. Multiple instances of the
<subject/> element MAY be included for the purpose of providing <subject/> element MAY be included for the purpose of providing
alternate versions of the same subject, but only if each instance alternate versions of the same subject, but only if each instance
possesses an 'xml:lang' attribute with a distinct language value. possesses an 'xml:lang' attribute with a distinct language value. The
The <subject> element MUST NOT contain mixed content. <subject> element MUST NOT contain mixed content.
7.3.2.3 Thread 7.3.2.3 Thread
The <thread/> element contains a random string that is generated by The <thread/> element contains a random string that is generated by
the sender and that SHOULD be copied back in replies; it is used for the sender and that SHOULD be copied back in replies; it is used for
tracking a conversation thread (sometimes referred to as an "IM tracking a conversation thread (sometimes referred to as an "IM
session") between two entities. If used, it MUST be unique to that session") between two entities. If used, it MUST be unique to that
conversation thread within the stream and MUST be consistent conversation thread within the stream and MUST be consistent
throughout that conversation. The use of the <thread/> element is throughout that conversation. The use of the <thread/> element is
optional and is not used to identify individual messages, only optional and is not used to identify individual messages, only
conversations. Only one <thread/> element MAY be included in a conversations. Only one <thread/> element MAY be included in a
message stanza, and it MUST NOT possess any attributes. The <thread/ message stanza, and it MUST NOT possess any attributes. The <thread/>
> element MUST be treated as an opaque string by entities; no element MUST be treated as an opaque string by entities; no semantic
semantic meaning may be derived from it, and only exact, case- meaning may be derived from it, and only exact, case-insensitve
insensitve comparisons be made against it. The <thread> element MUST comparisons be made against it. The <thread> element MUST NOT contain
NOT contain mixed content. mixed content.
The method for generating thread IDs SHOULD be as follows: The method for generating thread IDs SHOULD be as follows:
1. concatenate the sender's full JID (user@host/resource) with the 1. concatenate the sender's full JID (user@host/resource) with the
recipient's full JID recipient's full JID
2. concatenate these JID strings with a full ISO-8601 timestamp 2. concatenate these JID strings with a full ISO-8601 timestamp
including year, month, day, hours, minutes, seconds, and UTC including year, month, day, hours, minutes, seconds, and UTC
offset in the following format: yyyy-mm-dd-Thh:mm:ss-hh:mm offset in the following format: yyyy-mm-dd-Thh:mm:ss-hh:mm
skipping to change at page 42, line 13 skipping to change at page 42, line 13
stanzas. If the presence stanza is of type "error", it MUST include stanzas. If the presence stanza is of type "error", it MUST include
an <error/> child; for details, see Section 7.7. If the presence an <error/> child; for details, see Section 7.7. If the presence
stanza possesses no 'type' attribute, it MAY contain any of the stanza possesses no 'type' attribute, it MAY contain any of the
following child elements (note that the <status/> child MAY be sent following child elements (note that the <status/> child MAY be sent
in a presence stanza of type "unavailable" or, for historical in a presence stanza of type "unavailable" or, for historical
reasons, "subscribe"): reasons, "subscribe"):
7.4.2.1 Show 7.4.2.1 Show
The <show/> element specifies describes the availability status of an The <show/> element specifies describes the availability status of an
entity or specific resource. Only one <show/> element MAY be entity or specific resource. Only one <show/> element MAY be included
included in a presence stanza, and it MUST NOT possess any in a presence stanza, and it MUST NOT possess any attributes. The
attributes. The value SHOULD be one of the following (values other value SHOULD be one of the following (values other than these four
than these four MAY be ignored; additional availability types could MAY be ignored; additional availability types could be defined
be defined through a properly-namespaced child element of the through a properly-namespaced child element of the presence stanza):
presence stanza):
o away o away
o chat o chat
o xa o xa
o dnd o dnd
For information about the meaning of these values, refer to XMPP IM For information about the meaning of these values, refer to XMPP IM
[2]. [2].
7.4.2.2 Status 7.4.2.2 Status
The optional <status/> element specifies a natural-language The optional <status/> element specifies a natural-language
description of availability status. It is normally used in description of availability status. It is normally used in
conjunction with the show element to provide a detailed description conjunction with the show element to provide a detailed description
of an availability state (e.g., "In a meeting"). The <status/> of an availability state (e.g., "In a meeting"). The <status/>
element MUST NOT possess any attributes, with the exception of the element MUST NOT possess any attributes, with the exception of the
'xml:lang' attribute. Multiple instances of the <status/> element 'xml:lang' attribute. Multiple instances of the <status/> element MAY
MAY be included but only if each instance possesses an 'xml:lang' be included but only if each instance possesses an 'xml:lang'
attribute with a distinct language value. attribute with a distinct language value.
7.4.2.3 Priority 7.4.2.3 Priority
The optional <priority/> element specifies the priority level of the The optional <priority/> element specifies the priority level of the
connected resource. The value may be any integer between -128 to connected resource. The value may be any integer between -128 to 127.
127. Only one <priority/> element MAY be included in a presence Only one <priority/> element MAY be included in a presence stanza,
stanza, and it MUST NOT possess any attributes. For information and it MUST NOT possess any attributes. For information regarding the
regarding the use of priority values in stanza routing within IM use of priority values in stanza routing within IM applications, see
applications, see XMPP IM [2]. XMPP IM [2].
7.5 IQ Stanzas 7.5 IQ Stanzas
7.5.1 Overview 7.5.1 Overview
Info/Query, or IQ, is a request-response mechanism, similar in some Info/Query, or IQ, is a request-response mechanism, similar in some
ways to HTTP [24]. IQ stanzas in the 'jabber:client' or ways to HTTP [24]. IQ stanzas in the 'jabber:client' or
'jabber:server' namespace enable an entity to make a request of, and 'jabber:server' namespace enable an entity to make a request of, and
receive a response from, another entity. The data content of the receive a response from, another entity. The data content of the
request and response is defined by the namespace declaration of a request and response is defined by the namespace declaration of a
skipping to change at page 44, line 40 skipping to change at page 44, line 39
7.6 Extended Namespaces 7.6 Extended Namespaces
While the core data elements in the "jabber:client" or While the core data elements in the "jabber:client" or
"jabber:server" namespace (along with their attributes and child "jabber:server" namespace (along with their attributes and child
elements) provide a basic level of functionality for messaging and elements) provide a basic level of functionality for messaging and
presence, XMPP uses XML namespaces to extend the core data elements presence, XMPP uses XML namespaces to extend the core data elements
for the purpose of providing additional functionality. Thus a for the purpose of providing additional functionality. Thus a
message, presence, or IQ stanza MAY house one or more optional child message, presence, or IQ stanza MAY house one or more optional child
elements containing content that extends the meaning of the message elements containing content that extends the meaning of the message
(e.g., an encrypted form of the message body). This child element (e.g., an encrypted form of the message body). This child element MAY
MAY be any element (other than the core data elements, stream be any element (other than the core data elements, stream elements,
elements, or defined children thereof). The child element MUST or defined children thereof). The child element MUST possess an
possess an 'xmlns' namespace declaration (other than the stream 'xmlns' namespace declaration (other than the stream namespace and
namespace and the default namespace) that defines all data contained the default namespace) that defines all data contained within the
within the child element. child element.
Support for any given extended namespace is OPTIONAL on the part of Support for any given extended namespace is OPTIONAL on the part of
any implementation. If an entity does not understand such a any implementation. If an entity does not understand such a
namespace, it MUST ignore the associated XML data (if the stanza is namespace, it MUST ignore the associated XML data (if the stanza is
being routed on to another entity, ignore means "pass it on being routed on to another entity, ignore means "pass it on
untouched"). If an entity receives a message or presence stanza that untouched"). If an entity receives a message or presence stanza that
contains XML data in an extended namespace it does not understand, contains XML data in an extended namespace it does not understand,
the portion of the stanza that is in the unknown namespace SHOULD be the portion of the stanza that is in the unknown namespace SHOULD be
ignored. If an entity receives a message stanza without a <body/> ignored. If an entity receives a message stanza without a <body/>
element but containing only a child element bound by a namespace it element but containing only a child element bound by a namespace it
skipping to change at page 46, line 14 skipping to change at page 46, line 12
The value of the 'class' attribute must be one of the following: The value of the 'class' attribute must be one of the following:
o access -- the condition relates to access rights, permissions, or o access -- the condition relates to access rights, permissions, or
authorization authorization
o address -- the condition relates to the JID or domain to which the o address -- the condition relates to the JID or domain to which the
stanza was addressed stanza was addressed
o app -- the condition is particular to an application and is o app -- the condition is particular to an application and is
specified in a namespace other than 'urn:ietf:params:xml:ns:xmpp- specified in a namespace other than
stanzas' 'urn:ietf:params:xml:ns:xmpp-stanzas'
o format -- the condition relates to XML format or structure o format -- the condition relates to XML format or structure
o recipient -- the condition relates to the state or capabilities of o recipient -- the condition relates to the state or capabilities of
the recipient (which may be the server) the recipient (which may be the server)
o server -- the condition relates to the internal state of the o server -- the condition relates to the internal state of the
server server
The <stanza-condition/> element MUST contain a child element that The <stanza-condition/> element MUST contain a child element that
specifies a particular stanza-related error condition, as defined in specifies a particular stanza-related error condition, as defined in
the next section. (Note: the XML namespace name the next section. (Note: the XML namespace name
'urn:ietf:params:xml:ns:xmpp-stanzas' that scopes the <stanza- 'urn:ietf:params:xml:ns:xmpp-stanzas' that scopes the
condition/> element adheres to the format defined in The IETF XML <stanza-condition/> element adheres to the format defined in The IETF
Registry [15].) XML Registry [15].)
7.7.3 Conditions 7.7.3 Conditions
The following stanza-related error conditions are defined: The following stanza-related error conditions are defined:
o <bad-request/> -- the sender has sent XML that is malformed or o <bad-request/> -- the sender has sent XML that is malformed or
cannot be processed (e.g., a client-generated stanza includes a cannot be processed (e.g., a client-generated stanza includes a
'from' address, or an IQ stanza includes an unrecognized value of 'from' address, or an IQ stanza includes an unrecognized value of
the 'type' attribute); the associated class is "format". the 'type' attribute); the associated class is "format".
skipping to change at page 47, line 36 skipping to change at page 47, line 34
as part or all of the JID of the intended recipient could not be as part or all of the JID of the intended recipient could not be
contacted within a reasonable amount of time; the associated class contacted within a reasonable amount of time; the associated class
is "server". is "server".
o <service-unavailable/> -- the service requested is currently o <service-unavailable/> -- the service requested is currently
unavailable on the server; the associated class is "server". unavailable on the server; the associated class is "server".
7.7.4 Extensibility 7.7.4 Extensibility
If desired, an XMPP application MAY provide custom error information; If desired, an XMPP application MAY provide custom error information;
this MUST be contained in a properly-namespaced child of the <stanza- this MUST be contained in a properly-namespaced child of the
condition/> element (i.e., the namespace name MUST NOT be one of <stanza-condition/> element (i.e., the namespace name MUST NOT be one
namespace names defined herein). of namespace names defined herein).
8. XML Usage within XMPP 8. XML Usage within XMPP
8.1 Restrictions 8.1 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 messages and presence information in elements in order to exchange messages and presence information in
close to real time. Because XMPP does not require the parsing of close to real time. Because XMPP does not require the parsing of
arbitrary and complete XML documents, there is no requirement that arbitrary and complete XML documents, there is no requirement that
XMPP must support the full XML specification [1]. In particular, the XMPP must support the full XML specification [1]. In particular, the
skipping to change at page 48, line 34 skipping to change at page 48, line 34
o internal or external entity references (Section 4.2) with the o internal or external entity references (Section 4.2) with the
exception of predefined entities (Section 4.6) exception of predefined entities (Section 4.6)
With regard to XML processing, if an XMPP implementation receives With regard to XML processing, if an XMPP implementation receives
such restricted XML data, it MUST ignore the data. such restricted XML data, it MUST ignore the data.
8.2 Namespaces 8.2 Namespaces
XML Namespaces [14] are used within all XMPP-compliant XML to create XML Namespaces [14] are used within all XMPP-compliant XML to create
strict boundaries of data ownership. The basic function of strict boundaries of data ownership. The basic function of namespaces
namespaces is to separate different vocabularies of XML elements that is to separate different vocabularies of XML elements that are
are structurally mixed together. Ensuring that XMPP-compliant XML is structurally mixed together. Ensuring that XMPP-compliant XML is
namespace-aware enables any XML to be structurally mixed with any namespace-aware enables any XML to be structurally mixed with any
data element within XMPP. data element within XMPP.
Additionally, XMPP is more strict about namespace prefixes than the Additionally, XMPP is more strict about namespace prefixes than the
XML namespace specification requires. XML namespace specification requires.
8.3 Validation 8.3 Validation
A server is not responsible for validating the XML elements forwarded A server is not responsible for validating the XML elements forwarded
to a client or another server; an implementation MAY choose to to a client or another server; an implementation MAY choose to
skipping to change at page 49, line 10 skipping to change at page 49, line 10
conform to the schemas, and SHOULD ignore any non-conformant elements conform to the schemas, and SHOULD ignore any non-conformant elements
or attributes on the incoming XML stream. Validation of XML streams or attributes on the incoming XML stream. Validation of XML streams
and stanzas is NOT REQUIRED or recommended, and schemas are included and stanzas is NOT REQUIRED or recommended, and schemas are included
herein for descriptive purposes only. herein for descriptive purposes only.
8.4 Character Encodings 8.4 Character Encodings
Software implementing XML streams MUST support the UTF-8 (RFC 2279 Software implementing XML streams MUST support the UTF-8 (RFC 2279
[25]) and UTF-16 (RFC 2781 [26]) transformations of Universal [25]) and UTF-16 (RFC 2781 [26]) transformations of Universal
Character Set (ISO/IEC 10646-1 [27]) characters. Software MUST NOT Character Set (ISO/IEC 10646-1 [27]) characters. Software MUST NOT
attempt to use any other encoding for transmitted data. The attempt to use any other encoding for transmitted data. The encodings
encodings of the transmitted and received streams are independent. of the transmitted and received streams are independent. Software MAY
Software MAY select either UTF-8 or UTF-16 for the transmitted select either UTF-8 or UTF-16 for the transmitted stream, and SHOULD
stream, and SHOULD deduce the encoding of the received stream as deduce the encoding of the received stream as described in the XML
described in the XML specification [1]. For historical reasons, specification [1]. For historical reasons, existing implementations
existing implementations MAY support UTF-8 only. MAY support UTF-8 only.
8.5 Inclusion of Text Declaration 8.5 Inclusion of Text Declaration
An application MAY send a text declaration. Applications MUST follow An application MAY send a text declaration. Applications MUST follow
the rules in the XML specification [1] regarding the circumstances the rules in the XML specification [1] regarding the circumstances
under which a text declaration is included. under which a text declaration is included.
9. IANA Considerations 9. IANA Considerations
9.1 XML Namespace Name for Stream Errors 9.1 XML Namespace Name for Stream Errors
skipping to change at page 51, line 8 skipping to change at page 51, line 8
The IANA registers "xmpp" as a GSSAPI [29] service name, as specified The IANA registers "xmpp" as a GSSAPI [29] service name, as specified
in Section 6.1.3. in Section 6.1.3.
Additionally, the IANA registers "jabber-client" and "jabber-server" Additionally, the IANA registers "jabber-client" and "jabber-server"
as keywords for TCP ports 5222 and 5269 respectively. as keywords for TCP ports 5222 and 5269 respectively.
10. Internationalization Considerations 10. Internationalization Considerations
Usage of the 'xml:lang' attribute is described above. If a client Usage of the 'xml:lang' attribute is described above. If a client
includes an 'xml:lang' attribute in a stanza, the server MUST NOT includes an 'xml:lang' attribute in a stanza, a server MUST NOT
modify or delete it. modify or delete it.
11. Security Considerations 11. Security Considerations
11.1 High Security 11.1 High Security
For the purposes of XMPP communications (client-to-server and server- For the purposes of XMPP communications (client-to-server and
to-server), the term "high security" refers to the use of security server-to-server), the term "high security" refers to the use of
technologies that provide both mutual authentication and integrity- security technologies that provide both mutual authentication and
checking; in particular, when using certificate-based authentication integrity-checking; in particular, when using certificate-based
to provide high security, a chain-of-trust must be established out- authentication to provide high security, a chain-of-trust must be
of-band (i.e., no self-signed certificates). established out-of-band (i.e., self-signed certificates are not
sufficient).
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.
11.2 Client-to-Server Communications 11.2 Client-to-Server Communications
The TLS protocol for encrypting XML streams (defined under Section 5) The TLS protocol for encrypting XML streams (defined under Section 5)
provides a reliable mechanism for helping to ensure the 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.
skipping to change at page 52, line 41 skipping to change at page 52, line 42
available by a server, nor are any connections other than the available by a server, nor are any connections other than the
original server connection required. This helps protect the client's original server connection required. This helps protect the client's
server from direct attack or identification by third parties. server from direct attack or identification by third parties.
End-to-end encryption of message bodies and presence status End-to-end encryption of message bodies and presence status
information MAY be effected through use of the methods defined in information MAY be effected through use of the methods defined in
End-to-End Object Encryption in XMPP [28]. End-to-End Object Encryption in XMPP [28].
11.3 Server-to-Server Communications 11.3 Server-to-Server Communications
A compliant implementation MUST support both TLS and SASL for inter- A compliant implementation MUST support both TLS and SASL for
domain communications. For historical reasons, a compliant inter-domain communications. For historical reasons, a compliant
implementation SHOULD also support the lower-security Dialback implementation SHOULD also support the lower-security Dialback
Protocol (Section 6.2), which provides a mechanism for helping to Protocol (Section 6.2), which provides a mechanism for helping to
prevent the spoofing of domains. prevent the spoofing of domains.
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 server- for any given domain to communicate with other domains, and
to-server communications MAY be disabled by the administrator of any server-to-server communications MAY be disabled by the administrator
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. In the absence of communications, it SHOULD enable high security. In the absence of
high security, a domain MAY use server dialback for inter-domain high security, a domain MAY use server dialback for inter-domain
communications. communications.
11.4 Firewalls 11.4 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 [6]. Use of these well-known ports allows registered with the IANA [6]. Use of these well-known ports allows
administrators to easily enable or disable XMPP activity through administrators to easily enable or disable XMPP activity through
skipping to change at page 54, line 11 skipping to change at page 54, line 11
for both: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher for both: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher
supporting client-side certificates) supporting client-side certificates)
References References
[1] World Wide Web Consortium, "Extensible Markup Language (XML) [1] World Wide Web Consortium, "Extensible Markup Language (XML)
1.0 (Second Edition)", W3C xml, October 2000, <http:// 1.0 (Second Edition)", W3C xml, October 2000, <http://
www.w3.org/TR/2000/REC-xml-20001006>. www.w3.org/TR/2000/REC-xml-20001006>.
[2] Saint-Andre, P. and J. Miller, "XMPP Instant Messaging (draft- [2] Saint-Andre, P. and J. Miller, "XMPP Instant Messaging
ietf-xmpp-im-07, work in progress)", April 2003. (draft-ietf-xmpp-im-08, work in progress)", April 2003.
[3] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for [3] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for
Presence and Instant Messaging", RFC 2779, February 2000, Presence and Instant Messaging", RFC 2779, February 2000,
<http://www.ietf.org/rfc/rfc2779.txt>. <http://www.ietf.org/rfc/rfc2779.txt>.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[5] University of Southern California, "Transmission Control [5] University of Southern California, "Transmission Control
Protocol", RFC 793, September 1981, <http://www.ietf.org/rfc/ Protocol", RFC 793, September 1981, <http://www.ietf.org/rfc/
skipping to change at page 54, line 46 skipping to change at page 54, line 46
Support", STD 3, RFC 1123, October 1989. Support", STD 3, RFC 1123, October 1989.
[10] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile [10] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile
for Internationalized Domain Names (draft-ietf-idn-nameprep-11, for Internationalized Domain Names (draft-ietf-idn-nameprep-11,
work in progress)", June 2002. work in progress)", June 2002.
[11] Hoffman, P. and M. Blanchet, "Preparation of Internationalized [11] Hoffman, P. and M. Blanchet, "Preparation of Internationalized
Strings ("stringprep")", RFC 3454, December 2002. Strings ("stringprep")", RFC 3454, December 2002.
[12] Saint-Andre, P. and J. Hildebrand, "Nodeprep: A Stringprep [12] Saint-Andre, P. and J. Hildebrand, "Nodeprep: A Stringprep
Profile for Node Identifiers in XMPP (draft-ietf-xmpp-nodeprep- Profile for Node Identifiers in XMPP
01, work in progress)", February 2003. (draft-ietf-xmpp-nodeprep-01, work in progress)", February
2003.
[13] Saint-Andre, P. and J. Hildebrand, "Resourceprep: A Stringprep [13] Saint-Andre, P. and J. Hildebrand, "Resourceprep: A Stringprep
Profile for Resource Identifiers in XMPP (draft-ietf-xmpp- Profile for Resource Identifiers in XMPP
resourceprep-01, work in progress)", February 2003. (draft-ietf-xmpp-resourceprep-01, work in progress)", February
2003.
[14] World Wide Web Consortium, "Namespaces in XML", W3C xml-names, [14] World Wide Web Consortium, "Namespaces in XML", W3C xml-names,
January 1999, <http://www.w3.org/TR/1999/REC-xml-names- January 1999, <http://www.w3.org/TR/1999/
19990114/>. REC-xml-names-19990114/>.
[15] Mealling, M., "The IANA XML Registry", draft-mealling-iana- [15] Mealling, M., "The IANA XML Registry",
xmlns-registry-04 (work in progress), June 2002. draft-mealling-iana-xmlns-registry-04 (work in progress), June
2002.
[16] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and [16] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and
P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January
1999. 1999.
[17] Crispin, M., "Internet Message Access Protocol - Version [17] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 2060, December 1996. 4rev1", RFC 2060, December 1996.
[18] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD [18] Myers, J. and M. Rose, "Post Office Protocol - Version 3", STD
53, RFC 1939, May 1996. 53, RFC 1939, May 1996.
skipping to change at page 69, line 10 skipping to change at page 69, line 10
<xs:element name='remote-server-timeout' type='xs:string'/> <xs:element name='remote-server-timeout' type='xs:string'/>
<xs:element name='service-unavailable' type='xs:string'/> <xs:element name='service-unavailable' type='xs:string'/>
</xs:schema> </xs:schema>
Appendix B. Revision History Appendix B. 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.
B.1 Changes from draft-ietf-xmpp-core-06 B.1 Changes from draft-ietf-xmpp-core-07
o Made several small editorial changes.
B.2 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 [15]. to the format defined in The IETF XML Registry [15].
o Removed note to RFC editor regarding provisional namespace names. o Removed note to RFC editor regarding provisional namespace names.
B.2 Changes from draft-ietf-xmpp-core-05 B.3 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.
B.3 Changes from draft-ietf-xmpp-core-04 B.4 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.
B.4 Changes from draft-ietf-xmpp-core-03 B.5 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.
B.5 Changes from draft-ietf-xmpp-core-02 B.6 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".
B.6 Changes from draft-ietf-xmpp-core-01 B.7 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 Stream Authentication regarding "version='1.0'" o Corrected error in Stream Authentication regarding "version='1.0'"
flag. flag.
o Made numerous small editorial changes. o Made numerous small editorial changes.
B.7 Changes from draft-ietf-xmpp-core-00 B.8 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.
B.8 Changes from draft-miller-xmpp-core-02 B.9 Changes from draft-miller-xmpp-core-02
o Brought Streams Authentication section into line with discussion o Brought Streams Authentication section into line with discussion
on list and at IETF 55 meeting. on list and 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 72, line 5 skipping to change at page 72, line 5
o Noted that XMPP activity respects firewall administration o Noted that XMPP activity respects firewall administration
policies. policies.
o Further specified the scope and uniqueness of the 'id' attribute o Further specified the scope and uniqueness of the 'id' attribute
in all stanza types and the <thread/> element in message stanzas. in all stanza types and the <thread/> element in message stanzas.
o Nomenclature changes: (1) from "chunks" to "stanzas"; (2) from o Nomenclature changes: (1) from "chunks" to "stanzas"; (2) from
"host" to "server" and from "node" to "client" (except with regard "host" to "server" and from "node" to "client" (except with regard
to definition of the addressing scheme). to definition of the addressing scheme).
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Acknowledgement Acknowledgement
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