draft-ietf-xmpp-core-24.txt   rfc3920.txt 
XMPP Working Group P. Saint-Andre, Ed. Network Working Group P. Saint-Andre, Ed.
Internet-Draft Jabber Software Foundation Request for Comments: 3920 Jabber Software Foundation
Expires: November 4, 2004 May 6, 2004 Category: Standards Track October 2004
Extensible Messaging and Presence Protocol (XMPP): Core Extensible Messaging and Presence Protocol (XMPP): Core
draft-ietf-xmpp-core-24
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004).
Abstract Abstract
This memo defines the core features of the Extensible Messaging and This memo defines the core features of the Extensible Messaging and
Presence Protocol (XMPP), a protocol for streaming Extensible Markup Presence Protocol (XMPP), a protocol for streaming Extensible Markup
Language (XML) elements in order to exchange structured information Language (XML) elements in order to exchange structured information
in close to real time between any two network endpoints. While XMPP in close to real time between any two network endpoints. While XMPP
provides a generalized, extensible framework for exchanging XML data, provides a generalized, extensible framework for exchanging XML data,
it is used mainly for the purpose of building instant messaging and it is used mainly for the purpose of building instant messaging and
presence applications that meet the requirements of RFC 2779. presence applications that meet the requirements of RFC 2779.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Generalized Architecture . . . . . . . . . . . . . . . . . . . 4 2. Generalized Architecture . . . . . . . . . . . . . . . . . . 3
3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . . 5 3. Addressing Scheme . . . . . . . . . . . . . . . . . . . . . 5
4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. XML Streams . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. Use of TLS . . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . . 26 6. Use of SASL . . . . . . . . . . . . . . . . . . . . . . . . 27
7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . . 36 7. Resource Binding . . . . . . . . . . . . . . . . . . . . . . 37
8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . . 39 8. Server Dialback . . . . . . . . . . . . . . . . . . . . . . 41
9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . . 47 9. XML Stanzas . . . . . . . . . . . . . . . . . . . . . . . . 48
10. Server Rules for Handling XML Stanzas . . . . . . . . . . . . 56 10. Server Rules for Handling XML Stanzas . . . . . . . . . . . 58
11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . . 58 11. XML Usage within XMPP . . . . . . . . . . . . . . . . . . . 60
12. Core Compliance Requirements . . . . . . . . . . . . . . . . . 60 12. Core Compliance Requirements . . . . . . . . . . . . . . . . 62
13. Internationalization Considerations . . . . . . . . . . . . . 61 13. Internationalization Considerations . . . . . . . . . . . . 64
14. Security Considerations . . . . . . . . . . . . . . . . . . . 62 14. Security Considerations . . . . . . . . . . . . . . . . . . 64
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 69
Normative References . . . . . . . . . . . . . . . . . . . . . 69 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 71
Informative References . . . . . . . . . . . . . . . . . . . . 71 A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 72 B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . 76
A. Nodeprep . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . 78
B. Resourceprep . . . . . . . . . . . . . . . . . . . . . . . . . 74 D. Differences Between Core Jabber Protocols and XMPP . . . . . 87
C. XML Schemas . . . . . . . . . . . . . . . . . . . . . . . . . 75 Contributors. . . . . . . . . . . . . . . . . . . . . . . . . . . 89
D. Differences Between Core Jabber Protocols and XMPP . . . . . . 84 Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . 89
Intellectual Property and Copyright Statements . . . . . . . . 86 Author's Address. . . . . . . . . . . . . . . . . . . . . . . . . 89
Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . 90
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] protocol for near-real-time messaging, presence, and Extensible Markup Language [XML] protocol for near-real-time
request-response services. The basic syntax and semantics were messaging, presence, and request-response services. The basic syntax
developed originally within the Jabber open-source community, mainly and semantics were developed originally within the Jabber open-source
in 1999. In 2002, the XMPP WG was chartered with developing an community, mainly in 1999. In 2002, the XMPP WG was chartered with
adaptation of the Jabber protocol that would be suitable as an IETF developing an adaptation of the Jabber protocol that would be
instant messaging (IM) and presence technology. As a result of work suitable as an IETF instant messaging (IM) and presence technology.
by the XMPP WG, the current memo defines the core features of XMPP As a result of work by the XMPP WG, the current memo defines the core
1.0; the extensions required to provide the instant messaging and features of XMPP 1.0; the extensions required to provide the instant
presence functionality defined in RFC 2779 [IMP-REQS] are specified messaging and presence functionality defined in RFC 2779 [IMP-REQS]
in Extensible Messaging and Presence Protocol (XMPP): Instant are specified in the Extensible Messaging and Presence Protocol
Messaging and Presence [XMPP-IM]. (XMPP): Instant Messaging and Presence [XMPP-IM].
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 BCP
2119 [TERMS]. 14, RFC 2119 [TERMS].
1.3 Contributors
Most of the core aspects of the Extensible Messaging and Presence
Protocol were developed originally within the Jabber open-source
community in 1999. This community was founded by Jeremie Miller, who
released source code for the initial version of the jabberd server in
January 1999. Major early contributors to the base protocol also
included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave
Smith. Work by the XMPP Working Group has concentrated especially on
security and internationalization; in these areas, protocols for the
use of TLS and SASL were originally contributed by Rob Norris, and
stringprep profiles were originally contributed by Joe Hildebrand.
The error code syntax was suggested by Lisa Dusseault.
1.4 Acknowledgements
Thanks are due to a number of individuals in addition to the
contributors listed. Although it is difficult to provide a complete
list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan
Hogg, Cullen Jennings, Craig Kaes, Jacek Konieczny, Alexey Melnikov,
Keith Minkler, Julian Missig, Pete Resnick, Marshall Rose, Alexey
Shchepin, Jean-Louis Seguineau, Iain Shigeoka, Greg Troxel, and David
Waite. Thanks also to members of the XMPP Working Group and the IETF
community for comments and feedback provided throughout the life of
this memo.
2. 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
date it usually has been implemented via a client-server architecture date it usually has been implemented via a client-server architecture
wherein a client utilizing XMPP accesses a server over a [TCP] wherein a client utilizing XMPP accesses a server over a [TCP]
connection, and servers also communicate with each other over TCP connection, and servers also communicate with each other over TCP
connections. connections.
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).
skipping to change at page 4, line 29 skipping to change at page 3, line 33
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:
o C1, C2, C3 = XMPP clients o C1, C2, C3 = XMPP clients
o S1, S2 = XMPP servers o S1, S2 = XMPP servers
o G1 = A gateway that translates between XMPP and the protocol(s) o G1 = A gateway that translates between XMPP and the protocol(s)
used on a foreign (non-XMPP) messaging network used on a foreign (non-XMPP) messaging network
o FN1 = A foreign messaging network o FN1 = A foreign messaging network
o FC1 = A client on a foreign messaging network o FC1 = A client on a foreign messaging network
2.2 Server 2.2. Server
A server acts as an intelligent abstraction layer for XMPP A server acts as an intelligent abstraction layer for XMPP
communications. Its primary responsibilities are: communications. Its primary responsibilities are:
o to manage connections from or sessions for other entities, in the o to manage connections from or sessions for other entities, in the
form of XML streams (Section 4) to and from authorized clients, form of XML streams (Section 4) to and from authorized clients,
servers, and other entities servers, and other entities
o to route appropriately-addressed XML stanzas (Section 9) among o to route appropriately-addressed XML stanzas (Section 9) among
such entities over XML streams such entities over XML streams
Most XMPP-compliant servers also assume responsibility for the Most XMPP-compliant servers also assume responsibility for the
storage of data that is used by clients (e.g., contact lists for storage of data that is used by clients (e.g., contact lists for
users of XMPP-based instant messaging and presence applications); in users of XMPP-based instant messaging and presence applications); in
this case, the XML data is processed directly by the server itself on this case, the XML data is processed directly by the server itself on
behalf of the client and is not routed to another entity. behalf of the client and is not routed to another entity.
2.3 Client 2.3. Client
Most clients connect directly to a server over a [TCP] connection and Most clients connect directly to a server over a [TCP] connection and
use XMPP to take full advantage of the functionality provided by a use XMPP to take full advantage of the functionality provided by a
server and any associated services. Multiple resources (e.g., server and any associated services. Multiple resources (e.g.,
devices or locations) MAY connect simultaneously to a server on devices or locations) MAY connect simultaneously to a server on
behalf of each authorized client, with each resource differentiated behalf of each authorized client, with each resource differentiated
by the resource identifier of an XMPP address (e.g., <node@domain/ by the resource identifier of an XMPP address (e.g., <node@domain/
home> vs. <node@domain/work>) as defined under Addressing Scheme home> vs. <node@domain/work>) as defined under Addressing Scheme
(Section 3). The RECOMMENDED port for connections between a client (Section 3). The RECOMMENDED port for connections between a client
and a server is 5222, as registered with the IANA (see Port Numbers and a server is 5222, as registered with the IANA (see Port Numbers
(Section 15.9)). (Section 15.9)).
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 used by a foreign function is to translate XMPP into the protocol used by a foreign
(non-XMPP) messaging system, as well as to translate the return data (non-XMPP) messaging system, as well as to translate the return data
back into XMPP. Examples are gateways to email (see [SMTP]), back into XMPP. Examples are gateways to email (see [SMTP]),
Internet Relay Chat (see [IRC]), SIMPLE (see [SIMPLE]), Short Message Internet Relay Chat (see [IRC]), SIMPLE (see [SIMPLE]), Short Message
Service (SMS), and legacy instant messaging services such as AIM, Service (SMS), and legacy instant messaging services such as AIM,
ICQ, MSN Messenger, and Yahoo! Instant Messenger. Communications ICQ, MSN Messenger, and Yahoo! Instant Messenger. Communications
between gateways and servers, and between gateways and the foreign between gateways and servers, and between gateways and the foreign
messaging system, are not defined in this document. messaging system, are not defined in this document.
2.5 Network 2.5. Network
Because each server is identified by a network address and because Because each server is identified by a network address and because
server-to-server communications are a straightforward extension of server-to-server communications are a straightforward extension of
the client-to-server protocol, in practice the system consists of a the client-to-server protocol, in practice, the system consists of a
network of servers that inter-communicate. Thus, for example, network of servers that inter-communicate. Thus, for example,
<juliet@example.com> is able to exchange messages, presence, and <juliet@example.com> is able to exchange messages, presence, and
other information with <romeo@example.net>. This pattern is familiar other information with <romeo@example.net>. This pattern is familiar
from messaging protocols (such as [SMTP]) that make use of network from messaging protocols (such as [SMTP]) that make use of network
addressing standards. Communications between any two servers are addressing standards. Communications between any two servers are
OPTIONAL. If enabled, such communications SHOULD occur over XML OPTIONAL. If enabled, such communications SHOULD occur over XML
streams that are bound to [TCP] connections. The RECOMMENDED port streams that are bound to [TCP] connections. The RECOMMENDED port
for connections between servers is 5269, as registered with the IANA for connections between servers is 5269, as registered with the IANA
(see Port Numbers (Section 15.9)). (see Port Numbers (Section 15.9)).
3. Addressing Scheme 3. Addressing Scheme
3.1 Overview 3.1. Overview
An entity is anything that can be considered a network endpoint An entity is anything that can be considered a network endpoint
(i.e., an ID on the network) and that can communicate using XMPP. (i.e., an ID on the network) and that can communicate using XMPP.
All such entities are uniquely addressable in a form that is All such entities are uniquely addressable in a form that is
consistent with RFC 2396 [URI]. For historical reasons, the address consistent with RFC 2396 [URI]. For historical reasons, the address
of an XMPP entity is called a Jabber Identifier or JID. A valid JID of an XMPP entity is called a Jabber Identifier or JID. A valid JID
contains a set of ordered elements formed of a domain identifier, contains a set of ordered elements formed of a domain identifier,
node identifier, and resource identifier. node identifier, and resource identifier.
The syntax for a JID is defined below using Augmented Backus-Naur The syntax for a JID is defined below using the Augmented Backus-Naur
Form as defined in [ABNF]. (The IPv4address and IPv6address rules Form as defined in [ABNF]. (The IPv4address and IPv6address rules
are defined in Appendix B of [IPv6]; the allowable character are defined in Appendix B of [IPv6]; the allowable character
sequences that conform to the node rule are defined by the Nodeprep sequences that conform to the node rule are defined by the Nodeprep
profile of [STRINGPREP] as documented in Appendix A of this memo; the profile of [STRINGPREP] as documented in Appendix A of this memo; the
allowable character sequences that conform to the resource rule are allowable character sequences that conform to the resource rule are
defined by the Resourceprep profile of [STRINGPREP] as documented in defined by the Resourceprep profile of [STRINGPREP] as documented in
Appendix B of this memo; and the sub-domain rule makes reference to Appendix B of this memo; and the sub-domain rule makes reference to
the concept of a domain label as described in [IDNA].) the concept of an internationalized domain label as described in
[IDNA].)
jid = [ node "@" ] domain [ "/" resource ] jid = [ node "@" ] domain [ "/" resource ]
domain = fqdn / address-literal domain = fqdn / address-literal
fqdn = (sub-domain 1*("." sub-domain)) fqdn = (sub-domain 1*("." sub-domain))
sub-domain = ([IDNA] conformant domain label) sub-domain = (internationalized domain label)
address-literal = IPv4address / IPv6address address-literal = IPv4address / IPv6address
All JIDs are based on the foregoing structure. The most common use All JIDs are based on the foregoing structure. The most common use
of this structure is to identify an instant messaging user, the of this structure is to identify an instant messaging user, the
server to which the user connects, and the user's connected resource server to which the user connects, and the user's connected resource
(e.g., a specific client) in the form of <user@host/resource>. (e.g., a specific client) in the form of <user@host/resource>.
However, node types other than clients are possible; for example, a However, node types other than clients are possible; for example, a
specific chat room offered by a multi-user chat service could be specific chat room offered by a multi-user chat service could be
addressed as <room@service> (where "room" is the name of the chat addressed as <room@service> (where "room" is the name of the chat
room and "service" is the hostname of the multi-user chat service) room and "service" is the hostname of the multi-user chat service)
and a specific occupant of such a room could be addressed as and a specific occupant of such a room could be addressed as
<room@service/nick> (where "nick" is the occupant's room nickname). <room@service/nick> (where "nick" is the occupant's room nickname).
Many other JID types are possible (e.g., <domain/resource> could be a Many other JID types are possible (e.g., <domain/resource> could be a
server-side script or service). server-side script or service).
Each allowable portion of a JID (node identifier, domain identifier, Each allowable portion of a JID (node identifier, domain identifier,
and resource identifier) MUST NOT be more than 1023 bytes in length, and resource identifier) MUST NOT be more than 1023 bytes in length,
resulting in a maximum total size (including the '@' and '/' resulting in a maximum total size (including the '@' and '/'
separators) of 3071 bytes. separators) of 3071 bytes.
3.2 Domain Identifier 3.2. Domain Identifier
The domain identifier is the primary identifier and is the only The domain identifier is the primary identifier and is the only
REQUIRED element of a JID (a mere domain identifier is a valid JID). REQUIRED element of a JID (a mere domain identifier is a valid JID).
It usually represents the network gateway or "primary" server to It usually represents the network gateway or "primary" server to
which other entities connect for XML routing and data management which other entities connect for XML routing and data management
capabilities. However, the entity referenced by a domain identifier capabilities. However, the entity referenced by a domain identifier
is not always a server, and may be a service that is addressed as a is not always a server, and may be a service that is addressed as a
subdomain of a server and that provides functionality above and subdomain of a server that provides functionality above and beyond
beyond the capabilities of a server (e.g., a multi-user chat service, the capabilities of a server (e.g., a multi-user chat service, a user
a user directory, or a gateway to a foreign messaging system). directory, or a gateway to a foreign messaging system).
The domain identifier for every server or service that will The domain identifier for every server or service that will
communicate over a network MAY be an IP address but SHOULD be a fully communicate over a network MAY be an IP address but SHOULD be a fully
qualified domain name (see [DNS]). A domain identifier MUST be an qualified domain name (see [DNS]). A domain identifier MUST be an
"internationalized domain name" as defined in [IDNA], to which the "internationalized domain name" as defined in [IDNA], to which the
Nameprep [NAMEPREP] profile of stringprep [STRINGPREP] can be applied Nameprep [NAMEPREP] profile of stringprep [STRINGPREP] can be applied
without failing. Before comparing two domain identifiers, a server without failing. Before comparing two domain identifiers, a server
MUST (and a client SHOULD) first apply the Nameprep profile to the MUST (and a client SHOULD) first apply the Nameprep profile to the
labels (as defined in [IDNA]) that make up each identifier. labels (as defined in [IDNA]) that make up each identifier.
3.3 Node Identifier 3.3. Node Identifier
The node identifier is an optional secondary identifier placed before The node identifier is an optional secondary identifier placed before
the domain identifier and separated from the latter by the '@' the domain identifier and separated from the latter by the '@'
character. It usually represents the entity requesting and using character. It usually represents the entity requesting and using
network access provided by the server or gateway (i.e., a client), network access provided by the server or gateway (i.e., a client),
although it can also represent other kinds of entities (e.g., a chat although it can also represent other kinds of entities (e.g., a chat
room associated with a multi-user chat service). The entity room associated with a multi-user chat service). The entity
represented by a node identifier is addressed within the context of a represented by a node identifier is addressed within the context of a
specific domain; within instant messaging and presence applications specific domain; within instant messaging and presence applications
of XMPP this address is called a "bare JID" and is of the form of XMPP, this address is called a "bare JID" and is of the form
<node@domain>. <node@domain>.
A node identifier MUST be formatted such that the Nodeprep profile of A node identifier MUST be formatted such that the Nodeprep profile of
[STRINGPREP] can be applied to it without failing. Before comparing [STRINGPREP] can be applied to it without failing. Before comparing
two node identifiers, a server MUST (and a client SHOULD) first apply two node identifiers, a server MUST (and a client SHOULD) first apply
the Nodeprep profile to each identifier. the Nodeprep profile to each identifier.
3.4 Resource Identifier 3.4. Resource Identifier
The resource identifier is an optional tertiary identifier placed The resource identifier is an optional tertiary identifier placed
after the domain identifier and separated from the latter by the '/' after the domain identifier and separated from the latter by the '/'
character. A resource identifier may modify either a <node@domain> character. A resource identifier may modify either a <node@domain>
or mere <domain> address. It usually represents a specific session, or a mere <domain> address. It usually represents a specific
connection (e.g., a device or location), or object (e.g., a session, connection (e.g., a device or location), or object (e.g., a
participant in a multi-user chat room) belonging to the entity participant in a multi-user chat room) belonging to the entity
associated with a node identifier. A resource identifier is opaque associated with a node identifier. A resource identifier is opaque
to both servers and other clients, and is typically defined by a to both servers and other clients, and is typically defined by a
client implementation when it provides the information necessary to client implementation when it provides the information necessary to
complete Resource Binding (Section 7) (although it may be generated complete Resource Binding (Section 7) (although it may be generated
by a server on behalf of a client), after which it is referred to as by a server on behalf of a client), after which it is referred to as
a "connected resource". An entity MAY maintain multiple connected a "connected resource". An entity MAY maintain multiple connected
resources simultaneously, with each connected resource differentiated resources simultaneously, with each connected resource differentiated
by a distinct resource identifier. by a distinct resource identifier.
A resource identifier MUST be formatted such that the Resourceprep A resource identifier MUST be formatted such that the Resourceprep
profile of [STRINGPREP] can be applied to it without failing. Before profile of [STRINGPREP] can be applied without failing. Before
comparing two resource identifiers, a server MUST (and a client comparing two resource identifiers, a server MUST (and a client
SHOULD) first apply the Resourceprep profile to each identifier. SHOULD) first apply the Resourceprep profile to each identifier.
3.5 Determination of Addresses 3.5. Determination of Addresses
After SASL negotiation (Section 6) and, if appropriate, Resource After SASL negotiation (Section 6) and, if appropriate, Resource
Binding (Section 7), the receiving entity for a stream MUST determine Binding (Section 7), the receiving entity for a stream MUST determine
the initiating entity's JID. the initiating entity's JID.
For server-to-server communications, the initiating entity's JID For server-to-server communications, the initiating entity's JID
SHOULD be the authorization identity, derived from the authentication SHOULD be the authorization identity, derived from the authentication
identity as defined by the Simple Authentication and Security Layer identity, as defined by the Simple Authentication and Security Layer
(SASL) specification [SASL] if no authorization identity was (SASL) specification [SASL], if no authorization identity was
specified during SASL negotiation (Section 6). specified during SASL negotiation (Section 6).
For client-to-server communications, the "bare JID" (<node@domain>) For client-to-server communications, the "bare JID" (<node@domain>)
SHOULD be the authorization identity, derived from the authentication SHOULD be the authorization identity, derived from the authentication
identity as defined in [SASL] if no authorization identity was identity, as defined in [SASL], if no authorization identity was
specified during SASL negotiation (Section 6); the resource specified during SASL negotiation (Section 6); the resource
identifier portion of the "full JID" (<node@domain/resource>) SHOULD identifier portion of the "full JID" (<node@domain/resource>) SHOULD
be the resource identifier negotiated by the client and server during be the resource identifier negotiated by the client and server during
Resource Binding (Section 7). Resource Binding (Section 7).
The receiving entity MUST ensure that the resulting JID (including The receiving entity MUST ensure that the resulting JID (including
node identifier, domain identifier, resource identifier, and node identifier, domain identifier, resource identifier, and
separator characters) conforms to the rules and formats defined separator characters) conforms to the rules and formats defined
earlier in this section; to meet this restriction, the receiving earlier in this section; to meet this restriction, the receiving
entity may need to replace the JID sent by the initiating entity with entity may need to replace the JID sent by the initiating entity with
the canonicalized JID as determined by the receiving entity. the canonicalized JID as determined by the receiving entity.
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. These between presence-aware entities: XML streams and XML stanzas. These
terms are defined as follows: terms are defined as follows:
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.
The start of an XML stream is denoted unambiguously by an opening The start of an XML stream is denoted unambiguously by an opening
XML <stream> tag (with appropriate attributes and namespace XML <stream> tag (with appropriate attributes and namespace
declarations), while the end of the XML stream is denoted declarations), while the end of the XML stream is denoted
unambiguously by a closing XML </stream> tag. During the life of unambiguously by a closing XML </stream> tag. During the life of
the stream, the entity that initiated it can send an unbounded the stream, the entity that initiated it can send an unbounded
number of XML elements over the stream, either elements used to number of XML elements over the stream, either elements used to
negotiate the stream (e.g., to negotiate use of TLS (Section 5) or negotiate the stream (e.g., to negotiate Use of TLS (Section 5) or
use of SASL (Section 6)) or XML stanzas (as defined herein, use of SASL (Section 6)) or XML stanzas (as defined herein,
<message/>, <presence/>, or <iq/> elements qualified by the <message/>, <presence/>, or <iq/> elements qualified by the
default namespace). The "initial stream" is negotiated from the default namespace). The "initial stream" is negotiated from the
initiating entity (usually a client or server) to the receiving initiating entity (usually a client or server) to the receiving
entity (usually a server), and can be seen as corresponding to the entity (usually a server), and can be seen as corresponding to the
initiating entity's "session" with the receiving entity. The initiating entity's "session" with the receiving entity. The
initial stream enables unidirectional communication from the initial stream enables unidirectional communication from the
initiating entity to the receiving entity; in order to enable initiating entity to the receiving entity; in order to enable
information exchange from the receiving entity to the initiating information exchange from the receiving entity to the initiating
entity, the receiving entity MUST negotiate a stream in the entity, the receiving entity MUST negotiate a stream in the
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<message/>, <presence/>, or <iq/> elements qualified by the <message/>, <presence/>, or <iq/> elements qualified by the
default namespace). The "initial stream" is negotiated from the default namespace). The "initial stream" is negotiated from the
initiating entity (usually a client or server) to the receiving initiating entity (usually a client or server) to the receiving
entity (usually a server), and can be seen as corresponding to the entity (usually a server), and can be seen as corresponding to the
initiating entity's "session" with the receiving entity. The initiating entity's "session" with the receiving entity. The
initial stream enables unidirectional communication from the initial stream enables unidirectional communication from the
initiating entity to the receiving entity; in order to enable initiating entity to the receiving entity; in order to enable
information exchange from the receiving entity to the initiating information exchange from the receiving entity to the initiating
entity, the receiving entity MUST negotiate a stream in the entity, the receiving entity MUST negotiate a stream in the
opposite direction (the "response stream"). opposite direction (the "response stream").
Definition of XML Stanza: An XML stanza is a discrete semantic unit Definition of XML Stanza: An XML stanza is a discrete semantic unit
of structured information that is sent from one entity to another of structured information that is sent from one entity to another
over an XML stream. An XML stanza exists at the direct child over an XML stream. An XML stanza exists at the direct child
level of the root <stream/> element and is said to be level of the root <stream/> element and is said to be
well-balanced if it matches production [43] content of [XML]. The well-balanced if it matches the production [43] content of [XML].
start of any XML stanza is denoted unambiguously by the element The start of any XML stanza is denoted unambiguously by the
start tag at depth=1 of the XML stream (e.g., <presence>), and the element start tag at depth=1 of the XML stream (e.g., <presence>),
end of any XML stanza is denoted unambiguously by the and the end of any XML stanza is denoted unambiguously by the
corresponding close tag at depth=1 (e.g., </presence>). An XML corresponding close tag at depth=1 (e.g., </presence>). An XML
stanza MAY contain child elements (with accompanying attributes, stanza MAY contain child elements (with accompanying attributes,
elements, and XML character data) as necessary in order to convey elements, and XML character data) as necessary in order to convey
the desired information. The only XML stanzas defined herein are the desired information. The only XML stanzas defined herein are
the <message/>, <presence/>, and <iq/> elements qualified by the the <message/>, <presence/>, and <iq/> elements qualified by the
default namespace for the stream, as described under XML Stanzas default namespace for the stream, as described under XML Stanzas
(Section 9); an XML element sent for the purpose of Transport (Section 9); an XML element sent for the purpose of Transport
Layer Security (TLS) negotiation (Section 5), Simple Layer Security (TLS) negotiation (Section 5), Simple
Authentication and Security Layer (SASL) negotiation (Section 6), Authentication and Security Layer (SASL) negotiation (Section 6),
or server dialback (Section 8) is not considered to be an XML or server dialback (Section 8) is not considered to be an XML
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server), after which both the client and server SHOULD terminate the server), after which both the client and server SHOULD terminate the
underlying connection (usually a TCP connection) as well. underlying connection (usually a TCP connection) as well.
Those who are accustomed to thinking of XML in a document-centric Those who are accustomed to thinking of XML in a document-centric
manner may wish to view a client's session with a server as manner may wish to view a client's session with a server as
consisting of two open-ended XML documents: one from the client to consisting of two open-ended XML documents: one from the client to
the server and one from the server to the client. From this the server and one from the server to the client. From this
perspective, the root <stream/> element can be considered the perspective, the root <stream/> element can be considered the
document entity for each "document", and the two "documents" are document entity for each "document", and the two "documents" are
built up through the accumulation of XML stanzas sent over the two built up through the accumulation of XML stanzas sent over the two
XML streams. However, this perspective is a convenience only, and XML streams. However, this perspective is a convenience only; XMPP
XMPP does not deal in documents but in XML streams and XML stanzas. does not deal in documents but in XML streams and XML stanzas.
In essence, then, an XML stream acts as an envelope for all the XML In essence, then, an XML stream acts as an envelope for all the XML
stanzas sent during a session. We can represent this in a simplistic stanzas sent during a session. We can represent this in a simplistic
fashion as follows: fashion as follows:
|--------------------| |--------------------|
| <stream> | | <stream> |
|--------------------| |--------------------|
| <presence> | | <presence> |
| <show/> | | <show/> |
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|--------------------| |--------------------|
| <iq to='bar'> | | <iq to='bar'> |
| <query/> | | <query/> |
| </iq> | | </iq> |
|--------------------| |--------------------|
| ... | | ... |
|--------------------| |--------------------|
| </stream> | | </stream> |
|--------------------| |--------------------|
4.2 Binding to TCP 4.2. Binding to TCP
Although there is no necessary coupling of an XML stream to a [TCP] Although there is no necessary coupling of an XML stream to a [TCP]
connection (e.g., two entities could connect to each other via connection (e.g., two entities could connect to each other via
another mechanism such as polling over [HTTP]), this specification another mechanism such as polling over [HTTP]), this specification
defines a binding of XMPP to TCP only. In the context of defines a binding of XMPP to TCP only. In the context of
client-to-server communications, a server MUST allow a client to client-to-server communications, a server MUST allow a client to
share a single TCP connection for XML stanzas sent from client to share a single TCP connection for XML stanzas sent from client to
server and from server to client. In the context of server-to-server server and from server to client. In the context of server-to-server
communications, a server MUST use one TCP connection for XML stanzas communications, a server MUST use one TCP connection for XML stanzas
sent from the server to the peer and another TCP connection sent from the server to the peer and another TCP connection
(initiated by the peer) for stanzas from the peer to the server, for (initiated by the peer) for stanzas from the peer to the server, for
a total of two TCP connections. a total of two TCP connections.
4.3 Stream Security 4.3. Stream Security
When negotiating XML streams in XMPP 1.0, TLS SHOULD be used as When negotiating XML streams in XMPP 1.0, TLS SHOULD be used as
defined under Use of TLS (Section 5) and SASL MUST be used as defined defined under Use of TLS (Section 5) and SASL MUST be used as defined
under Use of SASL (Section 6). The "initial stream" (i.e., the under Use of SASL (Section 6). The "initial stream" (i.e., the
stream from the initiating entity to the receiving entity) and the stream from the initiating entity to the receiving entity) and the
"response stream" (i.e., the stream from the receiving entity to the "response stream" (i.e., the stream from the receiving entity to the
initiating entity) MUST be secured separately, although security in initiating entity) MUST be secured separately, although security in
both directions MAY be established via mechanisms that provide mutual both directions MAY be established via mechanisms that provide mutual
authentication. An entity SHOULD NOT attempt to send XML Stanzas authentication. An entity SHOULD NOT attempt to send XML Stanzas
(Section 9) over the stream before the stream has been authenticated, (Section 9) over the stream before the stream has been authenticated,
but if it does then the other entity MUST NOT accept such stanzas and but if it does, then the other entity MUST NOT accept such stanzas
SHOULD return a <not-authorized/> stream error and then terminate and SHOULD return a <not-authorized/> stream error and then terminate
both the XML stream and the underlying TCP connection; note well that both the XML stream and the underlying TCP connection; note well that
this applies to XML stanzas only (i.e., <message/>, <presence/>, and this applies to XML stanzas only (i.e., <message/>, <presence/>, and
<iq/> elements scoped by the default namespace) and not to XML <iq/> elements scoped by the default namespace) and not to XML
elements used for stream negotiation (e.g., elements used to elements used for stream negotiation (e.g., elements used to
negotiate use of TLS (Section 5) or Use of SASL (Section 6)). negotiate Use of TLS (Section 5) or Use of SASL (Section 6)).
4.4 Stream Attributes 4.4. Stream Attributes
The attributes of the stream element are as follows: The attributes of the stream element are as follows:
o to -- The 'to' attribute SHOULD be used only in the XML stream o to -- The 'to' attribute SHOULD be used only in the XML stream
header from the initiating entity to the receiving entity, and header from the initiating entity to the receiving entity, and
MUST be set to a hostname serviced by the receiving entity. There MUST be set to a hostname serviced by the receiving entity. There
SHOULD NOT be a 'to' attribute set in the XML stream header by SHOULD NOT be a 'to' attribute set in the XML stream header by
which the receiving entity replies to the initiating entity; which the receiving entity replies to the initiating entity;
however, if a 'to' attribute is included, it SHOULD be silently however, if a 'to' attribute is included, it SHOULD be silently
ignored by the initiating entity. ignored by the initiating entity.
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entity SHOULD use a configurable default value for both streams, entity SHOULD use a configurable default value for both streams,
which it MUST communicate in the header for the response stream. which it MUST communicate in the header for the response stream.
For all stanzas sent over the initial stream, if the initiating For all stanzas sent over the initial stream, if the initiating
entity does not include an 'xml:lang' attribute, the receiving entity does not include an 'xml:lang' attribute, the receiving
entity SHOULD apply the default value; if the initiating entity entity SHOULD apply the default value; if the initiating entity
does include an 'xml:lang' attribute, the receiving entity MUST does include an 'xml:lang' attribute, the receiving entity MUST
NOT modify or delete it (see also xml:lang (Section 9.1.5)). The NOT modify or delete it (see also xml:lang (Section 9.1.5)). The
value of the 'xml:lang' attribute MUST be an NMTOKEN (as defined value of the 'xml:lang' attribute MUST be an NMTOKEN (as defined
in Section 2.3 of [XML]) and MUST conform to the format defined in in Section 2.3 of [XML]) and MUST conform to the format defined in
RFC 3066 [LANGTAGS]. RFC 3066 [LANGTAGS].
o version -- The presence of the version attribute set to a value of o version -- The presence of the version attribute set to a value of
at least "1.0" signals support for the stream-related protocols at least "1.0" signals support for the stream-related protocols
(including stream features) defined in this specification. (including stream features) defined in this specification.
Detailed rules regarding generation and handling of this attribute Detailed rules regarding the generation and handling of this
are defined below. attribute are defined below.
We can summarize as follows: We can summarize as follows:
| initiating to receiving | receiving to initiating | initiating to receiving | receiving to initiating
---------+---------------------------+----------------------- ---------+---------------------------+-----------------------
to | hostname of receiver | silently ignored to | hostname of receiver | silently ignored
from | silently ignored | hostname of receiver from | silently ignored | hostname of receiver
id | silently ignored | session key id | silently ignored | session key
xml:lang | default language | default language xml:lang | default language | default language
version | signals XMPP 1.0 support | signals XMPP 1.0 support version | signals XMPP 1.0 support | signals XMPP 1.0 support
4.4.1 Version Support 4.4.1. Version Support
The version of XMPP specified herein is "1.0"; in particular, this The version of XMPP specified herein is "1.0"; in particular, this
encapsulates the stream-related protocols (Use of TLS (Section 5), encapsulates the stream-related protocols (Use of TLS (Section 5),
Use of SASL (Section 6), and Stream Errors (Section 4.7)) as well as Use of SASL (Section 6), and Stream Errors (Section 4.7)), as well as
the semantics of the three defined XML stanza types (<message/>, the semantics of the three defined XML stanza types (<message/>,
<presence/>, and <iq/>). The numbering scheme for XMPP versions is <presence/>, and <iq/>). The numbering scheme for XMPP versions is
"<major>.<minor>". The major and minor numbers MUST be treated as "<major>.<minor>". The major and minor numbers MUST be treated as
separate integers and each number MAY be incremented higher than a separate integers and each number MAY be incremented higher than a
single digit. Thus, "XMPP 2.4" would be a lower version than "XMPP single digit. Thus, "XMPP 2.4" would be a lower version than "XMPP
2.13", which in turn would be lower than "XMPP 12.3". Leading zeros 2.13", which in turn would be lower than "XMPP 12.3". Leading zeros
(e.g., "XMPP 6.01") MUST be ignored by recipients and MUST NOT be (e.g., "XMPP 6.01") MUST be ignored by recipients and MUST NOT be
sent. sent.
The major version number should be incremented only if the stream and The major version number should be incremented only if the stream and
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specification. The minor version number indicates new capabilities, specification. The minor version number indicates new capabilities,
and MUST be ignored by an entity with a smaller minor version number, and MUST be ignored by an entity with a smaller minor version number,
but used for informational purposes by the entity with the larger but used for informational purposes by the entity with the larger
minor version number. For example, a minor version number might minor version number. For example, a minor version number might
indicate the ability to process a newly defined value of the 'type' indicate the ability to process a newly defined value of the 'type'
attribute for message, presence, or IQ stanzas; the entity with the attribute for message, presence, or IQ stanzas; the entity with the
larger minor version number would simply note that its correspondent larger minor version number would simply note that its correspondent
would not be able to understand that value of the 'type' attribute would not be able to understand that value of the 'type' attribute
and therefore would not send it. and therefore would not send it.
The following rules apply to the generation and handling by The following rules apply to the generation and handling of the
implementations of the 'version' attribute within stream headers: 'version' attribute within stream headers by implementations:
1. The initiating entity MUST set the value of the 'version' 1. The initiating entity MUST set the value of the 'version'
attribute on the initial stream header to the highest version attribute on the initial stream header to the highest version
number it supports (e.g., if the highest version number it number it supports (e.g., if the highest version number it
supports is that defined in this specification, it MUST set the supports is that defined in this specification, it MUST set the
value to "1.0"). value to "1.0").
2. The receiving entity MUST set the value of the 'version' 2. The receiving entity MUST set the value of the 'version'
attribute on the response stream header to either the value attribute on the response stream header to either the value
supplied by the initiating entity or the highest version number supplied by the initiating entity or the highest version number
supported by the receiving entity, whichever is lower. The supported by the receiving entity, whichever is lower. The
receiving entity MUST perform a numeric comparison on the major receiving entity MUST perform a numeric comparison on the major
and minor version numbers, not a string match on and minor version numbers, not a string match on
"<major>.<minor>". "<major>.<minor>".
3. If the version number included in the response stream header is 3. If the version number included in the response stream header is
at least one major version lower than the version number included at least one major version lower than the version number included
in the initial stream header and newer version entities cannot in the initial stream header and newer version entities cannot
interoperate with older version entities as described above, the interoperate with older version entities as described above, the
initiating entity SHOULD generate an <unsupported-version/> initiating entity SHOULD generate an <unsupported-version/>
stream error and terminate the XML stream and underlying TCP stream error and terminate the XML stream and underlying TCP
connection. connection.
4. If either entity receives a stream header with no 'version' 4. If either entity receives a stream header with no 'version'
attribute, the entity MUST consider the version supported by the attribute, the entity MUST consider the version supported by the
other entity to be "0.0" and SHOULD NOT include a 'version' other entity to be "0.0" and SHOULD NOT include a 'version'
attribute in the stream header it sends in reply. attribute in the stream header it sends in reply.
4.5 Namespace Declarations 4.5. Namespace Declarations
The stream element MUST possess both a streams namespace declaration The stream element MUST possess both a streams namespace declaration
and a default namespace declaration (as "namespace declaration" is and a default namespace declaration (as "namespace declaration" is
defined in the XML namespaces specification [XML-NAMES]). For defined in the XML namespaces specification [XML-NAMES]). For
detailed information regarding the streams namespace and default detailed information regarding the streams namespace and default
namespace, see Namespace Names and Prefixes (Section 11.2). namespace, see Namespace Names and Prefixes (Section 11.2).
4.6 Stream Features 4.6. Stream Features
If the initiating entity includes the 'version' attribute set to a If the initiating entity includes the 'version' attribute set to a
value of at least "1.0" in the initial stream header, the receiving value of at least "1.0" in the initial stream header, the receiving
entity MUST send a <features/> child element (prefixed by the streams entity MUST send a <features/> child element (prefixed by the streams
namespace prefix) to the initiating entity in order to announce any namespace prefix) to the initiating entity in order to announce any
stream-level features that can be negotiated (or capabilities that stream-level features that can be negotiated (or capabilities that
otherwise need to be advertised). Currently this is used only to otherwise need to be advertised). Currently, this is used only to
advertise Use of TLS (Section 5), Use of SASL (Section 6), and advertise Use of TLS (Section 5), Use of SASL (Section 6), and
Resource Binding (Section 7) as defined herein, and for Session Resource Binding (Section 7) as defined herein, and for Session
Establishment as defined in [XMPP-IM]; however, the stream features Establishment as defined in [XMPP-IM]; however, the stream features
functionality could be used to advertise other negotiable features in functionality could be used to advertise other negotiable features in
the future. If an entity does not understand or support some the future. If an entity does not understand or support some
features, it SHOULD silently ignore them. If one or more security features, it SHOULD silently ignore them. If one or more security
features (e.g., TLS and SASL) need to be successfully negotiated features (e.g., TLS and SASL) need to be successfully negotiated
before a non-security-related feature (e.g., Resource Binding) can be before a non-security-related feature (e.g., Resource Binding) can be
offered, the non-security-related feature SHOULD NOT be included in offered, the non-security-related feature SHOULD NOT be included in
the stream features that are advertised before the relevant security the stream features that are advertised before the relevant security
features have been negotiated. features have been negotiated.
4.7 Stream Errors 4.7. Stream Errors
The root stream element MAY contain an <error/> child element that is The root stream element MAY contain an <error/> child element that is
prefixed by the streams namespace prefix. The error child MUST be prefixed by the streams namespace prefix. The error child MUST be
sent by a compliant entity (usually a server rather than a client) if sent by a compliant entity (usually a server rather than a client) if
it perceives that a stream-level error has occurred. it perceives that a stream-level error has occurred.
4.7.1 Rules 4.7.1. Rules
The following rules apply to stream-level errors: The following rules apply to stream-level errors:
o It is assumed that all stream-level errors are unrecoverable; o It is assumed that all stream-level errors are unrecoverable;
therefore, if an error occurs at the level of the stream, the therefore, if an error occurs at the level of the stream, the
entity that detects the error MUST send a stream error to the entity that detects the error MUST send a stream error to the
other entity, send a closing </stream> tag, and terminate the other entity, send a closing </stream> tag, and terminate the
underlying TCP connection. underlying TCP connection.
o If the error occurs while the stream is being set up, the o If the error occurs while the stream is being set up, the
receiving entity MUST still send the opening <stream> tag, include receiving entity MUST still send the opening <stream> tag, include
the <error/> element as a child of the stream element, send the the <error/> element as a child of the stream element, send the
closing </stream> tag, and terminate the underlying TCP closing </stream> tag, and terminate the underlying TCP
connection. In this case, if the initiating entity provides an connection. In this case, if the initiating entity provides an
unknown host in the 'to' attribute (or provides no 'to' attribute unknown host in the 'to' attribute (or provides no 'to' attribute
at all), the server SHOULD provide the server's authoritative at all), the server SHOULD provide the server's authoritative
hostname in the 'from' attribute of the stream header sent before hostname in the 'from' attribute of the stream header sent before
termination. termination.
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o If the error occurs while the stream is being set up, the o If the error occurs while the stream is being set up, the
receiving entity MUST still send the opening <stream> tag, include receiving entity MUST still send the opening <stream> tag, include
the <error/> element as a child of the stream element, send the the <error/> element as a child of the stream element, send the
closing </stream> tag, and terminate the underlying TCP closing </stream> tag, and terminate the underlying TCP
connection. In this case, if the initiating entity provides an connection. In this case, if the initiating entity provides an
unknown host in the 'to' attribute (or provides no 'to' attribute unknown host in the 'to' attribute (or provides no 'to' attribute
at all), the server SHOULD provide the server's authoritative at all), the server SHOULD provide the server's authoritative
hostname in the 'from' attribute of the stream header sent before hostname in the 'from' attribute of the stream header sent before
termination. termination.
4.7.2 Syntax 4.7.2. Syntax
The syntax for stream errors is as follows: The syntax for stream errors is as follows:
<stream:error> <stream:error>
<defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-streams'/> <defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
<text xmlns='urn:ietf:params:xml:ns:xmpp-streams' <text xmlns='urn:ietf:params:xml:ns:xmpp-streams'
xml:lang='langcode'> xml:lang='langcode'>
OPTIONAL descriptive text OPTIONAL descriptive text
</text> </text>
[OPTIONAL application-specific condition element] [OPTIONAL application-specific condition element]
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that namespace that namespace
The <text/> element is OPTIONAL. If included, it SHOULD be used only The <text/> element is OPTIONAL. If included, it SHOULD be used only
to provide descriptive or diagnostic information that supplements the to provide descriptive or diagnostic information that supplements the
meaning of a defined condition or application-specific condition. It meaning of a defined condition or application-specific condition. It
SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be interpreted programmatically by an application. It
SHOULD NOT be used as the error message presented to a user, but MAY SHOULD NOT be used as the error message presented to a user, but MAY
be shown in addition to the error message associated with the be shown in addition to the error message associated with the
included condition element (or elements). included condition element (or elements).
4.7.3 Defined Conditions 4.7.3. Defined Conditions
The following stream-level error conditions are defined: The following stream-level error conditions are defined:
o <bad-format/> -- the entity has sent XML that cannot be processed; o <bad-format/> -- the entity has sent XML that cannot be processed;
this error MAY be used rather than more specific XML-related this error MAY be used instead of the more specific XML-related
errors such as <bad-namespace-prefix/>, <invalid-xml/>, errors, such as <bad-namespace-prefix/>, <invalid-xml/>,
<restricted-xml/>, <unsupported-encoding/>, and <restricted-xml/>, <unsupported-encoding/>, and
<xml-not-well-formed/>, although the more specific errors are <xml-not-well-formed/>, although the more specific errors are
preferred. preferred.
o <bad-namespace-prefix/> -- the entity has sent a namespace prefix o <bad-namespace-prefix/> -- the entity has sent a namespace prefix
that is unsupported, or has sent no namespace prefix on an element that is unsupported, or has sent no namespace prefix on an element
that requires such a prefix (see XML Namespace Names and Prefixes that requires such a prefix (see XML Namespace Names and Prefixes
(Section 11.2)). (Section 11.2)).
o <conflict/> -- the server is closing the active stream for this o <conflict/> -- the server is closing the active stream for this
entity because a new stream has been initiated that conflicts with entity because a new stream has been initiated that conflicts with
the existing stream. the existing stream.
o <connection-timeout/> -- the entity has not generated any traffic o <connection-timeout/> -- the entity has not generated any traffic
over the stream for some period of time (configurable according to over the stream for some period of time (configurable according to
a local service policy). a local service policy).
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. that is no longer hosted by the server.
o <host-unknown/> -- the value of the 'to' attribute provided by the o <host-unknown/> -- the value of the 'to' attribute provided by the
initiating entity in the stream header does not correspond to a initiating entity in the stream header does not correspond to a
hostname that is hosted by the server. hostname that is hosted by the server.
o <improper-addressing/> -- a stanza sent between two servers lacks o <improper-addressing/> -- a stanza sent between two servers lacks
a 'to' or 'from' attribute (or the attribute has no value). a 'to' or 'from' attribute (or the attribute has no value).
o <internal-server-error/> -- the server has experienced a o <internal-server-error/> -- the server has experienced a
misconfiguration or an otherwise-undefined internal error that misconfiguration or an otherwise-undefined internal error that
prevents it from servicing the stream. prevents it from servicing the stream.
o <invalid-from/> -- the JID or hostname provided in a 'from' o <invalid-from/> -- the JID or hostname provided in a 'from'
address does not match an authorized JID or validated domain address does not match an authorized JID or validated domain
negotiated between servers via SASL or dialback, or between a negotiated between servers via SASL or dialback, or between a
client and a server via authentication and resource binding. client and a server via authentication and resource binding.
o <invalid-id/> -- the stream ID or dialback ID is invalid or does o <invalid-id/> -- the stream ID or dialback ID is invalid or does
not match an ID previously provided. not match an ID previously provided.
o <invalid-namespace/> -- the streams namespace name is something o <invalid-namespace/> -- the streams namespace name is something
other than "http://etherx.jabber.org/streams" or the dialback other than "http://etherx.jabber.org/streams" or the dialback
namespace name is something other than "jabber:server:dialback" namespace name is something other than "jabber:server:dialback"
(see XML Namespace Names and Prefixes (Section 11.2)). (see XML Namespace Names and Prefixes (Section 11.2)).
o <invalid-xml/> -- the entity has sent invalid XML over the stream o <invalid-xml/> -- the entity has sent invalid XML over the stream
to a server that performs validation (see Validation (Section to a server that performs validation (see Validation (Section
11.3)). 11.3)).
o <not-authorized/> -- the entity has attempted to send data before o <not-authorized/> -- the entity has attempted to send data before
the stream has been authenticated, or otherwise is not authorized the stream has been authenticated, or otherwise is not authorized
to perform an action related to stream negotiation; the receiving to perform an action related to stream negotiation; the receiving
entity MUST NOT process the offending stanza before sending the entity MUST NOT process the offending stanza before sending the
stream error. stream error.
o <policy-violation/> -- the entity has violated some local service o <policy-violation/> -- the entity has violated some local service
policy; the server MAY choose to specify the policy in the <text/> policy; the server MAY choose to specify the policy in the <text/>
element or an application-specific condition element. element or an application-specific condition element.
o <remote-connection-failed/> -- the server is unable to properly o <remote-connection-failed/> -- the server is unable to properly
connect to a remote entity that is required for authentication or connect to a remote entity that is required for authentication or
authorization. authorization.
o <resource-constraint/> -- the server lacks the system resources o <resource-constraint/> -- the server lacks the system resources
necessary to service the stream. necessary to service the stream.
o <restricted-xml/> -- the entity has attempted to send restricted o <restricted-xml/> -- the entity has attempted to send restricted
XML features such as a comment, processing instruction, DTD, XML features such as a comment, processing instruction, DTD,
entity reference, or unescaped character (see Restrictions entity reference, or unescaped character (see Restrictions
(Section 11.1)). (Section 11.1)).
o <see-other-host/> -- the server will not provide service to the o <see-other-host/> -- the server will not provide service to the
initiating entity but is redirecting traffic to another host; the initiating entity but is redirecting traffic to another host; the
server SHOULD specify the alternate hostname or IP address (which server SHOULD specify the alternate hostname or IP address (which
MUST be a valid domain identifier) as the XML character data of MUST be a valid domain identifier) as the XML character data of
the <see-other-host/> element. the <see-other-host/> element.
o <system-shutdown/> -- the server is being shut down and all active o <system-shutdown/> -- the server is being shut down and all active
streams are being closed. streams are being closed.
o <undefined-condition/> -- the error condition is not one of those o <undefined-condition/> -- the error condition is not one of those
defined by the other conditions in this list; this error condition defined by the other conditions in this list; this error condition
SHOULD be used only in conjunction with an application-specific SHOULD be used only in conjunction with an application-specific
condition. condition.
o <unsupported-encoding/> -- the initiating entity has encoded the o <unsupported-encoding/> -- the initiating entity has encoded the
stream in an encoding that is not supported by the server (see stream in an encoding that is not supported by the server (see
Character Encoding (Section 11.5)). Character Encoding (Section 11.5)).
o <unsupported-stanza-type/> -- the initiating entity has sent a o <unsupported-stanza-type/> -- the initiating entity has sent a
first-level child of the stream that is not supported by the first-level child of the stream that is not supported by the
server. server.
o <unsupported-version/> -- the value of the 'version' attribute o <unsupported-version/> -- the value of the 'version' attribute
provided by the initiating entity in the stream header specifies a provided by the initiating entity in the stream header specifies a
version of XMPP that is not supported by the server; the server version of XMPP that is not supported by the server; the server
MAY specify the version(s) it supports in the <text/> element. MAY specify the version(s) it supports in the <text/> element.
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 [XML]. is not well-formed as defined by [XML].
4.7.4 Application-Specific Conditions 4.7.4. Application-Specific Conditions
As noted, an application MAY provide application-specific stream As noted, an application MAY provide application-specific stream
error information by including a properly-namespaced child in the error information by including a properly-namespaced child in the
error element. The application-specific element SHOULD supplement or error element. The application-specific element SHOULD supplement or
further qualify a defined element. Thus the <error/> element will further qualify a defined element. Thus the <error/> element will
contain two or three child elements: contain two or three child elements:
<stream:error> <stream:error>
<xml-not-well-formed <xml-not-well-formed
xmlns='urn:ietf:params:xml:ns:xmpp-streams'/> xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
<text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-streams'> <text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-streams'>
Some special application diagnostic information! Some special application diagnostic information!
</text> </text>
<escape-your-data xmlns='application-ns'/> <escape-your-data xmlns='application-ns'/>
</stream:error> </stream:error>
</stream:stream> </stream:stream>
4.8 Simplified Stream Examples 4.8. Simplified Stream Examples
This section contains two simplified examples of a stream-based This section contains two simplified examples of a stream-based
"session" of a client on a server (where the "C" lines are sent from "session" of a client on a server (where the "C" lines are sent from
the client to the server, and the "S" lines are sent from the server the client to the server, and the "S" lines are sent from the server
to the client); these examples are included for the purpose of to the client); these examples are included for the purpose of
illustrating the concepts introduced thus far. illustrating the concepts introduced thus far.
A basic "session": A basic "session":
C: <?xml version='1.0'?> C: <?xml version='1.0'?>
skipping to change at page 19, line 31 skipping to change at page 19, line 31
<body>Bad XML, no closing body tag! <body>Bad XML, no closing body tag!
</message> </message>
S: <stream:error> S: <stream:error>
<xml-not-well-formed <xml-not-well-formed
xmlns='urn:ietf:params:xml:ns:xmpp-streams'/> xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
</stream:error> </stream:error>
S: </stream:stream> S: </stream:stream>
5. Use of TLS 5. Use of TLS
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) protocol [TLS], along with a Transport Layer Security (TLS) protocol [TLS], along with a
"STARTTLS" extension that is modelled after similar extensions for "STARTTLS" extension that is modelled after similar extensions for
the IMAP [IMAP], POP3 [POP3], and ACAP [ACAP] protocols as described the IMAP [IMAP], POP3 [POP3], and ACAP [ACAP] protocols as described
in RFC 2595 [USINGTLS]. The namespace name for the STARTTLS in RFC 2595 [USINGTLS]. The namespace name for the STARTTLS
extension is 'urn:ietf:params:xml:ns:xmpp-tls'. extension is 'urn:ietf:params:xml:ns:xmpp-tls'.
An administrator of a given domain MAY require the use of TLS for An administrator of a given domain MAY require the use of TLS for
client-to-server communications, server-to-server communications, or client-to-server communications, server-to-server communications, or
both. Clients SHOULD use TLS to secure the streams prior to both. Clients SHOULD use TLS to secure the streams prior to
attempting to complete SASL negotiation (Section 6), and servers attempting the completion of SASL negotiation (Section 6), and
SHOULD use TLS between two domains for the purpose of securing servers SHOULD use TLS between two domains for the purpose of
server-to-server communications. securing server-to-server communications.
The following rules apply: The following rules apply:
1. An initiating entity that complies with this specification MUST 1. An initiating entity that complies with this specification MUST
include the 'version' attribute set to a value of "1.0" in the include the 'version' attribute set to a value of "1.0" in the
initial stream header. initial stream header.
2. If the TLS negotiation occurs between two servers,
communications MUST NOT proceed until the Domain Name System 2. If the TLS negotiation occurs between two servers, communications
(DNS) hostnames asserted by the servers have been resolved (see MUST NOT proceed until the Domain Name System (DNS) hostnames
Server-to-Server Communications (Section 14.4)). asserted by the servers have been resolved (see Server-to-Server
Communications (Section 14.4)).
3. When a receiving entity that complies with this specification 3. When a receiving entity that complies with this specification
receives an initial stream header that includes the 'version' receives an initial stream header that includes the 'version'
attribute set to a value of at least "1.0", after sending a attribute set to a value of at least "1.0", after sending a
stream header in reply (including the version flag) it MUST stream header in reply (including the version flag), it MUST
include a <starttls/> element (qualified by the include a <starttls/> element (qualified by the
'urn:ietf:params:xml:ns:xmpp-tls' namespace) along with the list 'urn:ietf:params:xml:ns:xmpp-tls' namespace) along with the list
of other stream features it supports. of other stream features it supports.
4. If the initiating entity chooses to use TLS, TLS negotiation
MUST be completed before proceeding to SASL negotiation; this 4. If the initiating entity chooses to use TLS, TLS negotiation MUST
order of negotiation is required in order to help safeguard be completed before proceeding to SASL negotiation; this order of
authentication information sent during SASL negotiation, as well negotiation is required to help safeguard authentication
as to make it possible to base the use of the SASL EXTERNAL information sent during SASL negotiation, as well as to make it
mechanism on a certificate provided during prior TLS possible to base the use of the SASL EXTERNAL mechanism on a
negotiation. certificate provided during prior TLS negotiation.
5. During TLS negotiation, an entity MUST NOT send any white space 5. During TLS negotiation, an entity MUST NOT send any white space
characters (matching production [3] content of [XML]) within the characters (matching production [3] content of [XML]) within the
root stream element as separators between elements (any white root stream element as separators between elements (any white
space characters shown in the TLS examples below are included space characters shown in the TLS examples below are included for
for the sake of readability only); this prohibition helps to the sake of readability only); this prohibition helps to ensure
ensure proper security layer byte precision. proper security layer byte precision.
6. The receiving entity MUST consider the TLS negotiation to have 6. The receiving entity MUST consider the TLS negotiation to have
begun immediately after sending the closing ">" character of the begun immediately after sending the closing ">" character of the
<proceed/> element. The initiating entity MUST consider the TLS <proceed/> element. The initiating entity MUST consider the TLS
negotiation to have begun immediately after receiving the negotiation to have begun immediately after receiving the closing
closing ">" character of the <proceed/> element from the ">" character of the <proceed/> element from the receiving
receiving entity. entity.
7. The initiating entity MUST validate the certificate presented by 7. The initiating entity MUST validate the certificate presented by
the receiving entity; see Certificate Validation (Section 14.2) the receiving entity; see Certificate Validation (Section 14.2)
regarding certificate validation procedures. regarding certificate validation procedures.
8. Certificates MUST be checked against the hostname as provided by 8. Certificates MUST be checked against the hostname as provided by
the initiating entity (e.g., a user), not the hostname as the initiating entity (e.g., a user), not the hostname as
resolved via the Domain Name System; e.g., if the user specifies resolved via the Domain Name System; e.g., if the user specifies
a hostname of "example.com" but a DNS SRV [SRV] lookup returned a hostname of "example.com" but a DNS SRV [SRV] lookup returned
"im.example.com", the certificate MUST be checked as "im.example.com", the certificate MUST be checked as
"example.com". If a JID for any kind of XMPP entity (e.g., "example.com". If a JID for any kind of XMPP entity (e.g.,
client or server) is represented in a certificate, it SHOULD be client or server) is represented in a certificate, it MUST be
encoded as a GeneralName entry of type otherName inside the represented as a UTF8String within an otherName entity inside the
subjectAltName, along with a type-id whose value is "xmpp" (as subjectAltName, using the [ASN.1] Object Identifier
these terms are profiled in [X509]). "id-on-xmppAddr" specified in Section 5.1.1 of this document.
9. If the TLS negotiation is successful, the receiving entity MUST 9. If the TLS negotiation is successful, the receiving entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
initiating entity before TLS takes effect. initiating entity before TLS takes effect.
10. If the TLS negotiation is successful, the initiating entity MUST 10. If the TLS negotiation is successful, the initiating entity MUST
discard any knowledge obtained in an insecure manner from the discard any knowledge obtained in an insecure manner from the
receiving entity before TLS takes effect. receiving entity before TLS takes effect.
11. If the TLS negotiation is successful, the receiving entity MUST 11. 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.
12. If the TLS negotiation is successful, the initiating entity MUST 12. If the TLS negotiation is successful, the initiating entity MUST
continue with SASL negotiation. continue with SASL negotiation.
13. If the TLS negotiation results in failure, the receiving entity 13. If the TLS negotiation results in failure, the receiving entity
MUST terminate both the XML stream and the underlying TCP MUST terminate both the XML stream and the underlying TCP
connection. connection.
14. See Mandatory-to-Implement Technologies (Section 14.7) regarding 14. See Mandatory-to-Implement Technologies (Section 14.7) regarding
mechanisms that MUST be supported. mechanisms that MUST be supported.
5.2 Narrative 5.1.1. ASN.1 Object Identifier for XMPP Address
The [ASN.1] Object Identifier "id-on-xmppAddr" described above is
defined as follows:
id-pkix OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
dod(6) internet(1) security(5) mechanisms(5) pkix(7) }
id-on OBJECT IDENTIFIER ::= { id-pkix 8 } -- other name forms
id-on-xmppAddr OBJECT IDENTIFIER ::= { id-on 5 }
XmppAddr ::= UTF8String
This Object Identifier MAY also be represented in the dotted display
format as "1.3.6.1.5.5.7.8.5".
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
using TLS, the steps involved are as follows: using TLS, the steps involved are as follows:
1. The initiating entity opens a TCP connection and initiates the 1. The initiating entity opens a TCP connection and initiates the
stream by sending the opening XML stream header to the receiving stream by sending the opening XML stream header to the receiving
entity, including the 'version' attribute set to a value of at entity, including the 'version' attribute set to a value of at
least "1.0". least "1.0".
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 the initiating entity, including sending an XML stream header to the initiating entity, including
the 'version' attribute set to a value of at least "1.0". the 'version' attribute set to a value of at least "1.0".
3. The receiving entity offers the STARTTLS extension to the 3. The receiving entity offers the STARTTLS extension to the
initiating entity by including it with the list of other initiating entity by including it with the list of other
supported stream features (if TLS is required for interaction supported stream features (if TLS is required for interaction
with the receiving entity, it SHOULD signal that fact by with the receiving entity, it SHOULD signal that fact by
including a <required/> element as a child of the <starttls/> including a <required/> element as a child of the <starttls/>
element). element).
4. The initiating entity issues the STARTTLS command (i.e., a 4. The initiating entity issues the STARTTLS command (i.e., a
<starttls/> element qualified by the <starttls/> element qualified by the
'urn:ietf:params:xml:ns:xmpp-tls' namespace) to instruct the 'urn:ietf:params:xml:ns:xmpp-tls' namespace) to instruct the
receiving entity that it wishes to begin a TLS negotiation to 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 a <proceed/> element 5. The receiving entity MUST reply with either a <proceed/> element
or a <failure/> element qualified by the or a <failure/> element qualified by the
'urn:ietf:params:xml:ns:xmpp-tls' namespace. If the failure case 'urn:ietf:params:xml:ns:xmpp-tls' namespace. If the failure case
occurs, the receiving entity MUST terminate both the XML stream occurs, the receiving entity MUST terminate both the XML stream
and the underlying TCP connection. If the proceed case occurs, and the underlying TCP connection. If the proceed case occurs,
the entities MUST attempt to complete the TLS negotiation over the entities MUST attempt to complete the TLS negotiation over
the TCP connection and MUST NOT send any further XML data until the TCP connection and MUST NOT send any further XML data until
the TLS negotiation is complete. the TLS negotiation is complete.
6. The initiating entity and receiving entity attempt to complete a 6. The initiating entity and receiving entity attempt to complete a
skipping to change at page 22, line 7 skipping to change at page 22, line 43
or a <failure/> element qualified by the or a <failure/> element qualified by the
'urn:ietf:params:xml:ns:xmpp-tls' namespace. If the failure case 'urn:ietf:params:xml:ns:xmpp-tls' namespace. If the failure case
occurs, the receiving entity MUST terminate both the XML stream occurs, the receiving entity MUST terminate both the XML stream
and the underlying TCP connection. If the proceed case occurs, and the underlying TCP connection. If the proceed case occurs,
the entities MUST attempt to complete the TLS negotiation over the entities MUST attempt to complete the TLS negotiation over
the TCP connection and MUST NOT send any further XML data until the TCP connection and MUST NOT send any further XML data until
the TLS negotiation is complete. the TLS negotiation is complete.
6. The initiating entity and receiving entity attempt to complete a 6. The initiating entity and receiving entity attempt to complete a
TLS negotiation in accordance with [TLS]. TLS negotiation in accordance with [TLS].
7. If the TLS negotiation is unsuccessful, the receiving entity MUST 7. If the TLS negotiation is unsuccessful, the receiving entity MUST
terminate the TCP connection. If the TLS negotiation is terminate the TCP connection. If the TLS negotiation is
successful, the initiating entity MUST initiate a new stream by successful, the initiating entity MUST initiate a new stream by
sending an opening XML stream header to the receiving entity (it sending an opening XML stream header to the receiving entity (it
is not necessary to send a closing </stream> tag first, since the is not necessary to send a closing </stream> tag first, since the
receiving entity and initiating entity MUST consider the original receiving entity and initiating entity MUST consider the original
stream to be closed upon successful TLS negotiation). stream to be closed upon successful TLS negotiation).
8. Upon receiving the new stream header from the initiating entity, 8. Upon receiving the new stream header from the initiating entity,
the receiving entity MUST respond by sending a new XML stream the receiving entity MUST respond by sending a new XML stream
header to the initiating entity along with the available features header to the initiating entity along with the available features
(but not including the STARTTLS feature). (but not including the STARTTLS feature).
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 (note: the alternate steps shown below are stream using STARTTLS (note: the alternate steps shown below are
provided to illustrate the protocol for failure cases; they are not provided to illustrate the protocol for failure cases; they are not
exhaustive and would not necessarily be triggered by the data sent in exhaustive and would not necessarily be triggered by the data sent in
the example). the example).
Step 1: Client initiates stream to server: Step 1: Client initiates stream to server:
<stream:stream <stream:stream
skipping to change at page 24, line 24 skipping to change at page 25, line 5
<stream:features> <stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'> <mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism> <mechanism>DIGEST-MD5</mechanism>
<mechanism>PLAIN</mechanism> <mechanism>PLAIN</mechanism>
<mechanism>EXTERNAL</mechanism> <mechanism>EXTERNAL</mechanism>
</mechanisms> </mechanisms>
</stream:features> </stream:features>
Step 9: Client continues with SASL negotiation (Section 6). Step 9: Client continues with SASL negotiation (Section 6).
5.4 Server-to-Server Example 5.4. Server-to-Server Example
The following example shows the data flow for two servers securing a The following example shows the data flow for two servers securing a
stream using STARTTLS (note: the alternate steps shown below are stream using STARTTLS (note: the alternate steps shown below are
provided to illustrate the protocol for failure cases; they are not provided to illustrate the protocol for failure cases; they are not
exhaustive and would not necessarily be triggered by the data sent in exhaustive and would not necessarily be triggered by the data sent in
the example). the example).
Step 1: Server1 initiates stream to Server2: Step 1: Server1 initiates stream to Server2:
<stream:stream <stream:stream
skipping to change at page 26, line 26 skipping to change at page 27, line 7
<mechanism>DIGEST-MD5</mechanism> <mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism> <mechanism>KERBEROS_V4</mechanism>
<mechanism>EXTERNAL</mechanism> <mechanism>EXTERNAL</mechanism>
</mechanisms> </mechanisms>
</stream:features> </stream:features>
Step 9: Server1 continues with SASL negotiation (Section 6). Step 9: Server1 continues with SASL negotiation (Section 6).
6. Use of SASL 6. Use of SASL
6.1 Overview 6.1. Overview
XMPP includes a method for authenticating a stream by means of an XMPP includes a method for authenticating a stream by means of an
XMPP-specific profile of the Simple Authentication and Security Layer XMPP-specific profile of the Simple Authentication and Security Layer
(SASL) protocol [SASL]. SASL provides a generalized method for (SASL) protocol [SASL]. SASL provides a generalized method for
adding authentication support to connection-based protocols, and XMPP adding authentication support to connection-based protocols, and XMPP
uses a generic XML namespace profile for SASL that conforms to the uses a generic XML namespace profile for SASL that conforms to the
profiling requirements of [SASL]. profiling requirements of [SASL].
The following rules apply: The following rules apply:
skipping to change at page 26, line 41 skipping to change at page 27, line 22
adding authentication support to connection-based protocols, and XMPP adding authentication support to connection-based protocols, and XMPP
uses a generic XML namespace profile for SASL that conforms to the uses a generic XML namespace profile for SASL that conforms to the
profiling requirements of [SASL]. profiling requirements of [SASL].
The following rules apply: The following rules apply:
1. If the SASL negotiation occurs between two servers, 1. If the SASL negotiation occurs between two servers,
communications MUST NOT proceed until the Domain Name System communications MUST NOT proceed until the Domain Name System
(DNS) hostnames asserted by the servers have been resolved (see (DNS) hostnames asserted by the servers have been resolved (see
Server-to-Server Communications (Section 14.4)). Server-to-Server Communications (Section 14.4)).
2. If the initiating entity is capable of SASL negotiation, it MUST 2. If the initiating entity is capable of SASL negotiation, it MUST
include the 'version' attribute set to a value of at least "1.0" include the 'version' attribute set to a value of at least "1.0"
in the initial stream header. in the initial stream header.
3. If the receiving entity is capable of SASL negotiation, it MUST 3. If the receiving entity is capable of SASL negotiation, it MUST
advertise one or more authentication mechanisms within a advertise one or more authentication mechanisms within a
<mechanisms/> element qualified by the <mechanisms/> element qualified by the
'urn:ietf:params:xml:ns:xmpp-sasl' namespace in reply to the 'urn:ietf:params:xml:ns:xmpp-sasl' namespace in reply to the
opening stream tag received from the initiating entity (if the opening stream tag received from the initiating entity (if the
opening stream tag included the 'version' attribute set to a opening stream tag included the 'version' attribute set to a
value of at least "1.0"). value of at least "1.0").
4. During SASL negotiation, an entity MUST NOT send any white space 4. During SASL negotiation, an entity MUST NOT send any white space
characters (matching production [3] content of [XML]) within the characters (matching production [3] content of [XML]) within the
root stream element as separators between elements (any white root stream element as separators between elements (any white
space characters shown in the SASL examples below are included space characters shown in the SASL examples below are included
for the sake of readability only); this prohibition helps to for the sake of readability only); this prohibition helps to
ensure proper security layer byte precision. ensure proper security layer byte precision.
5. Any XML character data contained within the XML elements used 5. Any XML character data contained within the XML elements used
during SASL negotiation MUST be encoded using base64, where the during SASL negotiation MUST be encoded using base64, where the
encoding adheres to the definition in Section 3 of RFC 3548 encoding adheres to the definition in Section 3 of RFC 3548
[BASE64]. [BASE64].
6. If provision of a "simple username" is supported by the selected 6. If provision of a "simple username" is supported by the selected
SASL mechanism (e.g., this is supported by the DIGEST-MD5 and SASL mechanism (e.g., this is supported by the DIGEST-MD5 and
CRAM-MD5 mechanisms but not by the EXTERNAL and GSSAPI CRAM-MD5 mechanisms but not by the EXTERNAL and GSSAPI
mechanisms), during authentication the initiating entity SHOULD mechanisms), during authentication the initiating entity SHOULD
provide as the simple username its sending domain (IP address or provide as the simple username its sending domain (IP address or
fully qualified domain name as contained in a domain identifier) fully qualified domain name as contained in a domain identifier)
in the case of server-to-server communications or its registered in the case of server-to-server communications or its registered
account name (user or node name as contained in an XMPP node account name (user or node name as contained in an XMPP node
identifer) in the case of client-to-server communications. identifier) in the case of client-to-server communications.
7. If the initiating entity wishes to act on behalf of another 7. If the initiating entity wishes to act on behalf of another
entity and the selected SASL mechanism supports transmission of entity and the selected SASL mechanism supports transmission of
an authorization identity, the initiating entity MUST provide an an authorization identity, the initiating entity MUST provide an
authorization identity during SASL negotiation. If the authorization identity during SASL negotiation. If the
initiating entity does not wish to act on behalf of another initiating entity does not wish to act on behalf of another
entity, it MUST NOT provide an authorization identity. As entity, it MUST NOT provide an authorization identity. As
specified in [SASL], the initiating entity MUST NOT provide an specified in [SASL], the initiating entity MUST NOT provide an
authorization identity unless the authorization identity is authorization identity unless the authorization identity is
different from the default authorization identity derived from different from the default authorization identity derived from
the authentication identity as described in [SASL]. If the authentication identity as described in [SASL]. If provided,
provided, the value of the authorization identity MUST be of the the value of the authorization identity MUST be of the form
form <domain> (i.e., a domain identifier only) for servers and <domain> (i.e., a domain identifier only) for servers and of the
of the form <node@domain> (i.e., node identifier and domain form <node@domain> (i.e., node identifier and domain identifier)
identifier) for clients. for clients.
8. Upon successful SASL negotiation that involves negotiation of a 8. Upon successful SASL negotiation that involves negotiation of a
security layer, the receiving entity MUST discard any knowledge security layer, the receiving entity MUST discard any knowledge
obtained from the initiating entity which was not obtained from obtained from the initiating entity which was not obtained from
the SASL negotiation itself. the SASL negotiation itself.
9. Upon successful SASL negotiation that involves negotiation of a 9. Upon successful SASL negotiation that involves negotiation of a
security layer, the initiating entity MUST discard any knowledge security layer, the initiating entity MUST discard any knowledge
obtained from the receiving entity which was not obtained from obtained from the receiving entity which was not obtained from
the SASL negotiation itself. the SASL negotiation itself.
10. See Mandatory-to-Implement Technologies (Section 14.7) regarding 10. See Mandatory-to-Implement Technologies (Section 14.7) regarding
mechanisms that MUST be supported. mechanisms that MUST be supported.
6.2 Narrative 6.2. Narrative
When an initiating entity authenticates with a receiving entity using When an initiating entity authenticates with a receiving entity using
SASL, the steps involved are as follows: SASL, the steps involved are as follows:
1. The initiating entity requests SASL authentication by including 1. The initiating entity requests SASL authentication by including
the 'version' attribute in the opening XML stream header sent to the 'version' attribute in the opening XML stream header sent to
the receiving entity, with the value set to "1.0". the receiving entity, with the value set to "1.0".
2. After sending an XML stream header in reply, the receiving entity 2. After sending an XML stream header in reply, the receiving entity
advertises a list of available SASL authentication mechanisms; advertises a list of available SASL authentication mechanisms;
each of these is a <mechanism/> element included as a child each of these is a <mechanism/> element included as a child
within a <mechanisms/> container element qualified by the within a <mechanisms/> container element qualified by the
'urn:ietf:params:xml:ns:xmpp-sasl' namespace, which in turn is a 'urn:ietf:params:xml:ns:xmpp-sasl' namespace, which in turn is a
child of a <features/> element in the streams namespace. If Use child of a <features/> element in the streams namespace. If Use
of TLS (Section 5) needs to be established before a particular of TLS (Section 5) needs to be established before a particular
authentication mechanism may be used, the receiving entity MUST authentication mechanism may be used, the receiving entity MUST
NOT provide that mechanism in the list of available SASL NOT provide that mechanism in the list of available SASL
authentication mechanisms prior to TLS negotiation. If the authentication mechanisms prior to TLS negotiation. If the
skipping to change at page 29, line 41 skipping to change at page 30, line 37
stream to be closed upon sending or receiving the <success/> stream to be closed upon sending or receiving the <success/>
element). Upon receiving the new stream header from the element). Upon receiving the new stream header from the
initiating entity, the receiving entity MUST respond by sending a initiating entity, the receiving entity MUST respond by sending a
new XML stream header to the initiating entity, along with any new XML stream header to the initiating entity, along with any
available features (but not including the STARTTLS and SASL available features (but not including the STARTTLS and SASL
features) or an empty <features/> element (to signify that no features) or an empty <features/> element (to signify that no
additional features are available); any such additional features additional features are available); any such additional features
not defined herein MUST be defined by the relevant extension to not defined herein MUST be defined by the relevant extension to
XMPP. XMPP.
6.3 SASL Definition 6.3. SASL Definition
The profiling requirements of [SASL] require that the following The profiling requirements of [SASL] require that the following
information be supplied by a protocol definition: information be supplied by a protocol definition:
service name: "xmpp" service name: "xmpp"
initiation sequence: After the initiating entity provides an opening initiation sequence: After the initiating entity provides an opening
XML stream header and the receiving entity replies in kind, the XML stream header and the receiving entity replies in kind, the
receiving entity provides a list of acceptable authentication receiving entity provides a list of acceptable authentication
methods. The initiating entity chooses one method from the list methods. The initiating entity chooses one method from the list
and sends it to the receiving entity as the value of the and sends it to the receiving entity as the value of the
'mechanism' attribute possessed by an <auth/> element, optionally 'mechanism' attribute possessed by an <auth/> element, optionally
including an initial response to avoid a round trip. including an initial response to avoid a round trip.
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. Upon successful negotiation, both sides <abort/> element. Upon successful negotiation, both sides
consider the original XML stream to be closed and new stream consider the original XML stream to be closed and new stream
headers are sent by both entities. headers are sent by both entities.
security layer negotiation: The security layer takes effect security layer negotiation: The security layer takes effect
immediately after sending the closing ">" character of the immediately after sending the closing ">" character of the
<success/> element for the receiving entity, and immediately after <success/> element for the receiving entity, and immediately after
receiving the closing ">" character of the <success/> element for receiving the closing ">" character of the <success/> element for
the initiating entity. The order of layers is first [TCP], then the initiating entity. The order of layers is first [TCP], then
[TLS], then [SASL], then XMPP. [TLS], then [SASL], then XMPP.
use of the authorization identity: The authorization identity may be use of the authorization identity: The authorization identity may be
used by xmpp to denote the non-default <node@domain> of a client used by xmpp to denote the non-default <node@domain> of a client
or the sending <domain> of a server. or the sending <domain> of a server.
6.4 SASL Errors 6.4. SASL Errors
The following SASL-related error conditions are defined: The following SASL-related error conditions are defined:
o <aborted/> -- The receiving entity acknowledges an <abort/> o <aborted/> -- The receiving entity acknowledges an <abort/>
element sent by the initiating entity; sent in reply to the element sent by the initiating entity; sent in reply to the
<abort/> element. <abort/> element.
o <incorrect-encoding/> -- The data provided by the initiating o <incorrect-encoding/> -- The data provided by the initiating
entity could not be processed because the [BASE64] encoding is entity could not be processed because the [BASE64] encoding is
incorrect (e.g., because the encoding does not adhere to the incorrect (e.g., because the encoding does not adhere to the
definition in Section 3 of [BASE64]); sent in reply to a definition in Section 3 of [BASE64]); sent in reply to a
<response/> element or an <auth/> element with initial response <response/> element or an <auth/> element with initial response
data. data.
o <invalid-authzid/> -- The authzid provided by the initiating o <invalid-authzid/> -- The authzid provided by the initiating
entity is invalid, either because it is incorrectly formatted or entity is invalid, either because it is incorrectly formatted or
because the initiating entity does not have permissions to because the initiating entity does not have permissions to
authorize that ID; sent in reply to a <response/> element or an authorize that ID; sent in reply to a <response/> element or an
<auth/> element with initial response data. <auth/> element with initial response data.
o <invalid-mechanism/> -- The initiating entity did not provide a o <invalid-mechanism/> -- The initiating entity did not provide a
mechanism or requested a mechanism that is not supported by the mechanism or requested a mechanism that is not supported by the
receiving entity; sent in reply to an <auth/> element. receiving entity; sent in reply to an <auth/> element.
o <mechanism-too-weak/> -- The mechanism requested by the initiating o <mechanism-too-weak/> -- The mechanism requested by the initiating
entity is weaker than server policy permits for that initiating entity is weaker than server policy permits for that initiating
entity; sent in reply to a <response/> element or an <auth/> entity; sent in reply to a <response/> element or an <auth/>
element with initial response data. element with initial response data.
o <not-authorized/> -- The authentication failed because the o <not-authorized/> -- The authentication failed because the
initiating entity did not provide valid credentials (this includes initiating entity did not provide valid credentials (this includes
but is not limited to the case of an unknown username); sent in but is not limited to the case of an unknown username); sent in
reply to a <response/> element or an <auth/> element with initial reply to a <response/> element or an <auth/> element with initial
response data. response data.
o <temporary-auth-failure/> -- The authentication failed because of o <temporary-auth-failure/> -- The authentication failed because of
a temporary error condition within the receiving entity; sent in a temporary error condition within the receiving entity; sent in
reply to an <auth/> element or <response/> element. reply to an <auth/> element or <response/> element.
6.5 Client-to-Server Example 6.5. 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, normally after successful TLS negotiation with a server using SASL, normally after successful TLS negotiation
(note: the alternate steps shown below are provided to illustrate the (note: the alternate steps shown below are provided to illustrate the
protocol for failure cases; they are not exhaustive and would not protocol for failure cases; they are not exhaustive and would not
necessarily be triggered by the data sent in the example). necessarily be triggered by the data sent in the example).
Step 1: Client initiates stream to server: Step 1: Client initiates stream to server:
<stream:stream <stream:stream
skipping to change at page 33, line 48 skipping to change at page 35, line 5
xmlns='jabber:client' xmlns='jabber:client'
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
id='c2s_345' id='c2s_345'
from='example.com' from='example.com'
version='1.0'> version='1.0'>
<stream:features> <stream:features>
<bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/> <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/>
<session xmlns='urn:ietf:params:xml:ns:xmpp-session'/> <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
</stream:features> </stream:features>
6.6 Server-to-Server Example 6.6. Server-to-Server Example
The following example shows the data flow for a server authenticating The following example shows the data flow for a server authenticating
with another server using SASL, normally after successful TLS with another server using SASL, normally after successful TLS
negotiation (note: the alternate steps shown below are provided to negotiation (note: the alternate steps shown below are provided to
illustrate the protocol for failure cases; they are not exhaustive illustrate the protocol for failure cases; they are not exhaustive
and would not necessarily be triggered by the data sent in the and would not necessarily be triggered by the data sent in the
example). example).
Step 1: Server1 initiates stream to Server2: Step 1: Server1 initiates stream to Server2:
skipping to change at page 39, line 46 skipping to change at page 41, line 7
</iq> </iq>
If, before completing the resource binding step, the client attempts If, before completing the resource binding step, the client attempts
to send an XML stanza other than an IQ stanza with a <bind/> child to send an XML stanza other than an IQ stanza with a <bind/> child
qualified by the 'urn:ietf:params:xml:ns:xmpp-bind' namespace, the qualified by the 'urn:ietf:params:xml:ns:xmpp-bind' namespace, the
server MUST NOT process the stanza and SHOULD return a server MUST NOT process the stanza and SHOULD return a
<not-authorized/> stanza error to the client. <not-authorized/> stanza error to the client.
8. Server Dialback 8. Server Dialback
8.1 Overview 8.1. Overview
The Jabber protocols from which XMPP was adapted include a "server The Jabber protocols from which XMPP was adapted include a "server
dialback" method for protecting against domain spoofing, thus making dialback" method for protecting against domain spoofing, thus making
it more difficult to spoof XML stanzas. Server dialback is not a it more difficult to spoof XML stanzas. Server dialback is not a
security mechanism, and results in weak verification of server security mechanism, and results in weak verification of server
identities only (see Server-to-Server Communications (Section 14.4) identities only (see Server-to-Server Communications (Section 14.4)
regarding this method's security characteristics). Domains requiring regarding this method's security characteristics). Domains requiring
robust security SHOULD use TLS and SASL; see Server-to-Server robust security SHOULD use TLS and SASL; see Server-to-Server
Communications (Section 14.4) for details. If SASL is used for Communications (Section 14.4) for details. If SASL is used for
server-to-server authentication, dialback SHOULD NOT be used since it server-to-server authentication, dialback SHOULD NOT be used since it
skipping to change at page 40, line 22 skipping to change at page 41, line 32
The server dialback method is made possible by the existence of the The server dialback method is made possible by the existence of the
Domain Name System (DNS), since one server can (normally) discover Domain Name System (DNS), since one server can (normally) discover
the authoritative server for a given domain. Because dialback the authoritative server for a given domain. Because dialback
depends on DNS, inter-domain communications MUST NOT proceed until depends on DNS, inter-domain communications MUST NOT proceed until
the Domain Name System (DNS) hostnames asserted by the servers have the Domain Name System (DNS) hostnames asserted by the servers have
been resolved (see Server-to-Server Communications (Section 14.4)). been resolved (see Server-to-Server Communications (Section 14.4)).
Server dialback is uni-directional, and results in (weak) Server dialback is uni-directional, and results in (weak)
verification of identities for one stream in one direction. Because verification of identities for one stream in one direction. Because
server dialback is not an authentication mechanism, mutual server dialback is not an authentication mechanism, mutual
authentication is not possible via dialback. Therefore server authentication is not possible via dialback. Therefore, server
dialback MUST be completed in each direction in order to enable dialback MUST be completed in each direction in order to enable
bi-directional communications between two domains. bi-directional communications between two domains.
The method for generating and verifying the keys used in server The method for generating and verifying the keys used in server
dialback MUST take into account the hostnames being used, the stream dialback MUST take into account the hostnames being used, the stream
ID generated by the receiving server, and a secret known by the ID generated by the receiving server, and a secret known by the
authoritative server's network. The stream ID is security-critical authoritative server's network. The stream ID is security-critical
in server dialback and therefore MUST be both unpredictable and in server dialback and therefore MUST be both unpredictable and
non-repeating (see [RANDOM] for recommendations regarding randomness non-repeating (see [RANDOM] for recommendations regarding randomness
for security purposes). for security purposes).
skipping to change at page 40, line 43 skipping to change at page 42, line 4
Any error that occurs during dialback negotiation MUST be considered Any error that occurs during dialback negotiation MUST be considered
a stream error, resulting in termination of the stream and of the a stream error, resulting in termination of the stream and of the
underlying TCP connection. The possible error conditions are underlying TCP connection. The possible error conditions are
specified in the protocol description below. specified in the protocol description below.
The following terminology applies: The following terminology applies:
o Originating Server -- the server that is attempting to establish a o Originating Server -- the server that is attempting to establish a
connection between two domains. connection between two domains.
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 domain which it claims to be. the Originating Server represents the domain which it claims to
be.
o Authoritative Server -- the server that answers to the DNS o Authoritative Server -- the server that answers to the DNS
hostname asserted by Originating Server; for basic environments hostname asserted by the Originating Server; for basic
this will be Originating Server, but it could be a separate environments this will be the Originating Server, but it could be
machine in Originating Server's network. a separate machine in the Originating Server's network.
8.2 Order of Events 8.2. Order of Events
The following is a brief summary of the order of events in dialback: The following is a brief summary of the order of events in dialback:
1. Originating Server establishes a connection to Receiving Server. 1. The Originating Server establishes a connection to the Receiving
2. Originating Server sends a 'key' value over the connection to
Receiving Server.
3. Receiving Server establishes a connection to Authoritative
Server.
4. Receiving Server sends the same 'key' value to Authoritative
Server. Server.
5. Authoritative Server replies that key is valid or invalid.
6. Receiving Server informs Originating Server whether it is 2. The Originating Server sends a 'key' value over the connection to
the Receiving Server.
3. The Receiving Server establishes a connection to the
Authoritative Server.
4. The Receiving Server sends the same 'key' value to the
Authoritative Server.
5. The Authoritative Server replies that key is valid or invalid.
6. The Receiving Server informs the Originating Server whether it is
authenticated or not. authenticated or not.
We can represent this flow of events graphically as follows: We can represent this flow of events graphically as follows:
Originating Receiving Originating Receiving
Server Server Server Server
----------- --------- ----------- ---------
| | | |
| establish connection | | establish connection |
| ----------------------> | | ----------------------> |
skipping to change at page 42, line 40 skipping to change at page 43, line 42
| send verify request | | send verify request |
| ----------------------> | | ----------------------> |
| | | |
| send verify response | | send verify response |
| <---------------------- | | <---------------------- |
| |
| report dialback result | | report dialback result |
| <---------------------- | | <---------------------- |
| | | |
8.3 Protocol 8.3. Protocol
The detailed protocol interaction between the servers is as follows: The detailed protocol interaction between the servers is as follows:
1. Originating Server establishes TCP connection to Receiving 1. The Originating Server establishes TCP connection to the
Server. Receiving Server.
2. Originating Server sends a stream header to Receiving Server:
2. The Originating Server sends a stream header to the Receiving
Server:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback'> xmlns:db='jabber:server:dialback'>
Note: The 'to' and 'from' attributes are OPTIONAL on the root Note: The 'to' and 'from' attributes are OPTIONAL on the root stream
stream element. The inclusion of the xmlns:db namespace element. The inclusion of the xmlns:db namespace declaration with
declaration with the name shown indicates to Receiving Server the name shown indicates to the Receiving Server that the Originating
that Originating Server supports dialback. If the namespace Server supports dialback. If the namespace name is incorrect, then
name is incorrect, then Receiving Server MUST generate an the Receiving Server MUST generate an <invalid-namespace/> stream
<invalid-namespace/> stream error condition and terminate both error condition and terminate both the XML stream and the underlying
the XML stream and the underlying TCP connection. TCP connection.
3. Receiving Server SHOULD send a stream header back to Originating
Server, including a unique ID for this interaction: 3. The Receiving Server SHOULD send a stream header back to the
Originating Server, including a unique ID for this interaction:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback' xmlns:db='jabber:server:dialback'
id='457F9224A0...'> id='457F9224A0...'>
Note: The 'to' and 'from' attributes are OPTIONAL on the root Note: The 'to' and 'from' attributes are OPTIONAL on the root stream
stream element. If the namespace name is incorrect, then element. If the namespace name is incorrect, then the Originating
Originating Server MUST generate an <invalid-namespace/> stream Server MUST generate an <invalid-namespace/> stream error condition
error condition and terminate both the XML stream and the and terminate both the XML stream and the underlying TCP connection.
underlying TCP connection. Note well that Receiving Server Note well that the Receiving Server SHOULD reply but MAY silently
SHOULD reply but MAY silently terminate the XML stream and terminate the XML stream and underlying TCP connection depending on
underlying TCP connection depending on security policies in security policies in place; however, if the Receiving Server desires
place; however, if Receiving Server desires to proceed, it MUST to proceed, it MUST send a stream header back to the Originating
send a stream header back to Originating Server. Server.
4. Originating Server sends a dialback key to Receiving Server:
4. The Originating Server sends a dialback key to the Receiving
Server:
<db:result <db:result
to='Receiving Server' to='Receiving Server'
from='Originating Server'> from='Originating Server'>
98AF014EDC0... 98AF014EDC0...
</db:result> </db:result>
Note: This key is not examined by Receiving Server, since Note: This key is not examined by the Receiving Server, since the
Receiving Server does not keep information about Originating Receiving Server does not keep information about the Originating
Server between sessions. The key generated by Originating Server between sessions. The key generated by the Originating Server
Server MUST be based in part on the value of the ID provided by MUST be based in part on the value of the ID provided by the
Receiving Server in the previous step, and in part on a secret Receiving Server in the previous step, and in part on a secret shared
shared by Originating Server and Authoritative Server. If the by the Originating Server and Authoritative Server. If the value of
value of the 'to' address does not match a hostname recognized the 'to' address does not match a hostname recognized by the
by Receiving Server, then Receiving Server MUST generate a Receiving Server, then the Receiving Server MUST generate a
<host-unknown/> stream error condition and terminate both the <host-unknown/> stream error condition and terminate both the XML
XML stream and the underlying TCP connection. If the value of stream and the underlying TCP connection. If the value of the 'from'
the 'from' address matches a domain with which Receiving Server address matches a domain with which the Receiving Server already has
already has an established connection, then Receiving Server an established connection, then the Receiving Server MUST maintain
MUST maintain the existing connection until it validates whether the existing connection until it validates whether the new connection
the new connection is legitimate; additionally, Receiving Server is legitimate; additionally, the Receiving Server MAY choose to
MAY choose to generate a <not-authorized/> stream error generate a <not-authorized/> stream error condition for the new
condition for the new connection and then terminate both the XML connection and then terminate both the XML stream and the underlying
stream and the underlying TCP connection related to the new TCP connection related to the new request.
request.
5. Receiving Server establishes a TCP connection back to the domain 5. The Receiving Server establishes a TCP connection back to the
name asserted by Originating Server, as a result of which it domain name asserted by the Originating Server, as a result of
connects to Authoritative Server. (Note: As an optimization, an which it connects to the Authoritative Server. (Note: As an
implementation MAY reuse an existing connection here.) optimization, an implementation MAY reuse an existing connection
6. Receiving Server sends Authoritative Server a stream header: here.)
6. The Receiving Server sends the Authoritative Server a stream
header:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback'> xmlns:db='jabber:server:dialback'>
Note: The 'to' and 'from' attributes are OPTIONAL on the root Note: The 'to' and 'from' attributes are OPTIONAL on the root stream
stream element. If the namespace name is incorrect, then element. If the namespace name is incorrect, then the Authoritative
Authoritative Server MUST generate an <invalid-namespace/> Server MUST generate an <invalid-namespace/> stream error condition
stream error condition and terminate both the XML stream and the and terminate both the XML stream and the underlying TCP connection.
underlying TCP connection.
7. Authoritative Server sends Receiving Server a stream header: 7. The Authoritative Server sends the Receiving Server a stream
header:
<stream:stream <stream:stream
xmlns:stream='http://etherx.jabber.org/streams' xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server' xmlns='jabber:server'
xmlns:db='jabber:server:dialback' xmlns:db='jabber:server:dialback'
id='1251A342B...'> id='1251A342B...'>
Note: If the namespace name is incorrect, then Receiving Server Note: If the namespace name is incorrect, then the Receiving Server
MUST generate an <invalid-namespace/> stream error condition and MUST generate an <invalid-namespace/> stream error condition and
terminate both the XML stream and the underlying TCP connection terminate both the XML stream and the underlying TCP connection
between it and Authoritative Server. If a stream error occurs between it and the Authoritative Server. If a stream error occurs
between Receiving Server and Authoritative Server, then between the Receiving Server and the Authoritative Server, then the
Receiving Server MUST generate a <remote-connection-failed/> Receiving Server MUST generate a <remote-connection-failed/> stream
stream error condition and terminate both the XML stream and the error condition and terminate both the XML stream and the underlying
underlying TCP connection between it and Originating Server. TCP connection between it and the Originating Server.
8. Receiving Server sends Authoritative Server a request for
8. The Receiving Server sends the Authoritative Server a request for
verification of a key: verification of a key:
<db:verify <db:verify
from='Receiving Server' from='Receiving Server'
to='Originating Server' to='Originating Server'
id='457F9224A0...'> id='457F9224A0...'>
98AF014EDC0... 98AF014EDC0...
</db:verify> </db:verify>
Note: Passed here are the hostnames, the original identifier Note: Passed here are the hostnames, the original identifier from the
from Receiving Server's stream header to Originating Server in Receiving Server's stream header to the Originating Server in Step 3,
Step 3, and the key that Originating Server sent to Receiving and the key that the Originating Server sent to the Receiving Server
Server in Step 4. Based on this information as well as shared in Step 4. Based on this information, as well as shared secret
secret information within the Authoritative Server's network, information within the Authoritative Server's network, the key is
the key is verified. Any verifiable method MAY be used to verified. Any verifiable method MAY be used to generate the key. If
generate the key. If the value of the 'to' address does not the value of the 'to' address does not match a hostname recognized by
match a hostname recognized by Authoritative Server, then the Authoritative Server, then the Authoritative Server MUST generate
Authoritative Server MUST generate a <host-unknown/> stream a <host-unknown/> stream error condition and terminate both the XML
error condition and terminate both the XML stream and the stream and the underlying TCP connection. If the value of the 'from'
underlying TCP connection. If the value of the 'from' address address does not match the hostname represented by the Receiving
does not match the hostname represented by Receiving Server when Server when opening the TCP connection (or any validated domain
opening the TCP connection (or any validated domain thereof, thereof, such as a validated subdomain of the Receiving Server's
such as a validated subdomain of Receiving Server's hostname or hostname or another validated domain hosted by the Receiving Server),
another validated domain hosted by Receiving Server), then then the Authoritative Server MUST generate an <invalid-from/> stream
Authoritative Server MUST generate an <invalid-from/> stream error condition and terminate both the XML stream and the underlying
error condition and terminate both the XML stream and the TCP connection.
underlying TCP connection.
9. Authoritative Server verifies whether the key was valid or 9. The Authoritative Server verifies whether the key was valid or
invalid: invalid:
<db:verify <db:verify
from='Originating Server' from='Originating Server'
to='Receiving Server' to='Receiving Server'
type='valid' type='valid'
id='457F9224A0...'/> id='457F9224A0...'/>
or or
<db:verify <db:verify
from='Originating Server' from='Originating Server'
to='Receiving Server' to='Receiving Server'
type='invalid' type='invalid'
id='457F9224A0...'/> id='457F9224A0...'/>
Note: If the ID does not match that provided by the Receiving Server
Note: If the ID does not match that provided by Receiving Server in Step 3, then the Receiving Server MUST generate an <invalid-id/>
in Step 3, then Receiving Server MUST generate an <invalid-id/>
stream error condition and terminate both the XML stream and the stream error condition and terminate both the XML stream and the
underlying TCP connection. If the value of the 'to' address underlying TCP connection. If the value of the 'to' address does not
does not match a hostname recognized by Receiving Server, then match a hostname recognized by the Receiving Server, then the
Receiving Server MUST generate a <host-unknown/> stream error Receiving Server MUST generate a <host-unknown/> stream error
condition and terminate both the XML stream and the underlying condition and terminate both the XML stream and the underlying TCP
TCP connection. If the value of the 'from' address does not connection. If the value of the 'from' address does not match the
match the hostname represented by Originating Server when hostname represented by the Originating Server when opening the TCP
opening the TCP connection (or any validated domain thereof, connection (or any validated domain thereof, such as a validated
such as a validated subdomain of Originating Server's hostname subdomain of the Originating Server's hostname or another validated
or another validated domain hosted by Originating Server), then domain hosted by the Originating Server), then the Receiving Server
Receiving Server MUST generate an <invalid-from/> stream error MUST generate an <invalid-from/> stream error condition and terminate
condition and terminate both the XML stream and the underlying both the XML stream and the underlying TCP connection. After
TCP connection. After returning the verification to Receiving returning the verification to the Receiving Server, the Authoritative
Server, Authoritative Server SHOULD terminate the stream between Server SHOULD terminate the stream between them.
them.
10. Receiving Server informs Originating Server of the result: 10. The Receiving Server informs the Originating Server of the
result:
<db:result <db:result
from='Receiving Server' from='Receiving Server'
to='Originating Server' to='Originating Server'
type='valid'/> type='valid'/>
Note: At this point the connection has either been validated via Note: At this point, the connection has either been validated via a
a type='valid', or reported as invalid. If the connection is type='valid', or reported as invalid. If the connection is invalid,
invalid, then Receiving Server MUST terminate both the XML then the Receiving Server MUST terminate both the XML stream and the
stream and the underlying TCP connection. If the connection is underlying TCP connection. If the connection is validated, data can
validated, data can be sent by Originating Server and read by be sent by the Originating Server and read by the Receiving Server;
Receiving Server; before that, all XML stanzas sent to Receiving before that, all XML stanzas sent to the Receiving Server SHOULD be
Server SHOULD be silently dropped. silently dropped.
The result of the foregoing is that Receiving Server has verified the The result of the foregoing is that the Receiving Server has verified
identity of Originating Server, so that Originating Server can send, the identity of the Originating Server, so that the Originating
and Receiving Server can accept, XML stanzas over the "initial Server can send, and the Receiving Server can accept, XML stanzas
stream" (i.e., the stream from Originating Server to Receiving over the "initial stream" (i.e., the stream from the Originating
Server). In order to verify the identities of the entities using the Server to the Receiving Server). In order to verify the identities
"response stream" (i.e., the stream from Receiving Server to of the entities using the "response stream" (i.e., the stream from
Originating Server), dialback MUST be completed in the opposite the Receiving Server to the Originating Server), dialback MUST be
direction as well. completed in the opposite direction as well.
After successful dialback negotiation, Receiving Server SHOULD accept After successful dialback negotiation, the Receiving Server SHOULD
subsequent <db:result/> packets (e.g., validation requests sent to a accept subsequent <db:result/> packets (e.g., validation requests
subdomain or other hostname serviced by Receiving Server) from the sent to a subdomain or other hostname serviced by the Receiving
Originating Server over the existing validated connection; this Server) from the Originating Server over the existing validated
enables "piggybacking" of the original validated connection in one connection; this enables "piggybacking" of the original validated
direction. connection in one direction.
Even if dialback negotiation is successful, a server MUST verify that Even if dialback negotiation is successful, a server MUST verify that
all XML stanzas received from the other server include a 'from' all XML stanzas received from the other server include a 'from'
attribute and a 'to' attribute; if a stanza does not meet this attribute and a 'to' attribute; if a stanza does not meet this
restriction, the server that receives the stanza MUST generate an restriction, the server that receives the stanza MUST generate an
<improper-addressing/> stream error condition and terminate both the <improper-addressing/> stream error condition and terminate both the
XML stream and the underlying TCP connection. Furthermore, a server XML stream and the underlying TCP connection. Furthermore, a server
MUST verify that the 'from' attribute of stanzas received from the MUST verify that the 'from' attribute of stanzas received from the
other server includes a validated domain for the stream; if a stanza other server includes a validated domain for the stream; if a stanza
does not meet this restriction, the server that receives the stanza does not meet this restriction, the server that receives the stanza
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(Section 6), and Resource Binding (Section 7) if necessary, XML (Section 6), and Resource Binding (Section 7) if necessary, XML
stanzas can be sent over the streams. Three kinds of XML stanza are stanzas can be sent over the streams. Three kinds of XML stanza are
defined for the 'jabber:client' and 'jabber:server' namespaces: defined for the 'jabber:client' and 'jabber:server' namespaces:
<message/>, <presence/>, and <iq/>. In addition, there are five <message/>, <presence/>, and <iq/>. In addition, there are five
common attributes for these kinds of stanza. These common common attributes for these kinds of stanza. These common
attributes, as well as the basic semantics of the three stanza kinds, attributes, as well as the basic semantics of the three stanza kinds,
are defined herein; more detailed information regarding the syntax of are defined herein; more detailed information regarding the syntax of
XML stanzas in relation to instant messaging and presence XML stanzas in relation to instant messaging and presence
applications is provided in [XMPP-IM]. applications is provided in [XMPP-IM].
9.1 Common Attributes 9.1. Common Attributes
The following five attributes are common to message, presence, and IQ The following five attributes are common to message, presence, and IQ
stanzas: stanzas:
9.1.1 to 9.1.1. 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. the stanza.
In the 'jabber:client' namespace, a stanza SHOULD possess a 'to' In the 'jabber:client' namespace, a stanza SHOULD possess a 'to'
attribute, although a stanza sent from a client to a server for attribute, although a stanza sent from a client to a 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
broadcasting to other entities) SHOULD NOT possess a 'to' attribute. broadcasting to other entities) SHOULD NOT possess a 'to' attribute.
In the 'jabber:server' namespace, a stanza MUST possess a 'to' In the 'jabber:server' namespace, a stanza MUST possess a 'to'
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restriction, it MUST generate an <improper-addressing/> stream error restriction, it MUST generate an <improper-addressing/> stream error
condition and terminate both the XML stream and the underlying TCP condition and terminate both the XML stream and the underlying TCP
connection with the offending server. connection with the offending server.
If the value of the 'to' attribute is invalid or cannot be contacted, If the value of the 'to' attribute is invalid or cannot be contacted,
the entity discovering that fact (usually the sender's or recipient's the entity discovering that fact (usually the sender's or recipient's
server) MUST return an appropriate error to the sender, setting the server) MUST return an appropriate error to the sender, setting the
'from' attribute of the error stanza to the value provided in the 'from' attribute of the error stanza to the value provided in the
'to' attribute of the offending stanza. 'to' attribute of the offending stanza.
9.1.2 from 9.1.2. from
The 'from' attribute specifies the JID of the sender. The 'from' attribute specifies the JID of the sender.
When a server receives an XML stanza within the context of an When a server receives an XML stanza within the context of an
authenticated stream qualified by the 'jabber:client' namespace, it authenticated stream qualified by the 'jabber:client' namespace, it
MUST do one of the following: MUST do one of the following:
1. validate that the value of the 'from' attribute provided by the 1. validate that the value of the 'from' attribute provided by the
client is that of a connected resource for the associated entity client is that of a connected resource for the associated entity
2. add a 'from' address to the stanza whose value is the bare JID 2. add a 'from' address to the stanza whose value is the bare JID
(<node@domain>) or the full JID (<node@domain/resource>) (<node@domain>) or the full JID (<node@domain/resource>)
determined by the server for the connected resource that determined by the server for the connected resource that
generated the stanza (see Determination of Addresses (Section generated the stanza (see Determination of Addresses (Section
3.5)) 3.5))
If a client attempts to send an XML stanza for which the value of the If a client attempts to send an XML stanza for which the value of the
'from' attribute does not match one of the connected resources for 'from' attribute does not match one of the connected resources for
that entity, the server SHOULD return an <invalid-from/> stream error that entity, the server SHOULD return an <invalid-from/> stream error
to the client. If a client attempts to send an XML stanza over a to the client. If a client attempts to send an XML stanza over a
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determined by the server for the connected resource that determined by the server for the connected resource that
generated the stanza (see Determination of Addresses (Section generated the stanza (see Determination of Addresses (Section
3.5)) 3.5))
If a client attempts to send an XML stanza for which the value of the If a client attempts to send an XML stanza for which the value of the
'from' attribute does not match one of the connected resources for 'from' attribute does not match one of the connected resources for
that entity, the server SHOULD return an <invalid-from/> stream error that entity, the server SHOULD return an <invalid-from/> stream error
to the client. If a client attempts to send an XML stanza over a to the client. If a client attempts to send an XML stanza over a
stream that is not yet authenticated, the server SHOULD return a stream that is not yet authenticated, the server SHOULD return a
<not-authorized/> stream error to the client. If generated, both of <not-authorized/> stream error to the client. If generated, both of
these conditions MUST result in closing of the stream and termination these conditions MUST result in closure of the stream and termination
of the underlying TCP connection; this helps to prevent a denial of of the underlying TCP connection; this helps to prevent a denial of
service attack launched from a rogue client. service attack launched from a rogue client.
When a server generates a stanza from the server itself for delivery When a server generates a stanza from the server itself for delivery
to a connected client (e.g., in the context of data storage services to a connected client (e.g., in the context of data storage services
provided by the server on behalf of the client), the stanza MUST provided by the server on behalf of the client), the stanza MUST
either (1) not include a 'from' attribute or (2) include a 'from' either (1) not include a 'from' attribute or (2) include a 'from'
attribute whose value is the account's bare JID (<node@domain>) or attribute whose value is the account's bare JID (<node@domain>) or
client's full JID (<node@domain/resource>). A server MUST NOT send client's full JID (<node@domain/resource>). A server MUST NOT send
to the client a stanza without a 'from' attribute if the stanza was to the client a stanza without a 'from' attribute if the stanza was
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sending server (or any validated domain thereof, such as a validated sending server (or any validated domain thereof, such as a validated
subdomain of the sending server's hostname or another validated subdomain of the sending server's hostname or another validated
domain hosted by the sending server) as communicated in the SASL domain hosted by the sending server) as communicated in the SASL
negotiation or dialback negotiation; if a server receives a stanza negotiation or dialback negotiation; if a server receives a stanza
that does not meet this restriction, it MUST generate an that does not meet this restriction, it MUST generate an
<invalid-from/> stream error condition. Both of these conditions <invalid-from/> stream error condition. Both of these conditions
MUST result in closing of the stream and termination of the MUST result in closing of the stream and termination of the
underlying TCP connection; this helps to prevent a denial of service underlying TCP connection; this helps to prevent a denial of service
attack launched from a rogue server. attack launched from a rogue server.
9.1.3 id 9.1.3. id
The optional 'id' attribute MAY be used by a sending entity for The optional 'id' attribute MAY be used by a sending entity for
internal tracking of stanzas that it sends and receives (especially internal tracking of stanzas that it sends and receives (especially
for tracking the request-response interaction inherent in the for tracking the request-response interaction inherent in the
semantics of IQ stanzas). It is OPTIONAL for the value of the 'id' semantics of IQ stanzas). It is OPTIONAL for the value of the 'id'
attribute to be unique globally, within a domain, or within a stream. attribute to be unique globally, within a domain, or within a stream.
The semantics of IQ stanzas impose additional restrictions; see IQ The semantics of IQ stanzas impose additional restrictions; see IQ
Semantics (Section 9.2.3). Semantics (Section 9.2.3).
9.1.4 type 9.1.4. type
The 'type' attribute specifies detailed information about the purpose The 'type' attribute specifies detailed information about the purpose
or context of the message, presence, or IQ stanza. The particular or context of the message, presence, or IQ stanza. The particular
allowable values for the 'type' attribute vary depending on whether allowable values for the 'type' attribute vary depending on whether
the stanza is a message, presence, or IQ; the values for message and the stanza is a message, presence, or IQ; the values for message and
presence stanzas are specific to instant messaging and presence presence stanzas are specific to instant messaging and presence
applications and therefore are defined in [XMPP-IM], whereas the applications and therefore are defined in [XMPP-IM], whereas the
values for IQ stanzas specify the role of an IQ stanza in a values for IQ stanzas specify the role of an IQ stanza in a
structured request-response "conversation" and thus are defined under structured request-response "conversation" and thus are defined under
IQ Semantics (Section 9.2.3) below. The only 'type' value common to IQ Semantics (Section 9.2.3) below. The only 'type' value common to
all three stanzas is "error", for which see Stanza Errors (Section all three stanzas is "error"; see Stanza Errors (Section 9.3).
9.3).
9.1.5 xml:lang 9.1.5. xml:lang
A stanza SHOULD possess an 'xml:lang' attribute (as defined in A stanza SHOULD possess an 'xml:lang' attribute (as defined in
Section 2.12 of [XML]) if the stanza contains XML character data that Section 2.12 of [XML]) if the stanza contains XML character data that
is intended to be presented to a human user (as explained in RFC 2277 is intended to be presented to a human user (as explained in RFC 2277
[CHARSET], "internationalization is for humans"). The value of the [CHARSET], "internationalization is for humans"). The value of the
'xml:lang' attribute specifies the default language of any such 'xml:lang' attribute specifies the default language of any such
human-readable XML character data, which MAY be overridden by the human-readable XML character data, which MAY be overridden by the
'xml:lang' attribute of a specific child element. If a stanza does 'xml:lang' attribute of a specific child element. If a stanza does
not possess an 'xml:lang' attribute, an implementation MUST assume not possess an 'xml:lang' attribute, an implementation MUST assume
that the default language is that specified for the stream as defined that the default language is that specified for the stream as defined
under Stream Attributes (Section 4.4) above. The value of the under Stream Attributes (Section 4.4) above. The value of the
'xml:lang' attribute MUST be an NMTOKEN and MUST conform to the 'xml:lang' attribute MUST be an NMTOKEN and MUST conform to the
format defined in RFC 3066 [LANGTAGS]. format defined in RFC 3066 [LANGTAGS].
9.2 Basic Semantics 9.2. Basic Semantics
9.2.1 Message Semantics 9.2.1. Message Semantics
The <message/> stanza kind can be seen as a "push" mechanism whereby The <message/> stanza kind can be seen as a "push" mechanism whereby
one entity pushes information to another entity, similar to the one entity pushes information to another entity, similar to the
communications that occur in a system such as email. All message communications that occur in a system such as email. All message
stanzas SHOULD possess a 'to' attribute that specifies the intended stanzas SHOULD possess a 'to' attribute that specifies the intended
recipient of the message; upon receiving such a stanza, a server recipient of the message; upon receiving such a stanza, a server
SHOULD route or deliver it to the intended recipient (see Server SHOULD route or deliver it to the intended recipient (see Server
Rules for Handling XML Stanzas (Section 10) for general routing and Rules for Handling XML Stanzas (Section 10) for general routing and
delivery rules related to XML stanzas). delivery rules related to XML stanzas).
9.2.2 Presence Semantics 9.2.2. Presence Semantics
The <presence/> element can be seen as a basic broadcast or The <presence/> element can be seen as a basic broadcast or
"publish-subscribe" mechanism, whereby multiple entities receive "publish-subscribe" mechanism, whereby multiple entities receive
information about an entity to which they have subscribed (in this information about an entity to which they have subscribed (in this
case, network availability information). In general, a publishing case, network availability information). In general, a publishing
entity SHOULD send a presence stanza with no 'to' attribute, in which entity SHOULD send a presence stanza with no 'to' attribute, in which
case the server to which the entity is connected SHOULD broadcast or case the server to which the entity is connected SHOULD broadcast or
multiplex that stanza to all subscribing entities. However, a multiplex that stanza to all subscribing entities. However, a
publishing entity MAY also send a presence stanza with a 'to' publishing entity MAY also send a presence stanza with a 'to'
attribute, in which case the server SHOULD route or deliver that attribute, in which case the server SHOULD route or deliver that
stanza to the intended recipient. See Server Rules for Handling XML stanza to the intended recipient. See Server Rules for Handling XML
Stanzas (Section 10) for general routing and delivery rules related Stanzas (Section 10) for general routing and delivery rules related
to XML stanzas, and [XMPP-IM] for presence-specific rules in the to XML stanzas, and [XMPP-IM] for presence-specific rules in the
context of an instant messaging and presence application. context of an instant messaging and presence application.
9.2.3 IQ Semantics 9.2.3. IQ Semantics
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]. The semantics of IQ enable an entity to make a ways to [HTTP]. The semantics of IQ enable an entity to make a
request of, and receive a response from, another entity. The data request of, and receive a response from, another entity. The data
content of the request and response is defined by the namespace content of the request and response is defined by the namespace
declaration of a direct child element of the IQ element, and the declaration of a direct child element of the IQ element, and the
interaction is tracked by the requesting entity through use of the interaction is tracked by the requesting entity through use of the
'id' attribute. Thus IQ interactions follow a common pattern of 'id' attribute. Thus, IQ interactions follow a common pattern of
structured data exchange such as get/result or set/result (although structured data exchange such as get/result or set/result (although
an error may be returned in reply to a request if appropriate): an error may be returned in reply to a request if appropriate):
Requesting Responding Requesting Responding
Entity Entity Entity Entity
---------- ---------- ---------- ----------
| | | |
| <iq type='get' id='1'> | | <iq type='get' id='1'> |
| ------------------------> | | ------------------------> |
| | | |
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| <iq type='set' id='2'> | | <iq type='set' id='2'> |
| ------------------------> | | ------------------------> |
| | | |
| <iq type='error' id='2'> | | <iq type='error' id='2'> |
| <------------------------ | | <------------------------ |
| | | |
In order to enforce these semantics, the following rules apply: In order to enforce these semantics, the following rules apply:
1. The 'id' attribute is REQUIRED for IQ stanzas. 1. The 'id' attribute is REQUIRED for IQ stanzas.
2. The 'type' attribute is REQUIRED for IQ stanzas. The value MUST 2. The 'type' attribute is REQUIRED for IQ stanzas. The value MUST
be one of the following: be one of the following:
* get -- The stanza is a request for information or * get -- The stanza is a request for information or
requirements. requirements.
* set -- The stanza provides required data, sets new values, or * set -- The stanza provides required data, sets new values, or
replaces existing values. replaces existing values.
* result -- The stanza is a response to a successful get or set * result -- The stanza is a response to a successful get or set
request. request.
* error -- An error has occurred regarding processing or * error -- An error has occurred regarding processing or
delivery of a previously-sent get or set (see Stanza Errors delivery of a previously-sent get or set (see Stanza Errors
(Section 9.3)). (Section 9.3)).
3. An entity that receives an IQ request of type "get" or "set" MUST 3. An entity that receives an IQ request of type "get" or "set" MUST
reply with an IQ response of type "result" or "error" (which reply with an IQ response of type "result" or "error" (the
response MUST preserve the 'id' attribute of the request). response MUST preserve the 'id' attribute of the request).
4. An entity that receives a stanza of type "result" or "error" MUST 4. An entity that receives a stanza of type "result" or "error" MUST
NOT respond to the stanza by sending a further IQ response of NOT respond to the stanza by sending a further IQ response of
type "result" or "error"; however, as shown above, the requesting type "result" or "error"; however, as shown above, the requesting
entity MAY send another request (e.g., an IQ of type "set" in entity MAY send another request (e.g., an IQ of type "set" in
order to provide required information discovered through a get/ order to provide required information discovered through a
result pair). get/result pair).
5. An IQ stanza of type "get" or "set" MUST contain one and only one 5. An IQ stanza of type "get" or "set" MUST contain one and only one
child element that specifies the semantics of the particular child element that specifies the semantics of the particular
request or response. request or response.
6. An IQ stanza of type "result" MUST include zero or one child 6. An IQ stanza of type "result" MUST include zero or one child
elements. elements.
7. An IQ stanza of type "error" SHOULD include the child element 7. An IQ stanza of type "error" SHOULD include the child element
contained in the associated "get" or "set" and MUST include an contained in the associated "get" or "set" and MUST include an
<error/> child; for details, see Stanza Errors (Section 9.3). <error/> child; for details, see Stanza Errors (Section 9.3).
9.3 Stanza Errors 9.3. Stanza Errors
Stanza-related errors are handled in a manner similar to stream Stanza-related errors are handled in a manner similar to stream
errors (Section 4.7). However, unlike stream errors, stanza errors errors (Section 4.7). However, unlike stream errors, stanza errors
are recoverable; therefore error stanzas include hints regarding are recoverable; therefore error stanzas include hints regarding
actions that the original sender can take in order to remedy the actions that the original sender can take in order to remedy the
error. error.
9.3.1 Rules 9.3.1. Rules
The following rules apply to stanza-related errors: The following rules apply to stanza-related errors:
o The receiving or processing entity that detects an error condition o The receiving or processing entity that detects an error condition
in relation to a stanza MUST return to the sending entity a stanza in relation to a stanza MUST return to the sending entity a stanza
of the same kind (message, presence, or IQ) whose 'type' attribute of the same kind (message, presence, or IQ), whose 'type'
is set to a value of "error" (such a stanza is called an "error attribute is set to a value of "error" (such a stanza is called an
stanza" herein). "error stanza" herein).
o The entity that generates an error stanza SHOULD include the o The entity that generates an error stanza SHOULD include the
original XML sent so that the sender can inspect and if necessary original XML sent so that the sender can inspect and, if
correct the XML before attempting to resend. necessary, correct the XML before attempting to resend.
o An error stanza MUST contain an <error/> child element. o An error stanza MUST contain an <error/> child element.
o An <error/> child MUST NOT be included if the 'type' attribute has o An <error/> child MUST NOT be included if the 'type' attribute has
a value other than "error" (or if there is no 'type' attribute). a value other than "error" (or if there is no 'type' attribute).
o An entity that receives an error stanza MUST NOT respond to the o An entity that receives an error stanza MUST NOT respond to the
stanza with a further error stanza; this helps to prevent looping. stanza with a further error stanza; this helps to prevent looping.
9.3.2 Syntax 9.3.2. Syntax
The syntax for stanza-related errors is as follows: The syntax for stanza-related errors is as follows:
<stanza-kind to='sender' type='error'> <stanza-kind to='sender' type='error'>
[RECOMMENDED to include sender XML here] [RECOMMENDED to include sender XML here]
<error type='error-type'> <error type='error-type'>
<defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> <defined-condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas' <text xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'
xml:lang='langcode'> xml:lang='langcode'>
OPTIONAL descriptive text OPTIONAL descriptive text
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meaning of a defined condition or application-specific condition. It meaning of a defined condition or application-specific condition. It
SHOULD NOT be interpreted programmatically by an application. It SHOULD NOT be interpreted programmatically by an application. It
SHOULD NOT be used as the error message presented to a user, but MAY SHOULD NOT be used as the error message presented to a user, but MAY
be shown in addition to the error message associated with the be shown in addition to the error message associated with the
included condition element (or elements). included condition element (or elements).
Finally, to maintain backward compatibility, the schema (specified in Finally, to maintain backward compatibility, the schema (specified in
[XMPP-IM]) allows the optional inclusion of a 'code' attribute on the [XMPP-IM]) allows the optional inclusion of a 'code' attribute on the
<error/> element. <error/> element.
9.3.3 Defined Conditions 9.3.3. Defined Conditions
The following conditions are defined for use in stanza errors. The following conditions are defined for use in stanza errors.
o <bad-request/> -- the sender has sent XML that is malformed or o <bad-request/> -- the sender has sent XML that is malformed or
that cannot be processed (e.g., an IQ stanza that includes an that cannot be processed (e.g., an IQ stanza that includes an
unrecognized value of the 'type' attribute); the associated error unrecognized value of the 'type' attribute); the associated error
type SHOULD be "modify". type SHOULD be "modify".
o <conflict/> -- access cannot be granted because an existing o <conflict/> -- access cannot be granted because an existing
resource or session exists with the same name or address; the resource or session exists with the same name or address; the
associated error type SHOULD be "cancel". associated error type SHOULD be "cancel".
o <feature-not-implemented/> -- the feature requested is not o <feature-not-implemented/> -- the feature requested is not
implemented by the recipient or server and therefore cannot be implemented by the recipient or server and therefore cannot be
processed; the associated error type SHOULD be "cancel". processed; the associated error type SHOULD be "cancel".
o <forbidden/> -- the requesting entity does not possess the o <forbidden/> -- the requesting entity does not possess the
required permissions to perform the action; the associated error required permissions to perform the action; the associated error
type SHOULD be "auth". type SHOULD be "auth".
o <gone/> -- the recipient or server can no longer be contacted at o <gone/> -- the recipient or server can no longer be contacted at
this address (the error stanza MAY contain a new address in the this address (the error stanza MAY contain a new address in the
XML character data of the <gone/> element); the associated error XML character data of the <gone/> element); the associated error
type SHOULD be "modify". type SHOULD be "modify".
o <internal-server-error/> -- the server could not process the o <internal-server-error/> -- the server could not process the
stanza because of a misconfiguration or an otherwise-undefined stanza because of a misconfiguration or an otherwise-undefined
internal server error; the associated error type SHOULD be "wait". internal server error; the associated error type SHOULD be "wait".
o <item-not-found/> -- the addressed JID or item requested cannot be o <item-not-found/> -- the addressed JID or item requested cannot be
found; the associated error type SHOULD be "cancel". found; the associated error type SHOULD be "cancel".
o <jid-malformed/> -- the sending entity has provided or o <jid-malformed/> -- the sending entity has provided or
communicated an XMPP address (e.g., a value of the 'to' attribute) communicated an XMPP address (e.g., a value of the 'to' attribute)
or aspect thereof (e.g., a resource identifier) that does not or aspect thereof (e.g., a resource identifier) that does not
adhere to the syntax defined in Addressing Scheme (Section 3); the adhere to the syntax defined in Addressing Scheme (Section 3); the
associated error type SHOULD be "modify". associated error type SHOULD be "modify".
o <not-acceptable/> -- the recipient or server understands the o <not-acceptable/> -- the recipient or server understands the
request but is refusing to process it because it does not meet request but is refusing to process it because it does not meet
criteria defined by the recipient or server (e.g., a local policy criteria defined by the recipient or server (e.g., a local policy
regarding acceptable words in messages); the associated error type regarding acceptable words in messages); the associated error type
SHOULD be "modify". SHOULD be "modify".
o <not-allowed/> -- the recipient or server does not allow any o <not-allowed/> -- the recipient or server does not allow any
entity to perform the action; the associated error type SHOULD be entity to perform the action; the associated error type SHOULD be
"cancel". "cancel".
o <not-authorized/> -- the sender must provide proper credentials o <not-authorized/> -- the sender must provide proper credentials
before being allowed to perform the action, or has provided before being allowed to perform the action, or has provided
improper credentials; the associated error type SHOULD be "auth". improper credentials; the associated error type SHOULD be "auth".
o <payment-required/> -- the requesting entity is not authorized to o <payment-required/> -- the requesting entity is not authorized to
access the requested service because payment is required; the access the requested service because payment is required; the
associated error type SHOULD be "auth". associated error type SHOULD be "auth".
o <recipient-unavailable/> -- the intended recipient is temporarily o <recipient-unavailable/> -- the intended recipient is temporarily
unavailable; the associated error type SHOULD be "wait" (note: an unavailable; the associated error type SHOULD be "wait" (note: an
application MUST NOT return this error if doing so would provide application MUST NOT return this error if doing so would provide
information about the intended recipient's network availability to information about the intended recipient's network availability to
an entity that is not authorized to know such information). an entity that is not authorized to know such information).
o <redirect/> -- the recipient or server is redirecting requests for o <redirect/> -- the recipient or server is redirecting requests for
this information to another entity, usually temporarily (the error this information to another entity, usually temporarily (the error
stanza SHOULD contain the alternate address, which MUST be a valid stanza SHOULD contain the alternate address, which MUST be a valid
JID, in the XML character data of the <redirect/> element); the JID, in the XML character data of the <redirect/> element); the
associated error type SHOULD be "modify". associated error type SHOULD be "modify".
o <registration-required/> -- the requesting entity is not o <registration-required/> -- the requesting entity is not
authorized to access the requested service because registration is authorized to access the requested service because registration is
required; the associated error type SHOULD be "auth". required; the associated error type SHOULD be "auth".
o <remote-server-not-found/> -- a remote server or service specified o <remote-server-not-found/> -- a remote server or service specified
as part or all of the JID of the intended recipient does not as part or all of the JID of the intended recipient does not
exist; the associated error type SHOULD be "cancel". exist; the associated error type SHOULD be "cancel".
o <remote-server-timeout/> -- a remote server or service specified o <remote-server-timeout/> -- a remote server or service specified
as part or all of the JID of the intended recipient (or required as part or all of the JID of the intended recipient (or required
to fulfill a request) could not be contacted within a reasonable to fulfill a request) could not be contacted within a reasonable
amount of time; the associated error type SHOULD be "wait". amount of time; the associated error type SHOULD be "wait".
o <resource-constraint/> -- the server or recipient lacks the system o <resource-constraint/> -- the server or recipient lacks the system
resources necessary to service the request; the associated error resources necessary to service the request; the associated error
type SHOULD be "wait". type SHOULD be "wait".
o <service-unavailable/> -- the server or recipient does not o <service-unavailable/> -- the server or recipient does not
currently provide the requested service; the associated error type currently provide the requested service; the associated error type
SHOULD be "cancel". SHOULD be "cancel".
o <subscription-required/> -- the requesting entity is not o <subscription-required/> -- the requesting entity is not
authorized to access the requested service because a subscription authorized to access the requested service because a subscription
is required; the associated error type SHOULD be "auth". is required; the associated error type SHOULD be "auth".
o <undefined-condition/> -- the error condition is not one of those o <undefined-condition/> -- the error condition is not one of those
defined by the other conditions in this list; any error type may defined by the other conditions in this list; any error type may
be associated with this condition, and it SHOULD be used only in be associated with this condition, and it SHOULD be used only in
conjunction with an application-specific condition. conjunction with an application-specific condition.
o <unexpected-request/> -- the recipient or server understood the o <unexpected-request/> -- the recipient or server understood the
request but was not expecting it at this time (e.g., the request request but was not expecting it at this time (e.g., the request
was out of order); the associated error type SHOULD be "wait". was out of order); the associated error type SHOULD be "wait".
9.3.4 Application-Specific Conditions 9.3.4. Application-Specific Conditions
As noted, an application MAY provide application-specific stanza As noted, an application MAY provide application-specific stanza
error information by including a properly-namespaced child in the error information by including a properly-namespaced child in the
error element. The application-specific element SHOULD supplement or error element. The application-specific element SHOULD supplement or
further qualify a defined element. Thus the <error/> element will further qualify a defined element. Thus, the <error/> element will
contain two or three child elements: contain two or three child elements:
<iq type='error' id='some-id'> <iq type='error' id='some-id'>
<error type='modify'> <error type='modify'>
<bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> <bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
<too-many-parameters xmlns='application-ns'/> <too-many-parameters xmlns='application-ns'/>
</error> </error>
</iq> </iq>
<message type='error' id='another-id'> <message type='error' id='another-id'>
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Compliant server implementations MUST ensure in-order processing of Compliant server implementations MUST ensure in-order processing of
XML stanzas between any two entities. XML stanzas between any two entities.
Beyond the requirement for in-order processing, each server Beyond the requirement for in-order processing, each server
implementation will contain its own "delivery tree" for handling implementation will contain its own "delivery tree" for handling
stanzas it receives. Such a tree determines whether a stanza needs stanzas it receives. Such a tree determines whether a stanza needs
to be routed to another domain, processed internally, or delivered to to be routed to another domain, processed internally, or delivered to
a resource associated with a connected node. The following rules a resource associated with a connected node. The following rules
apply: apply:
10.1 No 'to' Address 10.1. No 'to' Address
If the stanza possesses no 'to' attribute, the server SHOULD process If the stanza possesses no 'to' attribute, the server SHOULD process
it on behalf of the entity that sent it. Because all stanzas it on behalf of the entity that sent it. Because all stanzas
received from other servers MUST possess a 'to' attribute, this rule received from other servers MUST possess a 'to' attribute, this rule
applies only to stanzas received from a registered entity (such as a applies only to stanzas received from a registered entity (such as a
client) that is connected to the server. If the server receives a client) that is connected to the server. If the server receives a
presence stanza with no 'to' attribute, the server SHOULD broadcast presence stanza with no 'to' attribute, the server SHOULD broadcast
it to the entities that are subscribed to the sending entity's it to the entities that are subscribed to the sending entity's
presence, if applicable (the semantics of presence broadcast for presence, if applicable (the semantics of presence broadcast for
instant messaging and presence applications are defined in instant messaging and presence applications are defined in
[XMPP-IM]). If the server receives an IQ stanza of type "get" or [XMPP-IM]). If the server receives an IQ stanza of type "get" or
"set" with no 'to' attribute and it understands the namespace that "set" with no 'to' attribute and it understands the namespace that
qualifies the content of the stanza, it MUST either process the qualifies the content of the stanza, it MUST either process the
stanza on behalf of sending entity (where the meaning of "process" is stanza on behalf of the sending entity (where the meaning of
determined by the semantics of the qualifying namespace) or return an "process" is determined by the semantics of the qualifying namespace)
error to the sending entity. or return an error to the sending entity.
10.2 Foreign Domain 10.2. Foreign Domain
If the hostname of the domain identifier portion of the JID contained If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute does not match one of the configured hostnames in the 'to' attribute does not match one of the configured hostnames
of the server itself or a subdomain thereof, the server SHOULD route of the server itself or a subdomain thereof, the server SHOULD route
the stanza to the foreign domain (subject to local service the stanza to the foreign domain (subject to local service
provisioning and security policies regarding inter-domain provisioning and security policies regarding inter-domain
communication). There are two possible cases: communication). There are two possible cases:
A server-to-server stream already exists between the two domains: The A server-to-server stream already exists between the two domains: The
sender's server routes the stanza to the authoritative server for sender's server routes the stanza to the authoritative server for
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(as defined under Use of TLS (Section 5) and Use of SASL (Section (as defined under Use of TLS (Section 5) and Use of SASL (Section
6)), and (3) routes the stanza to the authoritative server for the 6)), and (3) routes the stanza to the authoritative server for the
foreign domain over the newly-established stream foreign domain over the newly-established stream
If routing to the recipient's server is unsuccessful, the sender's If routing to the recipient's server is unsuccessful, the sender's
server MUST return an error to the sender; if the recipient's server server MUST return an error to the sender; if the recipient's server
can be contacted but delivery by the recipient's server to the can be contacted but delivery by the recipient's server to the
recipient is unsuccessful, the recipient's server MUST return an recipient is unsuccessful, the recipient's server MUST return an
error to the sender by way of the sender's server. error to the sender by way of the sender's server.
10.3 Subdomain 10.3. Subdomain
If the hostname of the domain identifier portion of the JID contained If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches a subdomain of one of the configured in the 'to' attribute matches a subdomain of one of the configured
hostnames of the server itself, the server MUST either process the hostnames of the server itself, the server MUST either process the
stanza itself or route the stanza to a specialized service that is stanza itself or route the stanza to a specialized service that is
responsible for that subdomain (if the subdomain is configured), or responsible for that subdomain (if the subdomain is configured), or
return an error to the sender (if the subdomain is not configured). return an error to the sender (if the subdomain is not configured).
10.4 Mere Domain or Specific Resource 10.4. Mere Domain or Specific Resource
If the hostname of the domain identifier portion of the JID contained If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches a configured hostname of the server in the 'to' attribute matches a configured hostname of the server
itself and the JID contained in the 'to' attribute is of the form itself and the JID contained in the 'to' attribute is of the form
<domain> or <domain/resource>, the server (or a defined resource <domain> or <domain/resource>, the server (or a defined resource
thereof) MUST either process the stanza as appropriate for the stanza thereof) MUST either process the stanza as appropriate for the stanza
kind or return an error stanza to the sender. kind or return an error stanza to the sender.
10.5 Node in Same Domain 10.5. Node in Same Domain
If the hostname of the domain identifier portion of the JID contained If the hostname of the domain identifier portion of the JID contained
in the 'to' attribute matches a configured hostname of the server in the 'to' attribute matches a configured hostname of the server
itself and the JID contained in the 'to' attribute is of the form itself and the JID contained in the 'to' attribute is of the form
<node@domain> or <node@domain/resource>, the server SHOULD deliver <node@domain> or <node@domain/resource>, the server SHOULD deliver
the stanza to the intended recipient of the stanza as represented by the stanza to the intended recipient of the stanza as represented by
the JID contained in the 'to' attribute. The following rules apply: the JID contained in the 'to' attribute. The following rules apply:
1. If the JID contains a resource identifier (i.e., is of the form 1. If the JID contains a resource identifier (i.e., is of the form
<node@domain/resource>) and there exists a connected resource <node@domain/resource>) and there exists a connected resource
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itself and the JID contained in the 'to' attribute is of the form itself and the JID contained in the 'to' attribute is of the form
<node@domain> or <node@domain/resource>, the server SHOULD deliver <node@domain> or <node@domain/resource>, the server SHOULD deliver
the stanza to the intended recipient of the stanza as represented by the stanza to the intended recipient of the stanza as represented by
the JID contained in the 'to' attribute. The following rules apply: the JID contained in the 'to' attribute. The following rules apply:
1. If the JID contains a resource identifier (i.e., is of the form 1. If the JID contains a resource identifier (i.e., is of the form
<node@domain/resource>) and there exists a connected resource <node@domain/resource>) and there exists a connected resource
that matches the full JID, the recipient's server SHOULD deliver that matches the full JID, the recipient's server SHOULD deliver
the stanza to the stream or session that exactly matches the the stanza to the stream or session that exactly matches the
resource identifier. resource identifier.
2. If the JID contains a resource identifier and there exists no 2. If the JID contains a resource identifier and there exists no
connected resource that matches the full JID, the recipient's connected resource that matches the full JID, the recipient's
server SHOULD return a <service-unavailable/> stanza error to the server SHOULD return a <service-unavailable/> stanza error to the
sender. sender.
3. If the JID is of the form <node@domain> and there exists at least 3. If the JID is of the form <node@domain> and there exists at least
one connected resource for the node, the recipient's server one connected resource for the node, the recipient's server
SHOULD deliver the stanza to at least one of the connected SHOULD deliver the stanza to at least one of the connected
resources, according to application-specific rules (a set of resources, according to application-specific rules (a set of
delivery rules for instant messaging and presence applications is delivery rules for instant messaging and presence applications is
defined in [XMPP-IM]). defined in [XMPP-IM]).
11. XML Usage within XMPP 11. XML Usage within XMPP
11.1 Restrictions 11.1. Restrictions
XMPP is a simplified and specialized protocol for streaming XML XMPP is a simplified and specialized protocol for streaming XML
elements in order to exchange structured information in close to real elements in order to exchange structured information in close to real
time. Because XMPP does not require the parsing of arbitrary and time. Because XMPP does not require the parsing of arbitrary and
complete XML documents, there is no requirement that XMPP needs to complete XML documents, there is no requirement that XMPP needs to
support the full feature set of [XML]. In particular, the following support the full feature set of [XML]. In particular, the following
restrictions apply. restrictions apply.
With regard to XML generation, an XMPP implementation MUST NOT inject With regard to XML generation, an XMPP implementation MUST NOT inject
into an XML stream any of the following: into an XML stream any of the following:
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elements in order to exchange structured information in close to real elements in order to exchange structured information in close to real
time. Because XMPP does not require the parsing of arbitrary and time. Because XMPP does not require the parsing of arbitrary and
complete XML documents, there is no requirement that XMPP needs to complete XML documents, there is no requirement that XMPP needs to
support the full feature set of [XML]. In particular, the following support the full feature set of [XML]. In particular, the following
restrictions apply. restrictions apply.
With regard to XML generation, an XMPP implementation MUST NOT inject With regard to XML generation, an XMPP implementation MUST NOT inject
into an XML stream any of the following: into an XML stream any of the following:
o comments (as defined in Section 2.5 of [XML]) o comments (as defined in Section 2.5 of [XML])
o processing instructions (Section 2.6 therein) o processing instructions (Section 2.6 therein)
o internal or external DTD subsets (Section 2.8 therein) o internal or external DTD subsets (Section 2.8 therein)
o internal or external entity references (Section 4.2 therein) with o internal or external entity references (Section 4.2 therein) with
the exception of predefined entities (Section 4.6 therein) the exception of predefined entities (Section 4.6 therein)
o character data or attribute values containing unescaped characters o character data or attribute values containing unescaped characters
that map to the predefined entities (Section 4.6 therein); such that map to the predefined entities (Section 4.6 therein); such
characters MUST be escaped characters MUST be escaped
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.
11.2 XML Namespace Names and Prefixes 11.2. XML Namespace Names and Prefixes
XML Namespaces [XML-NAMES] are used within all XMPP-compliant XML to XML Namespaces [XML-NAMES] are used within all XMPP-compliant XML to
create strict boundaries of data ownership. The basic function of create strict boundaries of data ownership. The basic function of
namespaces is to separate different vocabularies of XML elements that namespaces is to separate different vocabularies of XML elements that
are structurally mixed together. Ensuring that XMPP-compliant XML is are structurally mixed together. Ensuring that XMPP-compliant XML is
namespace-aware enables any allowable XML to be structurally mixed namespace-aware enables any allowable XML to be structurally mixed
with any data element within XMPP. Rules for XML namespace names and with any data element within XMPP. Rules for XML namespace names and
prefixes are defined in the following subsections. prefixes are defined in the following subsections.
11.2.1 Streams Namespace 11.2.1. Streams Namespace
A streams namespace declaration is REQUIRED in all XML stream A streams namespace declaration is REQUIRED in all XML stream
headers. The name of the streams namespace MUST be 'http:// headers. The name of the streams namespace MUST be
etherx.jabber.org/streams'. The element names of the <stream/> 'http://etherx.jabber.org/streams'. The element names of the
element and its <features/> and <error/> children MUST be qualified <stream/> element and its <features/> and <error/> children MUST be
by the streams namespace prefix in all instances. An implementation qualified by the streams namespace prefix in all instances. An
SHOULD generate only the 'stream:' prefix for these elements, and for implementation SHOULD generate only the 'stream:' prefix for these
historical reasons MAY accept only the 'stream:' prefix. elements, and for historical reasons MAY accept only the 'stream:'
prefix.
11.2.2 Default Namespace 11.2.2. Default Namespace
A default namespace declaration is REQUIRED and is used in all XML A default namespace declaration is REQUIRED and is used in all XML
streams in order to define the allowable first-level children of the streams in order to define the allowable first-level children of the
root stream element. This namespace declaration MUST be the same for root stream element. This namespace declaration MUST be the same for
the initial stream and the response stream so that both streams are the initial stream and the response stream so that both streams are
qualified consistently. The default namespace declaration applies to qualified consistently. The default namespace declaration applies to
the stream and all stanzas sent within a stream (unless explicitly the stream and all stanzas sent within a stream (unless explicitly
qualified by another namespace, or by the prefix of the streams qualified by another namespace, or by the prefix of the streams
namespace or the dialback namespace). namespace or the dialback namespace).
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communications for 'jabber:client' and server-to-server communications for 'jabber:client' and server-to-server
communications for 'jabber:server'). The only difference between the communications for 'jabber:server'). The only difference between the
two is that the 'to' and 'from' attributes are OPTIONAL on stanzas two is that the 'to' 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 sent within 'jabber:server'. If a compliant implementation accepts a
stream that is qualified by the 'jabber:client' or 'jabber:server' stream that is qualified by the 'jabber:client' or 'jabber:server'
namespace, it MUST support the common attributes (Section 9.1) and namespace, it MUST support the common attributes (Section 9.1) and
basic semantics (Section 9.2) of all three core stanza kinds basic semantics (Section 9.2) of all three core stanza kinds
(message, presence, and IQ). (message, presence, and IQ).
11.2.3 Dialback Namespace 11.2.3. Dialback Namespace
A dialback namespace declaration is REQUIRED for all elements used in A dialback namespace declaration is REQUIRED for all elements used in
server dialback (Section 8). The name of the dialback namespace MUST server dialback (Section 8). The name of the dialback namespace MUST
be 'jabber:server:dialback'. All elements qualified by this be 'jabber:server:dialback'. All elements qualified by this
namespace MUST be prefixed. An implementation SHOULD generate only namespace MUST be prefixed. An implementation SHOULD generate only
the 'db:' prefix for such elements and MAY accept only the 'db:' the 'db:' prefix for such elements and MAY accept only the 'db:'
prefix. prefix.
11.3 Validation 11.3. Validation
Except as noted with regard to 'to' and 'from' addresses for stanzas Except as noted with regard to 'to' and 'from' addresses for stanzas
within the 'jabber:server' namespace, a server is not responsible for within the 'jabber:server' namespace, a server is not responsible for
validating the XML elements forwarded to a client or another server; validating the XML elements forwarded to a client or another server;
an implementation MAY choose to provide only validated data elements an implementation MAY choose to provide only validated data elements
but this is OPTIONAL (although an implementation MUST NOT accept XML but this is OPTIONAL (although an implementation MUST NOT accept XML
that is not well-formed). Clients SHOULD NOT rely on the ability to that is not well-formed). Clients SHOULD NOT rely on the ability to
send data which does not conform to the schemas, and SHOULD ignore send data which does not conform to the schemas, and SHOULD ignore
any non-conformant elements or attributes on the incoming XML stream. any non-conformant elements or attributes on the incoming XML stream.
Validation of XML streams and stanzas is OPTIONAL, and schemas are Validation of XML streams and stanzas is OPTIONAL, and schemas are
included herein for descriptive purposes only. included herein for descriptive purposes only.
11.4 Inclusion of Text Declaration 11.4. Inclusion of Text Declaration
Implementations SHOULD send a text declaration before sending a Implementations SHOULD send a text declaration before sending a
stream header. Applications MUST follow the rules in [XML] regarding stream header. Applications MUST follow the rules in [XML] regarding
the circumstances under which a text declaration is included. the circumstances under which a text declaration is included.
11.5 Character Encoding 11.5. Character Encoding
Implementations MUST support the UTF-8 (RFC 3269 [UTF-8]) Implementations MUST support the UTF-8 (RFC 3629 [UTF-8])
transformation of Universal Character Set (ISO/IEC 10646-1 [UCS2]) transformation of Universal Character Set (ISO/IEC 10646-1 [UCS2])
characters, as required by RFC 2277 [CHARSET]. Implementations MUST characters, as required by RFC 2277 [CHARSET]. Implementations MUST
NOT attempt to use any other encoding. NOT attempt to use any other encoding.
12. Core Compliance Requirements 12. Core Compliance Requirements
This section summarizes the specific aspects of the Extensible This section summarizes the specific aspects of the Extensible
Messaging and Presence Protocol that MUST be supported by servers and Messaging and Presence Protocol that MUST be supported by servers and
clients in order to be considered compliant implementations, as well clients in order to be considered compliant implementations, as well
as additional protocol aspects that SHOULD be supported. For as additional protocol aspects that SHOULD be supported. For
compliance purposes, we draw a distinction between core protocols compliance purposes, we draw a distinction between core protocols
(which MUST be supported by any server or client, regardless of the (which MUST be supported by any server or client, regardless of the
specific application) and instant messaging protocols (which MUST be specific application) and instant messaging protocols (which MUST be
supported only by instant messaging and presence applications built supported only by instant messaging and presence applications built
on top of the core protocols). Compliance requirements that apply to on top of the core protocols). Compliance requirements that apply to
all servers and clients are specified in this section; compliance all servers and clients are specified in this section; compliance
requirements for instant messaging servers and clients are specified requirements for instant messaging servers and clients are specified
in the corresponding section of [XMPP-IM]. in the corresponding section of [XMPP-IM].
12.1 Servers 12.1. Servers
In addition to all defined requirements with regard to security, XML In addition to all defined requirements with regard to security, XML
usage, and internationalization, a server MUST support the following usage, and internationalization, a server MUST support the following
core protocols in order to be considered compliant: core protocols in order to be considered compliant:
o Application of the [NAMEPREP], Nodeprep (Appendix A), and o Application of the [NAMEPREP], Nodeprep (Appendix A), and
Resourceprep (Appendix B) profiles of [STRINGPREP] to addresses Resourceprep (Appendix B) profiles of [STRINGPREP] to addresses
(including ensuring that domain identifiers are internationalized (including ensuring that domain identifiers are internationalized
domain names as defined in [IDNA]) domain names as defined in [IDNA])
o XML streams (Section 4), including Use of TLS (Section 5), Use of o XML streams (Section 4), including Use of TLS (Section 5), Use of
SASL (Section 6), and Resource Binding (Section 7) SASL (Section 6), and Resource Binding (Section 7)
o The basic semantics of the three defined stanza kinds (i.e., o The basic semantics of the three defined stanza kinds (i.e.,
<message/>, <presence/>, and <iq/>) as specified in stanza <message/>, <presence/>, and <iq/>) as specified in stanza
semantics (Section 9.2) semantics (Section 9.2)
o Generation (and, where appropriate, handling) of error syntax and o Generation (and, where appropriate, handling) of error syntax and
semantics related to streams, TLS, SASL, and XML stanzas semantics related to streams, TLS, SASL, and XML stanzas
In addition, a server MAY support the following core protocol: In addition, a server MAY support the following core protocol:
o Server dialback (Section 8) o Server dialback (Section 8)
12.2 Clients 12.2. Clients
A client MUST support the following core protocols in order to be A client MUST support the following core protocols in order to be
considered compliant: considered compliant:
o XML streams (Section 4), including Use of TLS (Section 5), Use of o XML streams (Section 4), including Use of TLS (Section 5), Use of
SASL (Section 6), and Resource Binding (Section 7) SASL (Section 6), and Resource Binding (Section 7)
o The basic semantics of the three defined stanza kinds (i.e., o The basic semantics of the three defined stanza kinds (i.e.,
<message/>, <presence/>, and <iq/>) as specified in stanza <message/>, <presence/>, and <iq/>) as specified in stanza
semantics (Section 9.2) semantics (Section 9.2)
o Handling (and, where appropriate, generation) of error syntax and o Handling (and, where appropriate, generation) of error syntax and
semantics related to streams, TLS, SASL, and XML stanzas semantics related to streams, TLS, SASL, and XML stanzas
In addition, a client SHOULD support the following core protocols: In addition, a client SHOULD support the following core protocols:
o Generation of addresses to which the [NAMEPREP], Nodeprep o Generation of addresses to which the [NAMEPREP], Nodeprep
(Appendix A), and Resourceprep (Appendix B) profiles of (Appendix A), and Resourceprep (Appendix B) profiles of
[STRINGPREP] can be applied without failing [STRINGPREP] can be applied without failing
13. Internationalization Considerations 13. Internationalization Considerations
XML streams MUST be encoded in UTF-8 as specified under Character XML streams MUST be encoded in UTF-8 as specified under Character
Encoding (Section 11.5). As specified under Stream Attributes Encoding (Section 11.5). As specified under Stream Attributes
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user. As specified under xml:lang (Section 9.1.5), an XML stanza user. As specified under xml:lang (Section 9.1.5), an XML stanza
SHOULD include an 'xml:lang' attribute if the stanza contains XML SHOULD include an 'xml:lang' attribute if the stanza contains XML
character data that is intended to be presented to a human user. A character data that is intended to be presented to a human user. A
server SHOULD apply the default 'xml:lang' attribute to stanzas it server SHOULD apply the default 'xml:lang' attribute to stanzas it
routes or delivers on behalf of connected entities, and MUST NOT routes or delivers on behalf of connected entities, and MUST NOT
modify or delete 'xml:lang' attributes from stanzas it receives from modify or delete 'xml:lang' attributes from stanzas it receives from
other entities. other entities.
14. Security Considerations 14. Security Considerations
14.1 High Security 14.1. High Security
For the purposes of XMPP communications (client-to-server and For the purposes of XMPP communications (client-to-server and
server-to-server), the term "high security" refers to the use of server-to-server), the term "high security" refers to the use of
security technologies that provide both mutual authentication and security technologies that provide both mutual authentication and
integrity-checking; in particular, when using certificate-based integrity-checking; in particular, when using certificate-based
authentication to provide high security, a chain-of-trust SHOULD be authentication to provide high security, a chain-of-trust SHOULD be
established out-of-band, although a shared certificate authority established out-of-band, although a shared certificate authority
signing certificates could allow a previously unknown certificate to signing certificates could allow a previously unknown certificate to
establish trust in-band. See Section 14.2 below regarding establish trust in-band. See Section 14.2 below regarding
certificate validation procedures. certificate validation procedures.
Implementations MUST support high security. Service provisioning Implementations MUST support high security. Service provisioning
SHOULD use high security, subject to local security policies. SHOULD use high security, subject to local security policies.
14.2 Certificate Validation 14.2. Certificate Validation
When an XMPP peer communicates with another peer securely, it MUST When an XMPP peer communicates with another peer securely, it MUST
validate the peer's certificate. There are three possible cases: validate the peer's certificate. There are three possible cases:
Case #1: The peer contains an End Entity certificate which appears to Case #1: The peer contains an End Entity certificate which appears to
be certified by a chain of certificates terminating in a trust be certified by a chain of certificates terminating in a trust
anchor (as described in Section 6.1 of [X509]). anchor (as described in Section 6.1 of [X509]).
Case #2: The peer certificate is certified by a Certificate Authority Case #2: The peer certificate is certified by a Certificate Authority
not known to the validating peer. not known to the validating peer.
Case #3: The peer certificate is self-signed. Case #3: The peer certificate is self-signed.
In Case #1, the validating peer MUST do one of two things: In Case #1, the validating peer MUST do one of two things:
1. Verify the peer certificate according to the rules of [X509]. 1. Verify the peer certificate according to the rules of [X509].
The certificate SHOULD then be checked against the expected The certificate SHOULD then be checked against the expected
identity of the peer following the rules described in [HTTP-TLS], identity of the peer following the rules described in [HTTP-TLS],
except that a subjectAltName extension of type "xmpp" MUST be except that a subjectAltName extension of type "xmpp" MUST be
used as the identity if present. If one of these checks fails, used as the identity if present. If one of these checks fails,
user-oriented clients MUST either notify the user (clients MAY user-oriented clients MUST either notify the user (clients MAY
give the user the opportunity to continue with the connection in give the user the opportunity to continue with the connection in
any case) or terminate the connection with a bad certificate any case) or terminate the connection with a bad certificate
error. Automated clients SHOULD terminate the connection (with a error. Automated clients SHOULD terminate the connection (with a
bad certificate error) and log the error to an appropriate audit bad certificate error) and log the error to an appropriate audit
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The certificate SHOULD then be checked against the expected The certificate SHOULD then be checked against the expected
identity of the peer following the rules described in [HTTP-TLS], identity of the peer following the rules described in [HTTP-TLS],
except that a subjectAltName extension of type "xmpp" MUST be except that a subjectAltName extension of type "xmpp" MUST be
used as the identity if present. If one of these checks fails, used as the identity if present. If one of these checks fails,
user-oriented clients MUST either notify the user (clients MAY user-oriented clients MUST either notify the user (clients MAY
give the user the opportunity to continue with the connection in give the user the opportunity to continue with the connection in
any case) or terminate the connection with a bad certificate any case) or terminate the connection with a bad certificate
error. Automated clients SHOULD terminate the connection (with a error. Automated clients SHOULD terminate the connection (with a
bad certificate error) and log the error to an appropriate audit bad certificate error) and log the error to an appropriate audit
log. Automated clients MAY provide a configuration setting that log. Automated clients MAY provide a configuration setting that
disables this check, but MUST provide a setting which enables it. disables this check, but MUST provide a setting that enables it.
2. The peer SHOULD show the certificate to a user for approval, 2. The peer SHOULD show the certificate to a user for approval,
including the entire certificate chain. The peer MUST cache the including the entire certificate chain. The peer MUST cache the
certificate (or some non-forgeable representation such as a certificate (or some non-forgeable representation such as a
hash). In future connections, the peer MUST verify that the same hash). In future connections, the peer MUST verify that the same
certificate was presented and MUST notify the user if it has certificate was presented and MUST notify the user if it has
changed. changed.
In Case #2 and Case #3, implementations SHOULD act as in (2) above. In Case #2 and Case #3, implementations SHOULD act as in (2) above.
14.3 Client-to-Server Communications 14.3. Client-to-Server Communications
A compliant client implementation MUST support both TLS and SASL for A compliant client implementation MUST support both TLS and SASL for
connections to a server. connections to a server.
The TLS protocol for encrypting XML streams (defined under Use of TLS The TLS protocol for encrypting XML streams (defined under Use of TLS
(Section 5)) provides a reliable mechanism for helping to ensure the (Section 5)) provides a reliable mechanism for helping to ensure the
confidentiality and data integrity of data exchanged between two confidentiality and data integrity of data exchanged between two
entities. entities.
The SASL protocol for authenticating XML streams (defined under Use The SASL protocol for authenticating XML streams (defined under Use
skipping to change at page 63, line 33 skipping to change at page 66, line 7
that a client connecting to a server is who it claims to be. that a client connecting to a server is who it claims to be.
Client-to-server communications MUST NOT proceed until the DNS Client-to-server communications MUST NOT proceed until the DNS
hostname asserted by the server has been resolved. Such resolutions hostname asserted by the server has been resolved. Such resolutions
SHOULD first attempt to resolve the hostname using an [SRV] Service SHOULD first attempt to resolve the hostname using an [SRV] Service
of "xmpp-client" and Proto of "tcp", resulting in resource records of "xmpp-client" and Proto of "tcp", resulting in resource records
such as "_xmpp-client._tcp.example.com." (the use of the string such as "_xmpp-client._tcp.example.com." (the use of the string
"xmpp-client" for the service identifier is consistent with the IANA "xmpp-client" for the service identifier is consistent with the IANA
registration). If the SRV lookup fails, the fallback is a normal registration). If the SRV lookup fails, the fallback is a normal
IPv4/IPv6 address record resolution to determine the IP address, IPv4/IPv6 address record resolution to determine the IP address,
using the "xmpp-client" port of 5222 registered with the IANA. using the "xmpp-client" port of 5222, registered with the IANA.
The IP address and method of access of clients MUST NOT be made The IP address and method of access of clients MUST NOT be made
public by a server, nor are any connections other than the original public by a server, nor are any connections other than the original
server connection required. This helps to protect the client's server connection required. This helps to protect the client's
server from direct attack or identification by third parties. server from direct attack or identification by third parties.
14.4 Server-to-Server Communications 14.4. Server-to-Server Communications
A compliant server implementation MUST support both TLS and SASL for A compliant server implementation MUST support both TLS and SASL for
inter-domain communications. For historical reasons, a compliant inter-domain communications. For historical reasons, a compliant
implementation SHOULD also support Server Dialback (Section 8). implementation SHOULD also support Server Dialback (Section 8).
Because service provisioning is a matter of policy, it is OPTIONAL Because service provisioning is a matter of policy, it is OPTIONAL
for any given domain to communicate with other domains, and for any given domain to communicate with other domains, and
server-to-server communications MAY be disabled by the administrator server-to-server communications MAY be disabled by the administrator
of any given deployment. If a particular domain enables inter-domain of any given deployment. If a particular domain enables inter-domain
communications, it SHOULD enable high security. communications, it SHOULD enable high security.
skipping to change at page 64, line 22 skipping to change at page 66, line 43
first attempt to resolve the hostname using an [SRV] Service of first attempt to resolve the hostname using an [SRV] Service of
"xmpp-server" and Proto of "tcp", resulting in resource records such "xmpp-server" and Proto of "tcp", resulting in resource records such
as "_xmpp-server._tcp.example.com." (the use of the string as "_xmpp-server._tcp.example.com." (the use of the string
"xmpp-server" for the service identifier is consistent with the IANA "xmpp-server" for the service identifier is consistent with the IANA
registration; note well that the "xmpp-server" service identifier registration; note well that the "xmpp-server" service identifier
supersedes the earlier use of a "jabber" service identifier, since supersedes the earlier use of a "jabber" service identifier, since
the earlier usage did not conform to [SRV]; implementations desiring the earlier usage did not conform to [SRV]; implementations desiring
to be backward compatible should continue to look for or answer to to be backward compatible should continue to look for or answer to
the "jabber" service identifier as well). If the SRV lookup fails, the "jabber" service identifier as well). If the SRV lookup fails,
the fallback is a normal IPv4/IPv6 address record resolution to the fallback is a normal IPv4/IPv6 address record resolution to
determine the IP address, using the "xmpp-server" port of 5269 determine the IP address, using the "xmpp-server" port 5269,
registered with the IANA. registered with the IANA.
Server dialback helps protect against domain spoofing, thus making it Server dialback helps protect against domain spoofing, thus making it
more difficult to spoof XML stanzas. It is not a mechanism for more difficult to spoof XML stanzas. It is not a mechanism for
authenticating, securing, or encrypting streams between servers as is authenticating, securing, or encrypting streams between servers as is
done via SASL and TLS, and results in weak verification of server done via SASL and TLS, and results in weak verification of server
identities only. Furthermore, it is susceptible to DNS poisoning identities only. Furthermore, it is susceptible to DNS poisoning
attacks unless DNSSec [DNSSEC] is used, and even if the DNS attacks unless DNSSec [DNSSEC] is used, and even if the DNS
information is accurate, dialback cannot protect from attacks where information is accurate, dialback cannot protect from attacks where
the attacker is capable of hijacking the IP address of the remote the attacker is capable of hijacking the IP address of the remote
domain. Domains requiring robust security SHOULD use TLS and SASL. domain. Domains requiring robust security SHOULD use TLS and SASL.
If SASL is used for server-to-server authentication, dialback SHOULD If SASL is used for server-to-server authentication, dialback SHOULD
NOT be used since it is unnecessary. NOT be used since it is unnecessary.
14.5 Order of Layers 14.5. Order of Layers
The order of layers in which protocols MUST be stacked is as follows: The order of layers in which protocols MUST be stacked is as follows:
1. TCP 1. TCP
2. TLS 2. TLS
3. SASL 3. SASL
4. XMPP 4. XMPP
The rationale for this order is that [TCP] is the base connection The rationale for this order is that [TCP] is the base connection
layer used by all of the protocols stacked on top of TCP, [TLS] is layer used by all of the protocols stacked on top of TCP, [TLS] is
often provided at the operating system layer, [SASL] is often often provided at the operating system layer, [SASL] is often
provided at the application layer, and XMPP is the application provided at the application layer, and XMPP is the application
itself. itself.
14.6 Lack of SASL Channel Binding to TLS 14.6. Lack of SASL Channel Binding to TLS
The SASL framework does not provide a mechanism to bind SASL The SASL framework does not provide a mechanism to bind SASL
authentication to a security layer providing confidentiality and authentication to a security layer providing confidentiality and
integrity protection that was negotiated at a lower layer. This lack integrity protection that was negotiated at a lower layer. This lack
of a "channel binding" prevents SASL from being able to verify that of a "channel binding" prevents SASL from being able to verify that
the source and destination end points to which the lower layer's the source and destination end points to which the lower layer's
security is bound are equivalent to the end points that SASL is security is bound are equivalent to the end points that SASL is
authenticating. If the end points are not identical, the lower authenticating. If the end points are not identical, the lower
layer's security cannot be trusted to protect data transmitted layer's security cannot be trusted to protect data transmitted
between the SASL authenticated entities. In such a situation, a SASL between the SASL authenticated entities. In such a situation, a SASL
security layer should be negotiated which effectively ignores the security layer should be negotiated that effectively ignores the
presence of the lower layer security. presence of the lower layer security.
14.7 Mandatory-to-Implement Technologies 14.7. Mandatory-to-Implement Technologies
At a minimum, all implementations MUST support the following At a minimum, all implementations MUST support the following
mechanisms: mechanisms:
for authentication: the SASL [DIGEST-MD5] mechanism for authentication: the SASL [DIGEST-MD5] mechanism
for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA for confidentiality: TLS (using the TLS_RSA_WITH_3DES_EDE_CBC_SHA
cipher) cipher)
for both: TLS plus SASL EXTERNAL(using the for both: TLS plus SASL EXTERNAL(using the
TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher supporting client-side
certificates) certificates)
14.8 Firewalls 14.8. Firewalls
Communications using XMPP normally occur over [TCP] connections on Communications using XMPP normally occur over [TCP] connections on
port 5222 (client-to-server) or port 5269 (server-to-server), as port 5222 (client-to-server) or port 5269 (server-to-server), as
registered with the IANA (see IANA Considerations (Section 15)). Use registered with the IANA (see IANA Considerations (Section 15)). Use
of these well-known ports allows administrators to easily enable or of these well-known ports allows administrators to easily enable or
disable XMPP activity through existing and commonly-deployed disable XMPP activity through existing and commonly-deployed
firewalls. firewalls.
14.9 Use of base64 in SASL 14.9. Use of base64 in SASL
Both the client and the server MUST verify any [BASE64] data received Both the client and the server MUST verify any [BASE64] data received
during SASL negotiation. An implementation MUST reject (not ignore) during SASL negotiation. An implementation MUST reject (not ignore)
any characters that are not explicitly allowed by the base64 any characters that are not explicitly allowed by the base64
alphabet; this helps to guard against creation of a covert channel alphabet; this helps to guard against creation of a covert channel
that could be used to "leak" information. An implementation MUST NOT that could be used to "leak" information. An implementation MUST NOT
break on invalid input and MUST reject any sequence of base64 break on invalid input and MUST reject any sequence of base64
characters containing the pad ('=') character if that character is characters containing the pad ('=') character if that character is
included as something other than the last character of the data (e.g. included as something other than the last character of the data
"=AAA" or "BBBB=CCC"); this helps to guard against buffer overflow (e.g., "=AAA" or "BBBB=CCC"); this helps to guard against buffer
attacks and other attacks on the implementation. Base 64 encoding overflow attacks and other attacks on the implementation. Base 64
visually hides otherwise easily recognized information, such as encoding visually hides otherwise easily recognized information, such
passwords, but does not provide any computational confidentiality. as passwords, but does not provide any computational confidentiality.
Base 64 encoding MUST follow the definition in Section 3 of RFC 3548 Base 64 encoding MUST follow the definition in Section 3 of RFC 3548
[BASE64]. [BASE64].
14.10 Stringprep Profiles 14.10. Stringprep Profiles
XMPP makes use of the [NAMEPREP] profile of [STRINGPREP] for XMPP makes use of the [NAMEPREP] profile of [STRINGPREP] for the
processing of domain identifiers; for security considerations related processing of domain identifiers; for security considerations related
to Nameprep, refer to the appropriate section of [NAMEPREP]. to Nameprep, refer to the appropriate section of [NAMEPREP].
In addition, XMPP defines two profiles of [STRINGPREP]: Nodeprep In addition, XMPP defines two profiles of [STRINGPREP]: Nodeprep
(Appendix A) for node identifiers and Resourceprep (Appendix B) for (Appendix A) for node identifiers and Resourceprep (Appendix B) for
resource identifiers. resource identifiers.
The Unicode and ISO/IEC 10646 repertoires have many characters that The Unicode and ISO/IEC 10646 repertoires have many characters that
look similar. In many cases, users of security protocols might do look similar. In many cases, users of security protocols might do
visual matching, such as when comparing the names of trusted third visual matching, such as when comparing the names of trusted third
parties. Because it is impossible to map similar-looking characters parties. Because it is impossible to map similar-looking characters
without a great deal of context such as knowing the fonts used, without a great deal of context, such as knowing the fonts used,
stringprep does nothing to map similar-looking characters together stringprep does nothing to map similar-looking characters together,
nor to prohibit some characters because they look like others. nor to prohibit some characters because they look like others.
A node identifier can be employed as one part of an entity's address A node identifier can be employed as one part of an entity's address
in XMPP. One common usage is as the username of an instant messaging in XMPP. One common usage is as the username of an instant messaging
user; another is as the name of a multi-user chat room; and many user; another is as the name of a multi-user chat room; many other
other kinds of entities could use node identifiers as part of their kinds of entities could use node identifiers as part of their
addresses. The security of such services could be compromised based addresses. The security of such services could be compromised based
on different interpretations of the internationalized node on different interpretations of the internationalized node
identifier; for example, a user entering a single internationalized identifier; for example, a user entering a single internationalized
node identifier could access another user's account information, or a node identifier could access another user's account information, or a
user could gain access to an otherwise restricted chat room or user could gain access to an otherwise restricted chat room or
service. service.
A resource identifier can be employed as one part of an entity's A resource identifier can be employed as one part of an entity's
address in XMPP. One common usage is as the name for an instant address in XMPP. One common usage is as the name for an instant
messaging user's connected resource (active session); another is as messaging user's connected resource (active session); another is as
the nickname of a user in a multi-user chat room; and many other the nickname of a user in a multi-user chat room; many other kinds of
kinds of entities could use resource identifiers as part of their entities could use resource identifiers as part of their addresses.
addresses. The security of such services could be compromised based The security of such services could be compromised based on different
on different interpretations of the internationalized resource interpretations of the internationalized resource identifier; for
identifier; for example, a user could attempt to initiate multiple example, a user could attempt to initiate multiple sessions with the
sessions with the same name, or a user could send a message to same name, or a user could send a message to someone other than the
someone other than the intended recipient in a multi-user chat room. intended recipient in a multi-user chat room.
15. IANA Considerations 15. IANA Considerations
15.1 XML Namespace Name for TLS Data 15.1. XML Namespace Name for TLS Data
A URN sub-namespace for TLS-related data in the Extensible Messaging A URN sub-namespace for TLS-related data in the Extensible Messaging
and Presence Protocol (XMPP) is defined as follows. (This namespace and Presence Protocol (XMPP) is defined as follows. (This namespace
name adheres to the format defined in The IETF XML Registry name adheres to the format defined in The IETF XML Registry
[XML-REG].) [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-tls URI: urn:ietf:params:xml:ns:xmpp-tls
Specification: XXXX Specification: RFC 3920
Description: This is the XML namespace name for TLS-related data in Description: This is the XML namespace name for TLS-related data in
the Extensible Messaging and Presence Protocol (XMPP) as defined the Extensible Messaging and Presence Protocol (XMPP) as defined
by XXXX. by RFC 3920.
Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>
15.2 XML Namespace Name for SASL Data 15.2. XML Namespace Name for SASL Data
A URN sub-namespace for SASL-related data in the Extensible Messaging A URN sub-namespace for SASL-related data in the Extensible Messaging
and Presence Protocol (XMPP) is defined as follows. (This namespace and Presence Protocol (XMPP) is defined as follows. (This namespace
name adheres to the format defined in [XML-REG].) name adheres to the format defined in [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-sasl URI: urn:ietf:params:xml:ns:xmpp-sasl
Specification: XXXX Specification: RFC 3920
Description: This is the XML namespace name for SASL-related data in Description: This is the XML namespace name for SASL-related data in
the Extensible Messaging and Presence Protocol (XMPP) as defined the Extensible Messaging and Presence Protocol (XMPP) as defined
by XXXX. by RFC 3920.
Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>
15.3 XML Namespace Name for Stream Errors 15.3. XML Namespace Name for Stream Errors
A URN sub-namespace for stream-related error data in the Extensible A URN sub-namespace for stream-related error data in the Extensible
Messaging and Presence Protocol (XMPP) is defined as follows. (This Messaging and Presence Protocol (XMPP) is defined as follows. (This
namespace name adheres to the format defined in [XML-REG].) namespace name adheres to the format defined in [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-streams URI: urn:ietf:params:xml:ns:xmpp-streams
Specification: XXXX Specification: RFC 3920
Description: This is the XML namespace name for stream-related error Description: This is the XML namespace name for stream-related error
data in the Extensible Messaging and Presence Protocol (XMPP) as data in the Extensible Messaging and Presence Protocol (XMPP) as
defined by XXXX. defined by RFC 3920.
Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>
15.4 XML Namespace Name for Resource Binding 15.4. XML Namespace Name for Resource Binding
A URN sub-namespace for resource binding in the Extensible Messaging A URN sub-namespace for resource binding in the Extensible Messaging
and Presence Protocol (XMPP) is defined as follows. (This namespace and Presence Protocol (XMPP) is defined as follows. (This namespace
name adheres to the format defined in [XML-REG].) name adheres to the format defined in [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-bind URI: urn:ietf:params:xml:ns:xmpp-bind
Specification: XXXX Specification: RFC 3920
Description: This is the XML namespace name for resource binding in Description: This is the XML namespace name for resource binding in
the Extensible Messaging and Presence Protocol (XMPP) as defined the Extensible Messaging and Presence Protocol (XMPP) as defined
by XXXX. by RFC 3920.
Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>
15.5 XML Namespace Name for Stanza Errors 15.5. XML Namespace Name for Stanza Errors
A URN sub-namespace for stanza-related error data in the Extensible A URN sub-namespace for stanza-related error data in the Extensible
Messaging and Presence Protocol (XMPP) is defined as follows. (This Messaging and Presence Protocol (XMPP) is defined as follows. (This
namespace name adheres to the format defined in [XML-REG].) namespace name adheres to the format defined in [XML-REG].)
URI: urn:ietf:params:xml:ns:xmpp-stanzas URI: urn:ietf:params:xml:ns:xmpp-stanzas
Specification: XXXX Specification: RFC 3920
Description: This is the XML namespace name for stanza-related error Description: This is the XML namespace name for stanza-related error
data in the Extensible Messaging and Presence Protocol (XMPP) as data in the Extensible Messaging and Presence Protocol (XMPP) as
defined by XXXX. defined by RFC 3920.
Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>
15.6 Nodeprep Profile of Stringprep 15.6. Nodeprep Profile of Stringprep
The Nodeprep profile of stringprep is defined under Nodeprep The Nodeprep profile of stringprep is defined under Nodeprep
(Appendix A). The IANA registers Nodeprep in the stringprep profile (Appendix A). The IANA has registered Nodeprep in the stringprep
registry. profile registry.
Name of this profile: Name of this profile:
Nodeprep Nodeprep
RFC in which the profile is defined: RFC in which the profile is defined:
XXXX RFC 3920
Indicator whether or not this is the newest version of the profile: Indicator whether or not this is the newest version of the profile:
This is the first version of Nodeprep This is the first version of Nodeprep
15.7 Resourceprep Profile of Stringprep 15.7. Resourceprep Profile of Stringprep
The Resourceprep profile of stringprep is defined under Resourceprep The Resourceprep profile of stringprep is defined under Resourceprep
(Appendix B). The IANA registers Resourceprep in the stringprep (Appendix B). The IANA has registered Resourceprep in the stringprep
profile registry. profile registry.
Name of this profile: Name of this profile:
Resourceprep Resourceprep
RFC in which the profile is defined: RFC in which the profile is defined:
XXXX RFC 3920
Indicator whether or not this is the newest version of the profile: Indicator whether or not this is the newest version of the profile:
This is the first version of Resourceprep This is the first version of Resourceprep
15.8 GSSAPI Service Name 15.8. GSSAPI Service Name
The IANA registers "xmpp" as a GSSAPI [GSS-API] service name, as The IANA has registered "xmpp" as a GSSAPI [GSS-API] service name, as
defined under SASL Definition (Section 6.3). defined under SASL Definition (Section 6.3).
15.9 Port Numbers 15.9. Port Numbers
The IANA registers "xmpp-client" and "xmpp-server" as keywords for The IANA has registered "xmpp-client" and "xmpp-server" as keywords
[TCP] ports 5222 and 5269 respectively. for [TCP] ports 5222 and 5269 respectively.
These ports SHOULD be used for client-to-server and server-to-server These ports SHOULD be used for client-to-server and server-to-server
communications respectively, but their use is OPTIONAL. communications respectively, but their use is OPTIONAL.
Normative References 16. References
16.1. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data [BASE64] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[CHARSET] Alvestrand, H., "IETF Policy on Character Sets and [CHARSET] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998. Languages", BCP 18, RFC 2277, January 1998.
[DIGEST-MD5] [DIGEST-MD5] Leach, P. and C. Newman, "Using Digest Authentication as
Leach, P. and C. Newman, "Using Digest Authentication as a a SASL Mechanism", RFC 2831, May 2000.
SASL Mechanism", RFC 2831, May 2000.
[DNS] Mockapetris, P., "Domain names - implementation and [DNS] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[GSS-API] Linn, J., "Generic Security Service Application Program [GSS-API] Linn, J., "Generic Security Service Application Program
Interface, Version 2", RFC 2078, January 1997. Interface Version 2, Update 1", RFC 2743, January 2000.
[HTTP-TLS] [HTTP-TLS] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[IDNA] Faltstrom, P., Hoffman, P. and A. Costello, [IDNA] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", "Internationalizing Domain Names in Applications
RFC 3490, March 2003. (IDNA)", RFC 3490, March 2003.
[IPv6] Hinden, R. and S. Deering, "IP Version 6 Addressing [IPv6] Hinden, R. and S. Deering, "Internet Protocol Version 6
Architecture", RFC 2373, July 1998. (IPv6) Addressing Architecture", RFC 3513, April 2003.
[LANGTAGS] [LANGTAGS] Alvestrand, H., "Tags for the Identification of
Alvestrand, H., "Tags for the Identification of
Languages", BCP 47, RFC 3066, January 2001. Languages", BCP 47, RFC 3066, January 2001.
[NAMEPREP] [NAMEPREP] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)", RFC Profile for Internationalized Domain Names (IDN)", RFC
3491, March 2003. 3491, March 2003.
[RANDOM] Eastlake, D., Crocker, S. and J. Schiller, "Randomness [RANDOM] Eastlake 3rd, D., Crocker, S., and J. Schiller,
Recommendations for Security", RFC 1750, December 1994. "Randomness Recommendations for Security", RFC 1750,
December 1994.
[SASL] Myers, J., "Simple Authentication and Security Layer [SASL] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997. (SASL)", RFC 2222, October 1997.
[SRV] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for [SRV] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC
February 2000. 2782, February 2000.
[STRINGPREP] [STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of
Hoffman, P. and M. Blanchet, "Preparation of Internationalized Strings ("stringprep")", RFC 3454,
Internationalized Strings ("STRINGPREP")", RFC 3454,
December 2002. December 2002.
[TCP] Postel, J., "Transmission Control Protocol", STD 7, RFC [TCP] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981. 793, September 1981.
[TERMS] Bradner, S., "Key words for use in RFCs to Indicate [TERMS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[TLS] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. [TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, RFC 2246, January 1999.
January 1999.
[UCS2] International Organization for Standardization, [UCS2] International Organization for Standardization,
"Information Technology - Universal Multiple-octet coded "Information Technology - Universal Multiple-octet coded
Character Set (UCS) - Amendment 2: UCS Transformation Character Set (UCS) - Amendment 2: UCS Transformation
Format 8 (UTF-8)", ISO Standard 10646-1 Addendum 2, Format 8 (UTF-8)", ISO Standard 10646-1 Addendum 2,
October 1996. October 1996.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[X509] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet [X509] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
X.509 Public Key Infrastructure Certificate and X.509 Public Key Infrastructure Certificate and
Certificate Revocation List (CRL) Profile", RFC 3280, Certificate Revocation List (CRL) Profile", RFC 3280,
April 2002. April 2002.
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., and E. Maler,
"Extensible Markup Language (XML) 1.0 (2nd ed)", W3C "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C
REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>. REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>.
[XML-NAMES] [XML-NAMES] Bray, T., Hollander, D., and A. Layman, "Namespaces in
Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C REC-xml-names, January 1999,
XML", W3C REC-xml-names, January 1999, <http://www.w3.org/ <http://www.w3.org/TR/REC-xml-names>.
TR/REC-xml-names>.
Informative References 16.2. Informative References
[ACAP] Newman, C. and J. Myers, "ACAP -- Application [ACAP] Newman, C. and J. Myers, "ACAP -- Application
Configuration Access Protocol", RFC 2244, November 1997. Configuration Access Protocol", RFC 2244, November 1997.
[DNSSEC] Eastlake, D., "Domain Name System Security Extensions", [ASN.1] CCITT, "Recommendation X.208: Specification of Abstract
RFC 2535, March 1999. Syntax Notation One (ASN.1)", 1988.
[DNSSEC] Eastlake 3rd, D., "Domain Name System Security
Extensions", RFC 2535, March 1999.
[HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[IMAP] Crispin, M., "Internet Message Access Protocol - Version [IMAP] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 2060, December 1996. 4rev1", RFC 3501, March 2003.
[IMP-REQS] [IMP-REQS] Day, M., Aggarwal, S., Mohr, G., and J. Vincent,
Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging / "Instant Messaging / Presence Protocol Requirements",
Presence Protocol Requirements", RFC 2779, February 2000. RFC 2779, February 2000.
[IRC] Oikarinen, J. and D. Reed, "Internet Relay Chat Protocol", [IRC] Oikarinen, J. and D. Reed, "Internet Relay Chat
RFC 1459, May 1993. Protocol", RFC 1459, May 1993.
[JSF] Jabber Software Foundation, "Jabber Software Foundation", [JEP-0029] Kaes, C., "Definition of Jabber Identifiers (JIDs)", JSF
<http://www.jabber.org/>. JEP 0029, October 2003.
[POP3] Myers, J. and M. Rose, "Post Office Protocol - Version 3", [JEP-0078] Saint-Andre, P., "Non-SASL Authentication", JSF JEP
STD 53, RFC 1939, May 1996. 0078, July 2004.
[SIMPLE] SIMPLE Working Group, "SIMPLE WG", <http://www.ietf.org/ [JEP-0086] Norris, R. and P. Saint-Andre, "Error Condition
html.charters/simple-charter.html>. Mappings", JSF JEP 0086, February 2004.
[JSF] Jabber Software Foundation, "Jabber Software
Foundation", <http://www.jabber.org/>.
[POP3] Myers, J. and M. Rose, "Post Office Protocol - Version
3", STD 53, RFC 1939, May 1996.
[SIMPLE] SIMPLE Working Group, "SIMPLE WG",
<http://www.ietf.org/html.charters/simple-charter.html>.
[SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, [SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001. April 2001.
[URI] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998. August 1998.
[USINGTLS] [USINGTLS] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
2595, June 1999. 2595, June 1999.
[XML-REG] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [XML-REG] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004. January 2004.
[XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence [XMPP-IM] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", Protocol (XMPP): Instant Messaging and Presence", RFC
draft-ietf-xmpp-im-22 (work in progress), April 2004. 3921, October 2004.
Author's Address
Peter Saint-Andre (editor)
Jabber Software Foundation
EMail: stpeter@jabber.org
Appendix A. Nodeprep Appendix A. Nodeprep
A.1 Introduction A.1. Introduction
This appendix defines the "Nodeprep" profile of [STRINGPREP]. As This appendix defines the "Nodeprep" profile of [STRINGPREP]. As
such, it specifies processing rules that will enable users to enter such, it specifies processing rules that will enable users to enter
internationalized node identifiers in the Extensible Messaging and internationalized node identifiers in the Extensible Messaging and
Presence Protocol (XMPP) and have the highest chance of getting the Presence Protocol (XMPP) and have the highest chance of getting the
content of the strings correct. (An XMPP node identifier is the content of the strings correct. (An XMPP node identifier is the
optional portion of an XMPP address that precedes a domain identifier optional portion of an XMPP address that precedes a domain identifier
and the '@' separator; it is often but not exclusively associated and the '@' separator; it is often but not exclusively associated
with an instant messaging username.) These processing rules are with an instant messaging username.) These processing rules are
intended only for XMPP node identifiers and are not intended for intended only for XMPP node identifiers and are not intended for
skipping to change at page 73, line 6 skipping to change at page 75, line 32
o The intended applicability of the profile: internationalized node o The intended applicability of the profile: internationalized node
identifiers within XMPP identifiers within XMPP
o The character repertoire that is the input and output to o The character repertoire that is the input and output to
stringprep: Unicode 3.2, specified in Section 2 of this Appendix stringprep: Unicode 3.2, specified in Section 2 of this Appendix
o The mappings used: specified in Section 3 o The mappings used: specified in Section 3
o The Unicode normalization used: specified in Section 4 o The Unicode normalization used: specified in Section 4
o The characters that are prohibited as output: specified in Section o The characters that are prohibited as output: specified in Section
5 5
o Bidirectional character handling: specified in Section 6 o Bidirectional character handling: specified in Section 6
A.2 Character Repertoire A.2. Character Repertoire
This profile uses Unicode 3.2 with the list of unassigned code points This profile uses Unicode 3.2 with the list of unassigned code points
being Table A.1, both defined in Appendix A of [STRINGPREP]. being Table A.1, both defined in Appendix A of [STRINGPREP].
A.3 Mapping A.3. Mapping
This profile specifies mapping using the following tables from This profile specifies mapping using the following tables from
[STRINGPREP]: [STRINGPREP]:
Table B.1 Table B.1
Table B.2 Table B.2
A.4 Normalization A.4. Normalization
This profile specifies using Unicode normalization form KC, as This profile specifies the use of Unicode normalization form KC, as
described in [STRINGPREP]. described in [STRINGPREP].
A.5 Prohibited Output A.5. Prohibited Output
This profile specifies prohibiting use of the following tables from This profile specifies the prohibition of using the following tables
[STRINGPREP]. from [STRINGPREP].
Table C.1.1 Table C.1.1
Table C.1.2 Table C.1.2
Table C.2.1 Table C.2.1
Table C.2.2 Table C.2.2
Table C.3 Table C.3
Table C.4 Table C.4
Table C.5 Table C.5
Table C.6 Table C.6
Table C.7 Table C.7
skipping to change at page 74, line 7 skipping to change at page 76, line 33
#x22 (") #x22 (")
#x26 (&) #x26 (&)
#x27 (') #x27 (')
#x2F (/) #x2F (/)
#x3A (:) #x3A (:)
#x3C (<) #x3C (<)
#x3E (>) #x3E (>)
#x40 (@) #x40 (@)
A.6 Bidirectional Characters A.6. Bidirectional Characters
This profile specifies checking bidirectional strings as described in This profile specifies the checking of bidirectional strings, as
Section 6 of [STRINGPREP]. described in Section 6 of [STRINGPREP].
Appendix B. Resourceprep Appendix B. Resourceprep
B.1 Introduction B.1. Introduction
This appendix defines the "Resourceprep" profile of [STRINGPREP]. As This appendix defines the "Resourceprep" profile of [STRINGPREP]. As
such, it specifies processing rules that will enable users to enter such, it specifies processing rules that will enable users to enter
internationalized resource identifiers in the Extensible Messaging internationalized resource identifiers in the Extensible Messaging
and Presence Protocol (XMPP) and have the highest chance of getting and Presence Protocol (XMPP) and have the highest chance of getting
the content of the strings correct. (An XMPP resource identifier is the content of the strings correct. (An XMPP resource identifier is
the optional portion of an XMPP address that follows a domain the optional portion of an XMPP address that follows a domain
identifier and the '/' separator; it is often but not exclusively identifier and the '/' separator; it is often but not exclusively
associated with an instant messaging session name.) These processing associated with an instant messaging session name.) These processing
rules are intended only for XMPP resource identifiers and are not rules are intended only for XMPP resource identifiers and are not
skipping to change at page 74, line 31 skipping to change at page 77, line 9
the optional portion of an XMPP address that follows a domain the optional portion of an XMPP address that follows a domain
identifier and the '/' separator; it is often but not exclusively identifier and the '/' separator; it is often but not exclusively
associated with an instant messaging session name.) These processing associated with an instant messaging session name.) These processing
rules are intended only for XMPP resource identifiers and are not rules are intended only for XMPP resource identifiers and are not
intended for arbitrary text or any other aspect of an XMPP address. intended for arbitrary text or any other aspect of an XMPP address.
This profile defines the following, as required by [STRINGPREP]: This profile defines the following, as required by [STRINGPREP]:
o The intended applicability of the profile: internationalized o The intended applicability of the profile: internationalized
resource identifiers within XMPP resource identifiers within XMPP
o The character repertoire that is the input and output to o The character repertoire that is the input and output to
stringprep: Unicode 3.2, specified in Section 2 of this Appendix stringprep: Unicode 3.2, specified in Section 2 of this Appendix
o The mappings used: specified in Section 3 o The mappings used: specified in Section 3
o The Unicode normalization used: specified in Section 4 o The Unicode normalization used: specified in Section 4
o The characters that are prohibited as output: specified in Section o The characters that are prohibited as output: specified in Section
5 5
o Bidirectional character handling: specified in Section 6 o Bidirectional character handling: specified in Section 6
B.2 Character Repertoire B.2. Character Repertoire
This profile uses Unicode 3.2 with the list of unassigned code points This profile uses Unicode 3.2 with the list of unassigned code points
being Table A.1, both defined in Appendix A of [STRINGPREP]. being Table A.1, both defined in Appendix A of [STRINGPREP].
B.3 Mapping B.3. Mapping
This profile specifies mapping using the following tables from This profile specifies mapping using the following tables from
[STRINGPREP]: [STRINGPREP]:
Table B.1 Table B.1
B.4 Normalization B.4. Normalization
This profile specifies using Unicode normalization form KC, as This profile specifies using Unicode normalization form KC, as
described in [STRINGPREP]. described in [STRINGPREP].
B.5 Prohibited Output B.5. Prohibited Output
This profile specifies prohibiting use of the following tables from This profile specifies prohibiting use of the following tables from
[STRINGPREP]. [STRINGPREP].
Table C.1.2 Table C.1.2
Table C.2.1 Table C.2.1
Table C.2.2 Table C.2.2
Table C.3 Table C.3
Table C.4 Table C.4
Table C.5 Table C.5
Table C.6 Table C.6
Table C.7 Table C.7
Table C.8 Table C.8
Table C.9 Table C.9
B.6 Bidirectional Characters B.6. Bidirectional Characters
This profile specifies checking bidirectional strings as described in This profile specifies checking bidirectional strings as described in
Section 6 of [STRINGPREP]. Section 6 of [STRINGPREP].
Appendix C. XML Schemas Appendix C. XML Schemas
The following XML schemas are descriptive, not normative. For The following XML schemas are descriptive, not normative. For
schemas defining the 'jabber:client' and 'jabber:server' namespaces, schemas defining the 'jabber:client' and 'jabber:server' namespaces,
refer to [XMPP-IM]. refer to [XMPP-IM].
C.1 Streams namespace C.1. Streams namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://etherx.jabber.org/streams' targetNamespace='http://etherx.jabber.org/streams'
xmlns='http://etherx.jabber.org/streams' xmlns='http://etherx.jabber.org/streams'
elementFormDefault='unqualified'> elementFormDefault='unqualified'>
<xs:element name='stream'> <xs:element name='stream'>
skipping to change at page 77, line 15 skipping to change at page 80, line 8
<xs:group ref='err:streamErrorGroup'/> <xs:group ref='err:streamErrorGroup'/>
<xs:element ref='err:text' <xs:element ref='err:text'
minOccurs='0' minOccurs='0'
maxOccurs='1'/> maxOccurs='1'/>
</xs:sequence> </xs:sequence>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
</xs:schema> </xs:schema>
C.2 Stream error namespace C.2. Stream error namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:ietf:params:xml:ns:xmpp-streams' targetNamespace='urn:ietf:params:xml:ns:xmpp-streams'
xmlns='urn:ietf:params:xml:ns:xmpp-streams' xmlns='urn:ietf:params:xml:ns:xmpp-streams'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='bad-format' type='empty'/> <xs:element name='bad-format' type='empty'/>
skipping to change at page 79, line 5 skipping to change at page 81, line 42
</xs:element> </xs:element>
<xs:simpleType name='empty'> <xs:simpleType name='empty'>
<xs:restriction base='xs:string'> <xs:restriction base='xs:string'>
<xs:enumeration value=''/> <xs:enumeration value=''/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:schema> </xs:schema>
C.3 TLS namespace C.3. TLS namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:ietf:params:xml:ns:xmpp-tls' targetNamespace='urn:ietf:params:xml:ns:xmpp-tls'
xmlns='urn:ietf:params:xml:ns:xmpp-tls' xmlns='urn:ietf:params:xml:ns:xmpp-tls'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='starttls'> <xs:element name='starttls'>
<xs:complexType> <xs:complexType>
<xs:sequence> <xs:sequence>
<xs:element <xs:element
name='required' name='required'
minOccurs='0' minOccurs='0'
maxOccurs='1' maxOccurs='1'
type='empty'/> type='empty'/>
</xs:sequence> </xs:sequence>
</xs:complexType> </xs:complexType>
skipping to change at page 79, line 38 skipping to change at page 82, line 27
<xs:element name='failure' type='empty'/> <xs:element name='failure' type='empty'/>
<xs:simpleType name='empty'> <xs:simpleType name='empty'>
<xs:restriction base='xs:string'> <xs:restriction base='xs:string'>
<xs:enumeration value=''/> <xs:enumeration value=''/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:schema> </xs:schema>
C.4 SASL namespace C.4. SASL namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:ietf:params:xml:ns:xmpp-sasl' targetNamespace='urn:ietf:params:xml:ns:xmpp-sasl'
xmlns='urn:ietf:params:xml:ns:xmpp-sasl' xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='mechanisms'> <xs:element name='mechanisms'>
skipping to change at page 80, line 40 skipping to change at page 83, line 29
<xs:element name='aborted' type='empty'/> <xs:element name='aborted' type='empty'/>
<xs:element name='incorrect-encoding' type='empty'/> <xs:element name='incorrect-encoding' type='empty'/>
<xs:element name='invalid-authzid' type='empty'/> <xs:element name='invalid-authzid' type='empty'/>
<xs:element name='invalid-mechanism' type='empty'/> <xs:element name='invalid-mechanism' type='empty'/>
<xs:element name='mechanism-too-weak' type='empty'/> <xs:element name='mechanism-too-weak' type='empty'/>
<xs:element name='not-authorized' type='empty'/> <xs:element name='not-authorized' type='empty'/>
<xs:element name='temporary-auth-failure' type='empty'/> <xs:element name='temporary-auth-failure' type='empty'/>
</xs:choice> </xs:choice>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:simpleType name='empty'> <xs:simpleType name='empty'>
<xs:restriction base='xs:string'> <xs:restriction base='xs:string'>
<xs:enumeration value=''/> <xs:enumeration value=''/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:schema> </xs:schema>
C.5 Resource binding namespace C.5. Resource binding namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:ietf:params:xml:ns:xmpp-bind' targetNamespace='urn:ietf:params:xml:ns:xmpp-bind'
xmlns='urn:ietf:params:xml:ns:xmpp-bind' xmlns='urn:ietf:params:xml:ns:xmpp-bind'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='bind'> <xs:element name='bind'>
<xs:complexType> <xs:complexType>
<xs:choice minOccurs='0' maxOccurs='1'> <xs:choice minOccurs='0' maxOccurs='1'>
<xs:element name='resource' type='xs:string'/> <xs:element name='resource' type='xs:string'/>
<xs:element name='jid' type='xs:string'/> <xs:element name='jid' type='xs:string'/>
</xs:choice> </xs:choice>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
</xs:schema> </xs:schema>
C.6 Dialback namespace C.6. Dialback namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='jabber:server:dialback' targetNamespace='jabber:server:dialback'
xmlns='jabber:server:dialback' xmlns='jabber:server:dialback'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='result'> <xs:element name='result'>
<xs:complexType> <xs:complexType>
<xs:simpleContent> <xs:simpleContent>
<xs:extension base='xs:NMTOKEN'> <xs:extension base='xs:token'>
<xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='from' type='xs:string' use='required'/>
<xs:attribute name='to' type='xs:string' use='required'/> <xs:attribute name='to' type='xs:string' use='required'/>
<xs:attribute name='type' use='optional'> <xs:attribute name='type' use='optional'>
<xs:simpleType> <xs:simpleType>
<xs:restriction base='xs:NCName'> <xs:restriction base='xs:NCName'>
<xs:enumeration value='invalid'/> <xs:enumeration value='invalid'/>
<xs:enumeration value='valid'/> <xs:enumeration value='valid'/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:attribute> </xs:attribute>
</xs:extension> </xs:extension>
</xs:simpleContent> </xs:simpleContent>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
<xs:element name='verify'> <xs:element name='verify'>
<xs:complexType> <xs:complexType>
<xs:simpleContent> <xs:simpleContent>
<xs:extension base='xs:NMTOKEN'> <xs:extension base='xs:token'>
<xs:attribute name='from' type='xs:string' use='required'/> <xs:attribute name='from' type='xs:string' use='required'/>
<xs:attribute name='id' type='xs:NMTOKEN' use='required'/> <xs:attribute name='id' type='xs:NMTOKEN' use='required'/>
<xs:attribute name='to' type='xs:string' use='required'/> <xs:attribute name='to' type='xs:string' use='required'/>
<xs:attribute name='type' use='optional'> <xs:attribute name='type' use='optional'>
<xs:simpleType> <xs:simpleType>
<xs:restriction base='xs:NCName'> <xs:restriction base='xs:NCName'>
<xs:enumeration value='invalid'/> <xs:enumeration value='invalid'/>
<xs:enumeration value='valid'/> <xs:enumeration value='valid'/>
</xs:restriction> </xs:restriction>
</xs:simpleType> </xs:simpleType>
</xs:attribute> </xs:attribute>
</xs:extension> </xs:extension>
</xs:simpleContent> </xs:simpleContent>
</xs:complexType> </xs:complexType>
</xs:element> </xs:element>
</xs:schema> </xs:schema>
C.7 Stanza error namespace C.7. Stanza error namespace
<?xml version='1.0' encoding='UTF-8'?> <?xml version='1.0' encoding='UTF-8'?>
<xs:schema <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:ietf:params:xml:ns:xmpp-stanzas' targetNamespace='urn:ietf:params:xml:ns:xmpp-stanzas'
xmlns='urn:ietf:params:xml:ns:xmpp-stanzas' xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'
elementFormDefault='qualified'> elementFormDefault='qualified'>
<xs:element name='bad-request' type='empty'/> <xs:element name='bad-request' type='empty'/>
skipping to change at page 84, line 24 skipping to change at page 87, line 19
XMPP has been adapted from the protocols originally developed in the XMPP has been adapted from the protocols originally developed in the
Jabber open-source community, which can be thought of as "XMPP 0.9". Jabber open-source community, which can be thought of as "XMPP 0.9".
Because there exists a large installed base of Jabber implementations Because there exists a large installed base of Jabber implementations
and deployments, it may be helpful to specify the key differences and deployments, it may be helpful to specify the key differences
between the relevant Jabber protocols and XMPP in order to expedite between the relevant Jabber protocols and XMPP in order to expedite
and encourage upgrades of those implementations and deployments to and encourage upgrades of those implementations and deployments to
XMPP. This section summarizes the core differences, while the XMPP. This section summarizes the core differences, while the
corresponding section of [XMPP-IM] summarizes the differences that corresponding section of [XMPP-IM] summarizes the differences that
relate specifically to instant messaging and presence applications. relate specifically to instant messaging and presence applications.
D.1 Channel Encryption D.1. Channel Encryption
It was common practice in the Jabber community to use SSL for channel It was common practice in the Jabber community to use SSL for channel
encryption on ports other than 5222 and 5269 (the convention is to encryption on ports other than 5222 and 5269 (the convention is to
use ports 5223 and 5270). XMPP uses TLS over the IANA-registered use ports 5223 and 5270). XMPP uses TLS over the IANA-registered
ports for channel encryption, as defined under Use of TLS (Section 5) ports for channel encryption, as defined under Use of TLS (Section 5)
herein. herein.
D.2 Authentication D.2. Authentication
The client-server authentication protocol developed in the Jabber The client-server authentication protocol developed in the Jabber
community used a basic IQ interaction qualified by the community used a basic IQ interaction qualified by the
'jabber:iq:auth' namespace (documentation of this protocol is 'jabber:iq:auth' namespace (documentation of this protocol is
contained in "JEP-0078: Non-SASL Authentication", published by the contained in [JEP-0078], published by the Jabber Software Foundation
Jabber Software Foundation [JSF]). XMPP uses SASL for [JSF]). XMPP uses SASL for authentication, as defined under Use of
authentication, as defined under Use of SASL (Section 6) herein. SASL (Section 6) herein.
The Jabber community did not develop an authentication protocol for The Jabber community did not develop an authentication protocol for
server-to-server communications, only the Server Dialback (Section 8) server-to-server communications, only the Server Dialback (Section 8)
protocol to prevent server spoofing. XMPP supersedes Server Dialback protocol to prevent server spoofing. XMPP supersedes Server Dialback
with a true server-to-server authentication protocol, as defined with a true server-to-server authentication protocol, as defined
under Use of SASL (Section 6) herein. under Use of SASL (Section 6) herein.
D.3 Resource Binding D.3. Resource Binding
Resource binding in the Jabber community was handled via the Resource binding in the Jabber community was handled via the
'jabber:iq:auth' namespace (which was also used for client 'jabber:iq:auth' namespace (which was also used for client
authentication with a server). XMPP defines a dedicated namespace authentication with a server). XMPP defines a dedicated namespace
for resource binding as well as the ability for a server to generate for resource binding as well as the ability for a server to generate
a resource identifier on behalf of a client, as defined under a resource identifier on behalf of a client, as defined under
Resource Binding (Section 7). Resource Binding (Section 7).
D.4 JID Processing D.4. JID Processing
JID processing was somewhat loosely defined by the Jabber community JID processing was somewhat loosely defined by the Jabber community
(documentation of forbidden characters and case handling is contained (documentation of forbidden characters and case handling is contained
in "JEP-0029: Definition of Jabber Identifiers", published by the in [JEP-0029], published by the Jabber Software Foundation [JSF]).
Jabber Software Foundation [JSF]). XMPP specifies the use of XMPP specifies the use of [NAMEPREP] for domain identifiers and
[NAMEPREP] for domain identifiers and supplements Nameprep with two supplements Nameprep with two additional [STRINGPREP] profiles for
additional [STRINGPREP] profiles for JID processing: Nodeprep JID processing: Nodeprep (Appendix A) for node identifiers and
(Appendix A) for node identifiers and Resourceprep (Appendix B) for Resourceprep (Appendix B) for resource identifiers.
resource identifiers.
D.5 Error Handling D.5. Error Handling
Stream-related errors were handled in the Jabber community via XML Stream-related errors were handled in the Jabber community via XML
character data text in a <stream:error/> element. In XMPP, character data text in a <stream:error/> element. In XMPP,
stream-related errors are handled via an extensible mechanism defined stream-related errors are handled via an extensible mechanism defined
under Stream Errors (Section 4.7) herein. under Stream Errors (Section 4.7) herein.
Stanza-related errors were handled in the Jabber community via Stanza-related errors were handled in the Jabber community via
HTTP-style error codes. In XMPP, stanza-related errors are handled HTTP-style error codes. In XMPP, stanza-related errors are handled
via an extensible mechanism defined under Stanza Errors (Section 9.3) via an extensible mechanism defined under Stanza Errors (Section 9.3)
herein. (Documentation of a mapping between Jabber and XMPP error herein. (Documentation of a mapping between Jabber and XMPP error
handling mechanisms is contained in "JEP-0086: Error Condition handling mechanisms is contained in [JEP-0086], published by the
Mappings", published by the Jabber Software Foundation [JSF].) Jabber Software Foundation [JSF].)
D.6 Internationalization D.6. Internationalization
Although use of UTF-8 has always been standard practice within the Although use of UTF-8 has always been standard practice within the
Jabber community, the community did not define mechanisms for Jabber community, the community did not define mechanisms for
specifying the language of human-readable text provided in XML specifying the language of human-readable text provided in XML
character data. XMPP specifies the use of the 'xml:lang' attribute character data. XMPP specifies the use of the 'xml:lang' attribute
in such contexts, as defined under Stream Attributes (Section 4.4) in such contexts, as defined under Stream Attributes (Section 4.4)
and xml:lang (Section 9.1.5) herein. and xml:lang (Section 9.1.5) herein.
D.7 Stream Version Attribute D.7. Stream Version Attribute
The Jabber community did not include a 'version' attribute in stream The Jabber community did not include a 'version' attribute in stream
headers. XMPP specifies inclusion of that attribute as a way to headers. XMPP specifies inclusion of that attribute as a way to
signal support for the stream features (authentication, encryption, signal support for the stream features (authentication, encryption,
etc.) defined under Version Support (Section 4.4.1) herein. etc.) defined under Version Support (Section 4.4.1) herein.
Intellectual Property Statement Contributors
The IETF takes no position regarding the validity or scope of any Most of the core aspects of the Extensible Messaging and Presence
intellectual property or other rights that might be claimed to Protocol were developed originally within the Jabber open-source
pertain to the implementation or use of the technology described in community in 1999. This community was founded by Jeremie Miller, who
this document or the extent to which any license under such rights released source code for the initial version of the jabber server in
might or might not be available; neither does it represent that it January 1999. Major early contributors to the base protocol also
has made any effort to identify any such rights. Information on the included Ryan Eatmon, Peter Millard, Thomas Muldowney, and Dave
IETF's procedures with respect to rights in standards-track and Smith. Work by the XMPP Working Group has concentrated especially on
standards-related documentation can be found in BCP-11. Copies of security and internationalization; in these areas, protocols for the
claims of rights made available for publication and any assurances of use of TLS and SASL were originally contributed by Rob Norris, and
licenses to be made available, or the result of an attempt made to stringprep profiles were originally contributed by Joe Hildebrand.
obtain a general license or permission for the use of such The error code syntax was suggested by Lisa Dusseault.
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any Acknowledgements
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice Thanks are due to a number of individuals in addition to the
this standard. Please address the information to the IETF Executive contributors listed. Although it is difficult to provide a complete
Director. list, the following individuals were particularly helpful in defining
the protocols or in commenting on the specifications in this memo:
Thomas Charron, Richard Dobson, Sam Hartman, Schuyler Heath, Jonathan
Hogg, Cullen Jennings, Craig Kaes, Jacek Konieczny, Alexey Melnikov,
Keith Minkler, Julian Missig, Pete Resnick, Marshall Rose, Alexey
Shchepin, Jean-Louis Seguineau, Iain Shigeoka, Greg Troxel, and David
Waite. Thanks also to members of the XMPP Working Group and the IETF
community for comments and feedback provided throughout the life of
this memo.
Author's Address
Peter Saint-Andre (editor)
Jabber Software Foundation
EMail: stpeter@jabber.org
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004).
This document and translations of it may be copied and furnished to This document is subject to the rights, licenses and restrictions
others, and derivative works that comment on or otherwise explain it contained in BCP 78, and except as set forth therein, the authors
or assist in its implementation may be prepared, copied, published retain all their rights.
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be This document and the information contained herein are provided on an
revoked by the Internet Society or its successors or assignees. "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/S HE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
This document and the information contained herein is provided on an Intellectual Property
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgment The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the IETF's procedures with respect to rights in IETF Documents can
be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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