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This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668.
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Copyright (C) The Internet Society (2004).
This document defines a Uniform Resource Identifier (URI) scheme for use in identifying entities that can communicate via the Extensible Messaging and Presence Protocol (XMPP).
1.
Introduction
1.1
Terminology
2.
Description of xmpp: URI Scheme
2.1
Rationale
2.2
Form
2.3
Generation of xmpp: URIs
2.4
Processing of xmpp: URIs
2.5
Internationalization
3.
IANA Registration of xmpp: URI Scheme
3.1
URI scheme name
3.2
URI scheme syntax
3.3
Character encoding considerations
3.4
Intended usage
3.5
Security considerations
3.6
Relevant publications
3.7
Person and email address to contact for further information
3.8
Author/change controller
3.9
Applications and/or protocols which use this URI scheme name
4.
IANA Considerations
5.
Security Considerations
6.
References
6.1
Normative References
6.2
Informative References
§
Author's Address
A.
Revision History
A.1
Changes from draft-saintandre-xmpp-uri-04
A.2
Changes from draft-saintandre-xmpp-uri-03
A.3
Changes from draft-saintandre-xmpp-uri-02
A.4
Changes from draft-saintandre-xmpp-uri-01
A.5
Changes from draft-saintandre-xmpp-uri-00
§
Intellectual Property and Copyright Statements
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The Extensible Messaging and Presence Protocol (XMPP) is a streaming XML technology that enables any two entities on a network to exchange well-defined but extensible XML elements (called "XML stanzas") in close to real time. [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004. specifies that on an XMPP network itself, the address of an XMPP entity MUST NOT be prepended with a Uniform Resource Identifier (URI) scheme (as defined in [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004.). However, many applications external to an XMPP network may need to identify XMPP entities as full URIs; examples are databases that need to store XMPP addresses and non-native user agents (e.g., web browsers and calendaring applications) that provide interfaces to XMPP services. This memo defines an xmpp: URI scheme for use by such applications, and conforms to both the requirements in Registration Procedures for URL Scheme NamesPetke, R. and I. King, Registration Procedures for URL Scheme Names, November 1999.[URL-REG] and the recommendations in Guidelines for new URL SchemesMasinter, L., Alvestrand, H., Zigmond, D. and R. Petke, Guidelines for new URL Schemes, November 1999.[URL-GUIDE].
This document inherits terminology described in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004..
The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, March 1997.[TERMS].
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Many types of application can be built using XMPP. As specified in [XMPP-IM]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence, April 2004., instant messaging and presence applications of XMPP must handle the im: and pres: URI schemes specified by [CPIM]Peterson, J., Common Profile for Instant Messaging (CPIM), August 2004. and [CPP]Peterson, J., Common Profile for Presence (CPP), August 2004.. However, it is appropriate to define an XMPP-specific URI scheme for other applications of XMPP (such as network management, workflow applications, generic publish-subscribe, remote procedure calls, content syndication, gaming, and middleware) since these applications do not implement instant messaging and presence semantics. Therefore, this document defines a generic URI scheme that will enable applications to address as a URI any entity that can communicate via XMPP.
The xmpp: URI format is provided for use by non-native interfaces and applications only, and primarily for the purpose of identification rather than interaction (on the latter distinction, see Section 1.2.2 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004.). In order to ensure interoperability on XMPP networks, when data is routed to an XMPP entity (e.g., when an XMPP address is contained in the 'to' or 'from' attribute of an XML stanza) or an XMPP entity is otherwise identified in standard XMPP protocol elements, the entity MUST be addressed as <[node@]domain[/resource]> (i.e., without a URI scheme), where the "node identifier", "domain identifer", and "resource identifier" portions of an XMPP address conform to the definitions provided in Section 3 of [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004..
(Note: For historical reasons, the term "resource identifier" is used in XMPP to refer to the optional portion of an XMPP address that follows the domain identifier and the "/" separator character; for details, refer to Section 3.4 of [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.. In the terms of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004., the resource identifier portion of an XMPP address can be seen as equivalent to (and indeed maps to) the path component of an xmpp: URI, and therefore is not to be confused with the meanings of "resource" and "identifier" provided in Section 1.1 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004..)
As described in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004., an XMPP address (also known as a "JID") used natively on an XMPP network is a string of Unicode characters that conforms to a certain set of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. profiles and [IDNA]Faltstrom, P., Hoffman, P. and A. Costello, Internationalizing Domain Names in Applications (IDNA), March 2003. restrictions, following a certain set of syntax rules, encoded as [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003.. The form of such an address can be represented using Augmented Backus-Naur Form ([ABNF]Crocker, D. and P. Overell, Augmented BNF for Syntax Specifications: ABNF, November 1997.) as:
[ node "@" ] domain [ "/" resource ]
However, the "node" and "resource" rules rely on distinct profiles of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. and the "domain" rule relies on the concept of an internationalized domain name as described in [IDNA]Faltstrom, P., Hoffman, P. and A. Costello, Internationalizing Domain Names in Applications (IDNA), March 2003.. Furthermore, a URI is allowed to contain [US-ASCII]American National Standards Institute, Coded Character Set - 7-bit American Standard Code for Information Interchange, 1986. characters only, and certain characters are reserved in URIs. Therefore an XMPP address must be properly handled when transformed into an xmpp: URI (see Section 2.3Generation of xmpp: URIs of this memo) and the ABNF syntax needs to be adjusted in order to accurately capture the form of an xmpp: URI as opposed to a native XMPP address.
Using the "unreserved", "pct-encoded", "host", "path-absolute", and "query" rules defined in [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004., the ABNF syntax for an xmpp: URI can be defined as follows:
xmppuri = "xmpp:" [ nodeid "@" ] host [ path-absolute ]
[ "?" query ]
nodeid = *( unreserved / pct-encoded / allowed )
allowed = "!" / "$" / "(" / ")" / "*" / "+" / ";" / "="
The nature of the query component is not specified herein but is reserved for future standardization or application-specific uses that are outside the scope of this memo; however, the encoding of the query component MUST be [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003., converting non-US-ASCII octets to percent-encoded octets as explained below for other components.
Note: While it would have been desirable to re-use the "userinfo" rule from [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004., this was not possible since the "userinfo" rule allows characters that conform to the "sub-delims" rule, but the "&" and "'" characters (which are allowed by the "sub-delims" rule) are disallowed in XMPP node identifiers by the Nodeprep profile of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. as specified in Appendix A of [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004..
As should be obvious from the foregoing, when generating a conformant xmpp: URI from an XMPP address, it is necessary to use consistent methods for transforming an XMPP "node identifier" into a URI "nodeid component", an XMPP "domain identifier" into a URI "host component", and an XMPP "resource identifer" into a URI "path-absolute component"; such methods are described below. Naturally, if the XMPP address exists in a non-UTF-8 form (e.g., having been written on a piece of paper or having been represented internally in a computer program as UTF-16), it MUST first be converted to [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. before the xmpp: URI is generated.
In order to transform an XMPP "node identifier" into a URI "nodeid component", it MUST first be constructed in accordance with the rules specified in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004., including application of the Nodeprep profile of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. (see Appendix A of [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.) and encoding as a [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. string; the [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. encoded characters of the XMPP "node identifier" MUST then be converted into US-ASCII characters, making sure to represent any reserved character and any character that is outside the range of the US-ASCII coded character set as a percent-encoded octet (see Section 2.1 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004.).
In order to transform an XMPP "domain identifier" into a URI "host component", it MUST first be constructed in accordance with the rules specified in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004., including application of the [NAMEPREP]Hoffman, P. and M. Blanchet, Nameprep: A Stringprep Profile for Internationalized Domain Names (IDN), March 2003. profile of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. and encoding as a [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. string; the [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. encoded characters of the XMPP "domain identifier" MUST then be converted into US-ASCII characters, making sure to represent any reserved character and any character that is outside the range of the US-ASCII coded character set as a percent-encoded octet (see Section 2.1 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004.).
In order to transform an XMPP "resource identifier" into a URI "path-absolute component", it MUST first be constructed in accordance with the rules specified in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004., including application of the Resourceprep profile of [STRINGPREP]Hoffman, P. and M. Blanchet, Preparation of Internationalized Strings ("STRINGPREP"), December 2002. (see Appendix B of [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.) and encoding as a [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. string; after prepending the "/" character, the [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. encoded characters of the XMPP "resource identifier" MUST then be converted into US-ASCII characters, making sure to represent any reserved character and any character that is outside the range of the US-ASCII coded character set as a percent-encoded octet (see Section 2.1 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004.).
In order to form an xmpp: URI from the foregoing components, the generating application MUST concatenate:
Consider the following XMPP address:
<jiři@Čechy.example/v Praze>
(Note: The string "ř" stands for the Unicode character LATIN SMALL LETTER R WITH CARON and the string "Č" stands for the Unicode character LATIN CAPITAL LETTER C WITH CARON, following the "XML Notation" used in [IRI]Duerst, M. and M. Suignard, Internationalized Resource Identifiers (IRI), July 2004.. The '<' and '>' characters are not part of the address itself, but are provided to set off the address for legibility. For those who do not read Czech, this example could be Anglicized as "george@czech-lands.example/In Prague".)
In accordance with the process specified above, the generating application would do the following in order to generate a valid xmpp: URI from this address:
The result is this xmpp: URI:
<xmpp:ji%C5%99i@%C4%8Cechy.example/v%20Praze>
As with the generation of an xmpp: URI from an XMPP address, so also with the processing of an xmpp: URI (including the extraction of an XMPP address therefrom): it is necessary to use consistent methods; such methods are described below.
In order to decompose an xmpp: URI, a processing application MUST separate:
In order to reconstruct the XMPP address from the foregoing components, the processing application MUST:
At this point, the processing application would either (1) complete further XMPP handling itself or (2) invoke a helper application to complete XMPP handling; such XMPP handling would most likely consist of the following steps:
Consider the xmpp: URI that resulted from the previous example:
<xmpp:ji%C5%99i@%C4%8Cechy.example/v%20Praze>
In accordance with the process specified above, the processing application would do the following in order to extract the XMPP address from this xmpp: URI:
The result is this XMPP address:
<jiři@Čechy.example/v Praze>
Because XMPP addresses are [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. strings and because the non-US-ASCII octets in XMPP addresses can be easily converted to percent-encoded octets, XMPP addresses are designed to work well with Internationalized Resource Identifiers ([IRI]Duerst, M. and M. Suignard, Internationalized Resource Identifiers (IRI), July 2004.). In particular, with the exception of stringprep verification and the conversion of syntax-relevant US-ASCII characters (e.g., "?"), an XMPP IRI can be constructed directly by prepending "xmpp:" to an XMPP address.
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This section provides the information required to register the xmpp: URI scheme.
xmpp
The syntax for an xmpp: URI is defined below using Augmented Backus-Naur Form as specified by [ABNF]Crocker, D. and P. Overell, Augmented BNF for Syntax Specifications: ABNF, November 1997.. The "unreserved", "pct-encoded", "host", "path-absolute", and "query" rules are defined in [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004..
xmppuri = "xmpp:" [ nodeid "@" ] host [ path-absolute ]
[ "?" query ]
nodeid = *( unreserved / pct-encoded / allowed )
allowed = "!" / "$" / "(" / ")" / "*" / "+" / ";" / "="
Prior to any conversion into a URI, an XMPP address MUST be represented as [UTF-8]Yergeau, F., UTF-8, a transformation format of ISO 10646, November 2003. by the generating application (e.g., by transforming an application's internal representation of the address as a UTF-16 string into a UTF-8 string) in accordance with [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.. The UTF-8 string MUST then be converted into a US-ASCII string in order to be included in a URI; as part of this conversion, non-US-ASCII octets MUST be percent-encoded as described in Section 2.1 of [URI]Berners-Lee, T., Fielding, R. and L. Masinter, Uniform Resource Identifier (URI): Generic Syntax, July 2004..
The xmpp: URI is intended to be used by interfaces to an XMPP network from non-native user agents such as web browsers, as well as by non-native applications that need to address XMPP entities as full URIs.
See Security ConsiderationsSecurity Considerations of XXXX.
[XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.
Peter Saint-Andre [mailto:stpeter@jabber.org]
This scheme is registered under the IETF tree. As such, the IETF maintains change control.
Applications (other than native native XMPP applications) that provide an interface to XMPP services or that need to address XMPP entities as full URIs.
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This document registers a URI scheme. The registration template can be found in Section 3IANA Registration of xmpp: URI Scheme of this document.
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Detailed security considerations for XMPP are given in [XMPP-CORE]Saint-Andre, P., Extensible Messaging and Presence Protocol (XMPP): Core, May 2004.. Providing an interface to XMPP services from non-native applications introduces new security concerns. For example, the ability to interact with XMPP entities via a web browser may expose sensitive information to attacks that are not possible or that are unlikely on a native XMPP network. Due care must be taken in deciding what information is appropriate for representing in xmpp: URIs.
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| Peter Saint-Andre | |
| Jabber Software Foundation | |
| EMail: | stpeter@jabber.org |
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Note to RFC Editor: please remove this entire appendix, and the corresponding entries in the table of contents, prior to publication.
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