XEP-xxxx: JID Prep

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.

Table of Contents

1. Introduction

In order to properly compare and match JIDs, a normalization and prepping step is required by RFC 6122 [1]. The responsibility for such normalization is split between the server and client, where the server is expected to prep any JID slots that it recognizes, particulary those related to stanza routing and roster items. However, the server can not prep JID slots that it does not understand, and so those are left for the client to process.

In some environments (in particular, browser based environments), a client does not have access to the various Unicode and internationalization libraries necessary to properly prep and normalize a JID. For those situations, this protocol defines a way for a client to ask a server to normalize a JID on its behalf.

2. Discovering support

If a server supports JID prep queries, it MUST specify the 'urn:xmpp:jidprep:tmp' feature in its service discovery information features as specified in Service Discovery [2] and the Entity Capabilities profile specified in Entity Capabilities [3].

Example 1. Client checks for support by the server

<iq type="get"
    to="capulet.lit"
    from="juliet@capulet.lit/balcony"
    id="info1">
  <query xmlns="http://jabber.org/protocol/disco#info"/>
</iq>

Example 2. Server advertises support for JID prep queries

<iq type="result"
    to="juliet@capulet.lit/balcony"
    from="capulet.lit"
    id="info1">
  <query xmlns="http://jabber.org/protocol/disco#info">
    ...
    <feature var="urn:xmpp:jidprep:tmp"/>
    ...
  </query>
</iq>

The JID prep service MAY be supported through the use of an external component (Jabber Component Protocol [4]); in which case, the component MUST return an identity of "component/jidprep" in addition to the "urn:xmpp:jidprep:tmp" feature.

Example 3. Server component advertises support for JID prep queries

<iq type="result"
    to="juliet@capulet.lit/balcony"
    from="jidprep.capulet.lit"
    id="info2">
  <query xmlns="http://jabber.org/protocol/disco#info">
    <identity category="component" type="jidprep" />
    ...
    <feature var="urn:xmpp:jidprep:tmp" />
  </query>
</iq>

3. Use Cases

In order to request prepping for a JID, the client sends an <iq/> stanza of type "get" to the server, containing a <jid/> element qualified by the 'urn:xmpp:jidprep:tmp' namespace and whose XML character data is the JID in question:

Example 4. Client requests the server to prep and normalize a JID

<iq type="get"
    to="capulet.lit"
    id="prep1">
  <jid xmlns="urn:xmpp:jidprep:tmp">ROMeo@montague.lit/orchard</jid>
</iq>

The server MUST return either an IQ-result or an IQ-error. When returning an IQ-result, the server sends an <iq/> staza of type='result' containing a <jid/> element qualifed by the 'urn:xmpp:jidprep:tmp' namespace and whose XML character data MUST be the prepped and normalized version of the requested JID:

Example 5. Server responds with the prepped JID

<iq type="result"
    to="juliet@capulet.lit/balcony"
    from="capulet.lit"
    id="prep1">
  <jid xmlns="urn:xmpp:jidprep:tmp">romeo@montague.lit/orchard</jid>
</iq>

If an IQ-error is returned, then it SHOULD specify an error condition of <jid-malformed/> if the given JID could not be processed to a normalized form:

Example 6. Server responds with an error for an invalid JID

<iq type="error"
    to="juliet@capulet.lit/balcony"
    from="capulet.lit"
    id="prep1">
  <jid xmlns="urn:xmpp:jidprep:tmp">romeo@@montague.lit/orchard</jid>
  <error type="modify">
    <jid-malformed xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" />
  </error>
</iq>

4. Implementation Notes

If a client has the ability to perform the prepping and normalization process itself, it SHOULD NOT make a JID prep request to the server.

Upon a successful response, the client SHOULD cache the result, mapping the original JID to the normalized version.

In order to reduce the number of queries made by clients, the server MUST enforce normalization rules for any JID slots understood by the server (e.g. the to and from attributes, roster item JIDs, etc). [5]

5. Security Considerations

As the process for normalizing a JID can be resource intensive, there is a possibility for denial of service attacks. A server MAY rate limit the number of requests to prevent such attacks. Likewise, the server MAY only respond to requests from users that are local to the server.

6. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [7].

7. XMPP Registrar Considerations

    <category>
      <name>component</name>
      <type>
        <name>jidprep</name>
        <desc>
          A server component that offers a JID prepping 
          and normalization service to constrained clients.
        </desc>
        <doc>XEP-XXXX</doc>
      </type>
    </category>

8. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:jidprep:tmp'
    xmlns='urn:xmpp:jidprep:tmp'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='jid'>
    <xs:complexType>
      <xs:simpleContent />
    </xs:complexType>
  </xs:element>

</xs:schema>

Appendices

Appendix A: Document Information

Series: XEP
Number: xxxx
Publisher: XMPP Standards Foundation
Status: ProtoXEP
Type: Standards Track
Version: 0.0.1
Last Updated: 2013-05-08
Approving Body: XMPP Council
Dependencies: XMPP Core, XMPP IM, XEP-0030
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
This document in other formats: XML  PDF

Appendix B: Author Information

Appendix C: Legal Notices

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

END