xeps/xep-0235.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xep SYSTEM 'xep.dtd' [
  <!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
]>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
  <title>Authorization Tokens</title>
  <abstract>This specification defines an XMPP extension for generating, requesting, and using authorization tokens, which can be used to join Multi-User Chat rooms, subscribe to Publish-Subscribe nodes, and even register XMPP accounts.</abstract>
  &LEGALNOTICE;
  <number>0235</number>
  <status>Experimental</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>NOT YET ASSIGNED</shortname>
  &stpeter;
  <revision>
    <version>0.3</version>
    <date>2008-03-31</date>
    <initials>psa</initials>
    <remark><p>Changed data forms usage to semantic XML format (except for in-band registration).</p></remark>
  </revision>
  <revision>
    <version>0.2</version>
    <date>2008-03-27</date>
    <initials>psa</initials>
    <remark><p>Generalized to cover authorization tokens; added use cases for pubsub node subscriptions and XMPP account registration.</p></remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2008-03-05</date>
    <initials>psa</initials>
    <remark><p>Initial published version.</p></remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2008-02-20</date>
    <initials>psa</initials>
    <remark><p>First draft.</p></remark>
  </revision>
</header>
<section1 topic='Introduction' anchor='intro'>
  <p>Although authentication is required in order to access an XMPP network, in some situations it is desirable to require authorization in order to access certain entities on the network. For example, authorization may be required in order to join a &xep0045; room or to subscribe to a &xep0060; node. This document defines a general method for obtaining, sharing, and using authorization tokens over XMPP.</p>
</section1>
<section1 topic='Obtaining an Authorization Token' anchor='obtain'>
  <p>In order to obtain an authorization token that can be sent to a consumer, a user requests an authorization token from the relevant service. For example, let us imagine that the user &lt;crone1@shakespeare.lit&gt; wishes to invite the consumer &lt;hecate@shakespeare.lit&gt; to the chatroom &lt;darkcave@macbeth.shakespeare.lit&gt;. Assuming that the user has already determined that the chatroom supports authorization tokens, the user would send the following request to the room &NSNOTE;.</p>
  <example caption='Token request'><![CDATA[
<iq from='crone1@shakespeare.lit/desktop'
    id='request1'
    to='darkcave@macbeth.shakespeare.lit'
    type='get'>
  <token xmlns='urn:xmpp:tmp:auth-token'
         consumer='xmpp:hecate@shakespeare.lit'/>
</iq>
  ]]></example>
  <p>If the room supports authorization tokens and the user is allowed to invite contacts to the room, the room returns an authorization token to the user.</p>
  <example caption='Token response'><![CDATA[
<iq from='darkcave@macbeth.shakespeare.lit'
    id='request1'
    to='crone1@shakespeare.lit/desktop'
    type='result'>
  <token xmlns='urn:xmpp:tmp:auth-token'
         consumer='xmpp:hecate@shakespeare.lit'
         expires='2007-02-21T23:59:59Z'
         service='darkcave@macbeth.shakespeare.lit'>
    37c69b1cf07a3f67c04a5ef5902fa5114f2c76fe4a2686482ba5b89323075643
  </token>
</iq>
  ]]></example>
  <p>The syntax of the &lt;token/&gt; element is as follows.</p>
  <ul>
    <li>The OPTIONAL 'expires' attribute defines a date and time when the token expires. If included, it MUST be a DateTime as specified in &xep0082;.</li>
    <li>The REQUIRED 'consumer' attribute defines the URI of the entity to be authorized (e.g., an XMPP URI, mailto URI, or HTTP URL).</li>
    <li>The REQUIRED 'service' attribute defines the JabberID of the service for which the consumer is being authorized.</li>
    <li>The OPTIONAL 'node' attribute defines a publish-subscribe node at the service; if the 'node' attribute is included, the authorization MUST be accepted only for interactions with that particular node.</li>
    <li>The XML character data of the &lt;token/&gt; element is the authorization token itself.</li>
  </ul>
</section1>
<section1 topic='Generating an Authorization Token' anchor='generate'>
  <p>A service MAY use any algorithm in generating an authorization token. Depending on implementation and deployment policies, the algorithm MAY take into account the URI of the consumer and be limited to use by an entity that communicates via that URI. Acceptable algorithms MAY include those defined by other standards development organizations, such as &oauth;.</p>
</section1>
<section1 topic='Sharing an Authorization Token' anchor='share'>
  <p>The user can then send the authorization token to the consumer in an XMPP message stanza:</p>
  <example caption='Sharing the authorization token'><![CDATA[
<message from='crone1@shakespeare.lit/desktop' to='hecate@shakespeare.lit'>
  <token xmlns='urn:xmpp:tmp:auth-token'
         consumer='xmpp:hecate@shakespeare.lit'
         expires='2007-02-21T23:59:59Z'
         service='darkcave@macbeth.shakespeare.lit'>
    37c69b1cf07a3f67c04a5ef5902fa5114f2c76fe4a2686482ba5b89323075643
  </token>
</message>
  ]]></example>
</section1>
<section1 topic='Using an Authorization Token' anchor='use'>
  <p>If the consumer wishes to use the token, it MUST first determine the identity of the service (via &xep0030;) so that it can decide how to proceed.</p>
  <p>Note: If the service supports this protocol, it MUST return a service discovery feature of "urn:xmpp:tmp:auth-token" in response to each disco#info request (see the <link url='#support'>Determining Support</link> section of this document).</p>  
  <section2 topic='Multi-User Chat' anchor='use-muc'>
    <p>In this example, the service is a multi-user chat service. If authorization is required in order to join a particular room but the joining entity does not include an authorization token in its join request, the service MUST return an error as follows.</p>
    <example caption='Chatroom join without token'><![CDATA[
<presence from='hecate@shakespeare.lit/broom' to='darkcave@macbeth.shakespeare.lit/Hecate'/>
    ]]></example>
    <example caption='Error from chatroom'><![CDATA[
<presence from='darkcave@macbeth.shakespeare.lit/Hecate'
          to='hecate@shakespeare.lit/broom' 
          type='error'>
  <error type='auth'>
    <not-authorized xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
    <token-required xmlns='urn:xmpp:tmp:auth-token'/>
  </error>
</presence>
    ]]></example>
    <p>The consumer would then include the authorization token in its join request.</p>
  <example caption='Chatroom join with token'><![CDATA[
<presence from='hecate@shakespeare.lit/broom' to='darkcave@macbeth.shakespeare.lit/Hecate'>
  <token xmlns='urn:xmpp:tmp:auth-token'>
    37c69b1cf07a3f67c04a5ef5902fa5114f2c76fe4a2686482ba5b89323075643
  </token>
</presence>
    ]]></example>
    <p>If the token is acceptable, the service will then allow the consumer to enter the room.</p>
    <p>Note: Although <cite>XEP-0045</cite> includes a protocol for inviting a contact to a chatroom, that protocol results in the sending of an invitation from the chatroom to the contact (a "mediated invitation"), not from the inviting user to the contact (a "direct invitation"). Because use of &xep0016; may result in blocking of XML stanzas from entities that are not in the contact's roster, mediated invitations may never be delivered to the contact. Use of authorization tokens as described herein enables a user to directly send an invitation to a contact, thus routing around the blocking of mediated invitations.</p>
  </section2>
  <section2 topic='Publish-Subscribe' anchor='use-pubsub'>
    <p>In this example, the service is a publish-subscribe service. If authorization is required in order to subscribe to a particular node but the subscribing entity does not include an authorization token in its subscribe request, the service MUST return an error as follows.</p>
    <example caption='Subscription request without token'><![CDATA[
<iq type='set'
    from='notify.marlowe.lit'
    to='pubsub.shakespeare.lit'
    id='sub1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <subscribe node='bard_geoloc'/>
  </pubsub>
</iq>
    ]]></example>
    <example caption='Error from node'><![CDATA[
<iq type='error'
    from='pubsub.shakespeare.lit'
    to='notify.marlowe.lit'
    id='sub1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <subscribe node='bard_geoloc'/>
  </pubsub>
  <error type='auth'>
    <not-authorized xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
    <token-required xmlns='urn:xmpp:tmp:auth-token'/>
  </error>
</iq>
    ]]></example>
    <p>The contact would then include the authorization token in its subscription request.</p>
  <example caption='Subscription request with token'><![CDATA[
<iq type='set'
    from='notify.marlowe.lit'
    to='pubsub.shakespeare.lit'
    id='sub1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <subscribe node='bard_geoloc'/>
    <token xmlns='urn:xmpp:tmp:auth-token'>
      37c69b1cf07a3f67c04a5ef5902fa5114f2c76fe4a2686482ba5b89323075643
    </token>
  </pubsub>
</iq>
    ]]></example>
    <p>If the token is acceptable, the service will then allow the consumer to subscribe to the node.</p>
  </section2>
  <section2 topic='Account Registration' anchor='use-register'>
    <p>In this example, the service allows new account registration using &xep0077;. The registering entity SHOULD request the registration form before attempting to register.</p>
    <example caption='Consumer requests registration form'><![CDATA[
<iq type='get'
    to='contests.shakespeare.lit'
    id='reg1'>
  <query xmlns='jabber:iq:register'/>
</iq>
    ]]></example>
    <example caption='Host returns registration form'><![CDATA[
<iq type='result'
    from='contests.shakespeare.lit'
    to='juliet@capulet.com/balcony'
    id='reg1'>
  <query xmlns='jabber:iq:register'>
    <instructions>
      Use the enclosed form to register. If your Jabber client does not
      support Data Forms, visit http://www.shakespeare.lit/contests.php
    </instructions>
    <x xmlns='jabber:x:data' type='form'>
      <title>Contest Registration</title>
      <instructions>
        Please provide the following information
        to sign up for our special contests!
      </instructions>
      <field type='hidden' var='FORM_TYPE'>
        <value>jabber:iq:register</value>
      </field>
      <field type='text-single' label='Given Name' var='first'>
        <required/>
      </field>
      <field type='text-single' label='Family Name' var='last'>
        <required/>
      </field>
      <field type='text-single' label='Email Address' var='email'>
        <required/>
      </field>
      <field type='list-single' label='Gender' var='x-gender'>
        <option label='Male'><value>M</value></option>
        <option label='Female'><value>F</value></option>
      </field>
      <field type='text-single' label='Invitation Token' var='auth-token'>
        <required/>
      </field>
    </x>
  </query>
</iq>
    ]]></example>
    <p>The user then SHOULD return the form:</p>
    <example caption='User Submits Registration Form'><![CDATA[
<iq type='set'
    from='juliet@capulet.com/balcony'
    to='contests.shakespeare.lit'
    id='reg2'>
  <query xmlns='jabber:iq:register'>
    <x xmlns='jabber:x:data' type='submit'>
      <field type='hidden' var='FORM_TYPE'>
        <value>jabber:iq:register</value>
      </field>
      <field type='text-single' label='Given Name' var='first'>
        <value>Juliet</value>
      </field>
      <field type='text-single' label='Family Name' var='last'>
        <value>Capulet</value>
      </field>
      <field type='text-single' label='Email Address' var='email'>
        <value>juliet@capulet.com</value>
      </field>
      <field type='list-single' label='Gender' var='x-gender'>
        <value>F</value>
      </field>
      <field var='auth-token'>
        <value>
          37c69b1cf07a3f67c04a5ef5902fa5114f2c76fe4a2686482ba5b89323075643
        </value>
      </field>
    </x>
  </query>
</iq>
    ]]></example>
    <p>If the token is acceptable, the service will then allow the consumer to register.</p>
  </section2>
</section1>
<section1 topic='Determining Support' anchor='support'>
  <p>If a service provides and accepts authorization tokens, it MUST advertise support for the 'urn:xmpp:tmp:auth-token' namespace in its disco#info replies (if provided) its &xep0115; notations &NSNOTE;.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
  <p>To follow.</p>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
  <p>This document requires no interaction with &IANA;.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
  <section2 topic='Protocol Namespaces' anchor='ns'>
    <p>Until this specification advances to a status of Draft, its associated namespace shall be "urn:xmpp:tmp:auth-token"; upon advancement of this specification, the &REGISTRAR; shall issue a permanent namespace in accordance with the process defined in Section 4 of &xep0053;.</p>
  </section2>
  <section2 topic='Field Standardization' anchor='registrar-formtypes'>
    <p>This specification adds one field to the existing FORM_TYPE for In-Band Registration.</p>
    <section3 topic='jabber:iq:register' anchor='registrar-formtypes-register'>
      <code><![CDATA[
<form_type>
  <name>jabber:iq:register</name>
  <field
      var='auth-token'
      type='text-single'
      label='Authorization token'/>
</form_type>
      ]]></code>
    </section3>
  </section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
  <code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>

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

  <xs:import 
      namespace='jabber:x:data'
      schemaLocation='http://www.xmpp.org/schemas/x-data.xsd'/>

  <xs:element name='token'>
    <xs:complexType>
      <xs:simpleContent>
        <xs:extension base='xs:string'>
          <xs:attribute name='consumer' type='xs:string' use='optional'/>
          <xs:attribute name='expires' type='xs:string' use='optional'/>
          <xs:attribute name='node' type='xs:string' use='optional'/>
          <xs:attribute name='service' type='xs:string' use='optional'/>
        </xs:extension>
      </xs:simpleContent>
    </xs:complexType>
  </xs:element>

  <xs:element name='token-required'>
    <xs:complexType>
      <xs:choice xmlns:xdata='jabber:x:data' minOccurs='0' maxOccurs='1'>
        <xs:element ref='xdata:x'/>
      </xs:choice>
    </xs:complexType>
  </xs:element>

</xs:schema>
  ]]></code>
</section1>
<section1 topic='Acknowledgements' anchor='ack'>
  <p>Thanks to Dave Cridland and Pedro Melo for their suggestions. Aspects of this specification were inspired by &rfc4467;. Some of the terminology in this specification was borrowed from OAuth.</p>
</section1>
</xep>