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327 lines
19 KiB
XML
327 lines
19 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>Privileged Components</title>
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<abstract>This specification provides a way for XMPP components to have a privileged access to entities data</abstract>
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<legal>
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<copyright>This XMPP Extension Protocol is copyright (c) 1999 - 2014 by the XMPP Standards Foundation (XSF).</copyright>
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<permissions>Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.</permissions>
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<warranty>## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##</warranty>
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<liability>In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising out of the use or inability to use the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.</liability>
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<conformance>This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <<link url='http://xmpp.org/extensions/ipr-policy.shtml'>http://xmpp.org/extensions/ipr-policy.shtml</link>> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).</conformance>
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</legal>
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<number>xxxx</number>
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<status>ProtoXEP</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XMPP Core</spec>
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<spec>XEP-0114</spec>
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<spec>XEP-0004</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>NOT_YET_ASSIGNED</shortname>
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<author>
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<firstname>Jérôme</firstname>
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<surname>Poisson</surname>
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<email>goffi@goffi.org</email>
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<jid>goffi@jabber.fr</jid>
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</author>
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<revision>
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<version>0.0.1</version>
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<date>2014-05-09</date>
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<initials>jp</initials>
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<remark><p>First draft.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='intro'>
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<p>XMPP components are used for long through &xep0114;, but are quite limited: they have a restricted access to other entities data, similar to what a client can do. This is sufficient for components like gateways, but very limiting for more complex components like a PubSub service. The goal of this XEP is to allow a component to have a "privileged" status, and access an entity data with the same privileges than the entity itself, that means send and receive IQ stanzas on its behalf.</p>
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<p>Privileged component have numerous advantages, including:</p>
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<ul>
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<li>a step forward in decentralization: it is possible for a component to do tasks which were before reserved to server itself. For example, a privileged pubsub component can offer roster access model</li>
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<li>better integration of component: a gateway can add items to an entity roster itslef</li>
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<li>possibility to overpass a server limitation</li>
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<li>quick development cycle: developers can implement the component they need without waiting for a new server release</li>
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<li>server agnostic</li>
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</ul>
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</section1>
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<section1 topic='Requirements' anchor='reqs'>
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<p>A privileged component can be used in two modes:</p>
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<ul>
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<li><strong>admin</strong> mode, where it is installed by the server administrator</li>
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<li><strong>client</strong> mode, where it can be installed by any user</li>
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</ul>
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<p>In <em>admin</em> mode, the component SHOULD be able to emit IQ stanzas in the same way as any entity, including managing roster or accessing persistent storage</p>
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<p>In <em>client</em> mode, a component MUST have an explicit autorization for any IQ namespace he wants to use. Client MUST be able to check and revoke granted permssions.</p>
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</section1>
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<section1 topic='Glossary' anchor='glossary'>
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<ul>
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<li><strong>Component</strong> — the privileged component.</li>
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<li><strong>Client</strong> — the entity that the component wants to manage.</li>
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</ul>
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</section1>
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<section1 topic='Admin Mode Use Cases' anchor='admin_usecases'>
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<section2 topic='Permission Request Use Case' anchor='admin_perm'>
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<section3 topic='Component request privileged status of admin' anchor='req_status'>
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<p>Once the component is authentified and stream is started as explained in <strong>XEP-0114</strong>, the component can request its privileged status. It do it by sending an IQ stanza with <strong>'urn:xmpp:tmp:privilege:0'</strong> namespace</p>
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<example caption='Component asks for admin privilege'><![CDATA[
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<iq from='pubsub.capulet.net' type='get' id='privilege1'>
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<query xmlns='urn:xmpp:tmp:privilege:0' type='request' privilege='admin'/>
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</iq>
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]]></example>
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</section3>
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<section3 topic='Server Accept Admin Privilege' anchor='accept_status'>
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<p>If the server accept the privileged status (e.g.: admin status specified in configuration), it MUST return empty IQ result stanza:</p>
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<example caption='Server accept admin privilege'><![CDATA[
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<iq from='capulet.net' to='pubsub.capulet.net' type='result' id='privilege1' />
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]]></example>
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</section3>
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<section3 topic='Server Reject Admin Privilege' anchor='reject_status'>
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<p>If the server reject the privileged status, it MUST return a &forbidden; error:</p>
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<example caption='Server reject admin privilege'><![CDATA[
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<iq from='capulet.net' to='pubsub.capulet.net' type='error' id='privilege1'>
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<error type='cancel'>
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<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
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</error>
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</iq>
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]]></example>
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</section3>
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</section2>
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<section2 topic='Privileged Component Send IQ Stanzas' anchor='priv_iq_admin'>
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<p>Sending an IQ stanzas is done by remplacing the &IQ; with a <privilege/> element of namespace <strong>'urn:xmpp:tmp:privilege:0'</strong>, and including it in a global IQ stanza. The <privilege/> element is then similar to the IQ stanza the client would have sent. In the following example, the PubSub service want to know juliet's roster because she own a node with roster access model:</p>
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<example caption='Privileged Component Send A Roster Stanza'><![CDATA[
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<iq from='pubsub.capulet.net' type='get' id='roster1'>
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<privilege xmlns='urn:xmpp:tmp:privilege:0'
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from='juliet@example.com'
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type='get'>
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<query xmlns='jabber:iq:roster'/>
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</privilege>
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</iq>
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]]></example>
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<p>The server then answer normaly, as it would have done with the client entity:</p>
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<example caption='Server Answer To Privileged Component'><![CDATA[
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<iq id='roster1'
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to='pubsub.caputet.net'
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type='result'>
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<query xmlns='jabber:iq:roster' ver='ver7'>
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<item jid='nurse@example.com'/>
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<item jid='romeo@example.net'/>
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</query>
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</iq>
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]]></example>
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<p>In the following example, the sync.capulet.net privileged component want to access client's bookmarks to synchronize them with an online service. It can request the bookmarks in the following way:</p>
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<example caption='Privileged Component Request Bookmarks'><![CDATA[
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<iq from='pubsub.capulet.net' type='get' id='bookmark1'>
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<privilege xmlns='urn:xmpp:tmp:privilege:0'
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from='juliet@capulet.lit'
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type='get'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<items node='storage:bookmarks'/>
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</pubsub>
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</privilege>
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</iq>
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]]></example>
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<p>and server answer:</p>
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<example caption='Server Return Bookmarks'><![CDATA[
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<iq id='bookmark1'
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to='pubsub.caputet.net'
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type='result'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<items node='storage:bookmarks'>
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<item id='current'>
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<storage xmlns='storage:bookmarks'>
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<conference name='The Play's the Thing'
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autojoin='true'
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jid='theplay@conference.shakespeare.lit'>
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<nick>JC</nick>
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</conference>
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</storage>
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</item>
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</items>
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</pubsub>
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</iq>
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]]></example>
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</section2>
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</section1>
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<section1 topic='Client Mode Use Cases' anchor='client_usecases'>
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<section2 topic='Permission Request Use Case' anchor='client_perm'>
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<p>In <em>client</em> mode, the component is not certified by the server administrator, so the permissions MUST be <strong>explicitly</strong> allowed by the client. This is initiated by the component (it can be after an interaction with a client, like a subscription). It's done in a the same way as for <em>admin</em> mode with the following exceptions:</p>
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<ol>
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<li>the privilege type is <em>client</em> instead of <em>admin</em></li>
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<li>the privilege is done per entity, so the entity MUST be specified in a 'to' attribute</li>
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<li>permission are explicitly asked for every needed namespace</li>
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</ol>
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<p>Namespace permission are asked with a <perm/> element, which MUST contain a 'xmlns' attribute and a 'type' attribute which can be:</p>
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<ul>
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<li><strong>get</strong> — the component wants to send &IQ; stanza of type <em>'get'</em></li>
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<li><strong>set</strong> — the component wants to send &IQ; stanza of type <em>'set'</em></li>
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<li><strong>both</strong> — the component wants to send &IQ; stanza of type <em>'get'</em> and <em>'set'</em></li>
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</ul>
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<p>If a component want a read/write access to a client's roster (juliet) and a read only access to her pubsub, it can ask the permission like this:
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</p>
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<example caption='Component Asks For User Privilege'><![CDATA[
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<iq from='priv.montaigu.net' to='capulet.net' type='get' id='privilege1'>
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<query xmlns='urn:xmpp:tmp:privilege:0'
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type='request'
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privilege='client'
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to='juliet@capulet.net'>
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<perm xmlns='jabber:iq:roster' type='both'/>
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<perm xmlns='http://jabber.org/protocol/pubsub' type='get'/>
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</query>
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</iq>
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]]></example>
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<p>Once received the permission request, the server ask to the client if it grant access to the requested permission using &xep0004;. The form SHOULD allow to fine tune the granted permissions. The server use a challenge which it MUST have generated himself.
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</p>
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<example caption='Server Asks User For The Permission'><![CDATA[
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<message from='capulet.net' to='juliet@capulet.net'>
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<body>
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priv.montaigu.net wants some privileges.
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Do you you allow him to use the following features ?
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Be careful ! According permissions to component is a serious thing,
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think twice that you can trust the component before doing this.
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</body>
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<x xmlns='jabber:x:data' type='form'>
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<title>Privileges request</title>
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<instructions>priv.montaigu.net wants to use the following features:
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Do you allow it?</instructions>
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<field type='hidden' var='challenge'><value>5439123</value></field>
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<field type='hidden' var='FORM_TYPE'>
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<value>urn:xmpp:tmp:privilege:0</value>
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</field>
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<field type='list-single'
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label='Manage roster (jabber:iq:roster) READ/WRITE'
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var='jabber:iq:roster'>
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<value>0</value>
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<option label='No'><value>0</value></option>
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<option label='Read only (get)'><value>get</value></option>
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<option label='Write only (set)'><value>set</value></option>
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<option label='Read and write (both)'><value>both</value></option>
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</field>
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<field type='list-single'
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label='Manage PubSub (http://jabber.org/protocol/pubsub) READ'
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var='http://jabber.org/protocol/pubsub'>
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<value>0</value>
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<option label='None'><value>none</value></option>
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<option label='Read only (get)'><value>get</value></option>
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</field>
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</x>
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</message>
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]]></example>
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<p>The server SHOULD include a warning message, SHOULD translate the namespace to human friendly names (and MAY keep the original namespace in addition) and MUST set the default value to '<strong>none</strong>' (permission refused).</p>
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<p>The client can then answer to the form:</p>
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<example caption='Client Answer To The Form'><![CDATA[
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<message from='juliet@capulet.net' to='capulet.net'>
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<x xmlns='jabber:x:data' type='submit'>
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<field var='FORM_TYPE'>
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<value></value>
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</field>
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<field var='challenge'><value>5439123</value></field>
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<field var='jabber:iq:roster'><value>both</value></field>
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<field var='http://jabber.org/protocol/pubsub'><value>none</value></field>
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</x>
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</message>
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]]></example>
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<p>Here juliet accept that <em>priv.montaigu.net</em> use 'set' and 'get' to manage her roster, but doesn't want it to do any 'get' on her pubsub nodes.</p>
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<p>Finaly, the server notify the component of the permission granted. For this it use a &QUERY; element with the 'allowed' type, and put the client jid in a 'from' attribute:</p>
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<example caption='Server notify accepted permissions'><![CDATA[
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<iq from='capulet.net' to='priv.montaigu.net' type='set' id='privilege2'>
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<query xmlns='urn:xmpp:tmp:privilege:0'
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type='allowed'
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from='juliet@capulet.net'>
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<perm xmlns='jabber:iq:roster' type='both'/>
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<perm xmlns='http://jabber.org/protocol/pubsub' type='none'/>
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</query>
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</iq>
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]]></example>
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<p>The privileged component can now act according to permission granted to him.</p>
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</section2>
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<section2 topic='Privileged Component Send IQ Stanzas' anchor='priv_iq_client'>
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<p>sending IQ stanza is done in the exact same way as for <link url='#priv_iq_admin'>admin mode</link>. If a component want to sent a non authorized IQ, it get a &forbidden; error:</p>
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<example caption='Component Request bookmarks'><![CDATA[
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<iq from='priv.montaigu.net' to='capulet.net' type='get' id='bookmark1'>
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<privilege xmlns='urn:xmpp:tmp:privilege:0'
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from='juliet@capulet.lit'
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type='get'>
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<pubsub xmlns='http://jabber.org/protocol/pubsub'>
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<items node='storage:bookmarks'/>
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</pubsub>
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</privilege>
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</iq>
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]]></example>
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<example caption='The Stanza Is Not Autorized !'><![CDATA[
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<iq from='capulet.net' to='priv.montaigu.net' type='error' id='bookmark1'>
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<error type='cancel'>
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<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
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</error>
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</iq>
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]]></example>
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</section2>
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</section1>
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<section1 topic='Discovering Support' anchor='disco'>
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<p>If a server or a component supports the component privilege protocol, it MUST report that fact by including a service discovery feature of "urn:xmpp:tmp:privilege:0" in response to a &xep0030; information request:</p>
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<example caption="Service Discovery information request"><![CDATA[
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<iq from='pubsub.capulet.net'
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id='disco1'
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to='capulet.net'
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type='get'>
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<query xmlns='http://jabber.org/protocol/disco#info'/>
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</iq>
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]]></example>
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<example caption="Service Discovery information response"><![CDATA[
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<iq from='capulet.net'
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id='disco1'
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to='pubsub.capulet.net'
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type='result'>
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<query xmlns='http://jabber.org/protocol/disco#info'>
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...
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<feature var='urn:xmpp:tmp:privilege:0'/>
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...
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</query>
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</iq>
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]]></example>
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</section1>
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<section1 topic='Business Rules' anchor='rules'>
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<ol>
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<li>Server MAY keep permission granted to an component by a client from one session to an other, but if it do so, it MUST provide a way to client to check already granted permission, and revoke them (possibly using &xep0050;).</li>
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<li>If a client can't check or revoke permission (e.g. it doesn't support <strong>XEP-0050</strong>), the server MUST NOT keep granted permission from one session to an other, and permission will be asked on each new session.</li>
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</ol>
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</section1>
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<section1 topic='Implementation Notes' anchor='impl'>
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<p>As admin mode is far more easy to implement than client mode, a server MAY choose to only implement the former</p>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<ol>
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<li>Privileged component nearly have the same possibility as the server itself, <em>admin</em> permission should be granted carefuly, only if you absolutely trust the component.</li>
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<li>A server MAY choose to filter allowed namespaces, to avoid giving dangerous permissions. In this case, it MUST always set the allowed type of filtered namespaces to <strong>none</strong></li>
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<li>In case of filtering, a whitelist system is more secure and SHOULD be prefered to a blacklist (idealy, configuration would allow no filtering, whitelist filtering and blacklist filtering)</li>
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</ol>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>REQUIRED. TODO</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<p>REQUIRED. TODO</p>
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</section1>
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<section1 topic='XML Schema' anchor='schema'>
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<p>REQUIRED for protocol specifications. TODO</p>
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</section1>
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</xep>
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