xep-0401.xml

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<xep>
<header>
  <title>Ad-hoc Account Invitation Generation</title>
  <abstract>This document defines a protocol and URI scheme for user invitation in order to allow a third party to register on a server. The goal of this is to make onboarding for XMPP IM newcomers as easy as possible.</abstract>
  &LEGALNOTICE;
  <number>0401</number>
  <status>Proposed</status>
  <lastcall>2021-10-20</lastcall>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XEP-0001</spec>
    <spec>XEP-0050</spec>
    <spec>XEP-0082</spec>
    <spec>XEP-0077</spec>
    <spec>XEP-0147</spec>
    <spec>XEP-0379</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>N/A</shortname>
  <author>
    <firstname>Marc</firstname>
    <surname>Schink</surname>
  </author>
  <author>
    <firstname>Georg</firstname>
    <surname>Lukas</surname>
  </author>
  <revision>
    <version>0.5.0</version>
    <date>2021-10-06</date>
    <initials>gl</initials>
    <remark>Factor out XEP-0445</remark>
  </revision>
  <revision>
    <version>0.4.0</version>
    <date>2020-01-08</date>
    <initials>jsc</initials>
    <remark>Revert version 0.3.0, which was merged prematurely and incorrectly.</remark>
  </revision>
  <revision>
    <version>0.3.0</version>
    <date>2020-01-02</date>
    <initials>gl</initials>
    <remark>Use pre-auth-IQ instead of re-using IBR as per council feedback.</remark>
  </revision>
  <revision>
    <version>0.2.0</version>
    <date>2018-02-11</date>
    <initials>ms</initials>
    <remark>
      <p>Used Data Forms for extension of In-Band Registration as required by <strong>XEP-0077</strong> § 4.</p>
      <p>Added "defined condition" elements in error stanzas as required by <strong>RFC 6120</strong> § 8.3.2.</p>
      <p>Changed type of "invalid-token" error to "modify".</p>
      <p>Fix namespacing of Ad-Hoc commands</p>
      <p>Bump namespace to invite:1</p>
    </remark>
  </revision>
  <revision>
    <version>0.1.0</version>
    <date>2018-01-25</date>
    <initials>XEP Editor (jwi)</initials>
    <remark>Accepted by vote of Council on 2018-01-17.</remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2018-01-10</date>
    <initials>ms</initials>
    <remark><p>First submission.</p></remark>
  </revision>
</header>
<section1 topic='Introduction' anchor='intro'>
  <p>Romeo is an active XMPP IM (Instant Messaging) user or the operator of
    an XMPP server. He convinces Juliet (who may not have an XMPP account yet)
    to install a client but she may still need to choose an XMPP server,
    create an account, and add Romeo as a contact.
    This specification defines two ways for Romeo to simplify this process for Juliet:</p>
  <section2 topic='User Invitation'>
    <p>If Romeo is an XMPP user, he can create an out-of-band link (URI)
      which allows Juliet to:</p>
    <ol>
      <li>Download an XMPP client (if needed).</li>
      <li>Optionally register an account with Romeo's server (if permitted by
	the server rules), or with a public server.</li>
      <li>Establish a mutual presence subscription between Romeo and Juliet.</li>
    </ol>
    <p>The process is designed to automatically skip steps that Juliet already
      completed, to make the overall experience as smooth as possible.</p>
  </section2>
  <section2 topic='Account Creation'>
    <p>If Romeo is an administrator of an XMPP server, he can create an
      out-of-band link (URI) which allows Juliet to:</p>
    <ol>
      <li>Download an XMPP client (if needed).</li>
      <li>Register an account on Romeo's server (with a user name pre-defined
	by Romeo or chosen by Juliet, and a password not known to Romeo).</li>
      <li>Establish a mutual presence subscription between Romeo and Juliet.</li>
    </ol>
  </section2>
</section1>
<section1 topic='Requirements' anchor='reqs'>
  <p>This specification makes use of XMPP URIs. The basic URI scheme for XMPP
    is defined in &rfc5122; and extended in &xep0147; and &xep0379;.
    Furthermore, this heavily builds upon the blocks provided in
    <cite>XEP-0379</cite> for landing page and roster subscription.
  </p>
  <p>
    To create out-of-band invitation links, Romeo's server needs to implement
    the &xep0050; commands specified in the following section, and his client
    must be able to execute them.
  </p>
  <p>
    Furthermore, Romeo's server SHOULD provide a HTTPS service hosting the
    landing page.
  </p>
  <p>Romeo's server MUST support at least one <link url="#preauth-ibr">Pre-Authenticated In-Band
    Registration</link> mechanism.</p>
</section1>
<section1 topic='Discovery' anchor='discover'>
  <p>Romeo can query his server for the availability of "User Invitation" and
  "Account Creation" commands:</p>
  <example caption="Discover available ad-hoc commands"><![CDATA[
<iq type='get' from='romeo@example.com' to='example.com' id='disco'>
  <query xmlns='http://jabber.org/protocol/disco#items'
         node='http://jabber.org/protocol/commands'/>
</iq>
]]></example>
  <p>TODO: use appropriate node namespace.</p>
  <example caption="Discovery result for available ad-hoc commands"><![CDATA[
<iq type='result' to='romeo@example.com' from='example.com' id='disco'>
  <query xmlns='http://jabber.org/protocol/disco#items'
         node='http://jabber.org/protocol/commands'>
    <item jid='example.com'
          node='urn:xmpp:invite#invite'
          name='Invite user'/>
    <item jid='example.com'
          node='urn:xmpp:invite#create-account'
          name='Create account'/>
  </query>
</iq>
]]></example>
</section1>
<section1 topic='Glossary' anchor='glossary'>
  <p>OPTIONAL.</p>
</section1>
<section1 topic='Use Cases' anchor='usecases'>
  <section2 topic='Creating a User Invitation' anchor='create-invitation'>
    <p>A user can execute the 'invite' command to obtain a new invitation link
      with a unique invitation token.</p>
    <example caption="Execute user invitation command"><![CDATA[
<iq type='set' from='romeo@example.com' to='example.com' id='exec1'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:invite#invite'
           action='execute'/>
</iq>
]]></example>
    <example caption="User invitation finished"><![CDATA[
<iq type='result' to='romeo@example.com' from='example.com' id='exec2'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:invite#invite'
           status='completed'>
    <x xmlns='jabber:x:data' type='result'>
      <item>
        <field var='uri'>
          <value>xmpp:inviter@example.com?roster;preauth=TOKEN;ibr=y</value>
        </field>
        <field var='landing-url'>
          <value>https://example.com/invite/#TOKEN</value>
        </field>
        <field var='expire'>
          <value>2017-11-06T02:56:15Z</value>
        </field>
      </item>
    </x>
  </command>
</iq>
]]></example>
    <p>The token should be unique, sufficiently
    long and generated by a strong random number generator.</p>
  <p>A server MUST provide the <strong>uri</strong> field which contains an
    XMPP URI of the following format:</p>
  <code>xmpp:inviter@example.com?roster;preauth=TOKEN;ibr=y</code>
  <p>The <strong>ibr</strong> query component in the XMPP URI indicates that
    the invitee is allowed to create an account on Romeo's server, using the
    'preauth' token.
    If the server does not support or allow in-band registration for invited
    users, the server MUST omit the <strong>ibr</strong> query component.</p>
  <p>Additionally, the server SHOULD provide the <strong>landing-url</strong>
    field which contains an HTTPS URL of a web-based landing page as described
    in &xep0379; § 3.3. The URL format may differ from the example shown here
    depending on where the landing page is hosted.</p>
  <p>If the server omits the <strong>landing-page</strong> field, Romeo's
    client SHOULD generate an appropriate landing page URL hosted by the
    client developer or a trusted third party.</p>
  <p>A server MAY provide a field which provides the expiration date of the
    generated token. The expiration date MUST conform to the DateTime profile
    specified in &xep0082;. If the field is not provided, the token does not
    expire.</p>
  <p>Romeo's client should provide adequate means to export the
    <strong>landing-page</strong> URL, possibly accompanied with a short
    description and the <strong>expire</strong> information, so that Romeo can
    share it with Juliet by other means than XMPP, like e-mail or a QR code.</p>
  </section2>
  <section2 topic='Landing Page' anchor='landing-page'>
    <p>The landing page that the generated URL points to should correspond to
      the format described in <cite>XEP-0379</cite> §3.3, and it needs to
      convey the following information:</p>
    <ul>
      <li>A short text that this is an XMPP invitation from Romeo.</li>
      <li>A client recommendation (based on the detected web browser/OS) with download links.</li>
      <li>A prominent button that activates the encoded <strong>xmpp:</strong> link.</li>
    </ul>
    <p>If the landing page is hosted by Romeo's server, the server MAY display
      additional information based on the supplied TOKEN value, like the name
      of the inviter or validity information.</p>
  </section2>
  <section2 topic='Redeeming a User Invitation' anchor='redeem-invitation'>
    <p>If Juliet does not have an XMPP client installed, she will not be able
      to open the <strong>xmpp:</strong> link from the invitation page.
      For this case, the landing page needs to indicate that a client must be
      installed first, and that the link will not work as intended without.
      The automatic installation of an appropriate IM client when a user
      clicks on an <strong>xmpp:</strong> is outside of the scope of this
      document.</p>
    <p>With an XMPP client installed, Juliet can open the
      <strong>xmpp:</strong> link and have the client process it
      appropriately, as follows:</p>
    <section3 topic='Pre-Configured Account' anchor='redeem-preconfigured'>
      <p>If Juliet's client is already configured with an account, the default
	action for the presented
	<strong>xmpp:inviter@example.com?roster;...</strong> URI is to add the
	inviter to Juliet's roster. This should be performed as described in
	§3.4 of <cite>XEP-0379</cite>, by sending a presence subscription
	request containing the 'preauth' token.</p>
      <p>If Juliet already has Romeo in her roster, her client should open the
	appropriate chat interface instead.</p>
    </section3>
    <section3 topic='No Configured Account' anchor='redeem-no-account'>
      <p>If Juliet's client does not have an XMPP account configured, she
	needs to login or register an account first. Therefore, the client
	should provide an interface with the following options:</p>
      <ul>
	<li>Login with an existing XMPP account.</li>
	<li>Register an account with Romeo's server (if the URI contains a
	  <strong>ibr=y</strong> parameter).</li>
	<li>Register an account with a public or client-endorsed server.</li>
      </ul>
      <p>If the <strong>xmpp:</strong> URI provided by Romeo contains the
	<strong>ibr=y</strong> parameter, it indicates that the server
	supports the <link url="#preauth-ibr">Pre-Authenticated In-Band
	Registration</link> defined in this document. If Juliet chooses this
	approach, the server will ensure that after the registration, Romeo is
	added to her roster with a full presence subscription.</p> <p>If
	Juliet chooses to login or register with a different server, her
	client must complete the respective process and issue a subscription
	request as described in §3.4 of <cite>XEP-0379</cite>.</p>
    </section3>
    </section2>
  <section2 topic='Initiating Account Creation' anchor='account-creation'>
    <p>If Romeo is the administrator of an XMPP server, he might want to
      ensure that Juliet obtains an account on this server, with a username
      defined either by Romeo or by Juliet, and in a way that does not require
      the out-of-band communication of user passwords.</p>
    <p>TODO: description of overall process steps, design motivation.</p>
    <example caption="Exceute account creation command"><![CDATA[
<iq type='set' from='romeo@example.com' to='example.com' id='exec1'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:invite#create-account'
           action='execute'/>
</iq>
]]></example>
    <example caption="Service returns form for account creation"><![CDATA[
<iq type='result' to='romeo@example.com' from='example.com' id='exec1'>
  <command xmlns='http://jabber.org/protocol/commands'
           sessionid='config:20020923T213616Z-700'
           node='urn:xmpp:invite#create-account'
           status='executing'>
    <actions execute='complete'>
      <complete/>
    </actions>
    <x xmlns='jabber:x:data' type='form'>
      <field var='username' label='Username' type='text-single'/>
      <field var='roster-subscription' label='Roster subscription' type='boolean'/>
    </x>
  </command>
</iq>
]]></example>
    <p>A server MAY require a username to be specified for account creation.
      In this case, the server MUST add the &lt;required/&gt; element to the
      username field.
      The username MUST be a valid localpart as defined in &rfc6122; §2.3.</p>
    <example caption="Account creation with specified username"><![CDATA[
<iq type='set' from='romeo@example.com' to='example.com' id='exec2'>
  <command xmlns='http://jabber.org/protocol/commands'
           sessionid='config:20020923T213616Z-700'
           node='urn:xmpp:invite#create-account'>
    <x xmlns='jabber:x:data' type='submit'>
      <field var='username'>
        <value>juliet</value>
      </field>
    </x>
  </command>
</iq>
]]></example>
    <example caption="Account creation finished"><![CDATA[
<iq type='result' to='romeo@example.com' from='example.com' id='exec2'>
  <command xmlns='http://jabber.org/protocol/commands'
           sessionid='config:20020923T213616Z-700'
           node='urn:xmpp:invite#create-account'
           status='completed'>
    <x xmlns='jabber:x:data' type='result'>
      <item>
        <field var='uri'>
          <value>xmpp:juliet@example.com?register;preauth=TOKEN</value>
        </field>
        <field var='landing-url'>
          <value>https://example.com/invite/#TOKEN</value>
        </field>
        <field var='expire'>
          <value>2017-11-06T02:56:15Z</value>
        </field>
      </item>
    </x>
  </command>
</iq>
]]></example>
    <p>The server's response for account creation is the same as for user
      invitation except for the format of the <strong>uri</strong> field which
      contains an XMPP URI of the following format:</p>
    <code>xmpp:juliet@example.com?register;preauth=TOKEN</code>
    <p>If no username was specified during the account creation process, the
      local part of the JID in the XMPP URI is omitted by the server which
      results in the following format:</p>
    <code>xmpp:example.com?register;preauth=TOKEN</code>
    <p>TODO: note about sensitivity of TOKEN</p>
  </section2>
  <section2 topic='Pre-Authenticated In-Band Registration' anchor='preauth-ibr'>
    <p>In order to allow invited users to register on a server, the
      server must support pre-authenticated in-band registration based on one
      of the following specifications:
    </p>
    <ul>
      <li>&xep0445;</li>
      <li>TODO: define a mechanism based on &xep0389;</li>
    </ul>
    <p>
      The invited user's client needs to connect to the server, check which of
      the above mechanisms are supported, and continue as specified in the
      respective document.
    </p>
    <p>After the invitee has successfully registered on the inviter's server
      and roster subscription is enabled for account creation, the server MUST
      use roster pushes as defined in &rfc6121; §2.1.6 in order to inform the
      inviter about the invitee's new account without the need to reconnect.</p>
    <example caption="Push roster item of invitee to inviter"><![CDATA[
<iq type='set' from='romeo@example.com' id='push'>
  <query xmlns='jabber:iq:roster'>
    <item subscription='both' jid='juliet@example.com'/>
  </query>
</iq>
]]></example>
  </section2>
</section1>
<section1 topic='Business Rules' anchor='rules'>
  <section2 topic='Fallback to Client-Side PARS'>
    <p>If the inviter's server does not support user invitation, the client
      application SHOULD silently fall back to &xep0379; for a good user
      experience.</p>
  </section2>
  <section2 topic='Account Creation'>
    <p>If a username was specified during the account creation process, the
      server SHOULD NOT create an account on the server until the invitee
      actually registers it with the corresponding token.
      The server MUST reserve the username at least until the corresponding
      token expires.</p>
  </section2>
</section1>
<section1 topic='Implementation Notes' anchor='impl'>
  <section2 topic='XMPP Server Suggestion for Invitees'>
    <p>If the invitee opens an invitation URI with <strong>ibr=y</strong> and
      chooses to create a new account, the client SHOULD pre-fill the
      inviter JID's domain part as the new account's domain. The client MAY
      provide a mechanism to enter or choose a different server, though.</p>
  </section2>
</section1>
<section1 topic='Accessibility Considerations' anchor='access'>
  <p>OPTIONAL.</p>
</section1>
<section1 topic='Internationalization Considerations' anchor='i18n'>
  <p>OPTIONAL.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
  <p>See security considerations in &xep0379;.</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'>
    <p>As authorized by &xep0147;, the XMPP Registrar maintains a registry of
      queries and key-value pairs for use in XMPP URIs (see &QUERYTYPES;).</p>
    <p>The key-value parameter <strong>preauth</strong> is added to the
      <strong>register</strong> query action as defined in &xep0077;</p>
    <code><![CDATA[
<querytype>
  <name>register</name>
    ...
    <key>
      <name>preauth</name>
      <desc>the token used to allow one-time in-band registration on the inviter's server</desc>
    </key>
</querytype>
]]></code>

    <p>In addition to the <strong>preauth</strong> key-value parameter define
      in &xep0379;, the <strong>ibr</strong> parameter is added to the
      <strong>roster</strong> query action.</p>
    <code><![CDATA[
<querytype>
  <name>roster</name>
    ...
    <key>
      <name>ibr</name>
      <value>y</value>
      <desc>the parameter to indicate that the token allows the invitee to create an account on the inviter's server via in-band registration</desc>
    </key>
</querytype>
]]></code>
</section1>
<section1 topic='XML Schema' anchor='schema'>
  <p>REQUIRED for protocol specifications.</p>
</section1>
</xep>