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<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="fs-memory-realm.html">

  &project;

  <properties>
    <author email="craigmcc@apache.org">Craig McClanahan</author>
    <title>MemoryRealm</title>
    <revision>$Id: fs-memory-realm.xml 918482 2010-03-03 14:21:09Z kkolinko $</revision>
  </properties>

<body>

<section name="Table of Contents">
<toc/>
</section>

<section name="Overview">


  <subsection name="Introduction">

    <p>The purpose of the <strong>MemoryRealm</strong> implementation is to
    provide a mechanism by which Tomcat can acquire information needed
    to authenticate web application users, and define their security roles,
    from a simple text-based configuration file in XML format.  This is
    intended to simplify the initial installation and operation of Tomcat,
    without the complexity of configuring a database or directory server
    based Realm.  It is not intended for production use.</p>

    <p>This specification reflects a combination of functionality that is
    already present in the <code>org.apache.catalina.realm.MemoryRealm</code>
    class, as well as requirements for enhancements that have been
    discussed.  Where appropriate, requirements statements are marked
    <em>[Current]</em> and <em>[Requested]</em> to distinguish them.</p>

    <p>The current status of this functional specification is
    <strong>PROPOSED</strong>.  It has not yet been discussed and
    agreed to on the TOMCAT-DEV mailing list.</p>

  </subsection>


  <subsection name="External Specifications">

    <p>The implementation of this functionality depends on the following
    external specifications:</p>
    <ul>
    <li>None</li>
    </ul>

  </subsection>


  <subsection name="Implementation Requirements">

    <p>The implementation of this functionality shall conform to the
    following requirements:</p>
    <ul>
    <li>Be realized in one or more implementation classes.</li>
    <li>Implement the <code>org.apache.catalina.Realm</code> interface.
        [Current]</li>
    <li>Implement the <code>org.apache.catalina.Lifecycle</code>
        interface.  [Current]</li>
    <li>Subclass the <code>org.apache.catalina.realm.RealmBase</code>
        base class.</li>
    <li>Live in the <code>org.apache.catalina.realm</code> package.
        [Current]</li>
    <li>Support a configurable debugging detail level. [Current]</li>
    <li>Log debugging and operational messages (suitably internationalized)
        via the <code>getContainer().log()</code> method. [Current]</li>
    </ul>

  </subsection>


</section>


<section name="Dependencies">


  <subsection name="Environmental Dependencies">

    <p>The following environmental dependencies must be met in order for
    MemoryRealm to operate correctly:</p>
    <ul>
    <li>The desire to utilize MemoryRealm must be registered in
        <code>$CATALINA_BASE/conf/server.xml</code>, in a
        <code>&lt;Realm&gt;</code> element that is nested inside a
        corresponding <code>&lt;Engine&gt;</code>, <code>&lt;Host&gt;</code>,
        or <code>&lt;Context&gt;</code> element.  (This is already
        included in the default <code>server.xml</code> file.)</li>
    </ul>

  </subsection>


  <subsection name="Container Dependencies">

    <p>Correct operation of MemoryRealm depends on the following
    specific features of the surrounding container:</p>
    <ul>
    <li>Interactions with <code>MemoryRealm</code> will be initiated by
        the appropriate <code>Authenticator</code> implementation, based
        on the login method that is selected.</li>
    <li><code>MemoryRealm</code> must have an XML parser compatible with
        the JAXP/1.1 APIs available to it.  This is normally accomplished
        by placing the corresponding JAR files in directory
        <code>$CATALINA_HOME/lib</code>.</li>
    </ul>

  </subsection>


</section>


<section name="Functionality">


  <subsection name="Overview of Operation">

    <p>The main purpose of <code>MemoryRealm</code> is to allow Catalina to
    authenticate users, and look up the corresponding security roles, from
    the information found in an XML-format configuration file.  The format
    of this file is described below.  When a <code>MemoryRealm</code>
    instance is started, it will read the contents of this XML file and create
    an "in memory database" of all the valid users and their associated
    security roles.</p>

    <p>Each time that Catalina needs to authenticate a user, it will call
    the <code>authenticate()</code> method of this Realm implementation,
    passing the username and password that were specified by the user.  If
    we find the user in the database (and match on the password), we accumulate
    all of the security roles that are defined for this user, and create a
    new <code>GenericPrincipal</code> object to be returned.  If the user
    is not authenticated, we return <code>null</code> instead.  The
    <code>GenericUser</code> object caches the set of security roles that
    were owned by this user at the time of authentication, so that calls to
    <code>isUserInRole()</code> can be answered without going back to the
    database every time.</p>

  </subsection>


  <subsection name="Detailed Functional Requirements">


    <h3>Configurable Properties</h3>

    <p>The implementation shall support the following properties
    that can be configured with JavaBeans property setters:</p>
    <ul>
    <li>Configurable debugging detail level.</li>
    <li>Configurable file pathname (absolute or relative to
        <code>$CATALINA_BASE</code> of the XML file containing our
        defined users.  [<code>conf/tomcat-users.xml</code>].</li>
    </ul>

    <h3>Lifecycle Functionality</h3>

    <p>The following processing must be performed when the <code>start()</code>
    method is called:</p>
    <ul>
    <li>Open and parse the specified XML file.</li>
    <li>Create an in-memory database representation of the XML file
        contents.</li>
    <li><strong>NOTE</strong> - There is no requirement to recognize
        subsequent changes to the contents of the XML file.</li>
    </ul>

    <p>The following processing must be performed when the <code>stop()</code>
    method is called:</p>
    <ul>
    <li>Release object references to the in-memory database representation.</li>
    </ul>


    <h3>Method authenticate() Functionality</h3>

    <p>When <code>authenticate()</code> is called, the following processing
    is required:</p>
    <ul>
    <li>Select the one and only "user" instance from the in-memory database,
        based on matching the specified username.  If there is no such
        instance, return <code>null</code>.</li>
    <li>Authenticate the user by comparing the (possibly encrypted) password
        value that was received against the password presented by the user.
        If there is no match, return <code>null</code>.</li>
    <li>Construct a new instance of class
        <code>org.apache.catalina.realm.GenericPrincipal</code> (if not
        already using this as the internal database representation) that
        contains the authenticated username and a <code>List</code> of the
        security roles associated with this user.</li>
    <li>Return the newly constructed <code>GenericPrincipal</code>.</li>
    </ul>


    <h3>Method hasRole() Functionality</h3>

    <p>When <code>hasRole()</code> is called, the following processing
    is required:</p>
    <ul>
    <li>The <code>principal</code> that is passed as an argument SHOULD
        be one that we returned (instanceof class
        <code>org.apache.catalina.realm.GenericPrincipal</code>, with a
        <code>realm</code> property that is equal to our instance.</li>
    <li>If the passed <code>principal</code> meets these criteria, check
        the specified role against the list returned by
        <code>getRoles()</code>, and return <code>true</code> if the
        specified role is included; otherwise, return <code>false</code>.</li>
    <li>If the passed <code>principal</code> does not meet these criteria,
        return <code>false</code>.</li>
    </ul>

  </subsection>

</section>


<section name="Testable Assertions">

  <p>In addition the the assertions implied by the functionality requirements
  listed above, the following additional assertions shall be tested to
  validate the behavior of <code>MemoryRealm</code>:</p>
  <ul>
  </ul>

</section>


</body>

</document>
