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

  &project;

  <properties>
    <author email="craigmcc@apache.org">Craig R. McClanahan</author>
    <title>The Realm Component</title>
  </properties>

<body>

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

<section name="Introduction">

  <p>A <strong>Realm</strong> element represents a "database" of usernames,
  passwords, and <em>roles</em> (similar to Unix <em>groups</em>) assigned
  to those users.  Different implementations of Realm allow Catalina to be
  integrated into environments where such authentication information is already
  being created and maintained, and then utilize that information to implement
  <em>Container Managed Security</em> as described in the Servlet
  Specification.</p>

  <p>You may nest a Realm inside any Catalina container
  <a href="engine.html">Engine</a>, <a href="host.html">Host</a>, or
  <a href="context.html">Context</a>).  In addition, Realms associated with
  an Engine or a Host are automatically inherited by lower-level
  containers, unless explicitly overridden.</p>

  <p>For more in-depth information about container managed security in web
  applications, as well as more information on configuring and using the 
  standard realm component implementations, please see the 
  <a href="../realm-howto.html">Container-Managed Security Guide</a>.
  </p>

    <blockquote><em>
    <p>The description below uses the variable name $CATALINA_BASE to refer the
    base directory against which most relative paths are resolved. If you have
    not configured Tomcat 6 for multiple instances by setting a CATALINA_BASE
    directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
    the directory into which you have installed Tomcat 6.</p>
    </em></blockquote>

</section>


<section name="Attributes">

  <subsection name="Common Attributes">

    <p>All implementations of <strong>Realm</strong>
    support the following attributes:</p>

    <attributes>

      <attribute name="className" required="true">
        <p>Java class name of the implementation to use.  This class must
        implement the <code>org.apache.catalina.Realm</code> interface.</p>
      </attribute>

    </attributes>

  </subsection>


  <subsection name="Standard Implementation">

    <p>Unlike most Catalina components, there are several standard
    <strong>Realm</strong> implementations available.  As a result,
    the <code>className</code> attribute MUST be used to select the
    implementation you wish to use.</p>

    <h3>JDBC Database Realm (org.apache.catalina.realm.JDBCRealm)</h3>

    <p>The <strong>JDBC Database Realm</strong> connects Catalina to
    a relational database, accessed through an appropriate JDBC driver,
    to perform lookups of usernames, passwords, and their associated
    roles.  Because the lookup is done each time that it is required,
    changes to the database will be immediately reflected in the
    information used to authenticate new logins.</p>

    <p>A rich set of additional attributes lets you configure the required
    connection to the underlying database, as well as the table and
    column names used to retrieve the required information:</p>

    <attributes>

      <attribute name="connectionName" required="true">
        <p>The database username to use when establishing the JDBC
        connection.</p>
      </attribute>

      <attribute name="connectionPassword" required="true">
        <p>The database password to use when establishing the JDBC
        connection.</p>
      </attribute>

      <attribute name="connectionURL" required="true">
        <p>The connection URL to be passed to the JDBC driver when
        establishing a database connection.</p>
      </attribute>

      <attribute name="digest" required="false">
        <p>The name of the <code>MessageDigest</code> algorithm used
        to encode user passwords stored in the database.  If not specified,
        user passwords are assumed to be stored in clear-text.</p>
      </attribute>
   
      <attribute name="digestEncoding" required="false">
        <p>The charset for encoding digests.  If not specified, the platform
        default will be used.</p>
      </attribute>

      <attribute name="driverName" required="true">
        <p>Fully qualified Java class name of the JDBC driver to be
        used to connect to the authentication database.</p>
      </attribute>

      <attribute name="roleNameCol" required="true">
        <p>Name of the column, in the "user roles" table, which contains
        a role name assigned to the corresponding user.</p>
      </attribute>

      <attribute name="userCredCol" required="true">
        <p>Name of the column, in the "users" table, which contains
        the user's credentials (i.e. password(.  If a value for the
        <code>digest</code> attribute is specified, this component
        will assume that the passwords have been encoded with the
        specified algorithm.  Otherwise, they will be assumed to be
        in clear text.</p>
      </attribute>

      <attribute name="userNameCol" required="true">
        <p>Name of the column, in the "users" and "user roles" table,
        that contains the user's username.</p>
      </attribute>

      <attribute name="userRoleTable" required="true">
        <p>Name of the "user roles" table, which must contain columns
        named by the <code>userNameCol</code> and <code>roleNameCol</code>
        attributes.</p>
      </attribute>

      <attribute name="userTable" required="true">
        <p>Name of the "users" table, which must contain columns named
        by the <code>userNameCol</code> and <code>userCredCol</code>
        attributes.</p>
      </attribute>

    </attributes>

    <p>See the <a href="../realm-howto.html">Container-Managed Security Guide</a> for more
    information on setting up container managed security using the
    JDBC Database Realm component.</p>


    <h3>
      DataSource Database Realm (org.apache.catalina.realm.DataSourceRealm)
    </h3>

    <p>The <strong>DataSource Database Realm</strong> connects Catalina to
    a relational database, accessed through a JNDI named JDBC DataSource
    to perform lookups of usernames, passwords, and their associated
    roles.  Because the lookup is done each time that it is required,
    changes to the database will be immediately reflected in the
    information used to authenticate new logins.</p>

    <p>The JDBC Realm uses a single db connection. This requires that
    realm based authentication be synchronized, i.e. only one authentication
    can be done at a time. This could be a bottleneck for applications
    with high volumes of realm based authentications.</p>

    <p>The DataSource Database Realm supports simultaneous realm based
    authentications and allows the underlying JDBC DataSource to
    handle optimizations like database connection pooling.</p>

    <p>A rich set of additional attributes lets you configure the name
    of the JNDI JDBC DataSource, as well as the table and
    column names used to retrieve the required information:</p>

    <attributes>

      <attribute name="dataSourceName" required="true">
        <p>The name of the JNDI JDBC DataSource for this Realm.</p>
      </attribute>

      <attribute name="digest" required="false">
        <p>The name of the <code>MessageDigest</code> algorithm used
        to encode user passwords stored in the database.  If not specified,
        user passwords are assumed to be stored in clear-text.</p>
      </attribute>

      <attribute name="localDataSource" required="false">
        <p>When the realm is nested inside a Context element, this allows the 
        realm to use a DataSource defined for the Context rather than a global
        DataSource.  If not specified, the default is <code>false</code>: use a 
        global DataSource.</p>
      </attribute>
    
      <attribute name="roleNameCol" required="true">
        <p>Name of the column, in the "user roles" table, which contains
        a role name assigned to the corresponding user.</p>
      </attribute>

      <attribute name="userCredCol" required="true">
        <p>Name of the column, in the "users" table, which contains
        the user's credentials (i.e. password(.  If a value for the
        <code>digest</code> attribute is specified, this component
        will assume that the passwords have been encoded with the
        specified algorithm.  Otherwise, they will be assumed to be
        in clear text.</p>
      </attribute>

      <attribute name="userNameCol" required="true">
        <p>Name of the column, in the "users" and "user roles" table,
        that contains the user's username.</p>
      </attribute>

      <attribute name="userRoleTable" required="true">
        <p>Name of the "user roles" table, which must contain columns
        named by the <code>userNameCol</code> and <code>roleNameCol</code>
        attributes.</p>
      </attribute>

      <attribute name="userTable" required="true">
        <p>Name of the "users" table, which must contain columns named
        by the <code>userNameCol</code> and <code>userCredCol</code>
        attributes.</p>
      </attribute>

    </attributes>

    <p>See the <a href="../realm-howto.html#DataSourceRealm">
    DataSource Realm HOW-TO</a> for more information on setting up container
    managed security using the DataSource Database Realm component.</p>


    <h3>JNDI Directory Realm (org.apache.catalina.realm.JNDIRealm)</h3>


    <p>The <strong>JNDI Directory Realm</strong> connects Catalina to
    an LDAP Directory, accessed through an appropriate JNDI driver,
    that stores usernames, passwords, and their associated
    roles. Changes to the directory are immediately reflected in the
    information used to authenticate new logins.</p>


    <p>The directory realm supports a variety of approaches to using
    LDAP for authentication:</p>

    <ul>
    <li>The realm can either use a pattern to determine the
    distinguished name (DN) of the user's directory entry, or search
    the directory to locate that entry.
    </li>

    <li>The realm can authenticate the user either by binding to the
    directory with the DN of the user's entry and the password
    presented by the user, or by retrieving the password from the
    user's entry and performing a comparison locally.
    </li>

    <li>Roles may be represented in the directory as explicit entries
    found by a directory search (e.g. group entries of which the user
    is a member), as the values of an attribute in the user's entry,
    or both.
    </li>
    </ul>

    <p> A rich set of additional attributes lets you configure the
    required behaviour as well as the connection to the underlying
    directory and the element and attribute names used to retrieve
    information from the directory:</p>

    <attributes>
      <attribute name="adCompat" required="false">
        <p>Microsoft Active Directory often returns referrals.
        When iterating over NamingEnumerations these lead to
        PartialResultExceptions. If you want us to ignore those exceptions,
        set this attribute to "true". Unfortunately there's no stable way
        to detect, if the Exceptions really come from an AD referral.
        The default value is "false".</p>
      </attribute>

      <attribute name="alternateURL" required="false">
        <p>If a socket connection can not be made to the provider at
        the <code>connectionURL</code> an attempt will be made to use the
        <code>alternateURL</code>.</p>
      </attribute>

      <attribute name="authentication" required="false">
        <p>A string specifying the type of authentication to use.
        "none", "simple", "strong" or a provider specific definition
        can be used. If no value is given the providers default is used.</p>
      </attribute>

      <attribute name="commonRole" required="false">
        <p>A role name assigned to each successfully authenticated user in
        addition to the roles retrieved from LDAP. If not specified, only
        the roles retrieved via LDAP are used.</p>
      </attribute>

      <attribute name="connectionName" required="false">
        <p>The directory username to use when establishing a
        connection to the directory for LDAP search operations. If not
        specified an anonymous connection is made, which is often
        sufficient unless you specify the <code>userPassword</code>
        property.</p>
      </attribute>

      <attribute name="connectionPassword" required="false">
        <p>The directory password to use when establishing a
        connection to the directory for LDAP search operations. If not
        specified an anonymous connection is made, which is often
        sufficient unless you specify the <code>userPassword</code>
        property.</p>
      </attribute>

      <attribute name="connectionTimeout" required="false">
        <p>The timeout in milliseconds to use when establishing the connection
        to the LDAP directory. If not specified, a value of 5000 (5 seconds) is
        used.</p>
      </attribute>

      <attribute name="connectionURL" required="true">
        <p>The connection URL to be passed to the JNDI driver when
        establishing a connection to the directory.</p>
      </attribute>

      <attribute name="contextFactory" required="false">
        <p>Fully qualified Java class name of the factory class used
        to acquire our JNDI <code>InitialContext</code>.  By default,
        assumes that the standard JNDI LDAP provider will be utilized.</p>
      </attribute>
      
      <attribute name="derefAliases" required="false">
        <p>A string specifying how aliases are to be dereferenced during
        search operations. The allowed values are "always", "never",
        "finding" and "searching". If not specified, "always" is used.</p>
      </attribute>

      <attribute name="digest" required="false">
        <p>The digest algorithm to apply to the plaintext password offered
        by the user before comparing it with the value retrieved from the
        directory.  Valid values are those accepted for the algorithm name
        by the <code>java.security.MessageDigest</code> class. If not
        specified the plaintext password is assumed to be retrieved. Not
        required unless <code>userPassword</code> is specified</p>
      </attribute>

      <attribute name="protocol" required="false">
         <p>A string specifying the security protocol to use. If not given
         the providers default is used.</p>
      </attribute>

      <attribute name="referrals" required="false">
        <p>How do we handle JNDI referrals? Allowed values are
        "ignore", "follow", or "throw"  (see javax.naming.Context.REFERRAL
        for more information).
        Microsoft Active Directory often returns referrals.
        If you need to follow them set referrals to "follow".
        Caution: if your DNS is not part of AD, the LDAP client lib might try
        to resolve your domain name in DNS to find another LDAP server.</p>
      </attribute>

      <attribute name="roleBase" required="false">
        <p>The base directory entry for performing role searches. If
        not specified the top-level element in the directory context
        will be used.</p>
      </attribute>

      <attribute name="roleName" required="false">
        <p>The name of the attribute that contains role names in the
        directory entries found by a role search. In addition you can
        use the <code>userRoleName</code> property to specify the name
        of an attribute, in the user's entry, containing additional
        role names.  If <code>roleName</code> is not specified a role
        search does not take place, and roles are taken only from the
        user's entry.</p>
      </attribute>

      <attribute name="roleSearch" required="false">
        <p>The LDAP filter expression used for performing role
        searches.  Use <code>{0}</code> to substitute the
        distinguished name (DN) of the user, and/or <code>{1}</code> to
        substitute the username. If not specified a role search does
        not take place and roles are taken only from the attribute in
        the user's entry specified by the <code>userRoleName</code>
        property.</p>
      </attribute>

      <attribute name="roleSubtree" required="false">
        <p>Set to <code>true</code> if you want to search the entire
        subtree of the element specified by the <code>roleBase</code>
        property for role entries associated with the user. The
        default value of <code>false</code> causes only the top level
        to be searched.</p>
      </attribute>

      <attribute name="userBase" required="false">
        <p>The base element for user searches performed using the
        <code>userSearch</code> expression.  Not used if you are using
        the <code>userPattern</code> expression.</p>
      </attribute>

      <attribute name="userPassword" required="false">
        <p>Name of the attribute in the user's entry containing the
        user's password.  If you specify this value, JNDIRealm will
        bind to the directory using the values specified by
        <code>connectionName</code> and
        <code>connectionPassword</code> properties, and retrieve the
        corresponding attribute for comparison to the value specified
        by the user being authenticated.  If you do
        <strong>not</strong> specify this value, JNDIRealm will
        attempt a simple bind to the directory using the DN of the
        user's entry and the password presented by the user, with a
        successful bind being interpreted as an authenticated
        user.</p>
      </attribute>

      <attribute name="userPattern" required="false">
        <p>Pattern for the distinguished name (DN) of the user's
        directory entry, with <code>{0}</code> marking where the
        actual username should be inserted. You can use this property
        instead of <code>userSearch</code>, <code>userSubtree</code>
        and <code>userBase</code> when the distinguished name contains
        the username and is otherwise the same for all users.</p>
      </attribute>

      <attribute name="userRoleName" required="false">
        <p>The name of an attribute in the user's directory entry
        containing zero or more values for the names of roles assigned
        to this user.  In addition you can use the
        <code>roleName</code> property to specify the name of an
        attribute to be retrieved from individual role entries found
        by searching the directory. If <code>userRoleName</code> is
        not specified all the roles for a user derive from the role
        search.</p>
      </attribute>

      <attribute name="userSearch" required="false">
        <p>The LDAP filter expression to use when searching for a
        user's directory entry, with <code>{0}</code> marking where
        the actual username should be inserted.  Use this property
        (along with the <code>userBase</code> and
        <code>userSubtree</code> properties) instead of
        <code>userPattern</code> to search the directory for the
        user's entry.</p>
      </attribute>

      <attribute name="userSubtree" required="false">
        <p>Set to <code>true</code> if you want to search the entire
        subtree of the element specified by the <code>userBase</code>
        property for the user's entry. The default value of
        <code>false</code> causes only the top level to be searched.
        Not used if you are using the <code>userPattern</code>
        expression.</p>
      </attribute>

    </attributes>

    <p>See the <a href="../realm-howto.html">Container-Managed Security Guide</a> for more
    information on setting up container managed security using the
    JNDI Directory Realm component.</p>


    <h3>UserDatabase Realm (org.apache.catalina.realm.UserDatabaseRealm)</h3>

    <p>The <strong>UserDatabase Realm</strong> is a Realm implementation
    that is based on a UserDatabase resource made available through the global
    JNDI resources configured for this Tomcat instance.</p>

    <p>The Memory Based Realm implementation supports the following
    additional attributes:</p>

    <attributes>

      <attribute name="resourceName" required="true">
        <p>The name of the resource that this realm will use for user, password
        and role information.</p>
      </attribute>

    </attributes>

    <p>See the
    <a href="../realm-howto.html">Container-Managed Security Guide</a> for more
    information on setting up container managed security using the UserDatabase
    Realm component and the
    <a href="../jndi-resources-howto.html">JNDI resources how-to</a> for more
    information on how to configure a UserDatabase resource.</p>

    <h3>Memory Based Realm (org.apache.catalina.realm.MemoryRealm)</h3>

    <p>The <strong>Memory Based Realm</strong> is a simple Realm implementation
    that reads user information from an XML format, and represents it as a
    collection of Java objects in memory.  This implementation is intended
    solely to get up and running with container managed security - it is NOT
    intended for production use.  As such, there are no mechanisms for
    updating the in-memory collection of users when the content of the
    underlying data file is changed.</p>

    <p>The Memory Based Realm implementation supports the following
    additional attributes:</p>

    <attributes>

      <attribute name="digest" required="false">
        <p>The digest algorithm used to store passwords in non-plaintext
        formats. Valid values are those accepted for the algorithm name by the
        <code>java.security.MessageDigest</code> class. If not specified,
        passwords are stored in clear text.</p>
      </attribute>

      <attribute name="pathname" required="false">
        <p>Absolute or relative (to $CATALINA_BASE) pathname to the XML file
        containing our user information.  See below for details on the
        XML element format required.  If no pathname is specified, the
        default value is <code>conf/tomcat-users.xml</code>.</p>
      </attribute>

    </attributes>

    <p>The XML document referenced by the <code>pathname</code> attribute must
    conform to the following requirements:</p>
    <ul>
    <li>The root (outer) element must be <code>&lt;tomcat-users&gt;</code>.
        </li>
    <li>Each authorized user must be represented by a single XML element
        <code>&lt;user&gt;</code>, nested inside the root element.</li>
    <li>Each <code>&lt;user&gt;</code> element must have the following
        attributes:
        <ul>
        <li><strong>name</strong> - Username of this user (must be unique
            within this file).</li>
        <li><strong>password</strong> - Password of this user (in
            clear text).</li>
        <li><strong>roles</strong> - Comma-delimited list of the role names
            assigned to this user.</li>
        </ul></li>
    </ul>

    <p>See the <a href="../realm-howto.html">Container-Managed Security Guide</a> for more
    information on setting up container managed security using the
    Memory Based Realm component.</p>

    <h3>JAAS Realm (org.apache.catalina.realm.JAASRealm)</h3>

    <p><strong>JAASRealm</strong> is an implementation of the Tomcat 6
    <code>Realm</code> interface that authenticates users through the Java
    Authentication &amp; Authorization Service (JAAS) framework which is now
    provided as part of the standard J2SE API.</p>

    <p>Using JAASRealm gives the developer the ability to combine practically
    any conceivable security realm with Tomcat's CMA.</p>

    <p>JAASRealm is prototype for Tomcat of the JAAS-based J2EE authentication
    framework for J2EE v1.4, based on the <a
    href="http://www.jcp.org/en/jsr/detail?id=196">JCP Specification Request
    196</a> to enhance container-managed security and promote 'pluggable'
    authentication mechanisms whose implementations would be
    container-independent.</p>

    <p>Based on the JAAS login module and principal
    (see <code>javax.security.auth.spi.LoginModule</code> and
    <code>javax.security.Principal</code>), you can develop your own security
    mechanism or wrap another third-party mechanism for integration with the CMA
    as implemented by Tomcat.</p>

    <p>The JAAS Realm implementation supports the following additional
    attributes:</p>

    <attributes>

      <attribute name="appName" required="true">
       <p>The name of the application as configured in your login configuration
       file 
       (<a href="http://java.sun.com/j2se/1.4.1/docs/guide/security/jaas/tutorials/LoginConfigFile.html">JAAS LoginConfig</a>).</p>
      </attribute>

      <attribute name="userClassNames" required="true">
        <p>A comma-separated list of the names of the classes that you have made 
        for your user <code>Principals</code>.</p>
      </attribute>

      <attribute name="roleClassNames" required="false">
        <p>A comma-separated list of the names of the classes that you have made 
        for your role <code>Principals</code>.</p>
      </attribute>

      <attribute name="useContextClassLoader" required="false">
        <p>Instructs JAASRealm to use the context class loader for loading the
        user-specified <code>LoginModule</code> class and associated
        <code>Principal</code> classes. The default value is <code>true</code>,
        which is backwards-compatible with the way Tomcat 5 works. To load
        classes using the container's classloader, specify
        <code>false</code>.</p>
      </attribute>

    </attributes>

    <p>See the <a href="../realm-howto.html">Container-Managed Security
    Guide</a> for more information on setting up container managed security
    using the JAAS Realm component.</p>

    <h3>Combined Realm (org.apache.catalina.realm.CombinedRealm)</h3>

    <p><strong>CombinedRealm</strong> is an implementation of the Tomcat 6
    <code>Realm</code> interface that authenticates users through one or more
    sub-Realms.</p>

    <p>Using CombinedRealm gives the developer the ability to combine multiple
    Realms of the same or different types. This can be used to authenticate
    against different sources, provide fall back in case one Realm fails or for
    any other purpose that requires multiple Realms.</p>

    <p>Sub-realms are defined by nesting <code>Realm</code> elements inside the
    <code>Realm</code> element that defines the CombinedRealm. Authentication
    will be attempted against each <code>Realm</code> in the order they are
    listed. Authentication against any Realm will be sufficient to authenticate
    the user.</p>

    <p>The CombinedRealm implementation does not support any additional
    attributes.</p>

    <p>See the <a href="../realm-howto.html">Container-Managed Security
    Guide</a> for more information on setting up container managed security
    using the CombinedRealm component.</p>

    <h3>LockOut Realm (org.apache.catalina.realm.LockOutRealm)</h3>

    <p><strong>LockOutRealm</strong> is an implementation of the Tomcat 6
    <code>Realm</code> interface that extends the CombinedRealm to provide lock
    out functionality to provide a user lock out mechanism if there are too many
    failed authentication attempts in a given period of time.</p>
    
    <p>To ensure correct operation, there is a reasonable degree of
    synchronization in this Realm.</p>
    
    <p>This Realm does not require modification to the underlying Realms or the
    associated user storage mechanisms. It achieves this by recording all failed
    logins, including those for users that do not exist. To prevent a DOS by
    deliberating making requests with invalid users (and hence causing this
    cache to grow) the size of the list of users that have failed authentication
    is limited.</p>

    <p>Sub-realms are defined by nesting <code>Realm</code> elements inside the
    <code>Realm</code> element that defines the LockOutRealm. Authentication
    will be attempted against each <code>Realm</code> in the order they are
    listed. Authentication against any Realm will be sufficient to authenticate
    the user.</p>

    <p>The LockOutRealm implementation supports the following additional
    attributes.</p>

    <attributes>

      <attribute name="cacheRemovalWarningTime" required="false">
       <p>If a failed user is removed from the cache because the cache is too
       big before it has been in the cache for at least this period of time (in
       seconds) a warning message will be logged. Defaults to 3600 (1 hour).</p>
      </attribute>

      <attribute name="cacheSize" required="false">
       <p>Number of users that have failed authentication to keep in cache. Over
       time the cache will grow to this size and may not shrink. Defaults to
       1000.</p>
      </attribute>

      <attribute name="failureCount" required="false">
       <p>The number of times in a row a user has to fail authentication to be
       locked out. Defaults to 5.</p>
      </attribute>

      <attribute name="lockOutTime" required="false">
       <p>The time (in seconds) a user is locked out for after too many
       authentication failures. Defaults to 300 (5 minutes).</p>
      </attribute>

    </attributes>

    <p>See the <a href="../realm-howto.html">Container-Managed Security
    Guide</a> for more information on setting up container managed security
    using the LockOutRealm component.</p>

  </subsection>


</section>


<section name="Nested Components">

  <h3>CombinedRealm Implementation</h3>

  <p>If you are using the <em>CombinedRealm Implementation</em> or a Realm
  that extends the CombinedRealm, e.g. the LockOutRealm,
  <strong>&lt;Realm&gt;</strong> elements may be nested inside it.</p>

  <h3>Other Realm Implementations</h3>
  
  <p>No other Realm implementation supports nested components.</p>

</section>


<section name="Special Features">

  <p>See <a href="host.html">Single Sign On</a> for information about
  configuring Single Sign On support for a virtual host.</p>

</section>


</body>


</document>
