kerberos-shared/src/main/java/org/apache/directory/server/kerberos/shared/replay/InMemoryReplayCache.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *  
 *    http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License. 
 *  
 */
package org.apache.directory.server.kerberos.shared.replay;


import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.security.auth.kerberos.KerberosPrincipal;

import org.apache.directory.server.kerberos.shared.messages.value.KerberosTime;


/**
 * "The replay cache will store at least the server name, along with the client name,
 * time, and microsecond fields from the recently-seen authenticators, and if a
 * matching tuple is found, the KRB_AP_ERR_REPEAT error is returned."
 *    
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 * @version $Rev$, $Date$
 */
public class InMemoryReplayCache implements ReplayCache
{
    private List<ReplayCacheEntry> list = new ArrayList<ReplayCacheEntry>();

    private long clockSkew = 5 * KerberosTime.MINUTE;


    /**
     * Sets the clock skew.
     *
     * @param clockSkew
     */
    public void setClockSkew( long clockSkew )
    {
        this.clockSkew = clockSkew;
    }


    public synchronized boolean isReplay( KerberosPrincipal serverPrincipal, KerberosPrincipal clientPrincipal,
        KerberosTime clientTime, int clientMicroSeconds )
    {
        ReplayCacheEntry testEntry = new ReplayCacheEntry( serverPrincipal, clientPrincipal, clientTime,
            clientMicroSeconds );

        Iterator<ReplayCacheEntry> it = list.iterator();
        while ( it.hasNext() )
        {
            ReplayCacheEntry entry = it.next();

            if ( entry.equals( testEntry ) )
            {
                return true;
            }

            if ( entry.isOutsideClockSkew( clockSkew ) )
            {
                it.remove();
            }
        }

        return false;
    }


    public synchronized void save( KerberosPrincipal serverPrincipal, KerberosPrincipal clientPrincipal,
        KerberosTime clientTime, int clientMicroSeconds )
    {
        list.add( new ReplayCacheEntry( serverPrincipal, clientPrincipal, clientTime, clientMicroSeconds ) );
    }

    private class ReplayCacheEntry
    {
        private KerberosPrincipal serverPrincipal;
        private KerberosPrincipal clientPrincipal;
        private KerberosTime clientTime;
        private int clientMicroSeconds;


        /**
         * Creates a new instance of ReplayCacheEntry.
         * 
         * @param serverPrincipal 
         * @param clientPrincipal 
         * @param clientTime 
         * @param clientMicroSeconds 
         */
        public ReplayCacheEntry( KerberosPrincipal serverPrincipal, KerberosPrincipal clientPrincipal,
            KerberosTime clientTime, int clientMicroSeconds )
        {
            this.serverPrincipal = serverPrincipal;
            this.clientPrincipal = clientPrincipal;
            this.clientTime = clientTime;
            this.clientMicroSeconds = clientMicroSeconds;
        }


        /**
         * Returns whether this {@link ReplayCacheEntry} is equal to another {@link ReplayCacheEntry}.
         * {@link ReplayCacheEntry}'s are equal when the server name, client name, client time, and
         * the client microseconds are equal.
         *
         * @param that
         * @return true if the ReplayCacheEntry's are equal.
         */
        public boolean equals( ReplayCacheEntry that )
        {
            return serverPrincipal.equals( that.serverPrincipal ) && clientPrincipal.equals( that.clientPrincipal )
                && clientTime.equals( that.clientTime ) && clientMicroSeconds == that.clientMicroSeconds;
        }


        /**
         * Returns whether this {@link ReplayCacheEntry} is older than a given time.
         *
         * @param clockSkew
         * @return true if the {@link ReplayCacheEntry}'s client time is outside the clock skew time.
         */
        public boolean isOutsideClockSkew( long clockSkew )
        {
            return !clientTime.isInClockSkew( clockSkew );
        }
    }
}