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/*
 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.
 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.
 */

package sun.security.krb5.internal.rcache;

import sun.security.krb5.KrbException;
import sun.security.krb5.Config;
import sun.security.krb5.internal.Krb5;
import java.util.LinkedList;
import java.util.ListIterator;
import sun.security.krb5.internal.KerberosTime;

This class provides an efficient caching mechanism to store the timestamp of client authenticators. The cache minimizes the memory usage by doing self-cleanup of expired items in the cache.
Author:Yanni Zhang
/** * This class provides an efficient caching mechanism to store the timestamp of client authenticators. * The cache minimizes the memory usage by doing self-cleanup of expired items in the cache. * * @author Yanni Zhang */
public class ReplayCache extends LinkedList<AuthTime> { private static final long serialVersionUID = 2997933194993803994L; private String principal; private CacheTable table; private int nap = 10 * 60 * 1000; //10 minutes break private boolean DEBUG = Krb5.DEBUG;
Constructs a ReplayCache for a client principal in specified CacheTable.
Params:
  • p – client principal name.
  • ct – CacheTable.
/** * Constructs a ReplayCache for a client principal in specified <code>CacheTable</code>. * @param p client principal name. * @param ct CacheTable. */
public ReplayCache (String p, CacheTable ct) { principal = p; table = ct; }
Puts the authenticator timestamp into the cache in descending order.
Params:
  • t – AuthTime
/** * Puts the authenticator timestamp into the cache in descending order. * @param t <code>AuthTime</code> */
public synchronized void put(AuthTime t, long currentTime) { if (this.size() == 0) { addFirst(t); } else { AuthTime temp = getFirst(); if (temp.kerberosTime < t.kerberosTime) { // in most cases, newly received authenticator has // larger timestamp. addFirst(t); } else if (temp.kerberosTime == t.kerberosTime) { if (temp.cusec < t.cusec) { addFirst(t); } } else { //unless client clock being re-adjusted. ListIterator<AuthTime> it = listIterator(1); while (it.hasNext()) { temp = it.next(); if (temp.kerberosTime < t.kerberosTime) { add(indexOf(temp), t); break; //we always put the bigger timestamp at the front. } else if (temp.kerberosTime == t.kerberosTime) { if (temp.cusec < t.cusec) { add(indexOf(temp), t); break; } } } } } // let us cleanup while we are here long timeLimit = currentTime - KerberosTime.getDefaultSkew() * 1000L; ListIterator<AuthTime> it = listIterator(0); AuthTime temp = null; int index = -1; while (it.hasNext()) { //search expired timestamps. temp = it.next(); if (temp.kerberosTime < timeLimit) { index = indexOf(temp); break; } } if (index > -1) { do { //remove expired timestamps from the list. removeLast(); } while(size() > index); } if (DEBUG) { printList(); } // if there are no entries in the replay cache, // remove the replay cache from the table. if (this.size() == 0) { table.remove(principal); } if (DEBUG) { printList(); } }
Printes out the debug message.
/** * Printes out the debug message. */
private void printList() { Object[] total = toArray(); for (int i = 0; i < total.length; i++) { System.out.println("object " + i + ": " + ((AuthTime)total[i]).kerberosTime + "/" + ((AuthTime)total[i]).cusec); } } }