/*
* Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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.internal.Krb5;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import sun.security.krb5.internal.KerberosTime;
import sun.security.krb5.internal.KrbApErrException;
/**
* This class provides an efficient caching mechanism to store AuthTimeWithHash
* from client authenticators. The cache minimizes the memory usage by doing
* self-cleanup of expired items in the cache.
*
* AuthTimeWithHash objects inside a cache are always sorted from big (new) to
* small (old) as determined by {@link AuthTimeWithHash#compareTo}. In the most
* common case a newcomer should be newer than the first element.
*
* @author Yanni Zhang
*/
public class AuthList {
private final LinkedList<AuthTimeWithHash> entries;
private final int lifespan;
// entries.getLast().ctime, updated after each cleanup.
private volatile int oldestTime = Integer.MIN_VALUE;
/**
* Constructs a AuthList.
*/
public AuthList(int lifespan) {
this.lifespan = lifespan;
entries = new LinkedList<>();
}
/**
* Puts the authenticator timestamp into the cache in descending order,
* and throw an exception if it's already there.
*/
public synchronized void put(AuthTimeWithHash t, KerberosTime currentTime)
throws KrbApErrException {
if (entries.isEmpty()) {
entries.addFirst(t);
oldestTime = t.ctime;
return;
} else {
AuthTimeWithHash temp = entries.getFirst();
int cmp = temp.compareTo(t);
if (cmp < 0) {
// This is the most common case, newly received authenticator
// has larger timestamp.
entries.addFirst(t);
} else if (cmp == 0) {
throw new KrbApErrException(Krb5.KRB_AP_ERR_REPEAT);
} else {
//unless client clock being re-adjusted.
ListIterator<AuthTimeWithHash> it = entries.listIterator(1);
boolean found = false;
while (it.hasNext()) {
temp = it.next();
cmp = temp.compareTo(t);
if (cmp < 0) {
// Find an older one, put in front of it
entries.add(entries.indexOf(temp), t);
found = true;
break;
} else if (cmp == 0) {
throw new KrbApErrException(Krb5.KRB_AP_ERR_REPEAT);
}
}
if (!found) {
// All is newer than the newcomer. Sigh.
entries.addLast(t);
}
}
}
// let us cleanup while we are here
long timeLimit = currentTime.getSeconds() - lifespan;
// Only trigger a cleanup when the earliest entry is
// lifespan + 5 sec ago. This ensures a cleanup is done
// at most every 5 seconds so that we don't always
// addLast(removeLast).
if (oldestTime > timeLimit - 5) {
return;
}
// and we remove the *enough* old ones (1 lifetime ago)
while (!entries.isEmpty()) {
AuthTimeWithHash removed = entries.removeLast();
if (removed.ctime >= timeLimit) {
entries.addLast(removed);
oldestTime = removed.ctime;
return;
}
}
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