com.qut.middleware.esoemanager.util.PolicyIDGenerator.java Source code

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Here is the source code for com.qut.middleware.esoemanager.util.PolicyIDGenerator.java

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/* Copyright 2008, Queensland University of Technology
 * Licensed 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 com.qut.middleware.esoemanager.util;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.concurrent.locks.ReentrantLock;

import org.apache.commons.codec.binary.Hex;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.qut.middleware.saml2.identifier.impl.Messages;

public class PolicyIDGenerator {
    private ReentrantLock lock;
    private SecureRandom random;
    private final String RNG = "SHA1PRNG";

    /* Local logging instance */
    private Logger logger = LoggerFactory.getLogger(PolicyIDGenerator.class.getName());

    public PolicyIDGenerator() {
        this.lock = new ReentrantLock();

        try {
            /* Attempt to get the specified RNG instance */
            this.random = SecureRandom.getInstance(this.RNG);
        } catch (NoSuchAlgorithmException nsae) {
            this.logger.error(Messages.getString("IdentifierGeneratorImpl.13")); //$NON-NLS-1$
            this.logger.debug(nsae.getLocalizedMessage(), nsae);
            this.random = new SecureRandom();
        }

        this.random.setSeed(System.currentTimeMillis());
    }

    public String generatePolicyID() {
        String id = "lxacmlpolicy:access:" + generate(6) + ":" + System.currentTimeMillis();
        return id;
    }

    /**
     * Generates the specified number of random bytes using SecureRandom
     * 
     * @param length
     *            The number of random bytes to generate
     * @return The generated random string
     */
    private String generate(int length) {
        String id;
        byte[] buf;
        buf = new byte[length];

        this.lock.lock();
        try {
            /* Seed the specified RNG instance and get bytes */
            this.random.setSeed(Thread.currentThread().getName().getBytes());
            this.random.setSeed(System.currentTimeMillis());
            this.random.nextBytes(buf);
        } finally {
            this.lock.unlock();
        }

        id = new String(Hex.encodeHex(buf));

        return id;
    }

}