/*
* Copyright 2002-2016 the original author or authors.
*
* 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 org.springframework.security.core.token;
import java.io.InputStream;
import java.security.SecureRandom;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.util.FileCopyUtils;
/**
* Creates a {@link SecureRandom} instance.
*
* @author Ben Alex
* @since 2.0.1
*/
public class SecureRandomFactoryBean implements FactoryBean<SecureRandom> {
private String algorithm = "SHA1PRNG";
private Resource seed;
public SecureRandom getObject() throws Exception {
SecureRandom rnd = SecureRandom.getInstance(algorithm);
if (seed != null) {
// Seed specified, so use it
byte[] seedBytes = FileCopyUtils.copyToByteArray(seed.getInputStream());
rnd.setSeed(seedBytes);
}
else {
// Request the next bytes, thus eagerly incurring the expense of default
// seeding
rnd.nextBytes(new byte[1]);
}
return rnd;
}
public Class<SecureRandom> getObjectType() {
return SecureRandom.class;
}
public boolean isSingleton() {
return false;
}
/**
* Allows the Pseudo Random Number Generator (PRNG) algorithm to be nominated.
* Defaults to "SHA1PRNG".
*
* @param algorithm to use (mandatory)
*/
public void setAlgorithm(String algorithm) {
Assert.hasText(algorithm, "Algorithm required");
this.algorithm = algorithm;
}
/**
* Allows the user to specify a resource which will act as a seed for the
* {@link SecureRandom} instance. Specifically, the resource will be read into an
* {@link InputStream} and those bytes presented to the
* {@link SecureRandom#setSeed(byte[])} method. Note that this will simply supplement,
* rather than replace, the existing seed. As such, it is always safe to set a seed
* using this method (it never reduces randomness).
*
* @param seed to use, or <code>null</code> if no additional seeding is needed
*/
public void setSeed(Resource seed) {
this.seed = seed;
}
}