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/**
 * 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.commons.crypto.random;

import java.security.GeneralSecurityException;
import java.util.List;
import java.util.Properties;

import org.apache.commons.crypto.Crypto;
import org.apache.commons.crypto.utils.ReflectionUtils;
import org.apache.commons.crypto.utils.Utils;

This is the factory class used for creating CryptoRandom instances /**
 * This is the factory class used for creating {@link CryptoRandom} instances
 */
public class CryptoRandomFactory {

    // security random related configuration keys
    
The configuration key of the file path for secure random device.
/**
     * The configuration key of the file path for secure random device.
     */
    public static final String DEVICE_FILE_PATH_KEY = Crypto.CONF_PREFIX
            + "secure.random.device.file.path";

    
The default value ("/dev/urandom") of the file path for secure random device. /**
     * The default value ({@value}) of the file path for secure random device.
     */
    // Note: this is public mainly for use by the Javadoc
    public static final String DEVICE_FILE_PATH_DEFAULT = "/dev/urandom";

    
The configuration key of the algorithm of secure random.
/**
     * The configuration key of the algorithm of secure random.
     */
    public static final String JAVA_ALGORITHM_KEY = Crypto.CONF_PREFIX
            + "secure.random.java.algorithm";

    
The default value ("SHA1PRNG") of the algorithm of secure random. /**
     * The default value ({@value}) of the algorithm of secure random.
     */
    // Note: this is public mainly for use by the Javadoc
    public static final String JAVA_ALGORITHM_DEFAULT = "SHA1PRNG";

    
The configuration key of the CryptoRandom implementation class.
 The value of the CLASSES_KEY needs to be the full name of a class that implements the CryptoRandom interface The internal classes are listed in the enum RandomProvider which can be used to obtain the full class name. 

The value can also be a comma-separated list of class names in
order of descending priority.
/**
     * The configuration key of the CryptoRandom implementation class.
     * <p>
     * The value of the CLASSES_KEY needs to be the full name of a
     * class that implements the
     * {@link org.apache.commons.crypto.random.CryptoRandom CryptoRandom} interface
     * The internal classes are listed in the enum
     * {@link RandomProvider RandomProvider}
     * which can be used to obtain the full class name.
     * <p>
     * The value can also be a comma-separated list of class names in
     * order of descending priority.
     */
    public static final String CLASSES_KEY = Crypto.CONF_PREFIX
            + "secure.random.classes";
    
Defines the internal CryptoRandom implementations.

Usage:
props.setProperty(CryptoRandomFactory.CLASSES_KEY, RandomProvider.OPENSSL.getClassName());
props.setProperty(...); // if required by the implementation
random = CryptoRandomFactory.getCryptoRandom(transformation, props);

/**
     * Defines the internal CryptoRandom implementations.
     * <p>
     * Usage:
     * <blockquote><pre>
     * props.setProperty(CryptoRandomFactory.CLASSES_KEY, RandomProvider.OPENSSL.getClassName());
     * props.setProperty(...); // if required by the implementation
     * random = CryptoRandomFactory.getCryptoRandom(transformation, props);
     * </pre></blockquote>
     */
    public enum RandomProvider {

        
The OpenSSL Random implementation (using JNI)
 No properties are used for configuration, but they are passed to the JAVA backup implementation /**
         * The OpenSSL Random implementation (using JNI)
         * <p>
         * No properties are used for configuration, but they
         * are passed to the {@link RandomProvider#JAVA} backup implementation
         */
        // Please ensure the property description agrees with the implementation
        OPENSSL(OpenSslCryptoRandom.class),

        
The SecureRandom implementation from the JVM
 Uses the property with key CryptoRandomFactory.JAVA_ALGORITHM_KEY with the default of CryptoRandomFactory.JAVA_ALGORITHM_DEFAULT /**
         * The SecureRandom implementation from the JVM
         * <p>
         * Uses the property with key
         * {@link #JAVA_ALGORITHM_KEY}
         * with the default of
         * {@link #JAVA_ALGORITHM_DEFAULT}
         */
        // Please ensure the property description agrees with the implementation
        JAVA(JavaCryptoRandom.class),

        
The OS random device implementation. May not be available on some OSes.
 Uses CryptoRandomFactory.DEVICE_FILE_PATH_KEY to determine the path to the random device, default is CryptoRandomFactory.DEVICE_FILE_PATH_DEFAULT /**
         * The OS random device implementation. May not be available on some OSes.
         * <p>
         * Uses {@link #DEVICE_FILE_PATH_KEY} to determine the
         * path to the random device, default is
         * {@link #DEVICE_FILE_PATH_DEFAULT}
         */
        // Please ensure the property description agrees with the implementation
        OS(OsCryptoRandom.class);

        private final Class<? extends CryptoRandom> klass;

        private final String className;

        
The private constructor.
Params:
klass – the Class of CryptoRandom/**
         * The private constructor.
         * @param klass the Class of CryptoRandom
         */
        private RandomProvider(final Class<? extends CryptoRandom> klass) {
            this.klass = klass;
            this.className = klass.getName();
        }

        
Gets the class name of the provider.
Returns:
the name of the provider class/**
         * Gets the class name of the provider.
         *
         * @return the name of the provider class
         */
        public String getClassName() {
            return className;
        }

        
Gets the implementation class of the provider.
Returns:
the implementation class of the provider/**
         * Gets the implementation class of the provider.
         *
         * @return the implementation class of the provider
         */
        public Class<? extends CryptoRandom> getImplClass() {
            return klass;
        }
    }

    
The default value (OPENSSL,JAVA) used when creating a CryptoCipher. /**
     * The default value (OPENSSL,JAVA) used when creating a {@link org.apache.commons.crypto.cipher.CryptoCipher}.
     */
    private static final String CLASSES_DEFAULT =
        RandomProvider.OPENSSL.getClassName()
        .concat(",")
        .concat(RandomProvider.JAVA.getClassName());

    
The private constructor of CryptoRandomFactory. /**
     * The private constructor of {@link CryptoRandomFactory}.
     */
    private CryptoRandomFactory() {
    }

    
Gets a CryptoRandom instance using the default implementation as defined by CLASSES_DEFAULT 
Throws:
GeneralSecurityException – if cannot create the CryptoRandom class
Returns:
CryptoRandom  the cryptoRandom object./**
     * Gets a CryptoRandom instance using the default implementation
     * as defined by {@link #CLASSES_DEFAULT}
     *
     * @return CryptoRandom  the cryptoRandom object.
     * @throws GeneralSecurityException if cannot create the {@link CryptoRandom} class
     */
    public static CryptoRandom getCryptoRandom() throws GeneralSecurityException {
        final Properties properties = new Properties();
        return getCryptoRandom(properties);
    }

    
Gets a CryptoRandom instance for specified props.
Uses the SECURE_RANDOM_CLASSES_KEY from the provided
properties.
If it is not set, then it checks the System properties.
Failing that, it defaults to OpenSslCryptoRandom,JavaCryptoRandom
The properties are passed to the generated class.
Params:
props – the configuration properties.
Throws:
GeneralSecurityException – if cannot create the CryptoRandom class
IllegalArgumentException – if no classname(s) are provided
Returns:
CryptoRandom  the cryptoRandom object./**
     * Gets a CryptoRandom instance for specified props.
     * Uses the SECURE_RANDOM_CLASSES_KEY from the provided
     * properties.
     * If it is not set, then it checks the System properties.
     * Failing that, it defaults to OpenSslCryptoRandom,JavaCryptoRandom
     * The properties are passed to the generated class.
     *
     * @param props the configuration properties.
     * @return CryptoRandom  the cryptoRandom object.
     * @throws GeneralSecurityException if cannot create the {@link CryptoRandom} class
     * @throws IllegalArgumentException if no classname(s) are provided
     */
    public static CryptoRandom getCryptoRandom(final Properties props)
            throws GeneralSecurityException {
        final List<String> names = Utils.splitClassNames(getRandomClassString(props), ",");
        if (names.size() == 0) {
            throw new IllegalArgumentException("No class name(s) provided");
        }
        final StringBuilder errorMessage = new StringBuilder();
        CryptoRandom random = null;
        Exception lastException = null;
        for (final String klassName : names) {
            try {
                final Class<?> klass = ReflectionUtils.getClassByName(klassName);
                random = (CryptoRandom) ReflectionUtils.newInstance(klass, props);
                if (random != null) {
                    break;
                }
            } catch (final ClassCastException e) {
                lastException = e;
                errorMessage.append("Class: [" + klassName + "] is not a CryptoRandom.");
            } catch (final ClassNotFoundException e) {
                lastException = e;
                errorMessage.append("CryptoRandom: [" + klassName + "] not found.");
            } catch (final Exception e) {
                lastException = e;
                errorMessage.append("CryptoRandom: [" + klassName + "] failed with " + e.getMessage());
            }
        }

        if (random != null) {
            return random;
        }
        throw new GeneralSecurityException(errorMessage.toString(), lastException);
    }

    
Gets the CryptoRandom class.
Params:
props – The Properties class represents a set of properties.
Returns:
the CryptoRandom class based on the props./**
     * Gets the CryptoRandom class.
     *
     * @param props The {@code Properties} class represents a set of
     *        properties.
     * @return the CryptoRandom class based on the props.
     */
    private static String getRandomClassString(final Properties props) {
        String randomClassString = props.getProperty(CryptoRandomFactory.CLASSES_KEY, CLASSES_DEFAULT);
        if (randomClassString.isEmpty()) { // TODO does it make sense to treat the empty string as the default?
            randomClassString = CLASSES_DEFAULT;
        }
        return randomClassString;
    }
}