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 * Copyright (c) 1996, 2016, 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,

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 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.security;

import java.util.*;

import java.util.regex.*;

import java.security.Provider.Service;

import sun.security.jca.*;

import sun.security.jca.GetInstance.Instance;

import sun.security.util.Debug;

/**

 * This class provides a cryptographically strong random number

 * generator (RNG).

 *

 * <a href="http://csrc.nist.gov/publications/fips/fips140-2/fips1402.pdf">

 * <i>FIPS 140-2, Security Requirements for Cryptographic Modules</i></a>,

 * section 4.9.1.

 * cryptographically strong, as described in

 * <a href="http://tools.ietf.org/html/rfc4086">

 * <i>RFC 4086: Randomness Requirements for Security</i></a>.

 *

 * Other implementations may produce true random numbers,

 * and yet others may use a combination of both techniques.

 *

 * to retrieve random bytes:

 *

 *

 * to generate a given number of seed bytes (to seed other random number

 * generators, for example):

 *

 *

 * @see java.security.SecureRandomSpi

 * @see java.util.Random

 *

 * @author Benjamin Renaud

 * @author Josh Bloch

 */

public class SecureRandom extends java.util.Random {

    private static final Debug pdebug =

                        Debug.getInstance("provider", "Provider");

    private static final boolean skipDebug =

        Debug.isOn("engine=") && !Debug.isOn("securerandom");

    /**

     * The provider.

     *

     * @serial

     * @since 1.2

     */

    private Provider provider = null;

    /**

     * The provider implementation.

     *

     * @serial

     * @since 1.2

     */

    private SecureRandomSpi secureRandomSpi = null;

    /*

     * The algorithm name of null if unknown.

     *

     * @serial

     * @since 1.5

     */

    private String algorithm;

    // Seed Generator

    private static volatile SecureRandom seedGenerator;

    /**

     * Constructs a secure random number generator (RNG) implementing the

     * default random number algorithm.

     *

     * <p> This constructor traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * If none of the Providers support a RNG algorithm,

     * then an implementation-specific default is returned.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard RNG algorithm names.

     */

    public SecureRandom() {

        /*

         * This call to our superclass constructor will result in a call

         * to our own {@code setSeed} method, which will return

         * immediately when it is passed zero.

         */

        super(0);

        getDefaultPRNG(false, null);

    }

    /**

     * Constructs a secure random number generator (RNG) implementing the

     * default random number algorithm.

     *

     * <p> This constructor traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * If none of the Providers support a RNG algorithm,

     * then an implementation-specific default is returned.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard RNG algorithm names.

     *

     * @param seed the seed.

     */

    public SecureRandom(byte[] seed) {

        super(0);

        getDefaultPRNG(true, seed);

    }

    private void getDefaultPRNG(boolean setSeed, byte[] seed) {

        String prng = getPrngAlgorithm();

        if (prng == null) {

            // bummer, get the SUN implementation

            prng = "SHA1PRNG";

            this.secureRandomSpi = new sun.security.provider.SecureRandom();

            this.provider = Providers.getSunProvider();

            if (setSeed) {

                this.secureRandomSpi.engineSetSeed(seed);

            }

        } else {

            try {

                SecureRandom random = SecureRandom.getInstance(prng);

                this.secureRandomSpi = random.getSecureRandomSpi();

                this.provider = random.getProvider();

                if (setSeed) {

                    this.secureRandomSpi.engineSetSeed(seed);

                }

            } catch (NoSuchAlgorithmException nsae) {

                // never happens, because we made sure the algorithm exists

                throw new RuntimeException(nsae);

            }

        }

        // JDK 1.1 based implementations subclass SecureRandom instead of

        // SecureRandomSpi. They will also go through this code path because

        // they must call a SecureRandom constructor as it is their superclass.

        // If we are dealing with such an implementation, do not set the

        // algorithm value as it would be inaccurate.

        if (getClass() == SecureRandom.class) {

            this.algorithm = prng;

        }

    }

    /**

     *

     * @param provider the provider.

     */

    protected SecureRandom(SecureRandomSpi secureRandomSpi,

                           Provider provider) {

        this(secureRandomSpi, provider, null);

    }

    private SecureRandom(SecureRandomSpi secureRandomSpi, Provider provider,

            String algorithm) {

        super(0);

        this.secureRandomSpi = secureRandomSpi;

        this.provider = provider;

        this.algorithm = algorithm;

        if (!skipDebug && pdebug != null) {

            pdebug.println("SecureRandom." + algorithm +

                " algorithm from: " + this.provider.getName());

        }

    }

    /**

     * Random Number Generator (RNG) algorithm.

     *

     * <p> This method traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * Provider that supports the specified algorithm is returned.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @implNote

     * The JDK Reference Implementation additionally uses the

     * {@code jdk.security.provider.preferred}

     * {@link Security#getProperty(String) Security} property to determine

     * the preferred provider order for the specified algorithm. This

     * may be different than the order of providers returned by

     * {@link Security#getProviders() Security.getProviders()}.

     *

     * @param algorithm the name of the RNG algorithm.

     * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard RNG algorithm names.

     *

     *

     * @exception NoSuchAlgorithmException if no Provider supports a

     *          specified algorithm.

     *

     * @see Provider

     *

     * @since 1.2

     */

    public static SecureRandom getInstance(String algorithm)

            throws NoSuchAlgorithmException {

        Instance instance = GetInstance.getInstance("SecureRandom",

        return new SecureRandom((SecureRandomSpi)instance.impl,

    }

    /**

     * Random Number Generator (RNG) algorithm.

     *

     * is returned.  The specified provider must be registered

     * in the security provider list.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @param algorithm the name of the RNG algorithm.

     * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard RNG algorithm names.

     *

     * @param provider the name of the provider.

     *

     *

     *

     *

     *

     * @see Provider

     *

     * @since 1.2

     */

    public static SecureRandom getInstance(String algorithm, String provider)

            throws NoSuchAlgorithmException, NoSuchProviderException {

        Instance instance = GetInstance.getInstance("SecureRandom",

            SecureRandomSpi.class, algorithm, provider);

        return new SecureRandom((SecureRandomSpi)instance.impl,

            instance.provider, algorithm);

    }

    /**

     * Random Number Generator (RNG) algorithm.

     *

     * does not have to be registered in the provider list.

     *

     * @param algorithm the name of the RNG algorithm.

     * "{@docRoot}/../technotes/guides/security/StandardNames.html#SecureRandom">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard RNG algorithm names.

     *

     * @param provider the provider.

     *

     *

     *

     *

     * @see Provider

     *

     * @since 1.4

     */

    public static SecureRandom getInstance(String algorithm,

            Provider provider) throws NoSuchAlgorithmException {

        Instance instance = GetInstance.getInstance("SecureRandom",

            SecureRandomSpi.class, algorithm, provider);

        return new SecureRandom((SecureRandomSpi)instance.impl,

            instance.provider, algorithm);

    }

    /**