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 * accompanied this code).

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package javax.crypto;

import java.util.*;

import java.security.*;

import java.security.Provider.Service;

import java.security.spec.*;

import sun.security.jca.*;

import sun.security.jca.GetInstance.Instance;

import sun.security.util.Debug;

/**

 * This class provides the functionality of a secret (symmetric) key generator.

 *

 * <p>Key generators are constructed using one of the {@code getInstance}

 * class methods of this class.

 *

 * <p>KeyGenerator objects are reusable, i.e., after a key has been

 * generated, the same KeyGenerator object can be re-used to generate further

 * keys.

 *

 * <p>There are two ways to generate a key: in an algorithm-independent

 * manner, and in an algorithm-specific manner.

 * The only difference between the two is the initialization of the object:

 *

 * <ul>

 * <li><b>Algorithm-Independent Initialization</b>

 * <p>All key generators share the concepts of a <i>keysize</i> and a

 * <i>source of randomness</i>.

 * There is an

 * {@link #init(int, java.security.SecureRandom) init}

 * method in this KeyGenerator class that takes these two universally

 * shared types of arguments. There is also one that takes just a

 * {@code keysize} argument, and uses the SecureRandom implementation

 * of the highest-priority installed provider as the source of randomness

 * (or a system-provided source of randomness if none of the installed

 * providers supply a SecureRandom implementation), and one that takes just a

 * source of randomness.

 *

 * <p>Since no other parameters are specified when you call the above

 * algorithm-independent {@code init} methods, it is up to the

 * provider what to do about the algorithm-specific parameters (if any) to be

 * associated with each of the keys.

 *

 * <li><b>Algorithm-Specific Initialization</b>

 * <p>For situations where a set of algorithm-specific parameters already

 * exists, there are two

 * {@link #init(java.security.spec.AlgorithmParameterSpec) init}

 * methods that have an {@code AlgorithmParameterSpec}

 * argument. One also has a {@code SecureRandom} argument, while the

 * other uses the SecureRandom implementation

 * of the highest-priority installed provider as the source of randomness

 * (or a system-provided source of randomness if none of the installed

 * providers supply a SecureRandom implementation).

 * </ul>

 *

 * <p>In case the client does not explicitly initialize the KeyGenerator

 * (via a call to an {@code init} method), each provider must

 * supply (and document) a default initialization.

 * See the Keysize Restriction sections of the

 * {@extLink security_guide_jdk_providers JDK Providers}

 * document for information on the KeyGenerator defaults used by

 * JDK providers.

 * However, note that defaults may vary across different providers.

 * Additionally, the default value for a provider may change in a future

 * version. Therefore, it is recommended to explicitly initialize the

 * KeyGenerator instead of relying on provider-specific defaults.

 *

 * <p> Every implementation of the Java platform is required to support the

 * following standard {@code KeyGenerator} algorithms with the keysizes in

 * parentheses:

 * <ul>

 * <li>{@code AES} (128)</li>

 * <li>{@code DESede} (168)</li>

 * <li>{@code HmacSHA1}</li>

 * <li>{@code HmacSHA256}</li>

 * </ul>

 * These algorithms are described in the <a href=

 * "{@docRoot}/../specs/security/standard-names.html#keygenerator-algorithms">

 * KeyGenerator section</a> of the

 * Java Security Standard Algorithm Names Specification.

 * Consult the release documentation for your implementation to see if any

 * other algorithms are supported.

 *

 * @author Jan Luehe

 *

 * @see SecretKey

 * @since 1.4

 */

public class KeyGenerator {

    private static final Debug pdebug =

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

    private static final boolean skipDebug =

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

    // see java.security.KeyPairGenerator for failover notes

    private static final int I_NONE   = 1;

    private static final int I_RANDOM = 2;

    private static final int I_PARAMS = 3;

    private static final int I_SIZE   = 4;

    // The provider

    private Provider provider;

    // The provider implementation (delegate)

    private volatile KeyGeneratorSpi spi;

    // The algorithm

    private final String algorithm;

    private final Object lock = new Object();

    private Iterator<Service> serviceIterator;

    private int initType;

    private int initKeySize;

    private AlgorithmParameterSpec initParams;

    private SecureRandom initRandom;

    /**

     * Creates a KeyGenerator object.

     *

     * @param keyGenSpi the delegate

     * @param provider the provider

     * @param algorithm the algorithm

     */

    protected KeyGenerator(KeyGeneratorSpi keyGenSpi, Provider provider,

                           String algorithm) {

        this.spi = keyGenSpi;

        this.provider = provider;

        this.algorithm = algorithm;

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

            pdebug.println("KeyGenerator." + algorithm + " algorithm from: " +

                getProviderName());

        }

    }

    private KeyGenerator(String algorithm) throws NoSuchAlgorithmException {

        this.algorithm = algorithm;

        List<Service> list =

                GetInstance.getServices("KeyGenerator", algorithm);

        serviceIterator = list.iterator();

        initType = I_NONE;

        // fetch and instantiate initial spi

        if (nextSpi(null, false) == null) {

            throw new NoSuchAlgorithmException

                (algorithm + " KeyGenerator not available");

        }

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

            pdebug.println("KeyGenerator." + algorithm + " algorithm from: " +

                getProviderName());

        }

    }

    private String getProviderName() {

        return (provider == null) ? "(no provider)" : provider.getName();

    }

    /**

     * Returns the algorithm name of this {@code KeyGenerator} object.

     *

     * <p>This is the same name that was specified in one of the

     * {@code getInstance} calls that created this

     * {@code KeyGenerator} object.

     *

     * @return the algorithm name of this {@code KeyGenerator} object.

     */

    public final String getAlgorithm() {

        return this.algorithm;

    }

    /**

     * Returns a {@code KeyGenerator} object that generates secret keys

     * for the specified algorithm.

     *

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

     * starting with the most preferred Provider.

     * A new KeyGenerator object encapsulating the

     * KeyGeneratorSpi implementation from the first

     * 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 standard name of the requested key algorithm.

     * See the KeyGenerator section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#keygenerator-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @return the new {@code KeyGenerator} object

     *

     * @throws NoSuchAlgorithmException if no {@code Provider} supports a

     *         {@code KeyGeneratorSpi} implementation for the

     *         specified algorithm

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see java.security.Provider

     */

    public static final KeyGenerator getInstance(String algorithm)

            throws NoSuchAlgorithmException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        return new KeyGenerator(algorithm);

    }

    /**

     * Returns a {@code KeyGenerator} object that generates secret keys

     * for the specified algorithm.

     *

     * <p> A new KeyGenerator object encapsulating the

     * KeyGeneratorSpi implementation from the specified provider

     * 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 standard name of the requested key algorithm.

     * See the KeyGenerator section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#keygenerator-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the name of the provider.

     *

     * @return the new {@code KeyGenerator} object

     *

     * @throws IllegalArgumentException if the {@code provider}

     *         is {@code null} or empty

     *

     * @throws NoSuchAlgorithmException if a {@code KeyGeneratorSpi}

     *         implementation for the specified algorithm is not

     *         available from the specified provider

     *

     * @throws NoSuchProviderException if the specified provider is not

     *         registered in the security provider list

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see java.security.Provider

     */

    public static final KeyGenerator getInstance(String algorithm,

            String provider) throws NoSuchAlgorithmException,

            NoSuchProviderException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        Instance instance = JceSecurity.getInstance("KeyGenerator",

                KeyGeneratorSpi.class, algorithm, provider);

        return new KeyGenerator((KeyGeneratorSpi)instance.impl,

                instance.provider, algorithm);

    }

    /**

     * Returns a {@code KeyGenerator} object that generates secret keys

     * for the specified algorithm.

     *

     * <p> A new KeyGenerator object encapsulating the

     * KeyGeneratorSpi implementation from the specified Provider

     * object is returned.  Note that the specified Provider object

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

     *

     * @param algorithm the standard name of the requested key algorithm.

     * See the KeyGenerator section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#keygenerator-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the provider.

     *

     * @return the new {@code KeyGenerator} object

     *

     * @throws IllegalArgumentException if the {@code provider}

     *         is {@code null}

     *

     * @throws NoSuchAlgorithmException if a {@code KeyGeneratorSpi}

     *         implementation for the specified algorithm is not available

     *         from the specified {@code Provider} object

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see java.security.Provider

     */

    public static final KeyGenerator getInstance(String algorithm,

            Provider provider) throws NoSuchAlgorithmException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        Instance instance = JceSecurity.getInstance("KeyGenerator",

                KeyGeneratorSpi.class, algorithm, provider);

        return new KeyGenerator((KeyGeneratorSpi)instance.impl,

                instance.provider, algorithm);

    }

    /**

     * Returns the provider of this {@code KeyGenerator} object.

     *

     * @return the provider of this {@code KeyGenerator} object

     */

    public final Provider getProvider() {

        synchronized (lock) {

            disableFailover();

            return provider;

        }

    }

    /**

     * Update the active spi of this class and return the next

     * implementation for failover. If no more implementations are

     * available, this method returns null. However, the active spi of

     * this class is never set to null.

     */

    private KeyGeneratorSpi nextSpi(KeyGeneratorSpi oldSpi,

            boolean reinit) {

        synchronized (lock) {

            // somebody else did a failover concurrently

            // try that spi now

            if ((oldSpi != null) && (oldSpi != spi)) {

                return spi;

            }

            if (serviceIterator == null) {

                return null;

            }

            while (serviceIterator.hasNext()) {

                Service s = serviceIterator.next();

                if (JceSecurity.canUseProvider(s.getProvider()) == false) {

                    continue;

                }

                try {

                    Object inst = s.newInstance(null);

                    // ignore non-spis

                    if (inst instanceof KeyGeneratorSpi == false) {

                        continue;

                    }

                    KeyGeneratorSpi spi = (KeyGeneratorSpi)inst;

                    if (reinit) {

                        if (initType == I_SIZE) {

                            spi.engineInit(initKeySize, initRandom);

                        } else if (initType == I_PARAMS) {

                            spi.engineInit(initParams, initRandom);

                        } else if (initType == I_RANDOM) {

                            spi.engineInit(initRandom);

                        } else if (initType != I_NONE) {

                            throw new AssertionError

                                ("KeyGenerator initType: " + initType);

                        }

                    }

                    provider = s.getProvider();

                    this.spi = spi;

                    return spi;

                } catch (Exception e) {

                    // ignore

                }

            }

            disableFailover();

            return null;

        }

    }

    void disableFailover() {

        serviceIterator = null;

        initType = 0;

        initParams = null;

        initRandom = null;

    }

    /**

     * Initializes this key generator.

     *

     * @param random the source of randomness for this generator

     */

    public final void init(SecureRandom random) {

        if (serviceIterator == null) {

            spi.engineInit(random);

            return;

        }

        RuntimeException failure = null;

        KeyGeneratorSpi mySpi = spi;

        do {

            try {

                mySpi.engineInit(random);

                initType = I_RANDOM;

                initKeySize = 0;

                initParams = null;

                initRandom = random;

                return;

            } catch (RuntimeException e) {

                if (failure == null) {

                    failure = e;

                }

                mySpi = nextSpi(mySpi, false);

            }

        } while (mySpi != null);

        throw failure;

    }

    /**

     * Initializes this key generator with the specified parameter set.

     *

     * <p> If this key generator requires any random bytes, it will get them

     * using the

     * {@link java.security.SecureRandom}

     * implementation of the highest-priority installed

     * provider as the source of randomness.

     * (If none of the installed providers supply an implementation of

     * SecureRandom, a system-provided source of randomness will be used.)

     *

     * @param params the key generation parameters

     *

     * @exception InvalidAlgorithmParameterException if the given parameters

     * are inappropriate for this key generator

     */

    public final void init(AlgorithmParameterSpec params)

        throws InvalidAlgorithmParameterException

    {

        init(params, JceSecurity.RANDOM);

    }

    /**

     * Initializes this key generator with the specified parameter

     * set and a user-provided source of randomness.

     *

     * @param params the key generation parameters

     * @param random the source of randomness for this key generator

     *

     * @exception InvalidAlgorithmParameterException if {@code params} is

     * inappropriate for this key generator

     */

    public final void init(AlgorithmParameterSpec params, SecureRandom random)

        throws InvalidAlgorithmParameterException

    {

        if (serviceIterator == null) {

            spi.engineInit(params, random);

            return;

        }

        Exception failure = null;

        KeyGeneratorSpi mySpi = spi;

        do {

            try {

                mySpi.engineInit(params, random);

                initType = I_PARAMS;

                initKeySize = 0;

                initParams = params;

                initRandom = random;

                return;

            } catch (Exception e) {

                if (failure == null) {

                    failure = e;

                }

                mySpi = nextSpi(mySpi, false);

            }

        } while (mySpi != null);

        if (failure instanceof InvalidAlgorithmParameterException) {

            throw (InvalidAlgorithmParameterException)failure;

        }

        if (failure instanceof RuntimeException) {

            throw (RuntimeException)failure;

        }

        throw new InvalidAlgorithmParameterException("init() failed", failure);

    }

    /**

     * Initializes this key generator for a certain keysize.

     *

     * <p> If this key generator requires any random bytes, it will get them

     * using the

     * {@link java.security.SecureRandom}

     * implementation of the highest-priority installed

     * provider as the source of randomness.

     * (If none of the installed providers supply an implementation of

     * SecureRandom, a system-provided source of randomness will be used.)

     *

     * @param keysize the keysize. This is an algorithm-specific metric,

     * specified in number of bits.

     *

     * @exception InvalidParameterException if the keysize is wrong or not

     * supported.