/*
 * @(#)KeyPairGenerator.java	1.59 06/04/21
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
 
package java.security;

import java.util.*;

import java.security.spec.AlgorithmParameterSpec;

import java.security.Provider.Service;

import sun.security.jca.*;
import sun.security.jca.GetInstance.Instance;

/**
 * The KeyPairGenerator class is used to generate pairs of
 * public and private keys. Key pair generators are constructed using the
 * <code>getInstance</code> factory methods (static methods that
 * return instances of a given class).
 *
 * <p>A Key pair generator for a particular algorithm creates a public/private
 * key pair that can be used with this algorithm. It also associates
 * algorithm-specific parameters with each of the generated keys.
 * 
 * <p>There are two ways to generate a key pair: 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 pair generators share the concepts of a keysize and a
 * source of randomness. The keysize is interpreted differently for different
 * algorithms (e.g., in the case of the <i>DSA</i> algorithm, the keysize 
 * corresponds to the length of the modulus).
 * There is an 
 * {@link #initialize(int, java.security.SecureRandom) initialize}
 * method in this KeyPairGenerator class that takes these two universally
 * shared types of arguments. There is also one that takes just a
 * <code>keysize</code> argument, and uses the <code>SecureRandom</code>
 * implementation of the highest-priority installed provider as the source
 * of randomness. (If none of the installed providers supply an implementation
 * of <code>SecureRandom</code>, a system-provided source of randomness is
 * used.)
 * 
 * <p>Since no other parameters are specified when you call the above
 * algorithm-independent <code>initialize</code> 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.
 * 
 * <p>If the algorithm is the <i>DSA</i> algorithm, and the keysize (modulus
 * size) is 512, 768, or 1024, then the <i>Sun</i> provider uses a set of
 * precomputed values for the <code>p</code>, <code>q</code>, and
 * <code>g</code> parameters. If the modulus size is not one of the above
 * values, the <i>Sun</i> provider creates a new set of parameters. Other
 * providers might have precomputed parameter sets for more than just the
 * three modulus sizes mentioned above. Still others might not have a list of
 * precomputed parameters at all and instead always create new parameter sets.
 * <p>
 *
 * <li><b>Algorithm-Specific Initialization</b>
 * <p>For situations where a set of algorithm-specific parameters already
 * exists (e.g., so-called <i>community parameters</i> in DSA), there are two
 * {@link #initialize(java.security.spec.AlgorithmParameterSpec)
 * initialize} methods that have an <code>AlgorithmParameterSpec</code>
 * argument. One also has a <code>SecureRandom</code> argument, while the
 * the other uses the <code>SecureRandom</code>
 * implementation of the highest-priority installed provider as the source
 * of randomness. (If none of the installed providers supply an implementation
 * of <code>SecureRandom</code>, a system-provided source of randomness is
 * used.)
 * </ul>
 *
 * <p>In case the client does not explicitly initialize the KeyPairGenerator
 * (via a call to an <code>initialize</code> method), each provider must
 * supply (and document) a default initialization.
 * For example, the <i>Sun</i> provider uses a default modulus size (keysize)
 * of 1024 bits.
 *
 * <p>Note that this class is abstract and extends from
 * <code>KeyPairGeneratorSpi</code> for historical reasons.
 * Application developers should only take notice of the methods defined in
 * this <code>KeyPairGenerator</code> class; all the methods in
 * the superclass are intended for cryptographic service providers who wish to
 * supply their own implementations of key pair generators.
 *
 * @author Benjamin Renaud
 *
 * @version 1.59, 04/21/06
 *
 * @see java.security.spec.AlgorithmParameterSpec
 */

public abstract class KeyPairGenerator extends KeyPairGeneratorSpi {

    private final String algorithm;

    // The provider
    Provider provider;

    /**
     * Creates a KeyPairGenerator object for the specified algorithm.
     *
     * @param algorithm the standard string name of the algorithm. 
     * See Appendix A in the <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     */
    protected KeyPairGenerator(String algorithm) {
	this.algorithm = algorithm;
    }
    
    /**
     * Returns the standard name of the algorithm for this key pair generator.
     * See Appendix A in the <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     * 
     * @return the standard string name of the algorithm. 
     */
    public String getAlgorithm() {
	return this.algorithm;
    }

    private static KeyPairGenerator getInstance(Instance instance, 
	    String algorithm) {
	KeyPairGenerator kpg;
	if (instance.impl instanceof KeyPairGenerator) {
	    kpg = (KeyPairGenerator)instance.impl;
	} else {
	    KeyPairGeneratorSpi spi = (KeyPairGeneratorSpi)instance.impl;
	    kpg = new Delegate(spi, algorithm);
	}
	kpg.provider = instance.provider;
	return kpg;
    }

    /**
     * Returns a KeyPairGenerator object that generates public/private
     * key pairs for the specified algorithm.
     *
     * <p> This method traverses the list of registered security Providers,
     * starting with the most preferred Provider.
     * A new KeyPairGenerator object encapsulating the
     * KeyPairGeneratorSpi 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.
     *
     * @param algorithm the standard string name of the algorithm. 
     * See Appendix A in the <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @return the new KeyPairGenerator object.
     *
     * @exception NoSuchAlgorithmException if no Provider supports a
     *          KeyPairGeneratorSpi implementation for the
     *          specified algorithm.
     *
     * @see Provider
     */
    public static KeyPairGenerator getInstance(String algorithm)
	    throws NoSuchAlgorithmException {
	List<Service> list = 
		GetInstance.getServices("KeyPairGenerator", algorithm);
	Iterator<Service> t = list.iterator();
	if (t.hasNext() == false) {
	    throw new NoSuchAlgorithmException
	    	(algorithm + " KeyPairGenerator not available");
	}
	// find a working Spi or KeyPairGenerator subclass
	NoSuchAlgorithmException failure = null;
	do {
	    Service s = t.next();
	    try {
		Instance instance = 
		    GetInstance.getInstance(s, KeyPairGeneratorSpi.class);
		if (instance.impl instanceof KeyPairGenerator) {
		    return getInstance(instance, algorithm);
		} else {
		    return new Delegate(instance, t, algorithm);
		}
	    } catch (NoSuchAlgorithmException e) {
		if (failure == null) {
		    failure = e;
		}
	    }
	} while (t.hasNext());
	throw failure;
    }

    /** 
     * Returns a KeyPairGenerator object that generates public/private
     * key pairs for the specified algorithm.
     *
     * <p> A new KeyPairGenerator object encapsulating the
     * KeyPairGeneratorSpi 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 string name of the algorithm.
     * See Appendix A in the <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @param provider the string name of the provider.
     *
     * @return the new KeyPairGenerator object.
     *
     * @exception NoSuchAlgorithmException if a KeyPairGeneratorSpi
     *          implementation for the specified algorithm is not
     *          available from the specified provider.
     *
     * @exception NoSuchProviderException if the specified provider is not
     *          registered in the security provider list.
     *
     * @exception IllegalArgumentException if the provider name is null
     *		or empty.
     * 
     * @see Provider 
     */
    public static KeyPairGenerator getInstance(String algorithm,
	    String provider) 
	    throws NoSuchAlgorithmException, NoSuchProviderException {
	Instance instance = GetInstance.getInstance("KeyPairGenerator", 
		KeyPairGeneratorSpi.class, algorithm, provider);
	return getInstance(instance, algorithm);
    }

    /** 
     * Returns a KeyPairGenerator object that generates public/private
     * key pairs for the specified algorithm.
     *
     * <p> A new KeyPairGenerator object encapsulating the
     * KeyPairGeneratorSpi 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 string name of the algorithm.
     * See Appendix A in the <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @param provider the provider.
     *
     * @return the new KeyPairGenerator object.
     *
     * @exception NoSuchAlgorithmException if a KeyPairGeneratorSpi
     *          implementation for the specified algorithm is not available
     *          from the specified Provider object.
     *
     * @exception IllegalArgumentException if the specified provider is null.
     *
     * @see Provider
     *
     * @since 1.4
     */
    public static KeyPairGenerator getInstance(String algorithm,
	    Provider provider) throws NoSuchAlgorithmException {
	Instance instance = GetInstance.getInstance("KeyPairGenerator", 
		KeyPairGeneratorSpi.class, algorithm, provider);
	return getInstance(instance, algorithm);
    }

    /** 
     * Returns the provider of this key pair generator object.
     * 
     * @return the provider of this key pair generator object
     */
    public final Provider getProvider() {
	disableFailover();
	return this.provider;
    }
    
    void disableFailover() {
	// empty, overridden in Delegate
    }

    /**
     * Initializes the key pair generator for a certain keysize using
     * a default parameter set and the <code>SecureRandom</code>
     * implementation of the highest-priority installed provider as the source
     * of randomness.
     * (If none of the installed providers supply an implementation of
     * <code>SecureRandom</code>, a system-provided source of randomness is
     * used.)
     *
     * @param keysize the keysize. This is an
     * algorithm-specific metric, such as modulus length, specified in
     * number of bits.
     *
     * @exception InvalidParameterException if the <code>keysize</code> is not
     * supported by this KeyPairGenerator object.
     */
    public void initialize(int keysize) {
	initialize(keysize, JCAUtil.getSecureRandom());
    }

    /**
     * Initializes the key pair generator for a certain keysize with
     * the given source of randomness (and a default parameter set).
     *
     * @param keysize the keysize. This is an
     * algorithm-specific metric, such as modulus length, specified in
     * number of bits.
     * @param random the source of randomness.
     *
     * @exception InvalidParameterException if the <code>keysize</code> is not
     * supported by this KeyPairGenerator object.
     *
     * @since 1.2
     */
    public void initialize(int keysize, SecureRandom random) {
	// This does nothing, because either
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own 
	//    initialize(keysize, random) method, so the application would
	//    be calling that method directly, or
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case initialize(keysize, random) is
	//    overridden to call the corresponding SPI method.
	// (This is a special case, because the API and SPI method have the
	// same name.)
    }

    /**
     * Initializes the key pair generator using the specified parameter 
     * set and the <code>SecureRandom</code>
     * implementation of the highest-priority installed provider as the source
     * of randomness.
     * (If none of the installed providers supply an implementation of
     * <code>SecureRandom</code>, a system-provided source of randomness is
     * used.).
     *
     * <p>This concrete method has been added to this previously-defined
     * abstract class.
     * This method calls the KeyPairGeneratorSpi 
     * {@link KeyPairGeneratorSpi#initialize(
     * java.security.spec.AlgorithmParameterSpec,
     * java.security.SecureRandom) initialize} method, 
     * passing it <code>params</code> and a source of randomness (obtained
     * from the highest-priority installed provider or system-provided if none
     * of the installed providers supply one).
     * That <code>initialize</code> method always throws an
     * UnsupportedOperationException if it is not overridden by the provider.
     *
     * @param params the parameter set used to generate the keys.
     *
     * @exception InvalidAlgorithmParameterException if the given parameters
     * are inappropriate for this key pair generator.
     *
     * @since 1.2
     */
    public void initialize(AlgorithmParameterSpec params)
	    throws InvalidAlgorithmParameterException {
	initialize(params, JCAUtil.getSecureRandom());
    }

    /**
     * Initializes the key pair generator with the given parameter 
     * set and source of randomness.
     *
     * <p>This concrete method has been added to this previously-defined
     * abstract class.
     * This method calls the KeyPairGeneratorSpi {@link 
     * KeyPairGeneratorSpi#initialize(
     * java.security.spec.AlgorithmParameterSpec,
     * java.security.SecureRandom) initialize} method, 
     * passing it <code>params</code> and <code>random</code>.
     * That <code>initialize</code>
     * method always throws an
     * UnsupportedOperationException if it is not overridden by the provider.
     *
     * @param params the parameter set used to generate the keys.
     * @param random the source of randomness.
     *
     * @exception InvalidAlgorithmParameterException if the given parameters
     * are inappropriate for this key pair generator.
     *
     * @since 1.2
     */
    public void initialize(AlgorithmParameterSpec params,
			   SecureRandom random)
	throws InvalidAlgorithmParameterException
    {
	// This does nothing, because either
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own 
	//    initialize(params, random) method, so the application would
	//    be calling that method directly, or
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case initialize(params, random) is
	//    overridden to call the corresponding SPI method.
	// (This is a special case, because the API and SPI method have the
	// same name.)
    }

    /**
     * Generates a key pair.
     *
     * <p>If this KeyPairGenerator has not been initialized explicitly,
     * provider-specific defaults will be used for the size and other
     * (algorithm-specific) values of the generated keys.
     *
     * <p>This will generate a new key pair every time it is called.
     *
     * <p>This method is functionally equivalent to 
     * {@link #generateKeyPair() generateKeyPair}.
     *
     * @return the generated key pair
     *
     * @since 1.2
     */
    public final KeyPair genKeyPair() {
	return generateKeyPair();
    }

    /**
     * Generates a key pair.
     *
     * <p>If this KeyPairGenerator has not been initialized explicitly,
     * provider-specific defaults will be used for the size and other
     * (algorithm-specific) values of the generated keys.
     *
     * <p>This will generate a new key pair every time it is called.
     * 
     * <p>This method is functionally equivalent to 
     * {@link #genKeyPair() genKeyPair}.
     *
     * @return the generated key pair
     */
    public KeyPair generateKeyPair() {
	// This does nothing (except returning null), because either:
	//
	// 1. the implementation object returned by getInstance() is an
	//    instance of KeyPairGenerator which has its own implementation
	//    of generateKeyPair (overriding this one), so the application
	//    would be calling that method directly, or
	//
	// 2. the implementation returned by getInstance() is an instance
	//    of Delegate, in which case generateKeyPair is
	//    overridden to invoke the corresponding SPI method.
	//
	// (This is a special case, because in JDK 1.1.x the generateKeyPair
	// method was used both as an API and a SPI method.)
        return null;
    }


    /*
     * The following class allows providers to extend from KeyPairGeneratorSpi
     * rather than from KeyPairGenerator. It represents a KeyPairGenerator
     * with an encapsulated, provider-supplied SPI object (of type
     * KeyPairGeneratorSpi).
     * If the provider implementation is an instance of KeyPairGeneratorSpi,
     * the getInstance() methods above return an instance of this class, with
     * the SPI object encapsulated.
     *
     * Note: All SPI methods from the original KeyPairGenerator class have been
     * moved up the hierarchy into a new class (KeyPairGeneratorSpi), which has
     * been interposed in the hierarchy between the API (KeyPairGenerator)
     * and its original parent (Object).
     */
     
    //
    // error failover notes:
    //
    //  . we failover if the implementation throws an error during init
    //    by retrying the init on other providers
    //
    //  . we also failover if the init succeeded but the subsequent call
    //    to generateKeyPair() fails. In order for this to work, we need
    //    to remember the parameters to the last successful call to init
    //    and initialize() the next spi using them.
    //
    //  . although not specified, KeyPairGenerators could be thread safe,
    //    so we make sure we do not interfere with that
    //
    //  . failover is not available, if:
    //    . getInstance(algorithm, provider) was used
    //    . a provider extends KeyPairGenerator rather than
    //      KeyPairGeneratorSpi (JDK 1.1 style)
    //    . once getProvider() is called
    //

    private static final class Delegate extends KeyPairGenerator {

	// The provider implementation (delegate)
	private volatile KeyPairGeneratorSpi spi;
	
	private final Object lock = new Object();
	
	private Iterator<Service> serviceIterator;
	
	private final static int I_NONE   = 1;
	private final static int I_SIZE   = 2;
	private final static int I_PARAMS = 3;
	
	private int initType;
	private int initKeySize;
	private AlgorithmParameterSpec initParams;
	private SecureRandom initRandom;

	// constructor
	Delegate(KeyPairGeneratorSpi spi, String algorithm) {
	    super(algorithm);
	    this.spi = spi;
	}
	
	Delegate(Instance instance, Iterator<Service> serviceIterator, 
		String algorithm) {
	    super(algorithm);
	    spi = (KeyPairGeneratorSpi)instance.impl;
	    provider = instance.provider;
	    this.serviceIterator = serviceIterator;
	    initType = I_NONE;
	}
	
	/**
	 * Update the active spi of this class and return the next
	 * implementation for failover. If no more implemenations are
	 * available, this method returns null. However, the active spi of
	 * this class is never set to null.
	 */
	private KeyPairGeneratorSpi nextSpi(KeyPairGeneratorSpi 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();
		    try {
			Object inst = s.newInstance(null);
			// ignore non-spis
			if (inst instanceof KeyPairGeneratorSpi == false) {
			    continue;
			}
			if (inst instanceof KeyPairGenerator) {
			    continue;
			}
			KeyPairGeneratorSpi spi = (KeyPairGeneratorSpi)inst;
			if (reinit) {
			    if (initType == I_SIZE) {
				spi.initialize(initKeySize, initRandom);
			    } else if (initType == I_PARAMS) {
				spi.initialize(initParams, initRandom);
			    } else if (initType != I_NONE) {
				throw new AssertionError
				    ("KeyPairGenerator 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;
	}

	// engine method
	public void initialize(int keysize, SecureRandom random) {
	    if (serviceIterator == null) {
		spi.initialize(keysize, random);
		return;
	    }
	    RuntimeException failure = null;
	    KeyPairGeneratorSpi mySpi = spi;
	    do {
		try {
		    mySpi.initialize(keysize, random);
		    initType = I_SIZE;
		    initKeySize = keysize;
		    initParams = null;
		    initRandom = random;
		    return;
		} catch (RuntimeException e) {
		    if (failure == null) {
			failure = e;
		    }
		    mySpi = nextSpi(mySpi, false);
		}
	    } while (mySpi != null);
	    throw failure;
	}

	// engine method
	public void initialize(AlgorithmParameterSpec params,
		SecureRandom random) throws InvalidAlgorithmParameterException {
	    if (serviceIterator == null) {
		spi.initialize(params, random);
		return;
	    }
	    Exception failure = null;
	    KeyPairGeneratorSpi mySpi = spi;
	    do {
		try {
		    mySpi.initialize(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 RuntimeException) {
		throw (RuntimeException)failure;
	    }
	    // must be an InvalidAlgorithmParameterException
	    throw (InvalidAlgorithmParameterException)failure;
	}

	// engine method
	public KeyPair generateKeyPair() {
	    if (serviceIterator == null) {
		return spi.generateKeyPair();
	    }
	    RuntimeException failure = null;
	    KeyPairGeneratorSpi mySpi = spi;
	    do {
		try {
		    return mySpi.generateKeyPair();
		} catch (RuntimeException e) {
		    if (failure == null) {
			failure = e;
		    }
		    mySpi = nextSpi(mySpi, true);
		}
	    } while (mySpi != null);
	    throw failure;
	}
    }

}