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	/*
	* Copyright (c) 1997, 2017, 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,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.security;

	import java.util.*;

	import java.security.Provider.Service;
	import java.security.spec.KeySpec;
	import java.security.spec.InvalidKeySpecException;

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

	/**
	* Key factories are used to convert <I>keys</I> (opaque
	* cryptographic keys of type {@code Key}) into <I>key specifications</I>
	* (transparent representations of the underlying key material), and vice
	* versa.
	*
	* <P> Key factories are bi-directional. That is, they allow you to build an
	* opaque key object from a given key specification (key material), or to
	* retrieve the underlying key material of a key object in a suitable format.
	*
	* <P> Multiple compatible key specifications may exist for the same key.
	* For example, a DSA public key may be specified using
	* {@code DSAPublicKeySpec} or
	* {@code X509EncodedKeySpec}. A key factory can be used to translate
	* between compatible key specifications.
	*
	* <P> The following is an example of how to use a key factory in order to
	* instantiate a DSA public key from its encoding.
	* Assume Alice has received a digital signature from Bob.
	* Bob also sent her his public key (in encoded format) to verify
	* his signature. Alice then performs the following actions:
	*
	* <pre>
	* X509EncodedKeySpec bobPubKeySpec = new X509EncodedKeySpec(bobEncodedPubKey);
	* KeyFactory keyFactory = KeyFactory.getInstance("DSA");
	* PublicKey bobPubKey = keyFactory.generatePublic(bobPubKeySpec);
	* Signature sig = Signature.getInstance("DSA");
	* sig.initVerify(bobPubKey);
	* sig.update(data);
	* sig.verify(signature);
	* </pre>
	*
	* <p> Every implementation of the Java platform is required to support the
	* following standard {@code KeyFactory} algorithms:
	* <ul>
	* <li>{@code DiffieHellman}</li>
	* <li>{@code DSA}</li>
	* <li>{@code RSA}</li>
	* </ul>
	* These algorithms are described in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#keyfactory-algorithms">
	* KeyFactory 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 Key
	* @see PublicKey
	* @see PrivateKey
	* @see java.security.spec.KeySpec
	* @see java.security.spec.DSAPublicKeySpec
	* @see java.security.spec.X509EncodedKeySpec
	*
	* @since 1.2
	*/

	public class KeyFactory {

	private static final Debug debug =
	Debug.getInstance("jca", "KeyFactory");

	// The algorithm associated with this key factory
	private final String algorithm;

	// The provider
	private Provider provider;

	// The provider implementation (delegate)
	private volatile KeyFactorySpi spi;

	// lock for mutex during provider selection
	private final Object lock = new Object();

	// remaining services to try in provider selection
	// null once provider is selected
	private Iterator<Service> serviceIterator;

	/**
	* Creates a KeyFactory object.
	*
	* @param keyFacSpi the delegate
	* @param provider the provider
	* @param algorithm the name of the algorithm
	* to associate with this {@code KeyFactory}
	*/
	protected KeyFactory(KeyFactorySpi keyFacSpi, Provider provider,
	String algorithm) {
	this.spi = keyFacSpi;
	this.provider = provider;
	this.algorithm = algorithm;
	}

	private KeyFactory(String algorithm) throws NoSuchAlgorithmException {
	this.algorithm = algorithm;
	List<Service> list = GetInstance.getServices("KeyFactory", algorithm);
	serviceIterator = list.iterator();
	// fetch and instantiate initial spi
	if (nextSpi(null) == null) {
	throw new NoSuchAlgorithmException
	(algorithm + " KeyFactory not available");
	}
	}

	/**
	* Returns a KeyFactory object that converts
	* public/private keys of the specified algorithm.
	*
	* <p> This method traverses the list of registered security Providers,
	* starting with the most preferred Provider.
	* A new KeyFactory object encapsulating the
	* KeyFactorySpi 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 name of the requested key algorithm.
	* See the KeyFactory section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#keyfactory-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @return the new {@code KeyFactory} object
	*
	* @throws NoSuchAlgorithmException if no {@code Provider} supports a
	* {@code KeyFactorySpi} implementation for the
	* specified algorithm
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see Provider
	*/
	public static KeyFactory getInstance(String algorithm)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	return new KeyFactory(algorithm);
	}

	/**
	* Returns a KeyFactory object that converts
	* public/private keys of the specified algorithm.
	*
	* <p> A new KeyFactory object encapsulating the
	* KeyFactorySpi 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 name of the requested key algorithm.
	* See the KeyFactory section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#keyfactory-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 KeyFactory} object
	*
	* @throws IllegalArgumentException if the provider name is {@code null}
	* or empty
	*
	* @throws NoSuchAlgorithmException if a {@code KeyFactorySpi}
	* 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 Provider
	*/
	public static KeyFactory getInstance(String algorithm, String provider)
	throws NoSuchAlgorithmException, NoSuchProviderException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = GetInstance.getInstance("KeyFactory",
	KeyFactorySpi.class, algorithm, provider);
	return new KeyFactory((KeyFactorySpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns a KeyFactory object that converts
	* public/private keys of the specified algorithm.
	*
	* <p> A new KeyFactory object encapsulating the
	* KeyFactorySpi 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 name of the requested key algorithm.
	* See the KeyFactory section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#keyfactory-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @param provider the provider.
	*
	* @return the new {@code KeyFactory} object
	*
	* @throws IllegalArgumentException if the specified provider is
	* {@code null}
	*
	* @throws NoSuchAlgorithmException if a {@code KeyFactorySpi}
	* implementation for the specified algorithm is not available
	* from the specified {@code Provider} object
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see Provider
	*
	* @since 1.4
	*/
	public static KeyFactory getInstance(String algorithm, Provider provider)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = GetInstance.getInstance("KeyFactory",
	KeyFactorySpi.class, algorithm, provider);
	return new KeyFactory((KeyFactorySpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns the provider of this key factory object.
	*
	* @return the provider of this key factory object
	*/
	public final Provider getProvider() {
	synchronized (lock) {
	// disable further failover after this call
	serviceIterator = null;
	return provider;
	}
	}

	/**
	* Gets the name of the algorithm
	* associated with this {@code KeyFactory}.
	*
	* @return the name of the algorithm associated with this
	* {@code KeyFactory}
	*/
	public final String getAlgorithm() {
	return this.algorithm;
	}

	/**
	* Update the active KeyFactorySpi 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 KeyFactorySpi nextSpi(KeyFactorySpi oldSpi) {
	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 obj = s.newInstance(null);
	if (obj instanceof KeyFactorySpi == false) {
	continue;
	}
	KeyFactorySpi spi = (KeyFactorySpi)obj;
	provider = s.getProvider();
	this.spi = spi;
	return spi;
	} catch (NoSuchAlgorithmException e) {
	// ignore
	}
	}
	serviceIterator = null;
	return null;
	}
	}

	/**
	* Generates a public key object from the provided key specification
	* (key material).
	*
	* @param keySpec the specification (key material) of the public key.
	*
	* @return the public key.
	*
	* @exception InvalidKeySpecException if the given key specification
	* is inappropriate for this key factory to produce a public key.
	*/
	public final PublicKey generatePublic(KeySpec keySpec)
	throws InvalidKeySpecException {
	if (serviceIterator == null) {
	return spi.engineGeneratePublic(keySpec);
	}
	Exception failure = null;
	KeyFactorySpi mySpi = spi;
	do {
	try {
	return mySpi.engineGeneratePublic(keySpec);
	} catch (Exception e) {
	if (failure == null) {
	failure = e;
	}
	mySpi = nextSpi(mySpi);
	}
	} while (mySpi != null);
	if (failure instanceof RuntimeException) {
	throw (RuntimeException)failure;
	}
	if (failure instanceof InvalidKeySpecException) {
	throw (InvalidKeySpecException)failure;
	}
	throw new InvalidKeySpecException
	("Could not generate public key", failure);
	}

	/**
	* Generates a private key object from the provided key specification
	* (key material).
	*
	* @param keySpec the specification (key material) of the private key.
	*
	* @return the private key.
	*
	* @exception InvalidKeySpecException if the given key specification
	* is inappropriate for this key factory to produce a private key.
	*/
	public final PrivateKey generatePrivate(KeySpec keySpec)
	throws InvalidKeySpecException {
	if (serviceIterator == null) {
	return spi.engineGeneratePrivate(keySpec);
	}
	Exception failure = null;
	KeyFactorySpi mySpi = spi;
	do {
	try {
	return mySpi.engineGeneratePrivate(keySpec);
	} catch (Exception e) {
	if (failure == null) {
	failure = e;
	}
	mySpi = nextSpi(mySpi);
	}
	} while (mySpi != null);
	if (failure instanceof RuntimeException) {
	throw (RuntimeException)failure;
	}
	if (failure instanceof InvalidKeySpecException) {
	throw (InvalidKeySpecException)failure;
	}
	throw new InvalidKeySpecException
	("Could not generate private key", failure);
	}

	/**
	* Returns a specification (key material) of the given key object.
	* {@code keySpec} identifies the specification class in which
	* the key material should be returned. It could, for example, be
	* {@code DSAPublicKeySpec.class}, to indicate that the
	* key material should be returned in an instance of the
	* {@code DSAPublicKeySpec} class.
	*
	* @param <T> the type of the key specification to be returned
	*
	* @param key the key.
	*
	* @param keySpec the specification class in which
	* the key material should be returned.
	*
	* @return the underlying key specification (key material) in an instance
	* of the requested specification class.
	*
	* @exception InvalidKeySpecException if the requested key specification is
	* inappropriate for the given key, or the given key cannot be processed
	* (e.g., the given key has an unrecognized algorithm or format).
	*/
	public final <T extends KeySpec> T getKeySpec(Key key, Class<T> keySpec)
	throws InvalidKeySpecException {
	if (serviceIterator == null) {
	return spi.engineGetKeySpec(key, keySpec);
	}
	Exception failure = null;
	KeyFactorySpi mySpi = spi;
	do {
	try {
	return mySpi.engineGetKeySpec(key, keySpec);
	} catch (Exception e) {
	if (failure == null) {
	failure = e;
	}
	mySpi = nextSpi(mySpi);
	}
	} while (mySpi != null);
	if (failure instanceof RuntimeException) {
	throw (RuntimeException)failure;
	}
	if (failure instanceof InvalidKeySpecException) {
	throw (InvalidKeySpecException)failure;
	}
	throw new InvalidKeySpecException
	("Could not get key spec", failure);
	}

	/**
	* Translates a key object, whose provider may be unknown or potentially
	* untrusted, into a corresponding key object of this key factory.
	*
	* @param key the key whose provider is unknown or untrusted.
	*
	* @return the translated key.
	*
	* @exception InvalidKeyException if the given key cannot be processed
	* by this key factory.
	*/
	public final Key translateKey(Key key) throws InvalidKeyException {
	if (serviceIterator == null) {
	return spi.engineTranslateKey(key);
	}
	Exception failure = null;
	KeyFactorySpi mySpi = spi;
	do {
	try {
	return mySpi.engineTranslateKey(key);
	} catch (Exception e) {
	if (failure == null) {
	failure = e;
	}
	mySpi = nextSpi(mySpi);
	}
	} while (mySpi != null);
	if (failure instanceof RuntimeException) {
	throw (RuntimeException)failure;
	}
	if (failure instanceof InvalidKeyException) {
	throw (InvalidKeyException)failure;
	}
	throw new InvalidKeyException
	("Could not translate key", failure);
	}

	}

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