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	/*
	* Copyright (c) 1999, 2013, 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 javax.crypto;

	import java.security.AlgorithmParameters;
	import java.security.Provider;
	import java.security.Key;
	import java.security.Security;
	import java.security.NoSuchAlgorithmException;
	import java.security.NoSuchProviderException;
	import java.security.InvalidKeyException;
	import java.security.InvalidAlgorithmParameterException;
	import java.security.spec.AlgorithmParameterSpec;

	import sun.security.jca.GetInstance.Instance;

	/**
	* This class provides the functionality of an exemption mechanism, examples
	* of which are <i>key recovery</i>, <i>key weakening</i>, and
	* <i>key escrow</i>.
	*
	* <p>Applications or applets that use an exemption mechanism may be granted
	* stronger encryption capabilities than those which don't.
	*
	* @since 1.4
	*/

	public class ExemptionMechanism {

	// The provider
	private Provider provider;

	// The provider implementation (delegate)
	private ExemptionMechanismSpi exmechSpi;

	// The name of the exemption mechanism.
	private String mechanism;

	// Flag which indicates whether this ExemptionMechanism
	// result is generated successfully.
	private boolean done = false;

	// State information
	private boolean initialized = false;

	// Store away the key at init() time for later comparison.
	private Key keyStored = null;

	/**
	* Creates a ExemptionMechanism object.
	*
	* @param exmechSpi the delegate
	* @param provider the provider
	* @param mechanism the exemption mechanism
	*/
	protected ExemptionMechanism(ExemptionMechanismSpi exmechSpi,
	Provider provider,
	String mechanism) {
	this.exmechSpi = exmechSpi;
	this.provider = provider;
	this.mechanism = mechanism;
	}

	/**
	* Returns the exemption mechanism name of this
	* <code>ExemptionMechanism</code> object.
	*
	* <p>This is the same name that was specified in one of the
	* <code>getInstance</code> calls that created this
	* <code>ExemptionMechanism</code> object.
	*
	* @return the exemption mechanism name of this
	* <code>ExemptionMechanism</code> object.
	*/
	public final String getName() {
	return this.mechanism;
	}

	/**
	* Returns an <code>ExemptionMechanism</code> object that implements the
	* specified exemption mechanism algorithm.
	*
	* <p> This method traverses the list of registered security Providers,
	* starting with the most preferred Provider.
	* A new ExemptionMechanism object encapsulating the
	* ExemptionMechanismSpi 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 name of the requested exemption
	* mechanism.
	* See the ExemptionMechanism section in the
	* <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Exemption">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard exemption mechanism names.
	*
	* @return the new <code>ExemptionMechanism</code> object.
	*
	* @exception NullPointerException if <code>algorithm</code>
	* is null.
	*
	* @exception NoSuchAlgorithmException if no Provider supports an
	* ExemptionMechanismSpi implementation for the
	* specified algorithm.
	*
	* @see java.security.Provider
	*/
	public static final ExemptionMechanism getInstance(String algorithm)
	throws NoSuchAlgorithmException {
	Instance instance = JceSecurity.getInstance("ExemptionMechanism",
	ExemptionMechanismSpi.class, algorithm);
	return new ExemptionMechanism((ExemptionMechanismSpi)instance.impl,
	instance.provider, algorithm);
	}


	/**
	* Returns an <code>ExemptionMechanism</code> object that implements the
	* specified exemption mechanism algorithm.
	*
	* <p> A new ExemptionMechanism object encapsulating the
	* ExemptionMechanismSpi 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 exemption mechanism.
	* See the ExemptionMechanism section in the
	* <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Exemption">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard exemption mechanism names.
	*
	* @param provider the name of the provider.
	*
	* @return the new <code>ExemptionMechanism</code> object.
	*
	* @exception NullPointerException if <code>algorithm</code>
	* is null.
	*
	* @exception NoSuchAlgorithmException if an ExemptionMechanismSpi
	* 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 <code>provider</code>
	* is null or empty.
	*
	* @see java.security.Provider
	*/
	public static final ExemptionMechanism getInstance(String algorithm,
	String provider) throws NoSuchAlgorithmException,
	NoSuchProviderException {
	Instance instance = JceSecurity.getInstance("ExemptionMechanism",
	ExemptionMechanismSpi.class, algorithm, provider);
	return new ExemptionMechanism((ExemptionMechanismSpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns an <code>ExemptionMechanism</code> object that implements the
	* specified exemption mechanism algorithm.
	*
	* <p> A new ExemptionMechanism object encapsulating the
	* ExemptionMechanismSpi 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 exemption mechanism.
	* See the ExemptionMechanism section in the
	* <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Exemption">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard exemption mechanism names.
	*
	* @param provider the provider.
	*
	* @return the new <code>ExemptionMechanism</code> object.
	*
	* @exception NullPointerException if <code>algorithm</code>
	* is null.
	*
	* @exception NoSuchAlgorithmException if an ExemptionMechanismSpi
	* implementation for the specified algorithm is not available
	* from the specified Provider object.
	*
	* @exception IllegalArgumentException if the <code>provider</code>
	* is null.
	*
	* @see java.security.Provider
	*/
	public static final ExemptionMechanism getInstance(String algorithm,
	Provider provider) throws NoSuchAlgorithmException {
	Instance instance = JceSecurity.getInstance("ExemptionMechanism",
	ExemptionMechanismSpi.class, algorithm, provider);
	return new ExemptionMechanism((ExemptionMechanismSpi)instance.impl,
	instance.provider, algorithm);
	}

	/**
	* Returns the provider of this <code>ExemptionMechanism</code> object.
	*
	* @return the provider of this <code>ExemptionMechanism</code> object.
	*/
	public final Provider getProvider() {
	return this.provider;
	}

	/**
	* Returns whether the result blob has been generated successfully by this
	* exemption mechanism.
	*
	* <p>The method also makes sure that the key passed in is the same as
	* the one this exemption mechanism used in initializing and generating
	* phases.
	*
	* @param key the key the crypto is going to use.
	*
	* @return whether the result blob of the same key has been generated
	* successfully by this exemption mechanism; false if <code>key</code>
	* is null.
	*
	* @exception ExemptionMechanismException if problem(s) encountered
	* while determining whether the result blob has been generated successfully
	* by this exemption mechanism object.
	*/
	public final boolean isCryptoAllowed(Key key)
	throws ExemptionMechanismException {
	boolean ret = false;
	if (done && (key != null)) {
	// Check if the key passed in is the same as the one
	// this exemption mechanism used.
	ret = keyStored.equals(key);
	}
	return ret;
	}

	/**
	* Returns the length in bytes that an output buffer would need to be in
	* order to hold the result of the next
	* {@link #genExemptionBlob(byte[]) genExemptionBlob}
	* operation, given the input length <code>inputLen</code> (in bytes).
	*
	* <p>The actual output length of the next
	* {@link #genExemptionBlob(byte[]) genExemptionBlob}
	* call may be smaller than the length returned by this method.
	*
	* @param inputLen the input length (in bytes)
	*
	* @return the required output buffer size (in bytes)
	*
	* @exception IllegalStateException if this exemption mechanism is in a
	* wrong state (e.g., has not yet been initialized)
	*/
	public final int getOutputSize(int inputLen) throws IllegalStateException {
	if (!initialized) {
	throw new IllegalStateException(
	"ExemptionMechanism not initialized");
	}
	if (inputLen < 0) {
	throw new IllegalArgumentException(
	"Input size must be equal to " + "or greater than zero");
	}
	return exmechSpi.engineGetOutputSize(inputLen);
	}

	/**
	* Initializes this exemption mechanism with a key.
	*
	* <p>If this exemption mechanism requires any algorithm parameters
	* that cannot be derived from the given <code>key</code>, the
	* underlying exemption mechanism implementation is supposed to
	* generate the required parameters itself (using provider-specific
	* default values); in the case that algorithm parameters must be
	* specified by the caller, an <code>InvalidKeyException</code> is raised.
	*
	* @param key the key for this exemption mechanism
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* this exemption mechanism.
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of initializing.
	*/
	public final void init(Key key)
	throws InvalidKeyException, ExemptionMechanismException {
	done = false;
	initialized = false;

	keyStored = key;
	exmechSpi.engineInit(key);
	initialized = true;
	}

	/**
	* Initializes this exemption mechanism with a key and a set of algorithm
	* parameters.
	*
	* <p>If this exemption mechanism requires any algorithm parameters
	* and <code>params</code> is null, the underlying exemption
	* mechanism implementation is supposed to generate the required
	* parameters itself (using provider-specific default values); in the case
	* that algorithm parameters must be specified by the caller, an
	* <code>InvalidAlgorithmParameterException</code> is raised.
	*
	* @param key the key for this exemption mechanism
	* @param params the algorithm parameters
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* this exemption mechanism.
	* @exception InvalidAlgorithmParameterException if the given algorithm
	* parameters are inappropriate for this exemption mechanism.
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of initializing.
	*/
	public final void init(Key key, AlgorithmParameterSpec params)
	throws InvalidKeyException, InvalidAlgorithmParameterException,
	ExemptionMechanismException {
	done = false;
	initialized = false;

	keyStored = key;
	exmechSpi.engineInit(key, params);
	initialized = true;
	}

	/**
	* Initializes this exemption mechanism with a key and a set of algorithm
	* parameters.
	*
	* <p>If this exemption mechanism requires any algorithm parameters
	* and <code>params</code> is null, the underlying exemption mechanism
	* implementation is supposed to generate the required parameters itself
	* (using provider-specific default values); in the case that algorithm
	* parameters must be specified by the caller, an
	* <code>InvalidAlgorithmParameterException</code> is raised.
	*
	* @param key the key for this exemption mechanism
	* @param params the algorithm parameters
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* this exemption mechanism.
	* @exception InvalidAlgorithmParameterException if the given algorithm
	* parameters are inappropriate for this exemption mechanism.
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of initializing.
	*/
	public final void init(Key key, AlgorithmParameters params)
	throws InvalidKeyException, InvalidAlgorithmParameterException,
	ExemptionMechanismException {
	done = false;
	initialized = false;

	keyStored = key;
	exmechSpi.engineInit(key, params);
	initialized = true;
	}

	/**
	* Generates the exemption mechanism key blob.
	*
	* @return the new buffer with the result key blob.
	*
	* @exception IllegalStateException if this exemption mechanism is in
	* a wrong state (e.g., has not been initialized).
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of generating.
	*/
	public final byte[] genExemptionBlob() throws IllegalStateException,
	ExemptionMechanismException {
	if (!initialized) {
	throw new IllegalStateException(
	"ExemptionMechanism not initialized");
	}
	byte[] blob = exmechSpi.engineGenExemptionBlob();
	done = true;
	return blob;
	}

	/**
	* Generates the exemption mechanism key blob, and stores the result in
	* the <code>output</code> buffer.
	*
	* <p>If the <code>output</code> buffer is too small to hold the result,
	* a <code>ShortBufferException</code> is thrown. In this case, repeat this
	* call with a larger output buffer. Use
	* {@link #getOutputSize(int) getOutputSize} to determine how big
	* the output buffer should be.
	*
	* @param output the buffer for the result
	*
	* @return the number of bytes stored in <code>output</code>
	*
	* @exception IllegalStateException if this exemption mechanism is in
	* a wrong state (e.g., has not been initialized).
	* @exception ShortBufferException if the given output buffer is too small
	* to hold the result.
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of generating.
	*/
	public final int genExemptionBlob(byte[] output)
	throws IllegalStateException, ShortBufferException,
	ExemptionMechanismException {
	if (!initialized) {
	throw new IllegalStateException
	("ExemptionMechanism not initialized");
	}
	int n = exmechSpi.engineGenExemptionBlob(output, 0);
	done = true;
	return n;
	}

	/**
	* Generates the exemption mechanism key blob, and stores the result in
	* the <code>output</code> buffer, starting at <code>outputOffset</code>
	* inclusive.
	*
	* <p>If the <code>output</code> buffer is too small to hold the result,
	* a <code>ShortBufferException</code> is thrown. In this case, repeat this
	* call with a larger output buffer. Use
	* {@link #getOutputSize(int) getOutputSize} to determine how big
	* the output buffer should be.
	*
	* @param output the buffer for the result
	* @param outputOffset the offset in <code>output</code> where the result
	* is stored
	*
	* @return the number of bytes stored in <code>output</code>
	*
	* @exception IllegalStateException if this exemption mechanism is in
	* a wrong state (e.g., has not been initialized).
	* @exception ShortBufferException if the given output buffer is too small
	* to hold the result.
	* @exception ExemptionMechanismException if problem(s) encountered in the
	* process of generating.
	*/
	public final int genExemptionBlob(byte[] output, int outputOffset)
	throws IllegalStateException, ShortBufferException,
	ExemptionMechanismException {
	if (!initialized) {
	throw new IllegalStateException
	("ExemptionMechanism not initialized");
	}
	int n = exmechSpi.engineGenExemptionBlob(output, outputOffset);
	done = true;
	return n;
	}

	/**
	* Ensures that the key stored away by this ExemptionMechanism
	* object will be wiped out when there are no more references to it.
	*/
	protected void finalize() {
	keyStored = null;
	// Are there anything else we could do?
	}
	}

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