jdk/src/java.base/share/classes/javax/crypto/Mac.java - platform/libcore - Git at Google

 /*
  * Copyright (c) 1998, 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,
  * 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.util.*;

 import java.security.*;
 import java.security.Provider.Service;
 import java.security.spec.AlgorithmParameterSpec;

 import java.nio.ByteBuffer;

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

 /**
  * This class provides the functionality of a "Message Authentication Code"
  * (MAC) algorithm.
  *
  * <p> A MAC provides a way to check
  * the integrity of information transmitted over or stored in an unreliable
  * medium, based on a secret key. Typically, message
  * authentication codes are used between two parties that share a secret
  * key in order to validate information transmitted between these
  * parties.
  *
  * <p> A MAC mechanism that is based on cryptographic hash functions is
  * referred to as HMAC. HMAC can be used with any cryptographic hash function,
  * e.g., MD5 or SHA-1, in combination with a secret shared key. HMAC is
  * specified in RFC 2104.
  *
  * <p> Every implementation of the Java platform is required to support
  * the following standard {@code Mac} algorithms:
  * <ul>
  * <li>{@code HmacMD5}</li>
  * <li>{@code HmacSHA1}</li>
  * <li>{@code HmacSHA256}</li>
  * </ul>
  * These algorithms are described in the
  * <a href="{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
  * Mac section</a> of the
  * Java Cryptography Architecture Standard Algorithm Name Documentation.
  * Consult the release documentation for your implementation to see if any
  * other algorithms are supported.
  *
  * @author Jan Luehe
  *
  * @since 1.4
  */

 public class Mac implements Cloneable {

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

     private static final Debug pdebug =
                         Debug.getInstance("provider", "Provider");
     private static final boolean skipDebug =
         Debug.isOn("engine=") && !Debug.isOn("mac");

     // The provider
     private Provider provider;

     // The provider implementation (delegate)
     private MacSpi spi;

     // The name of the MAC algorithm.
     private final String algorithm;

     // Has this object been initialized?
     private boolean initialized = false;

     // next service to try in provider selection
     // null once provider is selected
     private Service firstService;

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

     private final Object lock;

     /**
      * Creates a MAC object.
      *
      * @param macSpi the delegate
      * @param provider the provider
      * @param algorithm the algorithm
      */
     protected Mac(MacSpi macSpi, Provider provider, String algorithm) {
         this.spi = macSpi;
         this.provider = provider;
         this.algorithm = algorithm;
         serviceIterator = null;
         lock = null;
     }

     private Mac(Service s, Iterator<Service> t, String algorithm) {
         firstService = s;
         serviceIterator = t;
         this.algorithm = algorithm;
         lock = new Object();
     }

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

     /**
      * Returns a {@code Mac} object that implements the
      * specified MAC algorithm.
      *
      * <p> This method traverses the list of registered security Providers,
      * starting with the most preferred Provider.
      * A new Mac object encapsulating the
      * MacSpi 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 MAC algorithm.
      * See the Mac section in the <a href=
      *   "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
      * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
      * for information about standard algorithm names.
      *
      * @return the new {@code Mac} object
      *
      * @throws NoSuchAlgorithmException if no {@code Provider} supports a
      *         {@code MacSpi} implementation for the specified algorithm
      *
      * @throws NullPointerException if {@code algorithm} is {@code null}
      *
      * @see java.security.Provider
      */
     public static final Mac getInstance(String algorithm)
             throws NoSuchAlgorithmException {
         Objects.requireNonNull(algorithm, "null algorithm name");
         List<Service> services = GetInstance.getServices("Mac", algorithm);
         // make sure there is at least one service from a signed provider
         Iterator<Service> t = services.iterator();
         while (t.hasNext()) {
             Service s = t.next();
             if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                 continue;
             }
             return new Mac(s, t, algorithm);
         }
         throw new NoSuchAlgorithmException
                                 ("Algorithm " + algorithm + " not available");
     }

     /**
      * Returns a {@code Mac} object that implements the
      * specified MAC algorithm.
      *
      * <p> A new Mac object encapsulating the
      * MacSpi 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 MAC algorithm.
      * See the Mac section in the <a href=
      *   "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
      * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
      * for information about standard algorithm names.
      *
      * @param provider the name of the provider.
      *
      * @return the new {@code Mac} object
      *
      * @throws IllegalArgumentException if the {@code provider}
      *         is {@code null} or empty
      *
      * @throws NoSuchAlgorithmException if a {@code MacSpi}
      *         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 Mac getInstance(String algorithm, String provider)
             throws NoSuchAlgorithmException, NoSuchProviderException {
         Objects.requireNonNull(algorithm, "null algorithm name");
         Instance instance = JceSecurity.getInstance
                 ("Mac", MacSpi.class, algorithm, provider);
         return new Mac((MacSpi)instance.impl, instance.provider, algorithm);
     }

     /**
      * Returns a {@code Mac} object that implements the
      * specified MAC algorithm.
      *
      * <p> A new Mac object encapsulating the
      * MacSpi 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 MAC algorithm.
      * See the Mac section in the <a href=
      *   "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
      * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
      * for information about standard algorithm names.
      *
      * @param provider the provider.
      *
      * @return the new {@code Mac} object
      *
      * @throws IllegalArgumentException if the {@code provider} is
      *         {@code null}
      *
      * @throws NoSuchAlgorithmException if a {@code MacSpi}
      *         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 Mac getInstance(String algorithm, Provider provider)
             throws NoSuchAlgorithmException {
         Objects.requireNonNull(algorithm, "null algorithm name");
         Instance instance = JceSecurity.getInstance
                 ("Mac", MacSpi.class, algorithm, provider);
         return new Mac((MacSpi)instance.impl, instance.provider, algorithm);
     }

     // max number of debug warnings to print from chooseFirstProvider()
     private static int warnCount = 10;

     /**
      * Choose the Spi from the first provider available. Used if
      * delayed provider selection is not possible because init()
      * is not the first method called.
      */
     void chooseFirstProvider() {
         if ((spi != null) || (serviceIterator == null)) {
             return;
         }
         synchronized (lock) {
             if (spi != null) {
                 return;
             }
             if (debug != null) {
                 int w = --warnCount;
                 if (w >= 0) {
                     debug.println("Mac.init() not first method "
                         + "called, disabling delayed provider selection");
                     if (w == 0) {
                         debug.println("Further warnings of this type will "
                             + "be suppressed");
                     }
                     new Exception("Call trace").printStackTrace();
                 }
             }
             Exception lastException = null;
             while ((firstService != null) || serviceIterator.hasNext()) {
                 Service s;
                 if (firstService != null) {
                     s = firstService;
                     firstService = null;
                 } else {
                     s = serviceIterator.next();
                 }
                 if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                     continue;
                 }
                 try {
                     Object obj = s.newInstance(null);
                     if (obj instanceof MacSpi == false) {
                         continue;
                     }
                     spi = (MacSpi)obj;
                     provider = s.getProvider();
                     // not needed any more
                     firstService = null;
                     serviceIterator = null;
                     return;
                 } catch (NoSuchAlgorithmException e) {
                     lastException = e;
                 }
             }
             ProviderException e = new ProviderException
                     ("Could not construct MacSpi instance");
             if (lastException != null) {
                 e.initCause(lastException);
             }
             throw e;
         }
     }

     private void chooseProvider(Key key, AlgorithmParameterSpec params)
             throws InvalidKeyException, InvalidAlgorithmParameterException {
         synchronized (lock) {
             if (spi != null) {
                 spi.engineInit(key, params);
                 return;
             }
             Exception lastException = null;
             while ((firstService != null) || serviceIterator.hasNext()) {
                 Service s;
                 if (firstService != null) {
                     s = firstService;
                     firstService = null;
                 } else {
                     s = serviceIterator.next();
                 }
                 // if provider says it does not support this key, ignore it
                 if (s.supportsParameter(key) == false) {
                     continue;
                 }
                 if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                     continue;
                 }
                 try {
                     MacSpi spi = (MacSpi)s.newInstance(null);
                     spi.engineInit(key, params);
                     provider = s.getProvider();
                     this.spi = spi;
                     firstService = null;
                     serviceIterator = null;
                     return;
                 } catch (Exception e) {
                     // NoSuchAlgorithmException from newInstance()
                     // InvalidKeyException from init()
                     // RuntimeException (ProviderException) from init()
                     if (lastException == null) {
                         lastException = e;
                     }
                 }
             }
             // no working provider found, fail
             if (lastException instanceof InvalidKeyException) {
                 throw (InvalidKeyException)lastException;
             }
             if (lastException instanceof InvalidAlgorithmParameterException) {
                 throw (InvalidAlgorithmParameterException)lastException;
             }
             if (lastException instanceof RuntimeException) {
                 throw (RuntimeException)lastException;
             }
             String kName = (key != null) ? key.getClass().getName() : "(null)";
             throw new InvalidKeyException
                 ("No installed provider supports this key: "
                 + kName, lastException);
         }
     }

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

     /**
      * Returns the length of the MAC in bytes.
      *
      * @return the MAC length in bytes.
      */
     public final int getMacLength() {
         chooseFirstProvider();
         return spi.engineGetMacLength();
     }

     private String getProviderName() {
         return (provider == null) ? "(no provider)" : provider.getName();
     }

     /**
      * Initializes this {@code Mac} object with the given key.
      *
      * @param key the key.
      *
      * @exception InvalidKeyException if the given key is inappropriate for
      * initializing this MAC.
      */
     public final void init(Key key) throws InvalidKeyException {
         try {
             if (spi != null) {
                 spi.engineInit(key, null);
             } else {
                 chooseProvider(key, null);
             }
         } catch (InvalidAlgorithmParameterException e) {
             throw new InvalidKeyException("init() failed", e);
         }
         initialized = true;

         if (!skipDebug && pdebug != null) {
             pdebug.println("Mac." + algorithm + " algorithm from: " +
                 getProviderName());
         }
     }

     /**
      * Initializes this {@code Mac} object with the given key and
      * algorithm parameters.
      *
      * @param key the key.
      * @param params the algorithm parameters.
      *
      * @exception InvalidKeyException if the given key is inappropriate for
      * initializing this MAC.
      * @exception InvalidAlgorithmParameterException if the given algorithm
      * parameters are inappropriate for this MAC.
      */
     public final void init(Key key, AlgorithmParameterSpec params)
             throws InvalidKeyException, InvalidAlgorithmParameterException {
         if (spi != null) {
             spi.engineInit(key, params);
         } else {
             chooseProvider(key, params);
         }
         initialized = true;

         if (!skipDebug && pdebug != null) {
             pdebug.println("Mac." + algorithm + " algorithm from: " +
                 getProviderName());
         }
     }

     /**
      * Processes the given byte.
      *
      * @param input the input byte to be processed.
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final void update(byte input) throws IllegalStateException {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         spi.engineUpdate(input);
     }

     /**
      * Processes the given array of bytes.
      *
      * @param input the array of bytes to be processed.
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final void update(byte[] input) throws IllegalStateException {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         if (input != null) {
             spi.engineUpdate(input, 0, input.length);
         }
     }

     /**
      * Processes the first {@code len} bytes in {@code input},
      * starting at {@code offset} inclusive.
      *
      * @param input the input buffer.
      * @param offset the offset in {@code input} where the input starts.
      * @param len the number of bytes to process.
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final void update(byte[] input, int offset, int len)
             throws IllegalStateException {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }

         if (input != null) {
             if ((offset < 0) || (len > (input.length - offset)) || (len < 0))
                 throw new IllegalArgumentException("Bad arguments");
             spi.engineUpdate(input, offset, len);
         }
     }

     /**
      * Processes {@code input.remaining()} bytes in the ByteBuffer
      * {@code input}, starting at {@code input.position()}.
      * Upon return, the buffer's position will be equal to its limit;
      * its limit will not have changed.
      *
      * @param input the ByteBuffer
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      * @since 1.5
      */
     public final void update(ByteBuffer input) {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         if (input == null) {
             throw new IllegalArgumentException("Buffer must not be null");
         }
         spi.engineUpdate(input);
     }

     /**
      * Finishes the MAC operation.
      *
      * <p>A call to this method resets this {@code Mac} object to the
      * state it was in when previously initialized via a call to
      * {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      * That is, the object is reset and available to generate another MAC from
      * the same key, if desired, via new calls to {@code update} and
      * {@code doFinal}.
      * (In order to reuse this {@code Mac} object with a different key,
      * it must be reinitialized via a call to {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      *
      * @return the MAC result.
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final byte[] doFinal() throws IllegalStateException {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         byte[] mac = spi.engineDoFinal();
         spi.engineReset();
         return mac;
     }

     /**
      * Finishes the MAC operation.
      *
      * <p>A call to this method resets this {@code Mac} object to the
      * state it was in when previously initialized via a call to
      * {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      * That is, the object is reset and available to generate another MAC from
      * the same key, if desired, via new calls to {@code update} and
      * {@code doFinal}.
      * (In order to reuse this {@code Mac} object with a different key,
      * it must be reinitialized via a call to {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      *
      * <p>The MAC result is stored in {@code output}, starting at
      * {@code outOffset} inclusive.
      *
      * @param output the buffer where the MAC result is stored
      * @param outOffset the offset in {@code output} where the MAC is
      * stored
      *
      * @exception ShortBufferException if the given output buffer is too small
      * to hold the result
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final void doFinal(byte[] output, int outOffset)
         throws ShortBufferException, IllegalStateException
     {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         int macLen = getMacLength();
         if (output == null || output.length-outOffset < macLen) {
             throw new ShortBufferException
                 ("Cannot store MAC in output buffer");
         }
         byte[] mac = doFinal();
         System.arraycopy(mac, 0, output, outOffset, macLen);
         return;
     }

     /**
      * Processes the given array of bytes and finishes the MAC operation.
      *
      * <p>A call to this method resets this {@code Mac} object to the
      * state it was in when previously initialized via a call to
      * {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      * That is, the object is reset and available to generate another MAC from
      * the same key, if desired, via new calls to {@code update} and
      * {@code doFinal}.
      * (In order to reuse this {@code Mac} object with a different key,
      * it must be reinitialized via a call to {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      *
      * @param input data in bytes
      * @return the MAC result.
      *
      * @exception IllegalStateException if this {@code Mac} has not been
      * initialized.
      */
     public final byte[] doFinal(byte[] input) throws IllegalStateException
     {
         chooseFirstProvider();
         if (initialized == false) {
             throw new IllegalStateException("MAC not initialized");
         }
         update(input);
         return doFinal();
     }

     /**
      * Resets this {@code Mac} object.
      *
      * <p>A call to this method resets this {@code Mac} object to the
      * state it was in when previously initialized via a call to
      * {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      * That is, the object is reset and available to generate another MAC from
      * the same key, if desired, via new calls to {@code update} and
      * {@code doFinal}.
      * (In order to reuse this {@code Mac} object with a different key,
      * it must be reinitialized via a call to {@code init(Key)} or
      * {@code init(Key, AlgorithmParameterSpec)}.
      */
     public final void reset() {
         chooseFirstProvider();
         spi.engineReset();
     }

     /**
      * Returns a clone if the provider implementation is cloneable.
      *
      * @return a clone if the provider implementation is cloneable.
      *
      * @exception CloneNotSupportedException if this is called on a
      * delegate that does not support {@code Cloneable}.
      */
     public final Object clone() throws CloneNotSupportedException {
         chooseFirstProvider();
         Mac that = (Mac)super.clone();
         that.spi = (MacSpi)this.spi.clone();
         return that;
     }
 }
	/*
	* Copyright (c) 1998, 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,
	* 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.util.*;

	import java.security.*;
	import java.security.Provider.Service;
	import java.security.spec.AlgorithmParameterSpec;

	import java.nio.ByteBuffer;

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

	/**
	* This class provides the functionality of a "Message Authentication Code"
	* (MAC) algorithm.
	*
	* <p> A MAC provides a way to check
	* the integrity of information transmitted over or stored in an unreliable
	* medium, based on a secret key. Typically, message
	* authentication codes are used between two parties that share a secret
	* key in order to validate information transmitted between these
	* parties.
	*
	* <p> A MAC mechanism that is based on cryptographic hash functions is
	* referred to as HMAC. HMAC can be used with any cryptographic hash function,
	* e.g., MD5 or SHA-1, in combination with a secret shared key. HMAC is
	* specified in RFC 2104.
	*
	* <p> Every implementation of the Java platform is required to support
	* the following standard {@code Mac} algorithms:
	* <ul>
	* <li>{@code HmacMD5}</li>
	* <li>{@code HmacSHA1}</li>
	* <li>{@code HmacSHA256}</li>
	* </ul>
	* These algorithms are described in the
	* <a href="{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
	* Mac section</a> of the
	* Java Cryptography Architecture Standard Algorithm Name Documentation.
	* Consult the release documentation for your implementation to see if any
	* other algorithms are supported.
	*
	* @author Jan Luehe
	*
	* @since 1.4
	*/

	public class Mac implements Cloneable {

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

	private static final Debug pdebug =
	Debug.getInstance("provider", "Provider");
	private static final boolean skipDebug =
	Debug.isOn("engine=") && !Debug.isOn("mac");

	// The provider
	private Provider provider;

	// The provider implementation (delegate)
	private MacSpi spi;

	// The name of the MAC algorithm.
	private final String algorithm;

	// Has this object been initialized?
	private boolean initialized = false;

	// next service to try in provider selection
	// null once provider is selected
	private Service firstService;

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

	private final Object lock;

	/**
	* Creates a MAC object.
	*
	* @param macSpi the delegate
	* @param provider the provider
	* @param algorithm the algorithm
	*/
	protected Mac(MacSpi macSpi, Provider provider, String algorithm) {
	this.spi = macSpi;
	this.provider = provider;
	this.algorithm = algorithm;
	serviceIterator = null;
	lock = null;
	}

	private Mac(Service s, Iterator<Service> t, String algorithm) {
	firstService = s;
	serviceIterator = t;
	this.algorithm = algorithm;
	lock = new Object();
	}

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

	/**
	* Returns a {@code Mac} object that implements the
	* specified MAC algorithm.
	*
	* <p> This method traverses the list of registered security Providers,
	* starting with the most preferred Provider.
	* A new Mac object encapsulating the
	* MacSpi 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 MAC algorithm.
	* See the Mac section in the <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard algorithm names.
	*
	* @return the new {@code Mac} object
	*
	* @throws NoSuchAlgorithmException if no {@code Provider} supports a
	* {@code MacSpi} implementation for the specified algorithm
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see java.security.Provider
	*/
	public static final Mac getInstance(String algorithm)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	List<Service> services = GetInstance.getServices("Mac", algorithm);
	// make sure there is at least one service from a signed provider
	Iterator<Service> t = services.iterator();
	while (t.hasNext()) {
	Service s = t.next();
	if (JceSecurity.canUseProvider(s.getProvider()) == false) {
	continue;
	}
	return new Mac(s, t, algorithm);
	}
	throw new NoSuchAlgorithmException
	("Algorithm " + algorithm + " not available");
	}

	/**
	* Returns a {@code Mac} object that implements the
	* specified MAC algorithm.
	*
	* <p> A new Mac object encapsulating the
	* MacSpi 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 MAC algorithm.
	* See the Mac section in the <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard algorithm names.
	*
	* @param provider the name of the provider.
	*
	* @return the new {@code Mac} object
	*
	* @throws IllegalArgumentException if the {@code provider}
	* is {@code null} or empty
	*
	* @throws NoSuchAlgorithmException if a {@code MacSpi}
	* 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 Mac getInstance(String algorithm, String provider)
	throws NoSuchAlgorithmException, NoSuchProviderException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = JceSecurity.getInstance
	("Mac", MacSpi.class, algorithm, provider);
	return new Mac((MacSpi)instance.impl, instance.provider, algorithm);
	}

	/**
	* Returns a {@code Mac} object that implements the
	* specified MAC algorithm.
	*
	* <p> A new Mac object encapsulating the
	* MacSpi 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 MAC algorithm.
	* See the Mac section in the <a href=
	* "{@docRoot}/../technotes/guides/security/StandardNames.html#Mac">
	* Java Cryptography Architecture Standard Algorithm Name Documentation</a>
	* for information about standard algorithm names.
	*
	* @param provider the provider.
	*
	* @return the new {@code Mac} object
	*
	* @throws IllegalArgumentException if the {@code provider} is
	* {@code null}
	*
	* @throws NoSuchAlgorithmException if a {@code MacSpi}
	* 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 Mac getInstance(String algorithm, Provider provider)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	Instance instance = JceSecurity.getInstance
	("Mac", MacSpi.class, algorithm, provider);
	return new Mac((MacSpi)instance.impl, instance.provider, algorithm);
	}

	// max number of debug warnings to print from chooseFirstProvider()
	private static int warnCount = 10;

	/**
	* Choose the Spi from the first provider available. Used if
	* delayed provider selection is not possible because init()
	* is not the first method called.
	*/
	void chooseFirstProvider() {
	if ((spi != null) \|\| (serviceIterator == null)) {
	return;
	}
	synchronized (lock) {
	if (spi != null) {
	return;
	}
	if (debug != null) {
	int w = --warnCount;
	if (w >= 0) {
	debug.println("Mac.init() not first method "
	+ "called, disabling delayed provider selection");
	if (w == 0) {
	debug.println("Further warnings of this type will "
	+ "be suppressed");
	}
	new Exception("Call trace").printStackTrace();
	}
	}
	Exception lastException = null;
	while ((firstService != null) \|\| serviceIterator.hasNext()) {
	Service s;
	if (firstService != null) {
	s = firstService;
	firstService = null;
	} else {
	s = serviceIterator.next();
	}
	if (JceSecurity.canUseProvider(s.getProvider()) == false) {
	continue;
	}
	try {
	Object obj = s.newInstance(null);
	if (obj instanceof MacSpi == false) {
	continue;
	}
	spi = (MacSpi)obj;
	provider = s.getProvider();
	// not needed any more
	firstService = null;
	serviceIterator = null;
	return;
	} catch (NoSuchAlgorithmException e) {
	lastException = e;
	}
	}
	ProviderException e = new ProviderException
	("Could not construct MacSpi instance");
	if (lastException != null) {
	e.initCause(lastException);
	}
	throw e;
	}
	}

	private void chooseProvider(Key key, AlgorithmParameterSpec params)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	synchronized (lock) {
	if (spi != null) {
	spi.engineInit(key, params);
	return;
	}
	Exception lastException = null;
	while ((firstService != null) \|\| serviceIterator.hasNext()) {
	Service s;
	if (firstService != null) {
	s = firstService;
	firstService = null;
	} else {
	s = serviceIterator.next();
	}
	// if provider says it does not support this key, ignore it
	if (s.supportsParameter(key) == false) {
	continue;
	}
	if (JceSecurity.canUseProvider(s.getProvider()) == false) {
	continue;
	}
	try {
	MacSpi spi = (MacSpi)s.newInstance(null);
	spi.engineInit(key, params);
	provider = s.getProvider();
	this.spi = spi;
	firstService = null;
	serviceIterator = null;
	return;
	} catch (Exception e) {
	// NoSuchAlgorithmException from newInstance()
	// InvalidKeyException from init()
	// RuntimeException (ProviderException) from init()
	if (lastException == null) {
	lastException = e;
	}
	}
	}
	// no working provider found, fail
	if (lastException instanceof InvalidKeyException) {
	throw (InvalidKeyException)lastException;
	}
	if (lastException instanceof InvalidAlgorithmParameterException) {
	throw (InvalidAlgorithmParameterException)lastException;
	}
	if (lastException instanceof RuntimeException) {
	throw (RuntimeException)lastException;
	}
	String kName = (key != null) ? key.getClass().getName() : "(null)";
	throw new InvalidKeyException
	("No installed provider supports this key: "
	+ kName, lastException);
	}
	}

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

	/**
	* Returns the length of the MAC in bytes.
	*
	* @return the MAC length in bytes.
	*/
	public final int getMacLength() {
	chooseFirstProvider();
	return spi.engineGetMacLength();
	}

	private String getProviderName() {
	return (provider == null) ? "(no provider)" : provider.getName();
	}

	/**
	* Initializes this {@code Mac} object with the given key.
	*
	* @param key the key.
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this MAC.
	*/
	public final void init(Key key) throws InvalidKeyException {
	try {
	if (spi != null) {
	spi.engineInit(key, null);
	} else {
	chooseProvider(key, null);
	}
	} catch (InvalidAlgorithmParameterException e) {
	throw new InvalidKeyException("init() failed", e);
	}
	initialized = true;

	if (!skipDebug && pdebug != null) {
	pdebug.println("Mac." + algorithm + " algorithm from: " +
	getProviderName());
	}
	}

	/**
	* Initializes this {@code Mac} object with the given key and
	* algorithm parameters.
	*
	* @param key the key.
	* @param params the algorithm parameters.
	*
	* @exception InvalidKeyException if the given key is inappropriate for
	* initializing this MAC.
	* @exception InvalidAlgorithmParameterException if the given algorithm
	* parameters are inappropriate for this MAC.
	*/
	public final void init(Key key, AlgorithmParameterSpec params)
	throws InvalidKeyException, InvalidAlgorithmParameterException {
	if (spi != null) {
	spi.engineInit(key, params);
	} else {
	chooseProvider(key, params);
	}
	initialized = true;

	if (!skipDebug && pdebug != null) {
	pdebug.println("Mac." + algorithm + " algorithm from: " +
	getProviderName());
	}
	}

	/**
	* Processes the given byte.
	*
	* @param input the input byte to be processed.
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final void update(byte input) throws IllegalStateException {
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	spi.engineUpdate(input);
	}

	/**
	* Processes the given array of bytes.
	*
	* @param input the array of bytes to be processed.
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final void update(byte[] input) throws IllegalStateException {
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	if (input != null) {
	spi.engineUpdate(input, 0, input.length);
	}
	}

	/**
	* Processes the first {@code len} bytes in {@code input},
	* starting at {@code offset} inclusive.
	*
	* @param input the input buffer.
	* @param offset the offset in {@code input} where the input starts.
	* @param len the number of bytes to process.
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final void update(byte[] input, int offset, int len)
	throws IllegalStateException {
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}

	if (input != null) {
	if ((offset < 0) \|\| (len > (input.length - offset)) \|\| (len < 0))
	throw new IllegalArgumentException("Bad arguments");
	spi.engineUpdate(input, offset, len);
	}
	}

	/**
	* Processes {@code input.remaining()} bytes in the ByteBuffer
	* {@code input}, starting at {@code input.position()}.
	* Upon return, the buffer's position will be equal to its limit;
	* its limit will not have changed.
	*
	* @param input the ByteBuffer
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	* @since 1.5
	*/
	public final void update(ByteBuffer input) {
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	if (input == null) {
	throw new IllegalArgumentException("Buffer must not be null");
	}
	spi.engineUpdate(input);
	}

	/**
	* Finishes the MAC operation.
	*
	* <p>A call to this method resets this {@code Mac} object to the
	* state it was in when previously initialized via a call to
	* {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	* That is, the object is reset and available to generate another MAC from
	* the same key, if desired, via new calls to {@code update} and
	* {@code doFinal}.
	* (In order to reuse this {@code Mac} object with a different key,
	* it must be reinitialized via a call to {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	*
	* @return the MAC result.
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final byte[] doFinal() throws IllegalStateException {
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	byte[] mac = spi.engineDoFinal();
	spi.engineReset();
	return mac;
	}

	/**
	* Finishes the MAC operation.
	*
	* <p>A call to this method resets this {@code Mac} object to the
	* state it was in when previously initialized via a call to
	* {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	* That is, the object is reset and available to generate another MAC from
	* the same key, if desired, via new calls to {@code update} and
	* {@code doFinal}.
	* (In order to reuse this {@code Mac} object with a different key,
	* it must be reinitialized via a call to {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	*
	* <p>The MAC result is stored in {@code output}, starting at
	* {@code outOffset} inclusive.
	*
	* @param output the buffer where the MAC result is stored
	* @param outOffset the offset in {@code output} where the MAC is
	* stored
	*
	* @exception ShortBufferException if the given output buffer is too small
	* to hold the result
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final void doFinal(byte[] output, int outOffset)
	throws ShortBufferException, IllegalStateException
	{
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	int macLen = getMacLength();
	if (output == null \|\| output.length-outOffset < macLen) {
	throw new ShortBufferException
	("Cannot store MAC in output buffer");
	}
	byte[] mac = doFinal();
	System.arraycopy(mac, 0, output, outOffset, macLen);
	return;
	}

	/**
	* Processes the given array of bytes and finishes the MAC operation.
	*
	* <p>A call to this method resets this {@code Mac} object to the
	* state it was in when previously initialized via a call to
	* {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	* That is, the object is reset and available to generate another MAC from
	* the same key, if desired, via new calls to {@code update} and
	* {@code doFinal}.
	* (In order to reuse this {@code Mac} object with a different key,
	* it must be reinitialized via a call to {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	*
	* @param input data in bytes
	* @return the MAC result.
	*
	* @exception IllegalStateException if this {@code Mac} has not been
	* initialized.
	*/
	public final byte[] doFinal(byte[] input) throws IllegalStateException
	{
	chooseFirstProvider();
	if (initialized == false) {
	throw new IllegalStateException("MAC not initialized");
	}
	update(input);
	return doFinal();
	}

	/**
	* Resets this {@code Mac} object.
	*
	* <p>A call to this method resets this {@code Mac} object to the
	* state it was in when previously initialized via a call to
	* {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	* That is, the object is reset and available to generate another MAC from
	* the same key, if desired, via new calls to {@code update} and
	* {@code doFinal}.
	* (In order to reuse this {@code Mac} object with a different key,
	* it must be reinitialized via a call to {@code init(Key)} or
	* {@code init(Key, AlgorithmParameterSpec)}.
	*/
	public final void reset() {
	chooseFirstProvider();
	spi.engineReset();
	}

	/**
	* Returns a clone if the provider implementation is cloneable.
	*
	* @return a clone if the provider implementation is cloneable.
	*
	* @exception CloneNotSupportedException if this is called on a
	* delegate that does not support {@code Cloneable}.
	*/
	public final Object clone() throws CloneNotSupportedException {
	chooseFirstProvider();
	Mac that = (Mac)super.clone();
	that.spi = (MacSpi)this.spi.clone();
	return that;
	}
	}