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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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,

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 *

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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., SHA256 or SHA384, 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 HmacSHA1}</li>

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

 * </ul>

 * These algorithms are described in the

 * <a href="{@docRoot}/../specs/security/standard-names.html#mac-algorithms">

 * Mac 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

 *

 * @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}/../specs/security/standard-names.html#mac-algorithms">

     * Java Security Standard Algorithm Names Specification</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}/../specs/security/standard-names.html#mac-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 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}/../specs/security/standard-names.html#mac-algorithms">

     * Java Security Standard Algorithm Names Specification</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.