/*
 * Copyright (c) 1998, 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
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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 HmacMD5}</li>
 * <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.
 *
 * @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;
 }
}