/*
 * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */

package java.security;

import java.util.*;
import java.lang.*;
import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.io.InputStream;
import java.io.ByteArrayInputStream;

import java.nio.ByteBuffer;

import sun.security.util.Debug;

/**
 * This MessageDigest class provides applications the functionality of a
 * message digest algorithm, such as SHA-1 or SHA-256.
 * Message digests are secure one-way hash functions that take arbitrary-sized
 * data and output a fixed-length hash value.
 *
 * <p>A MessageDigest object starts out initialized. The data is
 * processed through it using the {@link #update(byte) update}
 * methods. At any point {@link #reset() reset} can be called
 * to reset the digest. Once all the data to be updated has been
 * updated, one of the {@link #digest() digest} methods should
 * be called to complete the hash computation.
 *
 * <p>The {@code digest} method can be called once for a given number
 * of updates. After {@code digest} has been called, the MessageDigest
 * object is reset to its initialized state.
 *
 * <p>Implementations are free to implement the Cloneable interface.
 * Client applications can test cloneability by attempting cloning
 * and catching the CloneNotSupportedException:
 *
 * <pre>{@code
 * MessageDigest md = MessageDigest.getInstance("SHA-256");
 *
 * try {
 * md.update(toChapter1);
 * MessageDigest tc1 = md.clone();
 * byte[] toChapter1Digest = tc1.digest();
 * md.update(toChapter2);
 * ...etc.
 * } catch (CloneNotSupportedException cnse) {
 * throw new DigestException("couldn't make digest of partial content");
 * }
 * }</pre>
 *
 * <p>Note that if a given implementation is not cloneable, it is
 * still possible to compute intermediate digests by instantiating
 * several instances, if the number of digests is known in advance.
 *
 * <p>Note that this class is abstract and extends from
 * {@code MessageDigestSpi} for historical reasons.
 * Application developers should only take notice of the methods defined in
 * this {@code MessageDigest} class; all the methods in
 * the superclass are intended for cryptographic service providers who wish to
 * supply their own implementations of message digest algorithms.
 *
 * <p> Every implementation of the Java platform is required to support
 * the following standard {@code MessageDigest} algorithms:
 * <ul>
 * <li>{@code MD5}</li>
 * <li>{@code SHA-1}</li>
 * <li>{@code SHA-256}</li>
 * </ul>
 * These algorithms are described in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * MessageDigest 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 Benjamin Renaud
 *
 * @see DigestInputStream
 * @see DigestOutputStream
 */

public abstract class MessageDigest extends MessageDigestSpi {

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

 private String algorithm;

 // The state of this digest
 private static final int INITIAL = 0;
 private static final int IN_PROGRESS = 1;
 private int state = INITIAL;

 // The provider
 private Provider provider;

 /**
 * Creates a message digest with the specified algorithm name.
 *
 * @param algorithm the standard name of the digest algorithm.
 * See the MessageDigest section in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
 * for information about standard algorithm names.
 */
 protected MessageDigest(String algorithm) {
 this.algorithm = algorithm;
 }

 /**
 * Returns a MessageDigest object that implements the specified digest
 * algorithm.
 *
 * <p> This method traverses the list of registered security Providers,
 * starting with the most preferred Provider.
 * A new MessageDigest object encapsulating the
 * MessageDigestSpi 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 name of the algorithm requested.
 * See the MessageDigest section in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
 * for information about standard algorithm names.
 *
 * @return a Message Digest object that implements the specified algorithm.
 *
 * @exception NoSuchAlgorithmException if no Provider supports a
 * MessageDigestSpi implementation for the
 * specified algorithm.
 *
 * @see Provider
 */
 public static MessageDigest getInstance(String algorithm)
 throws NoSuchAlgorithmException {
 try {
 MessageDigest md;
 Object[] objs = Security.getImpl(algorithm, "MessageDigest",
 (String)null);
 if (objs[0] instanceof MessageDigest) {
 md = (MessageDigest)objs[0];
 } else {
 md = new Delegate((MessageDigestSpi)objs[0], algorithm);
 }
 md.provider = (Provider)objs[1];

 if (!skipDebug && pdebug != null) {
 pdebug.println("MessageDigest." + algorithm +
 " algorithm from: " + md.provider.getName());
 }

 return md;

 } catch(NoSuchProviderException e) {
 throw new NoSuchAlgorithmException(algorithm + " not found");
 }
 }

 /**
 * Returns a MessageDigest object that implements the specified digest
 * algorithm.
 *
 * <p> A new MessageDigest object encapsulating the
 * MessageDigestSpi implementation from the specified provider
 * is returned. The specified provider must be registered
 * in the security provider list.
 *
 * <p> Note that the list of registered providers may be retrieved via
 * the {@link Security#getProviders() Security.getProviders()} method.
 *
 * @param algorithm the name of the algorithm requested.
 * See the MessageDigest section in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
 * for information about standard algorithm names.
 *
 * @param provider the name of the provider.
 *
 * @return a MessageDigest object that implements the specified algorithm.
 *
 * @exception NoSuchAlgorithmException if a MessageDigestSpi
 * 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 provider name is null
 * or empty.
 *
 * @see Provider
 */
 public static MessageDigest getInstance(String algorithm, String provider)
 throws NoSuchAlgorithmException, NoSuchProviderException
 {
 if (provider == null || provider.length() == 0)
 throw new IllegalArgumentException("missing provider");
 Object[] objs = Security.getImpl(algorithm, "MessageDigest", provider);
 if (objs[0] instanceof MessageDigest) {
 MessageDigest md = (MessageDigest)objs[0];
 md.provider = (Provider)objs[1];
 return md;
 } else {
 MessageDigest delegate =
 new Delegate((MessageDigestSpi)objs[0], algorithm);
 delegate.provider = (Provider)objs[1];
 return delegate;
 }
 }

 /**
 * Returns a MessageDigest object that implements the specified digest
 * algorithm.
 *
 * <p> A new MessageDigest object encapsulating the
 * MessageDigestSpi implementation from the specified Provider
 * object is returned. Note that the specified Provider object
 * does not have to be registered in the provider list.
 *
 * @param algorithm the name of the algorithm requested.
 * See the MessageDigest section in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
 * for information about standard algorithm names.
 *
 * @param provider the provider.
 *
 * @return a MessageDigest object that implements the specified algorithm.
 *
 * @exception NoSuchAlgorithmException if a MessageDigestSpi
 * implementation for the specified algorithm is not available
 * from the specified Provider object.
 *
 * @exception IllegalArgumentException if the specified provider is null.
 *
 * @see Provider
 *
 * @since 1.4
 */
 public static MessageDigest getInstance(String algorithm,
 Provider provider)
 throws NoSuchAlgorithmException
 {
 if (provider == null)
 throw new IllegalArgumentException("missing provider");
 Object[] objs = Security.getImpl(algorithm, "MessageDigest", provider);
 if (objs[0] instanceof MessageDigest) {
 MessageDigest md = (MessageDigest)objs[0];
 md.provider = (Provider)objs[1];
 return md;
 } else {
 MessageDigest delegate =
 new Delegate((MessageDigestSpi)objs[0], algorithm);
 delegate.provider = (Provider)objs[1];
 return delegate;
 }
 }

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

 /**
 * Updates the digest using the specified byte.
 *
 * @param input the byte with which to update the digest.
 */
 public void update(byte input) {
 engineUpdate(input);
 state = IN_PROGRESS;
 }

 /**
 * Updates the digest using the specified array of bytes, starting
 * at the specified offset.
 *
 * @param input the array of bytes.
 *
 * @param offset the offset to start from in the array of bytes.
 *
 * @param len the number of bytes to use, starting at
 * {@code offset}.
 */
 public void update(byte[] input, int offset, int len) {
 if (input == null) {
 throw new IllegalArgumentException("No input buffer given");
 }
 if (input.length - offset < len) {
 throw new IllegalArgumentException("Input buffer too short");
 }
 engineUpdate(input, offset, len);
 state = IN_PROGRESS;
 }

 /**
 * Updates the digest using the specified array of bytes.
 *
 * @param input the array of bytes.
 */
 public void update(byte[] input) {
 engineUpdate(input, 0, input.length);
 state = IN_PROGRESS;
 }

 /**
 * Update the digest using the specified ByteBuffer. The digest is
 * updated using the {@code input.remaining()} bytes 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
 * @since 1.5
 */
 public final void update(ByteBuffer input) {
 if (input == null) {
 throw new NullPointerException();
 }
 engineUpdate(input);
 state = IN_PROGRESS;
 }

 /**
 * Completes the hash computation by performing final operations
 * such as padding. The digest is reset after this call is made.
 *
 * @return the array of bytes for the resulting hash value.
 */
 public byte[] digest() {
 /* Resetting is the responsibility of implementors. */
 byte[] result = engineDigest();
 state = INITIAL;
 return result;
 }

 /**
 * Completes the hash computation by performing final operations
 * such as padding. The digest is reset after this call is made.
 *
 * @param buf output buffer for the computed digest
 *
 * @param offset offset into the output buffer to begin storing the digest
 *
 * @param len number of bytes within buf allotted for the digest
 *
 * @return the number of bytes placed into {@code buf}
 *
 * @exception DigestException if an error occurs.
 */
 public int digest(byte[] buf, int offset, int len) throws DigestException {
 if (buf == null) {
 throw new IllegalArgumentException("No output buffer given");
 }
 if (buf.length - offset < len) {
 throw new IllegalArgumentException
 ("Output buffer too small for specified offset and length");
 }
 int numBytes = engineDigest(buf, offset, len);
 state = INITIAL;
 return numBytes;
 }

 /**
 * Performs a final update on the digest using the specified array
 * of bytes, then completes the digest computation. That is, this
 * method first calls {@link #update(byte[]) update(input)},
 * passing the <i>input</i> array to the {@code update} method,
 * then calls {@link #digest() digest()}.
 *
 * @param input the input to be updated before the digest is
 * completed.
 *
 * @return the array of bytes for the resulting hash value.
 */
 public byte[] digest(byte[] input) {
 update(input);
 return digest();
 }

 /**
 * Returns a string representation of this message digest object.
 */
 public String toString() {
 ByteArrayOutputStream baos = new ByteArrayOutputStream();
 PrintStream p = new PrintStream(baos);
 p.print(algorithm+" Message Digest from "+provider.getName()+", ");
 switch (state) {
 case INITIAL:
 p.print("<initialized>");
 break;
 case IN_PROGRESS:
 p.print("<in progress>");
 break;
 }
 p.println();
 return (baos.toString());
 }

 /**
 * Compares two digests for equality. Does a simple byte compare.
 *
 * @param digesta one of the digests to compare.
 *
 * @param digestb the other digest to compare.
 *
 * @return true if the digests are equal, false otherwise.
 */
 public static boolean isEqual(byte[] digesta, byte[] digestb) {
 if (digesta == digestb) return true;
 if (digesta == null || digestb == null) {
 return false;
 }
 if (digesta.length != digestb.length) {
 return false;
 }

 int result = 0;
 // time-constant comparison
 for (int i = 0; i < digesta.length; i++) {
 result |= digesta[i] ^ digestb[i];
 }
 return result == 0;
 }

 /**
 * Resets the digest for further use.
 */
 public void reset() {
 engineReset();
 state = INITIAL;
 }

 /**
 * Returns a string that identifies the algorithm, independent of
 * implementation details. The name should be a standard
 * Java Security name (such as "SHA-256").
 * See the MessageDigest section in the <a href=
 * "{@docRoot}/../technotes/guides/security/StandardNames.html#MessageDigest">
 * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
 * for information about standard algorithm names.
 *
 * @return the name of the algorithm
 */
 public final String getAlgorithm() {
 return this.algorithm;
 }

 /**
 * Returns the length of the digest in bytes, or 0 if this operation is
 * not supported by the provider and the implementation is not cloneable.
 *
 * @return the digest length in bytes, or 0 if this operation is not
 * supported by the provider and the implementation is not cloneable.
 *
 * @since 1.2
 */
 public final int getDigestLength() {
 int digestLen = engineGetDigestLength();
 if (digestLen == 0) {
 try {
 MessageDigest md = (MessageDigest)clone();
 byte[] digest = md.digest();
 return digest.length;
 } catch (CloneNotSupportedException e) {
 return digestLen;
 }
 }
 return digestLen;
 }

 /**
 * Returns a clone if the implementation is cloneable.
 *
 * @return a clone if the implementation is cloneable.
 *
 * @exception CloneNotSupportedException if this is called on an
 * implementation that does not support {@code Cloneable}.
 */
 public Object clone() throws CloneNotSupportedException {
 if (this instanceof Cloneable) {
 return super.clone();
 } else {
 throw new CloneNotSupportedException();
 }
 }




 /*
 * The following class allows providers to extend from MessageDigestSpi
 * rather than from MessageDigest. It represents a MessageDigest with an
 * encapsulated, provider-supplied SPI object (of type MessageDigestSpi).
 * If the provider implementation is an instance of MessageDigestSpi,
 * the getInstance() methods above return an instance of this class, with
 * the SPI object encapsulated.
 *
 * Note: All SPI methods from the original MessageDigest class have been
 * moved up the hierarchy into a new class (MessageDigestSpi), which has
 * been interposed in the hierarchy between the API (MessageDigest)
 * and its original parent (Object).
 */

 static class Delegate extends MessageDigest {

 // The provider implementation (delegate)
 private MessageDigestSpi digestSpi;

 // constructor
 public Delegate(MessageDigestSpi digestSpi, String algorithm) {
 super(algorithm);
 this.digestSpi = digestSpi;
 }

 /**
 * Returns a clone if the delegate is cloneable.
 *
 * @return a clone if the delegate is cloneable.
 *
 * @exception CloneNotSupportedException if this is called on a
 * delegate that does not support {@code Cloneable}.
 */
 public Object clone() throws CloneNotSupportedException {
 if (digestSpi instanceof Cloneable) {
 MessageDigestSpi digestSpiClone =
 (MessageDigestSpi)digestSpi.clone();
 // Because 'algorithm', 'provider', and 'state' are private
 // members of our supertype, we must perform a cast to
 // access them.
 MessageDigest that =
 new Delegate(digestSpiClone,
 ((MessageDigest)this).algorithm);
 that.provider = ((MessageDigest)this).provider;
 that.state = ((MessageDigest)this).state;
 return that;
 } else {
 throw new CloneNotSupportedException();
 }
 }

 protected int engineGetDigestLength() {
 return digestSpi.engineGetDigestLength();
 }

 protected void engineUpdate(byte input) {
 digestSpi.engineUpdate(input);
 }

 protected void engineUpdate(byte[] input, int offset, int len) {
 digestSpi.engineUpdate(input, offset, len);
 }

 protected void engineUpdate(ByteBuffer input) {
 digestSpi.engineUpdate(input);
 }

 protected byte[] engineDigest() {
 return digestSpi.engineDigest();
 }

 protected int engineDigest(byte[] buf, int offset, int len)
 throws DigestException {
 return digestSpi.engineDigest(buf, offset, len);
 }

 protected void engineReset() {
 digestSpi.engineReset();
 }
 }
}