messagedigest.java

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/*
 * @(#)MessageDigest.java	1.78 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

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;

/**
 * This MessageDigest class provides applications the functionality of a
 * message digest algorithm, such as MD5 or SHA.
 * 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</code> method can be called once for a given number 
 * of updates. After <code>digest</code> 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: <p>    
 *
* <pre>
* MessageDigest md = MessageDigest.getInstance("SHA");
*
* 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</code> for historical reasons.
 * Application developers should only take notice of the methods defined in
 * this <code>MessageDigest</code> class; all the methods in
 * the superclass are intended for cryptographic service providers who wish to
 * supply their own implementations of message digest algorithms.
 *
 * @author Benjamin Renaud 
 *
 * @version 1.71, 02/02/00
 *
 * @see DigestInputStream
 * @see DigestOutputStream
 */

public abstract class MessageDigest extends MessageDigestSpi {

    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 Appendix A in the <a href=
     * "../../../guide/security/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     */
    protected MessageDigest(String algorithm) {
	this.algorithm = algorithm;
    }

    /**
     * Generates a MessageDigest object that implements the specified digest
     * algorithm. If the default provider package
     * provides an implementation of the requested digest algorithm,
     * an instance of MessageDigest containing that implementation is returned.
     * If the algorithm is not available in the default 
     * package, other packages are searched.
     *
     * @param algorithm the name of the algorithm requested. 
     * See Appendix A in the <a href=
     * "../../../guide/security/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @return a Message Digest object implementing the specified
     * algorithm.
     *
     * @exception NoSuchAlgorithmException if the algorithm is
     * not available in the caller's environment.  
     */
    public static MessageDigest getInstance(String algorithm) 
    throws NoSuchAlgorithmException { 
	try {
	    Object[] objs = Security.getImpl(algorithm, "MessageDigest",
					     (String)null);
	    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;
	    }
	} catch(NoSuchProviderException e) {
	    throw new NoSuchAlgorithmException(algorithm + " not found");
	}
    }

    /**
     * Generates a MessageDigest object implementing the specified
     * algorithm, as supplied from the specified provider, if such an 
     * algorithm is available from the provider.
     *
     * @param algorithm the name of the algorithm requested. 
     * See Appendix A in the <a href=
     * "../../../guide/security/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @param provider the name of the provider.
     *
     * @return a Message Digest object implementing the specified
     * algorithm.
     *
     * @exception NoSuchAlgorithmException if the algorithm is
     * not available in the package supplied by the requested
     * provider.
     *
     * @exception NoSuchProviderException if the provider is not
     * available in the environment. 
     *
     * @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;
	}
    }

    /**
     * Generates a MessageDigest object implementing the specified
     * algorithm, as supplied from the specified provider, if such an 
     * algorithm is available from the provider. Note: the 
     * <code>provider</code> doesn't have to be registered. 
     *
     * @param algorithm the name of the algorithm requested. 
     * See Appendix A in the <a href=
     * "../../../guide/security/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a> 
     * for information about standard algorithm names.
     *
     * @param provider the provider.
     *
     * @return a Message Digest object implementing the specified
     * algorithm.
     *
     * @exception NoSuchAlgorithmException if the algorithm is
     * not available in the package supplied by the requested
     * provider.
     *
     * @exception IllegalArgumentException if the <code>provider</code> 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