Apple Developer Connection Student Program/ADC Tools Sampler CD Disk 3 1999.iso/Metrowerks CodeWarrior/Java Support/Java_Source/Java2/src/java/security/MessageDigest.java

Java Source | 1999-05-28 | 14.7 KB | 474 lines | [TEXT/CWIE]

/*
 * @(#)MessageDigest.java    1.62 98/07/17
 *
 * Copyright 1996-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

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 1.62 99/03/26
 *
 * @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 & 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 & 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", 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 & 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.
     *
     * @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 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</code>.
     */
    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;
    }

    /**
     * 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</code>
     *
     * @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 <a href = "#update(byte[])">update(input)</a>,
     * passing the <i>input</i> array to the <code>update</code> 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.length != digestb.length)
        return false;

    for (int i = 0; i < digesta.length; i++) {
        if (digesta[i] != digestb[i]) {
        return false;
        }
    }
    return true;
    }

    /**
     * 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", "MD5", and so on).
     * See Appendix A in the <a href=
     * "../../../guide/security/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification & Reference </a>
     * for information about standard algorithm names.
     */
    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 JDK1.2
     */
    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</code>.
     */
    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</code>.
     */
    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 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();
    }
    }
}