MessageDigest.java

/* MessageDigest.java --- The message digest interface.
   Copyright (C) 1999, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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this exception to your version of the library, but you are not
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package java.security;

import gnu.java.lang.CPStringBuilder;

import gnu.java.security.Engine;
import java.nio.ByteBuffer;

import java.lang.reflect.InvocationTargetException;

/**
 * Message digests are secure one-way hash functions that take arbitrary-sized
 * data and output a fixed-length hash value.
 *
 * @see MessageDigestSpi
 * @since JDK 1.1
 */
public abstract class MessageDigest extends MessageDigestSpi
{
  /** The service name for message digests. */
  private static final String MESSAGE_DIGEST = "MessageDigest";

  private String algorithm;
  Provider provider;
  private byte[] lastDigest;

  /**
   * Constructs a new instance of <code>MessageDigest</code> representing the
   * specified algorithm.
   *
   * @param algorithm
   *          the name of the digest algorithm to use.
   */
  protected MessageDigest(String algorithm)
  {
    this.algorithm = algorithm;
    provider = null;
  }

  /**
   * Returns a new instance of <code>MessageDigest</code> representing the
   * specified algorithm.
   *
   * @param algorithm the name of the digest algorithm to use.
   * @return a new instance representing the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by any
   *           provider.
   * @throws IllegalArgumentException if <code>algorithm</code> is
   *           <code>null</code> or is an empty string.
   */
  public static MessageDigest getInstance(String algorithm)
      throws NoSuchAlgorithmException
  {
    Provider[] p = Security.getProviders();
    NoSuchAlgorithmException lastException = null;
    for (int i = 0; i < p.length; i++)
      try
        {
          return getInstance(algorithm, p[i]);
        }
      catch (NoSuchAlgorithmException x)
        {
          lastException = x;
        }
    if (lastException != null)
      throw lastException;
    throw new NoSuchAlgorithmException(algorithm);
  }

  /**
   * Returns a new instance of <code>MessageDigest</code> representing the
   * specified algorithm from a named provider.
   *
   * @param algorithm the name of the digest algorithm to use.
   * @param provider the name of the provider to use.
   * @return a new instance representing the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by the
   *           named provider.
   * @throws NoSuchProviderException if the named provider was not found.
   * @throws IllegalArgumentException if either <code>algorithm</code> or
   *           <code>provider</code> is <code>null</code> or empty.
   */
  public static MessageDigest getInstance(String algorithm, String provider)
      throws NoSuchAlgorithmException, NoSuchProviderException
  {
    if (provider == null)
      throw new IllegalArgumentException("provider MUST NOT be null");
    provider = provider.trim();
    if (provider.length() == 0)
      throw new IllegalArgumentException("provider MUST NOT be empty");
    Provider p = Security.getProvider(provider);
    if (p == null)
      throw new NoSuchProviderException(provider);
    return getInstance(algorithm, p);
  }

  /**
   * Returns a new instance of <code>MessageDigest</code> representing the
   * specified algorithm from a designated {@link Provider}.
   *
   * @param algorithm the name of the digest algorithm to use.
   * @param provider the {@link Provider} to use.
   * @return a new instance representing the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by
   *           {@link Provider}.
   * @throws IllegalArgumentException if either <code>algorithm</code> or
   *           <code>provider</code> is <code>null</code>, or if
   *           <code>algorithm</code> is an empty string.
   * @since 1.4
   * @see Provider
   */
  public static MessageDigest getInstance(String algorithm, Provider provider)
    throws NoSuchAlgorithmException
  {
    CPStringBuilder sb = new CPStringBuilder("MessageDigest for algorithm [")
        .append(algorithm).append("] from provider[")
        .append(provider).append("] ");
    Object o;
    try
      {
        o = Engine.getInstance(MESSAGE_DIGEST, algorithm, provider);
      }
    catch (InvocationTargetException x)
      {
        Throwable cause = x.getCause();
        if (cause instanceof NoSuchAlgorithmException)
          throw (NoSuchAlgorithmException) cause;
        if (cause == null)
          cause = x;
        sb.append("could not be created");
        NoSuchAlgorithmException y = new NoSuchAlgorithmException(sb.toString());
        y.initCause(cause);
        throw y;
      }
    MessageDigest result;
    if (o instanceof MessageDigestSpi)
      result = new DummyMessageDigest((MessageDigestSpi) o, algorithm);
    else if (o instanceof MessageDigest)
      {
        result = (MessageDigest) o;
        result.algorithm = algorithm;
      }
    else
      {
        sb.append("is of an unexpected Type: ").append(o.getClass().getName());
        throw new NoSuchAlgorithmException(sb.toString());
      }
    result.provider = provider;
    return result;
  }

  /**
   * Returns the {@link Provider} of this instance.
   *
   * @return the {@link Provider} of this instance.
   */
  public final Provider getProvider()
  {
    return provider;
  }

  /**
   * Updates the digest with the byte.
   *
   * @param input byte to update the digest with.
   */
  public void update(byte input)
  {
    engineUpdate(input);
  }

  /**
   * Updates the digest with the bytes from the array starting from the
   * specified offset and using the specified length of bytes.
   *
   * @param input
   *          bytes to update the digest with.
   * @param offset
   *          the offset to start at.
   * @param len
   *          length of the data to update with.
   */
  public void update(byte[] input, int offset, int len)
  {
    engineUpdate(input, offset, len);
  }

  /**
   * Updates the digest with the bytes of an array.
   *
   * @param input bytes to update the digest with.
   */
  public void update(byte[] input)
  {
    engineUpdate(input, 0, input.length);
  }

  /**
   * Updates the digest with the remaining bytes of a buffer.
   *
   * @param input The input byte buffer.
   * @since 1.5
   */
  public final void update (ByteBuffer input)
  {
    engineUpdate (input);
  }

  /**
   * Computes the final digest of the stored data.
   *
   * @return a byte array representing the message digest.
   */
  public byte[] digest()
  {
    return lastDigest = engineDigest();
  }

  /**
   * Computes the final digest of the stored bytes and returns the result.
   *
   * @param buf
   *          an array of bytes to store the result in.
   * @param offset
   *          an offset to start storing the result at.
   * @param len
   *          the length of the buffer.
   * @return Returns the length of the buffer.
   */
  public int digest(byte[] buf, int offset, int len) throws DigestException
  {
    return engineDigest(buf, offset, len);
  }

  /**
   * Computes a final update using the input array of bytes, then computes a
   * final digest and returns it. It calls {@link #update(byte[])} and then
   * {@link #digest(byte[])}.
   *
   * @param input
   *          an array of bytes to perform final update with.
   * @return a byte array representing the message digest.
   */
  public byte[] digest(byte[] input)
  {
    update(input);
    return digest();
  }

  /**
   * Returns a string representation of this instance.
   *
   * @return a string representation of this instance.
   */
  public String toString()
  {
    return (getClass()).getName() + " Message Digest <" + digestToString() + ">";
  }

  /**
   * Does a simple byte comparison of the two digests.
   *
   * @param digesta
   *          first digest to compare.
   * @param digestb
   *          second digest to compare.
   * @return <code>true</code> if both are equal, <code>false</code>
   *         otherwise.
   */
  public static boolean isEqual(byte[] digesta, byte[] digestb)
  {
    if (digesta.length != digestb.length)
      return false;

    for (int i = digesta.length - 1; i >= 0; --i)
      if (digesta[i] != digestb[i])
        return false;

    return true;
  }

  /** Resets this instance. */
  public void reset()
  {
    engineReset();
  }

  /**
   * Returns the name of message digest algorithm.
   *
   * @return the name of message digest algorithm.
   */
  public final String getAlgorithm()
  {
    return algorithm;
  }

  /**
   * Returns the length of the message digest. The default is zero which means
   * that the concrete implementation does not implement this method.
   *
   * @return length of the message digest.
   * @since 1.2
   */
  public final int getDigestLength()
  {
    return engineGetDigestLength();
  }

  /**
   * Returns a clone of this instance if cloning is supported. If it does not
   * then a {@link CloneNotSupportedException} is thrown. Cloning depends on
   * whether the subclass {@link MessageDigestSpi} implements {@link Cloneable}
   * which contains the actual implementation of the appropriate algorithm.
   *
   * @return a clone of this instance.
   * @throws CloneNotSupportedException
   *           the implementation does not support cloning.
   */
  public Object clone() throws CloneNotSupportedException
  {
    return super.clone();
  }

  private String digestToString()
  {
    byte[] digest = lastDigest;

    if (digest == null)
      return "incomplete";

    CPStringBuilder buf = new CPStringBuilder();
    int len = digest.length;
    for (int i = 0; i < len; ++i)
      {
        byte b = digest[i];
        byte high = (byte) ((b & 0xff) >>> 4);
        byte low = (byte) (b & 0xf);

        buf.append(high > 9 ? ('a' - 10) + high : '0' + high);
        buf.append(low > 9 ? ('a' - 10) + low : '0' + low);
      }

    return buf.toString();
  }
}