/* SecureRandomAdapter.java -- 
   Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a 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 of the License, or (at
your option) any later version.

GNU Classpath 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 for more details.

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along with GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, 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
conditions of the GNU General Public License cover the whole
combination.

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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independent module, the terms and conditions of the license of that
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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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package gnu.java.security.jce.prng;

import gnu.java.security.action.GetSecurityPropertyAction;
import gnu.classpath.SystemProperties;
import gnu.java.security.prng.LimitReachedException;
import gnu.java.security.prng.MDGenerator;

import java.security.AccessController;
import java.security.SecureRandom;
import java.security.SecureRandomSpi;

import java.util.Collections;
import java.util.logging.Level;
import java.util.logging.Logger;

import java.io.InputStream;
import java.io.IOException;

import java.net.MalformedURLException;
import java.net.URL;

/**
 * <p>The implementation of a generic {@link java.security.SecureRandom} adapter
 * class to wrap gnu.crypto prng instances based on Message Digest algorithms.</p>
 *
 * <p>This class defines the <i>Service Provider Interface</i> (<b>SPI</b>) for
 * the {@link java.security.SecureRandom} class, which provides the
 * functionality of a cryptographically strong pseudo-random number generator.</p>
 *
 * <p>All the abstract methods in the {@link SecureRandomSpi} class are
 * implemented by this class and all its sub-classes.</p>
 */
public abstract class SecureRandomAdapter 
  extends SecureRandomSpi
{

  private boolean isSeeded = false;

  /** Our underlying prng instance. */
  private MDGenerator adaptee = new MDGenerator();

  /** The name of the message digest algorithm used by the adaptee. */
  private String mdName;

  private static final Logger logger =
    Logger.getLogger(SecureRandom.class.getName());

  private static final String SECURERANDOM_SOURCE = "securerandom.source";
  private static final String JAVA_SECURITY_EGD = "java.security.egd";

  /**
   * <p>Trivial protected constructor.</p>
   *
   * @param mdName the canonical name of the underlying hash algorithm.
   */
  protected SecureRandomAdapter(String mdName)
  {
    super();

    this.mdName = mdName;
    adaptee.init (Collections.singletonMap (MDGenerator.MD_NAME, mdName));
  }

  public static final byte[] getSeed(int numBytes)
  {  
    URL sourceUrl = null;
    String urlStr = null;

    byte[] buffer = new byte[numBytes];

    GetSecurityPropertyAction action =
      new GetSecurityPropertyAction(SECURERANDOM_SOURCE);
    try
      {
        urlStr = (String) AccessController.doPrivileged(action);
        if (urlStr != null)
          sourceUrl = new URL(urlStr);
      }
    catch (MalformedURLException ignored)
      {
        logger.log(Level.WARNING,
		   SECURERANDOM_SOURCE + " property is malformed: {0}", 
                   urlStr);
      }

    if (sourceUrl == null)
      {
        try
          {
            urlStr = SystemProperties.getProperty(JAVA_SECURITY_EGD);
            if (urlStr != null)
              sourceUrl = new URL(urlStr);
          }
        catch (MalformedURLException mue)
          {
            logger.log(Level.WARNING,
		       JAVA_SECURITY_EGD + " property is malformed: {0}",
                       urlStr);
          }
      }

    if (sourceUrl != null)
      {
        try
          {
            InputStream in = sourceUrl.openStream();
            in.read(buffer);
            return buffer;
          }
        catch (IOException ioe)
          {
            logger.log(Level.FINE, "error reading random bytes", ioe);
          }
      }

    // If we get here, we did not get any seed from a property URL.
    VMSecureRandom.generateSeed(buffer, 0, buffer.length);
    return buffer;
  }

  public byte[] engineGenerateSeed(int numBytes)
  {
    return getSeed(numBytes);
  }

  public void engineNextBytes(byte[] bytes)
  {
    if (!isSeeded)
      {
        engineSetSeed(engineGenerateSeed(32));
      }
    try
      {
        adaptee.nextBytes(bytes, 0, bytes.length);
      }
    catch (LimitReachedException ignored)
      {
      }
  }

  public void engineSetSeed(byte[] seed)
  {
    adaptee.addRandomBytes (seed);
    isSeeded = true;
  }
}