/*
  Name:         Keystore.java
  Licensing:    LGPL

  API:          Sun (http://java.sun.com) JCE 1.2.2 API (cleanroom implementation by Bouncy Castle)
  Provider:     Bouncy Castle (http://www.bouncycastle.org)

  Disclaimer:

  COVERED CODE IS PROVIDED UNDER THIS LICENSE ON AN "AS IS" BASIS, WITHOUT WARRANTY OF ANY KIND,
  EITHER EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES THAT THE COVERED CODE
  IS FREE OF DEFECTS, MERCHANTABLE, FIT FOR A PARTICULAR PURPOSE OR NON-INFRINGING. THE ENTIRE
  RISK AS TO THE QUALITY AND PERFORMANCE OF THE COVERED CODE IS WITH YOU. SHOULD ANY COVERED CODE
  PROVE DEFECTIVE IN ANY RESPECT, YOU (NOT THE INITIAL DEVELOPER OR ANY OTHER CONTRIBUTOR)
  ASSUME THE COST OF ANY NECESSARY SERVICING, REPAIR OR CORRECTION. THIS DISCLAIMER OF WARRANTY
  CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. NO USE OF ANY COVERED CODE IS AUTHORIZED
  HEREUNDER EXCEPT UNDER THIS DISCLAIMER.

  (C) Copyright 2003 Gert Van Ham
*/

package net.sourceforge.jcetaglib.lib;

import net.sourceforge.jcetaglib.exceptions.CryptoException;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import java.io.File;
import java.io.FileInputStream;
import java.security.SecureRandom;
import java.security.Security;

/**
 * Create SecureRandom seed from different sources
 *
 * @author Gert Van Ham
 * @author hamgert@users.sourceforge.net
 * @author http://jcetaglib.sourceforge.net
 * @version $Id: Seed.java,v 1.1 2003/12/28 19:04:26 hamgert Exp $
 */
public class Seed {

    /**
     * Get Random filename
     *
     * @return filename
     */
    private static String getDevRandomFilename() {
        String filename = "/dev/urandom";

        if (System.getProperty("java.security.egd") != null) {
            filename = System.getProperty("java.security.egd");
        }

        return filename;
    }

    /**
     * Create and seed SecureRandom (from optional seed, random file or self-seed)
     *
     * @param seed optional seed
     * @return SecureRandom object
     * @throws CryptoException
     */
    public static SecureRandom getSecureRandom(byte[] seed)
            throws CryptoException {
        SecureRandom sr = null;

        Security.addProvider(new BouncyCastleProvider());

        try {
            sr = SecureRandom.getInstance("SHA1PRNG", "SUN");

            if (seed != null && !seed.equals("")) {
                // set provided seed
                sr.setSeed(seed);
                Clean.blank(seed);
            } else {
                // try random file name on Unix boxes
                if (new File(getDevRandomFilename()).exists()) {
                    byte[] salt = new byte[8192];
                    new FileInputStream(getDevRandomFilename()).read(salt);
                    sr.setSeed(salt);
                    Clean.blank(salt);
                    salt = null;
                }
                // Windows machines must self-seed
            }

        } catch (Exception e) {
            e.printStackTrace();
            throw new CryptoException(e.getMessage());
        }

        return sr;
    }
}