Java tutorial
/* * File : $Source: /alkacon/cvs/alkacon/com.alkacon.opencms.commons/src/com/alkacon/opencms/commons/CmsStringCrypter.java,v $ * Date : $Date: 2007/11/30 11:57:27 $ * Version: $Revision: 1.3 $ * * This file is part of the Alkacon OpenCms Add-On Module Package * * Copyright (c) 2007 Alkacon Software GmbH (http://www.alkacon.com) * * The Alkacon OpenCms Add-On Module Package 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 3 of the License, or * (at your option) any later version. * * The Alkacon OpenCms Add-On Module Package 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. * * You should have received a copy of the GNU General Public License * along with the Alkacon OpenCms Add-On Module Package. * If not, see http://www.gnu.org/licenses/. * * For further information about Alkacon Software GmbH, please see the * company website: http://www.alkacon.com. * * For further information about OpenCms, please see the * project website: http://www.opencms.org. */ package com.alkacon.opencms.commons; import org.opencms.i18n.CmsEncoder; import org.opencms.main.CmsLog; import org.opencms.util.CmsStringUtil; import java.security.Key; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import javax.crypto.Cipher; import javax.crypto.spec.SecretKeySpec; import org.apache.commons.logging.Log; import sun.misc.BASE64Decoder; import sun.misc.BASE64Encoder; /** * This class is responsible for encrypting and decrypting Strings.<p> * * The result can be be used as URL parameters.<p> * * @author Peter Bonrad * @author Andreas Zahner */ public final class CmsStringCrypter { /** The encryption to be used. */ private static final String ENCRYPTION = "DES"; /** The format of the key and the values to be crypted. */ private static final String FORMAT = "UTF8"; /** The log object for this class. */ private static final Log LOG = CmsLog.getLog(CmsStringCrypter.class); /** The default password to be used. */ private static final String PASSWORD_DEFAULT = "fuZe-6jK"; /** * Hides the public constructor for this utility class.<p> */ private CmsStringCrypter() { // hide constructor } /** * Decrypts the given value which was encrypted with the encrypt method with a default password.<p> * * @param value the value to be decrypted * @return the decrypted string of the value or null if something went wrong */ public static String decrypt(String value) { return decrypt(value, PASSWORD_DEFAULT); } /** * Decrypts the given value which was encrypted with the encrypt method.<p> * * @param value the value to be decrypted * @param password the passsword used for decryption, has to be the same as used for encryption * @return the decrypted string of the value or null if something went wrong */ public static String decrypt(String value, String password) { // check if given value is valid if (CmsStringUtil.isEmptyOrWhitespaceOnly(value)) { if (LOG.isWarnEnabled()) { LOG.warn(Messages.get().getBundle().key(Messages.LOG_WARN_INVALID_DECRYPT_STRING_1, value)); } return null; } try { // create key Key key = new SecretKeySpec(getKey(password), ENCRYPTION); Cipher cipher = Cipher.getInstance(ENCRYPTION); cipher.init(Cipher.DECRYPT_MODE, key); // decode from base64 BASE64Decoder base64decoder = new BASE64Decoder(); byte[] cleartext = base64decoder.decodeBuffer(value); // decrypt text byte[] ciphertext = cipher.doFinal(cleartext); return CmsEncoder.decode(new String(ciphertext)); } catch (Exception ex) { if (LOG.isErrorEnabled()) { LOG.error(Messages.get().getBundle().key(Messages.LOG_ERROR_DECRPYT_0), ex); } } return null; } /** * Encrypts the given value with a default password.<p> * * @param value the string which should be encrypted * @return the encrypted string of the value or null if something went wrong */ public static String encrypt(String value) { return encrypt(value, PASSWORD_DEFAULT); } /** * Encrypts the given value.<p> * * @param value the string which should be encrypted * @param password the passsword used for encryption, use the same password for decryption * @return the encrypted string of the value or null if something went wrong */ public static String encrypt(String value, String password) { // check if given value is valid if (CmsStringUtil.isEmptyOrWhitespaceOnly(value)) { if (LOG.isWarnEnabled()) { LOG.warn(Messages.get().getBundle().key(Messages.LOG_WARN_INVALID_ENCRYPT_STRING_1, value)); } return null; } try { // create key byte[] k = getKey(password); Key key = new SecretKeySpec(k, ENCRYPTION); Cipher cipher = Cipher.getInstance(ENCRYPTION); cipher.init(Cipher.ENCRYPT_MODE, key); // encrypt text byte[] cleartext = value.getBytes(FORMAT); byte[] ciphertext = cipher.doFinal(cleartext); // encode with base64 to be used as a url parameter BASE64Encoder base64encoder = new BASE64Encoder(); return CmsEncoder.encode(base64encoder.encode(ciphertext)); } catch (Exception ex) { if (LOG.isErrorEnabled()) { LOG.error(Messages.get().getBundle().key(Messages.LOG_ERROR_ENCRYPT_0), ex); } } return null; } /** * Converts the given password to machine readable form.<p> * * @param password the password to convert to a machine readable key * @return the password in machine readable form */ private static byte[] getKey(String password) { try { MessageDigest md5 = MessageDigest.getInstance("MD5"); md5.update(password.toString().getBytes()); byte[] key = md5.digest(); // now get the first 8 bytes byte[] finalKey = new byte[8]; for (int i = 0; i <= 7; i++) { finalKey[i] = key[i]; } return finalKey; } catch (NoSuchAlgorithmException ex) { if (LOG.isErrorEnabled()) { LOG.error(Messages.get().getBundle().key(Messages.LOG_ERROR_CREATE_KEY_0), ex); } } return null; } }