package fr.in2p3.jsaga.adaptor.security;
   
   import org.apache.commons.codec.binary.Base64;
   import org.ogf.saga.error.BadParameterException;
   
   import javax.crypto.Cipher;
   
   /* ***************************************************
   * *** Centre de Calcul de l'IN2P3 - Lyon (France) ***
  * ***             http://cc.in2p3.fr/             ***
  * ***************************************************
  * File:   PasswordDecrypterSingleton
  * Author: Sylvain Reynaud (sreynaud@in2p3.fr)
  * Date:   21 sept. 2007
  * ***************************************************
  * Description:                                      */
  /**
   *
   */
  public class PasswordDecrypterSingleton extends PasswordAbstract {
      private static final int EXPIRY_DATE_POSITION = 12;
  
      /**
       * @param keyalias the alias of the secret key
       */
      public PasswordDecrypterSingleton(String keyalias) throws Exception {
          super();
  
          // load key from keystore
          m_key = m_keystore.getKey(keyalias, m_keypass);
          if (m_key == null) {
              throw new BadParameterException("Key not found in keystore: "+keyalias);
          }
      }
  
      public int getExpiryDate() {
          return getValue(m_key.getEncoded(), EXPIRY_DATE_POSITION);
      }
  
      public String decrypt(String cryptedBase64) throws Exception {
          byte[] crypted = Base64.decodeBase64(cryptedBase64);
          Cipher cipher = Cipher.getInstance(CIPHER);
          cipher.init(Cipher.DECRYPT_MODE, m_key);
          byte[] decrypted = cipher.doFinal(crypted);
          return new String(decrypted);
      }
  
      private static int getValue(byte[] bytes, int pos) {
          return ((bytes[pos] & 0xFF) << 24)
                  | ((bytes[pos+1] & 0xFF) << 16)
                  | ((bytes[pos+2] & 0xFF) << 8)
                  | (bytes[pos+3] & 0xFF);
      }
  }