/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *  
   *    http://www.apache.org/licenses/LICENSE-2.0
   *  
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License. 
   *  
   */
  package org.apache.directory.server.kerberos.shared.crypto.encryption;
  
  
  import java.security.NoSuchAlgorithmException;
  import java.util.Collections;
  import java.util.EnumMap;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  
  import javax.crypto.KeyGenerator;
  import javax.crypto.SecretKey;
  
  import org.apache.directory.server.i18n.I18n;
  import org.apache.directory.shared.kerberos.codec.types.EncryptionType;
  import org.apache.directory.shared.kerberos.components.EncryptionKey;
  import org.apache.directory.shared.kerberos.exceptions.ErrorType;
  import org.apache.directory.shared.kerberos.exceptions.KerberosException;
  
  
  /**
   * A factory class for producing random keys, suitable for use as session keys.  For a
   * list of desired cipher types, Kerberos random-to-key functions are used to derive
   * keys for DES-, DES3-, AES-, and RC4-based encryption types.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class RandomKeyFactory
  {
      /** A map of default encryption types mapped to cipher names. */
      private static final Map<EncryptionType, String> DEFAULT_CIPHERS;
  
      static
      {
          EnumMap<EncryptionType, String> map = new EnumMap<>( EncryptionType.class );
  
          map.put( EncryptionType.DES_CBC_MD5, "DES" );
          map.put( EncryptionType.DES3_CBC_SHA1_KD, "DESede" );
          map.put( EncryptionType.RC4_HMAC, "RC4" );
          map.put( EncryptionType.AES128_CTS_HMAC_SHA1_96, "AES" );
          map.put( EncryptionType.AES256_CTS_HMAC_SHA1_96, "AES" );
  
          DEFAULT_CIPHERS = Collections.unmodifiableMap( map );
      }
  
  
      /**
       * Get a map of random keys.  The default set of encryption types is used.
       * 
       * @return The map of random keys.
       * @throws KerberosException 
       */
      public static Map<EncryptionType, EncryptionKey> getRandomKeys() throws KerberosException
      {
          return getRandomKeys( DEFAULT_CIPHERS.keySet() );
      }
  
  
      /**
       * Get a map of random keys for a list of cipher types to derive keys for.
       *
       * @param ciphers The list of ciphers to derive keys for.
       * @return The list of KerberosKey's.
       * @throws KerberosException 
       */
      public static Map<EncryptionType, EncryptionKey> getRandomKeys( Set<EncryptionType> ciphers )
          throws KerberosException
      {
          Map<EncryptionType, EncryptionKey> map = new HashMap<>();
  
          for ( EncryptionType encryptionType : ciphers )
          {
              map.put( encryptionType, getRandomKey( encryptionType ) );
          }
  
          return map;
      }
  
  
      /**
      * Get a new random key for a given {@link EncryptionType}.
      * 
      * @param encryptionType 
      * 
      * @return The new random key.
      * @throws KerberosException 
      */
     public static EncryptionKey getRandomKey( EncryptionType encryptionType ) throws KerberosException
     {
         String algorithm = DEFAULT_CIPHERS.get( encryptionType );
 
         if ( algorithm == null )
         {
             throw new KerberosException( ErrorType.KDC_ERR_ETYPE_NOSUPP, I18n.err( I18n.ERR_616,
                 encryptionType.getName() ) );
         }
 
         try
         {
             KeyGenerator keyGenerator = KeyGenerator.getInstance( algorithm );
 
             if ( encryptionType.equals( EncryptionType.AES128_CTS_HMAC_SHA1_96 ) )
             {
                 keyGenerator.init( 128 );
             }
 
             if ( encryptionType.equals( EncryptionType.AES256_CTS_HMAC_SHA1_96 ) )
             {
                 keyGenerator.init( 256 );
             }
 
             SecretKey key = keyGenerator.generateKey();
 
             byte[] keyBytes = key.getEncoded();
 
             return new EncryptionKey( encryptionType, keyBytes );
         }
         catch ( NoSuchAlgorithmException nsae )
         {
             throw new KerberosException( ErrorType.KDC_ERR_ETYPE_NOSUPP, nsae );
         }
     }
 }