/*
    *  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.checksum;
  
  
  import java.util.Collections;
  import java.util.EnumMap;
  import java.util.Map;
  
  import org.apache.directory.server.kerberos.shared.crypto.encryption.Aes128CtsSha1Encryption;
  import org.apache.directory.server.kerberos.shared.crypto.encryption.Aes256CtsSha1Encryption;
  import org.apache.directory.server.kerberos.shared.crypto.encryption.Des3CbcSha1KdEncryption;
  import org.apache.directory.server.kerberos.shared.crypto.encryption.KeyUsage;
  import org.apache.directory.shared.kerberos.components.Checksum;
  import org.apache.directory.shared.kerberos.crypto.checksum.ChecksumType;
  import org.apache.directory.shared.kerberos.exceptions.ErrorType;
  import org.apache.directory.shared.kerberos.exceptions.KerberosException;
  
  
  /**
   * A Hashed Adapter encapsulating checksum engines for performing integrity checks.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class ChecksumHandler
  {
      /** A map of the default encodable class names to the encoder class names. */
      private static final Map<ChecksumType, Class<?>> DEFAULT_CHECKSUMS;
  
      static
      {
          EnumMap<ChecksumType, Class<?>> map = new EnumMap<>( ChecksumType.class );
  
          map.put( ChecksumType.HMAC_MD5, HmacMd5Checksum.class );
          map.put( ChecksumType.HMAC_SHA1_96_AES128, Aes128CtsSha1Encryption.class );
          map.put( ChecksumType.HMAC_SHA1_96_AES256, Aes256CtsSha1Encryption.class );
          map.put( ChecksumType.HMAC_SHA1_DES3_KD, Des3CbcSha1KdEncryption.class );
          map.put( ChecksumType.RSA_MD5, RsaMd5Checksum.class );
  
          DEFAULT_CHECKSUMS = Collections.unmodifiableMap( map );
      }
  
  
      /**
       * Calculate a checksum based on raw bytes and an (optional) key for keyed checksums.
       *
       * @param checksumType The type of checksum to use
       * @param bytes The data
       * @param key The key
       * @param usage The key usage 
       * @return The computed {@link Checksum}.
       * @throws KerberosException If the checksum can't be cmputed
       */
      public Checksum calculateChecksum( ChecksumType checksumType, byte[] bytes, byte[] key, KeyUsage usage )
          throws KerberosException
      {
          if ( !DEFAULT_CHECKSUMS.containsKey( checksumType ) )
          {
              throw new KerberosException( ErrorType.KDC_ERR_SUMTYPE_NOSUPP );
          }
  
          ChecksumEngine digester = getEngine( checksumType );
          return new Checksum( checksumType, digester.calculateChecksum( bytes, key, usage ) );
      }
  
  
      /**
       * Verify a checksum by providing the raw bytes and an (optional) key for keyed checksums.
       *
       * @param checksum The checksum to verify
       * @param bytes The data
       * @param key The key
       * @param usage The key usage 
       * @throws KerberosException If the verification failed
       */
      public void verifyChecksum( Checksum checksum, byte[] bytes, byte[] key, KeyUsage usage ) throws KerberosException
      {
          if ( checksum == null )
          {
              throw new KerberosException( ErrorType.KRB_AP_ERR_INAPP_CKSUM );
          }
  
         if ( !DEFAULT_CHECKSUMS.containsKey( checksum.getChecksumType() ) )
         {
             throw new KerberosException( ErrorType.KDC_ERR_SUMTYPE_NOSUPP );
         }
 
         ChecksumType checksumType = checksum.getChecksumType();
         ChecksumEngine digester = getEngine( checksumType );
         Checksumared/kerberos/components/Checksum.html#Checksum">Checksum newChecksum = new Checksum( checksumType, digester.calculateChecksum( bytes, key, usage ) );
 
         if ( !newChecksum.equals( checksum ) )
         {
             throw new KerberosException( ErrorType.KRB_AP_ERR_MODIFIED );
         }
     }
 
 
     private ChecksumEngine getEngine( ChecksumType checksumType ) throws KerberosException
     {
         Class<?> clazz = DEFAULT_CHECKSUMS.get( checksumType );
 
         if ( clazz == null )
         {
             throw new KerberosException( ErrorType.KDC_ERR_SUMTYPE_NOSUPP );
         }
 
         try
         {
             return ( ChecksumEngine ) clazz.newInstance();
         }
         catch ( IllegalAccessException iae )
         {
             throw new KerberosException( ErrorType.KDC_ERR_SUMTYPE_NOSUPP, iae );
         }
         catch ( InstantiationException ie )
         {
             throw new KerberosException( ErrorType.KDC_ERR_SUMTYPE_NOSUPP, ie );
         }
     }
 }