/*
    *  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.shared.kerberos.components;
  
  
  import java.nio.BufferOverflowException;
  import java.nio.ByteBuffer;
  import java.security.MessageDigest;
  import java.util.Arrays;
  
  import org.apache.directory.api.asn1.Asn1Object;
  import org.apache.directory.api.asn1.EncoderException;
  import org.apache.directory.api.asn1.ber.tlv.BerValue;
  import org.apache.directory.api.asn1.ber.tlv.TLV;
  import org.apache.directory.api.asn1.ber.tlv.UniversalTag;
  import org.apache.directory.api.util.Strings;
  import org.apache.directory.server.i18n.I18n;
  import org.apache.directory.shared.kerberos.KerberosConstants;
  import org.apache.directory.shared.kerberos.codec.types.EncryptionType;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * A Kerberos symmetric encryption key, which includes metadata support for
   * the associated key type and key version number.
   * 
   * The ASN.1 description for this structure is :
   * <pre>
   * EncryptionKey   ::= SEQUENCE {
   *       keytype         [0] Int32 -- actually encryption type --,
   *       keyvalue        [1] OCTET STRING
   * }
   * </pre>
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class EncryptionKey implements Asn1Object
  {
      /** The logger */
      private static final Logger log = LoggerFactory.getLogger( EncryptionKey.class );
  
      /** Speedup for logs */
      private static final boolean IS_DEBUG = log.isDebugEnabled();
  
      /** The encryption type */
      private EncryptionType keyType;
  
      /** The encrypted value */
      private byte[] keyValue;
  
      /** The key version */
      private int keyVersion;
  
      // Storage for computed lengths
      private int keyTypeLength;
      private int keyValueLength;
      private int encryptionKeyLength;
  
  
      /**
       * Creates a new instance of EncryptionKey.
       */
      public EncryptionKey()
      {
      }
  
  
      /**
       * Creates a new instance of EncryptionKey.
       *
       * @param keyType The encryptionType 
       * @param keyValue The value
       */
      public EncryptionKey( EncryptionType keyType, byte[] keyValue )
      {
          this.keyType = keyType;
          this.keyValue = keyValue;
      }
  
  
      /**
       * Creates a new instance of EncryptionKey.
      *
      * @param keyType The encryptionType 
      * @param keyValue The value
      * @param keyVersion ???
      */
     public EncryptionKey( EncryptionType keyType, byte[] keyValue, int keyVersion )
     {
         this.keyType = keyType;
         this.keyValue = keyValue;
         this.keyVersion = keyVersion;
     }
 
 
     /**
      * Destroys this key by overwriting the symmetric key material with zeros.
      */
     public synchronized void destroy()
     {
         if ( keyValue != null )
         {
             Arrays.fill( keyValue, ( byte ) 0x00 );
         }
     }
 
 
     /**
      * Returns the key type.
      *
      * @return The key type.
      */
     public EncryptionType getKeyType()
     {
         return keyType;
     }
 
 
     /**
      * Set the encryption type
      * @param keyType The encryption type
      */
     public void setKeyType( EncryptionType keyType )
     {
         this.keyType = keyType;
     }
 
 
     /**
      * Returns the key value.
      *
      * @return The key value.
      */
     public byte[] getKeyValue()
     {
         return keyValue;
     }
 
 
     /**
      * Returns the key version.
      *
      * @return The key version.
      */
     public int getKeyVersion()
     {
         return keyVersion;
     }
 
 
     /**
      * Set the key value
      * @param keyVersion The key version
      */
     public void setKeyVersion( int keyVersion )
     {
         this.keyVersion = keyVersion;
     }
 
 
     /**
      * Set the key value
      * @param keyValue The key value
      */
     public void setKeyValue( byte[] keyValue )
     {
         this.keyValue = keyValue;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public int hashCode()
     {
         int hash = 37;
         hash = hash * 17 + keyType.hashCode();
         hash = hash * 17 + Arrays.hashCode( keyValue );
 
         return hash;
     }
 
 
     /**
      * @see Object#equals(Object)
      */
     @Override
     public boolean equals( Object o )
     {
         if ( this == o )
         {
             return true;
         }
 
         if ( !( o instanceof EncryptionKey ) )
         {
             return false;
         }
 
         EncryptionKey../../../../org/apache/directory/shared/kerberos/components/EncryptionKey.html#EncryptionKey">EncryptionKey that = ( EncryptionKey ) o;
         return ( this.keyType == that.keyType ) && ( MessageDigest.isEqual( this.keyValue, that.keyValue ) );
     }
 
 
     /**
      * Compute the EncryptionKey length
      * <pre>
      * EncryptionKey :
      * 
      * 0x30 L1 EncryptionKey
      *  |
      *  +--&gt; 0xA0 L2 keyType tag
      *  |     |
      *  |     +--&gt; 0x02 L2-1 keyType (int)
      *  |
      *  +--&gt; 0xA1 L3 keyValue tag
      *        |
      *        +--&gt; 0x04 L3-1 keyValue (OCTET STRING)
      *        
      *  where L1 = L2 + lenght(0xA0) + length(L2) +
      *             L3 + lenght(0xA1) + length(L3) 
      *  and
      *  L2 = L2-1 + length(0x02) + length( L2-1) 
      *  L3 = L3-1 + length(0x04) + length( L3-1)
      *  </pre> 
      */
     public int computeLength()
     {
         // Compute the keyType. The Length will always be cobntained in 1 byte
         keyTypeLength = 1 + 1 + BerValue.getNbBytes( keyType.getValue() );
         encryptionKeyLength = 1 + TLV.getNbBytes( keyTypeLength ) + keyTypeLength;
 
         // Compute the keyValue
         if ( keyValue == null )
         {
             keyValueLength = 1 + 1;
         }
         else
         {
             keyValueLength = 1 + TLV.getNbBytes( keyValue.length ) + keyValue.length;
         }
 
         encryptionKeyLength += 1 + TLV.getNbBytes( keyValueLength ) + keyValueLength;
 
         // Compute the whole sequence length
         return 1 + BerValue.getNbBytes( encryptionKeyLength ) + encryptionKeyLength;
     }
 
 
     /**
      * Encode the EncryptionKey message to a PDU. 
      * <pre>
      * EncryptionKey :
      * 
      * 0x30 LL
      *   0xA0 LL 
      *     0x02 0x01 keyType
      *   0xA1 LL 
      *     0x04 LL keyValue
      * </pre>
      * @param buffer The buffer where to put the PDU. It should have been allocated
      * before, with the right size.
      * @return The constructed PDU.
      */
     public ByteBuffer encode( ByteBuffer buffer ) throws EncoderException
     {
         if ( buffer == null )
         {
             throw new EncoderException( I18n.err( I18n.ERR_148 ) );
         }
 
         try
         {
             // The EncryptionKey SEQ Tag
             buffer.put( UniversalTag.SEQUENCE.getValue() );
             buffer.put( TLV.getBytes( encryptionKeyLength ) );
 
             // The keyType, first the tag, then the value
             buffer.put( ( byte ) KerberosConstants.ENCRYPTION_KEY_TYPE_TAG );
             buffer.put( TLV.getBytes( keyTypeLength ) );
             BerValue.encode( buffer, keyType.getValue() );
 
             // The keyValue, first the tag, then the value
             buffer.put( ( byte ) KerberosConstants.ENCRYPTION_KEY_VALUE_TAG );
             buffer.put( TLV.getBytes( keyValueLength ) );
             BerValue.encode( buffer, keyValue );
         }
         catch ( BufferOverflowException boe )
         {
             log.error( I18n.err( I18n.ERR_142, 1 + TLV.getNbBytes( encryptionKeyLength )
                 + encryptionKeyLength, buffer.capacity() ) );
             throw new EncoderException( I18n.err( I18n.ERR_138 ), boe );
         }
 
         if ( IS_DEBUG )
         {
             log.debug( "EncryptionKey encoding : {}", Strings.dumpBytes( buffer.array() ) );
             log.debug( "EncryptionKey initial value : {}", this );
         }
 
         return buffer;
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         return keyType.toString() + " (" + keyType.getValue() + ")";
     }
 }