/*
    *  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.keytab;
  
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.nio.channels.Channels;
  import java.nio.channels.WritableByteChannel;
  import java.nio.file.Files;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.directory.server.i18n.I18n;
  
  
  /**
   * Keytab file. The format is the following :
   * <pre>
   * { 
   *   version : 2 bytes (0x05 0x02)
   *   keytabEntry*
   * }
   *
   * keytab_entry 
   * {
   *     size : int
   *     numComponents :  short
   *     realm : countedOctetString
   *     components[numComponents] : countedOctetString
   *     nameType : int
   *     timestamp : int
   *     vno8 : byte
   *     key : keyBlock
   *     vno : int // only present if &gt;= 4 bytes left in entry
   * };
   *
   * keyblock 
   * {
   *     type : int
   *     data : countedOctetString
   * }
   *
   * countedOctetString 
   * {
   *     length : short
   *     data[length] : bytes
   * }
   * </pre>
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class Keytab
  {
      /**
       * Byte array constant for keytab file format 5.1.
       */
      public static final byte[] VERSION_0X501_BYTES = new byte[]
          { ( byte ) 0x05, ( byte ) 0x01 };
  
      // Format 0x0501
      public static final short VERSION_0X501 = 0x0501;
  
      /**
       * Byte array constant for keytab file format 5.2.
       */
      public static final byte[] VERSION_0X502_BYTES = new byte[]
          { ( byte ) 0x05, ( byte ) 0x02 };
  
      // Format 0x0502
      public static final short VERSION_0X502 = 0x0502;
  
      private byte[] keytabVersion = VERSION_0X502_BYTES;
      private List<KeytabEntry> entries = new ArrayList<>();
  
  
      /**
       * Read a keytab file.
      *
      * @param file
      * @return The keytab.
      * @throws IOException
      */
     public static Keytab read( File file ) throws IOException
     {
         ByteBuffer buffer = ByteBuffer.wrap( getBytesFromFile( file ) );
         return readKeytab( buffer );
     }
 
 
     /**
      * Returns a new instance of a keytab with the version
      * defaulted to 5.2.
      *
      * @return The keytab.
      */
     public static Keytab getInstance()
     {
         return new Keytab();
     }
 
 
     /**
      * Write the keytab to a {@link File}.
      *
      * @param file
      * @throws IOException
      */
     public void write( File file ) throws IOException
     {
         KeytabEncoderr/kerberos/shared/keytab/KeytabEncoder.html#KeytabEncoder">KeytabEncoder writer = new KeytabEncoder();
         ByteBuffer buffer = writer.write( keytabVersion, entries );
         writeFile( buffer, file );
     }
 
 
     /**
      * @param entries The entries to set.
      */
     public void setEntries( List<KeytabEntry> entries )
     {
         this.entries = entries;
     }
 
 
     /**
      * @param keytabVersion The keytabVersion to set.
      */
     public void setKeytabVersion( byte[] keytabVersion )
     {
         this.keytabVersion = keytabVersion;
     }
 
 
     /**
      * @return The entries.
      */
     public List<KeytabEntry> getEntries()
     {
         return Collections.unmodifiableList( entries );
     }
 
 
     /**
      * @return The keytabVersion.
      */
     public byte[] getKeytabVersion()
     {
         return keytabVersion;
     }
 
 
     /**
      * Read bytes into a keytab.
      *
      * @param bytes
      * @return The keytab.
      */
     static Keytab read( byte[] bytes ) throws IOException
     {
         ByteBuffer buffer = ByteBuffer.wrap( bytes );
         return readKeytab( buffer );
     }
 
 
     /**
      * Write the keytab to a {@link ByteBuffer}.
      * @return The buffer.
      */
     ByteBuffer write()
     {
         KeytabEncoderr/kerberos/shared/keytab/KeytabEncoder.html#KeytabEncoder">KeytabEncoder writer = new KeytabEncoder();
         return writer.write( keytabVersion, entries );
     }
 
 
     /**
      * Read the contents of the buffer into a keytab.
      *
      * @param buffer
      * @return The keytab.
      */
     private static Keytab readKeytab( ByteBuffer buffer ) throws IOException
     {
         KeytabDecoderr/kerberos/shared/keytab/KeytabDecoder.html#KeytabDecoder">KeytabDecoder reader = new KeytabDecoder();
         byte[] keytabVersion = reader.getKeytabVersion( buffer );
         List<KeytabEntry> entries = reader.getKeytabEntries( buffer );
 
         Keytaby/server/kerberos/shared/keytab/Keytab.html#Keytab">Keytab keytab = new Keytab();
 
         keytab.setKeytabVersion( keytabVersion );
         keytab.setEntries( entries );
 
         return keytab;
     }
 
 
     /**
      * Returns the contents of the {@link File} in a byte array.
      *
      * @param file
      * @return The byte array of the file contents.
      * @throws IOException
      */
     protected static byte[] getBytesFromFile( File file ) throws IOException
     {
         try ( InputStream is = Files.newInputStream( file.toPath() ) )
         {
 
             long length = file.length();
 
             // Check to ensure that file is not larger than Integer.MAX_VALUE.
             if ( length > Integer.MAX_VALUE )
             {
                 throw new IOException( I18n.err( I18n.ERR_618, file.getName() ) );
             }
 
             // Create the byte array to hold the data.
             byte[] bytes = new byte[( int ) length];
 
             // Read in the bytes
             int offset = 0;
             int numRead = 0;
             while ( offset < bytes.length && ( numRead = is.read( bytes, offset, bytes.length - offset ) ) >= 0 )
             {
                 offset += numRead;
             }
 
             // Ensure all the bytes have been read in.
             if ( offset < bytes.length )
             {
                 throw new IOException( I18n.err( I18n.ERR_619, file.getName() ) );
             }
 
             return bytes;
         }
     }
 
 
     /**
      * Write the contents of the {@link ByteBuffer} to a {@link File}.
      *
      * @param buffer
      * @param file
      * @throws IOException
      */
     protected void writeFile( ByteBuffer buffer, File file ) throws IOException
     {
         // Set append false to replace existing.
         OutputStream out = Files.newOutputStream( file.toPath() );
 
         try ( WritableByteChannel channel = Channels.newChannel( out ) )
         {
             // Write the bytes between the position and limit.
             channel.write( buffer );
         }
         finally
         {
             out.close();
         }
     }
 }