Source for gnu.javax.crypto.pad.PKCS7

   1: /* PKCS7.java --
   2:  Copyright (C) 2001, 2002, 2006, 2010 Free Software Foundation, Inc.
   3: 
   4:  This file is a part of GNU Classpath.
   5: 
   6:  GNU Classpath is free software; you can redistribute it and/or modify
   7:  it under the terms of the GNU General Public License as published by
   8:  the Free Software Foundation; either version 2 of the License, or (at
   9:  your option) any later version.
  10: 
  11:  GNU Classpath is distributed in the hope that it will be useful, but
  12:  WITHOUT ANY WARRANTY; without even the implied warranty of
  13:  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14:  General Public License for more details.
  15: 
  16:  You should have received a copy of the GNU General Public License
  17:  along with GNU Classpath; if not, write to the Free Software
  18:  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19:  USA
  20: 
  21:  Linking this library statically or dynamically with other modules is
  22:  making a combined work based on this library.  Thus, the terms and
  23:  conditions of the GNU General Public License cover the whole
  24:  combination.
  25: 
  26:  As a special exception, the copyright holders of this library give you
  27:  permission to link this library with independent modules to produce an
  28:  executable, regardless of the license terms of these independent
  29:  modules, and to copy and distribute the resulting executable under
  30:  terms of your choice, provided that you also meet, for each linked
  31:  independent module, the terms and conditions of the license of that
  32:  module.  An independent module is a module which is not derived from
  33:  or based on this library.  If you modify this library, you may extend
  34:  this exception to your version of the library, but you are not
  35:  obligated to do so.  If you do not wish to do so, delete this
  36:  exception statement from your version.  */
  37: 
  38: 
  39: package gnu.javax.crypto.pad;
  40: 
  41: import gnu.java.security.Configuration;
  42: import gnu.java.security.Registry;
  43: import gnu.java.security.util.Util;
  44: 
  45: import java.util.logging.Logger;
  46: 
  47: /**
  48:  * The implementation of the PKCS7 padding algorithm.
  49:  * <p>
  50:  * This algorithm is described for 8-byte blocks in [RFC-1423] and extended to
  51:  * block sizes of up to 256 bytes in [PKCS-7].
  52:  * <p>
  53:  * References:
  54:  * <ol>
  55:  * <li><a href="http://www.ietf.org/rfc/rfc1423.txt">RFC-1423</a>: Privacy
  56:  * Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and
  57:  * Identifiers.</li>
  58:  * <li><a href="http://www.ietf.org/">IETF</a>.</li>
  59:  * <li><a href="http://www.rsasecurity.com/rsalabs/pkcs/pkcs-7/">[PKCS-7]</a>
  60:  * PKCS #7: Cryptographic Message Syntax Standard - An RSA Laboratories
  61:  * Technical Note.</li>
  62:  * <li><a href="http://www.rsasecurity.com/">RSA Security</a>.</li>
  63:  * </ol>
  64:  */
  65: public final class PKCS7
  66:     extends BasePad
  67: {
  68:   private static final Logger log = Configuration.DEBUG ?
  69:                         Logger.getLogger(PKCS7.class.getName()) : null;
  70: 
  71:   /**
  72:    * Trivial package-private constructor for use by the <i>Factory</i> class.
  73:    *
  74:    * @see PadFactory
  75:    */
  76:   PKCS7()
  77:   {
  78:     super(Registry.PKCS7_PAD);
  79:   }
  80: 
  81:   public void setup()
  82:   {
  83:     if (blockSize < 2 || blockSize > 256)
  84:       throw new IllegalArgumentException();
  85:   }
  86: 
  87:   public byte[] pad(byte[] in, int offset, int length)
  88:   {
  89:     int padLength = blockSize;
  90:     if (length % blockSize != 0)
  91:       padLength = blockSize - length % blockSize;
  92:     byte[] result = new byte[padLength];
  93:     for (int i = 0; i < padLength;)
  94:       result[i++] = (byte) padLength;
  95:     if (Configuration.DEBUG)
  96:       log.fine("padding: 0x" + Util.toString(result));
  97:     return result;
  98:   }
  99: 
 100:   public int unpad(byte[] in, int offset, int length)
 101:       throws WrongPaddingException
 102:   {
 103:     int limit = offset + length;
 104:     int result = in[--limit] & 0xFF;
 105:     for (int i = 0; i < result - 1; i++)
 106:       if (result != (in[--limit] & 0xFF))
 107:         throw new WrongPaddingException();
 108:     if (Configuration.DEBUG)
 109:       log.fine("padding length: " + result);
 110:     return result;
 111:   }
 112: }