libjava/classpath/gnu/javax/crypto/pad/SSL3.java

   1 /* SSL3.java -- SSLv3 padding scheme.
   2    Copyright (C) 2004, 2006 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 /**
  42  * The padding scheme used by the Secure Sockets Layer, version 3. This
  43  * padding scheme is used in the block-ciphered struct, e.g.:
  44  *
  45  * <pre>
  46  * block-ciphered struct {
  47  *   opaque content[SSLCompressed.length];
  48  *   opaque MAC[CipherSpec.hash_size];
  49  *   uint8 padding[GenericBlockCipher.padding_length];
  50  *   uint8 padding_length;
  51  * } GenericBlockCipher;
  52  * </pre>
  53  *
  54  * <p>Where <i>padding_length</i> is <i>cipher_block_size</i> -
  55  * ((<i>SSLCompressed.length</i> + <i>CipherSpec.hash_size</i>)
  56  * % <i>cipher_block_size</i>) - 1. That is, the padding is enough bytes
  57  * to make the plaintext a multiple of the block size minus one, plus one
  58  * additional byte for the padding length. The padding can be any arbitrary
  59  * data.</p>
  60  */
  61 public class SSL3 extends BasePad
  62 {
  63
  64   // Constructors.
  65   // -------------------------------------------------------------------------
  66
  67   public SSL3()
  68   {
  69     super("ssl3");
  70   }
  71
  72   // Instance methods.
  73   // -------------------------------------------------------------------------
  74
  75   public void setup()
  76   {
  77     if (blockSize <= 0 || blockSize > 255)
  78       throw new IllegalArgumentException("invalid block size: " + blockSize);
  79   }
  80
  81   public byte[] pad(final byte[] in, final int off, final int len)
  82   {
  83     int padlen = blockSize - (len % blockSize);
  84     byte[] pad = new byte[padlen];
  85     for (int i = 0; i < padlen; i++)
  86       pad[i] = (byte) (padlen - 1);
  87     return pad;
  88   }
  89
  90   public int unpad(final byte[] in, final int off, final int len)
  91       throws WrongPaddingException
  92   {
  93     int padlen = in[off + len - 1] & 0xFF;
  94     if (padlen >= blockSize)
  95       throw new WrongPaddingException();
  96     return padlen + 1;
  97   }
  98 }