Source for gnu.javax.crypto.pad.TLS1

   1: /* TLS1.java -- TLSv1 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 Transport Layer Security protocol, version 1.
  43:  * This padding scheme is used in the block-ciphered struct, e.g.:
  44:  * <pre>
  45:  *  block-ciphered struct {
  46:  *    opaque content[TLSCompressed.length];
  47:  *    opaque MAC[CipherSpec.hash_size];
  48:  *    uint8 padding[GenericBlockCipher.padding_length];
  49:  *    uint8 padding_length;
  50:  *  } GenericBlockCipher;
  51:  * </pre>
  52:  * <p>
  53:  * Where <i>padding_length</i> is any multiple of <i>cipher_block_size</i> -
  54:  * ((<i>SSLCompressed.length</i> + <i>CipherSpec.hash_size</i>) %
  55:  * <i>cipher_block_size</i>) - 1 that is less than 255. Every byte of the
  56:  * padding must be equal to <i>padding_length</i>. That is, the end of the
  57:  * plaintext is <i>n</i> + 1 copies of the unsigned byte <i>n</i>.
  58:  */
  59: public class TLS1
  60:     extends BasePad
  61: {
  62:   public TLS1()
  63:   {
  64:     super("tls1");
  65:   }
  66: 
  67:   public void setup()
  68:   {
  69:     if (blockSize <= 0 || blockSize > 255)
  70:       throw new IllegalArgumentException("invalid block size: " + blockSize);
  71:   }
  72: 
  73:   public byte[] pad(final byte[] in, final int off, final int len)
  74:   {
  75:     int padlen = blockSize - (len % blockSize);
  76:     byte[] pad = new byte[padlen];
  77:     for (int i = 0; i < padlen; i++)
  78:       pad[i] = (byte)(padlen - 1);
  79:     return pad;
  80:   }
  81: 
  82:   public int unpad(final byte[] in, final int off, final int len)
  83:       throws WrongPaddingException
  84:   {
  85:     int padlen = in[off + len - 1] & 0xFF;
  86:     for (int i = off + (len - padlen - 1); i < off + len - 1; i++)
  87:       if ((in[i] & 0xFF) != padlen)
  88:         throw new WrongPaddingException();
  89:     return padlen + 1;
  90:   }
  91: }