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Source code: gnu/javax/crypto/pad/BasePad.java


1   /* BasePad.java -- 
2      Copyright (C) 2001, 2002, 2003, 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   * <p>An abstract class to facilitate implementing padding algorithms.</p>
43   */
44  public abstract class BasePad implements IPad
45  {
46  
47    // Constants and variables
48    // -------------------------------------------------------------------------
49  
50    /** The canonical name prefix of the padding algorithm. */
51    protected String name;
52  
53    /** The block size, in bytes, for this instance. */
54    protected int blockSize;
55  
56    // Constructor(s)
57    // -------------------------------------------------------------------------
58  
59    /** Trivial constructor for use by concrete subclasses. */
60    protected BasePad(final String name)
61    {
62      super();
63  
64      this.name = name;
65      blockSize = -1;
66    }
67  
68    // Class methods
69    // -------------------------------------------------------------------------
70  
71    // Instance methods
72    // -------------------------------------------------------------------------
73  
74    // IPad interface implementation -------------------------------------------
75  
76    public String name()
77    {
78      final StringBuffer sb = new StringBuffer(name);
79      if (blockSize != -1)
80        {
81          sb.append('-').append(String.valueOf(8 * blockSize));
82        }
83      return sb.toString();
84    }
85  
86    public void init(final int bs) throws IllegalStateException
87    {
88      if (blockSize != -1)
89        {
90          throw new IllegalStateException();
91        }
92      blockSize = bs;
93      setup();
94    }
95  
96    public void reset()
97    {
98      blockSize = -1;
99    }
100 
101   public boolean selfTest()
102   {
103     byte[] padBytes;
104     final int offset = 5;
105     final int limit = 1024;
106     final byte[] in = new byte[limit];
107     for (int bs = 2; bs < 256; bs++)
108       {
109         this.init(bs);
110         for (int i = 0; i < limit - offset - blockSize; i++)
111           {
112             padBytes = pad(in, offset, i);
113             if (((i + padBytes.length) % blockSize) != 0)
114               {
115                 new RuntimeException(name()).printStackTrace(System.err);
116                 return false;
117               }
118 
119             System.arraycopy(padBytes, 0, in, offset + i, padBytes.length);
120             try
121               {
122                 if (padBytes.length != unpad(in, offset, i + padBytes.length))
123                   {
124                     new RuntimeException(name()).printStackTrace(System.err);
125                     return false;
126                   }
127               }
128             catch (WrongPaddingException x)
129               {
130                 x.printStackTrace(System.err);
131                 return false;
132               }
133           }
134         this.reset();
135       }
136 
137     return true;
138   }
139 
140   // abstract methods to implement by subclasses -----------------------------
141 
142   /**
143    * <p>If any additional checks or resource setup must be done by the
144    * subclass, then this is the hook for it. This method will be called before
145    * the {@link #init(int)} method returns.</p>
146    */
147   public abstract void setup();
148 
149   public abstract byte[] pad(byte[] in, int off, int len);
150 
151   public abstract int unpad(byte[] in, int off, int len)
152       throws WrongPaddingException;
153 }