1 /*

     2  * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package com.sun.crypto.provider;

    27 

    28 import java.security.InvalidKeyException;

    29 

    30 /**

    31  * This class represents ciphers in cipher block chaining (CBC) mode.

    32  *

    33  * <p>This mode is implemented independently of a particular cipher.

    34  * Ciphers to which this mode should apply (e.g., DES) must be

    35  * <i>plugged-in</i> using the constructor.

    36  *

    37  * <p>NOTE: This class does not deal with buffering or padding.

    38  *

    39  * @author Gigi Ankeny

    40  */

    41 

    42 class CipherBlockChaining extends FeedbackCipher  {

    43 

    44     /*

    45      * random bytes that are initialized with iv

    46      */

    47     protected byte[] r;

    48 

    49     /*

    50      * output buffer

    51      */

    52     private byte[] k;

    53 

    54     // variables for save/restore calls

    55     private byte[] rSave = null;

    56 

    57     CipherBlockChaining(SymmetricCipher embeddedCipher) {

    58         super(embeddedCipher);

    59         k = new byte[blockSize];

    60         r = new byte[blockSize];

    61     }

    62 

    63     /**

    64      * Gets the name of this feedback mode.

    65      *

    66      * @return the string <code>CBC</code>

    67      */

    68     String getFeedback() {

    69         return "CBC";

    70     }

    71 

    72     /**

    73      * Initializes the cipher in the specified mode with the given key

    74      * and iv.

    75      *

    76      * @param decrypting flag indicating encryption or decryption

    77      * @param algorithm the algorithm name

    78      * @param key the key

    79      * @param iv the iv

    80      *

    81      * @exception InvalidKeyException if the given key is inappropriate for

    82      * initializing this cipher

    83      */

    84     void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)

    85             throws InvalidKeyException {

    86         if ((key == null) || (iv == null) || (iv.length != blockSize)) {

    87             throw new InvalidKeyException("Internal error");

    88         }

    89         this.iv = iv;

    90         reset();

    91         embeddedCipher.init(decrypting, algorithm, key);

    92     }

    93 

    94     /**

    95      * Resets the iv to its original value.

    96      * This is used when doFinal is called in the Cipher class, so that the

    97      * cipher can be reused (with its original iv).

    98      */

    99     void reset() {

   100         System.arraycopy(iv, 0, r, 0, blockSize);

   101     }

   102 

   103     /**

   104      * Save the current content of this cipher.

   105      */

   106     void save() {

   107         if (rSave == null) {

   108             rSave = new byte[blockSize];

   109         }

   110         System.arraycopy(r, 0, rSave, 0, blockSize);

   111     }

   112 

   113     /**

   114      * Restores the content of this cipher to the previous saved one.

   115      */

   116     void restore() {

   117         System.arraycopy(rSave, 0, r, 0, blockSize);

   118     }

   119 

   120     /**

   121      * Performs encryption operation.

   122      *

   123      * <p>The input plain text <code>plain</code>, starting at

   124      * <code>plainOffset</code> and ending at

   125      * <code>(plainOffset + len - 1)</code>, is encrypted.

   126      * The result is stored in <code>cipher</code>, starting at

   127      * <code>cipherOffset</code>.

   128      *

   129      * <p>It is the application's responsibility to make sure that

   130      * <code>plainLen</code> is a multiple of the embedded cipher's block size,

   131      * as any excess bytes are ignored.

   132      *

   133      * @param plain the buffer with the input data to be encrypted

   134      * @param plainOffset the offset in <code>plain</code>

   135      * @param plainLen the length of the input data

   136      * @param cipher the buffer for the result

   137      * @param cipherOffset the offset in <code>cipher</code>

   138      * @return the length of the encrypted data

   139      */

   140     int encrypt(byte[] plain, int plainOffset, int plainLen,

   141                 byte[] cipher, int cipherOffset)

   142     {

   143         int i;

   144         int endIndex = plainOffset + plainLen;

   145 

   146         for (; plainOffset < endIndex;

   147              plainOffset+=blockSize, cipherOffset += blockSize) {

   148             for (i=0; i<blockSize; i++) {

   149                 k[i] = (byte)(plain[i+plainOffset] ^ r[i]);

   150             }

   151             embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);

   152             System.arraycopy(cipher, cipherOffset, r, 0, blockSize);

   153         }

   154         return plainLen;

   155     }

   156 

   157     /**

   158      * Performs decryption operation.

   159      *

   160      * <p>The input cipher text <code>cipher</code>, starting at

   161      * <code>cipherOffset</code> and ending at

   162      * <code>(cipherOffset + len - 1)</code>, is decrypted.

   163      * The result is stored in <code>plain</code>, starting at

   164      * <code>plainOffset</code>.

   165      *

   166      * <p>It is the application's responsibility to make sure that

   167      * <code>cipherLen</code> is a multiple of the embedded cipher's block

   168      * size, as any excess bytes are ignored.

   169      *

   170      * <p>It is also the application's responsibility to make sure that

   171      * <code>init</code> has been called before this method is called.

   172      * (This check is omitted here, to avoid double checking.)

   173      *

   174      * @param cipher the buffer with the input data to be decrypted

   175      * @param cipherOffset the offset in <code>cipherOffset</code>

   176      * @param cipherLen the length of the input data

   177      * @param plain the buffer for the result

   178      * @param plainOffset the offset in <code>plain</code>

   179      * @return the length of the decrypted data

   180      *

   181      * @exception IllegalBlockSizeException if input data whose length does

   182      * not correspond to the embedded cipher's block size is passed to the

   183      * embedded cipher

   184      */

   185     int decrypt(byte[] cipher, int cipherOffset, int cipherLen,

   186                 byte[] plain, int plainOffset)

   187     {

   188         int i;

   189         int endIndex = cipherOffset + cipherLen;

   190 

   191         for (; cipherOffset < endIndex;

   192              cipherOffset += blockSize, plainOffset += blockSize) {

   193             embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0);

   194             for (i = 0; i < blockSize; i++) {

   195                 plain[i+plainOffset] = (byte)(k[i] ^ r[i]);

   196             }

   197             System.arraycopy(cipher, cipherOffset, r, 0, blockSize);

   198         }

   199         return cipherLen;

   200     }

   201 }