1 /* 2 * Copyright (c) 1997, 2014, 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 import java.security.ProviderException; 30 31 32 /** 33 * This class represents ciphers in cipher block chaining (CBC) mode. 34 * 35 * <p>This mode is implemented independently of a particular cipher. 36 * Ciphers to which this mode should apply (e.g., DES) must be 37 * <i>plugged-in</i> using the constructor. 38 * 39 * <p>NOTE: This class does not deal with buffering or padding. 40 * 41 * @author Gigi Ankeny 42 */ 43 44 class CipherBlockChaining extends FeedbackCipher { 45 46 /* 47 * random bytes that are initialized with iv 48 */ 49 protected byte[] r; 50 51 /* 52 * output buffer 53 */ 54 private byte[] k; 55 56 // variables for save/restore calls 57 private byte[] rSave = null; 58 59 CipherBlockChaining(SymmetricCipher embeddedCipher) { 60 super(embeddedCipher); 61 k = new byte[blockSize]; 62 r = new byte[blockSize]; 63 } 64 65 /** 66 * Gets the name of this feedback mode. 67 * 68 * @return the string <code>CBC</code> 69 */ 70 String getFeedback() { 71 return "CBC"; 72 } 73 74 /** 75 * Initializes the cipher in the specified mode with the given key 76 * and iv. 77 * 78 * @param decrypting flag indicating encryption or decryption 79 * @param algorithm the algorithm name 80 * @param key the key 81 * @param iv the iv 82 * 83 * @exception InvalidKeyException if the given key is inappropriate for 84 * initializing this cipher 85 */ 86 void init(boolean decrypting, String algorithm, byte[] key, byte[] iv) 87 throws InvalidKeyException { 88 if ((key == null) || (iv == null) || (iv.length != blockSize)) { 89 throw new InvalidKeyException("Internal error"); 90 } 91 this.iv = iv; 92 reset(); 93 embeddedCipher.init(decrypting, algorithm, key); 94 } 95 96 /** 97 * Resets the iv to its original value. 98 * This is used when doFinal is called in the Cipher class, so that the 99 * cipher can be reused (with its original iv). 100 */ 101 void reset() { 102 System.arraycopy(iv, 0, r, 0, blockSize); 103 } 104 105 /** 106 * Save the current content of this cipher. 107 */ 108 void save() { 109 if (rSave == null) { 110 rSave = new byte[blockSize]; 111 } 112 System.arraycopy(r, 0, rSave, 0, blockSize); 113 } 114 115 /** 116 * Restores the content of this cipher to the previous saved one. 117 */ 118 void restore() { 119 System.arraycopy(rSave, 0, r, 0, blockSize); 120 } 121 122 /** 123 * Performs encryption operation. 124 * 125 * <p>The input plain text <code>plain</code>, starting at 126 * <code>plainOffset</code> and ending at 127 * <code>(plainOffset + plainLen - 1)</code>, is encrypted. 128 * The result is stored in <code>cipher</code>, starting at 129 * <code>cipherOffset</code>. 130 * 131 * @param plain the buffer with the input data to be encrypted 132 * @param plainOffset the offset in <code>plain</code> 133 * @param plainLen the length of the input data 134 * @param cipher the buffer for the result 135 * @param cipherOffset the offset in <code>cipher</code> 136 * @exception ProviderException if <code>len</code> is not 137 * a multiple of the block size 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 if ((plainLen % blockSize) != 0) { 144 throw new ProviderException("Internal error in input buffering"); 145 } 146 int endIndex = plainOffset + plainLen; 147 148 for (; plainOffset < endIndex; 149 plainOffset+=blockSize, cipherOffset += blockSize) { 150 for (int i = 0; i < blockSize; i++) { 151 k[i] = (byte)(plain[i + plainOffset] ^ r[i]); 152 } 153 embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset); 154 System.arraycopy(cipher, cipherOffset, r, 0, blockSize); 155 } 156 return plainLen; 157 } 158 159 /** 160 * Performs decryption operation. 161 * 162 * <p>The input cipher text <code>cipher</code>, starting at 163 * <code>cipherOffset</code> and ending at 164 * <code>(cipherOffset + cipherLen - 1)</code>, is decrypted. 165 * The result is stored in <code>plain</code>, starting at 166 * <code>plainOffset</code>. 167 * 168 * <p>It is also the application's responsibility to make sure that 169 * <code>init</code> has been called before this method is called. 170 * (This check is omitted here, to avoid double checking.) 171 * 172 * @param cipher the buffer with the input data to be decrypted 173 * @param cipherOffset the offset in <code>cipherOffset</code> 174 * @param cipherLen the length of the input data 175 * @param plain the buffer for the result 176 * @param plainOffset the offset in <code>plain</code> 177 * @exception ProviderException if <code>len</code> is not 178 * a multiple of the block size 179 * @return the length of the decrypted data 180 */ 181 int decrypt(byte[] cipher, int cipherOffset, int cipherLen, 182 byte[] plain, int plainOffset) 183 { 184 if ((cipherLen % blockSize) != 0) { 185 throw new ProviderException("Internal error in input buffering"); 186 } 187 int endIndex = cipherOffset + cipherLen; 188 189 for (; cipherOffset < endIndex; 190 cipherOffset += blockSize, plainOffset += blockSize) { 191 embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0); 192 for (int i = 0; i < blockSize; i++) { 193 plain[i + plainOffset] = (byte)(k[i] ^ r[i]); 194 } 195 System.arraycopy(cipher, cipherOffset, r, 0, blockSize); 196 } 197 return cipherLen; 198 } 199 }