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| 1 | /* | ||
| 2 | * Copyright (c) 2004, 2007, 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 javax.crypto.IllegalBlockSizeException; | ||
| 29 | import javax.crypto.ShortBufferException; | ||
| 30 | |||
| 31 | /** | ||
| 32 | * This class represents ciphers in cipher text stealing (CTS) mode. | ||
| 33 | * <br>CTS provides a way to allow block ciphers to operate on partial | ||
| 34 | * blocks without padding, and all bits of the message go through | ||
| 35 | * the encryption algorithm, rather than simply being XOR'd. | ||
| 36 | * <br>More details can be found in RFC 2040 section 8 "Description | ||
| 37 | * of RC5-CTS". | ||
| 38 | * | ||
| 39 | * <p>This mode is implemented independently of a particular cipher. | ||
| 40 | * Ciphers to which this mode should apply (e.g., DES) must be | ||
| 41 | * <i>plugged-in</i> using the constructor. | ||
| 42 | * | ||
| 43 | * <p>NOTE#1: CTS requires the input data to be at least one block | ||
| 44 | * long. Thus, callers of this class has to buffer the input data | ||
| 45 | * to make sure the input data passed to encryptFinal()/decryptFinal() | ||
| 46 | * is not shorter than a block. | ||
| 47 | * <p>NOTE#2: This class does not deal with buffering or padding | ||
| 48 | * just like all other cipher mode implementations. | ||
| 49 | * | ||
| 50 | * @author Valerie Peng | ||
| 51 | */ | ||
| 52 | |||
| 53 | final class CipherTextStealing extends CipherBlockChaining { | ||
| 54 | |||
| 55 | CipherTextStealing(SymmetricCipher embeddedCipher) { | ||
| 56 | super(embeddedCipher); | ||
| 57 | } | ||
| 58 | |||
| 59 | /** | ||
| 60 | * Gets the name of this feedback mode. | ||
| 61 | * | ||
| 62 | * @return the string <code>CBC</code> | ||
| 63 | */ | ||
| 64 | String getFeedback() { | ||
| 65 | return "CTS"; | ||
| 66 | } | ||
| 67 | |||
| 68 | /** | ||
| 69 | * Performs the last encryption operation. | ||
| 70 | * | ||
| 71 | * <p>The input plain text <code>plain</code>, starting at | ||
| 72 | * <code>plainOffset</code> and ending at | ||
| 73 | * <code>(plainOffset + len - 1)</code>, is encrypted. | ||
| 74 | * The result is stored in <code>cipher</code>, starting at | ||
| 75 | * <code>cipherOffset</code>. | ||
| 76 | * | ||
| 77 | * <p>It is the application's responsibility to make sure that | ||
| 78 | * <code>plainLen</code> is a multiple of the embedded cipher's block size, | ||
| 79 | * as any excess bytes are ignored. | ||
| 80 | * | ||
| 81 | * @param plain the buffer with the input data to be encrypted | ||
| 82 | * @param plainOffset the offset in <code>plain</code> | ||
| 83 | * @param plainLen the length of the input data | ||
| 84 | * @param cipher the buffer for the result | ||
| 85 | * @param cipherOffset the offset in <code>cipher</code> | ||
| 86 | */ | ||
| 87 | void encryptFinal(byte[] plain, int plainOffset, int plainLen, | ||
| 88 | byte[] cipher, int cipherOffset) | ||
| 89 | throws IllegalBlockSizeException { | ||
| 90 | |||
| 91 | if (plainLen < blockSize) { | ||
| 92 | throw new IllegalBlockSizeException("input is too short!"); | ||
| 93 | } else if (plainLen == blockSize) { | ||
| 94 | encrypt(plain, plainOffset, plainLen, cipher, cipherOffset); | ||
| 95 | } else { | ||
| 96 | // number of bytes in the last block | ||
| 97 | int nLeft = plainLen % blockSize; | ||
| 98 | if (nLeft == 0) { | ||
| 99 | encrypt(plain, plainOffset, plainLen, cipher, cipherOffset); | ||
| 100 | // swap the last two blocks after encryption | ||
| 101 | int lastBlkIndex = cipherOffset + plainLen - blockSize; | ||
| 102 | int nextToLastBlkIndex = lastBlkIndex - blockSize; | ||
| 103 | byte[] tmp = new byte[blockSize]; | ||
| 104 | System.arraycopy(cipher, lastBlkIndex, tmp, 0, blockSize); | ||
| 105 | System.arraycopy(cipher, nextToLastBlkIndex, | ||
| 106 | cipher, lastBlkIndex, blockSize); | ||
| 107 | System.arraycopy(tmp, 0, cipher, nextToLastBlkIndex, | ||
| 108 | blockSize); | ||
| 109 | } else { | ||
| 110 | int newPlainLen = plainLen - (blockSize + nLeft); | ||
| 111 | if (newPlainLen > 0) { | ||
| 112 | encrypt(plain, plainOffset, newPlainLen, cipher, | ||
| 113 | cipherOffset); | ||
| 114 | plainOffset += newPlainLen; | ||
| 115 | cipherOffset += newPlainLen; | ||
| 116 | } | ||
| 117 | |||
| 118 | // Do final CTS step for last two blocks (the second of which | ||
| 119 | // may or may not be incomplete). | ||
| 120 | byte[] tmp = new byte[blockSize]; | ||
| 121 | // now encrypt the next-to-last block | ||
| 122 | for (int i = 0; i < blockSize; i++) { | ||
| 123 | tmp[i] = (byte) (plain[plainOffset+i] ^ r[i]); | ||
| 124 | } | ||
| 125 | byte[] tmp2 = new byte[blockSize]; | ||
| 126 | embeddedCipher.encryptBlock(tmp, 0, tmp2, 0); | ||
| 127 | System.arraycopy(tmp2, 0, cipher, | ||
| 128 | cipherOffset+blockSize, nLeft); | ||
| 129 | // encrypt the last block | ||
| 130 | for (int i=0; i<nLeft; i++) { | ||
| 131 | tmp2[i] = (byte) | ||
| 132 | (plain[plainOffset+blockSize+i] ^ tmp2[i]); | ||
| 133 | } | ||
| 134 | embeddedCipher.encryptBlock(tmp2, 0, cipher, cipherOffset); | ||
| 135 | } | ||
| 136 | } | ||
| 137 | } | ||
| 138 | |||
| 139 | /** | ||
| 140 | * Performs decryption operation. | ||
| 141 | * | ||
| 142 | * <p>The input cipher text <code>cipher</code>, starting at | ||
| 143 | * <code>cipherOffset</code> and ending at | ||
| 144 | * <code>(cipherOffset + len - 1)</code>, is decrypted. | ||
| 145 | * The result is stored in <code>plain</code>, starting at | ||
| 146 | * <code>plainOffset</code>. | ||
| 147 | * | ||
| 148 | * <p>It is the application's responsibility to make sure that | ||
| 149 | * <code>cipherLen</code> is a multiple of the embedded cipher's block | ||
| 150 | * size, as any excess bytes are ignored. | ||
| 151 | * | ||
| 152 | * <p>It is also the application's responsibility to make sure that | ||
| 153 | * <code>init</code> has been called before this method is called. | ||
| 154 | * (This check is omitted here, to avoid double checking.) | ||
| 155 | * | ||
| 156 | * @param cipher the buffer with the input data to be decrypted | ||
| 157 | * @param cipherOffset the offset in <code>cipherOffset</code> | ||
| 158 | * @param cipherLen the length of the input data | ||
| 159 | * @param plain the buffer for the result | ||
| 160 | * @param plainOffset the offset in <code>plain</code> | ||
| 161 | */ | ||
| 162 | void decryptFinal(byte[] cipher, int cipherOffset, int cipherLen, | ||
| 163 | byte[] plain, int plainOffset) | ||
| 164 | throws IllegalBlockSizeException { | ||
| 165 | if (cipherLen < blockSize) { | ||
| 166 | throw new IllegalBlockSizeException("input is too short!"); | ||
| 167 | } else if (cipherLen == blockSize) { | ||
| 168 | decrypt(cipher, cipherOffset, cipherLen, plain, plainOffset); | ||
| 169 | } else { | ||
| 170 | // number of bytes in the last block | ||
| 171 | int nLeft = cipherLen % blockSize; | ||
| 172 | if (nLeft == 0) { | ||
| 173 | // swap the last two blocks before decryption | ||
| 174 | int lastBlkIndex = cipherOffset + cipherLen - blockSize; | ||
| 175 | int nextToLastBlkIndex = | ||
| 176 | cipherOffset + cipherLen - 2*blockSize; | ||
| 177 | byte[] tmp = new byte[2*blockSize]; | ||
| 178 | System.arraycopy(cipher, lastBlkIndex, tmp, 0, blockSize); | ||
| 179 | System.arraycopy(cipher, nextToLastBlkIndex, | ||
| 180 | tmp, blockSize, blockSize); | ||
| 181 | int cipherLen2 = cipherLen-2*blockSize; | ||
| 182 | decrypt(cipher, cipherOffset, cipherLen2, plain, plainOffset); | ||
| 183 | decrypt(tmp, 0, 2*blockSize, plain, plainOffset+cipherLen2); | ||
| 184 | } else { | ||
| 185 | int newCipherLen = cipherLen-(blockSize+nLeft); | ||
| 186 | if (newCipherLen > 0) { | ||
| 187 | decrypt(cipher, cipherOffset, newCipherLen, plain, | ||
| 188 | plainOffset); | ||
| 189 | cipherOffset += newCipherLen; | ||
| 190 | plainOffset += newCipherLen; | ||
| 191 | } | ||
| 192 | // Do final CTS step for last two blocks (the second of which | ||
| 193 | // may or may not be incomplete). | ||
| 194 | |||
| 195 | // now decrypt the next-to-last block | ||
| 196 | byte[] tmp = new byte[blockSize]; | ||
| 197 | embeddedCipher.decryptBlock(cipher, cipherOffset, tmp, 0); | ||
| 198 | for (int i = 0; i < nLeft; i++) { | ||
| 199 | plain[plainOffset+blockSize+i] = | ||
| 200 | (byte) (cipher[cipherOffset+blockSize+i] ^ tmp[i]); | ||
| 201 | } | ||
| 202 | |||
| 203 | // decrypt the last block | ||
| 204 | System.arraycopy(cipher, cipherOffset+blockSize, tmp, 0, | ||
| 205 | nLeft); | ||
| 206 | embeddedCipher.decryptBlock(tmp, 0, plain, plainOffset); | ||
| 207 | //System.arraycopy(r, 0, tmp, 0, r.length); | ||
| 208 | for (int i=0; i<blockSize; i++) { | ||
| 209 | plain[plainOffset+i] = (byte) | ||
| 210 | (plain[plainOffset+i]^r[i]); | ||
| 211 | } | ||
| 212 | } | ||
| 213 | } | ||
| 214 | } | ||
| 215 | } | ||