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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 | +} | |