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| 1 | +/* | |
| 2 | + * Copyright (c) 1997, 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 java.security.InvalidKeyException; | |
| 29 | + | |
| 30 | +/** | |
| 31 | + * This class represents ciphers in cipher-feedback (CFB) 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 | +final class CipherFeedback extends FeedbackCipher { | |
| 43 | + | |
| 44 | + /* | |
| 45 | + * encrypt/decrypt output buffer | |
| 46 | + */ | |
| 47 | + private final byte[] k; | |
| 48 | + | |
| 49 | + /* | |
| 50 | + * register value, initialized with iv | |
| 51 | + */ | |
| 52 | + private final byte[] register; | |
| 53 | + | |
| 54 | + /* | |
| 55 | + * number of bytes for each stream unit, defaults to the blocksize | |
| 56 | + * of the embedded cipher | |
| 57 | + */ | |
| 58 | + private int numBytes; | |
| 59 | + | |
| 60 | + // variables for save/restore calls | |
| 61 | + private byte[] registerSave = null; | |
| 62 | + | |
| 63 | + CipherFeedback(SymmetricCipher embeddedCipher, int numBytes) { | |
| 64 | + super(embeddedCipher); | |
| 65 | + if (numBytes > blockSize) { | |
| 66 | + numBytes = blockSize; | |
| 67 | + } | |
| 68 | + this.numBytes = numBytes; | |
| 69 | + k = new byte[blockSize]; | |
| 70 | + register = new byte[blockSize]; | |
| 71 | + } | |
| 72 | + | |
| 73 | + /** | |
| 74 | + * Gets the name of this feedback mode. | |
| 75 | + * | |
| 76 | + * @return the string <code>CFB</code> | |
| 77 | + */ | |
| 78 | + String getFeedback() { | |
| 79 | + return "CFB"; | |
| 80 | + } | |
| 81 | + | |
| 82 | + /** | |
| 83 | + * Initializes the cipher in the specified mode with the given key | |
| 84 | + * and iv. | |
| 85 | + * | |
| 86 | + * @param decrypting flag indicating encryption or decryption | |
| 87 | + * @param algorithm the algorithm name | |
| 88 | + * @param key the key | |
| 89 | + * @param iv the iv | |
| 90 | + * | |
| 91 | + * @exception InvalidKeyException if the given key is inappropriate for | |
| 92 | + * initializing this cipher | |
| 93 | + */ | |
| 94 | + void init(boolean decrypting, String algorithm, byte[] key, byte[] iv) | |
| 95 | + throws InvalidKeyException { | |
| 96 | + if ((key == null) || (iv == null) || (iv.length != blockSize)) { | |
| 97 | + throw new InvalidKeyException("Internal error"); | |
| 98 | + } | |
| 99 | + this.iv = iv; | |
| 100 | + reset(); | |
| 101 | + // always encrypt mode for embedded cipher | |
| 102 | + embeddedCipher.init(false, algorithm, key); | |
| 103 | + } | |
| 104 | + | |
| 105 | + /** | |
| 106 | + * Resets the iv to its original value. | |
| 107 | + * This is used when doFinal is called in the Cipher class, so that the | |
| 108 | + * cipher can be reused (with its original iv). | |
| 109 | + */ | |
| 110 | + void reset() { | |
| 111 | + System.arraycopy(iv, 0, register, 0, blockSize); | |
| 112 | + } | |
| 113 | + | |
| 114 | + /** | |
| 115 | + * Save the current content of this cipher. | |
| 116 | + */ | |
| 117 | + void save() { | |
| 118 | + if (registerSave == null) { | |
| 119 | + registerSave = new byte[blockSize]; | |
| 120 | + } | |
| 121 | + System.arraycopy(register, 0, registerSave, 0, blockSize); | |
| 122 | + } | |
| 123 | + | |
| 124 | + /** | |
| 125 | + * Restores the content of this cipher to the previous saved one. | |
| 126 | + */ | |
| 127 | + void restore() { | |
| 128 | + System.arraycopy(registerSave, 0, register, 0, blockSize); | |
| 129 | + } | |
| 130 | + | |
| 131 | + /** | |
| 132 | + * Performs encryption operation. | |
| 133 | + * | |
| 134 | + * <p>The input plain text <code>plain</code>, starting at | |
| 135 | + * <code>plainOffset</code> and ending at | |
| 136 | + * <code>(plainOffset + len - 1)</code>, is encrypted. | |
| 137 | + * The result is stored in <code>cipher</code>, starting at | |
| 138 | + * <code>cipherOffset</code>. | |
| 139 | + * | |
| 140 | + * <p>It is the application's responsibility to make sure that | |
| 141 | + * <code>plainLen</code> is a multiple of the stream unit size | |
| 142 | + * <code>numBytes</code>, as any excess bytes are ignored. | |
| 143 | + * | |
| 144 | + * <p>It is also the application's responsibility to make sure that | |
| 145 | + * <code>init</code> has been called before this method is called. | |
| 146 | + * (This check is omitted here, to avoid double checking.) | |
| 147 | + * | |
| 148 | + * @param plain the buffer with the input data to be encrypted | |
| 149 | + * @param plainOffset the offset in <code>plain</code> | |
| 150 | + * @param plainLen the length of the input data | |
| 151 | + * @param cipher the buffer for the result | |
| 152 | + * @param cipherOffset the offset in <code>cipher</code> | |
| 153 | + */ | |
| 154 | + void encrypt(byte[] plain, int plainOffset, int plainLen, | |
| 155 | + byte[] cipher, int cipherOffset) | |
| 156 | + { | |
| 157 | + int i, len; | |
| 158 | + len = blockSize - numBytes; | |
| 159 | + int loopCount = plainLen / numBytes; | |
| 160 | + int oddBytes = plainLen % numBytes; | |
| 161 | + | |
| 162 | + if (len == 0) { | |
| 163 | + for (; loopCount > 0 ; | |
| 164 | + plainOffset += numBytes, cipherOffset += numBytes, | |
| 165 | + loopCount--) { | |
| 166 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 167 | + for (i = 0; i < blockSize; i++) | |
| 168 | + register[i] = cipher[i+cipherOffset] = | |
| 169 | + (byte)(k[i] ^ plain[i+plainOffset]); | |
| 170 | + } | |
| 171 | + if (oddBytes > 0) { | |
| 172 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 173 | + for (i=0; i<oddBytes; i++) | |
| 174 | + register[i] = cipher[i+cipherOffset] = | |
| 175 | + (byte)(k[i] ^ plain[i+plainOffset]); | |
| 176 | + } | |
| 177 | + } else { | |
| 178 | + for (; loopCount > 0 ; | |
| 179 | + plainOffset += numBytes, cipherOffset += numBytes, | |
| 180 | + loopCount--) { | |
| 181 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 182 | + System.arraycopy(register, numBytes, register, 0, len); | |
| 183 | + for (i=0; i<numBytes; i++) | |
| 184 | + register[i+len] = cipher[i+cipherOffset] = | |
| 185 | + (byte)(k[i] ^ plain[i+plainOffset]); | |
| 186 | + | |
| 187 | + } | |
| 188 | + if (oddBytes != 0) { | |
| 189 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 190 | + System.arraycopy(register, numBytes, register, 0, len); | |
| 191 | + for (i=0; i<oddBytes; i++) { | |
| 192 | + register[i+len] = cipher[i+cipherOffset] = | |
| 193 | + (byte)(k[i] ^ plain[i+plainOffset]); | |
| 194 | + } | |
| 195 | + } | |
| 196 | + } | |
| 197 | + } | |
| 198 | + | |
| 199 | + /** | |
| 200 | + * Performs decryption operation. | |
| 201 | + * | |
| 202 | + * <p>The input cipher text <code>cipher</code>, starting at | |
| 203 | + * <code>cipherOffset</code> and ending at | |
| 204 | + * <code>(cipherOffset + len - 1)</code>, is decrypted. | |
| 205 | + * The result is stored in <code>plain</code>, starting at | |
| 206 | + * <code>plainOffset</code>. | |
| 207 | + * | |
| 208 | + * <p>It is the application's responsibility to make sure that | |
| 209 | + * <code>cipherLen</code> is a multiple of the stream unit size | |
| 210 | + * <code>numBytes</code>, as any excess bytes are ignored. | |
| 211 | + * | |
| 212 | + * <p>It is also the application's responsibility to make sure that | |
| 213 | + * <code>init</code> has been called before this method is called. | |
| 214 | + * (This check is omitted here, to avoid double checking.) | |
| 215 | + * | |
| 216 | + * @param cipher the buffer with the input data to be decrypted | |
| 217 | + * @param cipherOffset the offset in <code>cipherOffset</code> | |
| 218 | + * @param cipherLen the length of the input data | |
| 219 | + * @param plain the buffer for the result | |
| 220 | + * @param plainOffset the offset in <code>plain</code> | |
| 221 | + */ | |
| 222 | + void decrypt(byte[] cipher, int cipherOffset, int cipherLen, | |
| 223 | + byte[] plain, int plainOffset) | |
| 224 | + { | |
| 225 | + int i, len; | |
| 226 | + len = blockSize - numBytes; | |
| 227 | + int loopCount = cipherLen / numBytes; | |
| 228 | + int oddBytes = cipherLen % numBytes; | |
| 229 | + | |
| 230 | + if (len == 0) { | |
| 231 | + for (; loopCount > 0; | |
| 232 | + plainOffset += numBytes, cipherOffset += numBytes, | |
| 233 | + loopCount--) { | |
| 234 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 235 | + for (i = 0; i < blockSize; i++) { | |
| 236 | + register[i] = cipher[i+cipherOffset]; | |
| 237 | + plain[i+plainOffset] | |
| 238 | + = (byte)(cipher[i+cipherOffset] ^ k[i]); | |
| 239 | + } | |
| 240 | + } | |
| 241 | + if (oddBytes > 0) { | |
| 242 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 243 | + for (i=0; i<oddBytes; i++) { | |
| 244 | + register[i] = cipher[i+cipherOffset]; | |
| 245 | + plain[i+plainOffset] | |
| 246 | + = (byte)(cipher[i+cipherOffset] ^ k[i]); | |
| 247 | + } | |
| 248 | + } | |
| 249 | + } else { | |
| 250 | + for (; loopCount > 0; | |
| 251 | + plainOffset += numBytes, cipherOffset += numBytes, | |
| 252 | + loopCount--) { | |
| 253 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 254 | + System.arraycopy(register, numBytes, register, 0, len); | |
| 255 | + for (i=0; i<numBytes; i++) { | |
| 256 | + register[i+len] = cipher[i+cipherOffset]; | |
| 257 | + plain[i+plainOffset] | |
| 258 | + = (byte)(cipher[i+cipherOffset] ^ k[i]); | |
| 259 | + } | |
| 260 | + } | |
| 261 | + if (oddBytes != 0) { | |
| 262 | + embeddedCipher.encryptBlock(register, 0, k, 0); | |
| 263 | + System.arraycopy(register, numBytes, register, 0, len); | |
| 264 | + for (i=0; i<oddBytes; i++) { | |
| 265 | + register[i+len] = cipher[i+cipherOffset]; | |
| 266 | + plain[i+plainOffset] | |
| 267 | + = (byte)(cipher[i+cipherOffset] ^ k[i]); | |
| 268 | + } | |
| 269 | + } | |
| 270 | + } | |
| 271 | + } | |
| 272 | +} | |