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 26package com.sun.crypto.provider; 27 28import java.security.InvalidKeyException; 29import java.security.ProviderException; 30 31/** 32 * This class represents ciphers in cipher-feedback (CFB) mode. 33 * 34 * <p>This mode is implemented independently of a particular cipher. 35 * Ciphers to which this mode should apply (e.g., DES) must be 36 * <i>plugged-in</i> using the constructor. 37 * 38 * <p>NOTE: This class does not deal with buffering or padding. 39 * 40 * @author Gigi Ankeny 41 */ 42 43final class CipherFeedback extends FeedbackCipher { 44 45 /* 46 * encrypt/decrypt output buffer 47 */ 48 private final byte[] k; 49 50 /* 51 * register value, initialized with iv 52 */ 53 private final byte[] register; 54 55 /* 56 * number of bytes for each stream unit, defaults to the blocksize 57 * of the embedded cipher 58 */ 59 private int numBytes; 60 61 // variables for save/restore calls 62 private byte[] registerSave = null; 63 64 CipherFeedback(SymmetricCipher embeddedCipher, int numBytes) { 65 super(embeddedCipher); 66 if (numBytes > blockSize) { 67 numBytes = blockSize; 68 } 69 this.numBytes = numBytes; 70 k = new byte[blockSize]; 71 register = new byte[blockSize]; 72 } 73 74 /** 75 * Gets the name of this feedback mode. 76 * 77 * @return the string <code>CFB</code> 78 */ 79 String getFeedback() { 80 return "CFB"; 81 } 82 83 /** 84 * Initializes the cipher in the specified mode with the given key 85 * and iv. 86 * 87 * @param decrypting flag indicating encryption or decryption 88 * @param algorithm the algorithm name 89 * @param key the key 90 * @param iv the iv 91 * 92 * @exception InvalidKeyException if the given key is inappropriate for 93 * initializing this cipher 94 */ 95 void init(boolean decrypting, String algorithm, byte[] key, byte[] iv) 96 throws InvalidKeyException { 97 if ((key == null) || (iv == null) || (iv.length != blockSize)) { 98 throw new InvalidKeyException("Internal error"); 99 } 100 this.iv = iv; 101 reset(); 102 // always encrypt mode for embedded cipher 103 embeddedCipher.init(false, algorithm, key); 104 } 105 106 /** 107 * Resets the iv to its original value. 108 * This is used when doFinal is called in the Cipher class, so that the 109 * cipher can be reused (with its original iv). 110 */ 111 void reset() { 112 System.arraycopy(iv, 0, register, 0, blockSize); 113 } 114 115 /** 116 * Save the current content of this cipher. 117 */ 118 void save() { 119 if (registerSave == null) { 120 registerSave = new byte[blockSize]; 121 } 122 System.arraycopy(register, 0, registerSave, 0, blockSize); 123 } 124 125 /** 126 * Restores the content of this cipher to the previous saved one. 127 */ 128 void restore() { 129 System.arraycopy(registerSave, 0, register, 0, blockSize); 130 } 131 132 /** 133 * Performs encryption operation. 134 * 135 * <p>The input plain text <code>plain</code>, starting at 136 * <code>plainOffset</code> and ending at 137 * <code>(plainOffset + plainLen - 1)</code>, is encrypted. 138 * The result is stored in <code>cipher</code>, starting at 139 * <code>cipherOffset</code>. 140 * 141 * @param plain the buffer with the input data to be encrypted 142 * @param plainOffset the offset in <code>plain</code> 143 * @param plainLen the length of the input data 144 * @param cipher the buffer for the result 145 * @param cipherOffset the offset in <code>cipher</code> 146 * @exception ProviderException if <code>plainLen</code> is not 147 * a multiple of the <code>numBytes</code> 148 * @return the length of the encrypted data 149 */ 150 int encrypt(byte[] plain, int plainOffset, int plainLen, 151 byte[] cipher, int cipherOffset) { 152 if ((plainLen % numBytes) != 0) { 153 throw new ProviderException("Internal error in input buffering"); 154 } 155 156 int nShift = blockSize - numBytes; 157 int loopCount = plainLen / numBytes; 158 159 for (; loopCount > 0 ; 160 plainOffset += numBytes, cipherOffset += numBytes, 161 loopCount--) { 162 embeddedCipher.encryptBlock(register, 0, k, 0); 163 if (nShift != 0) { 164 System.arraycopy(register, numBytes, register, 0, nShift); 165 } 166 for (int i = 0; i < numBytes; i++) { 167 register[nShift + i] = cipher[i + cipherOffset] = 168 (byte)(k[i] ^ plain[i + plainOffset]); 169 } 170 } 171 return plainLen; 172 } 173 174 /** 175 * Performs the last encryption operation. 176 * 177 * <p>The input plain text <code>plain</code>, starting at 178 * <code>plainOffset</code> and ending at 179 * <code>(plainOffset + plainLen - 1)</code>, is encrypted. 180 * The result is stored in <code>cipher</code>, starting at 181 * <code>cipherOffset</code>. 182 * 183 * @param plain the buffer with the input data to be encrypted 184 * @param plainOffset the offset in <code>plain</code> 185 * @param plainLen the length of the input data 186 * @param cipher the buffer for the result 187 * @param cipherOffset the offset in <code>cipher</code> 188 * @return the number of bytes placed into <code>cipher</code> 189 */ 190 int encryptFinal(byte[] plain, int plainOffset, int plainLen, 191 byte[] cipher, int cipherOffset) { 192 193 int oddBytes = plainLen % numBytes; 194 int len = encrypt(plain, plainOffset, (plainLen - oddBytes), 195 cipher, cipherOffset); 196 plainOffset += len; 197 cipherOffset += len; 198 if (oddBytes != 0) { 199 embeddedCipher.encryptBlock(register, 0, k, 0); 200 for (int i = 0; i < oddBytes; i++) { 201 cipher[i + cipherOffset] = 202 (byte)(k[i] ^ plain[i + plainOffset]); 203 } 204 } 205 return plainLen; 206 } 207 208 /** 209 * Performs decryption operation. 210 * 211 * <p>The input cipher text <code>cipher</code>, starting at 212 * <code>cipherOffset</code> and ending at 213 * <code>(cipherOffset + cipherLen - 1)</code>, is decrypted. 214 * The result is stored in <code>plain</code>, starting at 215 * <code>plainOffset</code>. 216 * 217 * @param cipher the buffer with the input data to be decrypted 218 * @param cipherOffset the offset in <code>cipherOffset</code> 219 * @param cipherLen the length of the input data 220 * @param plain the buffer for the result 221 * @param plainOffset the offset in <code>plain</code> 222 * @exception ProviderException if <code>cipherLen</code> is not 223 * a multiple of the <code>numBytes</code> 224 * @return the length of the decrypted data 225 */ 226 int decrypt(byte[] cipher, int cipherOffset, int cipherLen, 227 byte[] plain, int plainOffset) { 228 if ((cipherLen % numBytes) != 0) { 229 throw new ProviderException("Internal error in input buffering"); 230 } 231 232 int nShift = blockSize - numBytes; 233 int loopCount = cipherLen / numBytes; 234 235 for (; loopCount > 0; 236 plainOffset += numBytes, cipherOffset += numBytes, 237 loopCount--) { 238 embeddedCipher.encryptBlock(register, 0, k, 0); 239 if (nShift != 0) { 240 System.arraycopy(register, numBytes, register, 0, nShift); 241 } 242 for (int i = 0; i < numBytes; i++) { 243 register[i + nShift] = cipher[i + cipherOffset]; 244 plain[i + plainOffset] 245 = (byte)(cipher[i + cipherOffset] ^ k[i]); 246 } 247 } 248 return cipherLen; 249 } 250 251 /** 252 * Performs the last decryption operation. 253 * 254 * <p>The input cipher text <code>cipher</code>, starting at 255 * <code>cipherOffset</code> and ending at 256 * <code>(cipherOffset + cipherLen - 1)</code>, is decrypted. 257 * The result is stored in <code>plain</code>, starting at 258 * <code>plainOffset</code>. 259 * 260 * @param cipher the buffer with the input data to be decrypted 261 * @param cipherOffset the offset in <code>cipherOffset</code> 262 * @param cipherLen the length of the input data 263 * @param plain the buffer for the result 264 * @param plainOffset the offset in <code>plain</code> 265 * @return the length of the decrypted data 266 */ 267 int decryptFinal(byte[] cipher, int cipherOffset, int cipherLen, 268 byte[] plain, int plainOffset) { 269 270 int oddBytes = cipherLen % numBytes; 271 int len = decrypt(cipher, cipherOffset, (cipherLen - oddBytes), 272 plain, plainOffset); 273 cipherOffset += len; 274 plainOffset += len; 275 if (oddBytes != 0) { 276 embeddedCipher.encryptBlock(register, 0, k, 0); 277 for (int i = 0; i < oddBytes; i++) { 278 plain[i + plainOffset] 279 = (byte)(cipher[i + cipherOffset] ^ k[i]); 280 } 281 } 282 return cipherLen; 283 } 284} 285