1 /* 2 * Copyright (c) 1997, 2018, 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 import sun.security.util.ArrayUtil; 31 32 /** 33 * This class represents ciphers in output-feedback (OFB) 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 final class OutputFeedback extends FeedbackCipher { 44 45 /* 46 * output buffer 47 */ 48 private byte[] k = null; 49 50 /* 51 * register buffer 52 */ 53 private byte[] register = null; 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 OutputFeedback(SymmetricCipher embeddedCipher, int numBytes)64 OutputFeedback(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>OFB</code> 78 */ getFeedback()79 String getFeedback() { 80 return "OFB"; 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 */ init(boolean decrypting, String algorithm, byte[] key, byte[] iv)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 */ reset()111 void reset() { 112 System.arraycopy(iv, 0, register, 0, blockSize); 113 } 114 115 /** 116 * Save the current content of this cipher. 117 */ save()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 */ restore()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 */ encrypt(byte[] plain, int plainOffset, int plainLen, byte[] cipher, int cipherOffset)150 int encrypt(byte[] plain, int plainOffset, int plainLen, 151 byte[] cipher, int cipherOffset) { 152 ArrayUtil.blockSizeCheck(plainLen, numBytes); 153 ArrayUtil.nullAndBoundsCheck(plain, plainOffset, plainLen); 154 ArrayUtil.nullAndBoundsCheck(cipher, cipherOffset, plainLen); 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 for (int i = 0; i < numBytes; i++) { 164 cipher[i + cipherOffset] = 165 (byte)(k[i] ^ plain[i + plainOffset]); 166 } 167 if (nShift != 0) { 168 System.arraycopy(register, numBytes, register, 0, nShift); 169 } 170 System.arraycopy(k, 0, register, nShift, numBytes); 171 } 172 return plainLen; 173 } 174 175 /** 176 * Performs last encryption operation. 177 * 178 * <p>The input plain text <code>plain</code>, starting at 179 * <code>plainOffset</code> and ending at 180 * <code>(plainOffset + plainLen - 1)</code>, is encrypted. 181 * The result is stored in <code>cipher</code>, starting at 182 * <code>cipherOffset</code>. 183 * 184 * @param plain the buffer with the input data to be encrypted 185 * @param plainOffset the offset in <code>plain</code> 186 * @param plainLen the length of the input data 187 * @param cipher the buffer for the result 188 * @param cipherOffset the offset in <code>cipher</code> 189 * @return the length of the encrypted data 190 */ encryptFinal(byte[] plain, int plainOffset, int plainLen, byte[] cipher, int cipherOffset)191 int encryptFinal(byte[] plain, int plainOffset, int plainLen, 192 byte[] cipher, int cipherOffset) { 193 ArrayUtil.nullAndBoundsCheck(plain, plainOffset, plainLen); 194 ArrayUtil.nullAndBoundsCheck(cipher, cipherOffset, plainLen); 195 196 int oddBytes = plainLen % numBytes; 197 int len = encrypt(plain, plainOffset, (plainLen - oddBytes), 198 cipher, cipherOffset); 199 plainOffset += len; 200 cipherOffset += len; 201 202 if (oddBytes != 0) { 203 embeddedCipher.encryptBlock(register, 0, k, 0); 204 for (int i = 0; i < oddBytes; i++) { 205 cipher[i + cipherOffset] = 206 (byte)(k[i] ^ plain[ i + plainOffset]); 207 } 208 } 209 return plainLen; 210 } 211 212 // OFB encrypt and decrypt are identical decrypt(byte[] cipher, int cipherOffset, int cipherLen, byte[] plain, int plainOffset)213 int decrypt(byte[] cipher, int cipherOffset, int cipherLen, 214 byte[] plain, int plainOffset) { 215 return encrypt(cipher, cipherOffset, cipherLen, plain, plainOffset); 216 } 217 218 // OFB encrypt and decrypt are identical decryptFinal(byte[] cipher, int cipherOffset, int cipherLen, byte[] plain, int plainOffset)219 int decryptFinal(byte[] cipher, int cipherOffset, int cipherLen, 220 byte[] plain, int plainOffset) { 221 // OFB encrypt and decrypt are identical 222 return encryptFinal(cipher, cipherOffset, cipherLen, plain, plainOffset); 223 } 224 } 225