1 /* 2 * Copyright (c) 2002, 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 26 package com.sun.crypto.provider; 27 28 import java.security.InvalidKeyException; 29 import java.util.Objects; 30 31 import jdk.internal.HotSpotIntrinsicCandidate; 32 33 /** 34 * This class represents ciphers in counter (CTR) mode. 35 * 36 * <p>This mode is implemented independently of a particular cipher. 37 * Ciphers to which this mode should apply (e.g., DES) must be 38 * <i>plugged-in</i> using the constructor. 39 * 40 * <p>NOTE: This class does not deal with buffering or padding. 41 * 42 * @author Andreas Sterbenz 43 * @since 1.4.2 44 */ 45 final class CounterMode extends FeedbackCipher { 46 47 // current counter value 48 private final byte[] counter; 49 50 // encrypted bytes of the previous counter value 51 private final byte[] encryptedCounter; 52 53 // number of bytes in encryptedCounter already used up 54 private int used; 55 56 // variables for save/restore calls 57 private byte[] counterSave = null; 58 private byte[] encryptedCounterSave = null; 59 private int usedSave = 0; 60 61 CounterMode(SymmetricCipher embeddedCipher) { 62 super(embeddedCipher); 63 counter = new byte[blockSize]; 64 encryptedCounter = new byte[blockSize]; 65 } 66 67 /** 68 * Gets the name of the feedback mechanism 69 * 70 * @return the name of the feedback mechanism 71 */ 72 String getFeedback() { 73 return "CTR"; 74 } 75 76 /** 77 * Resets the iv to its original value. 78 * This is used when doFinal is called in the Cipher class, so that the 79 * cipher can be reused (with its original iv). 80 */ 81 void reset() { 82 System.arraycopy(iv, 0, counter, 0, blockSize); 83 used = blockSize; 84 } 85 86 /** 87 * Save the current content of this cipher. 88 */ 89 void save() { 90 if (counterSave == null) { 91 counterSave = new byte[blockSize]; 92 encryptedCounterSave = new byte[blockSize]; 93 } 94 System.arraycopy(counter, 0, counterSave, 0, blockSize); 95 System.arraycopy(encryptedCounter, 0, encryptedCounterSave, 0, 96 blockSize); 97 usedSave = used; 98 } 99 100 /** 101 * Restores the content of this cipher to the previous saved one. 102 */ 103 void restore() { 104 System.arraycopy(counterSave, 0, counter, 0, blockSize); 105 System.arraycopy(encryptedCounterSave, 0, encryptedCounter, 0, 106 blockSize); 107 used = usedSave; 108 } 109 110 /** 111 * Initializes the cipher in the specified mode with the given key 112 * and iv. 113 * 114 * @param decrypting flag indicating encryption or decryption 115 * @param algorithm the algorithm name 116 * @param key the key 117 * @param iv the iv 118 * 119 * @exception InvalidKeyException if the given key is inappropriate for 120 * initializing this cipher 121 */ 122 void init(boolean decrypting, String algorithm, byte[] key, byte[] iv) 123 throws InvalidKeyException { 124 if ((key == null) || (iv == null) || (iv.length != blockSize)) { 125 throw new InvalidKeyException("Internal error"); 126 } 127 this.iv = iv; 128 reset(); 129 // always encrypt mode for embedded cipher 130 embeddedCipher.init(false, algorithm, key); 131 } 132 133 /** 134 * Performs encryption operation. 135 * 136 * <p>The input plain text <code>plain</code>, starting at 137 * <code>plainOffset</code> and ending at 138 * <code>(plainOffset + len - 1)</code>, is encrypted. 139 * The result is stored in <code>cipher</code>, starting at 140 * <code>cipherOffset</code>. 141 * 142 * @param in the buffer with the input data to be encrypted 143 * @param inOff the offset in <code>plain</code> 144 * @param len the length of the input data 145 * @param out the buffer for the result 146 * @param outOff the offset in <code>cipher</code> 147 * @return the length of the encrypted data 148 */ 149 int encrypt(byte[] in, int inOff, int len, byte[] out, int outOff) { 150 return crypt(in, inOff, len, out, outOff); 151 } 152 153 // CTR encrypt and decrypt are identical 154 int decrypt(byte[] in, int inOff, int len, byte[] out, int outOff) { 155 return crypt(in, inOff, len, out, outOff); 156 } 157 158 /** 159 * Increment the counter value. 160 */ 161 private static void increment(byte[] b) { 162 int n = b.length - 1; 163 while ((n >= 0) && (++b[n] == 0)) { 164 n--; 165 } 166 } 167 168 /** 169 * Do the actual encryption/decryption operation. 170 * Essentially we XOR the input plaintext/ciphertext stream with a 171 * keystream generated by encrypting the counter values. Counter values 172 * are encrypted on demand. 173 */ 174 private int crypt(byte[] in, int inOff, int len, byte[] out, int outOff) { 175 176 Objects.checkFromIndexSize(inOff, len, in.length); 177 Objects.checkFromIndexSize(outOff, len, out.length); 178 return implCrypt(in, inOff, len, out, outOff); 179 } 180 181 // Implementation of crpyt() method. Possibly replaced with a compiler intrinsic. 182 @HotSpotIntrinsicCandidate 183 private int implCrypt(byte[] in, int inOff, int len, byte[] out, int outOff) { 184 int result = len; 185 while (len-- > 0) { 186 if (used >= blockSize) { 187 embeddedCipher.encryptBlock(counter, 0, encryptedCounter, 0); 188 increment(counter); 189 used = 0; 190 } 191 out[outOff++] = (byte)(in[inOff++] ^ encryptedCounter[used++]); 192 } 193 return result; 194 } 195 196 }