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 cryptBlockCheck(in, inOff, len);
177 cryptBlockCheck(out, outOff, len);
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 // Used to perform all checks required by the Java semantics
197 // (i.e., null checks and bounds checks) on the input parameters to crypt().
198 // Normally, the Java Runtime performs these checks, however, as crypt() is
199 // possibly replaced with compiler intrinsic, the JDK performs the
200 // required checks instead.
201 // Does not check accesses to class-internal (private) arrays.
202 private static void cryptBlockCheck(byte[] array, int offset, int len) {
203 Objects.requireNonNull(array);
204
205 if (offset < 0 || len < 0 || offset >= array.length) {
206 throw new ArrayIndexOutOfBoundsException(offset);
207 }
208
209 int largestIndex = offset + len - 1;
210 if (largestIndex < 0 || largestIndex >= array.length) {
211 throw new ArrayIndexOutOfBoundsException(largestIndex);
212 }
213 }
214 }