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
26 package com.sun.crypto.provider;
27
28 import java.security.InvalidKeyException;
29 import java.security.ProviderException;
30
31
32 /**
33 * This class represents ciphers in cipher block chaining (CBC) 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
44 class CipherBlockChaining extends FeedbackCipher {
45
46 /*
47 * random bytes that are initialized with iv
48 */
49 protected byte[] r;
50
51 /*
52 * output buffer
53 */
54 private byte[] k;
55
56 // variables for save/restore calls
57 private byte[] rSave = null;
58
59 CipherBlockChaining(SymmetricCipher embeddedCipher) {
60 super(embeddedCipher);
61 k = new byte[blockSize];
62 r = new byte[blockSize];
63 }
64
65 /**
66 * Gets the name of this feedback mode.
67 *
68 * @return the string <code>CBC</code>
69 */
70 String getFeedback() {
71 return "CBC";
72 }
73
74 /**
75 * Initializes the cipher in the specified mode with the given key
76 * and iv.
77 *
78 * @param decrypting flag indicating encryption or decryption
79 * @param algorithm the algorithm name
80 * @param key the key
81 * @param iv the iv
82 *
83 * @exception InvalidKeyException if the given key is inappropriate for
84 * initializing this cipher
85 */
86 void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
87 throws InvalidKeyException {
88 if ((key == null) || (iv == null) || (iv.length != blockSize)) {
89 throw new InvalidKeyException("Internal error");
90 }
91 this.iv = iv;
92 reset();
93 embeddedCipher.init(decrypting, algorithm, key);
94 }
95
96 /**
97 * Resets the iv to its original value.
98 * This is used when doFinal is called in the Cipher class, so that the
99 * cipher can be reused (with its original iv).
100 */
101 void reset() {
102 System.arraycopy(iv, 0, r, 0, blockSize);
103 }
104
105 /**
106 * Save the current content of this cipher.
107 */
108 void save() {
109 if (rSave == null) {
110 rSave = new byte[blockSize];
111 }
112 System.arraycopy(r, 0, rSave, 0, blockSize);
113 }
114
115 /**
116 * Restores the content of this cipher to the previous saved one.
117 */
118 void restore() {
119 System.arraycopy(rSave, 0, r, 0, blockSize);
120 }
121
122 /**
123 * Performs encryption operation.
124 *
125 * <p>The input plain text <code>plain</code>, starting at
126 * <code>plainOffset</code> and ending at
127 * <code>(plainOffset + plainLen - 1)</code>, is encrypted.
128 * The result is stored in <code>cipher</code>, starting at
129 * <code>cipherOffset</code>.
130 *
131 * @param plain the buffer with the input data to be encrypted
132 * @param plainOffset the offset in <code>plain</code>
133 * @param plainLen the length of the input data
134 * @param cipher the buffer for the result
135 * @param cipherOffset the offset in <code>cipher</code>
136 * @exception ProviderException if <code>len</code> is not
137 * a multiple of the block size
138 * @return the length of the encrypted data
139 */
140 int encrypt(byte[] plain, int plainOffset, int plainLen,
141 byte[] cipher, int cipherOffset)
142 {
143 if ((plainLen % blockSize) != 0) {
144 throw new ProviderException("Internal error in input buffering");
145 }
146 int endIndex = plainOffset + plainLen;
147
148 for (; plainOffset < endIndex;
149 plainOffset+=blockSize, cipherOffset += blockSize) {
150 for (int i = 0; i < blockSize; i++) {
151 k[i] = (byte)(plain[i + plainOffset] ^ r[i]);
152 }
153 embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
154 System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
155 }
156 return plainLen;
157 }
158
159 /**
160 * Performs decryption operation.
161 *
162 * <p>The input cipher text <code>cipher</code>, starting at
163 * <code>cipherOffset</code> and ending at
164 * <code>(cipherOffset + cipherLen - 1)</code>, is decrypted.
165 * The result is stored in <code>plain</code>, starting at
166 * <code>plainOffset</code>.
167 *
168 * <p>It is also the application's responsibility to make sure that
169 * <code>init</code> has been called before this method is called.
170 * (This check is omitted here, to avoid double checking.)
171 *
172 * @param cipher the buffer with the input data to be decrypted
173 * @param cipherOffset the offset in <code>cipherOffset</code>
174 * @param cipherLen the length of the input data
175 * @param plain the buffer for the result
176 * @param plainOffset the offset in <code>plain</code>
177 * @exception ProviderException if <code>len</code> is not
178 * a multiple of the block size
179 * @return the length of the decrypted data
180 */
181 int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
182 byte[] plain, int plainOffset)
183 {
184 if ((cipherLen % blockSize) != 0) {
185 throw new ProviderException("Internal error in input buffering");
186 }
187 int endIndex = cipherOffset + cipherLen;
188
189 for (; cipherOffset < endIndex;
190 cipherOffset += blockSize, plainOffset += blockSize) {
191 embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0);
192 for (int i = 0; i < blockSize; i++) {
193 plain[i + plainOffset] = (byte)(k[i] ^ r[i]);
194 }
195 System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
196 }
197 return cipherLen;
198 }
199 }