1 /*
2 * Copyright (c) 1997, 2013, 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
30 /**
31 * This class represents ciphers in cipher block chaining (CBC) mode.
32 *
33 * <p>This mode is implemented independently of a particular cipher.
34 * Ciphers to which this mode should apply (e.g., DES) must be
35 * <i>plugged-in</i> using the constructor.
36 *
37 * <p>NOTE: This class does not deal with buffering or padding.
38 *
39 * @author Gigi Ankeny
40 */
41
42 class CipherBlockChaining extends FeedbackCipher {
43
44 /*
45 * random bytes that are initialized with iv
46 */
47 protected byte[] r;
48
49 /*
50 * output buffer
51 */
52 private byte[] k;
53
54 // variables for save/restore calls
55 private byte[] rSave = null;
56
57 CipherBlockChaining(SymmetricCipher embeddedCipher) {
58 super(embeddedCipher);
59 k = new byte[blockSize];
60 r = new byte[blockSize];
61 }
62
63 /**
64 * Gets the name of this feedback mode.
65 *
66 * @return the string <code>CBC</code>
67 */
68 String getFeedback() {
69 return "CBC";
70 }
71
72 /**
73 * Initializes the cipher in the specified mode with the given key
74 * and iv.
75 *
76 * @param decrypting flag indicating encryption or decryption
77 * @param algorithm the algorithm name
78 * @param key the key
79 * @param iv the iv
80 *
81 * @exception InvalidKeyException if the given key is inappropriate for
82 * initializing this cipher
83 */
84 void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
85 throws InvalidKeyException {
86 if ((key == null) || (iv == null) || (iv.length != blockSize)) {
87 throw new InvalidKeyException("Internal error");
88 }
89 this.iv = iv;
90 reset();
91 embeddedCipher.init(decrypting, algorithm, key);
92 }
93
94 /**
95 * Resets the iv to its original value.
96 * This is used when doFinal is called in the Cipher class, so that the
97 * cipher can be reused (with its original iv).
98 */
99 void reset() {
100 System.arraycopy(iv, 0, r, 0, blockSize);
101 }
102
103 /**
104 * Save the current content of this cipher.
105 */
106 void save() {
107 if (rSave == null) {
108 rSave = new byte[blockSize];
109 }
110 System.arraycopy(r, 0, rSave, 0, blockSize);
111 }
112
113 /**
114 * Restores the content of this cipher to the previous saved one.
115 */
116 void restore() {
117 System.arraycopy(rSave, 0, r, 0, blockSize);
118 }
119
120 /**
121 * Performs encryption operation.
122 *
123 * <p>The input plain text <code>plain</code>, starting at
124 * <code>plainOffset</code> and ending at
125 * <code>(plainOffset + len - 1)</code>, is encrypted.
126 * The result is stored in <code>cipher</code>, starting at
127 * <code>cipherOffset</code>.
128 *
129 * <p>It is the application's responsibility to make sure that
130 * <code>plainLen</code> is a multiple of the embedded cipher's block size,
131 * as any excess bytes are ignored.
132 *
133 * @param plain the buffer with the input data to be encrypted
134 * @param plainOffset the offset in <code>plain</code>
135 * @param plainLen the length of the input data
136 * @param cipher the buffer for the result
137 * @param cipherOffset the offset in <code>cipher</code>
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 int i;
144 int endIndex = plainOffset + plainLen;
145
146 for (; plainOffset < endIndex;
147 plainOffset+=blockSize, cipherOffset += blockSize) {
148 for (i=0; i<blockSize; i++) {
149 k[i] = (byte)(plain[i+plainOffset] ^ r[i]);
150 }
151 embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
152 System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
153 }
154 return plainLen;
155 }
156
157 /**
158 * Performs decryption operation.
159 *
160 * <p>The input cipher text <code>cipher</code>, starting at
161 * <code>cipherOffset</code> and ending at
162 * <code>(cipherOffset + len - 1)</code>, is decrypted.
163 * The result is stored in <code>plain</code>, starting at
164 * <code>plainOffset</code>.
165 *
166 * <p>It is the application's responsibility to make sure that
167 * <code>cipherLen</code> is a multiple of the embedded cipher's block
168 * size, as any excess bytes are ignored.
169 *
170 * <p>It is also the application's responsibility to make sure that
171 * <code>init</code> has been called before this method is called.
172 * (This check is omitted here, to avoid double checking.)
173 *
174 * @param cipher the buffer with the input data to be decrypted
175 * @param cipherOffset the offset in <code>cipherOffset</code>
176 * @param cipherLen the length of the input data
177 * @param plain the buffer for the result
178 * @param plainOffset the offset in <code>plain</code>
179 * @return the length of the decrypted data
180 *
181 * @exception IllegalBlockSizeException if input data whose length does
182 * not correspond to the embedded cipher's block size is passed to the
183 * embedded cipher
184 */
185 int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
186 byte[] plain, int plainOffset)
187 {
188 int i;
189 byte[] cipherOrig=null;
190 int endIndex = cipherOffset + cipherLen;
191
192 if (cipher==plain && (cipherOffset >= plainOffset)
193 && ((cipherOffset - plainOffset) < blockSize)) {
194 // Save the original ciphertext blocks, so they can be
195 // stored in the feedback register "r".
196 // This is necessary because in this constellation, a
197 // ciphertext block (or parts of it) will be overridden by
198 // the plaintext result.
199 cipherOrig = cipher.clone();
200 }
201 for (; cipherOffset < endIndex;
202 cipherOffset += blockSize, plainOffset += blockSize) {
203 embeddedCipher.decryptBlock(cipher, cipherOffset, k, 0);
204 for (i = 0; i < blockSize; i++) {
205 plain[i+plainOffset] = (byte)(k[i] ^ r[i]);
206 }
207 if (cipherOrig==null) {
208 System.arraycopy(cipher, cipherOffset, r, 0, blockSize);
209 } else {
210 System.arraycopy(cipherOrig, cipherOffset, r, 0, blockSize);
211 }
212 }
213 return cipherLen;
214 }
215 }