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
26package com.sun.crypto.provider;
27
28import java.security.InvalidKeyException;
29import java.security.ProviderException;
30
31
32/**
33 * This class represents ciphers in Plaintext Cipher Block Chaining (PCBC)
34 * 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 Gigi Ankeny
43 */
44
45final class PCBC extends FeedbackCipher {
46
47    /*
48     * output buffer
49     */
50    private final byte[] k;
51
52    // variables for save/restore calls
53    private byte[] kSave = null;
54
55    PCBC(SymmetricCipher embeddedCipher) {
56        super(embeddedCipher);
57        k = new byte[blockSize];
58    }
59
60    /**
61     * Gets the name of this feedback mode.
62     *
63     * @return the string <code>PCBC</code>
64     */
65    String getFeedback() {
66        return "PCBC";
67    }
68
69    /**
70     * Initializes the cipher in the specified mode with the given key
71     * and iv.
72     *
73     * @param decrypting flag indicating encryption or decryption
74     * @param algorithm the algorithm name
75     * @param key the key
76     * @param iv the iv
77     *
78     * @exception InvalidKeyException if the given key is inappropriate for
79     * initializing this cipher
80     */
81    void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
82            throws InvalidKeyException {
83        if ((key == null) || (iv == null) || (iv.length != blockSize)) {
84            throw new InvalidKeyException("Internal error");
85        }
86        this.iv = iv;
87        reset();
88        embeddedCipher.init(decrypting, algorithm, key);
89    }
90
91    /**
92     * Resets the iv to its original value.
93     * This is used when doFinal is called in the Cipher class, so that the
94     * cipher can be reused (with its original iv).
95     */
96    void reset() {
97        System.arraycopy(iv, 0, k, 0, blockSize);
98    }
99
100    /**
101     * Save the current content of this cipher.
102     */
103    void save() {
104        if (kSave == null) {
105            kSave = new byte[blockSize];
106        }
107        System.arraycopy(k, 0, kSave, 0, blockSize);
108
109    }
110
111    /**
112     * Restores the content of this cipher to the previous saved one.
113     */
114    void restore() {
115        System.arraycopy(kSave, 0, k, 0, blockSize);
116    }
117
118    /**
119     * Performs encryption operation.
120     *
121     * <p>The input plain text <code>plain</code>, starting at
122     * <code>plainOffset</code> and ending at
123     * <code>(plainOffset + plainLen - 1)</code>, is encrypted.
124     * The result is stored in <code>cipher</code>, starting at
125     * <code>cipherOffset</code>.
126     *
127     * @param plain the buffer with the input data to be encrypted
128     * @param plainOffset the offset in <code>plain</code>
129     * @param plainLen the length of the input data
130     * @param cipher the buffer for the result
131     * @param cipherOffset the offset in <code>cipher</code>
132     * @exception ProviderException if <code>plainLen</code> is not
133     * a multiple of the block size
134     * @return the length of the encrypted data
135     */
136    int encrypt(byte[] plain, int plainOffset, int plainLen,
137                byte[] cipher, int cipherOffset)
138    {
139        if ((plainLen % blockSize) != 0) {
140            throw new ProviderException("Internal error in input buffering");
141        }
142        int i;
143        int endIndex = plainOffset + plainLen;
144
145        for (; plainOffset < endIndex;
146             plainOffset += blockSize, cipherOffset += blockSize) {
147            for (i = 0; i < blockSize; i++) {
148                k[i] ^= plain[i + plainOffset];
149            }
150            embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
151            for (i = 0; i < blockSize; i++) {
152                k[i] = (byte)(plain[i + plainOffset] ^ cipher[i + cipherOffset]);
153            }
154        }
155        return plainLen;
156    }
157
158    /**
159     * Performs decryption operation.
160     *
161     * <p>The input cipher text <code>cipher</code>, starting at
162     * <code>cipherOffset</code> and ending at
163     * <code>(cipherOffset + cipherLen - 1)</code>, is decrypted.
164     * The result is stored in <code>plain</code>, starting at
165     * <code>plainOffset</code>.
166     *
167     * @param cipher the buffer with the input data to be decrypted
168     * @param cipherOffset the offset in <code>cipherOffset</code>
169     * @param cipherLen the length of the input data
170     * @param plain the buffer for the result
171     * @param plainOffset the offset in <code>plain</code>
172     * @exception ProviderException if <code>cipherLen</code> is not
173     * a multiple of the block size
174     * @return the length of the decrypted data
175     */
176    int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
177                byte[] plain, int plainOffset)
178    {
179        if ((cipherLen % blockSize) != 0) {
180             throw new ProviderException("Internal error in input buffering");
181        }
182        int i;
183        int endIndex = cipherOffset + cipherLen;
184
185        for (; cipherOffset < endIndex;
186             plainOffset += blockSize, cipherOffset += blockSize) {
187            embeddedCipher.decryptBlock(cipher, cipherOffset,
188                                   plain, plainOffset);
189            for (i = 0; i < blockSize; i++) {
190                plain[i + plainOffset] ^= k[i];
191            }
192            for (i = 0; i < blockSize; i++) {
193                k[i] = (byte)(plain[i + plainOffset] ^ cipher[i + cipherOffset]);
194            }
195        }
196        return cipherLen;
197    }
198}
199