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 java.security;
27 
28 import java.nio.ByteBuffer;
29 
30 import sun.security.jca.JCAUtil;
31 
32 /**
33  * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
34  * for the {@code MessageDigest} class, which provides the functionality
35  * of a message digest algorithm, such as MD5 or SHA. Message digests are
36  * secure one-way hash functions that take arbitrary-sized data and output a
37  * fixed-length hash value.
38  *
39  * <p> All the abstract methods in this class must be implemented by a
40  * cryptographic service provider who wishes to supply the implementation
41  * of a particular message digest algorithm.
42  *
43  * <p> Implementations are free to implement the Cloneable interface.
44  *
45  * @author Benjamin Renaud
46  * @since 1.2
47  *
48  *
49  * @see MessageDigest
50  */
51 
52 public abstract class MessageDigestSpi {
53 
54     // for re-use in engineUpdate(ByteBuffer input)
55     private byte[] tempArray;
56 
57     /**
58      * Returns the digest length in bytes.
59      *
60      * <p>This concrete method has been added to this previously-defined
61      * abstract class. (For backwards compatibility, it cannot be abstract.)
62      *
63      * <p>The default behavior is to return 0.
64      *
65      * <p>This method may be overridden by a provider to return the digest
66      * length.
67      *
68      * @return the digest length in bytes.
69      *
70      * @since 1.2
71      */
engineGetDigestLength()72     protected int engineGetDigestLength() {
73         return 0;
74     }
75 
76     /**
77      * Updates the digest using the specified byte.
78      *
79      * @param input the byte to use for the update.
80      */
engineUpdate(byte input)81     protected abstract void engineUpdate(byte input);
82 
83     /**
84      * Updates the digest using the specified array of bytes,
85      * starting at the specified offset.
86      *
87      * @param input the array of bytes to use for the update.
88      *
89      * @param offset the offset to start from in the array of bytes.
90      *
91      * @param len the number of bytes to use, starting at
92      * {@code offset}.
93      */
engineUpdate(byte[] input, int offset, int len)94     protected abstract void engineUpdate(byte[] input, int offset, int len);
95 
96     /**
97      * Update the digest using the specified ByteBuffer. The digest is
98      * updated using the {@code input.remaining()} bytes starting
99      * at {@code input.position()}.
100      * Upon return, the buffer's position will be equal to its limit;
101      * its limit will not have changed.
102      *
103      * @param input the ByteBuffer
104      * @since 1.5
105      */
engineUpdate(ByteBuffer input)106     protected void engineUpdate(ByteBuffer input) {
107         if (input.hasRemaining() == false) {
108             return;
109         }
110         if (input.hasArray()) {
111             byte[] b = input.array();
112             int ofs = input.arrayOffset();
113             int pos = input.position();
114             int lim = input.limit();
115             engineUpdate(b, ofs + pos, lim - pos);
116             input.position(lim);
117         } else {
118             int len = input.remaining();
119             int n = JCAUtil.getTempArraySize(len);
120             if ((tempArray == null) || (n > tempArray.length)) {
121                 tempArray = new byte[n];
122             }
123             while (len > 0) {
124                 int chunk = Math.min(len, tempArray.length);
125                 input.get(tempArray, 0, chunk);
126                 engineUpdate(tempArray, 0, chunk);
127                 len -= chunk;
128             }
129         }
130     }
131 
132     /**
133      * Completes the hash computation by performing final
134      * operations such as padding. Once {@code engineDigest} has
135      * been called, the engine should be reset (see
136      * {@link #engineReset() engineReset}).
137      * Resetting is the responsibility of the
138      * engine implementor.
139      *
140      * @return the array of bytes for the resulting hash value.
141      */
engineDigest()142     protected abstract byte[] engineDigest();
143 
144     /**
145      * Completes the hash computation by performing final
146      * operations such as padding. Once {@code engineDigest} has
147      * been called, the engine should be reset (see
148      * {@link #engineReset() engineReset}).
149      * Resetting is the responsibility of the
150      * engine implementor.
151      *
152      * This method should be abstract, but we leave it concrete for
153      * binary compatibility.  Knowledgeable providers should override this
154      * method.
155      *
156      * @param buf the output buffer in which to store the digest
157      *
158      * @param offset offset to start from in the output buffer
159      *
160      * @param len number of bytes within buf allotted for the digest.
161      * Both this default implementation and the SUN provider do not
162      * return partial digests.  The presence of this parameter is solely
163      * for consistency in our API's.  If the value of this parameter is less
164      * than the actual digest length, the method will throw a DigestException.
165      * This parameter is ignored if its value is greater than or equal to
166      * the actual digest length.
167      *
168      * @return the length of the digest stored in the output buffer.
169      *
170      * @exception DigestException if an error occurs.
171      *
172      * @since 1.2
173      */
engineDigest(byte[] buf, int offset, int len)174     protected int engineDigest(byte[] buf, int offset, int len)
175                                                 throws DigestException {
176 
177         byte[] digest = engineDigest();
178         if (len < digest.length)
179                 throw new DigestException("partial digests not returned");
180         if (buf.length - offset < digest.length)
181                 throw new DigestException("insufficient space in the output "
182                                           + "buffer to store the digest");
183         System.arraycopy(digest, 0, buf, offset, digest.length);
184         return digest.length;
185     }
186 
187     /**
188      * Resets the digest for further use.
189      */
engineReset()190     protected abstract void engineReset();
191 
192     /**
193      * Returns a clone if the implementation is cloneable.
194      *
195      * @return a clone if the implementation is cloneable.
196      *
197      * @exception CloneNotSupportedException if this is called on an
198      * implementation that does not support {@code Cloneable}.
199      */
clone()200     public Object clone() throws CloneNotSupportedException {
201         if (this instanceof Cloneable) {
202             return super.clone();
203         } else {
204             throw new CloneNotSupportedException();
205         }
206     }
207 }
208