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 */
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 */
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 */
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 */
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 */
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 */
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 */
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 */
200 public Object clone() throws CloneNotSupportedException {
201 if (this instanceof Cloneable) {
202 return super.clone();
203 } else {
204 throw new CloneNotSupportedException();
205 }
206 }
207 }