1 /*
2 * Copyright (c) 1997, 2016, 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.math.BigInteger;
29 import java.security.*;
30 import java.security.spec.*;
31 import javax.crypto.spec.DHParameterSpec;
32 import javax.crypto.spec.DHGenParameterSpec;
33
34 /*
35 * This class generates parameters for the Diffie-Hellman algorithm.
36 * The parameters are a prime, a base, and optionally the length in bits of
37 * the private value.
38 *
39 * <p>The Diffie-Hellman parameter generation accepts the size in bits of the
40 * prime modulus and the size in bits of the random exponent as input.
41 * The size of the prime modulus defaults to 2048 bits.
42 *
43 * @author Jan Luehe
44 *
45 *
46 * @see java.security.AlgorithmParameters
47 * @see java.security.spec.AlgorithmParameterSpec
48 * @see DHParameters
49 */
50 public final class DHParameterGenerator extends AlgorithmParameterGeneratorSpi {
51
52 // The size in bits of the prime modulus
53 private int primeSize = 2048;
54
55 // The size in bits of the random exponent (private value)
56 private int exponentSize = 0;
57
58 // The source of randomness
59 private SecureRandom random = null;
60
61 private static void checkKeySize(int keysize)
62 throws InvalidParameterException {
63
64 boolean supported = ((keysize == 2048) || (keysize == 3072) ||
65 ((keysize >= 512) && (keysize <= 1024) && (keysize % 64 == 0)));
66
67 if (!supported) {
68 throw new InvalidParameterException
69 ("Keysize must be multiple of 64 and range "
70 + "from 512 to 1024 (inclusive), or 2048, 3072");
71 }
72 }
73
74 /**
75 * Initializes this parameter generator for a certain keysize
76 * and source of randomness.
77 * The keysize is specified as the size in bits of the prime modulus.
78 *
79 * @param keysize the keysize (size of prime modulus) in bits
80 * @param random the source of randomness
81 */
82 @Override
83 protected void engineInit(int keysize, SecureRandom random) {
84 checkKeySize(keysize);
85 this.primeSize = keysize;
86 this.random = random;
87 }
88
89 /**
90 * Initializes this parameter generator with a set of parameter
91 * generation values, which specify the size of the prime modulus and
92 * the size of the random exponent, both in bits.
93 *
94 * @param genParamSpec the set of parameter generation values
95 * @param random the source of randomness
96 *
97 * @exception InvalidAlgorithmParameterException if the given parameter
98 * generation values are inappropriate for this parameter generator
99 */
100 @Override
101 protected void engineInit(AlgorithmParameterSpec genParamSpec,
102 SecureRandom random) throws InvalidAlgorithmParameterException {
103
104 if (!(genParamSpec instanceof DHGenParameterSpec)) {
105 throw new InvalidAlgorithmParameterException
106 ("Inappropriate parameter type");
107 }
108
109 DHGenParameterSpec dhParamSpec = (DHGenParameterSpec)genParamSpec;
110 primeSize = dhParamSpec.getPrimeSize();
111 exponentSize = dhParamSpec.getExponentSize();
112 if ((exponentSize <= 0) || (exponentSize >= primeSize)) {
113 throw new InvalidAlgorithmParameterException(
114 "Exponent size must be positive and less than modulus size");
115 }
116 try {
117 checkKeySize(primeSize);
118 } catch (InvalidParameterException ipe) {
119 throw new InvalidAlgorithmParameterException(ipe.getMessage());
120 }
121
122 this.random = random;
123 }
124
125 /**
126 * Generates the parameters.
127 *
128 * @return the new AlgorithmParameters object
129 */
130 @Override
131 protected AlgorithmParameters engineGenerateParameters() {
132
133 if (random == null) {
134 random = SunJCE.getRandom();
135 }
136
137 BigInteger paramP = null;
138 BigInteger paramG = null;
139 try {
140 AlgorithmParameterGenerator dsaParamGen =
141 AlgorithmParameterGenerator.getInstance("DSA");
142 dsaParamGen.init(primeSize, random);
143 AlgorithmParameters dsaParams = dsaParamGen.generateParameters();
144 DSAParameterSpec dsaParamSpec =
145 dsaParams.getParameterSpec(DSAParameterSpec.class);
146
147 DHParameterSpec dhParamSpec;
148 if (this.exponentSize > 0) {
149 dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
150 dsaParamSpec.getG(),
151 this.exponentSize);
152 } else {
153 dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
154 dsaParamSpec.getG());
155 }
156 AlgorithmParameters algParams =
157 AlgorithmParameters.getInstance("DH", SunJCE.getInstance());
158 algParams.init(dhParamSpec);
159
160 return algParams;
161 } catch (Exception ex) {
162 throw new ProviderException("Unexpected exception: " + ex);
163 }
164 }
165 }