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
26package com.sun.crypto.provider;
27
28import java.math.BigInteger;
29import java.security.*;
30import java.security.spec.*;
31import javax.crypto.spec.DHParameterSpec;
32import 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 */
50public 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 & 0x3F) == 0)));
66
67        if (!supported) {
68            throw new InvalidParameterException(
69                    "DH key size must be multiple of 64 and range " +
70                    "from 512 to 1024 (inclusive), or 2048, 3072. " +
71                    "The specific key size " + keysize + " is not supported");
72        }
73    }
74
75    /**
76     * Initializes this parameter generator for a certain keysize
77     * and source of randomness.
78     * The keysize is specified as the size in bits of the prime modulus.
79     *
80     * @param keysize the keysize (size of prime modulus) in bits
81     * @param random the source of randomness
82     */
83    @Override
84    protected void engineInit(int keysize, SecureRandom random) {
85        checkKeySize(keysize);
86        this.primeSize = keysize;
87        this.random = random;
88    }
89
90    /**
91     * Initializes this parameter generator with a set of parameter
92     * generation values, which specify the size of the prime modulus and
93     * the size of the random exponent, both in bits.
94     *
95     * @param genParamSpec the set of parameter generation values
96     * @param random the source of randomness
97     *
98     * @exception InvalidAlgorithmParameterException if the given parameter
99     * generation values are inappropriate for this parameter generator
100     */
101    @Override
102    protected void engineInit(AlgorithmParameterSpec genParamSpec,
103            SecureRandom random) throws InvalidAlgorithmParameterException {
104
105        if (!(genParamSpec instanceof DHGenParameterSpec)) {
106            throw new InvalidAlgorithmParameterException
107                ("Inappropriate parameter type");
108        }
109
110        DHGenParameterSpec dhParamSpec = (DHGenParameterSpec)genParamSpec;
111        primeSize = dhParamSpec.getPrimeSize();
112        exponentSize = dhParamSpec.getExponentSize();
113        if ((exponentSize <= 0) || (exponentSize >= primeSize)) {
114            throw new InvalidAlgorithmParameterException(
115                    "Exponent size (" + exponentSize +
116                    ") must be positive and less than modulus size (" +
117                    primeSize + ")");
118        }
119        try {
120            checkKeySize(primeSize);
121        } catch (InvalidParameterException ipe) {
122            throw new InvalidAlgorithmParameterException(ipe.getMessage());
123        }
124
125        this.random = random;
126    }
127
128    /**
129     * Generates the parameters.
130     *
131     * @return the new AlgorithmParameters object
132     */
133    @Override
134    protected AlgorithmParameters engineGenerateParameters() {
135
136        if (random == null) {
137            random = SunJCE.getRandom();
138        }
139
140        BigInteger paramP = null;
141        BigInteger paramG = null;
142        try {
143            AlgorithmParameterGenerator dsaParamGen =
144                    AlgorithmParameterGenerator.getInstance("DSA");
145            dsaParamGen.init(primeSize, random);
146            AlgorithmParameters dsaParams = dsaParamGen.generateParameters();
147            DSAParameterSpec dsaParamSpec =
148                    dsaParams.getParameterSpec(DSAParameterSpec.class);
149
150            DHParameterSpec dhParamSpec;
151            if (this.exponentSize > 0) {
152                dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
153                                                  dsaParamSpec.getG(),
154                                                  this.exponentSize);
155            } else {
156                dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
157                                                  dsaParamSpec.getG());
158            }
159            AlgorithmParameters algParams =
160                    AlgorithmParameters.getInstance("DH", SunJCE.getInstance());
161            algParams.init(dhParamSpec);
162
163            return algParams;
164        } catch (Exception ex) {
165            throw new ProviderException("Unexpected exception", ex);
166        }
167    }
168}
169