AlgIdDSA.java revision 12318:bee34b1dcbf1 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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).
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24 */
25
26package sun.security.x509;
27
28import java.io.IOException;
29import java.math.BigInteger;
30import java.security.*;
31import java.security.interfaces.DSAParams;
32
33import sun.security.util.*;
34
35
36/**
37 * This class identifies DSS/DSA Algorithm variants, which are distinguished
38 * by using different algorithm parameters <em>P, Q, G</em>.  It uses the
39 * NIST/IETF standard DER encoding.  These are used to implement the Digital
40 * Signature Standard (DSS), FIPS 186.
41 *
42 * <P><em><b>NOTE:</b></em>  DSS/DSA Algorithm IDs may be created without these
43 * parameters.  Use of DSS/DSA in modes where parameters are
44 * either implicit (e.g. a default applicable to a site or a larger scope),
45 * or are derived from some Certificate Authority's DSS certificate, is
46 * not supported directly.  The application is responsible for creating a key
47 * containing the required parameters prior to using the key in cryptographic
48 * operations.  The follwoing is an example of how this may be done assuming
49 * that we have a certificate called <code>currentCert</code> which doesn't
50 * contain DSS/DSA parameters and we need to derive DSS/DSA parameters
51 * from a CA's certificate called <code>caCert</code>.
52 *
53 * <pre>{@code
54 * // key containing parameters to use
55 * DSAPublicKey cAKey = (DSAPublicKey)(caCert.getPublicKey());
56 * // key without parameters
57 * DSAPublicKey nullParamsKey = (DSAPublicKey)(currentCert.getPublicKey());
58 *
59 * DSAParams cAKeyParams = cAKey.getParams();
60 * KeyFactory kf = KeyFactory.getInstance("DSA");
61 * DSAPublicKeySpec ks = new DSAPublicKeySpec(nullParamsKey.getY(),
62 *                                            cAKeyParams.getP(),
63 *                                            cAKeyParams.getQ(),
64 *                                            cAKeyParams.getG());
65 * DSAPublicKey usableKey = kf.generatePublic(ks);
66 * }</pre>
67 *
68 * @see java.security.interfaces.DSAParams
69 * @see java.security.interfaces.DSAPublicKey
70 * @see java.security.KeyFactory
71 * @see java.security.spec.DSAPublicKeySpec
72 *
73 * @author David Brownell
74 */
75public final
76class AlgIdDSA extends AlgorithmId implements DSAParams
77{
78
79    private static final long serialVersionUID = 3437177836797504046L;
80
81    /*
82     * The three unsigned integer parameters.
83     */
84    private BigInteger  p , q, g;
85
86    /** Returns the DSS/DSA parameter "P" */
87    public BigInteger   getP () { return p; }
88
89    /** Returns the DSS/DSA parameter "Q" */
90    public BigInteger   getQ () { return q; }
91
92    /** Returns the DSS/DSA parameter "G" */
93    public BigInteger   getG () { return g; }
94
95    /**
96     * Default constructor.  The OID and parameters must be
97     * deserialized before this algorithm ID is used.
98     */
99    @Deprecated
100    public AlgIdDSA () {}
101
102    AlgIdDSA (DerValue val) throws IOException
103        { super(val.getOID()); }
104
105    /**
106     * Construct an AlgIdDSA from an X.509 encoded byte array.
107     */
108    public AlgIdDSA (byte[] encodedAlg) throws IOException
109        { super (new DerValue(encodedAlg).getOID()); }
110
111    /**
112     * Constructs a DSS/DSA Algorithm ID from unsigned integers that
113     * define the algorithm parameters.  Those integers are encoded
114     * as big-endian byte arrays.
115     *
116     * @param p the DSS/DSA parameter "P"
117     * @param q the DSS/DSA parameter "Q"
118     * @param g the DSS/DSA parameter "G"
119     */
120    public AlgIdDSA (byte[] p, byte[] q, byte[] g)
121    throws IOException
122    {
123        this (new BigInteger (1, p),
124            new BigInteger (1, q),
125            new BigInteger (1, g));
126    }
127
128    /**
129     * Constructs a DSS/DSA Algorithm ID from numeric parameters.
130     * If all three are null, then the parameters portion of the algorithm id
131     * is set to null.  See note in header regarding use.
132     *
133     * @param p the DSS/DSA parameter "P"
134     * @param q the DSS/DSA parameter "Q"
135     * @param g the DSS/DSA parameter "G"
136     */
137    public AlgIdDSA (BigInteger p, BigInteger q, BigInteger g)
138    {
139        super (DSA_oid);
140
141        if (p != null || q != null || g != null) {
142            if (p == null || q == null || g == null)
143                throw new ProviderException("Invalid parameters for DSS/DSA" +
144                                            " Algorithm ID");
145            try {
146                this.p = p;
147                this.q = q;
148                this.g = g;
149                initializeParams ();
150
151            } catch (IOException e) {
152                /* this should not happen */
153                throw new ProviderException ("Construct DSS/DSA Algorithm ID");
154            }
155        }
156    }
157
158    /**
159     * Returns "DSA", indicating the Digital Signature Algorithm (DSA) as
160     * defined by the Digital Signature Standard (DSS), FIPS 186.
161     */
162    public String getName ()
163        { return "DSA"; }
164
165
166    /*
167     * For algorithm IDs which haven't been created from a DER encoded
168     * value, "params" must be created.
169     */
170    private void initializeParams ()
171    throws IOException
172    {
173        DerOutputStream out = new DerOutputStream ();
174
175        out.putInteger(p);
176        out.putInteger(q);
177        out.putInteger(g);
178        params = new DerValue (DerValue.tag_Sequence,out.toByteArray ());
179    }
180
181    /**
182     * Parses algorithm parameters P, Q, and G.  They're found
183     * in the "params" member, which never needs to be changed.
184     */
185    protected void decodeParams ()
186    throws IOException
187    {
188        if (params == null)
189            throw new IOException("DSA alg params are null");
190        if (params.tag != DerValue.tag_Sequence)
191            throw new  IOException("DSA alg parsing error");
192
193        params.data.reset ();
194
195        this.p = params.data.getBigInteger();
196        this.q = params.data.getBigInteger();
197        this.g = params.data.getBigInteger();
198
199        if (params.data.available () != 0)
200            throw new IOException ("AlgIdDSA params, extra="+
201                                   params.data.available ());
202    }
203
204
205    /*
206     * Returns a formatted string describing the parameters.
207     */
208    public String toString ()
209        { return paramsToString (); }
210
211    /*
212     * Returns a string describing the parameters.
213     */
214    protected String paramsToString ()
215    {
216        if (params == null)
217            return " null\n";
218        else
219            return
220                "\n    p:\n" + Debug.toHexString(p) +
221                "\n    q:\n" + Debug.toHexString(q) +
222                "\n    g:\n" + Debug.toHexString(g) +
223                "\n";
224    }
225}
226