1 /* BaseKeyAgreementParty.java --
2    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
3 
4 This file is a part of GNU Classpath.
5 
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or (at
9 your option) any later version.
10 
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 General Public License for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; if not, write to the Free Software
18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
19 USA
20 
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library.  Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25 
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module.  An independent module is a module which is not derived from
33 or based on this library.  If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so.  If you do not wish to do so, delete this
36 exception statement from your version.  */
37 
38 
39 package gnu.javax.crypto.key;
40 
41 import gnu.java.security.prng.IRandom;
42 import gnu.java.security.prng.LimitReachedException;
43 import gnu.java.security.util.PRNG;
44 
45 import java.math.BigInteger;
46 import java.security.SecureRandom;
47 import java.util.Map;
48 
49 /**
50  * A base abstract class to facilitate implementations of concrete key agreement
51  * protocol handlers.
52  */
53 public abstract class BaseKeyAgreementParty
54     implements IKeyAgreementParty
55 {
56   protected static final BigInteger TWO = BigInteger.valueOf(2L);
57   /** The canonical name of the protocol. */
58   protected String name;
59   /** Whether the instance is initialised or not. */
60   protected boolean initialised = false;
61   /** The current step index of the protocol exchange. */
62   protected int step = -1;
63   /** Whether the exchange has concluded or not. */
64   protected boolean complete = false;
65   /** The optional {@link SecureRandom} instance to use. */
66   protected SecureRandom rnd = null;
67   /** The optional {@link IRandom} instance to use. */
68   protected IRandom irnd = null;
69   /** Our default source of randomness. */
70   private PRNG prng = null;
71 
BaseKeyAgreementParty(String name)72   protected BaseKeyAgreementParty(String name)
73   {
74     super();
75 
76     this.name = name;
77   }
78 
name()79   public String name()
80   {
81     return name;
82   }
83 
init(Map attributes)84   public void init(Map attributes) throws KeyAgreementException
85   {
86     if (initialised)
87       throw new IllegalStateException("already initialised");
88     this.engineInit(attributes);
89     initialised = true;
90     this.step = -1;
91     this.complete = false;
92   }
93 
processMessage(IncomingMessage in)94   public OutgoingMessage processMessage(IncomingMessage in)
95       throws KeyAgreementException
96   {
97     if (! initialised)
98       throw new IllegalStateException("not initialised");
99     if (complete)
100       throw new IllegalStateException("exchange has already concluded");
101     step++;
102     return this.engineProcessMessage(in);
103   }
104 
isComplete()105   public boolean isComplete()
106   {
107     return complete;
108   }
109 
getSharedSecret()110   public byte[] getSharedSecret() throws KeyAgreementException
111   {
112     if (! initialised)
113       throw new KeyAgreementException("not yet initialised");
114     if (! isComplete())
115       throw new KeyAgreementException("not yet computed");
116     return engineSharedSecret();
117   }
118 
reset()119   public void reset()
120   {
121     if (initialised)
122       {
123         this.engineReset();
124         initialised = false;
125       }
126   }
127 
engineInit(Map attributes)128   protected abstract void engineInit(Map attributes)
129       throws KeyAgreementException;
130 
engineProcessMessage(IncomingMessage in)131   protected abstract OutgoingMessage engineProcessMessage(IncomingMessage in)
132       throws KeyAgreementException;
133 
engineSharedSecret()134   protected abstract byte[] engineSharedSecret() throws KeyAgreementException;
135 
engineReset()136   protected abstract void engineReset();
137 
138   /**
139    * Fills the designated byte array with random data.
140    *
141    * @param buffer the byte array to fill with random data.
142    */
nextRandomBytes(byte[] buffer)143   protected void nextRandomBytes(byte[] buffer)
144   {
145     if (rnd != null)
146       rnd.nextBytes(buffer);
147     else if (irnd != null)
148       try
149         {
150           irnd.nextBytes(buffer, 0, buffer.length);
151         }
152       catch (LimitReachedException lre)
153         {
154           irnd = null;
155           getDefaultPRNG().nextBytes(buffer);
156         }
157     else
158       getDefaultPRNG().nextBytes(buffer);
159   }
160 
getDefaultPRNG()161   private PRNG getDefaultPRNG()
162   {
163     if (prng == null)
164       prng = PRNG.getInstance();
165 
166     return prng;
167   }
168 }
169