001    /* SignedObject.java --- Signed Object Class
002       Copyright (C) 1999, 2003, Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.security;
039    
040    import java.io.ByteArrayInputStream;
041    import java.io.ByteArrayOutputStream;
042    import java.io.IOException;
043    import java.io.ObjectInput;
044    import java.io.ObjectInputStream;
045    import java.io.ObjectOutputStream;
046    import java.io.Serializable;
047    
048    /**
049     * <code>SignedObject</code> is used for storing runtime objects whose
050     * integrity cannot be compromised without being detected.
051     *
052     * <p><code>SignedObject</code> contains a {@link Serializable} object which is
053     * yet to be signed and a digital signature of that object.</p>
054     *
055     * <p>The signed copy is a "deep copy" (in serialized form) of an original
056     * object. Any changes to that original instance are not reflected in the
057     * enclosed copy inside this <code>SignedObject</code>.</p>
058     *
059     * <p>Several things to note are that, first there is no need to initialize the
060     * signature engine as this class will handle that automatically. Second,
061     * verification will only succeed if the public key corresponds to the private
062     * key used to generate the digital signature inside this
063     * <code>SignedObject</code>.</p>
064     *
065     * <p>For fexibility, the signature engine can be specified in the constructor
066     * or the <code>verify()</code> method. Programmers wishing to verify
067     * <code>SignedObject</code>s should be aware of the {@link Signature} engine
068     * they use. A malicious or flawed {@link Signature} implementation may always
069     * return true on verification thus circumventing the intended secrity check
070     * provided by the <code>SignedObject</code>.</p>
071     *
072     * <p>The GNU security provider offers an implementation of the standard NIST
073     * DSA which uses "DSA" and "SHA-1". It can be specified by "SHA/DSA",
074     * "SHA-1/DSA" or its OID. If the RSA signature algorithm is provided then it
075     * could be "MD2/RSA". "MD5/RSA", or "SHA-1/RSA". The algorithm must be
076     * specified because there is no default.</p>
077     *
078     * @author Mark Benvenuto (ivymccough@worldnet.att.net)
079     * @since 1.2
080     * @see Signature
081     */
082    public final class SignedObject implements Serializable
083    {
084      private static final long serialVersionUID = 720502720485447167L;
085    
086      /** @serial */
087      private byte[] content;
088      /** @serial */
089      private byte[] signature;
090      /** @serial */
091      private String thealgorithm;
092    
093      /**
094       * Constructs a new instance of <code>SignedObject</code> from a
095       * {@link Serializable} object. The object is signed with a designated
096       * private key and a signature engine.
097       *
098       * @param object
099       *          the object to sign.
100       * @param signingKey
101       *          the key to use.
102       * @param signingEngine
103       *          the signature engine to use.
104       * @throws IOException
105       *           if a serialization error occurred.
106       * @throws InvalidKeyException
107       *           if the key is invalid.
108       * @throws SignatureException
109       *           if a signing error occurs.
110       */
111      public SignedObject(Serializable object, PrivateKey signingKey,
112                          Signature signingEngine)
113        throws IOException, InvalidKeyException, SignatureException
114      {
115        thealgorithm = signingEngine.getAlgorithm();
116    
117        ByteArrayOutputStream ostream = new ByteArrayOutputStream();
118        ObjectOutputStream p = new ObjectOutputStream(ostream);
119        p.writeObject(object);
120        p.flush();
121        p.close();
122    
123        content = ostream.toByteArray();
124    
125        signingEngine.initSign(signingKey);
126        signingEngine.update(content);
127        signature = signingEngine.sign();
128      }
129    
130      /**
131       * Returns the encapsulated object. The object is de-serialized before being
132       * returned.
133       *
134       * @return the encapsulated object.
135       * @throws IOException
136       *           if a de-serialization error occurs.
137       * @throws ClassNotFoundException
138       *           if the encapsulated object's class was not found.
139       */
140      public Object getObject() throws IOException, ClassNotFoundException
141      {
142        ByteArrayInputStream bais = new ByteArrayInputStream(content);
143        ObjectInput oi = new ObjectInputStream(bais);
144        Object obj = oi.readObject();
145        oi.close();
146        bais.close();
147    
148        return obj;
149      }
150    
151      /**
152       * Returns the signature bytes of the encapsulated object.
153       *
154       * @return the signature bytes of the encapsulated object.
155       */
156      public byte[] getSignature()
157      {
158        return (byte[]) signature.clone();
159    
160      }
161    
162      /**
163       * Returns the name of the signature algorithm.
164       *
165       * @return the name of the signature algorithm.
166       */
167      public String getAlgorithm()
168      {
169        return thealgorithm;
170      }
171    
172      /**
173       * Verifies the encapsulated digital signature by checking that it was
174       * generated by the owner of a designated public key.
175       *
176       * @param verificationKey
177       *          the public key to use.
178       * @param verificationEngine
179       *          the signature engine to use.
180       * @return <code>true</code> if signature is correct, <code>false</code>
181       *         otherwise.
182       * @throws InvalidKeyException
183       *           if the key is invalid.
184       * @throws SignatureException
185       *           if verification fails.
186       */
187      public boolean verify(PublicKey verificationKey, Signature verificationEngine)
188        throws InvalidKeyException, SignatureException
189      {
190        verificationEngine.initVerify(verificationKey);
191        verificationEngine.update(content);
192        return verificationEngine.verify(signature);
193      }
194    
195      /** Called to restore the state of the SignedObject from a stream. */
196      private void readObject(ObjectInputStream s)
197        throws IOException, ClassNotFoundException
198      {
199        s.defaultReadObject();
200        content = (byte[]) content.clone();
201        signature = (byte[]) signature.clone();
202      }
203    }