001/* SignedObject.java --- Signed Object Class
002   Copyright (C) 1999, 2003, Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.security;
039
040import java.io.ByteArrayInputStream;
041import java.io.ByteArrayOutputStream;
042import java.io.IOException;
043import java.io.ObjectInput;
044import java.io.ObjectInputStream;
045import java.io.ObjectOutputStream;
046import 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 */
082public 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}