1/*
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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
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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).
16 *
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24 */
25
26package java.security;
27
28import java.io.*;
29
30/**
31 * <p> SignedObject is a class for the purpose of creating authentic
32 * runtime objects whose integrity cannot be compromised without being
33 * detected.
34 *
35 * <p> More specifically, a SignedObject contains another Serializable
36 * object, the (to-be-)signed object and its signature.
37 *
38 * <p> The signed object is a "deep copy" (in serialized form) of an
39 * original object.  Once the copy is made, further manipulation of
40 * the original object has no side effect on the copy.
41 *
42 * <p> The underlying signing algorithm is designated by the Signature
43 * object passed to the constructor and the {@code verify} method.
44 * A typical usage for signing is the following:
45 *
46 * <pre>{@code
47 * Signature signingEngine = Signature.getInstance(algorithm,
48 *                                                 provider);
49 * SignedObject so = new SignedObject(myobject, signingKey,
50 *                                    signingEngine);
51 * }</pre>
52 *
53 * <p> A typical usage for verification is the following (having
54 * received SignedObject {@code so}):
55 *
56 * <pre>{@code
57 * Signature verificationEngine =
58 *     Signature.getInstance(algorithm, provider);
59 * if (so.verify(publickey, verificationEngine))
60 *     try {
61 *         Object myobj = so.getObject();
62 *     } catch (java.lang.ClassNotFoundException e) {};
63 * }</pre>
64 *
65 * <p> Several points are worth noting.  First, there is no need to
66 * initialize the signing or verification engine, as it will be
67 * re-initialized inside the constructor and the {@code verify}
68 * method. Secondly, for verification to succeed, the specified
69 * public key must be the public key corresponding to the private key
70 * used to generate the SignedObject.
71 *
72 * <p> More importantly, for flexibility reasons, the
73 * constructor and {@code verify} method allow for
74 * customized signature engines, which can implement signature
75 * algorithms that are not installed formally as part of a crypto
76 * provider.  However, it is crucial that the programmer writing the
77 * verifier code be aware what {@code Signature} engine is being
78 * used, as its own implementation of the {@code verify} method
79 * is invoked to verify a signature.  In other words, a malicious
80 * {@code Signature} may choose to always return true on
81 * verification in an attempt to bypass a security check.
82 *
83 * <p> The signature algorithm can be, among others, the NIST standard
84 * DSA, using DSA and SHA-256.  The algorithm is specified using the
85 * same convention as that for signatures. The DSA algorithm using the
86 * SHA-256 message digest algorithm can be specified, for example, as
87 * "SHA256withDSA".  In the case of
88 * RSA the signing algorithm could be specified as, for example,
89 * "SHA256withRSA".  The algorithm name must be
90 * specified, as there is no default.
91 *
92 * <p> The name of the Cryptography Package Provider is designated
93 * also by the Signature parameter to the constructor and the
94 * {@code verify} method.  If the provider is not
95 * specified, the default provider is used.  Each installation can
96 * be configured to use a particular provider as default.
97 *
98 * <p> Potential applications of SignedObject include:
99 * <ul>
100 * <li> It can be used
101 * internally to any Java runtime as an unforgeable authorization
102 * token -- one that can be passed around without the fear that the
103 * token can be maliciously modified without being detected.
104 * <li> It
105 * can be used to sign and serialize data/object for storage outside
106 * the Java runtime (e.g., storing critical access control data on
107 * disk).
108 * <li> Nested SignedObjects can be used to construct a logical
109 * sequence of signatures, resembling a chain of authorization and
110 * delegation.
111 * </ul>
112 *
113 * @see Signature
114 *
115 * @author Li Gong
116 * @since 1.2
117 */
118
119public final class SignedObject implements Serializable {
120
121    private static final long serialVersionUID = 720502720485447167L;
122
123    /*
124     * The original content is "deep copied" in its serialized format
125     * and stored in a byte array.  The signature field is also in the
126     * form of byte array.
127     */
128
129    private byte[] content;
130    private byte[] signature;
131    private String thealgorithm;
132
133    /**
134     * Constructs a SignedObject from any Serializable object.
135     * The given object is signed with the given signing key, using the
136     * designated signature engine.
137     *
138     * @param object the object to be signed.
139     * @param signingKey the private key for signing.
140     * @param signingEngine the signature signing engine.
141     *
142     * @exception IOException if an error occurs during serialization
143     * @exception InvalidKeyException if the key is invalid.
144     * @exception SignatureException if signing fails.
145     */
146    public SignedObject(Serializable object, PrivateKey signingKey,
147                        Signature signingEngine)
148        throws IOException, InvalidKeyException, SignatureException {
149            // creating a stream pipe-line, from a to b
150            ByteArrayOutputStream b = new ByteArrayOutputStream();
151            ObjectOutput a = new ObjectOutputStream(b);
152
153            // write and flush the object content to byte array
154            a.writeObject(object);
155            a.flush();
156            a.close();
157            this.content = b.toByteArray();
158            b.close();
159
160            // now sign the encapsulated object
161            this.sign(signingKey, signingEngine);
162    }
163
164    /**
165     * Retrieves the encapsulated object.
166     * The encapsulated object is de-serialized before it is returned.
167     *
168     * @return the encapsulated object.
169     *
170     * @exception IOException if an error occurs during de-serialization
171     * @exception ClassNotFoundException if an error occurs during
172     * de-serialization
173     */
174    public Object getObject()
175        throws IOException, ClassNotFoundException
176    {
177        // creating a stream pipe-line, from b to a
178        ByteArrayInputStream b = new ByteArrayInputStream(this.content);
179        ObjectInput a = new ObjectInputStream(b);
180        Object obj = a.readObject();
181        b.close();
182        a.close();
183        return obj;
184    }
185
186    /**
187     * Retrieves the signature on the signed object, in the form of a
188     * byte array.
189     *
190     * @return the signature. Returns a new array each time this
191     * method is called.
192     */
193    public byte[] getSignature() {
194        return this.signature.clone();
195    }
196
197    /**
198     * Retrieves the name of the signature algorithm.
199     *
200     * @return the signature algorithm name.
201     */
202    public String getAlgorithm() {
203        return this.thealgorithm;
204    }
205
206    /**
207     * Verifies that the signature in this SignedObject is the valid
208     * signature for the object stored inside, with the given
209     * verification key, using the designated verification engine.
210     *
211     * @param verificationKey the public key for verification.
212     * @param verificationEngine the signature verification engine.
213     *
214     * @exception SignatureException if signature verification failed (an
215     *     exception prevented the signature verification engine from completing
216     *     normally).
217     * @exception InvalidKeyException if the verification key is invalid.
218     *
219     * @return {@code true} if the signature
220     * is valid, {@code false} otherwise
221     */
222    public boolean verify(PublicKey verificationKey,
223                          Signature verificationEngine)
224         throws InvalidKeyException, SignatureException {
225             verificationEngine.initVerify(verificationKey);
226             verificationEngine.update(this.content.clone());
227             return verificationEngine.verify(this.signature.clone());
228    }
229
230    /*
231     * Signs the encapsulated object with the given signing key, using the
232     * designated signature engine.
233     *
234     * @param signingKey the private key for signing.
235     * @param signingEngine the signature signing engine.
236     *
237     * @exception InvalidKeyException if the key is invalid.
238     * @exception SignatureException if signing fails.
239     */
240    private void sign(PrivateKey signingKey, Signature signingEngine)
241        throws InvalidKeyException, SignatureException {
242            // initialize the signing engine
243            signingEngine.initSign(signingKey);
244            signingEngine.update(this.content.clone());
245            this.signature = signingEngine.sign().clone();
246            this.thealgorithm = signingEngine.getAlgorithm();
247    }
248
249    /**
250     * readObject is called to restore the state of the SignedObject from
251     * a stream.
252     */
253    private void readObject(java.io.ObjectInputStream s)
254        throws java.io.IOException, ClassNotFoundException {
255            java.io.ObjectInputStream.GetField fields = s.readFields();
256            content = ((byte[])fields.get("content", null)).clone();
257            signature = ((byte[])fields.get("signature", null)).clone();
258            thealgorithm = (String)fields.get("thealgorithm", null);
259    }
260}
261