1 /*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
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
6 * under the terms of the GNU General Public License version 2 only, as
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 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.security;
27
28 import 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
119 public final class SignedObject implements Serializable {
120
121 @java.io.Serial
122 private static final long serialVersionUID = 720502720485447167L;
123
124 /*
125 * The original content is "deep copied" in its serialized format
126 * and stored in a byte array. The signature field is also in the
127 * form of byte array.
128 */
129
130 private byte[] content;
131 private byte[] signature;
132 private String thealgorithm;
133
134 /**
135 * Constructs a SignedObject from any Serializable object.
136 * The given object is signed with the given signing key, using the
137 * designated signature engine.
138 *
139 * @param object the object to be signed.
140 * @param signingKey the private key for signing.
141 * @param signingEngine the signature signing engine.
142 *
143 * @exception IOException if an error occurs during serialization
144 * @exception InvalidKeyException if the key is invalid.
145 * @exception SignatureException if signing fails.
146 */
147 public SignedObject(Serializable object, PrivateKey signingKey,
148 Signature signingEngine)
149 throws IOException, InvalidKeyException, SignatureException {
150 // creating a stream pipe-line, from a to b
151 ByteArrayOutputStream b = new ByteArrayOutputStream();
152 ObjectOutput a = new ObjectOutputStream(b);
153
154 // write and flush the object content to byte array
155 a.writeObject(object);
156 a.flush();
157 a.close();
158 this.content = b.toByteArray();
159 b.close();
160
161 // now sign the encapsulated object
162 this.sign(signingKey, signingEngine);
163 }
164
165 /**
166 * Retrieves the encapsulated object.
167 * The encapsulated object is de-serialized before it is returned.
168 *
169 * @return the encapsulated object.
170 *
171 * @exception IOException if an error occurs during de-serialization
172 * @exception ClassNotFoundException if an error occurs during
173 * de-serialization
174 */
175 public Object getObject()
176 throws IOException, ClassNotFoundException
177 {
178 // creating a stream pipe-line, from b to a
179 ByteArrayInputStream b = new ByteArrayInputStream(this.content);
180 ObjectInput a = new ObjectInputStream(b);
181 Object obj = a.readObject();
182 b.close();
183 a.close();
184 return obj;
185 }
186
187 /**
188 * Retrieves the signature on the signed object, in the form of a
189 * byte array.
190 *
191 * @return the signature. Returns a new array each time this
192 * method is called.
193 */
194 public byte[] getSignature() {
195 return this.signature.clone();
196 }
197
198 /**
199 * Retrieves the name of the signature algorithm.
200 *
201 * @return the signature algorithm name.
202 */
203 public String getAlgorithm() {
204 return this.thealgorithm;
205 }
206
207 /**
208 * Verifies that the signature in this SignedObject is the valid
209 * signature for the object stored inside, with the given
210 * verification key, using the designated verification engine.
211 *
212 * @param verificationKey the public key for verification.
213 * @param verificationEngine the signature verification engine.
214 *
215 * @exception SignatureException if signature verification failed (an
216 * exception prevented the signature verification engine from completing
217 * normally).
218 * @exception InvalidKeyException if the verification key is invalid.
219 *
220 * @return {@code true} if the signature
221 * is valid, {@code false} otherwise
222 */
223 public boolean verify(PublicKey verificationKey,
224 Signature verificationEngine)
225 throws InvalidKeyException, SignatureException {
226 verificationEngine.initVerify(verificationKey);
227 verificationEngine.update(this.content.clone());
228 return verificationEngine.verify(this.signature.clone());
229 }
230
231 /*
232 * Signs the encapsulated object with the given signing key, using the
233 * designated signature engine.
234 *
235 * @param signingKey the private key for signing.
236 * @param signingEngine the signature signing engine.
237 *
238 * @exception InvalidKeyException if the key is invalid.
239 * @exception SignatureException if signing fails.
240 */
241 private void sign(PrivateKey signingKey, Signature signingEngine)
242 throws InvalidKeyException, SignatureException {
243 // initialize the signing engine
244 signingEngine.initSign(signingKey);
245 signingEngine.update(this.content.clone());
246 this.signature = signingEngine.sign().clone();
247 this.thealgorithm = signingEngine.getAlgorithm();
248 }
249
250 /**
251 * readObject is called to restore the state of the SignedObject from
252 * a stream.
253 */
254 @java.io.Serial
255 private void readObject(java.io.ObjectInputStream s)
256 throws java.io.IOException, ClassNotFoundException {
257 java.io.ObjectInputStream.GetField fields = s.readFields();
258 content = ((byte[])fields.get("content", null)).clone();
259 signature = ((byte[])fields.get("signature", null)).clone();
260 thealgorithm = (String)fields.get("thealgorithm", null);
261 }
262 }