/* * @(#)SignedObject.java 1.44 06/10/10 * * Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License version * 2 only, as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License version 2 for more details (a copy is * included at /legal/license.txt). * * You should have received a copy of the GNU General Public License * version 2 along with this work; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa * Clara, CA 95054 or visit www.sun.com if you need additional * information or have any questions. * */ package java.security; import java.io.*; /** * SignedObject is a class for the purpose of creating authentic * runtime objects whose integrity cannot be compromised without being * detected. * * More specifically, a SignedObject contains another Serializable * object, the (to-be-)signed object and its signature. * * The signed object is a "deep copy" (in serialized form) of an * original object. Once the copy is made, further manipulation of * the original object has no side effect on the copy. * * The underlying signing algorithm is designated by the Signature * object passed to the constructor and the verify method. * A typical usage for signing is the following: * * * Signature signingEngine = Signature.getInstance(algorithm, * provider); * SignedObject so = new SignedObject(myobject, signingKey, * signingEngine); * * * A typical usage for verification is the following (having * received SignedObject so): * * * Signature verificationEngine = * Signature.getInstance(algorithm, provider); * if (so.verify(publickey, verificationEngine)) * try { * Object myobj = so.getObject(); * } catch (java.lang.ClassNotFoundException e) {}; * * * Several points are worth noting. First, there is no need to * initialize the signing or verification engine, as it will be * re-initialized inside the constructor and the verify * method. Secondly, for verification to succeed, the specified * public key must be the public key corresponding to the private key * used to generate the SignedObject. * * More importantly, for flexibility reasons, the * constructor and verify method allow for * customized signature engines, which can implement signature * algorithms that are not installed formally as part of a crypto * provider. However, it is crucial that the programmer writing the * verifier code be aware what Signature engine is being * used, as its own implementation of the verify method * is invoked to verify a signature. In other words, a malicious * Signature may choose to always return true on * verification in an attempt to bypass a security check. * * The signature algorithm can be, among others, the NIST standard * DSA, using DSA and SHA-1. The algorithm is specified using the * same convention as that for signatures. The DSA algorithm using the * SHA-1 message digest algorithm can be specified, for example, as * "SHA/DSA" or "SHA-1/DSA" (they are equivalent). In the case of * RSA, there are multiple choices for the message digest algorithm, * so the signing algorithm could be specified as, for example, * "MD2/RSA", "MD5/RSA" or "SHA-1/RSA". The algorithm name must be * specified, as there is no default. * * The name of the Cryptography Package Provider is designated * also by the Signature parameter to the constructor and the * verify method. If the provider is not * specified, the default provider is used. Each installation can * be configured to use a particular provider as default. * * Potential applications of SignedObject include: * * It can be used * internally to any Java runtime as an unforgeable authorization * token -- one that can be passed around without the fear that the * token can be maliciously modified without being detected. * It * can be used to sign and serialize data/object for storage outside * the Java runtime (e.g., storing critical access control data on * disk). * Nested SignedObjects can be used to construct a logical * sequence of signatures, resembling a chain of authorization and * delegation. * * * @see Signature * * @version 1.37, 02/02/00 * @author Li Gong */ public final class SignedObject implements Serializable { /* * The original content is "deep copied" in its serialized format * and stored in a byte array. The signature field is also in the * form of byte array. */ private byte[] content; private byte[] signature; private String thealgorithm; /** * Constructs a SignedObject from any Serializable object. * The given object is signed with the given signing key, using the * designated signature engine. * * @param object the object to be signed. * @param signingKey the private key for signing. * @param signingEngine the signature signing engine. * * @exception IOException if an error occurs during serialization * @exception InvalidKeyException if the key is invalid. * @exception SignatureException if signing fails. */ public SignedObject(Serializable object, PrivateKey signingKey, Signature signingEngine) throws IOException, InvalidKeyException, SignatureException { // creating a stream pipe-line, from a to b ByteArrayOutputStream b = new ByteArrayOutputStream(); ObjectOutput a = new ObjectOutputStream(b); // write and flush the object content to byte array a.writeObject(object); a.flush(); a.close(); this.content = b.toByteArray(); b.close(); // now sign the encapsulated object this.sign(signingKey, signingEngine); } /** * Retrieves the encapsulated object. * The encapsulated object is de-serialized before it is returned. * * @return the encapsulated object. * * @exception IOException if an error occurs during de-serialization * @exception ClassNotFoundException if an error occurs during * de-serialization */ public Object getObject() throws IOException, ClassNotFoundException { // creating a stream pipe-line, from b to a ByteArrayInputStream b = new ByteArrayInputStream(this.content); ObjectInput a = new ObjectInputStream(b); Object obj = a.readObject(); b.close(); a.close(); return obj; } /** * Retrieves the signature on the signed object, in the form of a * byte array. * * @return the signature. */ public byte[] getSignature() { // return only a clone, for integrity reasons byte[] sig = (byte[])this.signature.clone(); return sig; } /** * Retrieves the name of the signature algorithm. * * @return the signature algorithm name. */ public String getAlgorithm() { return this.thealgorithm; } /** * Verifies that the signature in this SignedObject is the valid * signature for the object stored inside, with the given * verification key, using the designated verification engine. * * @param verificationKey the public key for verification. * @param verificationEngine the signature verification engine. * * @exception SignatureException if signature verification failed. * @exception InvalidKeyException if the verification key is invalid. * * @return true if the signature * is valid, false otherwise */ public boolean verify(PublicKey verificationKey, Signature verificationEngine) throws InvalidKeyException, SignatureException { verificationEngine.initVerify(verificationKey); verificationEngine.update((byte[])this.content.clone()); return verificationEngine.verify((byte[])this.signature.clone()); } /* * Signs the encapsulated object with the given signing key, using the * designated signature engine. * * @param signingKey the private key for signing. * @param signingEngine the signature signing engine. * * @exception InvalidKeyException if the key is invalid. * @exception SignatureException if signing fails. */ private void sign(PrivateKey signingKey, Signature signingEngine) throws InvalidKeyException, SignatureException { // initialize the signing engine signingEngine.initSign(signingKey); signingEngine.update((byte[])this.content.clone()); this.signature = (byte[])signingEngine.sign().clone(); this.thealgorithm = signingEngine.getAlgorithm(); } /** * readObject is called to restore the state of the SignedObject from * a stream. */ private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); content = (byte[])content.clone(); signature = (byte[])signature.clone(); } }
