259 lines
9.8 KiB
Java
259 lines
9.8 KiB
Java
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/*
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* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.security;
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import java.io.*;
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/**
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* <p> SignedObject is a class for the purpose of creating authentic
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* runtime objects whose integrity cannot be compromised without being
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* detected.
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*
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* <p> More specifically, a SignedObject contains another Serializable
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* object, the (to-be-)signed object and its signature.
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*
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* <p> The signed object is a "deep copy" (in serialized form) of an
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* original object. Once the copy is made, further manipulation of
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* the original object has no side effect on the copy.
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*
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* <p> The underlying signing algorithm is designated by the Signature
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* object passed to the constructor and the {@code verify} method.
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* A typical usage for signing is the following:
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*
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* <pre>{@code
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* Signature signingEngine = Signature.getInstance(algorithm,
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* provider);
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* SignedObject so = new SignedObject(myobject, signingKey,
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* signingEngine);
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* }</pre>
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*
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* <p> A typical usage for verification is the following (having
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* received SignedObject {@code so}):
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*
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* <pre>{@code
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* Signature verificationEngine =
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* Signature.getInstance(algorithm, provider);
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* if (so.verify(publickey, verificationEngine))
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* try {
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* Object myobj = so.getObject();
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* } catch (java.lang.ClassNotFoundException e) {};
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* }</pre>
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*
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* <p> Several points are worth noting. First, there is no need to
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* initialize the signing or verification engine, as it will be
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* re-initialized inside the constructor and the {@code verify}
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* method. Secondly, for verification to succeed, the specified
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* public key must be the public key corresponding to the private key
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* used to generate the SignedObject.
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*
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* <p> More importantly, for flexibility reasons, the
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* constructor and {@code verify} method allow for
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* customized signature engines, which can implement signature
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* algorithms that are not installed formally as part of a crypto
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* provider. However, it is crucial that the programmer writing the
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* verifier code be aware what {@code Signature} engine is being
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* used, as its own implementation of the {@code verify} method
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* is invoked to verify a signature. In other words, a malicious
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* {@code Signature} may choose to always return true on
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* verification in an attempt to bypass a security check.
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*
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* <p> The signature algorithm can be, among others, the NIST standard
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* DSA, using DSA and SHA-256. The algorithm is specified using the
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* same convention as that for signatures. The DSA algorithm using the
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* SHA-256 message digest algorithm can be specified, for example, as
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* "SHA256withDSA". In the case of
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* RSA the signing algorithm could be specified as, for example,
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* "SHA256withRSA". The algorithm name must be
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* specified, as there is no default.
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*
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* <p> The name of the Cryptography Package Provider is designated
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* also by the Signature parameter to the constructor and the
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* {@code verify} method. If the provider is not
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* specified, the default provider is used. Each installation can
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* be configured to use a particular provider as default.
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*
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* <p> Potential applications of SignedObject include:
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* <ul>
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* <li> It can be used
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* internally to any Java runtime as an unforgeable authorization
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* token -- one that can be passed around without the fear that the
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* token can be maliciously modified without being detected.
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* <li> It
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* can be used to sign and serialize data/object for storage outside
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* the Java runtime (e.g., storing critical access control data on
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* disk).
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* <li> Nested SignedObjects can be used to construct a logical
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* sequence of signatures, resembling a chain of authorization and
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* delegation.
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* </ul>
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*
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* @see Signature
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*
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* @author Li Gong
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* @since 1.2
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*/
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public final class SignedObject implements Serializable {
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private static final long serialVersionUID = 720502720485447167L;
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/*
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* The original content is "deep copied" in its serialized format
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* and stored in a byte array. The signature field is also in the
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* form of byte array.
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*/
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private byte[] content;
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private byte[] signature;
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private String thealgorithm;
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/**
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* Constructs a SignedObject from any Serializable object.
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* The given object is signed with the given signing key, using the
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* designated signature engine.
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*
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* @param object the object to be signed.
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* @param signingKey the private key for signing.
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* @param signingEngine the signature signing engine.
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*
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* @exception IOException if an error occurs during serialization
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* @exception InvalidKeyException if the key is invalid.
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* @exception SignatureException if signing fails.
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*/
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public SignedObject(Serializable object, PrivateKey signingKey,
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Signature signingEngine)
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throws IOException, InvalidKeyException, SignatureException {
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// creating a stream pipe-line, from a to b
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ByteArrayOutputStream b = new ByteArrayOutputStream();
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ObjectOutput a = new ObjectOutputStream(b);
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// write and flush the object content to byte array
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a.writeObject(object);
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a.flush();
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a.close();
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this.content = b.toByteArray();
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b.close();
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// now sign the encapsulated object
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this.sign(signingKey, signingEngine);
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}
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/**
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* Retrieves the encapsulated object.
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* The encapsulated object is de-serialized before it is returned.
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*
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* @return the encapsulated object.
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*
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* @exception IOException if an error occurs during de-serialization
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* @exception ClassNotFoundException if an error occurs during
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* de-serialization
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*/
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public Object getObject()
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throws IOException, ClassNotFoundException
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{
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// creating a stream pipe-line, from b to a
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ByteArrayInputStream b = new ByteArrayInputStream(this.content);
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ObjectInput a = new ObjectInputStream(b);
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Object obj = a.readObject();
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b.close();
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a.close();
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return obj;
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}
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/**
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* Retrieves the signature on the signed object, in the form of a
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* byte array.
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*
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* @return the signature. Returns a new array each time this
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* method is called.
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*/
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public byte[] getSignature() {
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return this.signature.clone();
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}
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/**
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* Retrieves the name of the signature algorithm.
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*
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* @return the signature algorithm name.
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*/
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public String getAlgorithm() {
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return this.thealgorithm;
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}
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/**
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* Verifies that the signature in this SignedObject is the valid
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* signature for the object stored inside, with the given
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* verification key, using the designated verification engine.
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*
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* @param verificationKey the public key for verification.
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* @param verificationEngine the signature verification engine.
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*
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* @exception SignatureException if signature verification failed.
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* @exception InvalidKeyException if the verification key is invalid.
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*
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* @return {@code true} if the signature
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* is valid, {@code false} otherwise
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*/
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public boolean verify(PublicKey verificationKey,
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Signature verificationEngine)
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throws InvalidKeyException, SignatureException {
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verificationEngine.initVerify(verificationKey);
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verificationEngine.update(this.content.clone());
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return verificationEngine.verify(this.signature.clone());
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}
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/*
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* Signs the encapsulated object with the given signing key, using the
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* designated signature engine.
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*
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* @param signingKey the private key for signing.
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* @param signingEngine the signature signing engine.
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*
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* @exception InvalidKeyException if the key is invalid.
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* @exception SignatureException if signing fails.
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*/
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private void sign(PrivateKey signingKey, Signature signingEngine)
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throws InvalidKeyException, SignatureException {
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// initialize the signing engine
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signingEngine.initSign(signingKey);
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signingEngine.update(this.content.clone());
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this.signature = signingEngine.sign().clone();
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this.thealgorithm = signingEngine.getAlgorithm();
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}
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/**
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* readObject is called to restore the state of the SignedObject from
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* a stream.
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*/
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private void readObject(java.io.ObjectInputStream s)
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throws java.io.IOException, ClassNotFoundException {
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java.io.ObjectInputStream.GetField fields = s.readFields();
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content = ((byte[])fields.get("content", null)).clone();
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signature = ((byte[])fields.get("signature", null)).clone();
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thealgorithm = (String)fields.get("thealgorithm", null);
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}
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}
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