/*
* @(#)SignedObject.java 1.43 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.security;
import java.io.*;
/**
* <p> SignedObject is a class for the purpose of creating authentic
* runtime objects whose integrity cannot be compromised without being
* detected.
*
* <p> More specifically, a SignedObject contains another Serializable
* object, the (to-be-)signed object and its signature.
*
* <p> 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.
*
* <p> The underlying signing algorithm is designated by the Signature
* object passed to the constructor and the <code>verify</code> method.
* A typical usage for signing is the following:
*
* <p> <code> <pre>
* Signature signingEngine = Signature.getInstance(algorithm,
* provider);
* SignedObject so = new SignedObject(myobject, signingKey,
* signingEngine);
* </pre> </code>
*
* <p> A typical usage for verification is the following (having
* received SignedObject <code>so</code>):
*
* <p> <code> <pre>
* Signature verificationEngine =
* Signature.getInstance(algorithm, provider);
* if (so.verify(publickey, verificationEngine))
* try {
* Object myobj = so.getObject();
* } catch (java.lang.ClassNotFoundException e) {};
* </pre> </code>
*
* <p> 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 <code>verify</code>
* 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.
*
* <p> More importantly, for flexibility reasons, the
* constructor and <code>verify</code> 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 <code>Signature</code> engine is being
* used, as its own implementation of the <code>verify</code> method
* is invoked to verify a signature. In other words, a malicious
* <code>Signature</code> may choose to always return true on
* verification in an attempt to bypass a security check.
*
* <p> 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.
*
* <p> The name of the Cryptography Package Provider is designated
* also by the Signature parameter to the constructor and the
* <code>verify</code> method. If the provider is not
* specified, the default provider is used. Each installation can
* be configured to use a particular provider as default.
*
* <p> Potential applications of SignedObject include:
* <ul>
* <li> 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.
* <li> 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).
* <li> Nested SignedObjects can be used to construct a logical
* sequence of signatures, resembling a chain of authorization and
* delegation.
* </ul>
*
* @see Signature
*
* @version 1.43, 12/19/03
* @author Li Gong
*/
public final class SignedObject implements Serializable {
private static final long serialVersionUID = 720502720485447167L;
/*
* 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. Returns a new array each time this
* method is called.
*/
public byte[] getSignature() {
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 <tt>true</tt> if the signature
* is valid, <tt>false</tt> 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();
}
}
|
