/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 in the LICENSE file that
* accompanied this code).
*
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
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*/
package java.security;
import java.io.*;
import java.security.spec.AlgorithmParameterSpec;
/**
* <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} method.
* A typical usage for signing is the following:
*
* <pre>{@code
* Signature signingEngine = Signature.getInstance(algorithm,
* provider);
* SignedObject so = new SignedObject(myobject, signingKey,
* signingParams, signingEngine);
* }</pre>
*
* <p> A typical usage for verification is the following (having
* received SignedObject {@code so}):
*
* <pre>{@code
* Signature verificationEngine =
* Signature.getInstance(algorithm, provider);
* if (so.verify(verificationKey, verificationParams, verificationEngine))
* try {
* Object myobj = so.getObject();
* } catch (java.lang.ClassNotFoundException e) {};
* }</pre>
*
* <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}
* 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. If signing parameters are used,
* the same parameters must be specified when calling {@code verify}
* method for verification to succeed.
*
* <p> More importantly, for flexibility reasons, the
* constructor and {@code 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 {@code Signature} engine is being
* used, as its own implementation of the {@code verify} method
* is invoked to verify a signature. In other words, a malicious
* {@code Signature} 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-256. The algorithm is specified using the
* same convention as that for signatures. The DSA algorithm using the
* SHA-256 message digest algorithm can be specified, for example, as
* "SHA256withDSA". In the case of
* RSA the signing algorithm could be specified as, for example,
* "SHA256withRSA". 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} 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
*
* @author Li Gong
* @since 1.2
*/
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 with
* no signature parameters, 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
try {
this.sign(signingKey, null, signingEngine);
} catch (InvalidAlgorithmParameterException e) {
// should not happen, re-throw just in case
throw new SignatureException(e);
}
}
/**
* Constructs a SignedObject from any Serializable object.
* The given object is signed with the given signing key and
* signature parameters, using the designated signature engine.
* If the signature algorithm does not use any signature parameters,
* {@code signingParams} should be null.
*
* @param object the object to be signed.
* @param signingKey the private key for signing.
* @param signingParams the signature parameters used for signing,
* may be null.
* @param signingEngine the signature signing engine.
*
* @exception IOException if an error occurs during serialization
* @exception InvalidKeyException if the key is invalid.
* @exception InvalidAlgorithmParameterException if the given signature
* parameters is invalid.
* @exception SignatureException if signing fails.
* @since 11
*/
public SignedObject(Serializable object, PrivateKey signingKey,
AlgorithmParameterSpec signingParams,
Signature signingEngine)
throws IOException, InvalidKeyException,
InvalidAlgorithmParameterException, 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, signingParams, 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() {
return this.signature.clone();
}
/**
* 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 with no signature parameters, using the designated
* verification engine.
*
* @param verificationKey the public key for verification.
* @param verificationEngine the signature verification engine.
*
* @exception SignatureException if signature verification failed (an
* exception prevented the signature verification engine from completing
* normally).
* @exception InvalidKeyException if the verification key is invalid.
*
* @return {@code true} if the signature
* is valid, {@code false} otherwise
*/
public boolean verify(PublicKey verificationKey,
Signature verificationEngine)
throws InvalidKeyException, SignatureException {
try {
return verify(verificationKey, null, verificationEngine);
} catch (InvalidAlgorithmParameterException e) {
// should not happen, re-throw just in case
throw new SignatureException(e);
}
}
/**
* Verifies that the signature in this SignedObject is the valid
* signature for the object stored inside, with the given
* verification key and signature parameters, using the designated
* verification engine. If the signature algorithm does not use any
* signature parameters, {@code verificationParams} should be null.
* When signature parameters are used in signing, the same parameters
* must be specified when calling {@code verify} method for the
* verification to succeed.
*
* @param verificationKey the public key for verification.
* @param verificationParams the signature parameters for verification.
* @param verificationEngine the signature verification engine.
*
* @exception SignatureException if signature verification failed (an
* exception prevented the signature verification engine from completing
* normally).
* @exception InvalidKeyException if the verification key is invalid.
* @exception InvalidAlgorithmParameterException if the given signature
* parameters is invalid
* @return {@code true} if the signature is valid, {@code false} otherwise
* @since 11
*/
public boolean verify(PublicKey verificationKey,
AlgorithmParameterSpec verificationParams,
Signature verificationEngine)
throws InvalidKeyException, InvalidAlgorithmParameterException,
SignatureException {
// set parameteres before Signature.initSign/initVerify call,
// so key can be checked when it's set
try {
verificationEngine.setParameter(verificationParams);
} catch (UnsupportedOperationException e) {
// for backward compatibility, only re-throw when
// parameters is not null
if (verificationParams != null) throw e;
}
verificationEngine.initVerify(verificationKey);
verificationEngine.update(this.content.clone());
return verificationEngine.verify(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 signingParams the signature parameters for signing.
* @param signingEngine the signature signing engine.
*
* @exception InvalidKeyException if the key is invalid.
* @exception InvalidAlgorithmParameterException if the given signature
* parameters is invalid
* @exception SignatureException if signing fails.
*/
private void sign(PrivateKey signingKey,
AlgorithmParameterSpec signingParams,
Signature signingEngine)
throws InvalidKeyException, InvalidAlgorithmParameterException,
SignatureException {
// set parameteres before Signature.initSign/initVerify call,
// so key can be checked when it's set
try {
signingEngine.setParameter(signingParams);
} catch (UnsupportedOperationException e) {
// for backward compatibility, only re-throw when
// parameters is not null
if (signingParams != null) throw e;
}
signingEngine.initSign(signingKey);
signingEngine.update(this.content.clone());
this.signature = 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 {
java.io.ObjectInputStream.GetField fields = s.readFields();
content = ((byte[])fields.get("content", null)).clone();
signature = ((byte[])fields.get("signature", null)).clone();
thealgorithm = (String)fields.get("thealgorithm", null);
}
}