Signature class, which is used to provide the
* functionality of a digital signature algorithm. Digital signatures are used
* for authentication and integrity assurance of digital data.
*.
* All the abstract methods in this class must be implemented by each * cryptographic service provider who wishes to supply the implementation * of a particular signature algorithm. * * @author Benjamin Renaud * * * @see Signature */ public abstract class SignatureSpi { /** * Application-specified source of randomness. */ protected SecureRandom appRandom = null; /** * Initializes this signature object with the specified * public key for verification operations. * * @param publicKey the public key of the identity whose signature is * going to be verified. * * @exception InvalidKeyException if the key is improperly * encoded, parameters are missing, and so on. */ protected abstract void engineInitVerify(PublicKey publicKey) throws InvalidKeyException; /** * Initializes this signature object with the specified * private key for signing operations. * * @param privateKey the private key of the identity whose signature * will be generated. * * @exception InvalidKeyException if the key is improperly * encoded, parameters are missing, and so on. */ protected abstract void engineInitSign(PrivateKey privateKey) throws InvalidKeyException; /** * Initializes this signature object with the specified * private key and source of randomness for signing operations. * *
This concrete method has been added to this previously-defined
* abstract class. (For backwards compatibility, it cannot be abstract.)
*
* @param privateKey the private key of the identity whose signature
* will be generated.
* @param random the source of randomness
*
* @exception InvalidKeyException if the key is improperly
* encoded, parameters are missing, and so on.
*/
protected void engineInitSign(PrivateKey privateKey,
SecureRandom random)
throws InvalidKeyException {
this.appRandom = random;
engineInitSign(privateKey);
}
/**
* Updates the data to be signed or verified
* using the specified byte.
*
* @param b the byte to use for the update.
*
* @exception SignatureException if the engine is not initialized
* properly.
*/
protected abstract void engineUpdate(byte b) throws SignatureException;
/**
* Updates the data to be signed or verified, using the
* specified array of bytes, starting at the specified offset.
*
* @param b the array of bytes
* @param off the offset to start from in the array of bytes
* @param len the number of bytes to use, starting at offset
*
* @exception SignatureException if the engine is not initialized
* properly
*/
protected abstract void engineUpdate(byte[] b, int off, int len)
throws SignatureException;
/**
* Updates the data to be signed or verified using the specified
* ByteBuffer. Processes the data.remaining() bytes
* starting at at data.position().
* Upon return, the buffer's position will be equal to its limit;
* its limit will not have changed.
*
* @param input the ByteBuffer
* @since 1.5
*/
protected void engineUpdate(ByteBuffer input) {
if (input.hasRemaining() == false) {
return;
}
try {
if (input.hasArray()) {
byte[] b = input.array();
int ofs = input.arrayOffset();
int pos = input.position();
int lim = input.limit();
engineUpdate(b, ofs + pos, lim - pos);
input.position(lim);
} else {
int len = input.remaining();
byte[] b = new byte[JCAUtil.getTempArraySize(len)];
while (len > 0) {
int chunk = Math.min(len, b.length);
input.get(b, 0, chunk);
engineUpdate(b, 0, chunk);
len -= chunk;
}
}
} catch (SignatureException e) {
// is specified to only occur when the engine is not initialized
// this case should never occur as it is caught in Signature.java
throw new ProviderException("update() failed", e);
}
}
/**
* Returns the signature bytes of all the data
* updated so far.
* The format of the signature depends on the underlying
* signature scheme.
*
* @return the signature bytes of the signing operation's result.
*
* @exception SignatureException if the engine is not
* initialized properly or if this signature algorithm is unable to
* process the input data provided.
*/
protected abstract byte[] engineSign() throws SignatureException;
/**
* Finishes this signature operation and stores the resulting signature
* bytes in the provided buffer outbuf, starting at
* offset.
* The format of the signature depends on the underlying
* signature scheme.
*
*
The signature implementation is reset to its initial state
* (the state it was in after a call to one of the
* engineInitSign methods)
* and can be reused to generate further signatures with the same private
* key.
*
* This method should be abstract, but we leave it concrete for
* binary compatibility. Knowledgeable providers should override this
* method.
*
* @param outbuf buffer for the signature result.
*
* @param offset offset into outbuf where the signature is
* stored.
*
* @param len number of bytes within outbuf allotted for the
* signature.
* Both this default implementation and the SUN provider do not
* return partial digests. If the value of this parameter is less
* than the actual signature length, this method will throw a
* SignatureException.
* This parameter is ignored if its value is greater than or equal to
* the actual signature length.
*
* @return the number of bytes placed into outbuf
*
* @exception SignatureException if the engine is not
* initialized properly, if this signature algorithm is unable to
* process the input data provided, or if len is less
* than the actual signature length.
*
* @since 1.2
*/
protected int engineSign(byte[] outbuf, int offset, int len)
throws SignatureException {
byte[] sig = engineSign();
if (len < sig.length) {
throw new SignatureException
("partial signatures not returned");
}
if (outbuf.length - offset < sig.length) {
throw new SignatureException
("insufficient space in the output buffer to store the "
+ "signature");
}
System.arraycopy(sig, 0, outbuf, offset, sig.length);
return sig.length;
}
/**
* Verifies the passed-in signature.
*
* @param sigBytes the signature bytes to be verified.
*
* @return true if the signature was verified, false if not.
*
* @exception SignatureException if the engine is not
* initialized properly, the passed-in signature is improperly
* encoded or of the wrong type, if this signature algorithm is unable to
* process the input data provided, etc.
*/
protected abstract boolean engineVerify(byte[] sigBytes)
throws SignatureException;
/**
* Verifies the passed-in signature in the specified array
* of bytes, starting at the specified offset.
*
*
Note: Subclasses should overwrite the default implementation.
*
*
* @param sigBytes the signature bytes to be verified.
* @param offset the offset to start from in the array of bytes.
* @param length the number of bytes to use, starting at offset.
*
* @return true if the signature was verified, false if not.
*
* @exception SignatureException if the engine is not
* initialized properly, the passed-in signature is improperly
* encoded or of the wrong type, if this signature algorithm is unable to
* process the input data provided, etc.
* @since 1.4
*/
protected boolean engineVerify(byte[] sigBytes, int offset, int length)
throws SignatureException {
byte[] sigBytesCopy = new byte[length];
System.arraycopy(sigBytes, offset, sigBytesCopy, 0, length);
return engineVerify(sigBytesCopy);
}
/**
* Sets the specified algorithm parameter to the specified
* value. This method supplies a general-purpose mechanism through
* which it is possible to set the various parameters of this object.
* A parameter may be any settable parameter for the algorithm, such as
* a parameter size, or a source of random bits for signature generation
* (if appropriate), or an indication of whether or not to perform
* a specific but optional computation. A uniform algorithm-specific
* naming scheme for each parameter is desirable but left unspecified
* at this time.
*
* @param param the string identifier of the parameter.
*
* @param value the parameter value.
*
* @exception InvalidParameterException if param is an
* invalid parameter for this signature algorithm engine,
* the parameter is already set
* and cannot be set again, a security exception occurs, and so on.
*
* @deprecated Replaced by {@link
* #engineSetParameter(java.security.spec.AlgorithmParameterSpec)
* engineSetParameter}.
*/
@Deprecated
protected abstract void engineSetParameter(String param, Object value)
throws InvalidParameterException;
/**
*
This method is overridden by providers to initialize * this signature engine with the specified parameter set. * * @param params the parameters * * @exception UnsupportedOperationException if this method is not * overridden by a provider * * @exception InvalidAlgorithmParameterException if this method is * overridden by a provider and the given parameters * are inappropriate for this signature engine */ protected void engineSetParameter(AlgorithmParameterSpec params) throws InvalidAlgorithmParameterException { throw new UnsupportedOperationException(); } /** *
This method is overridden by providers to return the * parameters used with this signature engine, or null * if this signature engine does not use any parameters. * *
The returned parameters may be the same that were used to initialize
* this signature engine, or may contain a combination of default and
* randomly generated parameter values used by the underlying signature
* implementation if this signature engine requires algorithm parameters
* but was not initialized with any.
*
* @return the parameters used with this signature engine, or null if this
* signature engine does not use any parameters
*
* @exception UnsupportedOperationException if this method is
* not overridden by a provider
* @since 1.4
*/
protected AlgorithmParameters engineGetParameters() {
throw new UnsupportedOperationException();
}
/**
* Gets the value of the specified algorithm parameter.
* This method supplies a general-purpose mechanism through which it
* is possible to get the various parameters of this object. A parameter
* may be any settable parameter for the algorithm, such as a parameter
* size, or a source of random bits for signature generation (if
* appropriate), or an indication of whether or not to perform a
* specific but optional computation. A uniform algorithm-specific
* naming scheme for each parameter is desirable but left unspecified
* at this time.
*
* @param param the string name of the parameter.
*
* @return the object that represents the parameter value, or null if
* there is none.
*
* @exception InvalidParameterException if param is an
* invalid parameter for this engine, or another exception occurs while
* trying to get this parameter.
*
* @deprecated Deprecated.
*/
@Deprecated
// Android changed add "Deprecated."
protected abstract Object engineGetParameter(String param)
throws InvalidParameterException;
/**
* Returns a clone if the implementation is cloneable.
*
* @return a clone if the implementation is cloneable.
*
* @exception CloneNotSupportedException if this is called
* on an implementation that does not support Cloneable.
*/
public Object clone() throws CloneNotSupportedException {
if (this instanceof Cloneable) {
return super.clone();
} else {
throw new CloneNotSupportedException();
}
}
}