/*
 * @(#)SignatureSpi.java	1.20 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
  
package java.security;

import java.security.spec.AlgorithmParameterSpec;
import java.util.*;
import java.io.*;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the <code>Signature</code> 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.
 *.
 * <p> 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 
 *
 * @version 1.20, 01/23/03
 *
 * @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.
     *
     * <p>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;

    /** 
     * 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.  
     */
    protected abstract byte[] engineSign() throws SignatureException;

    /**
     * Finishes this signature operation and stores the resulting signature
     * bytes in the provided buffer <code>outbuf</code>, starting at
     * <code>offset</code>.
     * The format of the signature depends on the underlying 
     * signature scheme.
     * 
     * <p>The signature implementation is reset to its initial state
     * (the state it was in after a call to one of the
     * <code>engineInitSign</code> 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 <code>outbuf</code> where the signature is
     * stored.
     *
     * @param len number of bytes within <code>outbuf</code> 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 <code>outbuf</code>
     * 
     * @exception SignatureException if an error occurs or <code>len</code>
     * 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, or the passed-in signature is improperly encoded or 
     * of the wrong type, 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.
     *
     * <p> 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, or the passed-in signature is improperly encoded or 
     * of the wrong type, etc.  
     */
    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 <code>param</code> 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}.
     */
    protected abstract void engineSetParameter(String param, Object value) 
	throws InvalidParameterException;

    /**
     * <p>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 the given parameters
     * are inappropriate for this signature engine
     */
    protected void engineSetParameter(AlgorithmParameterSpec params)
	throws InvalidAlgorithmParameterException {
	    throw new UnsupportedOperationException();
    }

    /**
     * <p>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.
     *
     * <p>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
     */
    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 <code>param</code> is an 
     * invalid parameter for this engine, or another exception occurs while
     * trying to get this parameter.
     *
     * @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 <code>Cloneable</code>.
     */
    public Object clone() throws CloneNotSupportedException {
	if (this instanceof Cloneable) {
	    return super.clone();
	} else {
	    throw new CloneNotSupportedException();
	}
    }
}