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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package java.security;

import sun.security.jca.JCAUtil;

import java.nio.ByteBuffer;
import java.security.spec.AlgorithmParameterSpec;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the {@code 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.
 *
 * <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
 * @since 1.2
 *
 *
 * @see Signature
 */

public abstract class SignatureSpi {

    /**
     * Constructor for subclasses to call.
     */
    public SignatureSpi() {}

    /**
     * Application-specified source of randomness.
     */
    protected SecureRandom appRandom = null;

    /**
     * Initializes this {@code 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.
     *
     * @throws    InvalidKeyException if the key is improperly
     * encoded, parameters are missing, and so on.
     */
    protected abstract void engineInitVerify(PublicKey publicKey)
        throws InvalidKeyException;

    /**
     * Initializes this {@code 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.
     * @param params the parameters for verifying this {@code Signature} object
     *
     * @throws    InvalidKeyException if the key is improperly
     * encoded, does not work with the given parameters, and so on.
     * @throws    InvalidAlgorithmParameterException if the given parameters
     * is invalid.
     */
    void engineInitVerify(PublicKey publicKey,
            AlgorithmParameterSpec params)
            throws InvalidKeyException, InvalidAlgorithmParameterException {
        if (params != null) {
            try {
                engineSetParameter(params);
            } catch (UnsupportedOperationException usoe) {
                // error out if not overridden
                throw new InvalidAlgorithmParameterException(usoe);
            }
        }
        engineInitVerify(publicKey);
    }

    /**
     * Initializes this {@code Signature} object with the specified
     * private key for signing operations.
     *
     * @param privateKey the private key of the identity whose signature
     * will be generated.
     *
     * @throws    InvalidKeyException if the key is improperly
     * encoded, parameters are missing, and so on.
     */
    protected abstract void engineInitSign(PrivateKey privateKey)
        throws InvalidKeyException;

    /**
     * Initializes this {@code 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
     *
     * @throws    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);
    }

    /**
     * Initializes this {@code 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 params the parameters for generating signature
     * @param random the source of randomness
     *
     * @throws    InvalidKeyException if the key is improperly
     * encoded, parameters are missing, and so on.
     * @throws    InvalidAlgorithmParameterException if the parameters is
     * invalid.
     */
    void engineInitSign(PrivateKey privateKey,
            AlgorithmParameterSpec params, SecureRandom random)
            throws InvalidKeyException, InvalidAlgorithmParameterException {
        if (params != null) {
            try {
                engineSetParameter(params);
            } catch (UnsupportedOperationException usoe) {
                // error out if not overridden
                throw new InvalidAlgorithmParameterException(usoe);
            }
        }
        engineInitSign(privateKey, random);
    }

    /**
     * Updates the data to be signed or verified
     * using the specified byte.
     *
     * @param b the byte to use for the update.
     *
     * @throws    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
     *
     * @throws    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 {@code data.remaining()} bytes
     * starting at {@code 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()) {
            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.
     *
     * @throws    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 {@code outbuf}, starting at
     * {@code offset}.
     * 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} 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} where the signature is
     * stored.
     *
     * @param len number of bytes within {@code 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
     * {@code 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}
     *
     * @throws    SignatureException if the engine is not
     * initialized properly, if this signature algorithm is unable to
     * process the input data provided, or if {@code 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 {@code true} if the signature was verified, {@code false} if not.
     *
     * @throws    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.
     *
     * <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 {@code true} if the signature was verified, {@code false} if not.
     *
     * @throws    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 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.
     *
     * @throws    InvalidParameterException if {@code param} is an
     * invalid parameter for this {@code Signature} object,
     * 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;

    /**
     * Initializes this {@code Signature} object with the specified parameter
     * values.
     *
     * @param params the parameters
     *
     * @throws    UnsupportedOperationException if this method is not
     * overridden by a provider
     *
     * @throws    InvalidAlgorithmParameterException if this method is
     * overridden by a provider and the given parameters
     * are inappropriate for this {@code Signature} object
     */
    protected void engineSetParameter(AlgorithmParameterSpec params)
            throws InvalidAlgorithmParameterException {
        throw new UnsupportedOperationException();
    }

    /**
     * Returns the parameters used with this {@code Signature} object.
     *
     * <p>The returned parameters may be the same that were used to initialize
     * this {@code Signature} object, or may contain additional default or
     * random parameter values used by the underlying signature scheme.
     * If the required parameters were not supplied and can be generated by
     * the {@code Signature} object, the generated parameters are returned;
     * otherwise {@code null} is returned.
     *
     * <p>However, if the signature scheme does not support returning
     * the parameters as {@code AlgorithmParameters}, {@code null} is always
     * returned.
     *
     * @return the parameters used with this {@code Signature} object, or
     * {@code null}
     *
     * @throws 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 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 {@code null}
     * if there is none.
     *
     * @throws    InvalidParameterException if {@code param} is an
     * invalid parameter for this engine, or another exception occurs while
     * trying to get this parameter.
     *
     * @deprecated
     */
    @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.
     *
     * @throws    CloneNotSupportedException if this is called
     * on an implementation that does not support {@code Cloneable}.
     */
    public Object clone() throws CloneNotSupportedException {
        if (this instanceof Cloneable) {
            return super.clone();
        } else {
            throw new CloneNotSupportedException();
        }
    }
}