/* SignatureSpi.java --- Signature Service Provider Interface
   Copyright (C) 1999, 2003, Free Software Foundation, Inc.

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package java.security;

import java.security.spec.AlgorithmParameterSpec;

/**
 * <p>This class defines the <i>Service Provider Interface (SPI)</i> for the
 * {@link 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>
 *
 * <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 Mark Benvenuto (ivymccough@worldnet.att.net)
 * @since 1.2
 * @see Signature
 */
public abstract class SignatureSpi
{
  /** Application-specified source of randomness. */
  protected SecureRandom appRandom;

  public SignatureSpi()
  {
    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.
   * @throws 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.
   * @throws InvalidKeyException if the key is improperly encoded, parameters
   * are missing, and so on.
   */
  protected abstract void engineInitSign(PrivateKey privateKey)
    throws InvalidKeyException;

  /**
   * <p>Initializes this signature object with the specified private key and
   * source of randomness for signing operations.</p>
   *
   * <p>This concrete method has been added to this previously-defined abstract
   * class. (For backwards compatibility, it cannot be abstract.)</p>
   *
   * @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.
   * @since 1.2
   */
  protected void engineInitSign(PrivateKey privateKey, SecureRandom random)
    throws InvalidKeyException
  {
    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.
   * @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;

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

  /**
   * <p>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>
   *
   * <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.</p>
   *
   * @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 <b>GNU</b> provider do not return
   * partial digests. If the value of this parameter is less than the actual
   * signature length, this method will throw a {@link 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>.
   * @throws SignatureException if an error occurs or len is less than the
   * actual signature length.
   * @since 1.2
   */
  protected int engineSign(byte[] outbuf, int offset, int len)
    throws SignatureException
  {
    byte[] tmp = engineSign();
    if (tmp.length > len)
      throw new SignatureException("Invalid Length");

    System.arraycopy(outbuf, offset, tmp, 0, tmp.length);
    return tmp.length;
  }

  /**
   * Verifies the passed-in signature.
   *
   * @param sigBytes the signature bytes to be verified.
   * @return <code>true</code> if the signature was verified, <code>false</code>
   * if not.
   * @throws 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;

  /**
   * <p>Verifies the passed-in <code>signature</code> in the specified array of
   * bytes, starting at the specified <code>offset</code>.</p>
   *
   * <p>Note: Subclasses should overwrite the default implementation.</p>
   *
   * @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</code> if the signature was verified, <code>false</code>
   * if not.
   * @throws SignatureException if the engine is not initialized properly, or
   * the passed-in <code>signature</code> is improperly encoded or of the wrong
   * type, etc.
   */
  protected boolean engineVerify(byte[] sigBytes, int offset, int length)
    throws SignatureException
  {
    byte[] tmp = new byte[length];
    System.arraycopy(sigBytes, offset, tmp, 0, length);
    return engineVerify(tmp);
  }

  /**
   * 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.
   * @throws 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 engineSetParameter(AlgorithmParameterSpec).
   */
  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.
   * @throws UnsupportedOperationException if this method is not overridden by
   * a provider.
   * @throws 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 <code>null</code> if this signature engine
   * does not use any parameters.</p>
   *
   * <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.</p>
   *
   * @return the parameters used with this signature engine, or <code>null</code>
   * if this signature engine does not use any parameters.
   * @throws 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 <code>null</code>
   * if there is none.
   * @throws 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.
   * @throws CloneNotSupportedException if this is called on an implementation
   * that does not support {@link Cloneable}.
   * @see Cloneable
   */
  public Object clone() throws CloneNotSupportedException
  {
    return super.clone();
  }
}