/* PBEKeySpec.java -- Wrapper for password-based keys.
   Copyright (C) 2004, 2006  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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General Public License for more details.

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02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
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package javax.crypto.spec;

import java.security.spec.KeySpec;

/**
 * A wrapper for a password-based key, used for password-based
 * encryption (PBE).
 *
 * <p>Examples of password-based encryption algorithms include:
 *
 * <ul>
 * <li><a href="http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/">PKCS #5
 * - Password-Based Cryptography Standard</a></li>
 * <li><a href="http://www.rsasecurity.com/rsalabs/pkcs/pkcs-12/">PKCS
 * #12 - Personal Information Exchange Syntax Standard</a></li>
 * </ul>
 *
 * @author Casey Marshall (csm@gnu.org)
 * @since 1.4
 * @see javax.crypto.SecretKeyFactory
 * @see PBEParameterSpec
 */
public class PBEKeySpec implements KeySpec
{

  // Fields.
  // ------------------------------------------------------------------------

  /** The iteration count. */
  private int iterationCount;

  /** The generated key length. */
  private int keyLength;

  /** The password. */
  private char[] password;

  /** The salt. */
  private byte[] salt;

  /** The password state */
  private boolean passwordValid = true;

  // Constructors.
  // ------------------------------------------------------------------------

  /**
   * Create a new PBE key spec with just a password.
   * <p>
   * A copy of the password argument is stored instead of the argument itself.
   *
   * @param password The password char array.
   */
  public PBEKeySpec(char[] password)
  {
    setPassword(password);

    // load the default values for unspecified variables.
    salt = null;
    iterationCount = 0;
    keyLength = 0;
  }

  /**
   * Create a PBE key spec with a password, salt, and iteration count.
   * <p>
   * A copy of the password and salt arguments are stored instead of the
   * arguments themselves.
   *
   * @param password The password char array.
   * @param salt The salt bytes.
   * @param iterationCount The iteration count.
   * @throws NullPointerException If salt is null
   * @throws IllegalArgumentException If salt is an empty array, or
   *           iterationCount is negative
   */
  public PBEKeySpec(char[] password, byte[] salt, int iterationCount)
  {
    setPassword(password);
    setSalt(salt);
    setIterationCount(iterationCount);

    // load default values into unspecified variables.
    keyLength = 0;
  }

  /**
   * Create a PBE key spec with a password, salt, iteration count, and key
   * length.
   * <p>
   * A copy of the password and salt arguments are stored instead of the
   * arguments themselves.
   *
   * @param password The password char array.
   * @param salt The salt bytes.
   * @param iterationCount The iteration count.
   * @param keyLength The generated key length.
   * @throws NullPointerException If salt is null
   * @throws IllegalArgumentException If salt is an empty array, if
   *           iterationCount or keyLength is negative
   */
  public PBEKeySpec(char[] password, byte[] salt, int iterationCount,
                    int keyLength)
  {
    setPassword(password);
    setSalt(salt);
    setIterationCount(iterationCount);
    setKeyLength(keyLength);
  }

  // Instance methods.
  // ------------------------------------------------------------------------

  /**
   * Clear the password array by filling it with null characters.
   * <p>
   * This clears the stored copy of the password, not the original char array
   * used to create the password.
   */
  public final void clearPassword()
  {
    if (password == null)
      return;
    for (int i = 0; i < password.length; i++)
      password[i] = '\u0000';

    // since the password is cleared, it is no longer valid
    passwordValid = false;
  }

  /**
   * Get the iteration count, or 0 if it has not been specified.
   *
   * @return The iteration count, or 0 if it has not been specified.
   */
  public final int getIterationCount()
  {
    return iterationCount;
  }

  /**
   * Get the generated key length, or 0 if it has not been specified.
   *
   * @return The key length, or 0 if it has not been specified.
   */
  public final int getKeyLength()
  {
    return keyLength;
  }

  /**
   * Get the password character array copy.
   * <p>
   * This returns a copy of the password, not the password itself.
   *
   * @return a clone of the password.
   * @throws IllegalStateException If {@link #clearPassword()} has already been
   *           called.
   */
  public final char[] getPassword()
  {
    if (! passwordValid)
      throw new IllegalStateException("clearPassword() has been called, the "
                                      + "password is no longer valid");
    return (char[]) password.clone();
  }

  /**
   * Get the salt bytes array copy.
   * <p>
   * This returns a copy of the salt, not the salt itself.
   *
   * @return The salt.
   */
  public final byte[] getSalt()
  {
    if (salt != null)
      return (byte[]) salt.clone();
    return null;
  }

  /**
   * Set the password char array.
   * <p>
   * A copy of the password argument is stored instead of the argument itself.
   *
   * @param password The password to be set
   */
  private void setPassword(char[] password)
  {
    if (password != null)
      this.password = (char[]) password.clone();
    else
      this.password = new char[0];

    passwordValid = true;
  }

  /**
   * Set the salt byte array.
   * <p>
   * A copy of the salt arguments is stored instead of the argument itself.
   *
   * @param salt The salt to be set.
   * @throws NullPointerException If the salt is null.
   * @throws IllegalArgumentException If the salt is an empty array.
   */
  private void setSalt(byte[] salt)
  {
    if (salt.length == 0)
      throw new IllegalArgumentException("salt MUST NOT be an empty byte array");

    this.salt = (byte[]) salt.clone();
  }

  /**
   * Set the iterationCount.
   *
   * @param iterationCount The iteration count to be set.
   * @throws IllegalArgumentException If the iterationCount is negative.
   */
  private void setIterationCount(int iterationCount)
  {
    if (iterationCount < 0)
      throw new IllegalArgumentException("iterationCount MUST be positive");

    this.iterationCount = iterationCount;
  }

  /**
   * Set the keyLength.
   *
   * @param keyLength The keyLength to be set.
   * @throws IllegalArgumentException if the keyLength is negative.
   */
  private void setKeyLength(int keyLength)
  {
    if (keyLength < 0)
      throw new IllegalArgumentException("keyLength MUST be positive");

    this.keyLength = keyLength;
  }
}