/* ServerMechanism.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a 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
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 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
conditions of the GNU General Public License cover the whole
combination.

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
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
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exception statement from your version.  */


package gnu.javax.crypto.sasl;

import gnu.java.security.Registry;

import java.util.HashMap;
import java.util.Map;

import javax.security.auth.callback.CallbackHandler;
import javax.security.sasl.Sasl;
import javax.security.sasl.SaslException;
import javax.security.sasl.SaslServer;

/**
 * A base class to facilitate implementing SASL server-side mechanisms.
 */
public abstract class ServerMechanism
    implements SaslServer
{
  /** Name of this mechanism. */
  protected String mechanism;
  /** Name of protocol using this mechanism. */
  protected String protocol;
  /** Name of server to authenticate to. */
  protected String serverName;
  /** Properties of qualities desired for this mechanism. */
  protected Map properties;
  /** Callback handler to use with this mechanism instance. */
  protected CallbackHandler handler;
  /** Whether authentication phase is completed (true) or not (false). */
  protected boolean complete = false;
  /** The authorisation identity. */
  protected String authorizationID;
  /** Channel binding data to use with this mechanism instance. */
  protected byte[] channelBinding;
  /** The state of the authentication automaton. -1 means uninitialised. */
  protected int state = -1;
  /** The provider for authentication information. */
  protected IAuthInfoProvider authenticator;

  protected ServerMechanism(final String mechanism)
  {
    super();

    this.mechanism = mechanism;
    this.authenticator = AuthInfo.getProvider(mechanism);
    this.state = -1;
  }

  protected abstract void initMechanism() throws SaslException;

  protected abstract void resetMechanism() throws SaslException;

  public abstract byte[] evaluateResponse(byte[] response) throws SaslException;

  public boolean isComplete()
  {
    return complete;
  }

  public byte[] unwrap(final byte[] incoming, final int offset, final int len)
      throws SaslException
  {
    if (! isComplete())
      throw new IllegalMechanismStateException();
    return this.engineUnwrap(incoming, offset, len);
  }

  public byte[] wrap(final byte[] outgoing, final int offset, final int len)
      throws SaslException
  {
    if (! isComplete())
      throw new IllegalMechanismStateException();
    return this.engineWrap(outgoing, offset, len);
  }

  public String getMechanismName()
  {
    return this.mechanism;
  }

  public String getAuthorizationID()
  {
    return this.authorizationID;
  }

  public Object getNegotiatedProperty(final String propName)
  {
    if (! isComplete())
      throw new IllegalStateException();
    if (Sasl.QOP.equals(propName))
      return getNegotiatedQOP();
    if (Sasl.STRENGTH.equals(propName))
      return getNegotiatedStrength();
    if (Sasl.SERVER_AUTH.equals(propName))
      return getNegotiatedServerAuth();
    if (Sasl.MAX_BUFFER.equals(propName))
      return getNegotiatedMaxBuffer();
    if (Sasl.RAW_SEND_SIZE.equals(propName))
      return getNegotiatedRawSendSize();
    if (Sasl.POLICY_NOPLAINTEXT.equals(propName))
      return getNegotiatedPolicyNoPlainText();
    if (Sasl.POLICY_NOACTIVE.equals(propName))
      return getNegotiatedPolicyNoActive();
    if (Sasl.POLICY_NODICTIONARY.equals(propName))
      return getNegotiatedPolicyNoDictionary();
    if (Sasl.POLICY_NOANONYMOUS.equals(propName))
      return getNegotiatedPolicyNoAnonymous();
    if (Sasl.POLICY_FORWARD_SECRECY.equals(propName))
      return getNegotiatedPolicyForwardSecrecy();
    if (Sasl.POLICY_PASS_CREDENTIALS.equals(propName))
      return getNegotiatedPolicyPassCredentials();
    if (Sasl.REUSE.equals(propName))
      return getReuse();
    return null;
  }

  public void dispose() throws SaslException
  {
    reset();
  }

  protected String getNegotiatedQOP()
  {
    return Registry.QOP_AUTH;
  }

  protected String getNegotiatedStrength()
  {
    return Registry.STRENGTH_LOW;
  }

  protected String getNegotiatedServerAuth()
  {
    return Registry.SERVER_AUTH_FALSE;
  }

  protected String getNegotiatedMaxBuffer()
  {
    return null;
  }

  protected String getNegotiatedPolicyNoPlainText()
  {
    return null;
  }

  protected String getNegotiatedPolicyNoActive()
  {
    return null;
  }

  protected String getNegotiatedPolicyNoDictionary()
  {
    return null;
  }

  protected String getNegotiatedPolicyNoAnonymous()
  {
    return null;
  }

  protected String getNegotiatedPolicyForwardSecrecy()
  {
    return null;
  }

  protected String getNegotiatedPolicyPassCredentials()
  {
    return null;
  }

  protected String getNegotiatedRawSendSize()
  {
    return String.valueOf(Registry.SASL_BUFFER_MAX_LIMIT);
  }

  protected String getReuse()
  {
    return Registry.REUSE_FALSE;
  }

  protected byte[] engineUnwrap(final byte[] incoming, final int offset,
                                final int len) throws SaslException
  {
    final byte[] result = new byte[len];
    System.arraycopy(incoming, offset, result, 0, len);
    return result;
  }

  protected byte[] engineWrap(final byte[] outgoing, final int offset,
                              final int len) throws SaslException
  {
    final byte[] result = new byte[len];
    System.arraycopy(outgoing, offset, result, 0, len);
    return result;
  }

  /**
   * Initialises the mechanism with designated attributes. Permissible names and
   * values are mechanism specific.
   * 
   * @param attributes a set of name-value pairs that describes the desired
   *          future behaviour of this instance.
   * @throws IllegalMechanismStateException if the instance is already
   *           initialised.
   * @throws SaslException if an exception occurs during the process.
   */
  public void init(final Map attributes) throws SaslException
  {
    if (state != -1)
      throw new IllegalMechanismStateException("init()");
    if (properties == null)
      properties = new HashMap();
    else
      properties.clear();
    if (attributes != null)
      {
        protocol = (String) attributes.get(Registry.SASL_PROTOCOL);
        serverName = (String) attributes.get(Registry.SASL_SERVER_NAME);
        handler = (CallbackHandler) attributes.get(Registry.SASL_CALLBACK_HANDLER);
        channelBinding = (byte[]) attributes.get(Registry.SASL_CHANNEL_BINDING);
        properties.putAll(attributes);
      }
    else
      handler = null;
    if (protocol == null)
      protocol = "";
    if (serverName == null)
      serverName = "";
    if (authenticator != null)
      authenticator.activate(properties);
    if (channelBinding == null)
      channelBinding = new byte[0];
    initMechanism();
    complete = false;
    state = 0;
  }

  /**
   * Resets the mechanism instance for re-initialisation and use with other
   * characteristics.
   * 
   * @throws SaslException if an exception occurs during the process.
   */
  public void reset() throws SaslException
  {
    resetMechanism();
    properties.clear();
    if (authenticator != null)
      authenticator.passivate();
    protocol = serverName = null;
    channelBinding = null;
    complete = false;
    state = -1;
  }
}