/* CramMD5Server.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
along with GNU Classpath; if not, write to the Free Software
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
module.  An independent module is a module which is not derived from
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
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version.  */


package gnu.javax.crypto.sasl.crammd5;

import gnu.java.security.Registry;
import gnu.java.security.util.Util;
import gnu.javax.crypto.sasl.NoSuchUserException;
import gnu.javax.crypto.sasl.ServerMechanism;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import javax.security.sasl.AuthenticationException;
import javax.security.sasl.SaslException;
import javax.security.sasl.SaslServer;

/**
 * The CRAM-MD5 SASL server-side mechanism.
 */
public class CramMD5Server
    extends ServerMechanism
    implements SaslServer
{
  private byte[] msgID;

  public CramMD5Server()
  {
    super(Registry.SASL_CRAM_MD5_MECHANISM);
  }

  protected void initMechanism() throws SaslException
  {
  }

  protected void resetMechanism() throws SaslException
  {
  }

  public byte[] evaluateResponse(final byte[] response) throws SaslException
  {
    if (state == 0)
      {
        msgID = CramMD5Util.createMsgID();
        state++;
        return msgID;
      }
    final String responseStr = new String(response);
    final int index = responseStr.lastIndexOf(" ");
    final String username = responseStr.substring(0, index);
    final byte[] responseDigest;
    try
      {
        responseDigest = responseStr.substring(index + 1).getBytes("UTF-8");
      }
    catch (UnsupportedEncodingException x)
      {
        throw new AuthenticationException("evaluateResponse()", x);
      }
    // Look up the password
    final char[] password = lookupPassword(username);
    // Compute the digest
    byte[] digest;
    try
      {
        digest = CramMD5Util.createHMac(password, msgID);
      }
    catch (InvalidKeyException x)
      {
        throw new AuthenticationException("evaluateResponse()", x);
      }
    try
      {
        digest = Util.toString(digest).toLowerCase().getBytes("UTF-8");
      }
    catch (UnsupportedEncodingException x)
      {
        throw new AuthenticationException("evaluateResponse()", x);
      }
    // Compare the received and computed digests
    if (! Arrays.equals(digest, responseDigest))
      throw new AuthenticationException("Digest mismatch");
    state++;
    return null;
  }

  public boolean isComplete()
  {
    return (state == 2);
  }

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

  private char[] lookupPassword(final String userName) throws SaslException
  {
    try
      {
        if (! authenticator.contains(userName))
          throw new NoSuchUserException(userName);
        final Map userID = new HashMap();
        userID.put(Registry.SASL_USERNAME, userName);
        final Map credentials = authenticator.lookup(userID);
        final String password = (String) credentials.get(Registry.SASL_PASSWORD);
        if (password == null)
          throw new AuthenticationException("lookupPassword()",
                                            new InternalError());
        return password.toCharArray();
      }
    catch (IOException x)
      {
        if (x instanceof SaslException)
          throw (SaslException) x;
        throw new AuthenticationException("lookupPassword()", x);
      }
  }
}