/*
    *  Licensed to the Apache Software Foundation (ASF) under one
    *  or more contributor license agreements.  See the NOTICE file
    *  distributed with this work for additional information
    *  regarding copyright ownership.  The ASF licenses this file
    *  to you under the Apache License, Version 2.0 (the
    *  "License"); you may not use this file except in compliance
    *  with the License.  You may obtain a copy of the License at
    *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
   *  software distributed under the License is distributed on an
   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   *  KIND, either express or implied.  See the License for the
   *  specific language governing permissions and limitations
   *  under the License.
   *
   */
  package org.apache.directory.server.ldap.handlers.sasl.gssapi;
  
  
  import java.security.PrivilegedExceptionAction;
  import java.util.HashMap;
  import java.util.Map;
  
  import javax.security.auth.Subject;
  import javax.security.auth.callback.CallbackHandler;
  import javax.security.auth.kerberos.KerberosKey;
  import javax.security.auth.kerberos.KerberosPrincipal;
  import javax.security.sasl.Sasl;
  import javax.security.sasl.SaslServer;
  
  import org.apache.directory.api.ldap.model.constants.SupportedSaslMechanisms;
  import org.apache.directory.api.ldap.model.message.BindRequest;
  import org.apache.directory.api.ldap.model.name.Dn;
  import org.apache.directory.server.core.api.CoreSession;
  import org.apache.directory.server.i18n.I18n;
  import org.apache.directory.server.kerberos.shared.store.PrincipalStoreEntry;
  import org.apache.directory.server.protocol.shared.kerberos.GetPrincipal;
  import org.apache.directory.server.ldap.LdapServer;
  import org.apache.directory.server.ldap.LdapSession;
  import org.apache.directory.server.ldap.handlers.sasl.AbstractMechanismHandler;
  import org.apache.directory.server.ldap.handlers.sasl.SaslConstants;
  import org.apache.directory.server.protocol.shared.ServiceConfigurationException;
  import org.apache.directory.shared.kerberos.codec.types.EncryptionType;
  import org.apache.directory.shared.kerberos.components.EncryptionKey;
  
  
  /**
   * The GSSAPI Sasl mechanism handler.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public class GssapiMechanismHandler extends AbstractMechanismHandler
  {
      public SaslServer handleMechanism( LdapSession ldapSession, BindRequest bindRequest ) throws Exception
      {
          SaslServer ss = ( SaslServer ) ldapSession.getSaslProperty( SaslConstants.SASL_SERVER );
  
          if ( ss == null )
          {
              Subject subject = getSubject( ldapSession.getLdapServer() );
              final String saslHost = ( String ) ldapSession.getSaslProperty( SaslConstants.SASL_HOST );
              final Map<String, String> saslProps = ( Map<String, String> ) ldapSession
                  .getSaslProperty( SaslConstants.SASL_PROPS );
  
              CoreSession adminSession = ldapSession.getLdapServer().getDirectoryService().getAdminSession();
  
              final CallbackHandler callbackHandler = new GssapiCallbackHandler( ldapSession, adminSession, bindRequest );
  
              ss = Subject.doAs( subject, new PrivilegedExceptionAction<SaslServer>()
              {
                  public SaslServer run() throws Exception
                  {
                      return Sasl.createSaslServer( SupportedSaslMechanisms.GSSAPI, SaslConstants.LDAP_PROTOCOL,
                          saslHost, saslProps, callbackHandler );
                  }
              } );
  
              ldapSession.putSaslProperty( SaslConstants.SASL_SERVER, ss );
          }
  
          return ss;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public void init( LdapSession ldapSession )
      {
          // Store the host in the ldap session
          String saslHost = ldapSession.getLdapServer().getSaslHost();
          ldapSession.putSaslProperty( SaslConstants.SASL_HOST, saslHost );
  
          Map<String, String> saslProps = new HashMap<>();
          saslProps.put( Sasl.QOP, ldapSession.getLdapServer().getSaslQopString() );
          ldapSession.putSaslProperty( SaslConstants.SASL_PROPS, saslProps );
     }
 
 
     /**
      * Remove the Host, UserBaseDn, props and Mechanism property.
      * 
      * @param ldapSession the Ldapsession instance
      */
     public void cleanup( LdapSession ldapSession )
     {
         // Inject the Sasl Filter
         insertSaslFilter( ldapSession );
 
         // and remove the useless informations
         ldapSession.removeSaslProperty( SaslConstants.SASL_HOST );
         ldapSession.removeSaslProperty( SaslConstants.SASL_USER_BASE_DN );
         ldapSession.removeSaslProperty( SaslConstants.SASL_MECH );
         ldapSession.removeSaslProperty( SaslConstants.SASL_PROPS );
         ldapSession.removeSaslProperty( SaslConstants.SASL_AUTHENT_USER );
     }
 
 
     private Subject getSubject( LdapServer ldapServer ) throws Exception
     {
         String servicePrincipalName = ldapServer.getSaslPrincipal();
         KerberosPrincipal servicePrincipal = new KerberosPrincipal( servicePrincipalName );
         GetPrincipalprotocol/shared/kerberos/GetPrincipal.html#GetPrincipal">GetPrincipal getPrincipal = new GetPrincipal( servicePrincipal );
 
         PrincipalStoreEntry entry = null;
 
         try
         {
             entry = findPrincipal( ldapServer, getPrincipal );
         }
         catch ( ServiceConfigurationException sce )
         {
             String message = I18n.err( I18n.ERR_659, servicePrincipalName, ldapServer.getSearchBaseDn() );
             throw new ServiceConfigurationException( message, sce );
         }
 
         if ( entry == null )
         {
             String message = I18n.err( I18n.ERR_659, servicePrincipalName, ldapServer.getSearchBaseDn() );
             throw new ServiceConfigurationException( message );
         }
 
         Subject subject = new Subject();
 
         for ( EncryptionType encryptionType : entry.getKeyMap().keySet() )
         {
             EncryptionKey key = entry.getKeyMap().get( encryptionType );
 
             byte[] keyBytes = key.getKeyValue();
             int type = key.getKeyType().getValue();
             int kvno = key.getKeyVersion();
 
             KerberosKey serviceKey = new KerberosKey( servicePrincipal, keyBytes, type, kvno );
 
             subject.getPrivateCredentials().add( serviceKey );
         }
 
         return subject;
     }
 
 
     private PrincipalStoreEntry findPrincipal( LdapServer ldapServer, GetPrincipal getPrincipal ) throws Exception
     {
         CoreSession adminSession = ldapServer.getDirectoryService().getAdminSession();
         return ( PrincipalStoreEntry ) getPrincipal.execute( adminSession, new Dn( ldapServer.getSearchBaseDn() ) );
     }
 }