/*
    *  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.plain;
  
  
  import java.io.IOException;
  
  import javax.naming.InvalidNameException;
  import javax.security.sasl.SaslException;
  
  import org.apache.directory.api.ldap.model.constants.SchemaConstants;
  import org.apache.directory.api.ldap.model.constants.SupportedSaslMechanisms;
  import org.apache.directory.api.ldap.model.entry.Entry;
  import org.apache.directory.api.ldap.model.entry.Value;
  import org.apache.directory.api.ldap.model.exception.LdapAuthenticationException;
  import org.apache.directory.api.ldap.model.filter.EqualityNode;
  import org.apache.directory.api.ldap.model.message.BindRequest;
  import org.apache.directory.api.ldap.model.message.SearchScope;
  import org.apache.directory.api.ldap.model.schema.PrepareString;
  import org.apache.directory.api.util.Strings;
  import org.apache.directory.server.core.api.CoreSession;
  import org.apache.directory.server.core.api.DirectoryService;
  import org.apache.directory.server.core.api.OperationEnum;
  import org.apache.directory.server.core.api.OperationManager;
  import org.apache.directory.server.core.api.filtering.EntryFilteringCursor;
  import org.apache.directory.server.core.api.interceptor.context.BindOperationContext;
  import org.apache.directory.server.core.api.interceptor.context.SearchOperationContext;
  import org.apache.directory.server.i18n.I18n;
  import org.apache.directory.server.ldap.LdapServer;
  import org.apache.directory.server.ldap.LdapSession;
  import org.apache.directory.server.ldap.handlers.sasl.AbstractSaslServer;
  
  
  /**
   * A SaslServer implementation for PLAIN based SASL mechanism.  This is
   * required unfortunately because the JDK's SASL provider does not support
   * this mechanism.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  public final class PlainSaslServer extends AbstractSaslServer
  {
      /** The authzid property stored into the LdapSession instance */
      public static final String SASL_PLAIN_AUTHZID = "authzid";
  
      /** The authcid property stored into the LdapSession instance */
      public static final String SASL_PLAIN_AUTHCID = "authcid";
  
      /** The password property stored into the LdapSession instance */
      public static final String SASL_PLAIN_PASSWORD = "password";
  
      /**
       * The possible states for the negotiation of a PLAIN mechanism. 
       */
      private enum NegotiationState
      {
          INITIALIZED, // Negotiation has just started 
          MECH_RECEIVED, // We have received the PLAIN mechanism
          COMPLETED // The user/password have been received
      }
  
      /**
       * The different state used by the iInitialResponse decoding
       */
      private enum InitialResponse
      {
          AUTHZID_EXPECTED, // We are expecting a authzid element
          AUTHCID_EXPECTED, // We are expecting a authcid element 
          PASSWORD_EXPECTED // We are expecting a password element
      }
  
      /** The current negotiation state */
      private NegotiationState state;
  
      /**
       * 
       * Creates a new instance of PlainSaslServer.
       *
       * @param ldapSession The associated LdapSession instance
       * @param adminSession The Administrator session 
       * @param bindRequest The associated BindRequest object
       */
     public PlainSaslServer( LdapSession ldapSession, CoreSession adminSession, BindRequest bindRequest )
     {
         super( ldapSession, adminSession, bindRequest );
         state = NegotiationState.INITIALIZED;
 
         // Reinitialize the SASL properties
         getLdapSession().removeSaslProperty( SASL_PLAIN_AUTHZID );
         getLdapSession().removeSaslProperty( SASL_PLAIN_AUTHCID );
         getLdapSession().removeSaslProperty( SASL_PLAIN_PASSWORD );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public String getMechanismName()
     {
         return SupportedSaslMechanisms.PLAIN;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public byte[] evaluateResponse( byte[] initialResponse ) throws SaslException
     {
         if ( Strings.isEmpty( initialResponse ) )
         {
             state = NegotiationState.MECH_RECEIVED;
             return null;
         }
         else
         {
             // Split the credentials in three parts :
             // - the optional authzId
             // - the authId
             // - the password
             // The message should have this structure :
             // message   = [authzid] '0x00' authcid '0x00' passwd
             // authzid   = 1*SAFE ; MUST accept up to 255 octets
             // authcid   = 1*SAFE ; MUST accept up to 255 octets
             // passwd    = 1*SAFE ; MUST accept up to 255 octets
             InitialResponse element = InitialResponse.AUTHZID_EXPECTED;
             String authzId = null;
             String authcId = null;
             String password = null;
 
             int start = 0;
             int end = 0;
 
             try
             {
                 for ( byte b : initialResponse )
                 {
                     if ( b == '\0' )
                     {
                         if ( start - end == 0 )
                         {
                             // We don't have any value
                             if ( element == InitialResponse.AUTHZID_EXPECTED )
                             {
                                 // This is optional : do nothing, but change
                                 // the element type
                                 element = InitialResponse.AUTHCID_EXPECTED;
                             }
                             else
                             {
                                 // This not allowed
                                 throw new IllegalArgumentException( I18n.err( I18n.ERR_671 ) );
                             }
                         }
                         else
                         {
                             start++;
                             String value = new String( initialResponse, start, end - start + 1, "UTF-8" );
 
                             switch ( element )
                             {
                                 case AUTHZID_EXPECTED:
                                     element = InitialResponse.AUTHCID_EXPECTED;
                                     authzId = PrepareString.normalize( value );
                                     end++;
                                     start = end;
                                     break;
 
                                 case AUTHCID_EXPECTED:
                                     element = InitialResponse.PASSWORD_EXPECTED;
                                     authcId = PrepareString
                                         .normalize( value );
                                     end++;
                                     start = end;
                                     break;
 
                                 default:
                                     // This is an error !
                                     throw new IllegalArgumentException( I18n.err( I18n.ERR_672 ) );
                             }
                         }
                     }
                     else
                     {
                         end++;
                     }
                 }
 
                 if ( start == end )
                 {
                     throw new IllegalArgumentException( I18n.err( I18n.ERR_671 ) );
                 }
 
                 start++;
                 String value = Strings.utf8ToString( initialResponse, start, end - start + 1 );
 
                 password = PrepareString.normalize( value );
 
                 if ( ( authcId == null ) || ( password == null ) )
                 {
                     throw new IllegalArgumentException( I18n.err( I18n.ERR_671 ) );
                 }
 
                 // Now that we have the authcid and password, try to authenticate.
                 CoreSession userSession = authenticate( authcId, password );
 
                 getLdapSession().setCoreSession( userSession );
 
                 state = NegotiationState.COMPLETED;
             }
             catch ( IOException ioe )
             {
                 throw new IllegalArgumentException( I18n.err( I18n.ERR_674 ) );
             }
             catch ( InvalidNameException ine )
             {
                 throw new IllegalArgumentException( I18n.err( I18n.ERR_675 ) );
             }
             catch ( Exception e )
             {
                 throw new SaslException( I18n.err( I18n.ERR_676, authcId ) );
             }
         }
 
         return Strings.EMPTY_BYTES;
     }
 
 
     public boolean isComplete()
     {
         return state == NegotiationState.COMPLETED;
     }
 
 
     /**
      * Try to authenticate the user against the underlying LDAP server. The SASL PLAIN
      * authentication is based on the entry which uid is equal to the user name we received.
      */
     private CoreSession authenticate( String user, String password ) throws Exception
     {
         LdapSession ldapSession = getLdapSession();
         CoreSession adminSession = getAdminSession();
         DirectoryService directoryService = adminSession.getDirectoryService();
         LdapServer ldapServer = ldapSession.getLdapServer();
         OperationManager operationManager = directoryService.getOperationManager();
 
         // first, we have to find the entries which has the uid value
         EqualityNode<String> filter = new EqualityNode<>(
             directoryService.getSchemaManager().getAttributeType( SchemaConstants.UID_AT ), new Value( user ) );
 
         SearchOperationContextterceptor/context/SearchOperationContext.html#SearchOperationContext">SearchOperationContext searchContext = new SearchOperationContext( directoryService.getAdminSession() );
         searchContext.setDn( directoryService.getDnFactory().create( ldapServer.getSearchBaseDn() ) );
         searchContext.setScope( SearchScope.SUBTREE );
         searchContext.setFilter( filter );
         searchContext.setNoAttributes( true );
 
         EntryFilteringCursor cursor = operationManager.search( searchContext );
         Exception bindException = new LdapAuthenticationException( "Cannot authenticate user uid=" + user );
 
         while ( cursor.next() )
         {
             Entry entry = cursor.get();
 
             try
             {
                 BindOperationContexti/interceptor/context/BindOperationContext.html#BindOperationContext">BindOperationContext bindContext = new BindOperationContext( ldapSession.getCoreSession() );
                 bindContext.setDn( entry.getDn() );
                 bindContext.setCredentials( Strings.getBytesUtf8( password ) );
                 bindContext.setIoSession( ldapSession.getIoSession() );
                 bindContext.setInterceptors( directoryService.getInterceptors( OperationEnum.BIND ) );
 
                 operationManager.bind( bindContext );
 
                 cursor.close();
 
                 return bindContext.getSession();
             }
             catch ( Exception e )
             {
                 bindException = e;// Nothing to do here : we will try to bind with the next user
             }
         }
 
         cursor.close();
 
         throw bindException;
     }
 }