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    * 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   *
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   * 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.                                           *
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  package org.apache.james.smtpserver;
  
  import org.apache.avalon.framework.logger.AbstractLogEnabled;
  import org.apache.avalon.framework.configuration.Configuration;
  import org.apache.avalon.framework.configuration.Configurable;
  import org.apache.avalon.framework.configuration.ConfigurationException;
  import java.util.ArrayList;
  import java.util.StringTokenizer;
  
  /***
    * Connect handler for DNSRBL processing
    */
  public class DNSRBLHandler
      extends AbstractLogEnabled
      implements ConnectHandler, Configurable {
      /***
       * The lists of rbl servers to be checked to limit spam
       */
      private String[] whitelist;
      private String[] blacklist;
  
      /***
       * @see org.apache.avalon.framework.configuration.Configurable#configure(Configuration)
       */
      public void configure(Configuration handlerConfiguration) throws ConfigurationException {
  
          Configuration rblserverConfiguration = handlerConfiguration.getChild("rblservers", false);
          if ( rblserverConfiguration != null ) {
              ArrayList rblserverCollection = new ArrayList();
              Configuration[] children = rblserverConfiguration.getChildren("whitelist");
              if ( children != null ) {
                  for ( int i = 0 ; i < children.length ; i++ ) {
                      String rblServerName = children[i].getValue();
                      rblserverCollection.add(rblServerName);
                      if (getLogger().isInfoEnabled()) {
                          getLogger().info("Adding RBL server to whitelist: " + rblServerName);
                      }
                  }
                  if (rblserverCollection != null && rblserverCollection.size() > 0) {
                      whitelist = (String[]) rblserverCollection.toArray(new String[rblserverCollection.size()]);
                      rblserverCollection.clear();
                  }
              }
              children = rblserverConfiguration.getChildren("blacklist");
              if ( children != null ) {
                  for ( int i = 0 ; i < children.length ; i++ ) {
                      String rblServerName = children[i].getValue();
                      rblserverCollection.add(rblServerName);
                      if (getLogger().isInfoEnabled()) {
                          getLogger().info("Adding RBL server to blacklist: " + rblServerName);
                      }
                  }
                  if (rblserverCollection != null && rblserverCollection.size() > 0) {
                      blacklist = (String[]) rblserverCollection.toArray(new String[rblserverCollection.size()]);
                      rblserverCollection.clear();
                  }
              }
          }
  
      }
  
      /*
       * check if the remote Ip address is block listed
       *
       * @see org.apache.james.smtpserver.ConnectHandler#onConnect(SMTPSession)
      **/
      public void onConnect(SMTPSession session) {
          boolean blocklisted = checkDNSRBL(session, session.getRemoteIPAddress());
          session.setBlockListed(blocklisted);
      }
  
  
      /***
       * @see org.apache.james.smtpserver.SMTPHandlerConfigurationData#checkDNSRBL(Socket)
       */
      /*
       * This checks DNSRBL whitelists and blacklists.  If the remote IP is whitelisted
       * it will be permitted to send e-mail, otherwise if the remote IP is blacklisted,
       * the sender will only be permitted to send e-mail to postmaster (RFC 2821) or
       * abuse (RFC 2142), unless authenticated.
      */
 
     public boolean checkDNSRBL(SMTPSession session, String ipAddress) {
         
         /*
          * don't check against rbllists if the client is allowed to relay..
          * This whould make no sense.
          */
         if (session.isRelayingAllowed()) {
             getLogger().info("Ipaddress " + session.getRemoteIPAddress() + " is allowed to relay. Don't check it");
             return false;
         }
         
         if (whitelist != null || blacklist != null) {
             StringBuffer sb = new StringBuffer();
             StringTokenizer st = new StringTokenizer(ipAddress, " .", false);
             while (st.hasMoreTokens()) {
                 sb.insert(0, st.nextToken() + ".");
             }
             String reversedOctets = sb.toString();
 
             if (whitelist != null) {
                 String[] rblList = whitelist;
                 for (int i = 0 ; i < rblList.length ; i++) try {
                     java.net.InetAddress addr = org.apache.james.dnsserver.DNSServer.getByName(reversedOctets + rblList[i]);
                     if (getLogger().isInfoEnabled()) {
                         getLogger().info("Connection from " + ipAddress + " whitelisted by " + rblList[i]);
                     }
  
                     /* Ihis code may be helpful if admins need to debug why they are getting weird
                        behavior from the blocklists.  Also, it might help them to know what IP is
                        returned, since zones often use that to indicate interesting information.
 
                        The next version of this code already handles the associated TXT record,
                        so this code is just temporary for this release.
                      */
                     if (getLogger().isDebugEnabled()) {
                         getLogger().debug("Whitelist addr = " + addr.toString());
                     }
 
                     return false;
                 } catch (java.net.UnknownHostException uhe) {
                     if (getLogger().isDebugEnabled()) {
                         getLogger().debug("unknown host exception thrown:" + reversedOctets + rblList[i]);
                     }
                 }
             }
 
             if (blacklist != null) {
                 String[] rblList = blacklist;
                 for (int i = 0 ; i < rblList.length ; i++) try {
                     java.net.InetAddress addr = org.apache.james.dnsserver.DNSServer.getByName(reversedOctets + rblList[i]);
                     if (getLogger().isInfoEnabled()) {
                         getLogger().info("Connection from " + ipAddress + " restricted by " + rblList[i] + " to SMTP AUTH/postmaster/abuse.");
                     }
 
                     /* Ihis code may be helpful if admins need to debug why they are getting weird
                        behavior from the blocklists.  Also, it might help them to know what IP is
                        returned, since zones often use that to indicate interesting information.
 
                        The next version of this code already handles the associated TXT record,
                        so this code is just temporary for this release.
                      */
                     if (getLogger().isDebugEnabled()) {
                         getLogger().debug("Blacklist addr = " + addr.toString());
                     }
 
                     return true;
                 } catch (java.net.UnknownHostException uhe) {
                     // if it is unknown, it isn't blocked
                     if (getLogger().isDebugEnabled()) {
                         getLogger().debug("unknown host exception thrown:" + reversedOctets + rblList[i]);
                     }
                 }
             }
         }
         return false;
     }
 
 }