/**
    * 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.hadoop.hbase.rest.filter;
  
  import static org.apache.hadoop.hbase.rest.Constants.REST_AUTHENTICATION_PRINCIPAL;
  import static org.apache.hadoop.hbase.rest.Constants.REST_DNS_INTERFACE;
  import static org.apache.hadoop.hbase.rest.Constants.REST_DNS_NAMESERVER;
  
  import java.io.IOException;
  import java.util.Map;
  import java.util.Properties;
  
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HBaseConfiguration;
  import org.apache.hadoop.hbase.util.DNS;
  import org.apache.hadoop.hbase.util.Strings;
  import org.apache.hadoop.security.SecurityUtil;
  import org.apache.hadoop.security.authentication.server.AuthenticationFilter;
  
  public class AuthFilter extends AuthenticationFilter {
    private static final Log LOG = LogFactory.getLog(AuthFilter.class);
    private static final String REST_PREFIX = "hbase.rest.authentication.";
    private static final int REST_PREFIX_LEN = REST_PREFIX.length();
  
    /**
     * Returns the configuration to be used by the authentication filter
     * to initialize the authentication handler.
     *
     * This filter retrieves all HBase configurations and passes those started
     * with REST_PREFIX to the authentication handler.  It is useful to support
     * plugging different authentication handlers.
    */
    @Override
    protected Properties getConfiguration(
        String configPrefix, FilterConfig filterConfig) throws ServletException {
      Properties props = super.getConfiguration(configPrefix, filterConfig);
      //setting the cookie path to root '/' so it is used for all resources.
      props.setProperty(AuthenticationFilter.COOKIE_PATH, "/");
  
      Configuration conf = HBaseConfiguration.create();
      for (Map.Entry<String, String> entry : conf) {
        String name = entry.getKey();
        if (name.startsWith(REST_PREFIX)) {
          String value = entry.getValue();
          if(name.equals(REST_AUTHENTICATION_PRINCIPAL))  {
            try {
              String machineName = Strings.domainNamePointerToHostName(
                DNS.getDefaultHost(conf.get(REST_DNS_INTERFACE, "default"),
                  conf.get(REST_DNS_NAMESERVER, "default")));
              value = SecurityUtil.getServerPrincipal(value, machineName);
            } catch (IOException ie) {
              throw new ServletException("Failed to retrieve server principal", ie);
            }
          }
          if (LOG.isTraceEnabled()) {
            LOG.trace("Setting property " + name + "=" + value);
          }
          name = name.substring(REST_PREFIX_LEN);
          props.setProperty(name, value);
        }
      }
      return props;
    }
  }