/**
    * 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;
  
  import java.io.IOException;
  
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  import com.sun.jersey.spi.container.servlet.ServletContainer;
  
  import org.apache.hadoop.security.UserGroupInformation;
  import org.apache.hadoop.security.authorize.AuthorizationException;
  import org.apache.hadoop.security.authorize.ProxyUsers;
  import org.apache.hadoop.conf.Configuration;
  
  /**
   * REST servlet container. It is used to get the remote request user
   * without going through @HttpContext, so that we can minimize code changes.
   */
  @InterfaceAudience.Private
  public class RESTServletContainer extends ServletContainer {
    private static final long serialVersionUID = -2474255003443394314L;
  
    /**
     * This container is used only if authentication and
     * impersonation is enabled. The remote request user is used
     * as a proxy user for impersonation in invoking any REST service.
     */
    @Override
    public void service(final HttpServletRequest request,
        final HttpServletResponse response) throws ServletException, IOException {
      final String doAsUserFromQuery = request.getParameter("doAs");
      RESTServlet servlet = RESTServlet.getInstance();
      if (doAsUserFromQuery != null) {
        Configuration conf = servlet.getConfiguration();
        if (!servlet.supportsProxyuser()) {
          throw new ServletException("Support for proxyuser is not configured");
        }
        // Authenticated remote user is attempting to do 'doAs' proxy user.
        UserGroupInformation ugi = UserGroupInformation.createRemoteUser(request.getRemoteUser());
        // create and attempt to authorize a proxy user (the client is attempting
        // to do proxy user)
        ugi = UserGroupInformation.createProxyUser(doAsUserFromQuery, ugi);
        // validate the proxy user authorization
        try {
          ProxyUsers.authorize(ugi, request.getRemoteAddr(), conf);
        } catch(AuthorizationException e) {
          throw new ServletException(e.getMessage());
        }
        servlet.setEffectiveUser(doAsUserFromQuery);
      } else {
        String effectiveUser = request.getRemoteUser();
        servlet.setEffectiveUser(effectiveUser);
      }
      super.service(request, response);
    }
  }