/**
 * 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.gateway.hadoopauth.filter;

import java.io.IOException;
import java.security.AccessController;
import java.security.Principal;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;

import javax.security.auth.Subject;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.hadoop.gateway.security.PrimaryPrincipal;
import org.apache.hadoop.gateway.i18n.messages.MessagesFactory;
import org.apache.hadoop.gateway.hadoopauth.HadoopAuthMessages;

public class HadoopAuthPostFilter implements Filter {

  private static HadoopAuthMessages log = MessagesFactory.get( HadoopAuthMessages.class );
  
  @Override
  public void init( FilterConfig filterConfig ) throws ServletException {
  }

  @Override
  public void destroy() {
  }
  
  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    HttpServletRequest httpRequest = (HttpServletRequest)request;
    String principal = httpRequest.getRemoteUser();
    if (principal != null) {
        Subject subject = new Subject();
        subject.getPrincipals().add(new PrimaryPrincipal(principal));
        log.hadoopAuthAssertedPrincipal(principal);
        doAs(httpRequest, response, chain, subject);
    } 
    else {
      ((HttpServletResponse)response).sendError(HttpServletResponse.SC_FORBIDDEN, "User not authenticated");
    }
  }

  private void doAs(final ServletRequest request, final ServletResponse response, final FilterChain chain, Subject subject)
      throws IOException, ServletException {
      try {
        Subject.doAs(
            subject,
            new PrivilegedExceptionAction<Object>() {
              public Object run() throws Exception {
                chain.doFilter(request, response);
                return null;
              }
            }
            );
      }
      catch (PrivilegedActionException e) {
        Throwable t = e.getCause();
        if (t instanceof IOException) {
          throw (IOException) t;
        }
        else if (t instanceof ServletException) {
          throw (ServletException) t;
        }
        else {
          throw new ServletException(t);
        }
      }
    }
  
}
