/**
 * 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.hive.service.auth;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;

import javax.security.auth.Subject;

import org.apache.hadoop.hive.thrift.TFilterTransport;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;

/**
 * This is used on the client side, where the API explicitly opens a transport to
 * the server using the Subject.doAs().
 */
public class TSubjectAssumingTransport extends TFilterTransport {

  public TSubjectAssumingTransport(TTransport wrapped) {
    super(wrapped);
  }

  @Override
  public void open() throws TTransportException {
    try {
      AccessControlContext context = AccessController.getContext();
      Subject subject = Subject.getSubject(context);
      Subject.doAs(subject, new PrivilegedExceptionAction<Void>() {
        public Void run() {
          try {
            wrapped.open();
          } catch (TTransportException tte) {
            // Wrap the transport exception in an RTE, since Subject.doAs() then goes
            // and unwraps this for us out of the doAs block. We then unwrap one
            // more time in our catch clause to get back the TTE. (ugh)
            throw new RuntimeException(tte);
          }
          return null;
        }
      });
    } catch (PrivilegedActionException ioe) {
      throw new RuntimeException("Received an ioe we never threw!", ioe);
    } catch (RuntimeException rte) {
      if (rte.getCause() instanceof TTransportException) {
        throw (TTransportException) rte.getCause();
      } else {
        throw rte;
      }
    }
  }

}