core/src/main/java/org/apache/accumulo/core/rpc/UGIAssumingTransport.java

/*
 * 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
 *
 *   https://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.accumulo.core.rpc;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.security.PrivilegedExceptionAction;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.hadoop.security.UserGroupInformation;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;

/**
 * The Thrift SASL transports call Sasl.createSaslServer and Sasl.createSaslClient inside open().
 * So, we need to assume the correct UGI when the transport is opened so that the SASL mechanisms
 * have access to the right principal. This transport wraps the Sasl transports to set up the right
 * UGI context for open().
 *
 * This is used on the client side, where the API explicitly opens a transport to the server.
 *
 * Lifted from Apache Hive 0.14
 */
public class UGIAssumingTransport extends FilterTransport {
  protected UserGroupInformation ugi;

  public UGIAssumingTransport(TTransport wrapped, UserGroupInformation ugi) {
    super(wrapped);
    this.ugi = ugi;
  }

  @Override
  public void open() throws TTransportException {
    final AtomicReference<TTransportException> holder = new AtomicReference<>(null);
    try {
      ugi.doAs((PrivilegedExceptionAction<Void>) () -> {
        try {
          getWrapped().open();
        } catch (TTransportException tte) {
          holder.set(tte);
        }
        return null;
      });
    } catch (IOException e) {
      throw new UncheckedIOException(e);
    } catch (InterruptedException e) {
      throw new IllegalStateException(e);
    }

    // Make sure the transport exception gets (re)thrown if it happened
    TTransportException tte = holder.get();
    if (tte != null) {
      throw tte;
    }
  }
}