/**
 * 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 javax.security.sasl.AuthenticationException;

import net.sf.jpam.Pam;

import org.apache.hadoop.hive.conf.HiveConf;

public class PamAuthenticationProviderImpl implements PasswdAuthenticationProvider {

  private final String pamServiceNames;

  PamAuthenticationProviderImpl(HiveConf conf) {
    pamServiceNames = conf.getVar(HiveConf.ConfVars.HIVE_SERVER2_PAM_SERVICES);
  }

  @Override
  public void Authenticate(String user, String password) throws AuthenticationException {

    if (pamServiceNames == null || pamServiceNames.trim().isEmpty()) {
      throw new AuthenticationException("No PAM services are set.");
    }

    String errorMsg = "Error authenticating with the PAM service: ";
    String[] pamServices = pamServiceNames.split(",");
    for (String pamService : pamServices) {
      try {
        Pam pam = new Pam(pamService);
        boolean isAuthenticated = pam.authenticateSuccessful(user, password);
        if (!isAuthenticated) {
          throw new AuthenticationException(errorMsg + pamService);
        }
      } catch(Throwable e) {
        // Catch the exception caused by missing jpam.so which otherwise would
        // crashes the thread and causes the client hanging rather than notifying
        // the client nicely
        throw new AuthenticationException(errorMsg + pamService, e);
      }
    }
  }
}