/*
 * Copyright 2011 LinkedIn, Inc
 *
 * Licensed 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 azkaban.utils;


import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.log4j.Logger;

import java.io.IOException;
import java.util.Properties;

public class SecurityUtils {
  // Secure Hadoop proxy user params
  public static final String ENABLE_PROXYING = "azkaban.should.proxy"; // boolean
  public static final String PROXY_KEYTAB_LOCATION = "proxy.keytab.location";
  public static final String PROXY_USER = "proxy.user";
  public static final String TO_PROXY = "user.to.proxy";

  private static UserGroupInformation loginUser = null;

  /**
   * Create a proxied user based on the explicit user name, taking other parameters
   * necessary from properties file.
   */
  public static synchronized UserGroupInformation getProxiedUser(String toProxy, Properties prop, Logger log, Configuration conf) throws IOException {

    if(conf == null) {
      throw new IllegalArgumentException("conf can't be null");
    }
    UserGroupInformation.setConfiguration(conf);
    // don't do privileged actions in case the hadoop is not secured.
    if(!UserGroupInformation.isSecurityEnabled()) {
    	//we don't get into whether to allow impersonation as anybody in unsecured grid
    	return null;
    }
    
    if(toProxy == null) {
    	throw new IllegalArgumentException("toProxy can't be null");
    }
    
    if (loginUser == null) {
      log.info("No login user. Creating login user");
      String keytab = verifySecureProperty(prop, PROXY_KEYTAB_LOCATION, log);
      String proxyUser = verifySecureProperty(prop, PROXY_USER, log);
      UserGroupInformation.loginUserFromKeytab(proxyUser, keytab);
      loginUser = UserGroupInformation.getLoginUser();
      log.info("Logged in with user " + loginUser);
    } else {
      log.info("loginUser (" + loginUser + ") already created, refreshing tgt.");
      loginUser.checkTGTAndReloginFromKeytab();
    }

    return UserGroupInformation.createProxyUser(toProxy, loginUser);
  }

  /**
   * Create a proxied user, taking all parameters, including which user to proxy
   * from provided Properties.
   */
  public static UserGroupInformation getProxiedUser(Properties prop, Logger log, Configuration conf) throws IOException {
    String toProxy = verifySecureProperty(prop, TO_PROXY, log);
    UserGroupInformation user = getProxiedUser(toProxy, prop, log, conf);
    if(user == null) throw new IOException("Proxy as any user in unsecured grid is not supported!");
    return user;
  }

  public static String verifySecureProperty(Properties properties, String s, Logger l) throws IOException {
    String value = properties.getProperty(s);

    if(value == null) throw new IOException(s + " not set in properties. Cannot use secure proxy");
    l.info("Secure proxy configuration: Property " + s + " = " + value);
    return value;
  }

  public static boolean shouldProxy(Properties prop) {
    String shouldProxy = prop.getProperty(ENABLE_PROXYING);

    return shouldProxy != null && shouldProxy.equals("true");
  }
}
