java程序中获取kerberos登陆hadoop

本文由作者周梁伟授权网易云社区发布。

一般我们在使用kbs登陆hadoop服务时都直接在shell中调用kinit命令来获取凭证，这种方式简单直接，只要获取一次凭证之后都可以在该会话过程中重复访问。但是这种方式一个明显的问题就是如果在本次shell中会间隔调用不同的java程序，而这些程序需要访问不同权限的问题，需要在访问前调用各自的ktab文件获得授权。这中场景下情况会变得非常复杂，这时如果把kbs认证的过程移到java程序中就会简单很多，每个java程序中获取各自的凭证，及时多个进程同时运行也不会产生相互影响。我这里介绍两种java中获取kbs凭证的方法，分别使用 org.apache.hadoop.security.SecurityUtil 和 org.apache.hadoop.security.UserGroupInformation 两个类实现。

一、 使用ktab文件简单登录方式
登录操作函数
/**

  * 尝试使用kerberos认证登录hfs

  *@params

  *       conf: 配置，其中带有keytab相关配置属性

  *       keytab_KEY: 表示conf中代表keytab文件属性的键值

  *       principal_KEY: 表示conf中代表principal属性的键值

  * @throws IOException

  */

 static void tryKerberosLogin(Configuration conf, String keytab_KEY, String principal_KEY) throws IOException {

      boolean useSec = true;

      LOG.info("Hadoop Security enabled: " + useSec);

      if (!useSec) {

           return;

      }

      try {

           @SuppressWarnings("rawtypes")

           Class c = Class.forName("org.apache.hadoop.security.SecurityUtil");

           // get method login(Configuration, String, String);

           @SuppressWarnings("unchecked")

           Method m = c.getMethod("login", Configuration.class, String.class,

                     String.class);

           m.invoke(null, conf,  keytab_KEY, principal_KEY);

           LOG.info("successfully authenticated with keytab");

      } catch (Exception e) {

           LOG.error(

                     "Flume failed when attempting to authenticate with keytab "

                               + SimpleConfiguration.get().getKerberosKeytab()

                               + " and principal '"

                               + SimpleConfiguration.get().getKerberosPrincipal()

                               + "'", e);

           return;

      }

 }

配置
...

<property>

<name>flume.security.kerberos.principal</name>

<description></description>

</property>

<property>

<name>flume.security.kerberos.keytab</name>

<value>resources/flume.keytab</value>

<description></description>

</property>

…

Sample

//调用例子

public FileSystem getFileSystem(Configuration conf) {

           String KEYFILE_key = "flume.security.kerberos.keytab";

           String PRINCIPAL_key = "flume.security.kerberos.principal";



           try {

                // 尝试用kerberos登录

                tryKerberosLogin(conf, KEYFILE_key, PRINCIPAL_key);

                // 获取一个hdfs实例

                instance = FileSystem.get( conf);

           } catch (IOException e) {

                LOG.error("try getFileSystem fail()", e);

           } catch (URISyntaxException e) {

                LOG.error("try getFileSystem fail()", e);

           }

      }

      return instance;

 }

二、 通过UserGroupInformation获取代理用户方式
package com.netease.backend.bigdata.wa.jobs;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.security.UserGroupInformation;

import org.apache.log4j.Logger;

import org.hsqldb.lib.StringUtil;

import com.netease.backend.bigdata.wa.core.ConfKeys;

/**

• 代理用户信息认证工具

*

• @author zhouliangwei

*

*/

public class ProxyUGI {

 private static Logger LOG = Logger.getLogger(ProxyUGI.class);



 private static UserGroupInformation instance = null;

 /**

  * 从Configuration中获取代理用户的相关配置，并获取UserGroupInformation

  * @return

  * @throws IOException

  */

 public synchronized static UserGroupInformation getProxyUGI(Configuration conf) {

      if (instance != null)

           return instance;

      try {

           String username = conf.get(ConfKeys.MR_USER_NAME, "");

           String proxyPrincipal = conf.get(ConfKeys.WDA_PROXY_PRINCIPAL, "");

           String proxyKtab = conf.get(ConfKeys.WDA_PROXY_KEYTAB, "");

           if (StringUtil.isEmpty(username)

                     || StringUtil.isEmpty(proxyPrincipal)

                     || StringUtil.isEmpty(proxyKtab)) {

                LOG.warn("config properties: ["

                          + ConfKeys.MR_USER_NAME

                          + ", "

                          + ConfKeys.WDA_PROXY_PRINCIPAL

                          + ", "

                          + ConfKeys.WDA_PROXY_KEYTAB

                          + "] in config file './conf/wda-core.xml' must be set!, quite use proxy mechanism");

                return null;

           }

           instance = UserGroupInformation.createProxyUser(username,

                     UserGroupInformation.loginUserFromKeytabAndReturnUGI(

                               proxyPrincipal, proxyKtab));

      } catch (IOException ex) {

           //just ignore;

      }

      return instance;

 }

}

调用方式
...

public static void main(final String[] args) throws Exception {

      UserGroupInformation ugi = ProxyUGI.getProxyUGI();

      if (ugi != null) {

           ugi.doAs(new PrivilegedExceptionAction<EventJobClient>() {

                public EventJobClient run() throws Exception {

                     EventJobClient mr = new EventJobClient();

                     int code = ToolRunner.run(mr, args);

                     System.exit(code);

                     return mr;

                }

           });

           System.exit(1);

      } else {

           int exitCode = ToolRunner.run(new EventJobClient(), args);

           System.exit(exitCode);

      }

 }

….

文章来源： 网易云社区