两个hadoop集群开启Kerberos验证后，集群间不能够相互访问，需要实现Kerberos之间的互信，使用hera集群A的客户端访问hera集群B的服务（实质上是使用Kerberos Realm A上的Ticket实现访问Realm B的服务）。
先决条件：
1）两个集群hera.com和yoga.com均开启Kerberos认证
2）Kerberos的REALM分别设置为hera.com和yoga.com
步骤如下：

1 配置KDC之间的信任ticket

实现hera.com和yoga.com之间的跨域互信，例如使用hera.com的客户端访问yoga.com中的服务，两个REALM需要共同拥有名为krbtgt/yoga.com@hera.com的principal，两个Keys需要保证密码，version number和加密方式一致。默认情况下互信是单向的， yoga.com的客户端访问hera.com的服务，两个REALM需要有krbtgt/hera.com@yoga.com的principal。
向两个集群中添加krbtgt principal

#hera CLUSTERkadmin.local: addprinc –e

"aes128-cts:normal des3-hmac-sha1:normal arcfour-hmac:normal camellia256-cts:normal camellia128-cts:normal des-hmac-sha1:normal des-cbc-md5:normal"

krbtgt/hera.com@yoga.comkadmin.local: addprinc –e

"aes128-cts:normal des3-hmac-sha1:normal arcfour-hmac:normal camellia256-cts:normal camellia128-cts:normal des-hmac-sha1:normal des-cbc-md5:normal"

krbtgt/yoga.com@hera.com #yoga CLUSTERkadmin.local: addprinc –e

"aes128-cts:normal des3-hmac-sha1:normal arcfour-hmac:normal camellia256-cts:normal camellia128-cts:normal des-hmac-sha1:normal des-cbc-md5:normal"

krbtgt/hera.com@yoga.comkadmin.local: addprinc –e

"aes128-cts:normal des3-hmac-sha1:normal arcfour-hmac:normal camellia256-cts:normal camellia128-cts:normal des-hmac-sha1:normal des-cbc-md5:normal"

krbtgt/yoga.com@hera.com

要验证两个entries具有匹配的kvno和加密type，查看命令使用getprinc

kadmin.local: getprinc krbtgt/yoga.com@hera.comPrincipal: krbtgt/yoga.com@hera.comExpiration date: [never]Last password change: Wed Jul 05 14:18:11 CST 2017Password expiration date: [none]Maximum ticket life: 1 day 00:00:00Maximum renewable life: 30 days 00:00:00Last modified: Wed Jul 05 14:18:11 CST 2017 (admin/admin@yoga.com)Last successful authentication: [never]Last failed authentication: [never]Failed password attempts: 0Number of keys: 7Key: vno 1, aes128-cts-hmac-sha1-96Key: vno 1, des3-cbc-sha1Key: vno 1, arcfour-hmacKey: vno 1, camellia256-cts-cmacKey: vno 1, camellia128-cts-cmacKey: vno 1, des-hmac-sha1Key: vno 1, des-cbc-md5MKey: vno 1Attributes:Policy: [none]kadmin.local: getprinc addprinc krbtgt/hera.com@yoga.comusage: get_principal [-terse] principalkadmin.local: getprinc krbtgt/hera.com@yoga.comPrincipal: krbtgt/hera.com@yoga.comExpiration date: [never]Last password change: Wed Jul 05 14:17:47 CST 2017Password expiration date: [none]Maximum ticket life: 1 day 00:00:00Maximum renewable life: 30 days 00:00:00Last modified: Wed Jul 05 14:17:47 CST 2017 (admin/admin@yoga.com)Last successful authentication: [never]Last failed authentication: [never]Failed password attempts: 0Number of keys: 7Key: vno 1, aes128-cts-hmac-sha1-96Key: vno 1, des3-cbc-sha1Key: vno 1, arcfour-hmacKey: vno 1, camellia256-cts-cmacKey: vno 1, camellia128-cts-cmacKey: vno 1, des-hmac-sha1Key: vno 1, des-cbc-md5MKey: vno 1Attributes:Policy: [none]

2 在core-site中配置principal和user的映射RULES

设置hera.security.auth_to_local参数，该参数用于将principal转变为user，一个需要注意的问题是SASL RPC客户端需要远程Server的Kerberos principal在本身的配置中匹配该principal。相同的pricipal name需要分配给源和目标cluster的服务，例如Source Cluster中的NameNode的kerbeors principal name为nn/h@yoga.com，在Destination cluster中NameNode的pricipal设置为nn/h@hera.com（不能设置为nn2/h***@hera.com），例如：
在yoga Cluster和 hera Cluster的core-site中增加：

<property><name>hera.security.auth_to_local</name><value>RULE:[1:$1@$0](^.*@yoga\.com$)s/^(.*)@yoga\.com$/$1/gRULE:[2:$1@$0](^.*@yoga\.com$)s/^(.*)@yoga\.com$/$1/gRULE:[1:$1@$0](^.*@hera\.com$)s/^(.*)@hera\.com$/$1/gRULE:[2:$1@$0](^.*@hera\.com$)s/^(.*)@hera\.com$/$1/gDEFAULT </value></property>

用hera org.apache.hera.security.heraKerberosName 来实现验证，例如:

[root@node1a141 ~]# hera org.apache.hera.security.heraKerberosName hdfs/nodea1a141@yoga.com Name: hdfs/nodea1a141@yoga.com to hdfs

3 在krb5.conf中配置信任关系

3.1 配置capaths

第一种方式是配置shared hierarchy of names，这个是默认及比较简单的方式，第二种方式是在krb5.conf文件中改变capaths，复杂但是比较灵活，这里采用第二种方式。
在两个集群的节点的/etc/krb5.conf文件配置domain和realm的映射关系，例如：在yoga cluster中配置：

[capaths] yoga.com = { hera.com = . }

在hera Cluster中配置：

[capaths] hera.com = { yoga.com = . }

配置成'.'是表示没有intermediate realms

3.2 配置realms

为了是yoga 可以访问hera的KDC，需要将hera的KDC Server配置到yoga cluster中，如下，反之相同：

[realms] yoga.com = { kdc = {host}.yoga.com:88 admin_server = {host}.yoga.com:749 default_domain = yoga.com } hera.com = { kdc = {host}.hera.com:88 admin_server = {host}.hera.com:749 default_domain = hera.com }

3.3 配置domain_realm

在domain_realm中，一般配置成'.yoga.com'和'yoga.com'的格式，'.'前缀保证kerberos将所有的yoga.com的主机均映射到yoga.com realm。但是如果集群中的主机名不是以yoga.com为后缀的格式，那么需要在domain_realm中配置主机与realm的映射关系，例yoga.nn.local映射为yoga.com，需要增加yoga.nn.local = yoga.com。

[domain_realm]dc07-daily-bigdata-yoga-cdh-bj01host-748167.host.idcvdian.com = yoga.comdc07-daily-bigdata-yoga-cdh-bj01host-748168.host.idcvdian.com = yoga.comdc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com = yoga.comdc07-daily-bigdata-yoga-cdh-bj01host-748170.host.idcvdian.com = yoga.comdc07-daily-bigdata-yoga-cdh-bj01host-748171.host.idcvdian.com = yoga.comdc05-prod-bigdata-apollo-bj01host-614146.host.idcvdian.com = hera.comdc05-prod-bigdata-apollo-bj01host-614147.host.idcvdian.com = hera.comidc05-guoyu-hbase-22172.host.idcvdian.com = hera.comidc05-shunyi-bigdata-0333.host.idcvdian.com = hera.comidc05-shunyi-bigdata-0393.host.idcvdian.com = hera.comidc05-shunyi-bigdata-0502.host.idcvdian.com = hera.comidc05-shunyi-bigdata-0503.host.idcvdian.com = hera.comidc07-prod-guoyu-101614145.host.idcvdian.com = hera.comidc07-prod-guoyu-101620135.host.idcvdian.com = hera.comidc07-prod-guoyu-101622148.host.idcvdian.com = hera.com

重启kerberos服务

3.4 配置hdfs-site.xml

在hdfs-site.xml，设置允许的realms
在hdfs-site.xml中设置dfs.namenode.kerberos.principal.pattern为"*"

这个是客户端的匹配规则用于控制允许的认证realms，如果该参数不配置，会有下面的异常：

java.io.IOException: Failed on local exception: java.io.IOException:java.lang.IllegalArgumentException: Server has invalid Kerberosprincipal:nn/ hera.com@ yoga.com; Host Details : local host is: "host1.yoga.com/10.181.22.130"; destination host is: "host2.hera.com":8020;

4 测试

1)使用hdfs命令测试yoga 和hera 集群间的数据访问
例如在yoga Cluster中kinit admin@yoga.com，然后运行hdfs命令，查看本机群和对方集群得hdfs目录：
如果未开启跨域互信，访问对方hdfs目录时会报认证错误

[root@node1a141 ~]# kdestroy 在本机群客户端登陆admin用户,通过kerberos认证[root@node1a141 ~]# kinit adminPassword for admin@yoga.com: 访问本集群hdfs#hdfs dfs -ls /Found 11 itemsdrwxrwxrwt - yarn hadoop 0 2021-03-08 15:26 /app-logsdrwxr-xr-x - yarn hadoop 0 2021-03-03 20:28 /atsdrwxr-xr-x - hdfs hdfs 0 2021-03-08 19:16 /atsv2drwxr-xr-x - root hdfs 0 2021-03-17 17:12 /benchmarksdrwxr-xr-x - hdfs hdfs 0 2021-03-03 20:28 /hdpdrwxr-xr-x - mapred hdfs 0 2021-03-03 20:30 /mapreddrwxrwxrwx - mapred hadoop 0 2021-03-03 20:30 /mr-historydrwxr-xr-x - hdfs hdfs 0 2021-03-03 20:24 /servicesdrwxr-xr-x - hdfs hdfs 0 2021-03-18 15:00 /testdrwxrwxrwx - hdfs hdfs 0 2021-03-15 14:12 /tmpdrwxr-xr-x - hdfs hdfs 0 2021-03-04 14:42 /user 访问对方集群hdfs[14:19:40root@idc05-shunyi-bigdata-0393 /root]#hdfs dfs -ls hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/Found 8 itemsdrwxrwxr-x+ - noops supergroup 0 2020-11-18 22:35 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/backupdrwxrwxr-x+ - hdfs supergroup 0 2020-12-08 17:50 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/benchmarksdrwxrwxrwx+ - mars supergroup 0 2020-07-10 10:41 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/data-rw-r-xr--+ 1 mars supergroup 1550 2020-11-18 17:35 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/derby.logdrwxrwxr-x+ - hdfs supergroup 0 2020-08-24 20:26 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/systemdrwxrwxr-x+ - noops supergroup 0 2020-11-12 08:39 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/tempdrwxrwxrwt+ - hdfs supergroup 0 2021-03-04 11:16 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/tmpdr-xrwxrwx+ - hdfs supergroup 0 2021-03-19 00:54 hdfs://dc07-daily-bigdata-yoga-cdh-bj01host-748169.host.idcvdian.com:8020/user

好知识，才能预见未来

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双Hadoop集群&双Kerberos kdc认证跨域互信