kerberos的tgt时间理解

之前在impala集成kerberos时，遇到了时间相关的问题，当时没有做充分的测试，对某些理解有些问题（http://caiguangguang.blog.51cto.com/1652935/1381323），今天正好做了下测试，总结如下：

1.klist中expires以及renew until是由client端的/etc/krb5.conf配置文件中的参数决定（在没有超过max的情况）。

server端对应的配置为：
ticket_lifetime = 1h
renew_lifetime = 1d
client端对应的配置为：
ticket_lifetime = 4h
renew_lifetime = 5d

2.server端kdc.conf的配置起到限制client的作用。在client的设置超过max的设置时，按max取值
比如server端设置

max_life = 25h
max_renewable_life = 71d
client端设置
ticket_lifetime = 40h
renew_lifetime = 200d
klist的结果为server配置的值：
Valid starting Expires Service principal
03/25/14 11:55:41 03/26/14 12:55:41 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 06/03/14 11:55:41

3.kdc.conf配置的更改对新建的principal会立即生效，旧的不会生效，如果需要对旧的principal生效，需要modprinc
比如：

modprinc -maxlife 32days -maxrenewlife 32days +allow_renewable krbtgt/REALM

4.理解ticket_lifetime和renew_lifetime
超过renew_lifetime时间之后，不能kinit -R,kinit -R不会改变tgt cache的renew until时间，如果想要改变tgt cache的renew until时间
可以使用kinit -r xx来renew tgt，最大时间由max_renewable_life限制。

ticket_lifetime = 40w
renew_lifetime = 200w
klist
Valid starting Expires Service principal
03/25/14 12:04:25 03/25/14 12:05:05 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 03/25/14 12:07:45
 date
Tue Mar 25 12:05:38 CST 2014
  #超过了expires的时间，但是没有超过renew until的时间
kinit -R
  #可以renew,renew until的时间不会变
klist
Valid starting Expires Service principal
03/25/14 12:05:46 03/25/14 12:06:26 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 03/25/14 12:07:45
date
  #超过renew until的时间
Tue Mar 25 12:08:04 CST 2014
kinit -R
 #不能renew
kinit(v5): Ticket expired while renewing credentials

5.w不代表week的意思，是s的意思（和不带单位一样）

6.如果renew_lifetime 的时间小于ticket_lifetime的时间，则renew until和Expires 时间相同，运行kinit -R不会生效，但是可以运行kinit -r xx

ticket_lifetime = 60
renew_lifetime = 10
Valid starting Expires Service principal
03/25/14 12:25:38 03/25/14 12:26:38 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 03/25/14 12:26:38
date && kinit -R ;klist
Tue Mar 25 12:27:29 CST 2014
Valid starting Expires Service principal
03/25/14 12:27:29 03/25/14 12:27:46 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 03/25/14 12:27:46
date&&kinit -k -t hdfs.keytab hdfs/xxxxx@KERBEROS_HADOOP -r 10d;klist
Tue Mar 25 12:36:49 CST 2014
Valid starting Expires Service principal
03/25/14 12:36:49 03/25/14 12:37:49 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 04/04/14 12:36:49
  #renew life time变化了

7.renew_lifetime的优先级高于max_renewable_life，如果renew_lifetime<=max_renewable_life,
则取renew_lifetime，renew_lifetime>=max_renewable_life时，也是取renew_lifetime的值

ticket_lifetime = 60
renew_lifetime = 120
max_life = 25h
max_renewable_life = 10
Valid starting Expires Service principal
03/25/14 12:42:20 03/25/14 12:43:20 krbtgt/KERBEROS_HADOOP@KERBEROS_HADOOP
        renew until 03/25/14 12:44:20