今天遇到一个需求：修改MySQL用户的权限，需要限制特定IP地址才能访问，第一次遇到这类需求，结果在测试过程，使用更新系统权限报发现出现了一些问题， 具体演示如下. 下面测试环境为MySQL 5.6.20. 如有其它版本与下面测试结果有出入，请以实际环境为准。
我们先创建一个测试用户LimitIP，只允许192.168段的IP地址访问，具体权限如下所示：
mysql> GRANT SELECT ON MyDB.* TO LimitIP@'192.168.%' IDENTIFIED BY 'LimitIP';
Query OK, 0 rows affected (0.01 sec)
mysql> GRANT INSERT ,UPDATE,DELETE ON MyDB.kkk TO LimitIP@'192.168.%';
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> show grants for LimitIP@'192.168.%';
+----------------------------------------------------------------------------------------------------------------+
| Grants for LimitIP@192.168.% |
+----------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'LimitIP'@'192.168.%' IDENTIFIED BY PASSWORD '*72DDE03E02CC55A9478A82F3F4EBE7F639249DEC' |
| GRANT SELECT ON `MyDB`.* TO 'LimitIP'@'192.168.%' |
| GRANT INSERT, UPDATE, DELETE ON `MyDB`.`kkk` TO 'LimitIP'@'192.168.%' |
+----------------------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)
mysql>
假设现在收到需求：这个用户只允许这个IP地址192.168.103.17访问，于是我打算更新mysql.user表，如下所示：
mysql> select user, host from mysql.user where user='LimitIP';
+---------+-----------+
| user | host |
+---------+-----------+
| LimitIP | 192.168.% |
+---------+-----------+
1 row in set (0.00 sec)
mysql> update mysql.user set host='192.168.103.17' where user='LimitIP';
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)
mysql> select user, host from user where user='LimitIP';
ERROR 1046 (3D000): No database selected
mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select user, host from user where user='LimitIP';
+---------+----------------+
| user | host |
+---------+----------------+
| LimitIP | 192.168.103.17 |
+---------+----------------+
1 row in set (0.00 sec)
mysql> show grants for LimitIP@'192.168.103.17';
+---------------------------------------------------------------------------------------------------------------------+
| Grants for LimitIP@192.168.103.17 |
+---------------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'LimitIP'@'192.168.103.17' IDENTIFIED BY PASSWORD '*72DDE03E02CC55A9478A82F3F4EBE7F639249DEC' |
+---------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql>
上面测试发现，如果这样只修改mysql.user表， 那么之前的权限没有了，如下所示，如果你查询mysql.db、 mysql.tables_priv 发现Host的字段值依然为192.168.%
mysql> select * from mysql.db where user='LimitIP'G;
*************************** 1. row ***************************
Host: 192.168.%
Db: MyDB
User: LimitIP
Select_priv: Y
Insert_priv: N
Update_priv: N
Delete_priv: N
Create_priv: N
Drop_priv: N
Grant_priv: N
References_priv: N
Index_priv: N
Alter_priv: N
Create_tmp_table_priv: N
Lock_tables_priv: N
Create_view_priv: N
Show_view_priv: N
Create_routine_priv: N
Alter_routine_priv: N
Execute_priv: N
Event_priv: N
Trigger_priv: N
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> select * from mysql.tables_priv where user='LimitIP'G;
*************************** 1. row ***************************
Host: 192.168.%
Db: MyDB
User: LimitIP
Table_name: kkk
Grantor: root@localhost
Timestamp: 0000-00-00 00:00:00
Table_priv: Insert,Update,Delete
Column_priv:
1 row in set (0.00 sec)
ERROR:
No query specified
所以我继续修改 mysql.db、 mysql.tables_priv 表，然后测试验证终于OK了（请见下面测试步骤），当然如果账户的权限不止这几个层面，你可能还必须修改例如mysql.columns_priv、mysql.procs_priv等表
mysql> show grants for LimitIP@'192.168.%';
ERROR 1141 (42000): There is no such grant defined for user 'LimitIP' on host '192.168.%'
mysql>
mysql>
mysql> update mysql.db set host='192.168.103.17' where user='LimitIP';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> update mysql.tables_priv set host='192.168.103.17' where user='LimitIP';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for LimitIP@'192.168.103.17';
+---------------------------------------------------------------------------------------------------------------------+
| Grants for LimitIP@192.168.103.17 |
+---------------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'LimitIP'@'192.168.103.17' IDENTIFIED BY PASSWORD '*72DDE03E02CC55A9478A82F3F4EBE7F639249DEC' |
| GRANT SELECT ON `MyDB`.* TO 'LimitIP'@'192.168.103.17' |
| GRANT INSERT, UPDATE, DELETE ON `MyDB`.`kkk` TO 'LimitIP'@'192.168.103.17' |
+---------------------------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)
mysql>
如果需要修改用户的IP限制，其实更新mysql相关权限表不是上上策，其实有更好的方法，那就是RENAME USER Syntax
mysql> RENAME USER 'LimitIP'@'192.168.103.17' TO 'LimitIP'@'192.168.103.18';
Query OK, 0 rows affected (0.00 sec)
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for 'LimitIP'@'192.168.103.18';
+---------------------------------------------------------------------------------------------------------------------+
| Grants for LimitIP@192.168.103.18 |
+---------------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'LimitIP'@'192.168.103.18' IDENTIFIED BY PASSWORD '*72DDE03E02CC55A9478A82F3F4EBE7F639249DEC' |
| GRANT SELECT ON `MyDB`.* TO 'LimitIP'@'192.168.103.18' |
| GRANT INSERT, UPDATE, DELETE ON `MyDB`.`kkk` TO 'LimitIP'@'192.168.103.18' |
+---------------------------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)
mysql>