关于mysql.db和数据库层权限
2018-08-30 17:24
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1# 数据库层权限记录位置
表级别的权限记录在mysql.tables_priv表中。
(root@localhost)[mysql]> (root@localhost)[mysql]> desc tables_priv;
+-------------+-----------------------------------------------------------------------------------------------------------------------------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-----------------------------------------------------------------------------------------------------------------------------------+------+-----+-------------------+-----------------------------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(16) | NO | PRI | | |
| Table_name | char(64) | NO | PRI | | |
| Grantor | char(77) | NO | MUL | | |
| Timestamp | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| Table_priv | set('Select','Insert','Update','Delete','Create','Drop','Grant','References','Index','Alter','Create View','Show view','Trigger') | NO | | | |
| Column_priv | set('Select','Insert','Update','References') | NO | | | |
+-------------+-----------------------------------------------------------------------------------------------------------------------------------+------+-----+-------------------+-----------------------------+
8 rows in set (0.00 sec)
然而关于数据库层面的权限记录在mysql.db表中
(root@localhost)[mysql]> desc db;
+-----------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------------+---------------+------+-----+---------+-------+
| Host | char(60) | NO | PRI | | |
| Db | char(64) | NO | PRI | | |
| User | char(16) | NO | PRI | | |
| Select_priv | enum('N','Y') | NO | | N | |
| Insert_priv | enum('N','Y') | NO | | N | |
| Update_priv | enum('N','Y') | NO | | N | |
| Delete_priv | enum('N','Y') | NO | | N | |
| Create_priv | enum('N','Y') | NO | | N | |
| Drop_priv | enum('N','Y') | NO | | N | |
| Grant_priv | enum('N','Y') | NO | | N | |
| References_priv | enum('N','Y') | NO | | N | |
| Index_priv | enum('N','Y') | NO | | N | |
| Alter_priv | enum('N','Y') | NO | | N | |
| Create_tmp_table_priv | enum('N','Y') | NO | | N | |
| Lock_tables_priv | enum('N','Y') | NO | | N | |
| Create_view_priv | enum('N','Y') | NO | | N | |
| Show_view_priv | enum('N','Y') | NO | | N | |
| Create_routine_priv | enum('N','Y') | NO | | N | |
| Alter_routine_priv | enum('N','Y') | NO | | N | |
| Execute_priv | enum('N','Y') | NO | | N | |
| Event_priv | enum('N','Y') | NO | | N | |
| Trigger_priv | enum('N','Y') | NO | | N | |
+-----------------------+-------
2232
--------+------+-----+---------+-------+
22 rows in set (0.00 sec)
(root@localhost)[mysql]> select * from db\G
*************************** 1. row ***************************
Host: %
Db: sample
User: test1
Select_priv: Y
Insert_priv: N
Update_priv: N
Delete_priv: N
Create_priv: Y
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)
这条对应的grant语句是：
(root@localhost)[mysql]> show grants for test1; +------------------------------------------------------------------------------------------------------+ | Grants for test1@% | +------------------------------------------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'test1'@'%' IDENTIFIED BY PASSWORD '*CFA887C680E792C2DCF622D56FB809E3F8BE63CC' | | GRANT SELECT, CREATE ON `sample`.* TO 'test1'@'%' | | GRANT ALL PRIVILEGES ON `sample`.`smp` TO 'test1'@'%' | | GRANT SELECT ON `mysql`.`user` TO 'test1'@'%' | +------------------------------------------------------------------------------------------------------+ 4 rows in set (0.00 sec)
第二条：
GRANT SELECT, CREATE ON
sample.* TO 'test1'@'%'
尝试再增加权限：
(root@localhost)[mysql]> grant all privileges on sample.* to test1; Query OK, 0 rows affected (0.00 sec) (root@localhost)[mysql]> (root@localhost)[mysql]> (root@localhost)[mysql]> select * from db\G *************************** 1. row *************************** Host: % Db: sample User: test1 Select_priv: Y Insert_priv: Y Update_priv: Y Delete_priv: Y Create_priv: Y Drop_priv: Y Grant_priv: N References_priv: Y Index_priv: Y Alter_priv: Y Create_tmp_table_priv: Y Lock_tables_priv: Y Create_view_priv: Y Show_view_priv: Y Create_routine_priv: Y Alter_routine_priv: Y Execute_priv: Y Event_priv: Y Trigger_priv: Y 1 row in set (0.00 sec)
授予all privileges权限。注意点是grant option并不包含在all privileges里面。可以用with子句
(root@localhost)[mysql]> grant all privileges on sample.* to test1 with grant option; Query OK, 0 rows affected (0.00 sec) (root@localhost)[mysql]> select * from db\G *************************** 1. row *************************** Host: % Db: sample User: test1 Select_priv: Y Insert_priv: Y Update_priv: Y Delete_priv: Y Create_priv: Y Drop_priv: Y Grant_priv: Y References_priv: Y Index_priv: Y Alter_priv: Y Create_tmp_table_priv: Y Lock_tables_priv: Y Create_view_priv: Y Show_view_priv: Y Create_routine_priv: Y Alter_routine_priv: Y Execute_priv: Y Event_priv: Y Trigger_priv: Y 1 row in set (0.00 sec)
回收all privileges权限, 错误写法，revoke并不能带with grant option来回收grant option
(root@localhost)[mysql]> revoke all privileges on sample.* from test1 with grant option; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'grant option' at line 1 (root@localhost)[mysql]>
这样写还是不对：
revoke all privileges, grant option on sample.* from test1; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'on sample.* from test1' at line 1
分开写就可以了：
(root@localhost)[mysql]> revoke all privileges on sample.* from test1; Query OK, 0 rows affected (0.00 sec) (root@localhost)[mysql]> revoke grant option on sample.* from test1; Query OK, 0 rows affected (0.00 sec) (root@localhost)[mysql]>
grant option在授予的时候是用with子句，回收的时候需要单独回收。
2#一般用户可访问的数据库：
在test1用户下，查看可以访问的数据库：
(test1@localhost)[(none)]> show databases -> ; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | sample | +--------------------+ 3 rows in set (0.00 sec) (test1@localhost)[(none)]> (test1@localhost)[(none)]> (test1@localhost)[(none)]> (test1@localhost)[(none)]> 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 (test1@localhost)[mysql]> show tables; +-----------------+ | Tables_in_mysql | +-----------------+ | user | #由于只有user表上被授予了select权限，所以show tables只能看到一个表 +-----------------+ 1 row in set (0.00 sec) (test1@localhost)[mysql]> show grants; +---------------------------------------------------------------------+ | Grants for test1@% | +---------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'test1'@'%' IDENTIFIED BY PASSWORD <secret> | | GRANT ALL PRIVILEGES ON `sample`.* TO 'test1'@'%' WITH GRANT OPTION | | GRANT ALL PRIVILEGES ON `sample`.`smp` TO 'test1'@'%' | | GRANT SELECT ON `mysql`.`user` TO 'test1'@'%' | +---------------------------------------------------------------------+ 4 rows in set (0.00 sec)-----------------------------------------------------------------+ | Grants for test1@% | +-------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'test1'@'%' IDENTIFIED BY PASSWORD <secret> | | GRANT ALL PRIVILEGES ON `sample`.`smp` TO 'test1'@'%' | | GRANT SELECT ON `mysql`.`user` TO 'test1'@'%' | +-------------------------------------------------------------------+ 3 rows in set (0.00 sec) (test1@localhost)[mysql]>
sample数据库是被授予的all privileges,所以全库的表对象都是可用呗test1用户访问。至于mysql，只有user表上有一个select权限，所以也被归类在可用访问的数据库之列，但是实际上用show tables只能看到一个表。
3# 数据库层权限的从无到有，给一个用户授予权限后，db表的变化：
a# 建立一个新的数据库sample2
(root@localhost)[(none)]> create database sample2; Query OK, 1 row affected (0.00 sec)
这个时候查看用户test1所拥有的数据库权限，是只有sample数据库。MYSQL数据库并不显示。
(root@localhost)[mysql]> select * from db\G *************************** 1. row *************************** Host: % Db: sample User: test1 Select_priv: Y Insert_priv: Y Update_priv: Y Delete_priv: Y Create_priv: Y Drop_priv: Y Grant_priv: Y References_priv: Y Index_priv: Y Alter_priv: Y Create_tmp_table_priv: Y Lock_tables_priv: Y Create_view_priv: Y Show_view_priv: Y Create_routine_priv: Y Alter_routine_priv: Y Execute_priv: Y Event_priv: Y Trigger_priv: Y 1 row in set (0.00 sec) (root@localhost)[mysql]> #这个时候test1用户去尝试访问sample2数据库也是失败的： (test1@localhost)[sample]> use sample2 ERROR 1044 (42000): Access denied for user 'test1'@'%' to database 'sample2' (test1@localhost)[sample]>
运行授权语句，对test1受援sample2的select权限，这个时候mysql.db数据库中出现了2行数据，多了一行关于sample2的记录：
(root@localhost)[mysql]> select * from db\G *************************** 1. row *************************** Host: % Db: sample2 User: test1 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 *************************** 2. row *************************** Host: % Db: sample User: test1 Select_priv: Y Insert_priv: Y Update_priv: Y Delete_priv: Y Create_priv: Y Drop_priv: Y Grant_priv: Y References_priv: Y Index_priv: Y Alter_priv: Y Create_tmp_table_priv: Y Lock_tables_priv: Y Create_view_priv: Y Show_view_priv: Y Create_routine_priv: Y Alter_routine_priv: Y Execute_priv: Y Event_priv: Y Trigger_priv: Y 2 rows in set (0.00 sec)从记录可用看到test1用户对sample2数据库拥有select权限。也就是访问权限，表示里面的对象都具有。但是里面是没有表的。
(test1@localhost)[(none)]> use sample2; Database changed (test1@localhost)[sample2]> show tables; Empty set (0.00 sec)
#并且test1用户可用select出smp表的数据。 (test1@localhost)[sample2]> select * from smp; +------+------+ | id | name | +------+------+ | 1 | aaa | +------+------+ 1 row in set (0.00 sec) # 然而test1用户并不显示的拥有任在sample2上的表权限。所谓的权限的继承。 (test1@localhost)[information_schema]> select * from TABLE_PRIVILEGES where TABLE_SCHEMA='sample2'; Empty set (0.00 sec)
#奇怪，并没有给表smp授权select，受援的是select on sample2.*。尝试单独对表收回select 权限：
(root@localhost)[sample2]> revoke select on sample2.smp from test1; ERROR 1147 (42000): There is no such grant defined for user 'test1' on host '%' on table 'smp' #以失败告终。显示的revoke并不能收回隐式继承来的权限。 (test1@localhost)[sample2]> show tables; +-------------------+ | Tables_in_sample2 | +-------------------+ | smp | +-------------------+ 1 row in set (0.00 sec)
#这个说明了mysql的权限授予，采用了白名单方式，也就是不管你从什么层次获得过对象的权限，那么你就拥有对方想的权限，而并不会因为细粒度层次上不拥有权限而覆盖高层次上拥有的权限。这就意味着授权的时候，需要特别注意授权的粒度要尽量小。高层次的授权是相当的危险的。
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