每日MySQL之008：MySQL权限简介
MySQL权限简介
MySQL 有自己账户管理方式，这一点和DB2不同，因为DB2没有自己的账户，都是依赖于操作系统账户。MySQL账户由两部分组成：user name 和 host name，语法为 'user_name'@'host_name'. 如果一个账户只有user name，则等同于'user_name'@'%'，这里的%表示所有的host
mysql> show grants for 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> show grants for 'repl'@'db2b';
+-------------------------------------------------+
| Grants for repl@db2b |
+-------------------------------------------------+
| GRANT REPLICATION SLAVE ON *.* TO 'repl'@'db2b' |
+-------------------------------------------------+
1 row in set (0.00 sec)
Administrative privileges 用户此权限的用户能进行数据库管理的工作，不针对特别的数据库
Database privileges 针对具体的某个数据库以及数据库下所有的对象
Privileges for database objects 针对某个数据库对象，比如表、索引、视图、存储过程等
具体如下：
user: User accounts, global privileges, and other non-privilege columns
db: Database-level privileges
tables_priv: Table-level privileges
columns_priv: Column-level privileges
procs_priv: Stored procedure and function privileges
proxies_priv: Proxy-user privileges
https://dev.mysql.com/doc/refman/5.7/en/privileges-provided.html
如果直接使用SQL语句，比如INSERT, UPDATE, 或 DELETE 直接修改grant tables，那需要重启server或者显式地flush privileges操作。 显式地flush privileges有几种办法： FLUSH PRIVILEGES命令， mysqladmin flush-privileges命令或者mysqladminn reload命令。
--Database权限在发出下一次USE db_name后生效
mysql> select current_user();
+-----------------------------------+
| current_user() |
+-----------------------------------+
| skip-grants user@skip-grants host |
+-----------------------------------+
1 row in set (0.03 sec)
MySQL 有自己账户管理方式，这一点和DB2不同，因为DB2没有自己的账户，都是依赖于操作系统账户。MySQL账户由两部分组成：user name 和 host name，语法为 'user_name'@'host_name'. 如果一个账户只有user name，则等同于'user_name'@'%'，这里的%表示所有的host
1. 查看某个用户权限：
可以使用show grants for 'user'@'host'命令查看某个用户的权限：mysql> show grants for 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)
mysql> show grants for 'repl'@'db2b';
+-------------------------------------------------+
| Grants for repl@db2b |
+-------------------------------------------------+
| GRANT REPLICATION SLAVE ON *.* TO 'repl'@'db2b' |
+-------------------------------------------------+
1 row in set (0.00 sec)
2. 权限分类：
MySQL中的权限分为三大类,如下：Administrative privileges 用户此权限的用户能进行数据库管理的工作，不针对特别的数据库
Database privileges 针对具体的某个数据库以及数据库下所有的对象
Privileges for database objects 针对某个数据库对象，比如表、索引、视图、存储过程等
3. 权限存放位置
这些权限信息放在mysql数据库中的下列表当中 user, db, tables_priv, columns_priv, 和 procs_priv，当MySQL启动的时候，会把这些表的信息加载到内存中。具体如下：
user: User accounts, global privileges, and other non-privilege columns
db: Database-level privileges
tables_priv: Table-level privileges
columns_priv: Column-level privileges
procs_priv: Stored procedure and function privileges
proxies_priv: Proxy-user privileges
每个grant table都包含scope列和privilege列，以user表为例，Host,User属于scope列，Select_priv、Insert_priv等属于privilege列：
mysql> describe user;
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Host | char(60) | NO | PRI | | |
| User | char(32) | 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 | |
| Reload_priv | enum('N','Y') | NO | | N | |
| Shutdown_priv | enum('N','Y') | NO | | N | |
| Process_priv | enum('N','Y') | NO | | N | |
| File_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 | |
| Show_db_priv | enum('N','Y') | NO | | N | |
| Super_priv | enum('N','Y') | NO | | N | |
| Create_tmp_table_priv | enum('N','Y') | NO | | N | |
| Lock_tables_priv | enum('N','Y') | NO | | N | |
| Execute_priv | enum('N','Y') | NO | | N | |
| Repl_slave_priv | enum('N','Y') | NO | | N | |
| Repl_client_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 | |
| Create_user_priv | enum('N','Y') | NO | | N | |
| Event_priv | enum('N','Y') | NO | | N | |
| Trigger_priv | enum('N','Y') | NO | | N | |
| Create_tablespace_priv | enum('N','Y') | NO | | N | |
| ssl_type | enum('','ANY','X509','SPECIFIED') | NO | | | |
| ssl_cipher | blob | NO | | NULL | |
| x509_issuer | blob | NO | | NULL | |
| x509_subject | blob | NO | | NULL | |
| max_questions | int(11) unsigned | NO | | 0 | |
| max_updates | int(11) unsigned | NO | | 0 | |
| max_connections | int(11) unsigned | NO | | 0 | |
| max_user_connections | int(11) unsigned | NO | | 0 | |
| plugin | char(64) | NO | | mysql_native_password | |
| authentication_string | text | YES | | NULL | |
| password_expired | enum('N','Y') | NO | | N | |
| password_last_changed | timestamp | YES | | NULL | |
| password_lifetime | smallint(5) unsigned | YES | | NULL | |
| account_locked | enum('N','Y') | NO | | N | |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
45 rows in set (0.00 sec)
mysql> select Host, User, authentication_string,account_locked from user;
+----------------+-----------+-------------------------------------------+----------------+
| Host | User | authentication_string | account_locked |
+----------------+-----------+-------------------------------------------+----------------+
| localhost | root | *F18F94E9C8569A178D632770D54021F45705C972 | N |
| localhost | mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | Y |
| 192.168.16.129 | root | *F18F94E9C8569A178D632770D54021F45705C972 | N |
| db2b | repl | *A424E797037BF97C19A2E88CF7891C5C2038C039 | N |
+----------------+-----------+-------------------------------------------+----------------+
4 rows in set (0.00 sec)authentication_string是MySQL中真正的密码，通过show create user命令看到的，和通过user表看到的是一致的：
mysql> show create user 'repl'@'db2b';
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| CREATE USER for repl@db2b |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| CREATE USER 'repl'@'db2b' IDENTIFIED WITH 'mysql_native_password' AS '*A424E797037BF97C19A2E88CF7891C5C2038C039' REQUIRE NONE PASSWORD EXPIRE DEFAULT ACCOUNT UNLOCK |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
4. 赋予或者撤销权限
使用GRANT 和 REVOKE 语句来赋予和撤销权限，可以赋予和撤销的权限参考如下表6.2 :https://dev.mysql.com/doc/refman/5.7/en/privileges-provided.html
5. 访问控制的两个阶段
MySQL的访问控制分为两个阶段，第一阶段是Connection Verification，在 这个阶段，会检查用户名是否存在、密码是否匹配以及账户是否被锁，只要这些符合，就可以连接到MySQL server。第二个阶段是Request Verification，这个阶段会看连接要做什么操作，检查是否有做这些操作的权限。6. 修改权限之后，何时生效
如果使用账户管理语句来修改的grant tables，比如GRANT, REVOKE, SET PASSWORD, 或者 RENAME USER，那么server会立刻知道这些变化，会重新把grant tables加载到内存中。如果直接使用SQL语句，比如INSERT, UPDATE, 或 DELETE 直接修改grant tables，那需要重启server或者显式地flush privileges操作。 显式地flush privileges有几种办法： FLUSH PRIVILEGES命令， mysqladmin flush-privileges命令或者mysqladminn reload命令。
如果一个连接已经连接到MySQL server，那么权限变化对当前连接影响规则如下：
--Database权限在发出下一次USE db_name后生效
--Global权限和密码变化对当前连接没有作用
mysql> select current_user();
+-----------------------------------+
| current_user() |
+-----------------------------------+
| skip-grants user@skip-grants host |
+-----------------------------------+
1 row in set (0.03 sec)