问题描述：公司漏扫发现数据库内出现空用户名及密码，需要对这些用户进行整改
1.首先出现了疑问，这些空的用户名是怎么出现的，而且不附带密码。
2.可以手动这样创建这样的用户名和密码形式么。
3.如果能这样创建一个用户，是不是我可以不用用户名和密码能直接登录服务器呢。
4.如何对这样的形式存在进行规避。
空用户名为匿名用户，那么匿名用户能登录么，登录方式可以不用带用户名么。延伸到了mysql的匿名用户，安装完MySQL后，系统默认会创建一个不需要密码的root用户，和一个无用户名无密码的匿名用户(Anonymous Account)。进行下面的初始化操作以合理授权，增强安全。
mysql> create user ''@'localhost' ;
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host,authentication_string from mysql.user;
+------------------+-----------+------------------------------------------------------------------------+
| user | host | authentication_string |
+------------------+-----------+------------------------------------------------------------------------+
| employee_proxy | % | *DC6775B6D1F01EFD99CC191E929862480DAC2F7A |
| root | % | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| test01 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| tspmlf | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| username | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| | localhost | |
| backuper | localhost | *4DDFC2472B45DA20DB77FD7F3C19996CCCE35897 |
| employee | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.infoschema | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root | localhost | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| zabbix | localhost | *C5A9E29672800EE5E1A1B0EA8C397728FD1660D8 |
+------------------+-----------+------------------------------------------------------------------------+
13 rows in set (0.00 sec)
[mysql@rhel7 ~]$ /usr/local/mysql8/bin/mysql -u -p -hlocalhost -P33306 -S /data/mysql8/db_dxpt08/mysql.sock
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 8.0.22 MySQL Community Server - GPL Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
--测试证明，采用匿名登录测试可以直接登录数据库，不过登录进来权限受限制
mysql>
mysql> show grants for ''@'localhost' ;
+--------------------------------------+
| Grants for @localhost |
+--------------------------------------+
| GRANT USAGE ON *.* TO ``@`localhost` |
+--------------------------------------+
1 row in set (0.00 sec)
mysql> select current_user(),user();
+----------------+--------------+
| current_user() | user() |
+----------------+--------------+
| @localhost | -p@localhost |
+----------------+--------------+
1 row in set (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> select user,host from mysql.user;
ERROR 1142 (42000): SELECT command denied to user ''@'localhost' for table 'user'
如何进行规避，删除这种方式
--用drop ‘’@‘localhost’ 方式进行删除
mysql> select user,host,authentication_string from mysql.user;
+------------------+-----------+------------------------------------------------------------------------+
| user | host | authentication_string |
+------------------+-----------+------------------------------------------------------------------------+
| employee_proxy | % | *DC6775B6D1F01EFD99CC191E929862480DAC2F7A |
| root | % | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| test01 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| tspmlf | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| username | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| | localhost | |
| backuper | localhost | *4DDFC2472B45DA20DB77FD7F3C19996CCCE35897 |
| employee | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.infoschema | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root | localhost | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| zabbix | localhost | *C5A9E29672800EE5E1A1B0EA8C397728FD1660D8 |
+------------------+-----------+------------------------------------------------------------------------+
13 rows in set (0.00 sec) mysql> drop user ''@'localhost';
Query OK, 0 rows affected (0.01 sec) mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec) mysql> select user,host,authentication_string from mysql.user;
+------------------+-----------+------------------------------------------------------------------------+
| user | host | authentication_string |
+------------------+-----------+------------------------------------------------------------------------+
| employee_proxy | % | *DC6775B6D1F01EFD99CC191E929862480DAC2F7A |
| root | % | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| test01 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| tspmlf | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| username | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| backuper | localhost | *4DDFC2472B45DA20DB77FD7F3C19996CCCE35897 |
| employee | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.infoschema | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root | localhost | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| zabbix | localhost | *C5A9E29672800EE5E1A1B0EA8C397728FD1660D8 |
+------------------+-----------+------------------------------------------------------------------------+
12 rows in set (0.00 sec)
--delete from mysql.user where user='';
mysql> create user ''@'127.0.0.1' ;
Query OK, 0 rows affected (0.01 sec) mysql> select user,host,authentication_string from mysql.user;
+------------------+-----------+------------------------------------------------------------------------+
| user | host | authentication_string |
+------------------+-----------+------------------------------------------------------------------------+
| employee_proxy | % | *DC6775B6D1F01EFD99CC191E929862480DAC2F7A |
| root | % | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| test01 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| tspmlf | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| username | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| | 127.0.0.1 | |
| backuper | localhost | *4DDFC2472B45DA20DB77FD7F3C19996CCCE35897 |
| employee | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.infoschema | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root | localhost | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| zabbix | localhost | *C5A9E29672800EE5E1A1B0EA8C397728FD1660D8 |
+------------------+-----------+------------------------------------------------------------------------+
13 rows in set (0.00 sec) mysql> delete from mysql.user where user='';
Query OK, 1 row affected (0.00 sec) mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec) mysql> select user,host,authentication_string from mysql.user;
+------------------+-----------+------------------------------------------------------------------------+
| user | host | authentication_string |
+------------------+-----------+------------------------------------------------------------------------+
| employee_proxy | % | *DC6775B6D1F01EFD99CC191E929862480DAC2F7A |
| root | % | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| test01 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| tspmlf | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| username | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| backuper | localhost | *4DDFC2472B45DA20DB77FD7F3C19996CCCE35897 |
| employee | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.infoschema | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys | localhost | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root | localhost | *858D7135C67CFFAEE40C01A38AB99018DBB245A7 |
| zabbix | localhost | *C5A9E29672800EE5E1A1B0EA8C397728FD1660D8 |
+------------------+-----------+------------------------------------------------------------------------+
12 rows in set (0.00 sec)
匿名用户一般会在刚创建完数据库时，用来防止用户忘记登录密码。如果不及时清理掉，会暴露一个风险给漏扫。
