[#MDEV-17945] mysql.db contains ghost users which allow some operations on them

Anonymous users have been removed:

MariaDB [test]> select user, host from mysql.user;

+------+-----------+

| user | host      |

+------+-----------+

| root | 127.0.0.1 |

| root | ::1       |

| root | localhost |

| root | ws        |

+------+-----------+

4 rows in set (0.00 sec)

and the server knows they don't exist:

MariaDB [test]> set password for '' = password('test');

ERROR 1133 (28000): Can't find any matching row in the user table

but RENAME or DROP still works:

MariaDB [test]> rename user '' to foo;

Query OK, 0 rows affected (0.03 sec)

nothing of course appears in mysql.user:

MariaDB [test]> select user, host from mysql.user;

+------+-----------+

| user | host      |

+------+-----------+

| root | 127.0.0.1 |

| root | ::1       |

| root | localhost |

| root | ws        |

+------+-----------+

4 rows in set (0.00 sec)

It happens because there is some contents in mysql.db (and it remains there even when anonymous users get dropped):

before RENAME
MariaDB [test]> select user, host from mysql.db;
+------+------+
\| user \| host \|
+------+------+
\| \| % \|
\| \| % \|
+------+------+
2 rows in set (0.00 sec)

after RENAME
MariaDB [test]> select user, host from mysql.db;
+------+------+
\| user \| host \|
+------+------+
\| foo \| % \|
\| foo \| % \|
+------+------+
2 rows in set (0.00 sec)

Now we can work the same way on user foo, etc.

It appears strange. I suppose it was meant to be so once, but I'm not sure it still is.

[MDEV-17945] mysql.db contains ghost users which allow some operations on them Created: 2018-12-09 Updated: 2018-12-11 Resolved: 2018-12-11
Status:	Closed
Project:	MariaDB Server
Component/s:	Authentication and Privilege System
Affects Version/s:	5.5, 10.0, 10.1, 10.2, 10.3, 10.4
Fix Version/s:	N/A