Best Practices: Additional User Security

By default MySQL allows you to create user accounts and privileges with no password. In my earlier MySQL Best Practices: User Security I describe how to address the default installation empty passwords.

For new user accounts, you can improve this default behavior using the SQL_MODE variable, with a value of NO_AUTO_CREATE_USER. As detailed via the 5.1 Reference Manual

NO_AUTO_CREATE_USER

Prevent the GRANT statement from automatically creating new users if it would otherwise do so, unless a nonempty password also is specified.

Having set this variable I attempted to show the error of operation to demonstrate in my upcoming “MySQL Idiosyncrasies that bite” presentation.

Confirm Settings

mysql> show global variables like 'sql_mode';
+---------------+---------------------+
| Variable_name | Value               |
+---------------+---------------------+
| sql_mode      | NO_AUTO_CREATE_USER |
+---------------+---------------------+
1 row in set (0.00 sec)

mysql> show session variables like 'sql_mode';
+---------------+---------------------+
| Variable_name | Value               |
+---------------+---------------------+
| sql_mode      | NO_AUTO_CREATE_USER |
+---------------+---------------------+
1 row in set (0.00 sec)

Create error condition

mysql> CREATE USER superuser@localhost;
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT ALL ON *.* TO superuser@localhost;
Query OK, 0 rows affected (0.00 sec)
mysql> exit

What the? Surely this isn’t right.

$ mysql -usuperuser

mysql> SHOW GRANTS;
+--------------------------------------------------------+
| Grants for superuser@localhost                         |
+--------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'superuser'@'localhost' |
+--------------------------------------------------------+

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.1.39    |
+-----------+

Well that’s broken functionality.

What should happen as described in Bug #43938 is a cryptic message as reproduced below.

mysql> GRANT SELECT ON foo.* TO 'geert12'@'localhost';
ERROR 1133 (42000): Can't find any matching row in the user table
mysql> GRANT SELECT ON *.* TO geert12@localhost IDENTIFIED BY 'foobar';
Query OK, 0 rows affected (0.00 sec)

It seems however that the user of CREATE USER first nullifies this expected behavior, hence new Bug #54208.

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One Response to “Best Practices: Additional User Security”

  1. Shlomi Noach says:

    Hi,
    Again, this is covered by oak-security-audit, pardon my shameless plug.