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Security in MySQL  /  Security Plugins  /  The Password Validation Plugin

7.2 The Password Validation Plugin

The validate_password plugin can be used to test passwords and improve security. This plugin implements two capabilities:

  • In statements that assign a password supplied as a cleartext value, the value is checked against the current password policy and rejected if it is weak (the statement returns an ER_NOT_VALID_PASSWORD error). This affects the ALTER USER, CREATE USER, GRANT, and SET PASSWORD statements. Passwords given as arguments to the PASSWORD() and OLD_PASSWORD() functions are checked as well.

  • The strength of potential passwords can be assessed using the VALIDATE_PASSWORD_STRENGTH() SQL function, which takes a password argument and returns an integer from 0 (weak) to 100 (strong).

For example, the cleartext password in the following statement is checked. Under the default password policy, which requires passwords to be at least 8 characters long, the password is weak and the statement produces an error:

ERROR 1819 (HY000): Your password does not satisfy the current policy

Passwords specified as already hashed values are not checked because the original password value is not available:

mysql> ALTER USER 'jeffrey'@'localhost'
    -> IDENTIFIED WITH mysql_native_password
    -> AS '*0D3CED9BEC10A777AEC23CCC353A8C08A633045E';
Query OK, 0 rows affected (0.01 sec)

The parameters that control password checking are available as the values of the system variables having names of the form validate_password_xxx. These variables can be modified to configure password checking; see Section 7.2.2, “Password Validation Plugin Options and Variables”.

The three levels of password checking are LOW, MEDIUM, and STRONG. The default is MEDIUM; to change this, modify the value of validate_password_policy. The policies implement increasingly strict password tests. The following descriptions refer to default parameter values; these can be modified by changing the appropriate system variables.

  • LOW policy tests password length only. Passwords must be at least 8 characters long.

  • MEDIUM policy adds the conditions that passwords must contain at least 1 numeric character, 1 lowercase and uppercase character, and 1 special (nonalphanumeric) character.

  • STRONG policy adds the condition that password substrings of length 4 or longer must not match words in the dictionary file, if one has been specified.

If the validate_password plugin is not installed, the validate_password_xxx system variables are not available, passwords in statements are not checked, and VALIDATE_PASSWORD_STRENGTH() always returns 0. For example, accounts can be assigned passwords shorter than 8 characters.

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