Authentication

I don't think this is possible without modifying/extending some core code. The password policy checking function doesn't have an extension point built in. And the authentication plugins are not assumed to check the password policy themselves. Moodle assumes that you check your password policy centrally, and if the password passes the check, then the auth plugins simply perform the actions to update it wherever they have to.

So I'd say that the less invasive way to achieve what you want is to add a config setting (either in config.php or directly in the database, in prefix_settings table) with the name of a function that would perform as many additional policy checks as you want. Let's assume for the sake of the example that the setting is called $CFG->additional_password_policy_checks_function. The function would need to take the same two parameters as check_password_policy() function:

• a string with the new password to check
• an error message string, passed in by reference, where you would add (concatenate) your additional error messages.

Then you would just add something like this near the end of check_password_policy()

if (!check_consecutive_identical_characters($password, $CFG->maxconsecutiveidentchars)) {
    $errmsg .= '<div>'. get_string('errormaxconsecutiveidentchars', 'auth', $CFG->maxconsecutiveidentchars) .'</div>';
}

// -- Add from this line --
if(!empty($CFG->additional_password_policy_checks_function)) {
    call_user_func_array($CFG->additional_password_policy_checks_function,
                         array($password, &$errmsg));
}
// -- Add to this line --

if ($errmsg == '') {
    return true;
} else {
    return false;
}

That seems to work as expected in my test Moodle site.

Saludos.

Iñaki.