The use of %w in password_query leads to "Failed to expand plugin setting" error

Hi,

I'm trying to convert my existing users to a more modern password scheme by following the how-to at https://wiki.dovecot.org/HowTo/ConvertPasswordSchemes.

One of the steps is to include the use of '%w' in the password_query, like so:

password_query = \
  SELECT domain, password, '%w' AS userdb_plain_pass, \
  domain as userdb_domain, concat('*:storage=', quota) AS
userdb_quota_rule, 5000 as userdb_uid, 5000 as userdb_gid,
'/home/%d/%n' as userdb_home \
  FROM users WHERE (catch='%n' AND domain='%d')

and also to configure:

userdb {
  driver = prefetch
}

in order to combine the user/password_query into one. Now that all seemed to work well, except for one thing. When a user has a % sign in their password, the following error occurs:

Error: Failed to expand plugin setting plain_pass =
'Tfew3322gYEp$%5Qjk0': Unknown variable '%Q'

Which indicates that dovecot is trying to expand variables in the password.

As a consequence, the login process fails.

Is there some way around this behavior?

Thanks in advance,

Filidor Wiese