[Dovecot] Client Cert Auth Problem

Hello,

is there a config possible which supports both of following authentication schemes ?

1st: If user presents a client certificate, he can log in w/o username/password, where user id comes from CN. Accepting any password is not the right solution.

2nd: If user does not present a client certificate, he have to authenticate by username/password.

In both cases user data is read from userdb LDAP, which is already working. I was not able to get both auth schemes working at same time. With Postfix such a config is fully operable.

regards Christian