[Dovecot] Dovecot Director and MasterUsers

[Timo Sirainen]

On 8.4.2014, at 16.54, Daniel Parthey <d.parthey at metaways.de> wrote:

> the Dovecot Director determines the backend host in some way by hashing the username:
> 
> http://wiki2.dovecot.org/Director
> 
> For normal logins username at example.org, the director always gets the same hash
> for the same username and ensures that the login is always proxied to the same backend.
> 
> But what about MasterUsers in combination with Dovecot Director?
> 
> http://wiki2.dovecot.org/Authentication/MasterUsers
> 
> Which configuration directives should be used to make sure that logins
> 
> username at example.org*masteruser1 at example.org
> username at example.org*masteruser2 at example.org
> username at example.org*masteruser3 at example.org
> 
> go to the same mailbox backend, in order to avoid NFS caching
> conflicts for mailbox username at example.org which should always
> reside on the same NFS client?
> 
> Is the master user cut off from behind the master_user_separator?

Yes, assuming your director (not backend) is configured with auth_master_user_separator=*. It's translated into SASL PLAIN authentication for backends where director hashes only the username.

> How is the director hash exactly calculated?
> Can the director hashing algorithm be configured in some way?

director_username_hash can be used for configuring.

BTW. There are also some kludgy things you can do with this if you need some weird setup, such as using user at domain1@domain2 style usernames where director_username_hash = %{username}@%{domain_first} and then you can use the %{domain_last} variable in the backend to do some extra stuff. For example if you want to have @readonly user with readonly ACLs.