

Master users/passwords
======================


It's possible to configure master users who are able to log in as other users. It's also possible to directly log in as any user using a master password, although this isn't recommended. 


Master users
============


There are two ways for master users to log in as other users: 

 1. Give the login username in >>SASL mechanism's<< authorization ID field. Currently only PLAIN SASL mechanism supports this. 
 2. Specify both the master username and the login username in the same username field. The usernames are separated by a string configured in 'auth_master_user_separator' setting. UW-IMAP uses "*" as the separator, so that could be a good choice. Using "*" as the separator, the master user would log in as "login_user*master_user". 
Master users are configured by adding a new >>passdb<< with 'master=yes' setting. The users in the master passdb cannot log in as themselves, only as other people. That means they don't need to exist in the >>userdb<<, because the userdb lookup is done only for the user they're logging in as. 
You should also add 'pass=yes' setting to the master passdb if possible. It means that Dovecot verifies that the login user really exists before allowing the master user to log in. Without the setting if a non-existing login username is given, depending on the configuration it could either return an internal login error (the userdb lookup failed) or create a whole new user (with eg. >>static userdb<<). 'pass=yes' doesn't work with PAM or LDAP with 'auth_bind=yes', because both of them require knowing the user's password. 
'pass=yes' is especially useful with >>Checkpassword<< passdb because the script gets both the login and the master username as environment variables. Other passdbs see only the login username in '%u'. In future there will probably be another setting to make the user verification to be done from userdb. 
If you want master users to be able to log in as themselves, you'll need to either add the user to the normal passdb or add the passdb to 'dovecot.conf' twice, with and without the 'master=yes'. Note that if the passdbs point to different locations, the user can have a different password when logging in as other users than when logging in as himself. This is a good idea since it can avoid accidentally logging in as someone else. 
Usually it's better to having only a few special master users that are used *only* to log in as other people. One example could be a special "spam" master user that trains the users' spam filters by reading the messages from the user's spam mailbox. 


Example configuration
=====================



---%<-------------------------------------------------------------------------
auth_master_user_separator=*
auth default {
  passdb passwd-file {
    args = /etc/dovecot/passwd.masterusers
    master = yes
    pass = yes
  }
  passdb shadow {
  }
  userdb passwd {
  }
}
---%<-------------------------------------------------------------------------

Where the 'passwd.masterusers' file would contain the master usernames and passwords: 

---%<-------------------------------------------------------------------------
admin:{SHA1}nU4eI71bcnBGqeO0t9tXvY1u5oQ=
admin2:{SHA1}i+UhJqb95FCnFio2UdWJu1HpV50=
---%<-------------------------------------------------------------------------

One way to create this master file is to use the htaccess program as follows: 

---%<-------------------------------------------------------------------------
htpasswd -b -c -s passwd.masterusers user password
---%<-------------------------------------------------------------------------



SQL Example
===========


The master passdb doesn't have to be passwd-file, it could be an SQL query as well: 

---%<-------------------------------------------------------------------------
auth_master_user_separator=*
auth default {
  passdb sql {
    args = /etc/dovecot/dovecot-sql-master.conf
    master = yes
    pass = yes
  }
  passdb sql {
    args = /etc/dovecot/dovecot-sql.conf
  }
  userdb sql {
    args = /etc/dovecot/dovecot-sql.conf
  }
}
---%<-------------------------------------------------------------------------

'dovecot-sql-master.conf' would contain all the normal connection settings and a 'password_query': 

---%<-------------------------------------------------------------------------
password_query = SELECT password FROM users WHERE userid = '%u' and master_user = true
---%<-------------------------------------------------------------------------



Testing
=======



---%<-------------------------------------------------------------------------
# telnet localhost 143
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK Dovecot ready.
1 login loginuser*masteruser masterpass
1 OK Logged in.
---%<-------------------------------------------------------------------------

If you had any problems, set 'auth_debug=yes' and look at the logs. 


Master passwords
================


The easiest way to implement this is with SQL: 

---%<-------------------------------------------------------------------------
password_query = SELECT user, 'master-password' AS password FROM users WHERE userid = '%u'
---%<-------------------------------------------------------------------------

If you don't have the users in SQL database, you can still fake it: 

---%<-------------------------------------------------------------------------
password_query = SELECT '%u' AS user, 'master-password' AS password
---%<-------------------------------------------------------------------------

However note that the above will allow logins for any username using the master password, even those that don't really exist. 
Then in your dovecot.conf, have something like: 

---%<-------------------------------------------------------------------------
auth default {
..
  passdb pam {
  }
  passdb sql {
    args = /etc/dovecot-sql-master.conf
  }
..
}
---%<-------------------------------------------------------------------------

One way to do this without SQL is to create a >>passwd-file<< containing every user: 

---%<-------------------------------------------------------------------------
user1:{plain}master-password
user2:{plain}master-password
..etc..
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2007-12-11 04:42)
