Prefetch User Database
======================

Prefetch userdb can be used to combine passdb and userdb lookups into a single
lookup. It's usually used with <SQL> [AuthDatabase.SQL.txt], <LDAP>
[AuthDatabase.LDAP.txt] and <checkpassword>
[PasswordDatabase.CheckPassword.txt] passdbs.

Prefetch basically works by requiring that the passdb returns the userdb
information in <extra fields> [PasswordDatabase.ExtraFields.txt] with 'userdb_'
prefixes. For example if a userdb typically returns 'uid', 'gid' and 'home'
fields, the passdb would have to return 'userdb_uid', 'userdb_gid' and
'userdb_home' fields.

If you're using <LDA.txt> or <LMTP.txt>, you still need a valid userdb which
can be used to locate the users. You can do this by adding a normal SQL/LDAP
userdb *after the userdb prefetch*. The order of definitions is significant.
See below for examples.

LDAP: 'auth_bind=yes' with 'auth_bind_userdn'-template is incompatible with
prefetch, because no passdb lookup is done then. If you want zero LDAP lookups,
you might want to use <static userdb> [UserDatabase.Static.txt] instead of
prefetch.

SQL example
-----------

'dovecot.conf':

---%<-------------------------------------------------------------------------
passdb {
  driver = sql
  args = /etc/dovecot/dovecot-sql.conf.ext
}
userdb {
  driver = prefetch
}
# The userdb below is used only by lda.
userdb {
  driver = sql
  args = /etc/dovecot/dovecot-sql.conf.ext
}
---%<-------------------------------------------------------------------------

'dovecot-sql.conf.ext':

---%<-------------------------------------------------------------------------
password_query = SELECT userid AS user, password, \
  home AS userdb_home, uid AS userdb_uid, gid AS userdb_gid \
  FROM users \
  WHERE userid = '%u'

# For LDA:
user_query = SELECT home, uid, gid FROM users WHERE userid = '%u'
---%<-------------------------------------------------------------------------

LDAP example
------------

'dovecot.conf':

---%<-------------------------------------------------------------------------
passdb {
  driver = ldap
  args = /etc/dovecot/dovecot-ldap.conf.ext
}
userdb {
  driver = prefetch
}
# The userdb below is used only by LDA.
userdb {
  driver = ldap
  args = /etc/dovecot/dovecot-ldap.conf.ext
}
---%<-------------------------------------------------------------------------

'dovecot-ldap.conf.ext':

---%<-------------------------------------------------------------------------
pass_attrs = uid=user, userPassword=password, \
  homeDirectory=userdb_home, uidNumber=userdb_uid, gidNumber=userdb_gid

# For LDA:
user_attrs = homeDirectory=home, uidNumber=uid, gidNumber=gid
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2019-06-19 12:42)
