Trouble with case-sensitive LDAP user logins to Dovecot

Question

I asked this to the dovecot list to no avail, so will try here too. Please forgive the crosspost.

I have a client running Dovecot-Postfix on Debian Squeeze. I'm using Dovecot from the Squeeze repository.

# dovecot --version
1.2.15

I've implemented a central mail_location and am using one vmail user, as I thought this would be be the best approach for when it came time to implement Shared and Public Mailboxes.

# dovecot -n
# 1.2.15: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.32-5-xen-686 i686 Debian 6.0.7 ext3
log_timestamp: %Y-%m-%d %H:%M:%S 
protocols: imap imaps pop3s managesieve
listen(default): 127.0.0.1:143
listen(imap): 127.0.0.1:143
listen(pop3): 127.0.0.1:110
listen(managesieve): *
ssl_listen(default): *:993
ssl_listen(imap): *:993
ssl_listen(pop3): *:995
ssl_listen(managesieve): 
ssl_ca_file: /etc/ssl/certs/RapidSSL_CA_bundle.pem
ssl_cert_file: /etc/ssl/certs/mail.example.com.2013.chain.pem
ssl_key_file: /etc/ssl/private/example.2013.key
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
login_executable(managesieve): /usr/lib/dovecot/managesieve-login
mail_max_userip_connections(default): 40
mail_max_userip_connections(imap): 40
mail_max_userip_connections(pop3): 10
mail_max_userip_connections(managesieve): 10
mail_privileged_group: mail
mail_uid: vmail
mail_gid: vmail
mail_location: maildir:/var/spool/dovecot/%d/%u
mbox_write_locks: fcntl dotlock
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_executable(managesieve): /usr/lib/dovecot/managesieve
mail_plugins(default): quota imap_quota
mail_plugins(imap): quota imap_quota
mail_plugins(pop3): 
mail_plugins(managesieve): 
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
mail_plugin_dir(managesieve): /usr/lib/dovecot/modules/managesieve
namespace:
 type: private
 separator: /
 inbox: yes
 list: yes
 subscriptions: yes
lda:
 postmaster_address: [email protected]
 mail_plugins: sieve quota
 log_path: /var/log/dovecot-deliver.log
 info_log_path: /var/log/dovecot-deliver.log
auth default:
 mechanisms: plain login
 passdb:
   driver: ldap
   args: /etc/dovecot/dovecot-ldap.conf
 userdb:
   driver: ldap
   args: /etc/dovecot/dovecot-ldap-userdb.conf
 socket:
   type: listen
   client:
     path: /var/spool/postfix/private/auth
     mode: 432
     user: postfix
     group: postfix
   master:
     path: /var/run/dovecot/auth-master
     mode: 384
     user: vmail
     group: vmail
plugin:
 quota: maildir:User
 quota_rule: *:storage=1200M
 quota_rule2: Deleted Messages:storage=10%%
 quota_rule3: Deleted Items:storage=10%%
 quota_rule4: Trash:storage=10%%
 sieve: /var/spool/sieve/%d/%u/.dovecot.sieve
 sieve_dir: /var/spool/sieve/%d/%u

All of the mail users are LDAP users only (not local UNIX users - not using nsswitch). dovecot-ldap-userdb.conf is a symbolic link to dovecot-ldap.conf

# grep -v '^ *\(#.*\)\?$' /etc/dovecot/dovecot-ldap.conf 
uris = ldaps://mail.example.com/
dn = uid=mail,ou=Services,dc=example,dc=com
dnpass = ******************
tls_require_cert = hard
auth_bind = yes
base = ou=People,dc=example,dc=com
user_attrs = quota=quota_rule=*:storage=%$M
user_filter = (&(objectClass=posixAccount)(mail=%u))
pass_attrs = uid=mail,userPassword=password
pass_filter = (&(objectClass=posixAccount)(mail=%u))

Now, mail addressed to [email protected] and [email protected] correctly gets delivered to the correct mail location of /var/spool/dovecot/example.com/user, but the problem occurs when the user creates their email account in an IMAP client with uppercase characters in their username, e.g. [email protected]. This creates a new directory at /var/spool/dovecot/exaMPLE.com/user, which never receives any mail. Is it possible to ignore the case the user enters in their mail client and always land them at the lowercase mail directory? Where would this be done?

Answer 1

You are using a very old version of Dovecot, almost three years out of date. I suggest you upgrade to a newer version, 2.2.5 is current. There have been made countless improvements and fixes from which your setup will surely profit.

That said, you should set auth_username_format = %Lu in dovecot.conf so that Dovecot translates the username to lower case before doing a lookup. This will normalize the usernames to lower case, no matter what the user sets in their mail client.

NB: lower-casing usernames is the default behaviour as of Dovecot 2.1.x.