Hi all,

I have a setup of some nodes running Dovecot 2.0.13 and Postfix 2.5.6 with storage in NFS and authentication happening with PAM.

Poking around in the wiki, I tried out different possibilities but now I am stuck -- and are hoping for your (enlightening) comments and tips.

My planned setup for IMAP and LMTP is like this:

IMAP

1. A loadbalancer directs new sessions to a Dovecot-Director instance; this extra amount of traffic routing is mostly done for automatic handling in case of a failing Director node; this works fine, the same IP will end always on the same backend, but user-based Directory proxying seems more appropriate, especially taking the NFS-setup and the delivery process into account

2. Then the Director decides where to direct the user's session; this works fine when I let the backend servers do the authentication work

3. The backend Dovecot server will happily provide the user's e-mail

For now my section for the passdb in the Director instance is

passdb { driver = static args = proxy=y nopassword=y }

So the backend will do the authentication of the session. But this setup inhibits using Kerberos, as the TGT is not forwarded to the backend server.

I would very much like to provide GSSAPI/Kerberos authentication, which already works fine with the backend servers being directly connected by mail clients. The backend servers are using the PAM driver.

I could not figure out, how to setup the passdb entry for the director instance to use PAM (this way enabling GSSAPI/Kerberos) and also giving back the necessary "proxy=y" to make director proxying the IMAP session.

Is this setup feasible at all?

LMTP

1. Postfix accepts incoming e-mail and decides, which e-mail will go the LMTP-way to be deliverd into a Dovecot mailbox with something like

   virtual_transport = lmtp:inet:DOVECOT-DIRECTORS-IP:LMTP-PORT-ABC

2. the Dovecot Director instance accepts the LMTP connections and will proxy this to the appropriate==user's current backend server

For now Postfix delivers e-mails using LMTP to the _backend_ w/o proxying and everything like SIEVE-filtering works fine:

virtual_transport = lmtp:inet:DOVECOT-BACKENDS-IP:LMTP-PORT-XYZ

But when I use the Director's IP/Port combination for LMTP, I see an error "554 5.4.6 <the@addr.ess> Proxying loops to itself".

Where may I specify the port number of the backend server's LMTP-port? I suspect that the missing port number implies that the receiving LMTP-backend server uses the same port and so this would lead to a loop, hence the loop error?!

I browsed the Wiki and the archives but still cannot find the information I am looking for.

Any hints on that?

Cheers, Dirk

And here's the director.conf (via doveconf -n):

# 2.0.13: /dovecot/code/etc/dovecot-director/director.conf # OS: SunOS 5.10 sun4v auth_debug = yes auth_verbose = yes base_dir = /var/run/director/ debug_log_path = /var/adm/dovecot-director.debug director_mail_servers = <LOCAL-BACKEND-IP> director_servers = <PUBLIC-DIRECTOR-IP> lmtp_proxy = yes login_greeting = Dovecot Director ready. mail_debug = yes managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date

passdb { args = proxy=y nopassword=y driver = static }

protocols = imap lmtp

service auth-worker { user = root }

service auth { client_limit = 6000 unix_listener auth-userdb { mode = 0644 user = vmail } }

service director { fifo_listener login/proxy-notify { mode = 0666 } inet_listener { port = 9090 } unix_listener director-userdb { mode = 0600 } unix_listener login/director { mode = 0666 } }

service imap-login { executable = imap-login director inet_listener imap { port = 10143 } inet_listener imaps { port = 10993 ssl = yes } process_min_avail = 1 }

service imap { process_limit = 1024 }

service lmtp { inet_listener lmtp { address = <LOCAL-DIRECTOR-IP> port = 24242 } }

ssl_cert = </dovecot/code/dovecot-homedir/dovecot.crt ssl_key = </dovecot/code/dovecot-homedir/dovecot.key

syslog_facility = local0

protocol lmtp { auth_socket_path = director-userdb }

-- Dirk Jahnke-Zumbusch Deutsches Elektronen-Synchrotron DESY IT Information Fabrics Member of the Helmholtz Association D-22603 Hamburg Notkestrasse 85 / 22607 Hamburg T: +49-40-899.81760 F: +49-40-899.41760 dirk.jahnke-zumbusch@desy.de