I'm in a situation here at work where I'm trying to support a mixed network of OS X and RHEL desktop machines with a Postfix/Dovecot combination.
- user account information is stored in LDAP
- user credentials are in MIT Kerberos
- server is running RHEL 6/Dovecot 2.0.9/Postfix 2.6.6
I am currently using the PAM passdb module to authenticate my users (I began to have trouble with using GSSAPI directly). After I implemented it, a few weeks later, I noticed that some users were no longer getting their mail if they hadn't logged in during the past day. Postfix's mailq showed that hundreds of messages were backing up in the queue. I eventually tracked it down to leftover Kerberos credential cache files (/tmp/krb5cc_????) sitting in /tmp on the mail server. The presence of expired credential files was preventing Postfix from delivering mail to those users' mail spools. If I delete the credential files manually, Postfix immediately delivers the queued emails.
Currently, I have a cron job deleting the files manually every night. Obviously, this is a cruddy solution. I have Dovecot configured on a RHEL 6 box. The Pam stack on a RHEL 6 machine uses sssd (pam_sss.so) for authentication with Kerberos, not pam_krb5.so. I'm trying to track down which piece of the puzzle is responsible for cleaning up leftover credential caches. Is there a configuration option I can pass to Dovecot's passdb directly to clean up these cache files? Do others generally have more success using a custom PAM stack with pam_krb5.so instead of pam_sss.so? Poring over sssd's configuration options didn't reveal anything useful. I'm still not sure why Postfix even cares if there are expired credential cache files in /tmp at all.
I'm back to trying GSSAPI directly again as well in the meantime on a few test clients. When I used that in the past, users were getting issued duplicate Kerberos tickets and users were forced to log into the mail server directly using SSH after a day in order to get their mail to work (seemingly a related issue). If I get those same errors again, I'll start another thread.
The output of doveconf -N:
# 2.0.9: /etc/dovecot/dovecot.conf # OS: Linux 2.6.32-279.14.1.el6.x86_64 x86_64 Red Hat Enterprise Linux Server release 6.3 (Santiago) ext4 auth_cache_size = 10 k auth_cache_ttl = 5 hours auth_default_realm = server.com auth_gssapi_hostname = hostname.server.com auth_krb5_keytab = /etc/dovecot/dovecot.keytab auth_mechanisms = gssapi plain auth_realms = server.com auth_username_format = %n auth_verbose = no disable_plaintext_auth = yes listen = * mail_location = maildir:/var/spool/mail/%u mail_privileged_group = mail mbox_read_locks = fcntl mbox_write_locks = fcntl namespace { inbox = yes location = prefix = separator = / type = private } passdb { driver = pam } protocols = pop3 imap service auth { unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0666 user = postfix } } ssl = yes ssl_cert = </usr/share/ssl/private/mail.server.com.pem ssl_key = </usr/share/ssl/private/mail.server.com.pem userdb { driver = passwd } protocol imap { imap_client_workarounds = tb-extra-mailbox-sep mail_plugins = " listescape" }
Thanks for any pointers, Maura Dailey maura@eclipse.ncsc.mil