I am trying to add/make a new security policy for the courier mail 
server.  Sendmail is easy compared with qmail or courier.  This will 
also be a good learning experiance for me (and others) to go through the 
thinking behind creating a security policy.    I am not a courier 
expert,   but I think selinux and courier would be good togther.

courier stuff
See http://www.nsa.gov/selinux/doc/policy/policy.html
I was think about at least three domains for smtp.  One for the input 
modules, one for submit/courierd, and one for the output modules.  The 
issues here are we want to isolate any IO modules from the queue AND 
isolate any modules that have suid.
What I need to know is which executable accesses what files/dirs?
What are the transitions,  what modules call/execute what other modules?
A state diagram of the basic courier process would be great?

I the FUTURE I would want to add TLS certs auth, the pop3 and imap 
daemons with auth,  and then the web configuration and web email.  

I courier does have selinux support then it could become one of the most 
secure mail systems.


selinux stuff
The problem is how fine grained a security policy I should make?
Should every processes have a seperate policy or should the whole 
package be one security?
Should the certs be protected more than other parts?
Courier writes to the users Maildir in their home dir, only 
courier_local writes to users dir.  ????



Background:
Courier is a all inclusive mails server.  It is like qmail with 
different processes doing different tasks. It also has imap,pop3 secure 
imap,pop3 also.  It has a web interface to help with configuration.  And 
webmail client.

File structure
/etc/courier                courier_conf_t        configuration files

/var/spool/courier      courier_spool_t      spool directories for courier
/var/spool/courier/msgq    courier_msgq_t
/var/spool/courier/msgs     courier_msgs_t
/var/spool/courier/authdaemon

/usr/lib/courier          courier_t                 courier
/usr/lib/courier/bin    courier_bin_t
/usr/lib/courier/sbin   courier_sbin_t
/usr/lib/courier/share  courier_share_t
/usr/lib/courier/share/rootcerts    courier_certs_t               esmtp, 
imap, pop3 certs for SSL
/usr/lib/courier/share/htmldoc

Running processes:

courierd            main daemon            courier_daemon_t
courierXXXX   transport daemons    courier_trans_t
courieresmtp    input daemon             courier_esmtp_t
authdaemon      authorize connections courier_auth_t
couriertcpd       courier tcpd                  courier_tcpd_t
pop3d, pop3d-ssl, imapd, imapd-ssl       courier_XXXX_t
courierfilter      spam killer   (not used now)  courier_filter_t








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