Security-Enhanced Linux secures the system_mail processes via flexible mandatory access control.
The system_mail processes execute with the system_mail_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
For example:
ps -eZ | grep system_mail_t
The system_mail_t SELinux type can be entered via the sendmail_exec_t file type.
The default entrypoint paths for the system_mail_t domain are the following:
/usr/sbin/sendmail(.sendmail)?, /usr/bin/esmtp, /usr/sbin/rmail, /usr/sbin/ssmtp, /usr/lib/sendmail, /usr/bin/esmtp-wrapper, /var/qmail/bin/sendmail, /usr/sbin/sendmail.postfix
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux system_mail policy is very flexible allowing users to setup their system_mail processes in as secure a method as possible.
The following process types are defined for system_mail:
system_mail_t
Note: semanage permissive -a system_mail_t can be used to make the process type system_mail_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated.
If you want to allow users to resolve user passwd entries directly from ldap rather then using a sssd server, you must turn on the authlogin_nsswitch_use_ldap boolean. Disabled by default.
setsebool -P authlogin_nsswitch_use_ldap 1
If you want to allow all domains to execute in fips_mode, you must turn on the fips_mode boolean. Enabled by default.
setsebool -P fips_mode 1
If you want to determine whether Gitosis can send mail, you must turn on the gitosis_can_sendmail boolean. Disabled by default.
setsebool -P gitosis_can_sendmail 1
If you want to allow http daemon to send mail, you must turn on the httpd_can_sendmail boolean. Disabled by default.
setsebool -P httpd_can_sendmail 1
If you want to allow confined applications to run with kerberos, you must turn on the kerberos_enabled boolean. Enabled by default.
setsebool -P kerberos_enabled 1
If you want to allow system to run with NIS, you must turn on the nis_enabled boolean. Disabled by default.
setsebool -P nis_enabled 1
If you want to allow confined applications to use nscd shared memory, you must turn on the nscd_use_shm boolean. Enabled by default.
setsebool -P nscd_use_shm 1
If you want to allow Redis to run redis-sentinal notification scripts, you must turn on the redis_enable_notify boolean. Disabled by default.
setsebool -P redis_enable_notify 1
If you want to support ecryptfs home directories, you must turn on the use_ecryptfs_home_dirs boolean. Disabled by default.
setsebool -P use_ecryptfs_home_dirs 1
The SELinux process type system_mail_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note the processes UID still need to have DAC permissions.
anon_inodefs_t
arpwatch_tmp_t
cifs_t
courier_spool_t
/var/spool/courier(/.*)?
/var/spool/authdaemon(/.*)?
ecryptfs_t
/home/[^/]+/.Private(/.*)?
/home/[^/]+/.ecryptfs(/.*)?
etc_aliases_t
/etc/mail/.*.db
/etc/mail/aliases.*
/etc/postfix/aliases.*
/etc/aliases
/etc/aliases.db
exim_log_t
/var/log/exim[0-9]?(/.*)?
exim_spool_t
/var/spool/exim[0-9]?(/.*)?
mail_home_rw_t
/root/Maildir(/.*)?
/root/.esmtp_queue(/.*)?
/var/lib/arpwatch/.esmtp_queue(/.*)?
/home/[^/]+/.maildir(/.*)?
/home/[^/]+/Maildir(/.*)?
/home/[^/]+/.esmtp_queue(/.*)?
mail_home_t
/root/.mailrc
/root/.esmtprc
/root/.forward
/root/dead.letter
/home/[^/]+/.forward[^/]*
/home/[^/]+/.mailrc
/home/[^/]+/.esmtprc
/home/[^/]+/dead.letter
mail_spool_t
/var/mail(/.*)?
/var/spool/imap(/.*)?
/var/spool/mail(/.*)?
/var/spool/smtpd(/.*)?
mqueue_spool_t
/var/spool/(client)?mqueue(/.*)?
/var/spool/mqueue.in(/.*)?
munin_var_lib_t
/var/lib/munin(/.*)?
nfs_t
qmail_spool_t
/var/qmail/queue(/.*)?
sendmail_log_t
/var/log/mail(/.*)?
/var/log/sendmail.st.*
system_mail_tmp_t
uucpd_spool_t
/var/spool/uucp(/.*)?
/var/spool/uucppublic(/.*)?
semanage permissive can also be used to manipulate whether or not a process type is permissive.
semanage module can also be used to enable/disable/install/remove policy modules.
semanage boolean can also be used to manipulate the booleans
system-config-selinux is a GUI tool available to customize SELinux policy settings.