Security-Enhanced Linux secures the postfix_smtp processes via flexible mandatory access control.
The postfix_smtp processes execute with the postfix_smtp_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 postfix_smtp_t
The postfix_smtp_t SELinux type can be entered via the postfix_smtp_exec_t file type.
The default entrypoint paths for the postfix_smtp_t domain are the following:
/usr/libexec/postfix/lmtp, /usr/libexec/postfix/smtp, /usr/libexec/postfix/scache
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux postfix_smtp policy is very flexible allowing users to setup their postfix_smtp processes in as secure a method as possible.
The following process types are defined for postfix_smtp:
postfix_smtp_t, postfix_smtpd_t
Note: semanage permissive -a postfix_smtp_t can be used to make the process type postfix_smtp_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 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
The SELinux process type postfix_smtp_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
postfix_prng_t
/etc/postfix/prng_exch
postfix_smtp_tmp_t
postfix_spool_t
/var/spool/postfix.*
/var/spool/postfix/defer(/.*)?
/var/spool/postfix/flush(/.*)?
/var/spool/postfix/deferred(/.*)?
/var/spool/postfix/maildrop(/.*)?
postfix_var_run_t
/var/spool/postfix/pid/.*
You can see the context of a file using the -Z option to lsP Policy governs the access confined processes have to these files. SELinux postfix_smtp policy is very flexible allowing users to setup their postfix_smtp processes in as secure a method as possible.
STANDARD FILE CONTEXT
SELinux defines the file context types for the postfix_smtp, if you wanted to store files with these types in a diffent paths, you need to execute the semanage command to sepecify alternate labeling and then use restorecon to put the labels on disk.
semanage fcontext -a -t postfix_smtpd_tmp_t '/srv/mypostfix_smtp_content(/.*)?'
restorecon -R -v /srv/mypostfix_smtp_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for postfix_smtp:
postfix_smtp_exec_t
- Set files with the postfix_smtp_exec_t type, if you want to transition an executable to the postfix_smtp_t domain.
postfix_smtp_tmp_t
- Set files with the postfix_smtp_tmp_t type, if you want to store postfix smtp temporary files in the /tmp directories.
postfix_smtpd_exec_t
- Set files with the postfix_smtpd_exec_t type, if you want to transition an executable to the postfix_smtpd_t domain.
postfix_smtpd_tmp_t
- Set files with the postfix_smtpd_tmp_t type, if you want to store postfix smtpd temporary files in the /tmp directories.
Note: File context can be temporarily modified with the chcon command. If you want to permanently change the file context you need to use the semanage fcontext command. This will modify the SELinux labeling database. You will need to use restorecon to apply the labels.
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.