Security-Enhanced Linux secures the sendmail processes via flexible mandatory access control.
The sendmail processes execute with the sendmail_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
ps -eZ | grep sendmail_t
The sendmail_t SELinux type can be entered via the mta_exec_type, sendmail_exec_t file types.
The default entrypoint paths for the sendmail_t domain are the following:
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux sendmail policy is very flexible allowing users to setup their sendmail processes in as secure a method as possible.
The following process types are defined for sendmail:
Note: semanage permissive -a sendmail_t can be used to make the process type sendmail_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 sendmail_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.
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 sendmail policy is very flexible allowing users to setup their sendmail processes in as secure a method as possible.
STANDARD FILE CONTEXT
SELinux defines the file context types for the sendmail, 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 sendmail_var_run_t '/srv/mysendmail_content(/.*)?'
restorecon -R -v /srv/mysendmail_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for sendmail:
- Set files with the sendmail_exec_t type, if you want to transition an executable to the sendmail_t domain.
- Set files with the sendmail_initrc_exec_t type, if you want to transition an executable to the sendmail_initrc_t domain.
- Set files with the sendmail_keytab_t type, if you want to treat the files as kerberos keytab files.
- Set files with the sendmail_log_t type, if you want to treat the data as sendmail log data, usually stored under the /var/log directory.
- Set files with the sendmail_tmp_t type, if you want to store sendmail temporary files in the /tmp directories.
- Set files with the sendmail_var_run_t type, if you want to store the sendmail files under the /run or /var/run directory.
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.