Security-Enhanced Linux secures the sshd processes via flexible mandatory access control.
The sshd processes execute with the sshd_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 sshd_t
The sshd_t SELinux type can be entered via the sshd_exec_t file type.
The default entrypoint paths for the sshd_t domain are the following:
/usr/sbin/sshd, /usr/sbin/gsisshd
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux sshd policy is very flexible allowing users to setup their sshd processes in as secure a method as possible.
The following process types are defined for sshd:
sshd_t, sshd_sandbox_t, sshd_net_t, ssh_keygen_t, sshd_keygen_t, ssh_t, ssh_keysign_t
Note: semanage permissive -a sshd_t can be used to make the process type sshd_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 ssh logins as sysadm_r:sysadm_t, you must turn on the ssh_sysadm_login boolean. Disabled by default.
setsebool -P ssh_sysadm_login 1
If you want to allow sshd to use tcp wrappers, you must turn on the ssh_use_tcpd boolean. Disabled by default.
setsebool -P ssh_use_tcpd 1
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
If you want to enable polyinstantiated directory support, you must turn on the polyinstantiation_enabled boolean. Disabled by default.
setsebool -P polyinstantiation_enabled 1
You can see the types associated with a port by using the following command:
semanage port -l
Policy governs the access confined processes have to these ports. SELinux sshd policy is very flexible allowing users to setup their sshd processes in as secure a method as possible.
The following port types are defined for sshd:
Default Defined Ports: tcp 8888,22
The SELinux process type sshd_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.
auth_cache_t
/var/cache/coolkey(/.*)?
auth_home_t
/root/.yubico(/.*)?
/root/.google_authenticator
/root/.google_authenticator~
/home/[^/]+/.yubico(/.*)?
/home/[^/]+/.google_authenticator
/home/[^/]+/.google_authenticator~
cgroup_t
/sys/fs/cgroup
cifs_t
cluster_conf_t
/etc/cluster(/.*)?
cluster_var_lib_t
/var/lib/pcsd(/.*)?
/var/lib/cluster(/.*)?
/var/lib/openais(/.*)?
/var/lib/pengine(/.*)?
/var/lib/corosync(/.*)?
/usr/lib/heartbeat(/.*)?
/var/lib/heartbeat(/.*)?
/var/lib/pacemaker(/.*)?
cluster_var_run_t
/var/run/crm(/.*)?
/var/run/cman_.*
/var/run/rsctmp(/.*)?
/var/run/aisexec.*
/var/run/heartbeat(/.*)?
/var/run/corosync-qnetd(/.*)?
/var/run/corosync-qdevice(/.*)?
/var/run/corosync.pid
/var/run/cpglockd.pid
/var/run/rgmanager.pid
/var/run/cluster/rgmanager.sk
condor_var_lib_t
/var/lib/condor(/.*)?
/var/lib/condor/spool(/.*)?
/var/lib/condor/execute(/.*)?
ecryptfs_t
/home/[^/]+/.Private(/.*)?
/home/[^/]+/.ecryptfs(/.*)?
faillog_t
/var/log/btmp.*
/var/log/faillog.*
/var/log/tallylog.*
/var/run/faillock(/.*)?
fusefs_t
/var/run/user/[^/]*/gvfs
gitosis_var_lib_t
/srv/lib/gitosis(/.*)?
/var/lib/gitosis(/.*)?
/var/lib/gitolite(3)?(/.*)?
initrc_var_run_t
/var/run/utmp
/var/run/random-seed
/var/run/runlevel.dir
/var/run/setmixer_flag
kdbusfs_t
krb5_host_rcache_t
/var/cache/krb5rcache(/.*)?
/var/tmp/nfs_0
/var/tmp/DNS_25
/var/tmp/host_0
/var/tmp/imap_0
/var/tmp/HTTP_23
/var/tmp/HTTP_48
/var/tmp/ldap_55
/var/tmp/ldap_487
/var/tmp/ldapmap1_0
lastlog_t
/var/log/lastlog.*
nfs_t
openshift_tmp_t
/var/lib/openshift/.*/.tmp(/.*)?
/var/lib/openshift/.*/.sandbox(/.*)?
/var/lib/stickshift/.*/.tmp(/.*)?
/var/lib/stickshift/.*/.sandbox(/.*)?
pam_var_run_t
/var/(db|adm)/sudo(/.*)?
/var/lib/sudo(/.*)?
/var/run/sudo(/.*)?
/var/run/motd.d(/.*)?
/var/run/sepermit(/.*)?
/var/run/pam_mount(/.*)?
/var/run/motd
root_t
/sysroot/ostree/deploy/.*-atomic/deploy(/.*)?
/
/initrd
security_t
/selinux
ssh_home_t
/var/lib/[^/]+/.ssh(/.*)?
/root/.ssh(/.*)?
/var/lib/one/.ssh(/.*)?
/var/lib/pgsql/.ssh(/.*)?
/var/lib/openshift/[^/]+/.ssh(/.*)?
/var/lib/amanda/.ssh(/.*)?
/var/lib/stickshift/[^/]+/.ssh(/.*)?
/var/lib/gitolite/.ssh(/.*)?
/var/lib/nocpulse/.ssh(/.*)?
/var/lib/gitolite3/.ssh(/.*)?
/var/lib/openshift/gear/[^/]+/.ssh(/.*)?
/root/.shosts
/home/[^/]+/.ssh(/.*)?
/home/[^/]+/.ansible/cp/.*
/home/[^/]+/.shosts
sshd_var_run_t
/var/run/sshd.pid
/var/run/sshd.init.pid
systemd_passwd_var_run_t
/var/run/systemd/ask-password(/.*)?
/var/run/systemd/ask-password-block(/.*)?
user_tmp_t
/dev/shm/mono.*
/var/run/user(/.*)?
/tmp/.ICE-unix(/.*)?
/tmp/.X11-unix(/.*)?
/dev/shm/pulse-shm.*
/tmp/.X0-lock
/tmp/hsperfdata_root
/var/tmp/hsperfdata_root
/home/[^/]+/tmp
/home/[^/]+/.tmp
/tmp/gconfd-[^/]+
user_tmp_type
all user tmp files
var_auth_t
/var/ace(/.*)?
/var/rsa(/.*)?
/var/lib/abl(/.*)?
/var/lib/rsa(/.*)?
/var/lib/pam_ssh(/.*)?
/var/run/pam_ssh(/.*)?
/var/lib/pam_shield(/.*)?
/var/opt/quest/vas/vasd(/.*)?
/var/lib/google-authenticator(/.*)?
wtmp_t
/var/log/wtmp.*
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 sshd policy is very flexible allowing users to setup their sshd processes in as secure a method as possible.
STANDARD FILE CONTEXT
SELinux defines the file context types for the sshd, 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 sshd_keytab_t '/srv/mysshd_content(/.*)?'
restorecon -R -v /srv/mysshd_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for sshd:
sshd_exec_t
- Set files with the sshd_exec_t type, if you want to transition an executable to the sshd_t domain.
sshd_initrc_exec_t
- Set files with the sshd_initrc_exec_t type, if you want to transition an executable to the sshd_initrc_t domain.
sshd_key_t
- Set files with the sshd_key_t type, if you want to treat the files as sshd key data.
sshd_keygen_exec_t
- Set files with the sshd_keygen_exec_t type, if you want to transition an executable to the sshd_keygen_t domain.
sshd_keygen_unit_file_t
- Set files with the sshd_keygen_unit_file_t type, if you want to treat the files as sshd keygen unit content.
sshd_keytab_t
- Set files with the sshd_keytab_t type, if you want to treat the files as kerberos keytab files.
sshd_tmpfs_t
- Set files with the sshd_tmpfs_t type, if you want to store sshd files on a tmpfs file system.
sshd_unit_file_t
- Set files with the sshd_unit_file_t type, if you want to treat the files as sshd unit content.
sshd_var_run_t
- Set files with the sshd_var_run_t type, if you want to store the sshd 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 port can also be used to manipulate the port definitions
semanage boolean can also be used to manipulate the booleans
system-config-selinux is a GUI tool available to customize SELinux policy settings.