Security-Enhanced Linux secures the xdm processes via flexible mandatory access control.
The xdm processes execute with the xdm_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 xdm_t
The xdm_t SELinux type can be entered via the xdm_exec_t file type.
The default entrypoint paths for the xdm_t domain are the following:
/usr/s?bin/nodm, /usr/s?bin/gdm(3)?, /usr/s?bin/lightdm*, /usr/s?bin/[mxgkw]dm, /usr/s?bin/gdm-binary, /usr/s?bin/lxdm(-binary)?, /usr/X11R6/bin/[xgkw]dm, /usr/bin/razor-lightdm-.*, /usr/bin/sddm, /usr/bin/slim, /usr/bin/gpe-dm, /opt/kde3/bin/kdm, /usr/sbin/mdm-binary, /usr/bin/sddm-greeter, /etc/rc.d/init.d/x11-common, /usr/libexec/gdm-disable-wayland
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux xdm policy is very flexible allowing users to setup their xdm processes in as secure a method as possible.
The following process types are defined for xdm:
xdm_t, xdm_unconfined_t
Note: semanage permissive -a xdm_t can be used to make the process type xdm_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated.
If you want to allows xdm_t to bind on vnc_port_t(5910), you must turn on the xdm_bind_vnc_tcp_port boolean. Disabled by default.
setsebool -P xdm_bind_vnc_tcp_port 1
If you want to allow the graphical login program to execute bootloader, you must turn on the xdm_exec_bootloader boolean. Disabled by default.
setsebool -P xdm_exec_bootloader 1
If you want to allow the graphical login program to login directly as sysadm_r:sysadm_t, you must turn on the xdm_sysadm_login boolean. Disabled by default.
setsebool -P xdm_sysadm_login 1
If you want to allow the graphical login program to create files in HOME dirs as xdm_home_t, you must turn on the xdm_write_home boolean. Disabled by default.
setsebool -P xdm_write_home 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 deny user domains applications to map a memory region as both executable and writable, this is dangerous and the executable should be reported in bugzilla, you must turn on the deny_execmem boolean. Disabled by default.
setsebool -P deny_execmem 1
If you want to deny any process from ptracing or debugging any other processes, you must turn on the deny_ptrace boolean. Disabled by default.
setsebool -P deny_ptrace 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
If you want to allow unconfined executables to make their stack executable. This should never, ever be necessary. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla, you must turn on the selinuxuser_execstack boolean. Enabled by default.
setsebool -P selinuxuser_execstack 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
If you want to support fusefs home directories, you must turn on the use_fusefs_home_dirs boolean. Disabled by default.
setsebool -P use_fusefs_home_dirs 1
If you want to support NFS home directories, you must turn on the use_nfs_home_dirs boolean. Disabled by default.
setsebool -P use_nfs_home_dirs 1
If you want to support SAMBA home directories, you must turn on the use_samba_home_dirs boolean. Disabled by default.
setsebool -P use_samba_home_dirs 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 xdm policy is very flexible allowing users to setup their xdm processes in as secure a method as possible.
The following port types are defined for xdm:
Default Defined Ports: tcp 177 udp 177
The SELinux process type xdm_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
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
dosfs_t
ecryptfs_t
/home/[^/]+/.Private(/.*)?
/home/[^/]+/.ecryptfs(/.*)?
etc_runtime_t
/[^/]+
/etc/mtab.*
/etc/blkid(/.*)?
/etc/nologin.*
/etc/.fstab.hal..+
/halt
/fastboot
/poweroff
/.autofsck
/etc/cmtab
/forcefsck
/.suspended
/fsckoptions
/.autorelabel
/etc/.updated
/var/.updated
/etc/killpower
/etc/nohotplug
/etc/securetty
/etc/ioctl.save
/etc/fstab.REVOKE
/etc/network/ifstate
/etc/sysconfig/hwconf
/etc/ptal/ptal-printd-like
/etc/sysconfig/iptables.save
/etc/xorg.conf.d/00-system-setup-keyboard.conf
/etc/X11/xorg.conf.d/00-system-setup-keyboard.conf
faillog_t
/var/log/btmp.*
/var/log/faillog.*
/var/log/tallylog.*
/var/run/faillock(/.*)?
fonts_cache_t
/var/cache/fontconfig(/.*)?
fusefs_t
/var/run/user/[^/]*/gvfs
gconf_home_t
/root/.local.*
/root/.gconf(d)?(/.*)?
/home/[^/]+/.local.*
/home/[^/]+/.gconf(d)?(/.*)?
gnome_home_type
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.*
locale_t
/etc/locale.conf
/etc/vconsole.conf
/usr/lib/locale(/.*)?
/usr/share/locale(/.*)?
/usr/share/zoneinfo(/.*)?
/usr/share/X11/locale(/.*)?
/etc/timezone
/etc/localtime
/etc/sysconfig/clock
/etc/avahi/etc/localtime
/var/empty/sshd/etc/localtime
/var/named/chroot/etc/localtime
/var/spool/postfix/etc/localtime
nfs_t
pam_var_console_t
/var/run/console(/.*)?
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
security_t
/selinux
sysfs_t
/sys(/.*)?
systemd_passwd_var_run_t
/var/run/systemd/ask-password(/.*)?
/var/run/systemd/ask-password-block(/.*)?
user_fonts_t
/root/.fonts(/.*)?
/tmp/.font-unix(/.*)?
/home/[^/]+/.fonts(/.*)?
/home/[^/]+/.local/share/fonts(/.*)?
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.*
xauth_home_t
/root/.Xauth.*
/root/.xauth.*
/root/.Xauthority.*
/root/.serverauth.*
/var/lib/pqsql/.xauth.*
/var/lib/pqsql/.Xauthority.*
/var/lib/nxserver/home/.xauth.*
/var/lib/nxserver/home/.Xauthority.*
/home/[^/]+/.Xauth.*
/home/[^/]+/.xauth.*
/home/[^/]+/.Xauthority.*
/home/[^/]+/.serverauth.*
xdm_home_t
/root/.dmrc.*
/root/.wayland-errors.*
/root/.xsession-errors.*
/home/[^/]+/.dmrc.*
/home/[^/]+/.cache/gdm(/.*)?
/home/[^/]+/.wayland-errors.*
/home/[^/]+/.xsession-errors.*
/home/[^/]+/.local/share/xorg(/.*)?
xdm_lock_t
xdm_log_t
/var/log/[mkwx]dm.log.*
/var/log/mdm(/.*)?
/var/log/lxdm.log.*
/var/log/slim.log.*
xdm_rw_etc_t
/etc/X11/wdm(/.*)?
/etc/opt/VirtualGL(/.*)?
xdm_spool_t
/var/spool/[mg]dm(/.*)?
xdm_tmpfs_t
xdm_var_lib_t
/var/lib/[mxkwg]dm(/.*)?
/var/cache/[mg]dm(/.*)?
/var/lib/gdm(3)?(/.*)?
/var/lib/lxdm(/.*)?
/var/lib/sddm(/.*)?
/var/lib/lightdm(/.*)?
/var/cache/lightdm(/.*)?
/var/lib/lightdm-data(/.*)?
xdm_var_run_t
/etc/kde[34]?/kdm/backgroundrc
/var/run/[kgm]dm(/.*)?
/var/run/gdm(3)?.pid
/var/run/gdm(3)?(/.*)?
/usr/lib/qt-.*/etc/settings(/.*)?
/var/run/slim.*
/var/run/lxdm(/.*)?
/var/run/sddm(/.*)?
/var/run/xauth(/.*)?
/var/run/xdmctl(/.*)?
/var/run/lightdm(/.*)?
/var/run/systemd/multi-session-x(/.*)?
/var/run/xdm.pid
/var/run/lxdm.pid
/var/run/lxdm.auth
/var/run/gdm_socket
xkb_var_lib_t
/var/lib/xkb(/.*)?
/usr/X11R6/lib/X11/xkb/.*
/usr/X11R6/lib/X11/xkb
xserver_log_t
/var/[xgkw]dm(/.*)?
/usr/var/[xgkw]dm(/.*)?
/var/log/gdm(3)?(/.*)?
/var/log/Xorg.*
/var/log/XFree86.*
/var/log/lightdm(/.*)?
/var/log/nvidia-installer.log.*
xserver_tmpfs_t
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 xdm policy is very flexible allowing users to setup their xdm processes in as secure a method as possible.
EQUIVALENCE DIRECTORIES
xdm policy stores data with multiple different file context types under the /var/lib/lightdm directory. If you would like to store the data in a different directory you can use the semanage command to create an equivalence mapping. If you wanted to store this data under the /srv dirctory you would execute the following command:
semanage fcontext -a -e /var/lib/lightdm /srv/lightdm
restorecon -R -v /srv/lightdm
xdm policy stores data with multiple different file context types under the /var/run/gdm(3)? directory. If you would like to store the data in a different directory you can use the semanage command to create an equivalence mapping. If you wanted to store this data under the /srv dirctory you would execute the following command:
semanage fcontext -a -e /var/run/gdm(3)? /srv/gdm(3)?
restorecon -R -v /srv/gdm(3)?
xdm policy stores data with multiple different file context types under the /var/run/lxdm directory. If you would like to store the data in a different directory you can use the semanage command to create an equivalence mapping. If you wanted to store this data under the /srv dirctory you would execute the following command:
semanage fcontext -a -e /var/run/lxdm /srv/lxdm
restorecon -R -v /srv/lxdm
STANDARD FILE CONTEXT
SELinux defines the file context types for the xdm, 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 xdm_log_t '/srv/myxdm_content(/.*)?'
restorecon -R -v /srv/myxdm_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for xdm:
xdm_etc_t
- Set files with the xdm_etc_t type, if you want to store xdm files in the /etc directories.
xdm_exec_t
- Set files with the xdm_exec_t type, if you want to transition an executable to the xdm_t domain.
xdm_home_t
- Set files with the xdm_home_t type, if you want to store xdm files in the users home directory.
xdm_lock_t
- Set files with the xdm_lock_t type, if you want to treat the files as xdm lock data, stored under the /var/lock directory
xdm_log_t
- Set files with the xdm_log_t type, if you want to treat the data as xdm log data, usually stored under the /var/log directory.
xdm_rw_etc_t
- Set files with the xdm_rw_etc_t type, if you want to store xdm rw files in the /etc directories.
xdm_spool_t
- Set files with the xdm_spool_t type, if you want to store the xdm files under the /var/spool directory.
xdm_tmpfs_t
- Set files with the xdm_tmpfs_t type, if you want to store xdm files on a tmpfs file system.
xdm_unconfined_exec_t
- Set files with the xdm_unconfined_exec_t type, if you want to transition an executable to the xdm_unconfined_t domain.
xdm_var_lib_t
- Set files with the xdm_var_lib_t type, if you want to store the xdm files under the /var/lib directory.
xdm_var_run_t
- Set files with the xdm_var_run_t type, if you want to store the xdm 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.