guest_u is an SELinux User defined in the SELinux policy. SELinux users have default roles, guest_r. The default role has a default type, guest_t, associated with it.
The SELinux user will usually login to a system with a context that looks like:
guest_u:guest_r:guest_t:s0-s0:c0.c1023
Linux users are automatically assigned an SELinux users at login. Login programs use the SELinux User to assign initial context to the user's shell.
SELinux policy uses the context to control the user's access.
By default all users are assigned to the SELinux user via the __default__ flag
On Targeted policy systems the __default__ user is assigned to the unconfined_u SELinux user.
You can list all Linux User to SELinux user mapping using:
semanage login -l
If you wanted to change the default user mapping to use the guest_u user, you would execute:
semanage login -m -s guest_u __default__
If you want to map the one Linux user (joe) to the SELinux user guest, you would execute:
$ semanage login -a -s guest_u joe
The SELinux user guest_u is defined in policy as a unprivileged user. SELinux prevents unprivileged users from doing administration tasks without transitioning to a different role.
The SELinux user guest_u is not able to X Windows login.
dns_port_t: 53
ocsp_port_t: 9080
kerberos_port_t: 88,750,4444
dns_port_t: 53
ocsp_port_t: 9080
kerberos_port_t: 88,750,4444
If you want to allow xguest users to configure Network Manager and connect to apache ports, you must turn on the xguest_connect_network boolean.
setsebool -P xguest_connect_network 1
If you want to allow xguest users to mount removable media, you must turn on the xguest_mount_media boolean.
setsebool -P xguest_mount_media 1
If you want to allow xguest to use blue tooth devices, you must turn on the xguest_use_bluetooth boolean.
setsebool -P xguest_use_bluetooth 1
The SELinux user guest_u is able execute home content files.
Three things can happen when guest_t attempts to execute a program.
1. SELinux Policy can deny guest_t from executing the program.
Execute the following to see the types that the SELinux user guest_t can execute without transitioning:
sesearch -A -s guest_t -c file -p execute_no_trans
Execute the following to see the types that the SELinux user guest_t can execute and transition:
$ sesearch -A -s guest_t -c process -p transition
The SELinux user type guest_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(/.*)?
httpd_user_content_t
/home/[^/]*/((www)|(web)|(public_html))(/.+)?
httpd_user_htaccess_t
/home/[^/]*/((www)|(web)|(public_html))(/.*)?/.htaccess
httpd_user_ra_content_t
/home/[^/]*/((www)|(web)|(public_html))(/.*)?/logs(/.*)?
httpd_user_rw_content_t
httpd_user_script_exec_t
/home/[^/]*/((www)|(web)|(public_html))/cgi-bin(/.+)?
user_home_type