On Thu, Jan 9, 2020 at 10:42 PM Dominick Grift <dac.override@xxxxxxxxx> wrote: > > On Thu, Jan 09, 2020 at 04:06:38PM -0500, Chris PeBenito wrote: > > I'd like to refine how the policy handles systemd's mounton so that it works > > similar to how we manage mountpoints for mount_t. Since systemd can be made > > to mount over just about anything, I'm looking at adding a new conditional > > that would allow init_t to mounton non_security_file_type, and then an > > interface like files_mountpoint(). > > > > The question is for the implementation of the interface; I see two options, > > either the interface allows mounton for all file-like classes, or the > > classes are specified as a parameter: > > > > -------- > > init.te: > > attribute init_mountpoint_type; > > allow init_t init_mountpoint_type:dir_file_class_set mounton; > > > > init.if: > > interface(`init_mountpoint',` > > typeattribute $1 init_mountpoint_type; > > ') > > -------- > > > > or > > > > -------- > > init.if: > > interface(`init_mountpoint',` > > allow init_t $1:$2 mounton; > > ') > > -------- > > > > I like the first option because it is clearer since you can see the mounton > > in init.te, but that is excessive access. The second option could be made > > to look like the first option, but it would need several attributes and > > interfaces, e.g. init_dir_mountpoint_type, init_file_mountpoint_type, etc. > > which isn't so desirable. > > > > Any thoughts on this? > > I implemented the former in my policy. ie the dir_file_class_set equiv.. > > 4163 (allow subj bind_path_obj_type_attribute (dirs (create))) > 4164 (allow subj bind_path_obj_type_attribute list_dir_perms) > 4165 (allow subj bind_path_obj_type_attribute (dir (mounton))) > 4166 (allow subj bind_path_obj_type_attribute create_file_perms) > 4167 (allow subj bind_path_obj_type_attribute (file (mounton))) > > As you can see i even allow systemd to create the mountpoint in case it does not exist. For example if /etc/machine-id does not exist and I have a BindReadOnlyPath=/etc/machine-id then systemd will touch /etc/machine-id and mount it ro > > It also generally buggy. Systemd does not (alway's) use setfscreatecon to create the mountpoints. And sometimes it does use setfscreatecon where it shouldnt. > > https://github.com/systemd/systemd/issues/13762 > Using dir_file_class_set in the first option seems excessive. For example systemd mounts /dev/kmsg as chr_file, as explained in https://github.com/SELinuxProject/refpolicy/pull/144, and allowing mounting on kmsg_device_t:dir would not make sense. Nevertheless, as systemd seems to be the only things I know that mounts over /dev/kmsg, it seems that dev_mounton_kmsg(init_t) could be replaced by init_mountpoint(kmsg_device_t, chr_file) or init_chr_mountpoint(kmsg_device_t). That being said, I personally prefer the first option (with an attribute) for types that are regular files and directories, as having files labeled like directories is quite common. In short, what about this? -------- init.te: attribute init_mountpoint_type; allow init_t init_mountpoint_type:{dir, file} mounton; init.if: interface(`init_mountpoint',` typeattribute $1 init_mountpoint_type; ') interface(`init_mounton_chr',` # Or "init_chr_mountpoint"? allow init_t $1:chr_file mounton; # An attribute could also be used here ') -------- Cheers, Nicolas
