On Wed, 3 Oct 2018, Kees Cook wrote: > On Wed, Oct 3, 2018 at 11:28 AM, James Morris <jmorris@xxxxxxxxx> wrote: > > On Wed, 3 Oct 2018, Kees Cook wrote: > > > >> On Wed, Oct 3, 2018 at 11:17 AM, James Morris <jmorris@xxxxxxxxx> wrote: > >> > On Tue, 2 Oct 2018, John Johansen wrote: > >> >> To me a list like > >> >> lsm.enable=X,Y,Z > >> > > >> > What about even simpler: > >> > > >> > lsm=selinux,!apparmor,yama > >> > >> We're going to have lsm.order=, so I'd like to keep it with a dot > >> separator (this makes it more like module parameters, too). You want > >> to mix enable/disable in the same string? That implies you'd want > >> implicit enabling (i.e. it complements the builtin enabling), which is > >> opposite from what John wanted. > >> > > > > Why can't this be the order as well? > > That was covered extensively in the earlier threads. It boils down to > making sure we do not create a pattern of leaving LSMs disabled by > default when they are added to the kernel. The v1 series used > security= like this: > > + security= [SECURITY] An ordered comma-separated list of > + security modules to attempt to enable at boot. If > + this boot parameter is not specified, only the > + security modules asking for initialization will be > + enabled (see CONFIG_DEFAULT_SECURITY). Duplicate > + or invalid security modules will be ignored. The > + capability module is always loaded first, without > + regard to this parameter. > > This meant booting "security=apparmor" would disable all the other > LSMs, which wasn't friendly at all. So "security=" was left alone (to > leave it to only select the "major" LSM: all major LSMs not matching > "security=" would be disabled). So I proposed "lsm.order=" to specify > the order things were going to be initialized in, but to avoid kernels > booting with newly added LSMs forced-off due to not being listed in > "lsm.order=", it had to have implicit fall-back for unlisted LSMs. > (i.e. anything missing from lsm.order would then follow their order in > CONFIG_LSM_ORDER, and anything missing there would fall back to > link-time ordering.) However, then the objection was raised that this > didn't provide a way to explicitly disable an LSM. So I proposed > lsm.enable/disable, and John argued for CONFIG_LSM_ENABLE over > CONFIG_LSM_DISABLE. Ok, but it may end up being clearer, simpler, and thus more secure to just have a single way to configure LSM. For example: - All LSMs which are built are NOT enabled by default - You specify enablement and order via a Kconfig: CONFIG_LSM="selinux,yama" - This can be entirely overridden by a boot param: lsm="apparmor,landlock" And that's it. Of course, capabilities is always enabled and not be visible to kconfig or boot params. -- James Morris <jmorris@xxxxxxxxx>
