On Tue, Oct 2, 2018 at 3:06 PM, James Morris [off-list ref] wrote:

On Tue, 2 Oct 2018, Kees Cook wrote:

quoted

On Tue, Oct 2, 2018 at 11:57 AM, John Johansen
[off-list ref] wrote:

quoted

Under the current scheme

lsm.enabled=selinux

could actually mean selinux,yama,loadpin,something_else are
enabled. If we extend this behavior to when full stacking lands

lsm.enabled=selinux,yama

might mean selinux,yama,apparmor,loadpin,something_else

and what that list is will vary from kernel to kernel, which I think
is harder for the user than the lsm.enabled list being what is
actually enabled at boot

Ah, I think I missed this in your earlier emails. What you don't like
here is that "lsm.enable=" is additive. You want it to be explicit.

This is a path to madness.

How about enable flags set ONLY per LSM:

lsm.selinux.enable=x
lsm.apparmor.enable=x

With no lsm.enable, and removing selinux=x and apparmor=x.

Yes this will break existing docs, but they can be updated for newer
kernel versions to say "replace selinux=0 with lsm.selinux.enable=0" from
kernel X onwards.

Surely distro packages and bootloaders are able to cope with changes to
kernel parameters?

We can either take a one-time hit now, or build new usability debt, which
will confuse people forever.

I'd like to avoid this for a few reasons:

- this requires per-LSM plumbing instead of centralized plumbing
  - each LSM needs to have its own CONFIG flag
  - each LSM needs to have its own bootparam flag
- SELinux has explicited stated they do not want to lose selinux=
- this doesn't meet John's goal of having a "single explicit enable list"

I think the current proposal (in the other thread) is likely the
sanest approach:

- Drop CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE
- Drop CONFIG_SECURITY_APPARMOR_BOOTPARAM_VALUE
- All enabled LSMs are listed at build-time in CONFIG_LSM_ENABLE
- Boot time enabling for selinux= and apparmor= remain
- lsm.enable= is explicit: overrides above and omissions are disabled
- maybe include lsm.disable= to disable anything

-Kees

-- 
Kees Cook
Pixel Security