Messages in this thread | | | From | Kees Cook <> | Date | Mon, 17 Sep 2018 11:14:26 -0700 | Subject | Re: [PATCH 16/18] LSM: Allow arbitrary LSM ordering |
| |
On Mon, Sep 17, 2018 at 10:13 AM, Casey Schaufler <casey@schaufler-ca.com> wrote: > TOMOYO uses the cred blob pointer. When the blob is shared TOMOYO > has to be allocated a pointer size chunk to store the pointer in. > Smack has the same behavior on file blobs.
Oh dang, yes, I got confused over secid and other "extreme" shared things.
So one change of my series would be to declare tomoyo as "exclusive" too.
> Today the distinction is based on how the module registers hooks. > Modules that use blobs (including TOMOYO) use security_module_enable() > and those that don't just use security_add_hooks(). The "pick one" > policy is enforced in security_module_enable(), which is why you can > have as many non-blob users as you like. You could easily have a > non-blob using module that was exclusive simply by using > security_module_enable().
True. With my removal of security_module_enable(), yes, it makes sense to mark all LSMs that were calling it before as exclusive, rather than focusing on whether they would be exclusive under the blob-sharing situation.
> Keep security=$lsm with the existing exclusive behavior. > Add lsm=$lsm1,...,$lsmN which requires a full list of modules > > If you want to be fancy (I don't!) you could add > > lsm.add=$lsm1,...,$lsmN which adds the modules to the stack > lsm.delete=$lsm1,...,$lsmN which deletes modules from the stack
We've got two issues: ordering and enablement. It's been strongly suggested that we should move away from per-LSM enable/disable flags (to which I agree). If ordering should be separate from enablement (to avoid the "booted kernel with new LSM built in, but my lsm="..." line didn't include it so it's disabled case), then I think we need to split the logic (otherwise we just reinvented "security=" with similar problems).
Should "lsm=" allow arbitrary ordering? (I think yes.)
Should "lsm=" imply implicit enable/disable? (I think no: unlisted LSMs are implicitly auto-appended to the explicit list)
So then we could have "lsm.enable=..." and "lsm.disable=...".
If builtin list was: capability,yama,loadpin,integrity,{selinux,smack,tomoyo,apparmor} then:
lsm.disable=loadpin lsm=smack
becomes
capability,smack,yama,integrity
and
CONFIG_SECURITY_LOADPIN_DEFAULT_ENABLED=n selinux.enable=0 lsm.add=loadpin lsm.disable=smack,tomoyo lsm=integrity
becomes
capability,integrity,yama,loadpin,apparmor
If "lsm=" _does_ imply enablement, then how does it interact with per-LSM disabling? i.e. what does "apparmor.enabled=0 lsm=yama,apparmor" mean? If it means "turn on apparmor" how do I turn on a CONFIG-default-off LSM without specifying all the other LSMs too?
-Kees
-- Kees Cook Pixel Security
| |