Re: [PATCH 10/10] LSM: Blob sharing support for S.A.R.A and LandLock

[Jordan Glover]

On Thursday, September 13, 2018 11:50 PM, Paul Moore <paul@xxxxxxxxxxxxxx> wrote:

> On Thu, Sep 13, 2018 at 4:58 PM Jordan Glover
> Golden_Miller83@xxxxxxxxxxxxx wrote:
>
> > On Thursday, September 13, 2018 9:12 PM, Paul Moore paul@xxxxxxxxxxxxxx wrote:
> >
> > > On Thu, Sep 13, 2018 at 11:19 AM Kees Cook keescook@xxxxxxxxxxxx wrote:
> > >
> > > > On Thu, Sep 13, 2018 at 6:16 AM, Paul Moore paul@xxxxxxxxxxxxxx wrote:
> > > >
> > > > > On Thu, Sep 13, 2018 at 12:19 AM Kees Cook keescook@xxxxxxxxxxxx wrote:
>
> ...
>
> > > > > > I don't see a good reason to make this a config. Why shouldn't this
> > > > > > always be enabled?
> > > > >
> > > > > I do. From a user perspective it is sometimes difficult to determine
> > > > > the reason behind a failed operation; its is a DAC based denial, the
> > > > > LSM, or some other failure? Stacking additional LSMs has the
> > > > > potential to make this worse. The boot time configuration adds to the
> > > > > complexity.
> > > >
> > > > Let me try to convince you otherwise. :) The reason I think there's no
> > > > need for this is because the only functional change here is how
> > > > TOMOYO gets stacked. And in my proposal, we can convert TOMOYO to be
> > > > enabled/disabled like LoadPin. Given the configs I showed, stacking
> > > > TOMOYO with the other major LSMs becomes a config (and/or boottime)
> > > > option.
> > > > The changes for TOMOYO are still needed even with SECURITY_STACKING,
> > > > and I argue that the other major LSMs remain the same. It's only
> > > > infrastructure that has changed. So, I think having SECURITY_STACKING
> > > > actually makes things more complex internally (all the ifdefs, weird
> > > > enable logic) and for distros ("what's this stacking option", etc?)
> > >
> > > None of the above deals with the user experience or support burden a
> > > distro would have by forcing stacking on. If we make it an option the
> > > distros can choose for themselves; picking a kernel build config is
> > > not something new to distros, and I think Casey's text adequately
> > > explains CONFIG_SECURITY_STACKING in terms that would be sufficient.
> >
> > CONFIG_SECURITY_STACKING doesn't make any user visible changes on
> > itself as it doesn't automatically enable any new LSM. The LSM
> > specific configs are place where users/distros make decisions. If
> > there is only one LSM enabled to run then there's nothing to stack.
> > If someone choose to run two or more LSM in config/boot cmdline
> > then we can assume having it stacked is what they wanted. As Kees
> > pointed there is already CONFIG_SECURITY_DEFAULT_XXX. In both cases
> > CONFIG_SECURITY_STACKING is redundant and only adds burden instead
> > of removing it.
>
> See my last response to Kees.
>
> > > I currently have a neutral stance on stacking, making it mandatory
> > > pushes me more towards a "no".
> >
> > This implies that your real concern is something else than
> > CONFIG_SECURITY_STACKING which only allows you to ignore the whole
> > thing. Please reveal it. There are a lot of people waiting for LSM
> > stacking which is several years late and it would be great to
> > resolve potential issues earlier rather later.
>
> What? I resent the implication that I'm hiding anything; there are a
> lot of fair criticisms you could level at me, but I take offense at
> the idea that I'm not being honest here. I've been speaking with
> Casey, John, and others about stacking for years, both on-list and
> in-person at conferences, and my
> neutral-opinion-just-make-it-work-for-everything-and-make-it-optional
> stance has been pretty consistent and isn't new.
>
> Also, let's be really clear here: I'm only asking that stacking be
> made a build time option (as it is in Casey's patchset). That seems
> like a pretty modest ask for something so significant and "several
> years late" as you put it.
>
> paul moore

Fair enough. I apologize then.

Jordan