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Date:   Fri, 5 Oct 2018 14:58:13 +1000 (AEST)
From:   James Morris <jmorris@namei.org>
To:     Kees Cook <keescook@chromium.org>
cc:     John Johansen <john.johansen@canonical.com>,
        Jordan Glover <Golden_Miller83@protonmail.ch>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Paul Moore <paul@paul-moore.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        "Schaufler, Casey" <casey.schaufler@intel.com>,
        linux-security-module <linux-security-module@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH security-next v4 23/32] selinux: Remove boot parameter
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On Thu, 4 Oct 2018, Kees Cook wrote:

> On Thu, Oct 4, 2018 at 10:49 AM, James Morris <jmorris@namei.org> wrote:
> > On Wed, 3 Oct 2018, Kees Cook wrote:
> >> Then someone boots the system with:
> >>
> >> selinux=1 security=selinux
> >>
> >> In what order does selinux get initialized relative to yama?
> >> (apparmor, flagged as a "legacy major", would have been disabled by
> >> the "security=" not matching it.)
> >
> > It doesn't, it needs to be specified in one place.
> >
> > Distros will need to update boot parameter handling for this kernel
> > onwards.  Otherwise, we will need to carry this confusing mess forward
> > forever.
> 
> Are you saying that you want to overrule Paul and Stephen about
> keeping "selinux=1 secuiryt=selinux" working?

Not overrule, but convince.

At least, deprecate selinux=1 and security=X, but not extend it any 
further.

> > In my most recent suggestion, there is no '!' disablement, just
> > enablement.  If an LSM is not listed in CONFIG_LSM="", it's not enabled.
> 
> And a user would need to specify ALL lsms on the "lsm=" line?
> 

Yes, the ones they want enabled.

> What do you think of my latest proposal? It could happily work all
> three ways: old boot params and security= work ("selinux=1
> security=selinux" keeps working), individual LSM enable/disable works
> ("lsm=+loadpin"), and full LSM ordering works
> ("lsm=each,lsm,in,order,here"):
> 
> https://lore.kernel.org/lkml/CAGXu5jJJit8bDNvgXaFkuvFPy7NWtJW2oRWFbG-6iWk0+A1qng@mail.gmail.com/
> 

I think having something like +yama will still lead to confusion.
Explicitly stating each enabled LSM in order is totally unambiguous.

If people are moving away from the distro defaults, and there is no 
high-level interface to manage this, it seems to me there's a deeper 
issue with the distro.


-- 
James Morris
<jmorris@namei.org>