linux-kernel - Re: [PATCH V40 04/29] lockdown: Enforce module signatures if the kernel is locked down

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Date:   Wed, 4 Sep 2019 09:57:52 -0700
From:   Matthew Garrett <mjg59@...gle.com>
To:     David Howells <dhowells@...hat.com>
Cc:     James Morris <jmorris@...ei.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>, Jessica Yu <jeyu@...nel.org>
Subject: Re: [PATCH V40 04/29] lockdown: Enforce module signatures if the
 kernel is locked down

On Fri, Aug 30, 2019 at 9:31 AM David Howells <dhowells@...hat.com> wrote:
>
> Matthew Garrett <matthewgarrett@...gle.com> wrote:
>
> >  enum lockdown_reason {
> >       LOCKDOWN_NONE,
> > +     LOCKDOWN_MODULE_SIGNATURE,
> >       LOCKDOWN_INTEGRITY_MAX,
> >       LOCKDOWN_CONFIDENTIALITY_MAX,
> >  };
>
> Aren't you mixing disjoint sets?

The goal is to be able to check whether any given lockdown reason is a
matter of integrity or confidentiality in a straightforward way.

> > +     [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
>
> Wouldn't it be better to pass this string as a parameter to
> security_locked_down()?

I thought about that, but it's not how any other LSM hooks behave. I
think it's probably easier to revisit that when we see how other LSMs
want to make use of the data.