Be careful with rules

[Paul Moore]

On Tue, Jun 7, 2022 at 11:02 AM Steve Grubb <sgrubb at redhat.com> wrote:
> On Tuesday, June 7, 2022 9:42:06 AM EDT Paul Moore wrote:
> > On Mon, Jun 6, 2022 at 7:10 PM Lenny Bruzenak <lenny at magitekltd.com> wrote:
> > > I've been told that it is not a potential security problem, and not
> > > subject to change in the (current) kernel.
> >
> > I'm that little birdy that Lenny was talking to off-list so I figured
> > I would add a quick comment here :)
> >
> > As a reminder, elevated privilege is needed to both add/remove/modify
> > audit rules as well as the loaded SELinux policy (affecting the
> > validity of the relevant security labels).  Also, as Lenny already
> > mentioned, if an invalid security label is used, the kernel will
> > notify the admin via the kernel log.
>
> Wouldn't it be better if the kernel knew the rule was invalid to return
> EINVAL so that rule loading stops or becomes an error return from auditctl? A
> long time ago, there was no way from user space to check a type or a role or
> an selinux user for validity. Can that be done now? Is there an API for it?

We don't want to change how the kernel responds to userspace input
unless we have no (good) choice.  According to the git log, the kernel
has behaved like this for almost 20 years, this is not something we
want to change, especially given that we already need to trust the
administrator to configure the system correctly.

As I told Lenny earlier, I agree that the existing behavior is a bit
silly, but it's not something we can really change at this point with
the current API.  Future API changes will make things like this much
easier (hopefully I'll have more to share on this later this year).

-- 
paul-moore.com