Re: [Xen-devel] [PATCH] xsm/flask: Handle policy load failures properly

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-02-24 at 09:51 +0000, Julien Grall wrote:
> 
> On 24/02/2015 09:39, Ian Campbell wrote:
> > On Tue, 2015-02-24 at 09:31 +0000, Julien Grall wrote:
> >>
> >> On 24/02/2015 08:47, Ian Campbell wrote:
> >>> On Mon, 2015-02-23 at 12:53 -0500, Daniel De Graaf wrote:
> >>>> When no policy is loaded, the FLASK policy is equivalent to an allow-all
> >>>> policy; see xen/xsm/flask/ss/services.c:security_compute_av where it
> >>>> bails out if !ss_initialized.  It could be considered as either enforcing
> >>>> or being permissive with an allow-all policy, but the actual access is
> >>>> the same.
> >>>
> >>> Do you think anyone would want an option to be provided which causes Xen
> >>> to fail to boot if a proper policy isn't provided (and loaded)? Similar
> >>> to how iommu=force works.
> >>>
> >>> I can see how osstest testcases for xsm might want this to avoid
> >>> accidentally testing with no policy, but not sure if it would be
> >>> considered generally useful enough to be added.
> >>
> >> I think it would make sense to panic when flask_enforcing is enabled and
> >> the policy is not loaded or valid.
> >
> > That would stop you running in enforcing mode with a late loaded policy.
> > A separate flag to enforce boot time loading was what I was thinking of.
> 
> You can enforce the policy later via xl setenforce.

Ah, good.

> So if someone wants to load a policy later and enforced it, he would 
> have to call :
>       - xl loadpolicy
>       - xl setenforce
> 
> IHMO, when you set flask_enforcing on the command line, you expect to 
> pass a policy via the bootloader.

That doesn't seem unreasonable -- Daniel what do you think?


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