Re: [PATCH] libsepol/cil: Give an error when constraint expressions exceed max depth

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On Tue, Sep 8, 2020 at 9:46 AM Stephen Smalley
<stephen.smalley.work@xxxxxxxxx> wrote:
>
> On Fri, Sep 4, 2020 at 8:49 AM Stephen Smalley
> <stephen.smalley.work@xxxxxxxxx> wrote:
> >
> > On Thu, Sep 3, 2020 at 2:19 PM James Carter <jwcart2@xxxxxxxxx> wrote:
> > >
> > > CIL was not correctly determining the depth of constraint expressions
> > > which prevented it from giving an error when the max depth was exceeded.
> > > This allowed invalid policy binaries with constraint expressions exceeding
> > > the max depth to be created.
> > >
> > > Correctly calculate the depth of constraint expressions when building
> > > the AST and give an error when the max depth is exceeded.
> > >
> > > Reported-by: Jonathan Hettwer <j2468h@xxxxxxxxx>
> > > Signed-off-by: James Carter <jwcart2@xxxxxxxxx>
> >
> > The fix for conditional boolean expression depth checking can be a
> > separate patch.  For this one,
> >
> > Acked-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx>
>
> Actually, this breaks selinux-testsuite. Will have to look into why.
> /usr/sbin/semodule -i test_policy/test_policy.pp test_mlsconstrain.cil
> test_overlay_defaultrange.cil test_add_levels.cil test_glblub.cil
> Max depth of 4 exceeded for constraint expression
> Bad expression tree for constraint
> Bad constrain declaration at
> /var/lib/selinux/targeted/tmp/modules/100/base/cil:919

Here is the failing cil module:
$ cat policy/test_mlsconstrain.cil
(mlsconstrain (peer (recv)) (or (dom l1 l2) (and (neq t1
mcs_constrained_type) (neq t2 mcs_constrained_type))))
(mlsconstrain (packet (recv)) (or (dom l1 l2) (and (neq t1
mcs_constrained_type) (neq t2 mcs_constrained_type))))

Maybe an off-by-one in your depth checking?



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