SELinux Policy/Flask Classes from scratch

[Eric Paris]

On Fri, 2007-01-26 at 12:18 -0500, bx wrote:
>   I am working on creating a security policy from scratch and followed
> the tutorial the IBM published
> (http://www-128.ibm.com/developerworks/linux/library/l-selinux.html).
> After taking a look at the bare bones policy.conf file it generated,
> it got me thinking-  I don't need to have something as granular as
> SELinux allows me to be.  In fact it would simplify things if I could
> change the granularity.  How would SELinux be affected if I were to
> remove some of the class definitions and took anything that referred
> to those classes out of my policy?  Would SELinux just not enforce
> anything on those types of objects, would SELinux completely disallow
> all use of those objects or would it just break SELinux?  

Assuming you are talking about the definition of classes and permissions
in policy/flask/* pretty much it would just break.  The class and
permission definitions from policy and the kernel are supposed to match.
Recent kernel changes (2.6.18 and later I belive) have allowed policy to
load which does not define all of the classes and permissions defined in
the kernel, but it still enforces decisions over those classes and
permissions.  Since there cannot be any allow rules for those classes in
the policy everything gets denied.

I still have an old half baked patch which allows the policy to decide
if it wants to enforce decisions on undefined classes and permissions
but I haven't had time to make it work according to all the suggestions
I received when I submitted it.  So for now, you pretty much just have
to use them all.

-Eric