On Fri, Sep 12, 2014 at 6:37 AM, Stephen Smalley <[email protected]> wrote:

> Ideally it shouldn't need to scale because there should be very few if
> any exceptions added to the set of neverallow rules in
> external/sepolicy.  When you encounter a neverallow failure, the first
> step should be to see if you can avoid the need for the offending allow
> rule altogether.  This has happened for other cases in AOSP for the
> device-specific daemons on the Nexus devices, for example.
>

+1


>
> If we have a neverallow rule in external/sepolicy that we know will
> require device-specific overrides, we can define and use an attribute in
> writing the rule so that the device-specific policy can exempt its own
> domains by adding the attribute to those domains, e.g. rewrite:
>

We've tried this in the past with the relabelto domain, and in retrospect,
it just ended up causing more complexity than it solved. We ended up
deleting it in https://android-review.googlesource.com/#/c/94000/ . While
this approach is possible, I'd agree with you that we shouldn't follow this
approach.

I don't believe however that we should do this a priori for all of the
> neverallow rules, as it makes it all too easy to subvert any/all of the
> neverallow rules.  Rather if/when OEMs find the need for an exception,
> they can upload a change to external/sepolicy to rewrite the neverallow
> rule along with the justification as to why it is necessary for
> device-specific daemons, and the Android developers can assess the
> change on its merits, possibly suggesting alternative means of solving
> it without requiring such a change.
>


Agreed.

-- 
Nick Kralevich | Android Security | [email protected] | 650.214.4037
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