[Dev] Cynara

Lukasz Wojciechowski l.wojciechow at partner.samsung.com
Mon Apr 14 14:07:20 GMT 2014


W dniu 2014-04-14 15:44, Patrick Ohly pisze:
> On Mon, 2014-04-14 at 15:09 +0200, Lukasz Wojciechowski wrote:
>> I have an impression that discussion went some wrong place. Is this
>> thread still about Cynara?
> The display server aspect is going a bit far, but I still think that it
> is relevant for assessing Cynara to understand how the rest of the
> problem is going to get addressed (or not addressed).
>
> It was not said clearly at the beginning which apps will be denied
> access via Cynara, and how said apps will be prevented from accessing
> data handled by the service.
>
> In my current understanding, Cynara is targeted at web apps which run
> inside a controlled environment already (the web runtime) and can only
> access the host through these services. That Cynara checks will also be
> applied for native system apps is a side effect that we won't take
> advantage of at the moment, because these apps can already do anything
> they want to the users data anyway. Note that I am thinking of the PIM
> data case here where service and app both run using the user's uid; it
> may be different for more privileged and/or special services.
>
> Is that correct?
>
I think apps cannot do anything they want with user data. Even native 
apps have access only to their private data.
Every application with its data folders should be Smack labeled. Smack 
labels are added in installation process for all applications: web, 
native, etc.
Different Smack labels for apps give us Smack level separation.

Consider what Rafał Krypa <r.krypa at samsung.com> wrote:

One assumption for Smack is needed for this model to work: to assign separate Smack labels for the applications. I believe that there is a consensus to go that way.
While different, the app labels would still logically belong to the User domain. This is probably very confusing, given the "3-domain policy" name, but a domain is defined as a set of labels.
Separate Smack labels offer two important benefits:
- separation: keeping private application files private, hidden from other apps. This also prevents stuff like ptrace() between applications with different privileges.
- identification: whether a service consults Cynara for policy or implements some policing on itself, it must be sure who is on the other side. Smack label is a perfect unforgeable identifier for user apps.


best regards
Lukasz



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