[Dev] Cynara

Patrick Ohly patrick.ohly at intel.com
Wed Apr 9 14:38:56 GMT 2014


On Wed, 2014-04-09 at 15:13 +0200, José Bollo wrote:
> On mer, 2014-04-09 at 14:35 +0200, Patrick Ohly wrote:
> > On Wed, 2014-04-09 at 12:27 +0200, José Bollo wrote:
> > > On mer, 2014-04-09 at 09:30 +0200, Patrick Ohly wrote:
> > > > Access control: I understand that a service will have to implement this
> > > > access control mechanism and I see how Cynara will help with this. What
> > > > hasn't become clear to me is how a service running as a normal user
> > > > process (same PID as all other apps of the user) will be able to protect
> > > > its data files from those other processes when using the 3-domain Smack
> > > > model. Can someone point me towards documentation for that, ideally with
> > > > an example? Will it be possible to write services that grant direct
> > > > read-only access to files (for performance reasons) while handling
> > > > writes in the service?
> > > 
> > > I really agree with that remark. That is why I proposed a launcher that
> > > is aware of the problem of sharing/not sharing the filesystem.
> > > (see https://lists.tizen.org/pipermail/dev/2014-April/002292.html)
> > > I think that because smack rules modification will become lighter, the
> > > launch time will be less than 1 ms.
> > 
> > I've seen that. With that approach, apps can be restricted, but process
> > not getting that treatment would still have full access to everything. I
> > wonder whether we can do better than that.
> 
> You are right: apps not launched, not receiving the treatment have full
> accesses. But to my eyes it is not a problem because:
>  - Tizen enforces the use of launcher (for security) so what are the
> applications that aren't launched?

Which Tizen profile do you refer to here?

In Tizen IVI there are several user processes which do not get spawned
by the launcher and thus have access to more data than they really need.

>  - DAC and MAC are still here filtering real intrusions

But that doesn't help when the uid and smack label are the same.

> > Regarding "leaving details of multi-threading to the integrator": that
> > may simplify the work for the lib developer, but it complicates the
> > usage of the lib for service developers, in particular if those services
> > are not yet multithreaded. Just saying.
> 
> Agreed too. But remember only if it doesn't want to block.

My expectation is that services will not be allowed to block. So either
they are multithreaded, asynchronous or both. Cynara as currently
designed does not fit into services which are asynchronous, but not
multithreaded.

-- 
Best Regards, Patrick Ohly

The content of this message is my personal opinion only and although
I am an employee of Intel, the statements I make here in no way
represent Intel's position on the issue, nor am I authorized to speak
on behalf of Intel on this matter.





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