Re: X avcs

[Eamon Walsh <ewalsh@tycho.nsa.gov>]

Glenn Faden wrote:
> Eamon Walsh wrote:
>   
>>  
>> OK, I worked on this today.  The property polyinstantiation itself is 
>> easy enough, but I've run into a problem with the PropertyNotify 
>> events that occur when a polyinstantiated property is changed or 
>> deleted - everyone can see them!  Some major changes to the event 
>> delivery model are probably going to be necessary to make this work.
>>
>> I can't immediately see how it's done in Trusted Extensions.  In 
>> TsolDeleteProperty there is just a regular DeliverEvents call to send 
>> the event.
>>
>> I think there will have to be a way to pass some private data down 
>> with all events, and then have another hook call further down that 
>> gives a yes/no answer for each client.
>>     
> You're probably right that unnecessary PropertyNotify events may be 
> distributed to any client who has expressed interest in this event on 
> the root window. I don't think this is a big problem, however. If the 
> client cares to read the property whose atom is associated with the 
> event it will get the value which matches its security context.
>
> If your concern is that this presents a covert channel, that is an issue 
> that we generally ignore. For example we don't prevent higher-level 
> windows from generating exposure events which may be delivered to lower 
> level windows. We only prevent normal clients from mapping windows into 
> a Trusted Path workspace.
>
> --Glenn
>   

I'll press forward with this then, putting the event delivery on the 
to-do list.


-- 
Eamon Walsh <ewalsh@tycho.nsa.gov>
National Security Agency


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