Re: dazukofs and /dev/dazukofs.ign

Frantisek Hrbata schrieb:
> On Fri, 20 Feb 2009 10:02:40 +0100
> John Ogness <[email protected]> wrote:
>
>   
>> On 2009-02-19, Frantisek Hrbata <[email protected]> wrote:
>>     
>>> it there any particular reason to store task_struct pointer for
>>> processes which should be ignored? This requires for multi-threaded
>>> application to register each thread to dazukofs.
>>>       
>> Correct.
>>
>>     
>>> I cannot figure out what is this good for. Isn't tgid enough?
>>>       
>> You have to define "enough". The ignore feature can be implemented
>> however we want. Like the old trusted feature, it is there for
>> applications to allow themselves to be ignored (as well as have some
>> control over _how_ they are ignored).
>>     
>
> I just don't thing it is necessary to make a difference between threads
> of one process. Basically because I think that trusted framework should
> be used just for one purpose(described later).
>
> Also I found following comment in the dazuko_linux26.c file.
>
>  <quote>
> /* Same thread id and same file descriptors,
>  * looks like they could be the same process...
>  * We will treat two threads of the same process
>  * as the same (for relation checks). This is
>  * useful for the Trusted Application Framework,
>  * if we trust one thread, we can trust them all.*/
> </quote>
>
> And I agree with this.
>
>   
>> It is possible that a multi-threaded application only wants one of its
>> threads to be ignored because the other threads are doing tasks (such
>> as downloading files) that should _not_ be ignored.
>>     
>
> I am not a big fan of this trusted thing, but it is needed. And from my
> point of view, it is needed just for an AV's which are doing scan in a
> different process then process which is accepting events(requests) from
> dazuko. This is the only situation I am considering adequate to use
> trusted framework.
>
>   
>>> AFAIK old dazuko supports whole process(including its threads) to be
>>> trusted and all you need to do is to call dazukoRegisterTrusted just
>>> once for each process.  Or am I missing something?
>>>       
>> Actually that is only partially correct. Dazuko 2.x also uses the task
>> struct (individual threads) to implement the trusted feature. However,
>> dazukoRegisterTrusted() also had a flag DAZUKO_TRUST_CHILDREN that
>> would allow all the threads of the process and all children-processes
>> to be trusted.
>>     
>
> I am aware of this. My option was that dazuko 2.x by default allows as
> trusted process and all its threads. As I can see in the source code the
> tgid is always checked.
>
> dazuko_is_our_daemon
>         |
>         v
> call_xp_id_compare(check_related is set)
>         |
>         v
> xp_id_compare(linux26)
>         |
>         v
> if (id1->tgid == id2->tgid && id1->files == id2->files)
>
> More over I cannot not see that those checks are anyhow conditioned by
> the DAZUKO_TRUST_CHILDREN. But maybe I am just missing something.
>
>   
>> The DazukoFS ignore feature does not have such an option because I
>> could not find a safe method for traversing process trees. But we
>> could expand the feature to allow configuring it to trust all threads
>> of a process. This is technically not necessary. It would only be
>> there as a convenience for developers.
>>
>> John Ogness
>>
>>     
>
> I agree. This is just a step forward to developers, but I would find it
> useful. 
>
> Now why I am interested in this. I would like to implement(just
> experimental) support for dauzkofs to our avg8 on-access scanner. The
> reason for this is that I would like to have some performance
> comparision dazukofs vs. avflt since there is none. 
>
> -FH
>
>
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> [email protected]
> http://lists.nongnu.org/mailman/listinfo/dazuko-devel
>
>   
To be honest, I dont see the reason to handle process ignoring within 
the kernel at all,
(as well as the group handling).
Those are things that should IMHO be done in userspace (maybe by
a daemon at which application can register for file accesses or trust. 
This daemon could
be the ONLY allowed application to communicate with dazuko).
There may be applications that would like to handle process trusting and 
group handling
in a totally different way (i.e by using config files that specify which 
applications to
consider as trusted, or using certificates or another authorization 
scheme to allow trusts).

It would also make the kernel code less complex without the 
group/ignoring implementation,
and thus a lot more stable.

Greetings,
Lino Sanfilippo









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