Re: 'native files', 'object fingerprints' [was: sendpath()]

[Andi Kleen]

On Tue, Jan 16, 2001 at 10:48:34AM +0100, Ingo Molnar wrote:
> this is a safe, very fast [ O(1) ] object-permission model. (it's a
> variation of a former idea of yours.) A process can pass object
> fingerprints and kernel pointers to other processes too - thus the other
> process can access the object too. Threads will 'naturally' share objects,
>...

Just setuid etc. doesn't work with that because access cannot be easily
revoked without disturbing other clients.

To handle that you would probably need a "relookup if needed" mechanism 
similar to what NFSv4 has, so that you can force other users to relookup
after you revoked a key. That complicates the use a lot though.

Also the model depends on good secure random numbers, which is questionable
in many environments (e.g. a diskless box where the random device effectively
gets no new input) 

-Andi