Re: Just a few questions

[BVK Chaitanya]

Hi justin,

   Let me try to answer. Beware, i am a newbie. I am answering this 
sothat someone will point errors in *my* understanding.

> 1) How can the a process/kernel know that a capability really is who/what it 
> says it is?
>  
KERNEL: Kernel (should?) never know what really a capability can do. It 
only knows about (1) which process has access to this capability? (2) 
what kind of permissions a process has on this capability?

PROCESS: To know whether a capability is really what is says it is, a 
process should perform 'Capability Authentication'. A process must 
consult some *trusted* server processes to authenticate a capability.

> 2) How many capabilities can a capability have? 
??? Do you mean - how many capabilities can a *process* have? A process 
can have any number of capabilities it gets/creats, untill it runs out 
of its capability-space.

??? Do you mean - how many *methods* can a capability have? It depends 
on the interface that capability implements.

I dont understand your question properly.

> E.G. A mouse pointer capability loaded from a somewhere or other that also (malevolently) has the capability programed in to write to the hard drive?? Whats to stop that happening? 
If a process gets mouse pointer capability (say MPC), it shouldnt trust 
MPC unless it passes 'capability authentication' phase. Capability 
authentication guarantees that MPC you have is *really* *only* an MPC.

> Is the user requested to give permission every time a particular I/O operation 
> takes place? What if you have connected a
> file system ( maybe a floppy, CD ROM) and wish to copy some directories, will 
> it ask for permission on every object?
>  
I dont understand this :(

> 3) Will L4 on Hurd be using a constructor capability?
>  
It seems, this design/decision is not yet taken. I doubt, if Hurd goes 
for EROS like constructors, Hurd/Mach servers need considerable changes. 
Simply put - I dont know cleary.

> 4) Does L4 have the answers to some of the questions raised by a project like 
> Eros?
>  
L4.sec might have.


Correct me!
-BVK Chaitanya.