RE: preventing recursive loop in create dispatch hand------- ler

Hi Marc,

My answer was a bit vague, I agree… sorry.

Marc Sherman wrote:

Jerome,

How do you attach a “low” filter driver under the Fs? I’m guessing you
have to filter the disk driver to get this affect and then make sure
the requests to your disk driver filter are from the Fs you’re actully
interested in.

W2k allows you to have high and low filters, otherwise you are right for
NT4.0.

Also, what do you mean when you say to be careful in choosing your
target DO? Haven’t you already made that choice when you attached to
it earlier in order to filter it?

No, that was the point of the scheme, you choose (at any time) another
device object that the one you attached to at mount point. This device
object is created/known only by you and so is not filtered by other
devices on top of the stack, so you avoid the re-entrancy problem for
nested calls.

Finally, by patching the vpb, do you mean overwriting the DO
representing the mounted logical volume with a DO created by the
filter driver?

yes, this can be done by any driver and this driver can have a private
link to the fs.
(That’s my experience on NT 4.0)

Sorry for all the questions but a lot of this is still new to me.

thanks,
Marc

Jerome

> -----Original Message-----
> From: Jerome Christatos [mailto:xxxxx@vmware.com]
> Sent: Wednesday, July 12, 2000 4:27 PM
> To: File Systems Developers
> Subject: [ntfsd] RE: preventing recursive loop in create dispatch
hand
> ler
>
>
> Hi,
>
> I’ve been using this technique (“shadow device object” I call
> it :wink: for
> 2 years
> now with some success, but you must be careful in choosing your
target
> DO, some
> filters products use high and low filter drivers around the Fs at
the
> same time.
> (Getbasefilesystem() doesn’t always return the original Fs If I
recall
> correctly, if some filters patch the vpb).
>
> Jerome Christatos.
>
> —
> You are currently subscribed to ntfsd as: xxxxx@bionetrix.com
> To unsubscribe send a blank email to $subst(‘Email.Unsub’)

>

You can have a File system filter driver that layers itself below the FSD
and encrypts the file when it is to be written to the disk and decrypts it
when it is read from disk. This process takes place in the Kernel without
the knowledge of the user.
I beleive that Win2k has this feature that they call the EFS (Encrypting
file system)
and why is the autocad file to be destroyed if an unauthorized user can’t
read it ? this means having something into the Autocad application that will
destroy the file…i am not sure about how this can be acheived …

regds
amit
----- Original Message -----
From: Aaron Ballesteros
To: File Systems Developers
Sent: Thursday, July 13, 2000 10:45 PM
Subject: [ntfsd] [Fwd: Permanent Delivery Failure]

>
> I want a driver for NT server and Win95 to encode and decode autocad
>files
>without permission of the user. So when the user open or close an
>autocad file,
>doesn?t know about this internal process from Autocad application.
>If an unauthorized user send the file by mail, diskette, hard disk, CD,
>etc. this
>file travel encode and in the other side (destination), if the
>unauthorized user
>want to open but don?t have the decoder driver, the autocad file will
>be
>destroyed by any mechanism.
>If you are interested, please write me your proposal.

Aaron