freebsd security - May 2004 - X & securelevel=3

running (4-Stable)

Hi,

short form question:
 how does one run XDM under securelevel>0 ?

long version:
i've searched for an answer on how to run Xfree/Xorg at a securelevel
the X server likes access to /dev/io and some other resources but is not
granted access after security is switched on.
one way of doing it seems to be to start it before setting the securelevel, but
then is doesnt allow a restart of X.
the other option seems to be the Aperture patch, ported in 2001 with no recent
updates and no longer usable against the current software.

2nd part of the question..
cd writing needs direct access to /dev/<acd0c> and that is also not
allowed in
secure more.
how can one give selective access to only allow (RW) access to one or two
devices ?

if there is no way of doing these things with configs and such, can anyone
point me at the relevant source code that controls these functions so i can add
this specific functionality. 


Cheers
* Anna

"bofn" <bofn@irq.org> writes:
> running (4-Stable)
> 
> Hi,
> 
> short form question:
>  how does one run XDM under securelevel>0 ?
> 
> long version:
> i've searched for an answer on how to run Xfree/Xorg at a securelevel
> the X server likes access to /dev/io and some other resources but is not
> granted access after security is switched on.
> one way of doing it seems to be to start it before setting the securelevel,
but
> then is doesnt allow a restart of X.
> the other option seems to be the Aperture patch, ported in 2001 with no
recent
> updates and no longer usable against the current software.
You understand the situation just fine.  The real question is what you
hope securelevels will do for you if you are allowing a userland
process to access arbitrary memory, as X does.  
> 2nd part of the question..
> cd writing needs direct access to /dev/<acd0c> and that is also not
allowed in
> secure more.
> how can one give selective access to only allow (RW) access to one or two
> devices ?
You can't.
> if there is no way of doing these things with configs and such, can anyone
> point me at the relevant source code that controls these functions so i can
add
> this specific functionality. 
That would probably be the platform-dependent mem.c and sys_machdep.c
files; I think you may need to worry about the spigot and vnops
opens as well (and probably ioctls).  I don't think it's worth
worrying about, though; it would be very hard to make it bulletproof,
and for fairly little gain.  

Securelevels are a very narrowly focused tool; they are not intended
to be a magic bullet for security.

> > running (4-Stable)
> >
> > Hi,
> >
> > short form question:
> >  how does one run XDM under securelevel>0 ?
I've revived the Apature kernel patch for the 4-Stable kernels
and put a flag in for mutex under 5-Stable, but have not and will not test that
part.
The Xorg package does support it with the right flag switched on.. 
So... the XDM under Seclevel is under control
i will publish the new version of the patch once i've tested it a bit more.

next one will be enabling access to /dev/<(a)cd0c> for CD writing.
unless someone has a clever idea on how to do it ?!
pointers and samples are welcome

Cheers
* Anna