[HACKERS] semaphore usage "port based"?

[Kris Kennaway]

On Mon, Apr 03, 2006 at 06:51:45PM -0400, Stephen Frost wrote:
> * Robert Watson (rwatson at FreeBSD.org) wrote:
> > On Mon, 3 Apr 2006, Stephen Frost wrote:
> > >This is certainly a problem with FBSD jails...  Not only the 
> > >inconsistancy, but what happens if someone manages to get access to the 
> > >appropriate uid under one jail and starts sniffing or messing with the 
> > >semaphores or shared memory segments from other jails?  If that's possible 
> > >then that's a rather glaring security problem...
> > 
> > This is why it's disabled by default, and the jail documentation 
> > specifically advises of this possibility.  Excerpt below.
> 
> Ah, I see, glad to see it's accurately documented.  Given the rather
> significant use of shared memory by Postgres it seems to me that
> jail'ing it under FBSD is unlikely to get you the kind of isolation
> between instances that you want (the assumption being that you want to
> avoid the possibility of a user under one jail impacting a user in
> another jail).  As such, I'd suggest finding something else if you
> truely need that isolation for Postgres or dropping the jails entirely.
> 
> Running the Postgres instances under different uids (as you'd probably
> expect to do anyway if not using the jails) is probably the right
> approach.  Doing that and using jails would probably work, just don't
> delude yourself into thinking that you're safe from a malicious user in
> one jail.

Yes; however jails are still useful for administrative
compartmentalization even when you have to weaken their security
properties, such as here.

Kris
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