Re: Updates of SE-PostgreSQL 8.4devel patches (r1197)

On Fri, 2008-11-07 at 16:52 -0500, Bruce Momjian wrote:
> Simon Riggs wrote:
> > > > So if somebody with context x tries to delete value1 from TableB, they
> > > > will be refused because of a row they cannot see. In this case the
> > > > correct action is to update the tuple in TableB so it now has a
> > > > security_context = y. The user with x cannot see it and can be persuaded
> > > > he deleted it, while the user with y can still see it.
> > >
> > > It seems odd for a low-privilege user to be able to elevate the
> > > privilege of a tuple above their own privilege level. I also don't
> > > believe that the privilege level is a total order, which might make
> > > this something of a sticky wicket. But those are just my thoughts as
> > > a non-guru.
> >
> > The low-privilege user isn't elevating the label. If the tuple was
> > visible by multiple labels it was already elevated. All I am suggesting
> > is the system remove the one it can see, leaving the other ones intact.
> > This makes the row appear to be deleted by the lower privileged user,
> > whereas in fact it was merely updated. There need not be any ordering to
> > the labels for this scheme to work.
>
> Simon, would you read the chapter on "covert channels"? You might
> understand it better than I do and it might give you some ideas:
>
> http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.33.5950

It's probably easier just to say "here is the specification we;re
working to implement".

--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support