Re: [9fans] sendfd() on native Plan 9?

[Nathaniel W Filardo <nwf@cs.jhu.edu>]

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On Sun, Jan 04, 2009 at 07:19:35AM +0200, lucio@proxima.alt.za wrote:
> > '#p'
> > allows any of my namespaces to debug processess in any other, '#s' is too
> > global, and /net seems to allow any of my processes to manipulate any of my
> > other processes' network connections (though I've not tested in detail to
> > see what's possible.)
> 
> So you're saying that (a) a jailed process should not have access to
> the #-devices at all and (b) their equivalent /proc, /srv and /net
> ought to be configured as part of the jail and should not be
> modifiable.

Sounds about right.  I'd say that they can be modifiable if new capabilities
are sendfd()'d into the namespace, but yes.
 
> Plan 9 source often short-circuits the possibility that #-something is
> not bound to the conventional place (#v comes to mind as a frequent
> culprit) but that is a form of laziness that could be corrected by a
> careful source audit.  In which case it would be possible to treat #X
> as another of those security issues that needed special treatment for
> Factotum and have a kernel request that puts the #-space out of
> bounds.

Elsewhere in a different thread, eric grepped for explicit uses of #X paths
and found very few.  See <3598a04c733942f7f010ad61d83a8bc2@quanstro.net>.
 
> Would that satisfy your requirements?  Oh, sure, I haven't ever used
> #| directly and I'm a bit ignorant of consequences, but the rest seems
> feasible.

I suspect #| being an exception wouldn't hurt, though it might be viewed as
a historical wart, being the only one... could #| be made to operate more
like devdup and given a canonical mountpoint?

> Another aspect I noticed is that what you seem to need is a
> finer-grained construction of #p and #s, but being able to construct
> them one layer further down the hierarchy might suffice.

"one layer further down the hierarchy" ?

> Just an uneducated opinion, I've had little occasion to study those
> specific devices or the others in any detail.  But I am curious of
> where this discussion could lead.

I too.

--nwf;

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