Re: establishing the callers PID

[Marcus Brinkmann]

On Sat, May 11, 2002 at 06:02:18PM -0700, Thomas Bushnell, BSG wrote:
> Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> writes:
> 
> > I think it is absolutely mandatory that we establish the PID in a
> > trustworthy way rather than let the user provide some unique ID on its own.
> > I think there is already a place in the Hurd where we should do that but
> > don't (wasn't that term's term_open_ctty?), and there are all sort of simple
> > attacks possible if we can't trust the PID (eg a monitor server might check
> > for stale advisory locks and kill processes that don't release them timely. 
> > In the untrusted model, a user could make this monitor process kill
> > arbitrary processes on the system).
> 
> Nope; a malicious filesystem could just return bogus PID values too.

Mmh, we could restrict the monitor to trusted filesystems (eg /).
 
> I don't think this is a serious security issue, actually.  Such a
> monitor depends on an awful lot--it's not a strict Posix program
> already.

I am not really particularly attached to my example, it was just one of the
first that came to my mind.  Are you suggesting with "I don't think that
this is a serious security issue" that relying on a PID provided by the user
is good enough in the general case?  Or were you only relating this to my
example?

Thanks,
Marcus 

-- 
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
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