Re: "Real programs dump core"

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Tue, Sep 06, 2011 at 04:37:08PM +0200, Hauke Fath wrote:
> At 9:20 Uhr -0400 06.09.2011, Thor Lancelot Simon wrote:
> >> The Amanda planner binary runs setuid root to open a privileged port, then
> >> reuurns to unprivileged mode. As such it apparently cannot write a core to
> >> the CWD. I guess I'd have to set proc.curproc.corename from the planner
> >> process, then.
> >
> >Why not fix the planner binary to not run setuid root?  It's not hard to
> >do.
> 
> I don't see how... Care to drop a hint?

Well, there are two basic ways:

1) Write a tiny setuid wrapper that opens the socket, leaves it open on a
   known file descriptor, drops privileges, then execs the planner.

2) Write a setuid port-opener that returns the file descriptor for the
   socket to its caller by file descriptor passing on a unix domain
   socket.

Thor