Re: Filesystem Capabilities in 2.6?

[Theodore Ts'o]

On Sun, Nov 03, 2002 at 01:37:19AM -0500, Alexander Viro wrote:
> > In other words, it would actually make perfect sense to have 
> > 
> >   -r-sr-sr-x    1 nobody  mail  451280 Apr  8  2002 /usr/bin/sendmail
> > 
> >   mount --bind --capability=chown,bindlow /usr/bin/sendmail /usr/bin/sendmail
> 
> *blam*
> 
> Congratulations with potential crapload of security holes - now anyone
> who'd compromised a process running as nobody can chmod the damn thing
> and modify it.
> 
> And that is the reason why suid-nonroot is bad.  It creates a class of
> binaries that can easily give you a root compromise if one of them has
> an exploit - even if that one is never run by root.

This is solved by some implementations of POSIX capabilities by
zapping any capabilities if the executible is modified --- just as
some Unix systems zap the setuid bit if the executable is modified.
It addresses specifically the problem that you've raised.

						- Ted