Re: Healing the bash fork

[Sebastian Krahmer <krahmer () suse de>]

Hi

On Tue, Sep 30, 2014 at 08:41:24AM -0500, Kobrin, Eric wrote:
> > "innocuous looking setuid program" made my day ;)
>
> > We should take care not to blame all and everything to bash.
>
> I don't find that blame is a useful tool for fixing security problems. What's more interesting to me is: what system 
> components are in a position to help. If a change in bash can make a bunch of "innocuous looking setuid programs" not 
> be  vectors for the import of malicious functions, let's do it.

In no shell-universe

setreuid(0, 0); system("date");

is an "innocuous looking setuid program". It fails in so many ways
that I cant enumerate it here, despite missing sanity checks for readability
and in that suids must not use system() or popen() in the first place.

If one finds a construct in code that looks similar to this, fix it. Really.
No bash update (and no other shell) will ever make this secure. If we start
fixing the underlying system so that above code is innocuous indeed, rather
than fixing the programmers producing such code, our road ends at php.

Sebastian

-- 

~ perl self.pl
~ $_='print"\$_=\47$_\47;eval"';eval
~ krahmer () suse de - SuSE Security Team