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Re: restricted bash (rbash)


On 15 Nov 2000, Peter Cordes <peter@llama.nslug.ns.ca> wrote:
> > Jochen,
> > 
> > mkdir /usr/local/bin/restricted;ln -s <command>
> > /usr/local/bin/restricted/<command>;...
> > 
> > export PATH=/usr/local/bin/restricted;exec rbash
> > 
> > ...boom. Now only the commands you want the user to be able to run will be
> > available. 

OK. So far it's clear I think.

> > Shell scripts, however, continue to work fine, since their
> > `hash bang' doesn't pay attention to the PATH anyway (which I think is
> > more than slightly objectionable, but that's beyond the scope of this
> > email).

Umm... OK, so you have a restricted shell where /bin/bash is not executed
any more. But if your script begins


(or e.g. #!/usr/bin/perl) does rbash really still execute it?? Would be an
easy way to work around all those restrictions, right? Or did I just get
you wrong? Otherwise many users' scripts would simply be dead suddenly...

>   As long as they can't write to a directory that they can execute files
> from (i.e. in PATH, with rbash), they can't take advantage of it.
> (Probably...)

> I think rsh (restricted, not remote) was designed a long time ago, back when
> casual security was all that was needed.  If you trust your users not to
> be malicious, and just want to protect them from themselves, more or less,
> restricted shell is the way to go.

OK, I think I can live with that :-). Restricted != secure ...



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