Creating a capabilities-based restricted execution system

John Roth newsgroups at jhrothjr.com
Mon Jan 5 00:06:15 CET 2004


"Serge Orlov" <sombDELETE at pobox.ru> wrote in message
news:bta2ng$16v7$1 at nadya.doma...
>
> "John Roth" <newsgroups at jhrothjr.com> wrote in message
news:vvg0h93ue63c0b at news.supernews.com...
> >
> > What I *haven't* seen in this thread is very much consideration of
> > what people want from a security implementation.
>
> I think Sean is talking about his own implementation. I didn't
> see anywhere he said he's going to write general implementation
> for other people. He said what he wants from his implementation.

I see that point, and now that it's been made explicit (I missed
it the first time around, sorry,) I'm ok with it.

> > One problem I've been playing around with is: how would you
> > implement something functionally equivalent to the Unix/Linux
> > chroot() facility? The boundaries are that it should not require
> > coding changes to the application that is being restricted, and it
> > should allow any and all Python extension (not C language
> > extension) to operate as coded (at least as long as they don't
> > try to escape the jail!) Oh, yes. It has to work on Windows,
> > so it's not a legitimate response to say: "use chroot()."
>
> I don't see any unsolvable problems. Could you be more specific
> what is the problem? (besides time, money, need to support
> alternative python implementation, etc...)

Well, I don't see any unsolvable problems either. The biggest
sticking point is that the Unices use hard links to create
a directory tree that has the necessary programs availible.
Windows does not have this capability, so an implementation
would have to build a virtual directory structure, intercept all
paths and map them to the virtual structure backwards and
forwards.

The reason I find it an interesting problem is that I can't see
any way to do it with the kind of "generic" facility that was
in the Python Restricted execution facility,  at least without a
complete redesign of the file and directory functions and
classes in the os module. Without that, it would
require code in the C language implementation modules.
Right now the file and directory management modules are a
real mess.

John Roth
>
> -- Serge.
>
>





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