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Re: Hurdish applications for persistence


From: Bas Wijnen
Subject: Re: Hurdish applications for persistence
Date: Tue, 11 Oct 2005 15:00:22 +0200
User-agent: Mutt/1.5.11

On Tue, Oct 11, 2005 at 12:29:35PM +0200, Alfred M. Szmidt wrote:
> A obvious security exploit in the chroot() implementation (or really,
> file_reparent) and not in how passive translators work.  If you want a
> secure chroot enviroment (right now atleast) then you should run a
> sub-hurd.  Where this isn't possible (atleast, I have never been able
> to break out of a sub-hurd, and I have tried).  So instead of using
> broken UNIXoid ideas like chroot, it would make far more sense to
> implement a light-weight sub-hurd which can be used like chroot.

A problem here is that programs aren't and shouldn't be written solely for the
Hurd.  People should want to write portable programs, which means they don't
want to use platform-specific extentions.  This means a library is needed for
them.  But chroot exists, and if you replace it by a library call, nobody will
use it.

The obvious solution in this case would be to make chroot a libc call which
really just builds a sub-hurd.  However, I don't think that solves all the
problems.  Having the filesystem construct a "sane" environment is a very
fragile approach, and persistance sounds like a better solution to the
problem.  However, that has its costs as well, and I have no idea how big they
are.

Thanks,
Bas

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