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To: ebuddington@wesleyan.edu
Cc: linux-kernel@vger.kernel.org
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Subject: Re: can chroot be made safe for non-root?
References: <20021016015106.E30836@ma-northadams1b-3.bur.adelphia.net>
From: Philippe Troin <phil@fifi.org>
Date: 15 Oct 2002 23:44:32 -0700
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Eric Buddington <eric@ma-northadams1b-3.bur.adelphia.net> writes:

> I am eager to be able to sandbox my processes on a system without the
> help of suid-root programs (as I prefer to have none of these on my
> system).

Probably an impossible task...

> Would it be reasonable to allow non-root processes to chroot(), if the
> chroot syscall also changed the cwd for non-root processes?

No.

  fd = open("/", O_RDONLY);
  chroot("/tmp");
  fchdir(fd);

and you're out of the chroot.

> Is there a reason besides standards compliance that chroot() does not
> already change directory to the chroot'd directory for root processes?
> Would it actually break existing apps if it did change the directory?

Probably not. Make that: change the directory to chroot'd directory if
the current working directory is outside the chroot. That is, leave
the cwd alone if it is already inside the chroot.

Phil.
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