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SubjectRe: access to proc filesystem from chrooted process
   Date: 	Fri, 28 May 1999 10:13:59 -0700 (PDT)
From: Tim Smith <tzs@tzs.net>

Check the archives of this list. A while back there was a discussion of
chroot, and many ways to get out of a chroot'ed environment were listed.
I seem to recall that the conclusion was that chroot is not meant to be,
and cannot be made into, a secure environment. It is really just a safety
net that will catch accidental goofs, but won't stop anyone trying to get
around it.

I wouldn't go that far. It's possible to use chroot as part of secure,
restricted environment. However, there are other restrictions that a
process which is setting up such a restricted environment really does
have to check for in order to assure that the environment really is
secure. For example, the parent process which is doing the chroot needs
to make sure that there aren't any excess open file descriptors; it
needs to make sure there aren't any stray extra devices present in the
enviroment. There had better not be any setuid root programs in the
chroot'ed part of the filesystem, and the chrooted process should not
have root privileges when the environment is setup, and so on.

It's true that chroot is a general purpose solution where you don't have
to pay attention to other issues. But there are very few such examples
in the security world. The devil is always in the details, no matter
which tools you are using --- and chroot is simply one such tool, with
strengths and limitations.

- Ted



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