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SubjectRe: NFS question
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Peter wrote:

> I disagree. Consider the case where you are exporting files to a
> trusted machine - unprivileged users can execute but not read the file,
> which is what you wanted.
>
> It is only a security risk if you are exporting files to machines that
> are not under your control.

I believe that the behaviour should be:
if flags do not include "no_root_squash" -> deny access to mode 711
else if flags include "insecure" (non-root clients) -> deny access to mode 711
else if client is permitted by anonymous rule -> deny access to mode 711
else -> permit access to mode 711
Alternatively, the world could always use another export flag.
"permit_read_executable"?

Note that at present using the Linux loader for dynamically linked files,
the comment "unprivileged users can execute but not read the file" is
fairly inaccurate anyway - as per my post to linux-kernel & bugtraq with
a little LD_PRELOAD to dump a copy of the file. I think this is a loader
bug, and mode 711 executables should be treated as SUID executables are,
but opinions vary wildly.

(my view is that if someone sets a binary mode 711 it's a conscious decision
that they don't want anyone else reading the file or being able to reconstruct
the file and hence the loader and kernel should respect that, rather than
just denying read() to give a false sense of security)

David.

PS: This reply-to thing is annoying. It means that I get "To" set to the
list, "Cc" set to the people who were previously Cc'd (in this case Alan)
and have to add the person who I am responding to if I want to be sure they
get my response. If you are going to use "Reply-To", also move "Cc" to
"X-Cc". A little consistency, please.


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