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Date:      Thu, 11 Jun 1998 13:23:06 -0700
From:      "Jordan K. Hubbard" <jkh@time.cdrom.com>
To:        jbryant@unix.tfs.net
Cc:        njs3@doc.ic.ac.uk (Niall Smart), freebsd-hackers@FreeBSD.ORG
Subject:   Re: [Fwd: Secure Ping 1.0] 
Message-ID:  <3902.897596586@time.cdrom.com>
In-Reply-To: Your message of "Thu, 11 Jun 1998 15:01:22 CDT." <199806112001.PAA22953@unix.tfs.net> 

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> the original "secure-ping" idea presented is useful for preventing
> abuse by the casual unix user.  anyhow, what kind of idiot keeps a
> compiler user-accessable in an untrusted environment?!

Perhaps the kind of idiot who also knows that it makes about as much
sense to "secure" a system that way as it does to install a locking
door on a cardboard shack. :-)

There are enough free shell accounts given out on the net that any
reasonably determined newbie cracker can compile something somewhere
else or just use the copy of PERL which is invariably found somewhere
to do socket manipulation.  You can't really control the creation or
importation of strange executables onto your system, but what you can
control is the execute bit itself.  My first intro to this was what
Paul Vixie first did on gatekeeper.dec.com - joblow could log in and
FTP over all the ICMP killers they wanted, but any attempts to chmod
them executable would just be silently ignored - it was blocked at the
syscall level.  I also believe there it was a kernel variable he could
just set and unset with the debugger to turn this off when he himself
needed to install something, but FreeBSD could probably more
effectively key off the secure level and have "no new execs" as a
kernel option to go along with a securelevel > 1, or something.

- Jordan

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