Date: Thu, 12 May 2011 08:26:49 -0700 From: Chris Telting <christopher-ml@telting.org> To: Jonathan McKeown <j.mckeown@ru.ac.za> Cc: freebsd-questions@freebsd.org Subject: Re: Established method to enable suid scripts? Message-ID: <4DCBFC39.8060900@telting.org> In-Reply-To: <201105121657.57647.j.mckeown@ru.ac.za> References: <4DC9DE2C.6070605@telting.org> <20110511141420.GD41080@gizmo.acns.msu.edu> <4DCBEB1E.6090209@telting.org> <201105121657.57647.j.mckeown@ru.ac.za>
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On 05/12/2011 07:57, Jonathan McKeown wrote: > On Thursday 12 May 2011 16:13:50 Chris Telting wrote: >> On 05/11/2011 07:14, Jerry McAllister wrote: >>> On Tue, May 10, 2011 at 05:54:04PM -0700, Chris Telting wrote: >>>> I've googled for over an hour. >>>> >>>> I'm not looking to get into a discussion on security or previous bugs >>>> that are currently fixed. Suid in and of itself is a security issue. >>>> But if you are using suid it it should work; I don't want to use a >>>> kludge and I don't want to use sudo. I'm hoping it's a setting that is >>>> just disabled by default. >>> My understanding is that in general the system does not allow SUID >>> on scripts. The way I have gotten around that (a long time ago) >>> was to create a small binary that exec's the script and making >>> the binary SUID. >> Well it's all hacks and in my not so humble option like chasing your >> tail. The assumption is that if someone creates an executable >> (assumption is programming is C) they are more credible not to make >> mistakes. That's a fallacy and just plain nuts. And I'm an interpreted >> language snob saying that. Suid is either allowable or not and should >> be a sysctl and apply equally to binaries and scripts. Yet another >> thing to add to my project list. Anyone know of an established patch >> for fix this freebsd issue or am I yet again going to have to create my >> own? > Have you appreciated the issue with suid on scripts? It's nothing at all to do > with whether someone writing a compiled language is a better programmer than > someone writing an interpreted language. > > When the OS launches a binary, the file containing the program is opened once. > > When the OS launches an interpreted program, the file is opened once to find > out which interpreter to run, and then the interpreter is told to re-open the > same filename - whose contents might meanwhile have changed. > > I'll say that again. It is inherently insecure to run an interpreted program > set-uid, because the filename is opened twice and there's no guarantee that > someone hasn't changed the contents of the file addressed by that name > between the first and second open. > > It's one thing to tell people they need to be careful with suid because it has > security implications. Deliberately introducing a well-known security hole > into the system would in my view be dangerous and wrong. That race condition bug was fixed in ancient times. Before Freebsd or Linux ever existed I believe. It's a meme that just won't die. People accepted mediocrity in old commercial versions of Unix. I personally am unsatisfied by kludges.
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