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From: Jim Dennis <jimd@mistery.mcafee.com>
Message-Id: <199604152130.OAA15411@mistery.mcafee.com>
Subject: Re: FreeBSD 2.1 SUID
To: andy.smith@reuters.com (Andy Smith)
Date: Mon, 15 Apr 1996 14:30:41 -0700 (PDT)
Cc: questions@freebsd.org
In-Reply-To: <1722091815041996/A16461/REOA2/11A47C891500*@MHS> from "Andy Smith" at Apr 15, 96 06:09:22 pm
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	I can't answer this definitively for FreeBSD but I can say that
	most modern implementations of Unix (including Linux) specifically
	ignore the SUID flag on shell scripts.

	You'll probably want to consider installing sudo or converting 
	the file to perl and running it with sperl (suidperl) or tperl
	(taintperl).

	suid shell scripts are considered to be inherently insecure
	due to numerous way in which they might be spoofed via
	aliases, environment variable, and custom-built chrooted 
	environments.

	writing a "wrapper" in c which uses a system() call to 
	run the script -- compiling that and setting the resulting
	binary SUID is the classic workaround to the problem.  However
	this is also considered to be of dubious value by most security
	analysts that I've talked to.  
	
	(Please note:  I don't consider myself an expert in security
	-- I'm simply echoing somethings that I've read.  I'd suggest
	the USAH -- _Unix_System_Administration_Handbook_ by 
	Nemeth, Synder and Seebass, and O'Reilly's _Practical_Unix_Security_
	by Garfinkel and Spafford (don't buy that one right now -- the 
	second edition is due out any day now and it should be under 
	the new title: _Practical_Unix_and_Internet_Security_).

Jim Dennis,
System Administrator,
McAfee Associates
 

> 
> I hope you can help with a small problem that I have using FreeBSD to
> implement a
> Firewall. 
> 
> First off let me just say that I am very impressed with FreeBSD and
> have used in to implement a number of large projects, including this
> one, in preference to Sun.
> 
> The system is a Pentium PC with IDE HD, IDE SyQuest, Mitsumi CD Rom,
> 32Mb RAM.
> 
> It is FreeBSD 2.1, with a recompiled kernel, removing NFS, SCSI etc.
> Most of the unused binaries have been removed from the system.
> 
> The problem is I have a C program, that runs as user operator, with
> UID 3. I need this user to be able to modify some files in /etc, so I
> have a sh script that should run suid root. This script is simply 
> 
> #! /bin/sh
> #
> cp /usr/local/proto/weekly /etc/weekly
> cp /usr/local/proto/daily /etc/daily
> cp /usr/local/proto/security /etc/security
> ...
> Plus more of the same
> 
> This script is called on exit from the C program. The sh script is
> owned by root.wheel and has permissions -rwsr-----. So that it
> 'should' suid to root as it runs, unfortunately this is not the case,
> and it runs with uid 3, the operator.
> 
> How can I get this (or any) shell script to run SUID root??
> 
> Thanks
> 
> Andy
> 
>