From owner-freebsd-questions@FreeBSD.ORG  Fri Oct 27 15:51:11 2006
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id DD6A416A492
	for <freebsd-questions@freebsd.org>;
	Fri, 27 Oct 2006 15:51:11 +0000 (UTC)
	(envelope-from malcolm.kay@internode.on.net)
Received: from ash25e.internode.on.net (ash25e.internode.on.net
	[203.16.214.182])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 2946343D46
	for <freebsd-questions@freebsd.org>;
	Fri, 27 Oct 2006 15:51:10 +0000 (GMT)
	(envelope-from malcolm.kay@internode.on.net)
Received: from alpha.home (ppp66-14.lns3.adl2.internode.on.net [121.44.66.14])
	by ash25e.internode.on.net (8.13.6/8.13.5) with ESMTP id
	k9RFp8pW069006 for <freebsd-questions@freebsd.org>;
	Sat, 28 Oct 2006 01:21:09 +0930 (CST)
	(envelope-from malcolm.kay@internode.on.net)
From: Malcolm Kay <malcolm.kay@internode.on.net>
Organization: at home
To: freebsd-questions@freebsd.org
Date: Sat, 28 Oct 2006 01:21:07 +0930
User-Agent: KMail/1.8
MIME-Version: 1.0
Content-Type: text/plain;
  charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200610280121.07939.malcolm.kay@internode.on.net>
Subject: mount_smbfs/umount for non root user.
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 27 Oct 2006 15:51:11 -0000

Running mount_smbfs as a regular user generates a permission
denial in relation to iconv in the kernel.
This is apparently a well known problem which can be circumvented 
by setting the set-user-id-on-execution bit for mount_smbfs. 
This works for me but leads to the problem that the mount is now 
seen as belonging to root and the regular user gets a denial on 
umount.

Allowing regular users to mount smb shares with mount_smbfs seems
to me fairly benign but to set the  set-user-id-on-execution bit
for umount would be extremely dangerous.

Is there a way around this problem -- this is under FreeBSD 5.4.

Taking a look at the sources for mount_smbfs and the associated 
library, libsmb, I see that conditional compilation for APPLE 
(Darwin?) switches the effective user id when the 
set-user-id-on-execution bit is set with the code executed 
mostly under the identity of the real user and switching to 
privileged mode only for a few brief activities - notably for
installing the iconv table and a few error conditions. Apart from 
this the code looks very similar to (but not quite identical 
with) the FreeBSD code.

I presume (without any real justification) that these differences 
in the APPLE version are intended to circumvent the difficulty I 
am having when running under Darwin.

The question is if I modify the FreeBSD code to perform similar 
switchings of effective user id and recompile am I likely to 
achieve my desired goal? Has anyone else tried this?

Any comments would be welcome.

Malcolm