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Category:   OS (UNIX)  >   Dump Vendors:   NetBSD
NetBSD dump Utility Lets Local Users Obtain 'tty' Group Privileges
SecurityTracker Alert ID:  1002253
SecurityTracker URL:  http://securitytracker.com/id/1002253
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Aug 25 2001
Impact:   Execution of arbitrary code via local system, User access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): NetBSD-current: source prior to August 8, 2001, NetBSD 1.5.1, NetBSD 1.5, NetBSD 1.4.x
Description:   NetBSD reports that the dump utility for NetBSD contains a vulnerability that allows a local user to obtain tty group privileges.

It is reported that the dump(8) command (installed as /sbin/dump) and the dump_lfs(8) command (installed as /sbin/dump_lfs) are configured with set group id (setgid) tty group privileges. The programs apparently do not drop those setgid tty rights when not needed, including when a user supplied RCMD_CMD environment variable is executed.

These programs reportedly require tty group rights in order to notify members of the operator group to change backup media.

A similar vulnerability was reported with the dump utility on other operating systems last year, but that prior vulnerability resulted in local users gaining root privileges.

Impact:   A local user can gain tty group privileges on the host.
Solution:   The vendor has released fixes for this vulnerability. See the patch instructions in the Source Message.

Fixed versions include:
NetBSD-current: August 8, 2001;
NetBSD-1.5 branch: August 8, 2001 (1.5.2 includes the fix);
NetBSD-1.4 branch: Pullups are pending - see the Source Message.

Vendor URL:  www.netbsd.org/security (Links to External Site)
Cause:   Access control error
Underlying OS:  UNIX (NetBSD)

Message History:   None.


 Source Message Contents

Subject:  NetBSD Security Advisory 2001-014: dump(8) exposes 'tty' group


-----BEGIN PGP SIGNED MESSAGE-----


                 NetBSD Security Advisory 2001-014
                 =================================

Topic:		dump(8) exposes 'tty' group 

Version:	NetBSD-current: source prior to August 8, 2001
		NetBSD 1.5.1:	affected
		NetBSD 1.5:	affected
		NetBSD 1.4.x:	all affected
		
Severity:	local users can gain tty group

Fixed:		NetBSD-current:		August 8, 2001
		NetBSD-1.5 branch:	August 8, 2001 (1.5.2 includes the fix)
		NetBSD-1.4 branch:	Pullups pending - apply the patch as
					explained below.


Abstract
========

The dump(8) command (installed as /sbin/dump) and the dump_lfs(8)
command (installed as /sbin/dump_lfs) are setgid tty.  dump(8) and
dump_lfs(8) did not drop those setgid tty rights while performing
functions other than those the rights were provided for, including
execution of a user supplied RCMD_CMD environment variable.


Technical Details
=================

dump(8) and dump_lfs(8) require tty rights in order to notify
members of the operator group to change backup media.  Since a user
can supply an executable as a method to access a remote dump device
by setting the RCMD_CMD environment variable, a local user can gain
tty privilieges for themselves.

With the supplied patch, dump(8) and dump_lfs(8) properly reserve
tty rights and activate them only for the intended use.


Solutions and Workarounds
=========================

The following instructions describe how to upgrade your dump(8)
and dump_lfs(8) binaries by updating your source tree and rebuilding
and installing a new version of dump(8) and dump_lfs(8).

* NetBSD-current:

	Systems running NetBSD-current dated from before 2001-08-08
	should be upgraded to NetBSD-current dated 2001-08-09 or later.

	The following directories need to be updated from the
	netbsd-current CVS branch (aka HEAD):
		basesrc/sbin/dump

	To update from CVS, re-build, and re-install dump and dump_lfs:
		# cd src
		# cvs update -d -P sbin/dump
		# cd sbin/dump

		# make cleandir dependall
		# make install
		# cd ../dump_lfs
		# make cleandir dependall
		# make install


* NetBSD 1.5, 1.5.1:

	Systems running NetBSD 1.5 or 1.5.1 sources dated from
	before 2001-08-08 should be upgraded from NetBSD 1.5.x
	sources dated 2001-08-09 or later.

	NetBSD 1.5.2 is not vulnerable.

	The following directories need to be updated from the
	netbsd-1-5 CVS branch:
		src/sbin/dump

	To update from CVS, re-build, and re-install dump and dump_lfs:

		# cd src
		# cvs update -d -P sbin/dump
		# cd sbin/dump

		# make cleandir dependall
		# make install
		# cd ../dump_lfs
		# make cleandir dependall
		# make install


	Alternatively, apply the following patch (with potential offset
	differences):
		ftp://ftp.netbsd.org/pub/NetBSD/security/patches/SA2001-014-dump-1.5.patch

	To patch, re-build and re-install dump and dump_lfs:

		# cd src/sbin/dump
		# patch < /path/to/SA2001-014-dump-1.5.patch

		# make cleandir dependall
		# make install
		# cd ../dump_lfs
		# make cleandir dependall
		# make install


* NetBSD 1.4, 1.4.1, 1.4.2, 1.4.3:

	The patch supplied for the 1.5 releases, also applies to
	1.4, 1.4.1, 1.4.2, and 1.4.3.

	Follow the instructions for using the patch as detailed in
	the NetBSD 1.5 section above.


Thanks To
=========

canis for raising the issue.

Matthew Green for a patch, and David Maxwell for revisions to the patch.

John Hawkinson for the patches for the NetBSD 1.5 branch.


Revision History
================

	2001-08-23	Initial release


More Information
================

An up-to-date PGP signed copy of this release will be maintained at
  ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2001-014.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/.


Copyright 2001, The NetBSD Foundation, Inc.  All Rights Reserved.

$NetBSD: NetBSD-SA2001-014.txt,v 1.8 2001/08/23 05:59:07 lukem Exp $

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