[VulnWatch] gfxboot allows boot password circumvention, SuSE 8.1 GRUB
From: Matthias Andree (matthias.andree@gmx.de)
Date: 12/14/02
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Date: Sat, 14 Dec 2002 02:18:44 +0100 From: Matthias Andree <matthias.andree@gmx.de> To: vulnwatch@vulnwatch.org, bugtraq@securityfocus.com
SECURITY VULNERABILITY
SuSE 8.1's "gfxmenu" which is configured into GRUB by default on many
machines allows the user to pass in additional kernel boot parameters
without entering the password, even though one is configured in the GRUB
configuration file. The exact circumstances when YaST2 adds the gfxmenu
configuration have not been researched. What other machines may be
affected, has not been researched either. SuSE used LILO up to and
including SuSE Linux 8.0.
HOW TO CHECK IF YOU ARE VULNERABLE
As no fix is known at the moment, just reading the /boot/grub/menu.lst
configuration file is sufficient. If yours has a line that starts with
"gfxmenu", the computer is vulnerable.
IMPACT
A malicious user who can make the computer reboot can for example append
init=/bin/bash to defeat the regular boot procedures to bypass the root
password and steal data or install backdoors.
FIX
Unknown.
WORKAROUND
Remove the gfxboot line from /boot/grub/menu.lst.
HISTORY AND FUTURE
2002-11-27 v1.0 initial announcement, disclosed to SuSE Security only.
2002-11-29 extended schedule to 2002-12-13, 24:00 GMT
2002-12-03 original schedule date for publication
2002-12-13 deadline. public announcement will be made on this day at the latest.
2002-12-13 v1.1 reword first paragraph, not all machines enable gfxmenu
by default, add section on checking for the problem.
2002-12-14 sent this announcement to vulnwatch and bugtraq, a workaround
is documented, so holding back the announcement makes no sense.
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