[13684] in bugtraq
Re: vulnerability in Linux Debian default boot configuration
daemon@ATHENA.MIT.EDU (Pierre Beyssac)
Thu Feb 3 13:40:26 2000
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Message-Id: <20000203145216.W50448@enst.fr>
Date: Thu, 3 Feb 2000 14:52:16 +0100
Reply-To: Pierre Beyssac <beyssac@ENST.FR>
From: Pierre Beyssac <beyssac@ENST.FR>
X-To: Brian Almeida <bma@debian.org>
To: BUGTRAQ@SECURITYFOCUS.COM
In-Reply-To: <20000203074852.A14013@debian.org>; from Brian Almeida on Thu,
Feb 03, 2000 at 07:48:52AM -0500
On Thu, Feb 03, 2000 at 07:48:52AM -0500, Brian Almeida wrote:
> A 100+ message flamewar on debian-devel@lists.debian.org isn't enough
> 'attention' for you, is it. It has been thoroughly discussed there. I invite
Except it happened the other way around: the flame war came just
after I wrote the post to Bugtraq. Check the date; I wrote it soon
after I got noticed that the priority of the bug report was
downgraded.
> anyone who wants to read the list archives (available on www.debian.org).
> In any case, it has been resolved.
Granted. But not with the resolution description you forwarded
("disables the floppy option from the first mbr prompt") : it was
not enough of a fix because it still allowed the "A" menu.
The final fix, which I tend to agree with, is to disable by default
the "extended features" of this MBR:
To: 56821-done@bugs.debian.org
Subject: Boot floppies 2.2.6 has been uploaded. (Was: Re: Bug#56821: [POSSIBLE GRAVE SECURITY HOLD])
Message-ID: <87u2jqizug.fsf_-_@bittersweet.intra>
Boot floppies 2.2.6 has been uploaded.
Starting with this version of `boot-floppies', `install-mbr' is run
with `--interrupt n', so that it is not interruptable during boot;
that is, holding shift will NOT display the MBR menu; it should
behave just like a standard MBR. At local option, that functionality
may be enabled by the system administrator, via the `install-mbr'
command.
You will find that `install-mbr --help' displays the following:
Usage: install-mbr [options] <target>
Options:
-f, --force Override some sanity checks.
-I <path>, --install <path> Install code from the specified file.
-k, --keep Keep the current code in the MBR.
-l, --list Just list the parameters.
-n, --no-act Don't install anything.
-o <offset>, --offset <offset> Install the MBR at byte offset <offset>.
-P <path>, --parameters <path> Get parameters from <path>.
-r, --reset Reset the parameters to the default state.
-T <path>, --table <path> Get partition table from <path>.
-v, --verbose Operate verbosely.
-V, --version Show version.
-h, --help Display this message.
Parameters:
-d <drive>, --drive <drive> Set BIOS drive number.
-e <option>, --enable <option> Select enabled boot option.
-i <mode>, --interrupt <keys> Set interrupt mode. (a/c/s/cs/n)
-p <partn>, --partition <partn> Set boot partition (0=whole disk).
-t <timeout>, --timeout <timeout> Set the timeout in 1/18 second.
Interrupt modes:
's'=Interrupt if shift or ctrl is pressed.
'k'=Interrupt if other key pressed.
'a'=Interrupt always.
'n'=Interrupt never.
Boot options:
'1','2','3' or '4' - Partition 1,2,3 or 4.
'F' - 1st floppy drive.
'A' - Advanced mode.
Report bugs to neilt@chiark.greenend.org.uk
From `dbootstrap' (the familiar Debian installer program on the
rescue floppy) right after opting to install `mbr', a message dialog
will be displayed (unless the "quiet" bootarg was given) with the
following to say:
----------------------------------------------------------------------
Important Information about the installed MBR
The master boot record program that was just installed supports
several advanced options that have not been enabled by default.
The installed configuration will cause it to behave just like a
standard MBR. For information about the advanced features
supported by the mbr, please read the 'install-mbr' manual page.
----------------------------------------------------------------------
I have verified that the `install-mbr' man page is installed with the
base system. It will be available for reading after the standard
`man-db' setup is in place.
We hope that this will be sufficient grounds for closing bug #56821.
Karl M. Hegbloom <karlheg@debian.org>, on behalf of the `debian-boot'
team.
PS.
It has been brought up that _perhaps_ for `woody', an `mbr' and
`lilo' configuration widget can be added to `dbootstrap', allowing
one to enable and configure the advanced `mbr' functionality, and
even Lilo/Grub password access control features during installation.
--
Pierre Beyssac pb@enst.fr
