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Re: usb_modeswitch/pppd -detach
From: srm <srm () suckless org>
Date: Sat, 21 Jan 2012 23:14:27 +0100


On Thu, Jan 19, 2012 at 01:07:02AM +0100, srm wrote:

morrn,


Impact
======

Low


Summary
=======

When using usb_modeswitch and invoking pppd from wvdial in -detach mode. a /tmp/debug
file is created. Local Attacker could overwrite arbitrary files.


Example
=======

,file /tmp/debug
debug: broken symbolic link to `/etc/nologin'

Insert stick and connect:

,su
Password:
,sh connect >/dev/null

,file debug
debug: symbolic link to `/etc/nologin'

,cd /etc && cat nologin
symlink-name: /devices/pci0000:00/0000:00:1a.7/usb1/1-3/1-3:1.0/ttyUSB0/tty

,ls -l nologin
-rw-r--r-- 1 root root 84 Jan 19 01:11 nologin


Software
========
archlinux: community/usb_modeswitch 1.2.1-1c
archlinux: core/ppp 2.4.5-3 (base)


Please verify. YMMV.


Greetings
srm

So, the problem is definitive in the community package of archlinux.
*sigh*. I checked version 1.2.2 from

http://www.draisberghof.de/usb_modeswitch/#download

It doesn't contain the '/tmp/debug' statement.

However: The following version has the debug statement:
https://www.archlinux.org/packages/community/i686/usb_modeswitch/

,grep -n '/tmp/debug' usb_modeswitch.sh
66:             echo "symlink-name: $2" >/tmp/debug


A possible quick fix could be to append $$:
66:             echo "symlink-name: $2" >/tmp/debug.$$

Greetings
srm

 

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