Date: 5 Apr 2004 09:02:35 -0000
From: Rene <[email protected]>
To: [email protected]Subject: SuSEs YaST Online Update - possible symlink attack
author:l0om - l0om[at]excluded.org - www.excluded.org
date:05.04.2004
product:SuSE 9.0 maybe lower
possible symlink attack in SuSEs YOU [YaST Online
Update]
in SuSE linux you can use YOU to auto update your
system.
you can do this by YaST or by hand with the command
"online_update".
as a normal user you can check for updates with the
options "-q" or "-k".
By doing this "online_update" will do the follwing:
creats a directory in /usr/tmp/you-$USER
in this direcoty it will creat the files "cookies",
"quickcheack" and "youservers" (furthermore
it creats some directorys- nevermind...).
it doesnt check for a allready existing directory
called "you-$USER" or for files like "cookies"
which may be there.
an attacker could create a directory like "/usr/tmp/
you-asdf" and put a link
there named "cookies" which points to a file in /
home/asdf he likes to overwrite.
then he should set the directory permissions on 777
otherwise the binary will fail to create files
in /usr/tmp/asdf.
now he have to get the user asdf to execute the "/
usr/bin/online_update" binary (maybe by mail or
write) and the file will be overwritten.
bye and have a lot of phun
l0om
