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TESO Security Advisory
09/03/2000
atsadc local root compromise
Summary
===================
The atsar application contains an exploitable vulnerability.
The Halloween 4 Linux distribution, which is based on RedHat 6.1 is
shipped with this suid-root program. It might be used to gain superuser
privileges.
Systems Affected
===================
Halloween 4 Linux distribution, maybe others too.
Any system that has atsar-linux-1.4.2 package installed.
Tests
===================
liane:[bletchley]> id -a
uid=501(bletchley) gid=501(bletchley) groups=501(bletchley)
liane:[bletchley]> uname -a
Linux liane.c-skills.de 2.2.13-13 #21 Thu Mar 2 10:36:13 WET 2000 i686 unknown
liane:[bletchley]> stat `which atsadc`
File: "/usr/sbin/atsadc"
Size: 16000 Filetype: Regular File
Mode: (4755/-rwsr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Device: 3,1 Inode: 117038 Links: 1
Access: Thu Mar 9 10:09:37 2000(00000.01:02:49)
Modify: Tue Nov 9 23:57:50 1999(00120.11:14:36)
Change: Tue Mar 7 14:55:23 2000(00001.20:17:03)
liane:[bletchley]> cd atsar-hack/
liane:[atsar-hack]> ./ass.pl
Creating hijack-lib ...
Compiling hijack-lib ...
Compile shell ...
Invoking vulnerable program (atsadc)...
sh: error in loading shared libraries:
sh: error in loading shared libraries:
Welcome. But as always: BEHAVE!
sh-2.03# id -a
uid=0(root) gid=0(root) groups=501(bletchley)
sh-2.03#
We've created a full working root-exploit which can be obtained from
[1] or [2].
To work properly the /etc/ld.so.preload file must not exist.
If it already exist, attackers may use other config-files to gain
root access.
Impact
===================
The vulnerable program 'atsadc' is shipped on the power-tools/contrib
CD and comes per default suid root (package "atsar-linux").
Attackers might use this program with obscure command-line-options to
gain locally root-access.
Explanation
===================
Atsadc doesn't properly check permissions of the output-file given
on the command-line. Rather it opens the file without the O_EXCL flag,
allowing an attacker to overwrite any file he wishes.
Due to the nice mode of 0664 an attacker may even create new files where
he has write-access too (group -rw).
In interaction with other linux 'system-tools' he can gain root-access.
Solution
===================
Remove the suid-bit.
The vendor and the author has been informed before, so a patch is already
available.
Acknowledgments
================
The bug-discovery, further analyzation and the exploit was done by
S. Krahmer -- http://www.cs.uni-potsdam.de/homepages/students/linuxer/
This advisory has been written S. Krahmer
Contact Information
===================
The TESO crew can be reached by mailing to tesopubat_private
Our web-page is at http://teso.scene.at/
"C-Skills" developers may be reached through [1].
References
===================
[1] S. Krahmer, C-Skills
http://www.cs.uni-potsdam.de/homepages/students/linuxer/
[2] TESO
http://teso.scene.at
Disclaimer
===================
This advisory does not claim to be complete or to be usable for any
purpose. Especially information on the vulnerable systems may be
inaccurate or wrong. The supplied exploit is not to be used for malicious
purposes, but for educational purposes only.
This advisory is free for open distribution in unmodified form.
Articles that are based on information from this advisory should include
link [1] and [2].
Exploit
===================
We've created a working exploit to demonstrate the vulnerability.
The exploit is available on either
http://teso.scene.at/
or
http://www.cs.uni-potsdam.de/homepages/students/linuxer/
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This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 15:39:36 PDT