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Container Escapes 101 - Setup

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By Natalie Somersall
3 min read
Container Escapes 101 - Setup

Some logistics

This is a 2 hour workshop. It may take you more or less time and that’s okay! All the material is here, so hopefully no one is stressed about any time pressure.

You’ll need a few things:

  • A Linux virtual machine (Ubuntu 24.04 and Fedora 42 tested), local or in AWS or Azure
  • A container runtime on that VM (Docker Community Edition is what’s tested here)
  • Broadband internet, as we’ll be downloading quite a few container images
  • Probably a lack of corporate “auto-installed” stuff in your environment

If you want, I made an Ubuntu 24.04 VM for UTM (read a Mac GUI for QEMU ) that has a few things pre-installed. The “post-install” script is in (GitHub ). It also has SSH in the guest VM mapped to TCP port 3022 on the host.

  • (optional) VM download on Google Drive
  • login = user / password
  • copy/paste SSH command = ssh -p 3022 user@127.0.0.1

⛳️ There’s a plain text file at /boot/flag.txt that’ll serve as read and/or write proof as we go along. If you’re making your own VM to follow along, here’s the quick one-liner to add it:

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echo "hiya, you found me at appsec village @ defcon 33!" | \
  tee -a /boot/flag.txt

📦 There are also a few ports forwarded between the host and the VM.

Host port VM port Notes
3022 22 SSH
3080 80 HTTP with a web server
5000 5000 HTTP in a Flask webapp

The setup script I used on the VMs, Dockerfiles of any containers built for this, and more are in GitHub .

Hope it went without saying, but … uh … don’t use your company’s real accounts and infrastructure and such. This was tested on QEMU (arm64 and x86_64), but should work just as well on the free tiers of AWS and Azure. No $$$ should be needed here.

Image list

To run this in an airgap, here’s a list of the images used throughout the workshop. A small shell script to pull them all is available in GitHub .

  • docker.io/library/ubuntu:24.04
  • docker.io/redhat/ubi9:9.6
  • ghcr.io/some-natalie/some-natalie/whoami:latest
  • cgr.dev/chainguard/python:latest
  • cgr.dev/chainguard/curl:latest
  • docker.io/library/nginx:latest
  • ghcr.io/some-natalie/some-natalie/cowsay:latest
  • ghcr.io/some-natalie/some-natalie/secret-example:latest
  • ghcr.io/some-natalie/some-natalie/command-injection:latest
  • ghcr.io/some-natalie/some-natalie/command-injection-noshell:latest
  • ghcr.io/some-natalie/some-natalie/command-injection-noshell-noroot:latest

You’ll also need the static binaries hosted at http://files.some-fantastic.com . You may also need to do a bit of editing on package repositories, DNS, and other papercuts … but also, if this is your situation, I’m assuming you’re used to it and know what needs a tweak here and there. 🙈

Weirdness and other tips, tricks, and such.

DNS in a container in a VM to the host can get hairy (usually MTU … but we all have our suspicions). Sometimes it’s helpful to explicitly specify the DNS server in the container. For example, if you’re using Docker, you can do this:

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docker run -it --dns 8.8.8.8 ubuntu:24.04

Alternatively, altering the host VM’s DNS settings to add another server works too.

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sudo resolvectl dns enp0s1 8.8.8.8

Back to the index.

This post is licensed under CC BY-NC-SA 4.0 by the author.