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Containers, Docker, and Security: State Of The Union (LinuxCon and ContainerCon 2015)

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Docker is two years old. While security has always been at the core of the questions revolving around Docker, the nature of those questions has changed. Last year, the main concern was "can I safely colocate containers on the same machine?" and it elicited various responses. Dan Walsh, SELinux expert, notoriously said: "containers do not contain!", and at last year's LinuxCon, Jérôme delivered a presentation detailing how to harden Docker and containers to isolate them better.

Today, people have new concerns. They include image transport, vulnerability mitigation, and more.

After a recap about the current state of container security, Jérôme will explain why those new questions showed up, and most importantly, how to address them and safely deploy containers in general, and Docker in particular.

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Containers, Docker, and Security: State Of The Union (LinuxCon and ContainerCon 2015)

  1. 1. Containers, Docker, and Security: State ofthe Union 1 / 38
  2. 2. Who am I? Jérôme Petazzoni (@jpetazzo) French software engineer living in California Joined Docker (dotCloud) more than 4 years ago (I was at Docker before it was cool!) I built and scaled the dotCloud PaaS (millions of containers, no known security issues) I learned a few things about running containers (in production) 2 / 38
  3. 3. Outline Yesterday Today Tomorrow 3 / 38
  4. 4. Yesterday 4 / 38
  5. 5. Containers and Security yesterday Last year, at LinuxCon... "Is it safe to run applications in containers?" 5 / 38
  6. 6. Containers and Security yesterday Last year, at LinuxCon... "Is it safe to run applications in containers?" really meant "Can one container break out, and into another?" 6 / 38
  7. 7. Containers and Security yesterday Last year, at LinuxCon... "Is it safe to run applications in containers?" really meant "Can one container break out, and into another?" Main concern: isolation 7 / 38
  8. 8. What was the answer? 8 / 38
  9. 9. What was the answer? 9 / 38
  10. 10. What was the answer? "It's complicated" Long list of recommendations some were easy (and automatically enforced by Docker) some were not obvious (and had to be enabled manually) some were hard to deploy (or required missing kernel features) Video and Slides 10 / 38
  11. 11. How is this different today? People still ask about container isolation Much more frequently, they ask about image security and provenance They want to know: if dockerpulldebianis what it claims to be if jpetazzo/dindhas vulnerabilities if a given image has been vetted by their sec team 11 / 38
  12. 12. Why has it changed? Who cares about container isolation? hosting providers (more density = more $$$) PAAS (for rapid deployment; on-demand activation) → early adopters Who doesn't care about container isolation? people who use VMs only because autoscaling people who would put multiple components per machine anyway → second wave of users 12 / 38
  13. 13. Today 13 / 38
  14. 14. Docker and Containers Security Today Improving what we had yesterday (fine-grained permissions, immutable containers) Addressing new challenges (provenance, content verification, notary) Defense in depth (containers + VM) The infosec mindset (better upgrades, security benchmarks, policies) 14 / 38
  15. 15. Finer-grained permissions Per-container ulimit Capability reduction --cap-drop/ --cap-add e.g.: --cap-addnet_admin Device access restrictions --device(better than --privileged!) Improved handling of LSM (SELinux, AppArmor) 15 / 38
  16. 16. Smaller attack surface Hardware management done on the host (no kernel, drivers, device handling... in containers) Package management is optional (once a container is built, it doesn't need to be changed) Minimal distros can be used (e.g. buildroot, Alpine Linux...) Less software = less risk 16 / 38
  17. 17. Immutable containers dockerrun--read-only (makes it impossible to entrench in a container) Helps with vulnerability detection (audit can be performed on offline images) Even without --read-onlyflag: copy-on-write prevents changes from being permanent break a container when hacking it → it gets recycled dockerdiffallows easy audit of changes 17 / 38
  18. 18. Image provenance How can I trust dockerpulldebian? I must trust upstream (i.e. Debian and whoever maintains the image) I must trust Docker Inc. (operator of the Hub) I must trust the transport (between the Hub and my Docker host) 18 / 38
  19. 19. Image provenance How can I trust dockerpulldebian? I must trust upstream (i.e. Debian and whoever maintains the image) I must trust Docker Inc. (operator of the Hub) I must trust the transport (between the Hub and my Docker host) That's a lot of trust 19 / 38
  20. 20. "I don't want to trust anybody!" If you don't trust upstream, you have to ... stop using apt-getand yumwith public repos rebuild everything from source verify source integrity (full audit + review all changes) If you don't trust Docker Inc., you probably should ... audit the whole Docker Engine code audit every single patch that goes into Docker (if you can do that ... we're looking for reviewers) 20 / 38
  21. 21. Security reminder It's OK to be paranoid, but beware of: Bumps in the carpet (moving a problem rather than solving it) Usability (if security makes it hard/impossible to work, people will work around it!) Tinfoil hats 21 / 38
  22. 22. Can we trust the transport? Registry v1 protocol had serious issues: arbitrary layer IDs no integrity check (other than TLS transport integrity) Registry v2 protocol has: content-based layer IDs signed image manifests Is that enough? 22 / 38
  23. 23. Notary: a better trust framework 23 / 38
  24. 24. What are we trying to address? Distributed content should be signed Stealing a key should be hard Stealing a key shouldn't have dire consequences Replay attacks should be hard (=can't serve you yesterday's vulnerable version) Should use known models and research Existing distribution infrastructure should be used (=HTTP, HTTPS, FTP… are good) Trusting Docker Hub should not be mandatory 24 / 38
  25. 25. Notary Based on TUF (The Update Framework) Sign content with offline keys Trust thresholds (require K out of N keys) (Stealing a key reduces signing requirements, but doesn't break the whole model) Guarantee freshness Distribute signed content on (potentially insecure) servers (leverage existing (insecure) transport and mirrors) Enabled in Docker 1.8 by setting DOCKER_CONTENT_TRUST 25 / 38
  26. 26. Defense in depth So, VM or containers? 26 / 38
  27. 27. Defense in depth So, VM or containers? VM and containers! 27 / 38
  28. 28. Defense in depth So, VM or containers? VM and containers! Reduce number of VMs (when security perimeter allows it) Colocated containers are safer than colocated processes Malicious code has to escape both layers Docker provides an extra layer of isolation Applications are safer with containers than without 28 / 38
  29. 29. The infosec mindset Better upgrades Accurate, actionable security benchmarks Clear, sensible security policies 29 / 38
  30. 30. Better upgrades Dockerfile= easy, fast, reliable builds and rebuilds "But now I have 1000s of container images to upgrade!" Yes, but that's way better than the 100s of server images that you had before The organizational risk is lower (because if something goes wrong, you have reliable rollbacks) 30 / 38
  31. 31. Security benchmarks CIS (Center of Internet Security) Docker Benchmark Docker Bench (https://dockerbench.com) : automated assessment tool to check compliance 31 / 38
  32. 32. Policies Docker Inc. (the company) and the Docker Project (open source) have clear security guidelines Mandatory code reviews (see CONTRIBUTING.md) to ensure quality of code base Quarterly security audits and pen tests of our infrastructure We support responsible disclosure 32 / 38
  33. 33. Tomorrow 33 / 38
  34. 34. Container security in the future Personal predictions - not Docker Inc.'s roadmap! 34 / 38
  35. 35. Container security in the future Personal predictions - not Docker Inc.'s roadmap! Offline image audit Hardening of immutable containers (noexec, nosuid) Better GRSEC, PAX, LSM integration User namespaces (eventually!) Better default seccomp profiles 35 / 38
  36. 36. Last words David Mortman at DEFCON this year: “ A year ago, [Docker and security] was pretty horrible, six months ago it wasn't so bad, and now it's pretty usable. 36 / 38
  37. 37. Resources Docker security page Docker security presentation at DockerCon 2015 SF Docker Security CheatSheet Notary on GitHub Docker Bench for Security 37 / 38
  38. 38. Thanks! Questions? @jpetazzo @docker 38 / 38

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