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Exploring New Frontiers
in Container Technology

James Bottomley
Twitter: @jejb_
About Me


Container evangelist

Open Source Advocate

  • Converting Business to Open Source

Kernel Developer

  • SCSI Subsystem Maintainer
  • PA-RISC architecture Maintainer
  • Containers
Container Basics

Hypervisors are based on emulating hardware

Containers are about virtualizing the Operating System subsystems

Containers: Single Kernel; Hypervisors: multiple kernels.

Immediate Benefit: One Kernel, one resource manager

Other container advantages: elasticity









Sharing is a key attribute that enables container agility

containers can be scaled instantly up or down (instant vertical scaling)

resource decisions can be made much more efficiently than hypervisors

Boxing just the application lead to the revolution in devops

However, Docker is nothing more than an application packaging and transport system

Devops today is all about easy deployment of boxed applications with a consistent environment

Unfortunately, sharing also increases the security risk of the containment system

A fact that Hypervisor advocates seek to exploit.

"Fake News"

Problem: Lack of facts around "security" make it hard to dispute

Linux Containers API

Kernel API is the same for all containers

Came from an Agreement at the Kernel Summit in 2011

Caused container interests to converge on a unified, upstream API

No repeat of Xen/KVM split

Led directly to the ability of Docker to run on upstream containers

Also rapidly evolving


Block I/O







Network NS


Mount NS



User NS

Cgroup NS

Docker is not the end of containers, it's just the begining

And the source of quite a few of our security issues

Countering the Hype

Need to find a measure to define "Security" or "Containment"

Best Candidate is Attack Profile

Vertical Attack Profile means my overall chance of my application being Hacked

Horizontal Attack Profile (HAP) means my overall chance of being hacked by my exposed shared code.


here is the measured HAP of Docker vs KVM as Kata Containers.

Containers with a good seccomp profile are not much worse than a hypervisor

Can Make "Attack Profile" more precise by equating it to number of Lines of Code traversed multiplied by exploitable defect density.

Once we have a measure, we can start to build a container description that minimizes HAP.

HAP advances the state of the art but is by no means the end point.

Problems with HAP as a Measure

If no-one can exploit your bug does it exist from a security perspective?

Need to incorporate "exploitability" as the next refinement for HAP

We suspect this means the interface description is the most important factor in exploitability

Some interfaces are inherantly more exploitable than others

Alternate Container Descriptions (Sandboxing)

Sandboxing means emulating some system calls for isolation instead of doing namespacing.

Emulation means code isn't shared and therefore the HAP is reduced (in theory)

Very difficult to get sandboxing right for containers without committing the hypervisor fault.

Well known Sandboxes are IBM Nabla and Google gvisor.

gvisor rewrites system calls in go for security

Nabla extracts unikernel techniques and fits them to a single process

However, we also try to keep sharing by using standard Linux memory management techniques.

What's Next

Is there some useful segmentation within the Linux Kernel?

Separation by address spaces within the kernel?

Run parts of the kernel with user context?

Use supervisors, like LSMs, to correct interface defects?

What about VAP ... HAP protects the operator rather than the application?

There's lots of exciting progress to be made in terms of simply exploring how to measure security.
There's even more exciting advances to be made in terms of securing containers (while preserving sharing)
More research into container security is needed to explore this.
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