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Containers are great for isolating trusted applications from one another to ease deployment, but using them for multi-tenant security is ill advised.

Since all containers share the same kernel, any local privilege escalation vulnerability in Linux can be used to escape the container. Such vulnerabilities are much more common than vulnerabilities in mature hypervisors, so virtualization is the safer choice.

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This, and also bear in mind that kernel crypto state, particularly for the RNG, is shared.

Oh, fuck. I hadn't even thought of that. That's disaster.

only if you're expecting containers to somehow be a unicorn that lets you give people you don't know have your root password. :)

Could you explain what the implications are? I can see it going really bad if the simple dev/urandom is shared, but what are the practical risks for dev/random? (apart from the simple dos on host/all containers by draining)

Agree. I keep telling that container may provide some benefits but its really not security (especially docker which uses LXC which is still not complete und as you said uses a shared kernel - one plus point is Ubuntu's combination with AppArmor which mitigates certain attacks but configuring AppArmor is itself often overseen. Other distros are worse).

If you want to secure one app from another, just use separate hardware.

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