I’ve been doing some work for an upcoming talk on Kubernetes Multi-tenancy security, and as part of that I was thinking about one of my favourite topics in Kubernetes security, SSRF. As I was doing that I realised that applying a known existing weakness in Kubernetes security could be used by attackers to get unauthorised to other tenant’s workloads in a multi-tenant cluster.
Full disclosure, this is one of those posts I do where there’s no dramatic pay off at the end, it’s just documenting something I found that took me a while to figure out and that I thought was interesting :)
The questions of whether containers really contain has been an active topic of debate since pretty much as long as containers have been in use and the answer, like most things in security, is it depends! Security isn’t an absolute but calculations do change with new threats and tools and I think that that kind of change is happening at the moment with regards to Docker style containers and how much you can rely on their isolation.
For a long time I wanted a piece of software that used Firecracker to create MicroVMs on my Linux hosts. It seemed like it would be really useful for vulnerability research and testing features that weren’t suitable to be done in Docker containers. I looked around periodically but wasn’t able to find anything that really fit the bill and would work easily.
One of the points I tend to make in my talks about Kubernetes security is that it’s quite difficult to talk about what the security defaults are, as there are over 150 different Kubernetes distributions and services and each one of them has a different idea of what their security defaults should be.
I’ve been doing a talk on Kubernetes post-exploitation for a while now and one of requests has been for a blog post to refer back to, which I’m finally getting around to doing now!
Update Looks like Bitnami decided to take some more time over this details here and have some 1-day brown outs before removing the repos on Sept 29.
This exploration started, as many do, with “huh that’s odd”. Specifically I was looking at the output of amicontained around filtered syscalls.
I got a lesson today in the idea that it’s always worth re-visiting things you’ve used in the past to see how they’ve changed, as sometimes there will be cool new features!
I was looking at a Kubernetes issue the other day and it led me down a kind of interesting rabbit hole, so I thought it’d be worth sharing as I learned a couple of things.
