Raesene's Ramblings

This week there was some research published from Cambridge university called “Trojan Codes”, around the potential risks of RTL unicode characters in source code. Whilst this is very much not a new problem, there have been various pieces of research over the years about the difficulties of handling unicode characters, it seemed like a good cue to look at this kind of issue in the context of Kubernetes. So far I’ve not found any security issues caused by this, but I found a couple of things which could be of interest, so thought I’d write it down, in case it’s useful to anyone.

I was playing around with CRDs today when I wondered “what would happen if I tried to overwrite one of Kubernetes’ core object types? The results weren’t what I expected, so thought it was worth writing it down, in case it comes as a surprise to others :) N.B. There’s an update at the bottom which sheds more light on what happens when you do this

One of the things that comes up a lot with Docker security is that, by default, the authorization model is all or nothing. Essentially any user or process that has access to the Docker socket (or Docker TCP port if it’s configured to listen on a network) can use any of its functions. This means that from a security standpoint essentially any user with Docker access can get root on the host easily.

I had cause to look into unprivileged binding of ports in Docker containers recently, and found a couple of things that were a surprise to me, so taking the time to write them down, in case it’s of use to anyone else.

I’ve always been a fan of spelunking around in Internet data sets to see what interesting things I can find, so when I saw that Censys had a new version of their search site, and that it had classified data about Kubernetes clusters, I had to have a look around :) Before I talk about the results, I will say I was very impressed by their new offering, the search speed is amazing for the amount of data and there’s some really useful search filters, some of which I’m using here.

Container image signing has been a bit of a gap in the security landscape, so I’m always interested in seeing new projects starting up which address it. Docker Content Trust/Notary never really gained traction in v1, and whilst v2 looks very interesting, it’s still in the design phase (AFAIK).

Following on from looking at the escalate verb in Kubernetes RBAC, I thought it would be worth looking at another one of the unusual verbs you can see in Kubernetes RBAC, bind.

One of the interesting areas of Kubernetes to explore is how it handles networking, and this is a quick post looking at one assumption which can be made about Kubernetes networking and how it doesn’t always hold. Whilst Kubernetes can assign pod IP addresses on the same LAN as the host VM, it’s more normal for the CNI to hand out IP addresses from a separate range, and then implement some kind of overlay networking between the cluster nodes to get traffic from pods on one node, to pods on other nodes. As part of this duty, Kubernetes nodes will often act as routers, so if you can get traffic to the node they’ll happily forward it on.

With the release of Docker 20.10, the rootless containers feature has left experimental status. This is an important step for Docker security as it allows for the entire Docker installation to run with standard user prvivileges, no use of root required. Other container solutions like Podman have had this feature for a while but if your used to Docker’s approach it’s nice to see it being available.

Following a recent run of the container security training course I do, I was poking around a bit with the escalate verb in Kubernetes RBAC and found some interesting points, so thought it’d be worth documenting, as it’s not necessarily the best known part of RBAC.