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Category: Computer Science

Signed pointers

So those real hackers keep telling me that back then in the times of the LISP machine they had tagged pointers and stuff.

Those pesky mobile Whizkids at Qualcomm could not let that stand, so they created signed pointers for ARM 8.3. Two families of new instructions have been made, one for signing pointers, the other for checking the signature. How does that work? The PDF at Qualcomm describes the details.

Basically, when pushing a return address onto the stack on subroutine call, that pointer is authenticated with a PAC* instruction, on return that pointer is checked with an AUT* instruction. The actual RET will fail with an address violation if the pointer has been messed with. PAC* and AUT* are out of NOP space, so they can be executed as NOPs on older CPUs.

PAC* signs the return address, AUT* checks it. On pre-8.3 CPUs, they decode as NOP instructions. RETing to an address that does not AUT is an illegal address exception.

A 64 bit pointer in an 40 bit cellphone processor is good for 24 bit signatures, but other partitions are possible depending on address space layout and size.

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Curlbash, and Desktop Containers

I was having two independent discussions recently, which started with some traditional Unix person condemning software installing with curlbash (“curl https://… | bash”), or even “curl | sudo bash”.

I do not really think this to be much more dangerous than the installation of random rpm or dpkg packages any more. Especially if those packages are unsigned or the signing key gets installed just before the package.

The threat model really became a different one in the last few years, and the security mechanism have had to change as well. And they have, UIDs becoming much less important.

Desktop containers and Sandboxes have become much more important, and segregation happens now at a much finer granularity (the app level) instead of the user level.

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The Illustrated Guide to Kubernetes

»The other day, my daughter sidled into my office, and asked me, “Dearest Father, whose knowledge is incomparable, what is Kubernetes?”

And I responded, “Kubernetes is an open source orchestration system for Docker containers. It handles scheduling onto nodes in a compute cluster and actively manages workloads to ensure that their state matches the users’ declared intentions. Using the concepts of “labels” and “pods”, it groups the container which make up an application into logical units for easy management and discovery.”

And my daughter said to me, “Huh?”

And so I give you…«

Video: https://www.youtube.com/watch?v=4ht22ReBjno

Comic: The Illustrated Guide to Kubernetes

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Back from Kubecon

Right on the heels of the Openshift Commons and co-located with them, Kubecon 2017 happened at the BCC in Berlin. Supposedly 1500 people attended, which was straining BCC’s capacity to the limit, especially on the A-level. Room A03, which hosted the “Deep Dive track” was continuously overcrowded and could not accommodate all interested people.

Also, this was the most noisy event I have been attending in a long time, especially in the vendor booth setup in B01/B02. On the other hand, the hallway track was exceptionally useful, especially if one escaped out the door, weather permitting, or upstairs.

Quite a bit of content was a duplicate from the Openshift Commons Gathering preceding the Kubecon, but the inclusion of rkt and containerd as CNCF projects have been news and are very welcome.

Especially rkt will be useful, as Docker is not doing very many useful things in the context of Kubernetes and rkt kind of restricts itself to doing only these useful things and not having any other, less useful (in the K8s context) code.

At the CoreOS booth I learned that rkt is right now not yet a drop-in replacement for Docker, but may well be soon – work is being done, and quickly.

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Back from Openshift Commons

So I have been to Berlin this week, for the Openshift Commons Gathering and Kubecon, and of course to meet a few Berliners.

Openshift is Redhats distribution of Google Kubernetes, plus their own enhancements. It is available on your own machines as Openshift Origin (the GPL version) or OCP (Open Container Project). Redhat also operates dedicated and public clouds based on this. The Openshift Commons Gathering is a meeting of the Openshift Users Community, Commons.

Commons was a nice and fine gathering in the basement level of the BCC, a single track event with a nice mix of users reporting back  their experience with Kubernetes and Openshift. In fact, Commons already had quite a bit of the content later duplicated in Kubecon, but in a smaller and less noisy setting.

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