Tumblr Opensources Kubernetes Utilities | Hacker News Reader

Tumblr Opensources Kubernetes Utilities

engineering.tumblr.com

72 pointsbyxorna17 comments

My tinfoil hat is telling me that the engineers are pushing to open source as much as possible before the company inevitably goes under due to the recent banning of NSFW content.

That's actually not coming from the hat, you're receiving signals of the site's impending collapse through the foil. You way want to consider adding a few more layers.

Next week: “Tumblr open sources nudity classifier”

Not a cryptographer, but a few things irked me about the secret projector encryption features:

1. Calls it AES-CBC, but it's using AES-GCM https://github.com/tumblr/k8s-secret-projector/blob/master/p...

2. Encryption key generation (edited: from a password) uses a hash function rather than using a KDF. Short hashes are padded (takes first N bytes required to hit max length, appends to end) or trimmed to the appropriate length. https://github.com/tumblr/k8s-secret-projector/blob/master/p...

Fair points :)

Do you have any examples of using a KDF that jives with the bitlength requirements of a given cipher?

https://en.wikipedia.org/wiki/PBKDF2

Again, I'm not a cryptographer, and PBKDF2 is just an example. I would try to consult someone with a heavier background in the field. I've used PBKDF2 and Scrypt before, Argon2 is the newest, but also therefor least battle-tested.

https://godoc.org/golang.org/x/crypto/pbkdf2

https://godoc.org/golang.org/x/crypto/argon2

https://godoc.org/golang.org/x/crypto/scrypt

There's an RFC for that: https://tools.ietf.org/html/rfc5869

Doesn't look like the Go API[1] allows you to specify an output key material length, so you'd just truncate or iterate until you get however much material you need (The HKDF Wiki implementation does this[2]).

1: https://godoc.org/golang.org/x/crypto/hkdf

2: https://en.wikipedia.org/wiki/HKDF#Example:_Python_implement...

You don't want to generate key material from a password with hkdf. From the RFC:

On the other hand, it is anticipated that some applications will not be able to use HKDF "as-is" due to specific operational requirements, or will be able to use it but without the full benefits of the scheme. One significant example is the derivation of cryptographic keys from a source of low entropy, such as a user's password. The extract step in HKDF can concentrate existing entropy but cannot amplify entropy. In the case of password-based KDFs, a main goal is to slow down dictionary attacks using two ingredients: a salt value,and the intentional slowing of the key derivation computation. HKDF naturally accommodates the use of salt; however, a slowing down mechanism is not part of this specification. Applications interested in a password-based KDF should consider whether, for example, [PKCS5] meets their needs better than HKDF.

Ah, excuse my skimming. I wasn't aware it was being generated from a password. :x

I had another question regarding encryption of secrets. The reason you've mentioned is to prevent secrets from remaining in plain-text either during transmission to/from etcd or within etcd at rest.

Did you consider using https://kubernetes.io/docs/tasks/administer-cluster/encrypt-... instead? It has been there for quite some time (1.10 I think) and fixes all your concerns.

(We had similar issues with storing secrets in etcd, and went with k8s encryption instead).

That config injector seems super useful. I immediately start to wonder what subset of config options I can inject, and actually get the application to update.

K8s will update mounted ConfigMaps "live" in your pod, by updating a symlink. If your application is using inotify or file polling to watch the ConfigMap as a volume, you can reconfigure your app when changes happen (or signal your liveness probe you should be terminated to reload latest config).

This partly solves a big problem for me, which was how do I keep those configmaps up to date for a bunch of customers with a legacy application that writes UI config updates to a local xml config file. I wanted that file to live inside of configmaps but I have this problem. I already found a bash script that does inotify pushes to git (called git-watch), but I didn't have the other half of this equation. The missing half was getting those new config changes applied back into the configmap.

I hope Regulator has been decommissioned ;)

How did you see my Q1 TODO list?

;)

I miss Tumblr.

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