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Automatically generated secrets for Kubernetes

This repository contains a custom Kubernetes controller that can automatically create random secret values. This may be used for auto-generating random credentials for applications run on Kubernetes.

Security note

Older versions (>= 1.0.0) of this controller used the math/rand package for generating secrets, which is deterministic and not cryptographically secure (see #1 for more information). If you're already running this controller and want to regenerate all potentially compromised secrets, start the controller with the -regenerate-insecure flag (note that you will need to manually re-create any Pods using these secrets, though). When using the kubectl apply command from below, the new flag will be added to your Deployment automatically.

Deployment

Helm

The controller can be deployed using Helm.

You might want to take a look a the values.yaml to adjust the operator to your needs.

secretLength defines the length of the generated secret values.

watchNamespace defines, which namespaces should be watched for secret objects.

To watch a single namespace, set it to the desired namespace name. Multiple namespaces are supported and can be set as a comma-separated list: ns1,ns2.

If watchNamespace is set to the empty string value "", all namespaces will be watched.

Afterwards, deploy the operator using:

  1. Add the Mittwald-Charts Repo:

    $ helm repo add mittwald https://helm.mittwald.de
"mittwald" has been added to your repositories

$ helm repo update
Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "mittwald" chart repository
Update Complete. ⎈ Happy Helming!⎈

  2. Upgrade or install kubernetes-secret-generator:
    helm upgrade --install kubernetes-secret-generator mittwald/kubernetes-secret-generator

Manually

If you don't want to use helm, the required .yaml files can also be applied manually using kubectl apply:

$ make install

To uninstall, use:

$ make uninstall

Usage

This operator is capable of generating secure random strings and ssh keypair secrets.

The type of secret to be generated can be specified by the secret-generator.v1.mittwald.de/type annotation. This annotation can be added to any Kubernetes secret object in the operators watchNamespace.

Secure Random Strings

By default, the operator will generate secure random strings. If the type annotation is not present, it will be added after the first reconciliation loop and its value will be set to string.

To actually generate random string secrets, the secret-generator.v1.mittwald.de/autogenerate annotation is required as well. The value of the annotation can be a field name (or comma separated list of field names) within the secret; the SecretGeneratorController will pick up this annotation and add a field [or fields] (password in the example below) to the secret with a randomly generated string value.

apiVersion: v1
kind: Secret
metadata:
  name: string-secret
  annotations:
    secret-generator.v1.mittwald.de/autogenerate: password
data:
  username: c29tZXVzZXI=

after reconciliation:

apiVersion: v1
kind: Secret
metadata:
  name: string-secret
  annotations:
    secret-generator.v1.mittwald.de/type: string
    secret-generator.v1.mittwald.de/secure: "yes"
    secret-generator.v1.mittwald.de/autogenerate: password
    secret-generator.v1.mittwald.de/autogenerate-generated-at: "2020-04-03T14:07:47+02:00"
type: Opaque
data:
  username: c29tZXVzZXI=
  password: TWVwSU83L2huNXBralNTMHFwU3VKSkkwNmN4NmRpNTBBcVpuVDlLOQ==

SSH Key Pairs

To generate SSH Key Pairs, the secret-generator.v1.mittwald.de/type annotation has to be present on the kubernetes secret object.

The operator will then add two keys to the secret object, ssh-publickey and ssh-privatekey, each containing the respective key.

The Private Key will be PEM encoded, the Public Key will have the authorized-keys format.

apiVersion: v1
kind: Secret
metadata:
  annotations:
    secret-generator.v1.mittwald.de/type: ssh-keypair
data: {}

after reconciliation:

apiVersion: v1
kind: Secret
metadata:
  annotations:
    secret-generator.v1.mittwald.de/type: ssh-keypair
    secret-generator.v1.mittwald.de/autogenerate-generated-at: "2020-04-03T14:07:47+02:00"
type: Opaque
data:
  ssh-publickey: c3NoLXJzYSBBQUFBQ...
  ssh-privatekey: LS0tLS1CRUdJTi...

Operational tasks

  • Regenerate all automatically generated secrets:

    $ kubectl annotate secrets --all secret-generator.v1.mittwald.de/regenerate=true

  • Regenerate only certain fields, in case the secret is of the password type:

    $ kubectl annotate secrets --all secret-generator.v1.mittwald.de/regenerate=password1,password2