How not to overwrite randomly generated secrets in Helm templates - kubernetes

Question

I want to generate a password in a Helm template, this is easy to do using the randAlphaNum function. However the password will be changed when the release is upgraded. Is there a way to check if a password was previously generated and then use the existing value? Something like this:
apiVersion: v1
kind: Secret
metadata:
name: db-details
data:
{{ if .Secrets.db-details.db-password }}
db-password: {{ .Secrets.db-details.db-password | b64enc }}
{{ else }}
db-password: {{ randAlphaNum 20 | b64enc }}
{{ end }}

Answer 1

You can build on shaunc's idea to use the lookup function to fix the original poster's code like this:
apiVersion: v1
kind: Secret
metadata:
name: db-details
data:
{{- if .Release.IsInstall }}
db-password: {{ randAlphaNum 20 | b64enc }}
{{ else }}
# `index` function is necessary because the property name contains a dash.
# Otherwise (...).data.db_password would have worked too.
db-password: {{ index (lookup "v1" "Secret" .Release.Namespace "db-details").data "db-password" }}
{{ end }}
Only creating the Secret when it doesn't yet exist won't work because Helm will delete objects that are no longer defined during the upgrade.
Using an annotation to keep the object around has the disadvantage that it will not be deleted when you delete the release with helm delete ....

Answer 2

I've got a lot of trouble with the answers from Jan Dubois and shaunc. So I built a combined solution.
The downside of Jan's answer: It leads to errors, when it is used with --dry-run.
The downside of shaunc's answer: It won't work, because the resources will be deleted on helm upgrade.
Here is my code:
# store the secret-name as var
# in my case, the name was very long and containing a lot of fields
# so it helps me a lot
{{- $secret_name := "your-secret-name" -}}
apiVersion: v1
kind: Secret
metadata:
name: {{ $secret_name }}
data:
# try to get the old secret
# keep in mind, that a dry-run only returns an empty map
{{- $old_sec := lookup "v1" "Secret" .Release.Namespace $secret_name }}
# check, if a secret is already set
{{- if or (not $old_sec) (not $old_sec.data) }}
# if not set, then generate a new password
db-password: {{ randAlphaNum 20 | b64enc }}
{{ else }}
# if set, then use the old value
db-password: {{ index $old_sec.data "db-password" }}
{{ end }}

Answer 3

It's still one of the biggest issues of Helm. As far as I understand no good solution is available yet (see https://github.com/helm/charts/issues/5167).
One dirty workaround is to create secret as pre-install hook. Obvious downside of this approach is that secret will not be deleted on helm delete.
apiVersion: v1
kind: Secret
metadata:
name: {{ template "helm-random-secret.fullname" . }}
annotations:
"helm.sh/hook": "pre-install"
"helm.sh/hook-delete-policy": "before-hook-creation"
labels:
app: {{ template "helm-random-secret.name" . }}
chart: {{ template "helm-random-secret.chart" . }}
release: {{ .Release.Name }}
heritage: {{ .Release.Service }}
data:
some-password: {{ default (randAlphaNum 10) .Values.somePassword | b64enc | quote }}

Answer 4

Building on shaunc's idea to use the lookup function, I've created the following template:
{{/*
Returns a secret if it already in Kubernetes, otherwise it creates
it randomly.
*/}}
{{- define "getOrGeneratePass" }}
{{- $len := (default 16 .Length) | int -}}
{{- $obj := (lookup "v1" .Kind .Namespace .Name).data -}}
{{- if $obj }}
{{- index $obj .Key -}}
{{- else if (eq (lower .Kind) "secret") -}}
{{- randAlphaNum $len | b64enc -}}
{{- else -}}
{{- randAlphaNum $len -}}
{{- end -}}
{{- end }}
Then you can simply configure secrets like:
---
apiVersion: v1
kind: Secret
metadata:
name: my-secret
type: Opaque
data:
PASSWORD: "{{ include "getOrGeneratePass" (dict "Namespace" .Release.Namespace "Kind" "Secret" "Name" "my-secret" "Key" "PASSWORD") }}"

Answer 5

You can use the lookup function and skip generation if secret already exists:
{{- if not (lookup "v1" "secret" .Release.Namespace "db-details") -}}
<create secret here>
{{- end -}}

Answer 6

The actual tools are all here. My workaround is just another combination of suggested tools
{{- if not (lookup "v1" "Secret" .Release.Namespace "mysecret") }}
apiVersion: v1
kind: Secret
metadata:
name: mysecret
annotations:
"helm.sh/resource-policy": "keep"
type: Opaque
stringData:
password: {{ randAlphaNum 24 }}
{{- end }}
So if there is no such secret, it will be created. If the secret is present, it will be removed from the chart, but not from the cluster, the "helm.sh/resource-policy": "keep" will prevent it.
You may ask (as someone already did above) why lookup, not .Release.IsUpdate. Imagine the situation: your secret is a password to a database. You keep the data in the persistent volume, the claim for which is also annotated by "helm.sh/resource-policy": "keep", so if you even uninstall and reinstall the chart, the data would persist. If you do so with .Release.IsUpdate as condition, then you password will be recreated, the old password will be lost and you will loose the access to your data. If you query for the secret existence, it won't happen.

Answer 7

I've rewritten kubernetes replicator and added some annotations to deal with this kind of problems: https://github.com/olli-ai/k8s-replicator#use-random-password-generated-by-an-helm-chart
Now can generate a random password with helm, and replicate it only once to another secret thus it won't be change by helm in the future.
apiVersion: v1
kind: Secret
type: Opaque
metadata:
name: admin-password-source
annotations:
k8s-replicator/replicate-to: "admin-password"
k8s-replicator/replicate-once: "true"
stringData:
password: {{ randAlphaNum 64 | quote }}
Hope it will help people.

Answer 8

You can leverage definitions in the _helpers.tpl
_helpers.tpl
{{/*
Create the secret name
*/}}
{{- define "mssql-server.secretName" -}}
{{- include "mssql-server.name" . }}-mssql-secret
{{- end }}
{{/*
Get sa password value
*/}}
{{- define "mssql-server.sapassword" -}}
{{- if .Release.IsInstall -}}
{{ .Values.sa_password | default (randAlphaNum 20) | b64enc | quote }}
{{- else -}}
{{ index (lookup "v1" "Secret" .Release.Namespace (include "mssql-server.secretName" .)).data "sa_password" }}
{{- end }}
{{- end }}
secret.yaml
apiVersion: v1
kind: Secret
metadata:
name: {{ include "mssql-server.secretName" . }}
labels:
{{- include "mssql-server.labels" . | nindent 4 }}
type: Opaque
data:
sa_password: {{ include "mssql-server.sapassword" . }}

Answer 9

A bit late here, and most people may just catch it in the documentation:
helm does this for you with the annotation "helm.sh/resource-policy": keep
see:
https://helm.sh/docs/howto/charts_tips_and_tricks/#tell-helm-not-to-uninstall-a-resource