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Balkrishna Pandey
Balkrishna Pandey

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How to manage secrets in OpenShift/Kubernetes using Vault and External Secrets

Objective

The overall objective of this POC is to secure our application secrets and integrate them into our GitOps workflow. To accomplish this objective, I am going to utilize Hashicorp Vault to store our secure data and External Secret Operator to secretly fetch those secrets from Vault and create Kubernetes secrets inside the Cluster.

Anyone who doesn't know about GitOps is a process where we are using Git in our day-to-day system admin operation as we are using it for the development process. The concept is quite popular and emerging these days.

Image description

Pre-requisite

  • helm version 3, follow official instruction for installation.
  • Access to working OpenShift Cluster. If you don't have Cluster for this particular POC, you can use Code Ready Container for your local development and testing. I have also created a youtube video that explains what Code Ready Container is and how you can start using it.
  • oc or kubectl CLI to interact with Openshift Cluster

youtube video

HashiCorp and External Secrets Operator

Vault

Vault Introduction

If you don't know what Vault is, I suggest reading this excellent official article. Directly from the article, "Vault is an identity-based secret and encryption management system." A secret can be anything we want to secure, and for our use case, we want to secure a couple of secrets like BMC Secrets, Quay Pull Secrets, Github Secrets.

Vault Installation

We are using helm version 3 to install the vault.

$ helm repo add hashicorp https://helm.releases.hashicorp.com
"hashicorp" has been added to your repositories

$ helm search repo hashicorp/vault
NAME            CHART VERSION   APP VERSION DESCRIPTION
hashicorp/vault 0.19.0          1.9.2       Official HashiCorp Vault Chart
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For Openshift install, we have to override some of the values. The override creates a Vault cluster using the Raft integrated storage backend and deploys Vault in HA mode with three replicas.

Copy following content and save in file override-values.yaml

global:
  openshift: true

ui:
  enabled: true

injector:
  image:
    repository: "registry.connect.redhat.com/hashicorp/vault-k8s"
    tag: "0.14.2-ubi"

  agentImage:
    repository: "registry.connect.redhat.com/hashicorp/vault"
    tag: "1.9.2-ubi"

server:
  dataStorage: 
    enabled: true
    storageClass: ocs-storagecluster-cephfs
  route:
    enabled: true
    host: vault-server.apps.ztp-hub.ztp.home.lab
  image:
    repository: "registry.connect.redhat.com/hashicorp/vault"
    tag: "1.9.2-ubi"
  ha:
    enabled: true
    replicas: 3
    raft:
      enabled: true
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Now install Vault as follows,

oc new-project vault
helm install vault-server hashicorp/vault -f override-values.yaml
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Accessing Vault UI

This helm chart doesn't include Vault UI routes by default. Let's make the following OCP routes to get to the UI. Save the following text to the file route-vault-console.yaml and run oc apply -f route-vault-console.yaml to apply it.

kind: Route
apiVersion: route.openshift.io/v1
metadata:
  name: vault-console
  namespace: vault
  labels:
    app.kubernetes.io/instance: vault-server
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: vault-ui
    app.kubernetes.io/part-of: vault-server
    helm.sh/chart: vault-0.19.0
  annotations:
    openshift.io/host.generated: 'true'
spec:
  host: vault-console-vault.apps.ztp-hub.ztp.home.lab
  to:
    kind: Service
    name: vault-server-ui
    weight: 100
  port:
    targetPort: http
  wildcardPolicy: None
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Now you should be able to access UI from your browser, navigate to http://vault-console-vault.apps.ztp-hub.ztp.home.lab/

Vault Configuration

Next, initialize and unseal vault-server-0 pod:

oc exec -ti vault-server-0 -- vault operator init
oc exec -ti vault-server-0 -- vault operator unseal
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Finally, join the remaining pods to the Raft cluster and unseal them. The pods will need to communicate directly, so we'll configure the pods to use the internal service provided by the Helm chart:

oc exec -ti vault-server-1 -- vault operator raft join http://vault-server-0.vault-server-internal:8200
oc exec -ti vault-server-1 -- vault operator unseal

oc exec -ti vault-server-2 -- vault operator raft join http://vault-server-0.vault-server-internal:8200
oc exec -ti vault-server-2 -- vault operator unseal
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To verify if the Raft cluster has successfully been initialized, run the following.

First, log in using the root token on the vault-server-0 pod:

$ oc exec -ti vault-server-0 -- vault login
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Token (will be hidden): 
Success! You are now authenticated. The token information displayed below
is already stored in the token helper. You do NOT need to run "vault login"
again. Future Vault requests will automatically use this token.

Key-Value
---                  -----
token                s.tqN1UqGPJjtZKzILimuV7PfX
token_accessor       vusPbKI42SnRM4VHW2iLO5BK
token_duration       ∞
token_renewable      false
token_policies       ["root"]
identity_policies    []
policies             ["root"]
bpandey@Balkrishnas-MacBook-Pr
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Next, list all the raft peers:

oc exec -ti vault-server-0 -- vault operator raft list-peers
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Node                                    Address                                      State       Voter
----                                    -------                                      -----       -----
0c1af425-73c3-c369-886c-ee9dd95fe443    vault-server-0.vault-server-internal:8201    leader      true
7e3e94e1-3e14-00ff-3b77-b503a4df348b    vault-server-1.vault-server-internal:8201    follower    true
dc496945-b067-89e2-919d-fef47319d9fc    vault-server-2.vault-server-internal:8201    follower    true
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External Secret Operator (ESO)

External Secret Operator Introduction

If you don't know what External Secrets Operator is, I suggest reading this another excellent official article. The operator integrates external secret management systems like AWS Secrets Manager, HashiCorp Vault, Google Secrets Manager, Azure Key Vault, etc. This component reads data from external APIs and automatically injects the values into a Kubernetes Secret.

External Secret Operator Installation

We use helm to deploy External Secret Operator, which runs as a deployment resource within your Kubernetes cluster.

Let's install ESO as follows,

helm repo add external-secrets https://charts.external-secrets.io
helm install external-secrets \
   external-secrets/external-secrets \
    -n external-secrets \
    --create-namespace 
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Validate,

oc get po -n external-secrets
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NAME                               READY   STATUS    RESTARTS   AGE
external-secrets-b48757b96-kkwcd   1/1     Running   0          3d20h
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External Secret Operator Configuration

With the help of CustomResourceDefinitions, we can supply configuration to this operator so that it can access the Vault and create a Kubernetes secret. For our purpose, we are going to create the following two CRD definitions,

  1. ClusterSecretStore: is a cluster scoped SecretStore, its global to the Cluster that can be referenced by all ExternalSecrets from all namespaces.

Create a file cluster-secret-store.yaml with following content.

apiVersion: external-secrets.io/v1alpha1
kind: ClusterSecretStore
metadata:
  name: vault-backend
spec:
  provider:
    vault:
      server: "http://vault-server-internal.vault:8200"
      path: "secret"
      version: "v1"
      auth:
        tokenSecretRef:
          name: "vault-token"
          key: "token"
          namespace: vault
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In the above configuration file,

  • spec.provider.vault.server pointed to your vault server address. In this POC, both vault and external secrets operators are running in the same Cluster, so we use the Kubernetes service object to access the vault. If the Vault server is external, use the appropriate DNS name.
  • spec.provider.vault.path should be equals to secret, Vault itself implements lots of different secret engines, as of now, this operator only support the KV Secrets Engine.
  • spec.provider.vault.version, as per the documentation, this can be v1 and v2, but I saw some issue with the v2 version. I saw the following error message. So use v1 for now.
{"level":"error","ts":1646765745.1578374,"logger":"controllers.ExternalSecret","msg":"could not update Secret","ExternalSecret":"sno01/pullsecret-cluster-sno01","SecretStore":"/vault-backend","error":"could not get secret data from provider: key \"secret/openshiftpullsecret\" from ExternalSecret \"pullsecret-cluster-sno01\": cannot read secret data from Vault: Error making API request.\n\nURL: GET http://vault-server-internal.vault:8200/v1/secret/data/openshiftpullsecret\nCode: 404. Errors:\n\n","stacktrace":"sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile\n\t/home/runner/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.1/pkg/internal/controller/controller.go:114\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler\n\t/home/runner/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.1/pkg/internal/controller/controller.go:311\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\t/home/runner/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.1/pkg/internal/controller/controller.go:266\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2\n\t/home/runner/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.11.1/pkg/internal/controller/controller.go:227"}
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  • spec.provider.vault.auth.tokenSecretRef basically referencing to Kubernetes secrets. For simplicity, let's use the Vault root token here, which we generated as a part of the Vault initialization above.

First, generate base64 content with vault secrets token.

echo -n "s.tqN1UqGPJjtZKzILimuV7PfX" |base64 
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cy50cU4xVXFHUEpqdFpLeklMaW11VjdQZlg=
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Now create a file vault-token-secret.yaml with the following content, ensure token: cy50cU4xVXFHUEpqdFpLeklMaW11VjdQZlg= matches with your vault cluster root token.

---
apiVersion: v1
kind: Secret
metadata:
  name: vault-token
  namespace: vault
data:
  token: cy50cU4xVXFHUEpqdFpLeklMaW11VjdQZlg=
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Now apply both files as follows,

oc apply -f cluster-secret-store.yaml
oc apply -f vault-token-secret.yaml
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  1. ExternalSecret: This object describes what data should be fetched from the secret store (in this case, vault) and how the data should be transformed and saved as Kubernetes Secrets.

Create a file external-pullsecret-cluster.yaml with following content.

apiVersion: external-secrets.io/v1alpha1
kind: ExternalSecret
metadata:
  name: pullsecret-cluster-sno01
  namespace: sno01
spec:
  refreshInterval: "15s"
  secretStoreRef:
    name: vault-backend
    kind: ClusterSecretStore
  target:
    name: pullsecret-cluster-sno01
  data:
  - secretKey: .dockerconfigjson
    remoteRef:
      key: secret/openshiftpullsecret
      property: dockerconfigjson
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In the above configuration file,

  • spec.refreshInterval is the amount of time before the values reading again from the SecretStore provider. In this case, we are saying sync secrets every 15s. The valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h"
  • spec.secretStoreRef defines which SecretStore to use when fetching the secret data. You can have multiple SecretStore pointed to the different secret providers. In this case, we are pointing Vault using ClusterSecretStore created on step 1.
  • spec.target the Kubernetes secrets name you want to create.
  • spec.data this section defines the connection between the Kubernetes Secret keys and the Provider data. It's a list object, and you can fetch data from multiple endpoints. In this case, we say get property dockerconfigjson from vault endpoint secret/openshiftpullsecret and create Kubernetes secrets with the key name .dockerconfigjson with that vault data.

Let's visualize this with the actual use case. We don't have any secrets created so far in the Vault. Let's add some data inside the Vault as follows,

First, enable the kv endpoint as follows; this endpoint is not allowed by default.

oc exec -it vault-server-0 -- vault login
oc exec -it vault-server-0 -- vault secrets enable -path=secret/ kv
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Now add data,

oc exec -it vault-server-0 -- vault kv put secret/openshiftpullsecret dockerconfigjson='{"auths":{"cloud.openshift.com":{"auth":"3BlbnNoaWZ0LXJl==","email":"example@redhat.com"},"quay.io":{"auth":"ZZMVhJRUJUR1I3WUwxN05VMQ==","email":"example@redhat.com"},"registry.connect.redhat.com":{"auth":"3BlbnNoaWZ0LXJl==","email":"example@redhat.com"},"registry.redhat.io":{"auth":"==","email":"example@redhat.com"}}}'
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Now let's apply the ExternalSecret object created above.

oc apply -f external-pullsecret-cluster.yaml
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As soon as you apply this object, the External Secrets Operator will fetch data from the Vault and create Kubernetes Secrets in your sno01 namespace.

Let's Validate

As soon as the ExternalSecret manifest is created, the External Secrets controller creates a Kubernetes Secret on the Cluster that contains the secret saved in Vault.
So we should have the following object in a cluster

  • ExternalSecret
oc get externalsecret -n sno01 pullsecret-cluster-sno01
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NAME                        STORE           REFRESH INTERVAL   STATUS
pullsecret-cluster-sno01    vault-backend   15s                SecretSynced
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  • Kubernetes secret object created by External Secret Operator.
oc get secrets -n sno01 pullsecret-cluster-sno01
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NAME                        TYPE     DATA   AGE
pullsecret-cluster-sno01   Opaque   1      38s
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As you can see, a new secret is present with the following content, where base64 data matches Vault secrets content.

oc get secrets -n sno01 pullsecret-cluster-sno01 -o yaml
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apiVersion: v1
data:
  .dockerconfigjson: eyJhdXRocyI6eyJjbG91ZC5vcGVuc2hpZnQuY29tIjp7ImF1dGgiOiIzQmxibk5vYVdaMExYSmw9PSIsImVtYWlsIjoiZXhhbXBsZUByZWRoYXQuY29tIn0sInF1YXkuaW8iOnsiYXV0aCI6IlpaTVZoSlJVSlVSMUkzV1V3eE4wNVZNUT09IiwiZW1haWwiOiJleGFtcGxlQHJlZGhhdC5jb20ifSwicmVnaXN0cnkuY29ubmVjdC5yZWRoYXQuY29tIjp7ImF1dGgiOiIzQmxibk5vYVdaMExYSmw9PSIsImVtYWlsIjoiZXhhbXBsZUByZWRoYXQuY29tIn0sInJlZ2lzdHJ5LnJlZGhhdC5pbyI6eyJhdXRoIjoiPT0iLCJlbWFpbCI6ImV4YW1wbGVAcmVkaGF0LmNvbSJ9fX0=
...
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You may compare the decoded secret data to the secret you created earlier; both should match.

echo -n "eyJhdXRocyI6eyJjbG91ZC5vcGVuc2hpZnQuY29tIjp7ImF1dGgiOiIzQmxibk5vYVdaMExYSmw9PSIsImVtYWlsIjoiZXhhbXBsZUByZWRoYXQuY29tIn0sInF1YXkuaW8iOnsiYXV0aCI6IlpaTVZoSlJVSlVSMUkzV1V3eE4wNVZNUT09IiwiZW1haWwiOiJleGFtcGxlQHJlZGhhdC5jb20ifSwicmVnaXN0cnkuY29ubmVjdC5yZWRoYXQuY29tIjp7ImF1dGgiOiIzQmxibk5vYVdaMExYSmw9PSIsImVtYWlsIjoiZXhhbXBsZUByZWRoYXQuY29tIn0sInJlZ2lzdHJ5LnJlZGhhdC5pbyI6eyJhdXRoIjoiPT0iLCJlbWFpbCI6ImV4YW1wbGVAcmVkaGF0LmNvbSJ9fX0=" |base64 --decode
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{"auths":{"cloud.openshift.com":{"auth":"3BlbnNoaWZ0LXJl==","email":"example@redhat.com"},"quay.io":{"auth":"ZZMVhJRUJUR1I3WUwxN05VMQ==","email":"example@redhat.com"},"registry.connect.redhat.com":{"auth":"3BlbnNoaWZ0LXJl==","email":"example@redhat.com"},"registry.redhat.io":{"auth":"==","email":"example@redhat.com"}}}
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That's all for now. In this blog, we discussed how to use vault and the external-secrets operator to manage your secure data and how to securely roll out those secrets in a Kubernetes cluster.

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