The following examples show you how to configure the mutating webhook to best suit your environment.

The webhook checks if a container has environment variables defined in the following formats, and reads the values for those variables directly from Vault during startup time.

        env:
        - name: AWS_SECRET_ACCESS_KEY
          value: vault:secret/data/accounts/aws#AWS_SECRET_ACCESS_KEY
# or
        - name: AWS_SECRET_ACCESS_KEY
          valueFrom:
            secretKeyRef:
              name: aws-key-secret
              key: AWS_SECRET_ACCESS_KEY
# or
        - name: AWS_SECRET_ACCESS_KEY
            valueFrom:
              configMapKeyRef:
                name: aws-key-configmap
                key: AWS_SECRET_ACCESS_KEY

The webhook checks if a container has envFrom and parses the defined ConfigMaps and Secrets:

        envFrom:
          - secretRef:
              name: aws-key-secret
# or
          - configMapRef:
              name: aws-key-configmap

Secret and ConfigMap examples 🔗︎

Secrets require their payload to be base64 encoded, the API rejects manifests with plaintext in them. The secret value should contain a base64 encoded template string referencing the vault path you want to insert. Run echo -n "vault:secret/data/accounts/aws#AWS_SECRET_ACCESS_KEY" | base64 to get the correct string.

apiVersion: v1
kind: Secret
metadata:
  name: aws-key-secret
data:
  AWS_SECRET_ACCESS_KEY: dmF1bHQ6c2VjcmV0L2RhdGEvYWNjb3VudHMvYXdzI0FXU19TRUNSRVRfQUNDRVNTX0tFWQ==
type: Opaque
apiVersion: v1
kind: ConfigMap
metadata:
  name: aws-key-configmap
data:
  AWS_SECRET_ACCESSKEY: vault:secret/data/accounts/aws#AWS_SECRET_ACCESS_KEY

Inject secret into resources 🔗︎

The webhook can inject into any kind of resources, even into CRDs, for example:

apiVersion: mysql.example.github.com/v1
kind: MySQLCluster
metadata:
  name: "my-cluster"
spec:
  caBundle: "vault:pki/cert/43138323834372136778363829719919055910246657114#ca"

Inline mutation 🔗︎

The webhook also supports inline mutation when your secret needs to be replaced somewhere inside a string.

Set the annotation vault.security.banzaicloud.io/inline-mutation to true and:

apiVersion: v1
kind: Secret
metadata:
  name: aws-key-secret
data:
  config.yaml: >
foo: bar
secret: ${vault:secret/data/mysecret#supersecret}
type: Opaque

This works also for ConfigMap resources when configMapMutation is enabled. To enable inline mutation globally, set the env variable INLINE_MUTATION: true on the webhook.

You can specify the version of the injected Vault secret as well in the special reference, the format is: vault:PATH#KEY_OR_TEMPLATE#VERSION

Example:

        env:
        - name: AWS_SECRET_ACCESS_KEY
          value: vault:secret/data/accounts/aws#AWS_SECRET_ACCESS_KEY#2

Define multiple inline-secrets in resources 🔗︎

You can also inject multiple secrets under the same key in a Secret/ConfigMap/Object. This means that you can use multiple Vault paths in a value, for example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: sample-configmap
  annotations:
    vault.security.banzaicloud.io/vault-addr: "https://vault.default:8200"
    vault.security.banzaicloud.io/vault-role: "default"
    vault.security.banzaicloud.io/vault-tls-secret: vault-tls
    vault.security.banzaicloud.io/vault-path: "kubernetes"
    vault.security.banzaicloud.io/inline-mutation: "true"
data:
  aws-access-key-id: "vault:secret/data/accounts/aws#AWS_ACCESS_KEY_ID"
  aws-access-template: "vault:secret/data/accounts/aws#AWS key in base64: ${.AWS_ACCESS_KEY_ID | b64enc}"
  aws-access-inline: "AWS_ACCESS_KEY_ID: ${vault:secret/data/accounts/aws#AWS_ACCESS_KEY_ID} AWS_SECRET_ACCESS_KEY: ${vault:secret/data/accounts/aws#AWS_SECRET_ACCESS_KEY}"

This example also shows how a CA certificate (created by the operator) can be used with the vault.security.banzaicloud.io/vault-tls-secret: vault-tls annotation to validate the TLS connection in case of a non-Pod resource.

Request a Vault token 🔗︎

There is a special vault:login reference format to request a working Vault token into an environment variable to be later consumed by your application:

        env:
        - name: VAULT_TOKEN
          value: vault:login

Read a value from Vault 🔗︎

Values starting with "vault:" issue a read (HTTP GET) request towards the Vault API, this can be also used to request a dynamic database username/password pair for MySQL:

NOTE: This feature takes advantage of secret caching since we need to access the my-role endpoint twice, but in the background, it is written only once in Vault:

    env:
    - name: MYSQL_USERNAME
      value: "vault:database/creds/my-role#username"
    - name: MYSQL_PASSWORD
      value: "vault:database/creds/my-role#password"
    - name: REDIS_URI
      value: "redis://${vault:database/creds/my-role#username}:${vault:database/creds/my-role#password}@127.0.0.1:6739"

Write a value into Vault 🔗︎

Values starting with ">>vault:" issue a write (HTTP POST/PUT) request towards the Vault API, some secret engine APIs should be written instead of reading from like the Password Generator for HashiCorp Vault:

    env:
    - name: MY_SECRET_PASSWORD
      value: ">>vault:gen/password#value"

Or with Transit Secret Engine which is a fairly complex example since we are using templates when rendering the response and send data in the write request as well, the format is: vault:PATH#KEY_OR_TEMPLATE#DATA

Example:

    env:
    - name: MY_SECRET_PASSWORD
      value: ">>vault:transit/decrypt/mykey#${.plaintext | b64dec}#{"ciphertext":"vault:v1:/DupSiSbX/ATkGmKAmhqD0tvukByrx6gmps7dVI="}"

Templating in values 🔗︎

Templating is also supported on the secret sourced from Vault (in the key part, after the first #), in the very same fashion as in the Vault configuration and external configuration with all the Sprig functions (this is supported only for Pods right now):

    env:
    - name: DOCKER_USERNAME
      value: "vault:secret/data/accounts/dockerhub#My username on DockerHub is: ${title .DOCKER_USERNAME}"

In this case, an init-container will be injected into the given Pod. This container copies the vault-env binary into an in-memory volume and mounts that Volume to every container which has an environment variable definition like that. It also changes the command of the container to run vault-env instead of your application directly. When vault-env starts up, it connects to Vault to checks the environment variables. (By default, vault-env uses the Kubernetes Auth method, but you can also configure other authentication methods for the webhook.) The variables that have a reference to a value stored in Vault (vault:secret/....) are replaced with that value read from the Secret backend. After this, vault-env immediately executes (with syscall.Exec()) your process with the given arguments, replacing itself with that process (in non-daemon mode).

With this solution none of your Secrets stored in Vault will ever land in Kubernetes Secrets, thus in etcd.

vault-env was designed to work in Kubernetes in the first place, but nothing stops you to use it outside Kubernetes as well. It can be configured with the standard Vault client’s environment variables (because there is a standard Go Vault client underneath).

Currently, the Kubernetes Service Account-based Vault authentication mechanism is used by vault-env, so it requests a Vault token based on the Service Account of the container it is injected into.

Kubernetes 1.12 introduced a feature called APIServer dry-run which became beta as of 1.13. This feature requires some changes in webhooks with side effects. Vault mutating admission webhook is dry-run aware.

Mutate data from Vault and replace it in Kubernetes Secret 🔗︎

You can mutate Secrets (and ConfigMaps) as well if you set annotations and define proper Vault path in the data section:

apiVersion: v1
kind: Secret
metadata:
  name: sample-secret
  annotations:
    vault.security.banzaicloud.io/vault-addr: "https://vault.default.svc.cluster.local:8200"
    vault.security.banzaicloud.io/vault-role: "default"
    vault.security.banzaicloud.io/vault-skip-verify: "true"
    vault.security.banzaicloud.io/vault-path: "kubernetes"
type: kubernetes.io/dockerconfigjson
data:
  .dockerconfigjson: eyJhdXRocyI6eyJodHRwczovL2RvY2tlci5pbyI6eyJ1c2VybmFtZSI6InZhdWx0OnNlY3JldC9kYXRhL2RvY2tlcnJlcG8vI0RPQ0tFUl9SRVBPX1VTRVIiLCJwYXNzd29yZCI6InZhdWx0OnNlY3JldC9kYXRhL2RvY2tlcnJlcG8vI0RPQ0tFUl9SRVBPX1BBU1NXT1JEIiwiYXV0aCI6ImRtRjFiSFE2YzJWamNtVjBMMlJoZEdFdlpHOWphMlZ5Y21Wd2J5OGpSRTlEUzBWU1gxSkZVRTlmVlZORlVqcDJZWFZzZERwelpXTnlaWFF2WkdGMFlTOWtiMk5yWlhKeVpYQnZMeU5FVDBOTFJWSmZVa1ZRVDE5UVFWTlRWMDlTUkE9PSJ9fX0=

In the example above the secret type is kubernetes.io/dockerconfigjson and the webhook can get credentials from Vault. The base64 encoded data contain vault path in case of username and password for docker repository and you can create it with commands:

kubectl create secret docker-registry dockerhub --docker-username="vault:secret/data/dockerrepo#DOCKER_REPO_USER" --docker-password="vault:secret/data/dockerrepo#DOCKER_REPO_PASSWORD"
kubectl annotate secret dockerhub vault.security.banzaicloud.io/vault-addr="https://vault.default.svc.cluster.local:8200"
kubectl annotate secret dockerhub vault.security.banzaicloud.io/vault-role="default"
kubectl annotate secret dockerhub vault.security.banzaicloud.io/vault-skip-verify="true"
kubectl annotate secret dockerhub vault.security.banzaicloud.io/vault-path="kubernetes"

Use charts without explicit container.command and container.args 🔗︎

The Webhook can determine the container’s ENTRYPOINT and CMD with the help of image metadata queried from the image registry. This data is cached until the webhook Pod is restarted. If the registry is publicly accessible (without authentication) you don’t need to do anything, but if the registry requires authentication the credentials have to be available in the Pod’s imagePullSecrets section.

Some examples (apply cr.yaml from the operator samples first):

helm upgrade --install mysql stable/mysql \
  --set mysqlRootPassword=vault:secret/data/mysql#MYSQL_ROOT_PASSWORD \
  --set mysqlPassword=vault:secret/data/mysql#MYSQL_PASSWORD \
  --set "podAnnotations.vault\.security\.banzaicloud\.io/vault-addr"=https://vault:8200 \
  --set "podAnnotations.vault\.security\.banzaicloud\.io/vault-tls-secret"=vault-tls

Registry access 🔗︎

You can also specify a default secret being used by the webhook for cases where a pod has no imagePullSecrets specified. To make this work you have to set the environment variables DEFAULT_IMAGE_PULL_SECRET and DEFAULT_IMAGE_PULL_SECRET_NAMESPACE when deploying the vault-secrets-webhook. Have a look at the values.yaml of the vault-secrets-webhook helm chart to see how this is done.

Note:

  • If your EC2 nodes have the ECR instance role, the webhook can request an ECR access token through that role automatically, instead of an explicit imagePullSecret
  • If your workload is running on GCP nodes, the webhook automatically authenticates to GCR.

Future improvements:

  • on Azure/Alibaba get a credential dynamically with the specific SDK (for AWS ECR and GCP GCR this is already done)

Using a private image repository 🔗︎

# Docker Hub

kubectl create secret docker-registry dockerhub --docker-username=${DOCKER_USERNAME} --docker-password=$DOCKER_PASSWORD

helm upgrade --install mysql stable/mysql --set mysqlRootPassword=vault:secret/data/mysql#MYSQL_ROOT_PASSWORD --set "imagePullSecrets[0].name=dockerhub" --set-string "podAnnotations.vault\.security\.banzaicloud\.io/vault-skip-verify=true" --set image="private-repo/mysql"

# GCR

kubectl create secret docker-registry gcr \
--docker-server=gcr.io \
--docker-username=_json_key \
--docker-password="$(cat ~/json-key-file.json)"

helm upgrade --install mysql stable/mysql --set mysqlRootPassword=vault:secret/data/mysql#MYSQL_ROOT_PASSWORD --set "imagePullSecrets[0].name=gcr" --set-string "podAnnotations.vault\.security\.banzaicloud\.io/vault-skip-verify=true" --set image="gcr.io/your-repo/mysql"

# ECR

TOKEN=`aws ecr --region=eu-west-1 get-authorization-token --output text --query authorizationData[].authorizationToken | base64 --decode | cut -d: -f2`

kubectl create secret docker-registry ecr \
 --docker-server=https://171832738826.dkr.ecr.eu-west-1.amazonaws.com \
 --docker-username=AWS \
 --docker-password="${TOKEN}"

 helm upgrade --install mysql stable/mysql --set mysqlRootPassword=vault:secret/data/mysql#MYSQL_ROOT_PASSWORD --set "imagePullSecrets[0].name=ecr" --set-string "podAnnotations.vault\.security\.banzaicloud\.io/vault-skip-verify=true" --set image="171832738826.dkr.ecr.eu-west-1.amazonaws.com/mysql" --set-string imageTag=5.7

Mount all keys from Vault secret to env 🔗︎

This feature is very similar to Kubernetes’ standard envFrom: construct, but instead of a Kubernetes Secret/ConfigMap, all its keys are mounted from a Vault secret using the webhook and vault-env.

You can set the Vault secret to mount using the vault.security.banzaicloud.io/vault-env-from-path annotation.

Compared to the original environment variable definition in the Pod env construct, the only difference is that you won’t see the actual environment variables in the definition, because they are dynamic, and are based on the contents of the Vault secret’s, just like envFrom:.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-secrets
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: hello-secrets
  template:
    metadata:
      labels:
        app.kubernetes.io/name: hello-secrets
      annotations:
        vault.security.banzaicloud.io/vault-addr: "https://vault:8200"
        vault.security.banzaicloud.io/vault-tls-secret: vault-tls
        vault.security.banzaicloud.io/vault-env-from-path: "secret/data/accounts/aws"
    spec:
      initContainers:
      - name: init-ubuntu
        image: ubuntu
        command: ["sh", "-c", "echo AWS_ACCESS_KEY_ID: $AWS_ACCESS_KEY_ID && echo initContainers ready"]
      containers:
      - name: alpine
        image: alpine
        command: ["sh", "-c", "echo AWS_SECRET_ACCESS_KEY: $AWS_SECRET_ACCESS_KEY && echo going to sleep... && sleep 10000"]

Authenticate the webhook to Vault 🔗︎

By default, the webhook uses Kubernetes ServiceAccount-based authentication in Vault. Use the vault.security.banzaicloud.io/vault-auth-method annotation to request different authentication types from the following supported types: “kubernetes”, “aws-ec2”, “gcp-gce”, “jwt”. The following deployment - if running on a GCP instance - will automatically receive a signed-JWT token from the metadata server of the cloud provider, and use it to authenticate against Vault. The same goes for vault-auth-method: "aws-ec2", when running on an EC2 node with the right instance-role.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: vault-env-gcp-auth
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: vault-env-gcp-auth
  template:
    metadata:
      labels:
        app.kubernetes.io/name: vault-env-gcp-auth
      annotations:
        # These annotations enable Vault GCP GCE auth, see:
        # https://www.vaultproject.io/docs/auth/gcp#gce-login
        vault.security.banzaicloud.io/vault-addr: "https://vault:8200"
        vault.security.banzaicloud.io/vault-tls-secret: vault-tls
        vault.security.banzaicloud.io/vault-role: "my-role"
        vault.security.banzaicloud.io/vault-path: "gcp"
        vault.security.banzaicloud.io/vault-auth-method: "gcp-gce"
    spec:
      containers:
        - name: alpine
          image: alpine
          command:
            - "sh"
            - "-c"
            - "echo $MYSQL_PASSWORD && echo going to sleep... && sleep 10000"
          env:
            - name: MYSQL_PASSWORD
              value: vault:secret/data/mysql#MYSQL_PASSWORD