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Using AWS Secrets Manager CSI on Red Hat OpenShift on AWS with STS

Author Paul Czarkowski

last modified 2021-08-17

The AWS Secrets and Configuration Provider (ASCP) provides a way to expose AWS Secrets as Kubernetes storage volumes. With the ASCP, you can store and manage your secrets in Secrets Manager and then retrieve them through your workloads running on ROSA or OSD.

This is made even easier / more secure through the use of AWS STS and Kubernetes PodIdentity.

Prerequisites

Preparing Environment

  1. Validate that your cluster has STS

    oc get authentication.config.openshift.io cluster -o json \
    | jq .spec.serviceAccountIssuer
    

    You should see something like the following, if not you should not proceed, instead look to the Red Hat documentation on creating an STS cluster.

    "https://rh-oidc.s3.us-east-1.amazonaws.com/xxxxxx"
    
  2. Set SecurityContextConstraints to allow the CSI driver to run

    oc new-project csi-secrets-store
    oc adm policy add-scc-to-user privileged \
      system:serviceaccount:csi-secrets-store:secrets-store-csi-driver
    oc adm policy add-scc-to-user privileged \
      system:serviceaccount:csi-secrets-store:csi-secrets-store-provider-aws
    
  3. Create some environment variables to refer to later

    export ROSA_CLUSTER_NAME=my-cluster
    export ROSA_CLUSTER_ID=$(rosa describe cluster -c $ROSA_CLUSTER_NAME --output json | jq -r .id)
    export REGION=us-east-2
    export OIDC_ENDPOINT=$(oc get authentication.config.openshift.io cluster -o json | jq .spec.serviceAccountIssuer)
    export AWS_ACCOUNT_ID=`aws sts get-caller-identity --query Account --output text`
    export AWS_PAGER=""
    

Deploy the AWS Secrets and Configuration Provider

  1. Use Helm to register the secrets store csi driver

    helm repo add secrets-store-csi-driver https://kubernetes-sigs.github.io/secrets-store-csi-driver/charts
    
  2. Update your Helm Repositories

    helm repo update
    
  3. Install the secrets store csi driver

    helm upgrade --install -n csi-secrets-store csi-secrets-store-driver secrets-store-csi-driver/secrets-store-csi-driver
    
  4. Deploy the AWS provider

    kubectl -n csi-secrets-store apply -f \
      https://raw.githubusercontent.com/rh-mobb/documentation/main/docs/security/secrets-store-csi/aws-provider-installer.yaml
    
  5. Check that both Daemonsets are running

    kubectl -n csi-secrets-store get ds \
      csi-secrets-store-provider-aws \
      csi-secrets-store-driver-secrets-store-csi-driver
    

Creating a Secret and IAM Access Policies

  1. Create a secret in Secrets Manager

    SECRET_ARN=$(aws --region "$REGION" secretsmanager  create-secret \
      --name MySecret --secret-string \
      '{"username":"shadowman", "password":"hunter2"}' \
      --query ARN --output text)
    
    echo $SECRET_ARN
    
  2. Create IAM Access Policy document

    cat << EOF > policy.json
    {
      "Version": "2012-10-17",
      "Statement": [{
          "Effect": "Allow",
          "Action": [
            "secretsmanager:GetSecretValue",
            "secretsmanager:DescribeSecret"
          ],
          "Resource": ["$SECRET_ARN"]
          }]
    }
    EOF
    
  3. Create an IAM Access Policy

    POLICY_ARN=$(aws --region "$REGION" --query Policy.Arn \
      --output text iam create-policy \
      --policy-name openshift-access-to-mysecret-policy \
      --policy-document file://policy.json)
    echo $POLICY_ARN
    
  4. Create IAM Role trust policy document

    Note you can use Conditions to lock down to a specific namespace or service account here. But for simplicity we’re keeping it open.

    cat <<EOF > trust-policy.json
    {
    "Version": "2012-10-17",
    "Statement": [
      {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::$AWS_ACCOUNT_ID:oidc-provider/rh-oidc.s3.us-east-1.amazonaws.com/$ROSA_CLUSTER_ID"
      },
      "Action": "sts:AssumeRoleWithWebIdentity"
      }
    ]
    }
    EOF
    
  5. Create IAM Role

    ROLE_ARN=$(aws iam create-role --role-name openshift-access-to-mysecret \
      --assume-role-policy-document file://trust-policy.json \
      --query Role.Arn --output text)
    echo $ROLE_ARN
    
  6. Attach Role to the Policy

    aws iam attach-role-policy --role-name openshift-access-to-mysecret --policy-arn $POLICY_ARN
    

Create an Application to use this secret

  1. Create an OpenShift project

    oc new-project my-application
    
  2. Annotate the default service account to use the STS Role

    oc annotate -n my-application serviceaccount default \
      eks.amazonaws.com/role-arn=$ROLE_ARN
    
  3. Create a secret provider class to access our secret

    cat << EOF | kubectl apply -f -
    apiVersion: secrets-store.csi.x-k8s.io/v1
    kind: SecretProviderClass
    metadata:
      name: my-application-aws-secrets
    spec:
      provider: aws
      parameters:
        objects: |
            - objectName: "MySecret"
              objectType: "secretsmanager"
    EOF
    
  4. Create a Deployment using our secret

    cat << EOF | kubectl apply -f -
    apiVersion: v1
    kind: Pod
    metadata:
      name: my-application
      labels:
        app: my-application
    spec:
      volumes:
      - name: secrets-store-inline
        csi:
          driver: secrets-store.csi.k8s.io
          readOnly: true
          volumeAttributes:
            secretProviderClass: "my-application-aws-secrets"
      containers:
      - name: my-application-deployment
        image: k8s.gcr.io/e2e-test-images/busybox:1.29
        command:
          - "/bin/sleep"
          - "10000"
        volumeMounts:
        - name: secrets-store-inline
          mountPath: "/mnt/secrets-store"
          readOnly: true
    EOF
    
  5. Verify the Pod has the secret mounted

    kubectl exec -it my-application -- cat /mnt/secrets-store/MySecret
    

Cleanup

  1. Delete application

    oc delete project my-application
    
  2. Delete the secrets store csi driver

    helm delete -n kube-system csi-secrets-store
    
  3. Delete the AWS provider

    kubectl -n kube-system delete -f \
      https://raw.githubusercontent.com/aws/secrets-store-csi-driver-provider-aws/main/deployment/aws-provider-installer.yaml
    
  4. Delete Security Context Constraints

    oc adm policy remove-scc-from-user privileged \
      system:serviceaccount:kube-system:secrets-store-csi-driver
    oc adm policy remove-scc-from-user privileged \
      system:serviceaccount:kube-system:csi-secrets-store-provider-aws
    
  5. Delete AWS Roles and Policies

    aws iam detach-role-policy --role-name openshift-access-to-mysecret --policy-arn $POLICY_ARN
    aws iam delete-role --role-name openshift-access-to-mysecret
    aws iam delete-policy --policy-arn $POLICY_ARN