AWS Secrets Manager and Config Provider for Secret Store CSI Driver

AWS offers two services to manage secrets and parameters conveniently in your code. AWS Secrets Manager allows you to easily rotate, manage, and retrieve database credentials, API keys, certificates, and other secrets throughout their lifecycle. AWS Systems Manager Parameter Store provides hierarchical storage for configuration data. The AWS provider for the Secrets Store CSI Driver allows you to make secrets stored in Secrets Manager and parameters stored in Parameter Store appear as files mounted in Kubernetes pods.

Installation

Requirements

Amazon Elastic Kubernetes Service (EKS) 1.17+

Secrets Store CSI driver installed:

helm repo add secrets-store-csi-driver https://kubernetes-sigs.github.io/secrets-store-csi-driver/charts
helm install -n kube-system csi-secrets-store secrets-store-csi-driver/secrets-store-csi-driver

Note that older versions of the driver may require the --set grpcSupportedProviders="aws" flag on the install step.

IAM Roles for Service Accounts (IRSA) as described in the usage section below.

Installing the AWS Provider

To install the Secrets Manger and Config Provider use the YAML file in the deployment directory:

kubectl apply -f https://raw.githubusercontent.com/aws/secrets-store-csi-driver-provider-aws/main/deployment/aws-provider-installer.yaml

Usage

Set the region name and name of your cluster to use in the bash commands that follow:

REGION=<REGION>
CLUSTERNAME=<CLUSTERNAME>

Where <REGION> is the region in which your Kubernetes cluster is running and <CLUSTERNAME> is the name of your cluster.

Now create a test secret:

aws --region "$REGION" secretsmanager  create-secret --name MySecret --secret-string '{"username":"memeuser", "password":"hunter2"}'

Create an access policy for the pod scoped down to just the secrets it should have and save the policy ARN in a shell variable:

POLICY_ARN=$(aws --region "$REGION" --query Policy.Arn --output text iam create-policy --policy-name nginx-deployment-policy --policy-document '{
    "Version": "2012-10-17",
    "Statement": [ {
        "Effect": "Allow",
        "Action": ["secretsmanager:GetSecretValue", "secretsmanager:DescribeSecret"],
        "Resource": ["arn:*:secretsmanager:*:*:secret:MySecret-??????"]
    } ]
}')

Note, when using SSM parameters the permission "ssm:GetParameters" is needed in the policy. To simplify this example we use wild card matches above but you could lock this down further using the full ARN from the output of create-secret above.

Create the IAM OIDC provider for the cluster if you have not already done so:

eksctl utils associate-iam-oidc-provider --region="$REGION" --cluster="$CLUSTERNAME" --approve # Only run this once

Next create the service account to be used by the pod and associate the above IAM policy with that service account. For this example we use nginx-deployment-sa for the service account name:

eksctl create iamserviceaccount --name nginx-deployment-sa --region="$REGION" --cluster "$CLUSTERNAME" --attach-policy-arn "$POLICY_ARN" --approve --override-existing-serviceaccounts

Now create the SecretProviderClass which tells the AWS provider which secrets are to be mounted in the pod. The ExampleSecretProviderClass.yaml in the examples directory will mount "MySecret" created above:

kubectl apply -f https://raw.githubusercontent.com/aws/secrets-store-csi-driver-provider-aws/main/examples/ExampleSecretProviderClass.yaml

Finally we can deploy our pod. The ExampleDeployment.yaml in the examples directory contains a sample nginx deployment that mounts the secrets under /mnt/secrets-store in the pod:

kubectl apply -f https://raw.githubusercontent.com/aws/secrets-store-csi-driver-provider-aws/main/examples/ExampleDeployment.yaml

To verify the secret has been mounted properly, See the example below:

kubectl exec -it $(kubectl get pods | awk '/nginx-deployment/{print $1}' | head -1) cat /mnt/secrets-store/MySecret; echo

Troubleshooting

Most errors can be viewed by describing the pod deployment. For the deployment, find the pod names using get pods (use -n <NAMESPACE> if you are not using the default namespace):

kubectl get pods

Then describe the pod (substitute the pod ID from above for <PODID>, as before use -n if you are not using the default namespace):

kubectl describe pod/<PODID>

Additional information may be available in the provider logs:

kubectl -n kube-system get pods
kubectl -n kube-system logs pod/<PODID>

Where <PODID> in this case is the id of the csi-secrets-store-provider-aws pod.

SecretProviderClass options

The SecretProviderClass has the following format:

apiVersion: secrets-store.csi.x-k8s.io/v1alpha1
kind: SecretProviderClass
metadata:
  name: <NAME>
spec:
  provider: aws
  parameters:

The parameters section contains the details of the mount request and contain one of the three fields:

objects: This is a string containing a YAML declaration (described below) of the secrets to be mounted. This is most easily written using a YAML multi-line string or pipe character. For example:
```
  parameters:
    objects: |
        - objectName: "MySecret"
          objectType: "secretsmanager"
```
region: An optional field to specify the AWS region to use when retrieving secrets from Secrets Manager or Parameter Store. If this field is missing, the provider will lookup the region from the annotation on the node. This lookup adds overhead to mount requests so clusters using large numbers of pods will benefit from providing the region here.
pathTranslation: An optional field to specify a substitution character to use when the path separator character (slash on Linux) is used in the file name. If a Secret or parameter name contains the path separator failures will occur when the provider tries to create a mounted file using the name. When not specified the underscore character is used, thus My/Path/Secret will be mounted as My_Path_Secret. This pathTranslation value can either be the string "False" or a single character string. When set to "False", no character substitution is performed.

The objects field of the SecretProviderClass can contain the following sub-fields:

objectName: This field is required. It specifies the name of the secret or parameter to be fetched. For Secrets Manager this is the SecretId parameter and can be either the friendly name or or full ARN of the secret. For SSM Parameter Store, this must be the Name of the parameter and can not be a full ARN.
objectType: This field is optional when using a Secrets Manager ARN for objectName, otherwise it is required. This field can be either "secretsmanager" or "ssmparameter".
objectAlias: This optional field specifies the file name under which the secret will be mounted. When not specified the file name defaults to objectName.
objectVersion: This field is optional, and generally not recommended since updates to the secret require updating this field. For Secrets Manager this is the VersionId. For SSM Parameter Store, this is the optional version number.
objectVersionLabel: This optional fields specifies the alias used for the version. Most applications should not use this field since the most recent version of the secret is used by default. For Secrets Manager this is the VersionStage. For SSM Parameter Store this is the optional Parameter Label.
jmesPath: This optional field specifies the specific key-value pairs to extract from a JSON-formatted secret. You can use this field to mount key-value pairs from a properly formatted secret value as individual secrets. For example: Consider a secret "MySecret" with JSON content as follows:
```
    {
        "username": "testuser"
        "password": "testpassword"
    }
```
To mount the username and password key pairs of this secret as individual secrets, use the jmesPath field as follows:
```
      objects: |
          - objectName: "MySecret"
            objectType: "secretsmanager"
            jmesPath:
                - path: "username"
                  objectAlias: "MySecretUsername"
                - path: "password"
                  objectAlias: "MySecretPassword"
```
If you use the jmesPath field, you must provide the following two sub-fields:
- path: This required field is the JMES path to use for retrieval
- objectAlias: This required field specifies the file name under which the key-value pair secret will be mounted.

Additional Considerations

Rotation

When using the optional alpha rotation reconciler feature of the Secrets Store CSI driver the driver will periodically remount the secrets in the SecretProviderClass. This will cause additional API calls which results in additional charges. Applications should use a reasonable poll interval that works with their rotation strategy. A one hour poll interval is recommended as a default to reduce excessive API costs.

Anyone wishing to test out the rotation reconciler feature can enable it using helm:

helm upgrade -n kube-system csi-secrets-store secrets-store-csi-driver/secrets-store-csi-driver --set enableSecretRotation=true --set rotationPollInterval=3600s

Private Builds

You can pull down this git repository and build and install this plugin into your account's AWS ECR registry using the following steps. First clone the repository:

git clone https://github.com/aws/secrets-store-csi-driver-provider-aws
cd secrets-store-csi-driver-provider-aws

Next, set your region and repository name in bash shell variables to be used later:

export REGION=<REGION>
export PRIVREPO=<ACCOUNT>.dkr.ecr.$REGION.amazonaws.com/secrets-store-csi-driver-provider-aws

Where <REGION> is the AWS region in which your Kubernetes cluster is running, and <ACCOUNT> is your AWS account Id. Next create your ECR repository if you have not already done so:

aws --region $REGION ecr create-repository --repository-name secrets-store-csi-driver-provider-aws # Only do this once

Now run make to build the plugin and push it into your account's repo:

make

Once the image is in your repo you can install it into your cluster from your repo rather than the public repo:

envsubst < deployment/private-installer.yaml | kubectl apply -f -

Security Considerations

The AWS Secrets Manger and Config Provider provides compatibility for legacy applications that access secrets as mounted files in the pod. Security conscious appliations should use the native AWS APIs to fetch secrets and optionally cache them in memory rather than storing them in the file system.

Security

See CONTRIBUTING for more information.

License

This project is licensed under the Apache-2.0 License.

sturman/secrets-store-csi-driver-provider-aws