## AWS Authentication

### Controller's Pod Identity

![Pod Identity Authentication](./pictures/diagrams-provider-aws-auth-pod-identity.png)

This is basicially a zero-configuration authentication method that inherits the credentials from the runtime environment using the [aws sdk default credential chain](https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/credentials.html#credentials-default).

You can attach a role to the pod using [IRSA](https://docs.aws.amazon.com/eks/latest/userguide/iam-roles-for-service-accounts.html), [kiam](https://github.com/uswitch/kiam) or [kube2iam](https://github.com/jtblin/kube2iam). When no other authentication method is configured in the `Kind=Secretstore` this role is used to make all API calls against AWS Secrets Manager or SSM Parameter Store.

Based on the Pod's identity you can do a `sts:assumeRole` before fetching the secrets to limit access to certain keys in your provider. This is optional.

```yaml
apiVersion: external-secrets.io/v1alpha1
kind: SecretStore
metadata:
  name: team-b-store
spec:
  provider:
    aws:
      service: SecretsManager
      region: eu-central-1
      # optional: do a sts:assumeRole before fetching secrets
      role: team-b
```

### Access Key ID & Secret Access Key
![SecretRef](./pictures/diagrams-provider-aws-auth-secret-ref.png)

You can store Access Key ID & Secret Access Key in a `Kind=Secret` and reference it from a SecretStore.

```yaml
apiVersion: external-secrets.io/v1alpha1
kind: SecretStore
metadata:
  name: team-b-store
spec:
  provider:
    aws:
      service: SecretsManager
      region: eu-central-1
      # optional: assume role before fetching secrets
      role: team-b
      auth:
        secretRef:
          accessKeyIDSecretRef:
            name: awssm-secret
            key: access-key
          secretAccessKeySecretRef:
            name: awssm-secret
            key: secret-access-key
```

### EKS Service Account credentials

![Service Account](./pictures/diagrams-provider-aws-auth-service-account.png)

This feature lets you use short-lived service account tokens to authenticate with AWS.
You must have [Service Account Volume Projection](https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/#service-account-token-volume-projection) enabled - it is by default on EKS. See [EKS guide](https://docs.aws.amazon.com/eks/latest/userguide/iam-roles-for-service-accounts-technical-overview.html) on how to set up IAM roles for service accounts.

The big advantage of this approach is that ESO runs without any credentials.

```yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  annotations:
    eks.amazonaws.com/role-arn: arn:aws:iam::123456789012:role/team-a
  name: my-serviceaccount
  namespace: default
```

Reference the service account from above in the Secret Store:
```yaml
apiVersion: external-secrets.io/v1alpha1
kind: SecretStore
metadata:
  name: secretstore-sample
spec:
  provider:
    aws:
      service: SecretsManager
      region: eu-central-1
      auth:
        jwt:
          serviceAccountRef:
            name: my-serviceaccount
```
