IAM Roles for Service Accounts IRSA Lab

Provision an OpenID Connect (OIDC) identity provider, map an AWS IAM Role to a Kubernetes Service Account, and verify access using a test Pod.

Prerequisites

• An active Amazon EKS cluster.

• kubectl, eksctl, and aws CLI tools configured and authenticated.

---

Step 1: Associate an OIDC Provider

EKS clusters have an OIDC issuer URL. You must associate an IAM OIDC provider with this cluster so IAM can validate the tokens generated by Kubernetes.

Bash

# Replace  and  with your cluster details
export CLUSTER_NAME="eks-cluster"
export AWS_REGION="us-east-1"

eksctl utils associate-iam-oidc-provider \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION \
    --approve

``

# Replace  and  with your cluster details
export CLUSTER_NAME="eks-cluster"
export AWS_REGION="us-east-1"

eksctl utils associate-iam-oidc-provider \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION \
    --approve

Step 2: Create an AWS IAM Policy

Create a policy that defines the exact AWS permissions the Pod requires. In this lab, we will grant read-only access to Amazon S3.

Bash

cat < s3-readonly-policy.json
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": &#91;
                "s3:ListAllMyBuckets",
                "s3:GetBucketLocation"
            &#93;,
            "Resource": "*"
        }
    ]
}
EOF

# Create the policy and capture the ARN
POLICY_ARN=$(aws iam create-policy \
    --policy-name EKSS3ReadOnlyPolicy \
    --policy-document file://s3-readonly-policy.json \
    --query 'Policy.Arn' \
    --output text)

echo $POLICY_ARN

``

cat < s3-readonly-policy.json
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": &#91;
                "s3:ListAllMyBuckets",
                "s3:GetBucketLocation"
            &#93;,
            "Resource": "*"
        }
    ]
}
EOF

# Create the policy and capture the ARN
POLICY_ARN=$(aws iam create-policy \
    --policy-name EKSS3ReadOnlyPolicy \
    --policy-document file://s3-readonly-policy.json \
    --query &#39;Policy.Arn&#39; \
    --output text)

echo $POLICY_ARN

Step 3: Create the IAM Role and Kubernetes Service Account

This step creates an IAM role, attaches the policy from Step 2, and creates a Kubernetes Service Account annotated with the IAM Role ARN. It establishes the trust relationship.

Bash

eksctl create iamserviceaccount \
    --name s3-reader-sa \
    --namespace default \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION \
    --attach-policy-arn $POLICY_ARN \
    --approve \
    --override-existing-serviceaccounts

``

eksctl create iamserviceaccount \
    --name s3-reader-sa \
    --namespace default \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION \
    --attach-policy-arn $POLICY_ARN \
    --approve \
    --override-existing-serviceaccounts

Step 4: Deploy a Test Pod

Deploy an AWS CLI Pod configured to use the newly created Service Account (s3-reader-sa).

Bash

cat < test-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: aws-cli-tester
  namespace: default
spec:
  serviceAccountName: s3-reader-sa
  containers:
  - name: aws-cli
    image: amazon/aws-cli:latest
    command: &#91;"sleep", "3600"&#93;
  restartPolicy: Never
EOF

kubectl apply -f test-pod.yaml

``

cat < test-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: aws-cli-tester
  namespace: default
spec:
  serviceAccountName: s3-reader-sa
  containers:
  - name: aws-cli
    image: amazon/aws-cli:latest
    command: &#91;"sleep", "3600"&#93;
  restartPolicy: Never
EOF

kubectl apply -f test-pod.yaml

Wait for the Pod to be in the Running state:

Bash

kubectl get pods aws-cli-tester -w

``

kubectl get pods aws-cli-tester -w

Step 5: Verify IRSA Configuration

Exec into the Pod and verify that the AWS CLI is automatically picking up the injected web identity token.

1: Check the environment variables: Kubernetes automatically injects AWS_ROLE_ARN and AWS_WEB_IDENTITY_TOKEN_FILE when the Service Account is annotated.

Bash

kubectl exec -it aws-cli-tester -- env | grep AWS

``

kubectl exec -it aws-cli-tester -- env | grep AWS

2: Verify Identity: Check which IAM role the Pod is assuming.

Bash

kubectl exec -it aws-cli-tester -- aws sts get-caller-identity

``

kubectl exec -it aws-cli-tester -- aws sts get-caller-identity

Expected Output: The Arn should reflect the IAM role created in Step 3, not the worker node's IAM role.

3: Test S3 Access:

Bash

kubectl exec -it aws-cli-tester -- aws s3 ls

``

kubectl exec -it aws-cli-tester -- aws s3 ls

Expected Output: A list of S3 buckets in your account.

4: Test Unauthorized Access (Validation): Attempt to create an S3 bucket to ensure the least privilege policy is enforced.

Bash

kubectl exec -it aws-cli-tester -- aws s3 mb s3://my-irsa-test-bucket-12345

``

kubectl exec -it aws-cli-tester -- aws s3 mb s3://my-irsa-test-bucket-12345

Expected Output: AccessDenied error.

Step 6: Teardown

Remove the resources to avoid any ongoing configuration drift or clutter.

Bash

kubectl delete -f test-pod.yaml

eksctl delete iamserviceaccount \
    --name s3-reader-sa \
    --namespace default \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION

aws iam delete-policy --policy-arn $POLICY_ARN
rm s3-readonly-policy.json test-pod.yaml

``

kubectl delete -f test-pod.yaml

eksctl delete iamserviceaccount \
    --name s3-reader-sa \
    --namespace default \
    --cluster $CLUSTER_NAME \
    --region $AWS_REGION

aws iam delete-policy --policy-arn $POLICY_ARN
rm s3-readonly-policy.json test-pod.yaml