This question is essentially a duplicate of Adding IAM Group to aws-auth configmap in AWS EKS. However, the question does not have an accepted answer and I would like to provide more context.

I know that aws-auth ConfigMap object does not allow mapping AWS Group directly. A workaround would be to map an AWS Role instead. I tried that but were unable to get it working. Mapping an AWS User works without issues.

I setup an AWS Role arn:aws:iam::027755483893:role/development-readwrite with account 027755483893 as being the trusted entity and attached the following trust policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::027755483893:root"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

I setup an AWS Group arn:aws:iam::027755483893:group/development-readwrite and attached the following policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "sts:AssumeRole"
            ],
            "Resource": [
                "arn:aws:iam::027755483893:role/development-readwrite"
            ]
        }
    ]
}

I setup the aws-auth ConfigMap as follows:

apiVersion: v1
data:
  mapRoles: |
    # Other mappings omitted for clarity
    - groups:
      - system:masters
      rolearn: arn:aws:iam::027755483893:role/development-readwrite
  mapUsers: |
    []
kind: ConfigMap
metadata:
  creationTimestamp: "2019-08-21T08:25:15Z"
  name: aws-auth
  namespace: kube-system
  resourceVersion: "62031092"
  selfLink: /api/v1/namespaces/kube-system/configmaps/aws-auth
  uid: 33b33620-c3ed-11e9-83c0-029bc9dcca16

However, none of the users in the group have access to the cluster. Do the users need to explicitly assume role? Is there anything else I'm missing?