Amazon EMR clusters' security groups are open to the world

Description

Least privilege, it's is best practice to limit any database access only to those groups or instances that require it.

Fix - Buildtime

Terraform

Resource: aws_emr_cluster and aws_security_group
Argument: ingress of aws_security_group

resource "aws_emr_cluster" "cluster_ok" {
  name          = "emr-test-arn"
  release_label = "emr-4.6.0"
  applications  = ["Spark"]

  ec2_attributes {
    emr_managed_master_security_group = aws_security_group.block_access_ok.id
    emr_managed_slave_security_group  = aws_security_group.block_access_ok.id
    instance_profile                  = "connected_to_aws_iam_instance_profile"
  }
}

resource "aws_security_group" "block_access_ok" {
  name        = "block_access"
  description = "Block all traffic"

  ingress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["10.0.0.0/16"]
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["10.0.0.0/16"]
  }
}