nat-gateway-use: Managed NAT Gateway Usage

id: nat-gateway-use
info:
  name: Managed NAT Gateway Usage
  author: princechaddha
  severity: medium
  description: |
    Ensure the use of Amazon Managed NAT Gateway for better availability and bandwidth in VPC networks instead of self-managed NAT instances.
  impact: |
    Using self-managed NAT instances can lead to single points of failure and potential bandwidth bottlenecks.
  remediation: |
    Replace NAT instances with Amazon Managed NAT Gateway to ensure high availability and scalability in your VPC network.
  reference:
    - https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-gateway.html
  metadata:
    max-request: 2
  tags: cloud,devops,aws,amazon,vpc,aws-cloud-config
variables:
  region: "us-east-1"

flow: |
  code(1)
  for(let VPCIds of iterate(template.vpcid)){
    set("vpc", VPCIds)
    code(2)
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      aws ec2 describe-vpcs --region $region --query 'Vpcs[*].VpcId' --output json

    extractors:
      - type: json
        name: vpcid
        internal: true
        json:
          - '.[]'

  - engine:
      - sh
      - bash
    source: |
         aws ec2 describe-nat-gateways --region $region --filter "Name=vpc-id,Values=$vpc" "Name=state,Values=available" --query 'NatGateways'

    matchers:
      - type: word
        words:
          - "[]"

    extractors:
      - type: dsl
        dsl:
          - 'vpc + " VPC is not using Managed NAT Gateways"'
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