azure-vmss-public-ip-disabled: Azure VMSS Public IP Not Assigned

id: azure-vmss-public-ip-disabled
info:
  name: Azure VMSS Public IP Not Assigned
  author: princechaddha
  severity: high
  description: |
    Ensure that instances running within your Microsoft Azure virtual machine scale set (VMSS) are not configured with public IP addresses. Assigning public IP addresses to individual VMSS instances increases attack surface, making it harder to manage and secure the environment.
  impact: |
    Instances with public IP addresses are more exposed to potential external attacks, increasing the security risks for the Azure environment.
  remediation: |
    Configure your VMSS to disable public IP address assignments to its instances. Ensure that all networking is handled through internal networking resources.
  reference:
    - https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-networking
  tags: cloud,devops,azure,microsoft,vmss,azure-cloud-config

flow: |
  code(1);
  for (let InstanceData of iterate(template.vmssList)) {
    InstanceData = JSON.parse(InstanceData);
    set("name", InstanceData.name);
    set("resourceGroup", InstanceData.resourceGroup);
    code(2);
  }

self-contained: true
code:
  - engine:
      - sh
      - bash
    source: |
      az vmss list --output json --query '[*].{"name":name,"resourceGroup":resourceGroup}'

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

  - engine:
      - sh
      - bash
    source: |
      az vmss list-instance-public-ips --name "$name" --resource-group "$resourceGroup" --query '[*].ipAddress'

    matchers-condition: and
    matchers:
      - type: word
        words:
          - '[]'

    extractors:
      - type: dsl
        dsl:
          - 'name + " in " + resourceGroup + " has no public IP addresses assigned."'
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