azure-vmss-zone-redundancy-missing: Azure VMSS Zone-Redundant Configuration Not Enabled

id: azure-vmss-zone-redundancy-missing
info:
  name: Azure VMSS Zone-Redundant Configuration Not Enabled
  author: princechaddha
  severity: high
  description: |
    Ensure that all your Microsoft Azure virtual machine scale sets are using zone-redundant availability configurations instead of single-zone (zonal) configurations, to deploy and load balance virtual machines (VMs) across multiple Availability Zones (AZs) in order to protect the scale sets from datacenter-level failures.
  impact: |
    Using single-zone configurations can lead to potential datacenter-level outages affecting your services' availability and reliability.
  remediation: |
    Configure your VMSS to use zone-redundant availability configurations to ensure high availability and fault tolerance across multiple data centers.
  reference:
    - https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-design-overview
  tags: cloud,devops,azure,microsoft,vmss,azure-cloud-config

flow: |
  code(1);
  for (let ScaleSetData of iterate(template.scaleSetList)) {
    ScaleSetData = JSON.parse(ScaleSetData);
    set("name", ScaleSetData.name);
    set("resourceGroup", ScaleSetData.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: scaleSetList
        internal: true
        json:
          - '.[]'

  - engine:
      - sh
      - bash
    source: |
      az vmss show --name "$name" --resource-group "$resourceGroup" --query 'zones' --output json

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

      - type: word
        negative: true
        words:
          - "1"

    extractors:
      - type: dsl
        dsl:
          - 'name + " in " + resourceGroup + " is not using a zone-redundant configuration"'
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