azure-nsg-restricted-port-range: Restricted Port Range in Azure NSGs

id: azure-nsg-restricted-port-range
info:
  name: Restricted Port Range in Azure NSGs
  author: princechaddha
  severity: medium
  description: |
    Ensure that Azure network security groups (NSGs) do not have ranges of ports configured to allow inbound traffic, which can expose associated virtual machines to Denial-of-Service (DoS) or brute-force attacks. Only specific ports required by your application should be open following cloud security best practices.
  impact: |
    Having a range of ports open can increase the vulnerability to DoS and brute-force attacks, compromising the security of your Azure virtual machine instances.
  remediation: |
    Modify the NSG rules to only allow inbound traffic on necessary ports specific to your application requirements. This practice minimizes potential attack vectors.
  reference:
    - https://docs.microsoft.com/en-us/azure/virtual-network/network-security-groups-overview
  tags: cloud,devops,azure,microsoft,nsg,azure-cloud-config

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

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

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

  - engine:
      - sh
      - bash
    source: |
      az network nsg rule list --nsg-name $nsg --resource-group $resourcegroup --query "[?direction=='Inbound' && access=='Allow'].{PortRange:destinationPortRanges, Rule: name, Priority: priority}"

    matchers:
      - type: word
        words:
          - "0-65535"
          - "80-8080"
          - "111-32800"

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

      - type: dsl
        dsl:
          - 'nsg + " allows a range of ports " + destinationPortRange + " which may be vulnerable to attacks"'
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