azure-functionapp-public-exposure: Exposed Azure Functions

id: azure-functionapp-public-exposure
info:
  name: Exposed Azure Functions
  author: princechaddha
  severity: high
  description: |
    To follow Azure cloud security best practices and prevent public exposure, ensure that the functions managed with Microsoft Azure Function App are not publicly accessible. An Azure function is considered publicly accessible when it is configured to allow inbound access through the default (public) endpoint.
  impact: |
    Allowing public network access to Azure Functions can expose sensitive business logic and data to potential security risks.
  remediation: |
    Configure Azure Functions to restrict access from the public network by setting the 'publicNetworkAccess' to 'Disabled'.
  reference:
    - https://docs.microsoft.com/en-us/azure/azure-functions/functions-networking-options
  tags: cloud,devops,azure,microsoft,functionapp,azure-cloud-config

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

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

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

  - engine:
      - sh
      - bash
    source: |
      az functionapp show --name $name --resource-group $resourceGroup --query 'publicNetworkAccess' --output json

    matchers:
      - type: word
        words:
          - "Enabled"

    extractors:
      - type: dsl
        dsl:
          - 'name + " is publicly accessible and should restrict network access"'
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