terraform.azure.security.azure-instance-extensions.azure-instance-extensions

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Ensure Virtual Machine Extensions are not Installed

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Defintion

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rules:
  - id: azure-instance-extensions
    message: Ensure Virtual Machine Extensions are not Installed
    patterns:
      - pattern: resource
      - pattern-either:
          - pattern-inside: |
              resource "azurerm_linux_virtual_machine" "..." {
              ...
              }
          - pattern-inside: |
              resource "azurerm_windows_virtual_machine" "..." {
              ...
              }
      - pattern-not-inside: |
          resource "azurerm_linux_virtual_machine" "..." {
          ...
          allow_extension_operations = false
          ...
          }
      - pattern-not-inside: |
          resource "azurerm_windows_virtual_machine" "..." {
          ...
          allow_extension_operations = false
          ...
          }
    metadata:
      owasp:
        - A05:2017 - Broken Access Control
        - A01:2021 - Broken Access Control
      cwe:
        - "CWE-284: Improper Access Control"
      category: security
      technology:
        - terraform
        - azure
      references:
        - https://owasp.org/Top10/A01_2021-Broken_Access_Control
      subcategory:
        - audit
      likelihood: LOW
      impact: LOW
      confidence: LOW
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      vulnerability_class:
        - Improper Authorization
    languages:
      - hcl
    severity: WARNING

Examples

azure-instance-extensions.tf

# pass
resource "azurerm_linux_virtual_machine" "disabled" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "linux-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  allow_extension_operations = false
}

# pass
resource "azurerm_windows_virtual_machine" "disabled" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "win-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  allow_extension_operations = false
}

# fail
# ruleid: azure-instance-extensions
resource "azurerm_linux_virtual_machine" "default" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "linux-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }
}

# fail
# ruleid: azure-instance-extensions
resource "azurerm_linux_virtual_machine" "enabled" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "linux-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  allow_extension_operations = true
}

# fail
# ruleid: azure-instance-extensions
resource "azurerm_windows_virtual_machine" "default" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "win-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }
}

# fail
# ruleid: azure-instance-extensions
resource "azurerm_windows_virtual_machine" "enabled" {
  admin_password      = "admin"
  admin_username      = "admin123"
  location            = "azurerm_resource_group.test.location"
  name                = "win-vm"
  resource_group_name = "azurerm_resource_group.test.name"
  size                = "Standard_F2"

  network_interface_ids = [
    "azurerm_network_interface.test.id"
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  allow_extension_operations = true
}