terraform.azure.best-practice.azure-networkinterface-enable-ip-forwarding.azure-networkinterface-enable-ip-forwarding

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Ensure that Network Interfaces disable IP forwarding

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Defintion

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rules:
  - id: azure-networkinterface-enable-ip-forwarding
    message: Ensure that Network Interfaces disable IP forwarding
    patterns:
      - pattern: resource
      - pattern-inside: |
          resource "azurerm_network_interface" "..." {
          ...
          enable_ip_forwarding = true
          ...
          }
    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-networkinterface-enable-ip-forwarding.tf

# fail
# ruleid: azure-networkinterface-enable-ip-forwarding
resource "azurerm_network_interface" "example" {
    name                = "example-nic"
    location            = azurerm_resource_group.example.location
    resource_group_name = azurerm_resource_group.example.name

    ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.example.id
    private_ip_address_allocation = "Dynamic"
    }        
    enable_ip_forwarding = true
}

# pass
resource "azurerm_network_interface" "example" {
    name                = "example-nic"
    location            = azurerm_resource_group.example.location
    resource_group_name = azurerm_resource_group.example.name

    ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.example.id
    private_ip_address_allocation = "Dynamic"
    }
    enable_ip_forwarding = false
}

# pass
resource "azurerm_network_interface" "example" {
    name                = "example-nic"
    location            = azurerm_resource_group.example.location
    resource_group_name = azurerm_resource_group.example.name

    ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.example.id
    private_ip_address_allocation = "Dynamic"
    }
}