Modify-UDR.json

{
    "name": "Modify-UDR",
    "type": "Microsoft.Authorization/policyDefinitions",
    "apiVersion": "2021-06-01",
    "scope": null,
    "properties": {
        "policyType": "Custom",
        "mode": "All",
        "displayName": "Enforce specific configuration of User-Defined Routes (UDR)",
        "description": "This policy enforces the configuration of User-Defined Routes (UDR) within a subnet.",
        "metadata": {
            "version": "1.0.0",
            "category": "Network",
            "source": "https://github.com/Azure/Enterprise-Scale/",
            "alzCloudEnvironments": [
                "AzureCloud",
                "AzureChinaCloud",
                "AzureUSGovernment"
            ]
        },
        "parameters": {
            "effect": {
                "type": "String",
                "allowedValues": [
                    "Modify",
                    "Disabled"
                ],
                "defaultValue": "Modify",
                "metadata": {
                    "displayName": "Effect",
                    "description": "Enable or disable the execution of the policy"
                }
            },
            "addressPrefix": {
                "type": "string",
                "metadata": {
                    "description": "The destination IP address range in CIDR notation that this Policy checks for within the UDR. Example: 0.0.0.0/0 to check for the presence of a default route.",
                    "displayName": "Address Prefix"
                }
            },
            "nextHopType": {
                "type": "string",
                "metadata": {
                    "description": "The next hope type that the policy checks for within the inspected route. The value can be Virtual Network, Virtual Network Gateway, Internet, Virtual Appliance, or None.",
                    "displayName": "Next Hop Type"
                },
                "allowedValues": [
                    "VnetLocal",
                    "VirtualNetworkGateway",
                    "Internet",
                    "VirtualAppliance",
                    "None"
                ]
            },
            "nextHopIpAddress": {
                "type": "string",
                "metadata": {
                    "description": "The IP address packets should be forwarded to.",
                    "displayName": "Next Hop IP Address"
                }
            }
        },
        "policyRule": {
            "if": {
                "allOf": [
                    {
                        "field": "type",
                        "equals": "Microsoft.Network/routeTables"
                    },
                    {
                        "count": {
                            "field": "Microsoft.Network/routeTables/routes[*]"
                        },
                        "equals": 0
                    }
                ]
            },
            "then": {
                "effect": "[[parameters('effect')]",
                "details": {
                    "roleDefinitionIds": [
                        "/providers/microsoft.authorization/roleDefinitions/4d97b98b-1d4f-4787-a291-c67834d212e7"
                    ],
                    "conflictEffect": "audit",
                    "operations": [
                        {
                            "operation": "add",
                            "field": "Microsoft.Network/routeTables/routes[*]",
                            "value": {
                                "name": "default",
                                "properties": {
                                    "addressPrefix": "[[parameters('addressPrefix')]",
                                    "nextHopType": "[[parameters('nextHopType')]",
                                    "nextHopIpAddress": "[[parameters('nextHopIpAddress')]"
                                }
                            }
                        }
                    ]
                }
            }
        }
    }
}