aca-allowed-container-registries.json

{
  "properties": {
    "displayName": "Azure Container Apps allowed container registries",
    "policyType": "Custom",
    "mode": "Indexed",
    "description": "This policy enables you to restrict the list of container registries for Azure Container Apps.",
    "metadata": {
      "version": "1.0.0",
      "category": "Azure Container Apps"
    },
    "parameters": {
      "listOfAllowedContainerRegistries": {
        "type": "Array",
        "metadata": {
          "displayName": "Allowed container registries",
          "description": "The list of container registries that can be specified when deploying resources."
        },
        "defaultValue": [
          "mcr.microsoft.com"
        ]
      },
      "effect": {
        "type": "String",
        "metadata": {
          "displayName": "Effect",
          "description": "Enable or disable the execution of the policy"
        },
        "allowedValues": [
          "Audit",
          "Deny",
          "Disabled"
        ],
        "defaultValue": "Audit"
      }
    },
    "policyRule": {
      "if": {
        "allOf": [{
            "field": "type",
            "equals": "Microsoft.App/containerApps"
          },
          {
            "count": {
              "field": "Microsoft.App/containerApps/template.containers[*]",
              "where": {
                "value": "[split(first(field('Microsoft.App/containerApps/template.containers[*].image')), '/')[0]]",
                "notIn": "[parameters('listOfAllowedContainerRegistries')]"
              }
            },
            "greater": 0
          }
        ]
      },
      "then": {
        "effect": "[parameters('effect')]"
      }
    }
  }
}