Azure Policy definitions deny effect

The deny effect is used to prevent a resource request that doesn't match defined standards through a policy definition and fails the request.

Deny evaluation

When creating or updating a matched resource in a Resource Manager mode, deny prevents the request before being sent to the Resource Provider. The request is returned as a 403 (Forbidden). In the portal, the Forbidden can be viewed as a deployment status that was prevented by the policy assignment. For a Resource Provider mode, the resource provider manages the evaluation of the resource.

During evaluation of existing resources, resources that match a deny policy definition are marked as non-compliant.

Deny properties

For a Resource Manager mode, the deny effect doesn't have any more properties for use in the then condition of the policy definition.

For a Resource Provider mode of Microsoft.Kubernetes.Data, the deny effect has the following subproperties of details. Use of templateInfo is required for new or updated policy definitions as constraintTemplate is deprecated.

• templateInfo (required)
  • Can't be used with constraintTemplate.
  • sourceType (required)

    • Defines the type of source for the constraint template. Allowed values: PublicURL or Base64Encoded.

    • If PublicURL, paired with property url to provide location of the constraint template. The location must be publicly accessible.

      Hoiatus

      Don't use SAS URIs or tokens in url or anything else that could expose a secret.

    • If Base64Encoded, paired with property content to provide the base 64 encoded constraint template. See Create policy definition from constraint template to create a custom definition from an existing Open Policy Agent (OPA) Gatekeeper v3 constraint template.

• constraint (optional)
  • Can't be used with templateInfo.
  • The CRD implementation of the Constraint template. Uses parameters passed via values as {{ .Values.<valuename> }}. In example 2 below, these values are {{ .Values.excludedNamespaces }} and {{ .Values.allowedContainerImagesRegex }}.
• constraintTemplate (deprecated)
  • Can't be used with templateInfo.
  • Must be replaced with templateInfo when creating or updating a policy definition.
  • The Constraint template CustomResourceDefinition (CRD) that defines new Constraints. The template defines the Rego logic, the Constraint schema, and the Constraint parameters that are passed via values from Azure Policy. For more information, go to Gatekeeper constraints.
• constraintInfo (optional)
  • Can't be used with constraint, constraintTemplate, apiGroups, or kinds.
  • If constraintInfo isn't provided, the constraint can be generated from templateInfo and policy.
  • sourceType (required)

    • Defines the type of source for the constraint. Allowed values: PublicURL or Base64Encoded.

    • If PublicURL, paired with property url to provide location of the constraint. The location must be publicly accessible.

      Hoiatus

      Don't use SAS URIs or tokens in url or anything else that could expose a secret.

• namespaces (optional)
  • An array of Kubernetes namespaces to limit policy evaluation to.
  • An empty or missing value causes policy evaluation to include all namespaces, except the ones defined in excludedNamespaces.
• excludedNamespaces (required)
  • An array of Kubernetes namespaces to exclude from policy evaluation.
• labelSelector (required)
  • An object that includes matchLabels (object) and matchExpression (array) properties to allow specifying which Kubernetes resources to include for policy evaluation that matched the provided labels and selectors.
  • An empty or missing value causes policy evaluation to include all labels and selectors, except namespaces defined in excludedNamespaces.
• apiGroups (required when using templateInfo)
  • An array that includes the API groups to match. An empty array ([""]) is the core API group.
  • Defining ["*"] for apiGroups is disallowed.
• kinds (required when using templateInfo)
  • An array that includes the kind of Kubernetes object to limit evaluation to.
  • Defining ["*"] for kinds is disallowed.
• values (optional)
  • Defines any parameters and values to pass to the Constraint. Each value must exist in the Constraint template CRD.

Deny example

Example 1: Using the deny effect for Resource Manager modes.

JSON

"then": {
  "effect": "deny"
}

Example 2: Using the deny effect for a Resource Provider mode of Microsoft.Kubernetes.Data. The additional information in details.templateInfo declares use of PublicURL and sets url to the location of the Constraint template to use in Kubernetes to limit the allowed container images.

JSON

"then": {
  "effect": "deny",
  "details": {
    "templateInfo": {
      "sourceType": "PublicURL",
      "url": "https://store.policy.core.windows.net/kubernetes/container-allowed-images/v1/template.yaml",
    },
    "values": {
      "imageRegex": "[parameters('allowedContainerImagesRegex')]"
    },
    "apiGroups": [
      ""
    ],
    "kinds": [
      "Pod"
    ]
  }
}

Next steps

• Review examples at Azure Policy samples.
• Review the Azure Policy definition structure.
• Understand how to programmatically create policies.
• Learn how to get compliance data.
• Learn how to remediate non-compliant resources.
• Review Azure management groups.