Azure Authentication in Prowler

Prowler for Azure supports multiple authentication types. Authentication methods vary between Prowler App and Prowler CLI:

Prowler App:

• Service Principal Application

Prowler CLI:

• Service Principal Application (Recommended)
• AZ CLI credentials
• Interactive browser authentication
• Managed Identity Authentication

Required Permissions

Prowler for Azure requires two types of permission scopes:

Microsoft Entra ID Permissions

These permissions allow Prowler to retrieve metadata from the assumed identity and perform specific Entra checks. While not mandatory for execution, they enhance functionality.

Assigning Required API Permissions

Assign the following Microsoft Graph permissions:

• Directory.Read.All
• Policy.Read.All
• UserAuthenticationMethod.Read.All (optional, for multifactor authentication (MFA) checks)

Replace Directory.Read.All with Domain.Read.All for more restrictive permissions. Note that Entra checks related to DirectoryRoles and GetUsers will not run with this permission.

Azure Portal

1. Go to your App Registration > “API permissions”

   

2. Click ”+ Add a permission” > “Microsoft Graph” > “Application permissions”

   

3. Search and select:

   • Directory.Read.All
   • Policy.Read.All
   • UserAuthenticationMethod.Read.All
   

4. Click “Add permissions”, then grant admin consent

   

Azure CLI

1. To grant permissions to a Service Principal, execute the following command in a terminal:

   az ad app permission add --id {appId} --api 00000003-0000-0000-c000-000000000000 --api-permissions 7ab1d382-f21e-4acd-a863-ba3e13f7da61=Role 246dd0d5-5bd0-4def-940b-0421030a5b68=Role 38d9df27-64da-44fd-b7c5-a6fbac20248f=Role
   

Subscription Scope Permissions

These permissions are required to perform security checks against Azure resources. The following RBAC roles must be assigned per subscription to the entity used by Prowler:

• Reader – Grants read-only access to Azure resources.
• ProwlerRole – A custom role with minimal permissions needed for some specific checks, defined in the prowler-azure-custom-role.

Assigning “Reader” Role at the Subscription Level

By default, Prowler scans all accessible subscriptions. If you need to audit specific subscriptions, you must assign the necessary role Reader for each one. For streamlined and less repetitive role assignments in multi-subscription environments, refer to the following section.

Azure Portal

1. To grant Prowler access to scan a specific Azure subscription, follow these steps in Azure Portal: Navigate to the subscription you want to audit with Prowler.

2. In the left menu, select “Access control (IAM)”.

3. Click ”+ Add” and select “Add role assignment”.

4. In the search bar, enter Reader, select it and click “Next”.

5. In the “Members” tab, click ”+ Select members”, then add the accounts to assign this role.

6. Click “Review + assign” to finalize and apply the role assignment.

   

Azure CLI

1. Open a terminal and execute the following command to assign the Reader role to the identity that is going to be assumed by Prowler:

   az role assignment create --role "Reader" --assignee <user, group, or service principal> --scope /subscriptions/<subscription-id>
   

Assigning “ProwlerRole” Permissions at the Subscription Level

Some read-only permissions required for specific security checks are not included in the built-in Reader role. To support these checks, Prowler utilizes a custom role, defined in prowler-azure-custom-role. Once created, this role can be assigned following the same process as the Reader role.

The checks requiring this ProwlerRole can be found in this section.

Azure Portal

1. Download the Prowler Azure Custom Role

   

2. Modify assignableScopes to match your Subscription ID (e.g. /subscriptions/xxxx-xxxx-xxxx-xxxx)

3. Go to your Azure Subscription > “Access control (IAM)”

   

4. Click ”+ Add” > “Add custom role”, choose “Start from JSON” and upload the modified file

   

5. Click “Review + Create” to finish

   

6. Return to “Access control (IAM)” > ”+ Add” > “Add role assignment”

   • Assign the Reader role to the Application created in the previous step
   • Then repeat the same process assigning the custom ProwlerRole
   

The assignableScopes field in the JSON custom role file must be updated to reflect the correct subscription or management group. Use one of the following formats: /subscriptions/<subscription-id> or /providers/Microsoft.Management/managementGroups/<management-group-id>.

Azure CLI

1. To create a new custom role, open a terminal and execute the following command:

az role definition create --role-definition '{                                                                                                                   640ms  lun 16 dic 17:04:17 2024
                    "Name": "ProwlerRole",
                    "IsCustom": true,
                    "Description": "Role used for checks that require read-only access to Azure resources and are not covered by the Reader role.",
                    "AssignableScopes": [
                    "/subscriptions/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX" // USE YOUR SUBSCRIPTION ID
                    ],
                    "Actions": [
                    "Microsoft.Web/sites/host/listkeys/action",
                    "Microsoft.Web/sites/config/list/Action"
                    ]
                }'

2. If the command is executed successfully, the output is going to be similar to the following:

   {
       "assignableScopes": [
           "/subscriptions/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
       ],
       "createdBy": null,
       "createdOn": "YYYY-MM-DDTHH:MM:SS.SSSSSS+00:00",
       "description": "Role used for checks that require read-only access to Azure resources and are not covered by the Reader role.",
       "id": "/subscriptions/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX/providers/Microsoft.Authorization/roleDefinitions/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX",
       "name": "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX",
       "permissions": [
           {
               "actions": [
                   "Microsoft.Web/sites/host/listkeys/action",
                   "Microsoft.Web/sites/config/list/Action"
               ],
               "condition": null,
               "conditionVersion": null,
               "dataActions": [],
               "notActions": [],
               "notDataActions": []
           }
       ],
       "roleName": "ProwlerRole",
       "roleType": "CustomRole",
       "type": "Microsoft.Authorization/roleDefinitions",
       "updatedBy": "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX",
       "updatedOn": "YYYY-MM-DDTHH:MM:SS.SSSSSS+00:00"
   }
   

Additional Resources

For more detailed guidance on subscription management and permissions:

• Azure subscription permissions
• Create Prowler Service Principal

Some permissions in ProwlerRole involve write access. If a ReadOnly lock is attached to certain resources, you may encounter errors, and findings for those checks will not be available.

Checks Requiring ProwlerRole

The following security checks require the ProwlerRole permissions for execution. Ensure the role is assigned to the identity assumed by Prowler before running these checks:

• app_function_access_keys_configured
• app_function_ftps_deployment_disabled

---

Service Principal Application Authentication (Recommended)

This method is required for Prowler App and recommended for Prowler CLI.

Creating the Service Principal

For more information, see Creating Prowler Service Principal.

Environment Variables (CLI)

For Prowler CLI, set up the following environment variables:

export AZURE_CLIENT_ID="XXXXXXXXX"
export AZURE_TENANT_ID="XXXXXXXXX"
export AZURE_CLIENT_SECRET="XXXXXXX"

Execution with the --sp-env-auth flag fails if these variables are not set or exported.

AZ CLI Authentication

Available only for Prowler CLI

Use stored Azure CLI credentials:

prowler azure --az-cli-auth

Managed Identity Authentication

Available only for Prowler CLI

Authenticate via Azure Managed Identity when running Prowler on Azure resources (VMs, Container Instances, Azure Functions, etc.):

prowler azure --managed-identity-auth

Prerequisites

Before using Managed Identity authentication, the following steps are required:

1. Enable Managed Identity on the Azure resource (e.g., VM, Container Instance)
2. Assign the required permissions to the Managed Identity on the target subscription(s) to scan

A common misconception is that enabling a Managed Identity on a resource automatically grants it permissions. This is not the case. Without explicit role assignments, Prowler will be unable to scan subscriptions and will return authorization errors, resulting in incomplete security assessments. The Managed Identity itself is a service principal that must be explicitly granted Reader and ProwlerRole permissions on each subscription to scan.

Step-by-Step Setup Guide

Step 1: Enable Managed Identity on the Azure Resource

Azure VM

Via Azure Portal:

1. Navigate to the VM in Azure Portal
2. Select “Identity” from the left menu under “Security”
3. Under “System assigned” tab, set Status to “On”
4. Click “Save”
5. Note the “Object (principal) ID” - this value is required for permission assignment

Via Azure CLI:

# Enable system-assigned managed identity
az vm identity assign --name <vm-name> --resource-group <resource-group>

# Get the principal ID
az vm identity show --name <vm-name> --resource-group <resource-group> --query principalId -o tsv

Azure Container Instance

Via Azure CLI:

# Enable system-assigned managed identity
az container create \
  --resource-group <resource-group> \
  --name <container-name> \
  --image <image> \
  --assign-identity

# Get the principal ID
az container show --resource-group <resource-group> --name <container-name> --query identity.principalId -o tsv

Step 2: Assign Reader Role to the Managed Identity

The Managed Identity needs the Reader role on each subscription to scan. This role must be assigned to the Managed Identity’s principal ID, not the VM or resource itself.

Azure Portal

1. Navigate to the target subscription to scan (not the VM’s resource group)
2. Select “Access control (IAM)” from the left menu
3. Click ”+ Add” > “Add role assignment”
4. Select “Reader” role, click “Next”
5. Click ”+ Select members”
6. Search for the VM name or paste the Managed Identity’s Object/Principal ID
7. Select it and click “Select”
8. Click “Review + assign”

When scanning a subscription different from where the VM is located, ensure the role is assigned on the target subscription, not the VM’s subscription.

Azure CLI

# Get the principal ID of the resource's managed identity
PRINCIPAL_ID=$(az vm identity show --name <vm-name> --resource-group <resource-group> --query principalId -o tsv)

# Assign Reader role on the target subscription
az role assignment create \
  --role "Reader" \
  --assignee-object-id $PRINCIPAL_ID \
  --assignee-principal-type ServicePrincipal \
  --scope /subscriptions/<target-subscription-id>

Step 3: Create and Assign ProwlerRole to the Managed Identity

The ProwlerRole is a custom role required for specific security checks. First, create the role if it does not exist, then assign it to the Managed Identity.

Azure CLI

Create the ProwlerRole:

az role definition create --role-definition '{
  "Name": "ProwlerRole",
  "IsCustom": true,
  "Description": "Role used for checks that require read-only access to Azure resources and are not covered by the Reader role.",
  "AssignableScopes": ["/subscriptions/<target-subscription-id>"],
  "Actions": [
    "Microsoft.Web/sites/host/listkeys/action",
    "Microsoft.Web/sites/config/list/Action"
  ]
}'

Assign ProwlerRole to the Managed Identity:

# Get the principal ID if not already available
PRINCIPAL_ID=$(az vm identity show --name <vm-name> --resource-group <resource-group> --query principalId -o tsv)

# Assign ProwlerRole on the target subscription
az role assignment create \
  --role "ProwlerRole" \
  --assignee-object-id $PRINCIPAL_ID \
  --assignee-principal-type ServicePrincipal \
  --scope /subscriptions/<target-subscription-id>

Azure Portal

Follow the same process as creating the ProwlerRole in the Assigning ProwlerRole Permissions section, then assign it to the Managed Identity using the same steps as the Reader role assignment.

Step 4: (Optional) Assign Microsoft Graph Permissions

For Entra ID (Azure AD) checks, the Managed Identity needs Microsoft Graph API permissions: Directory.Read.All, Policy.Read.All, and optionally UserAuthenticationMethod.Read.All.

Assigning Microsoft Graph API permissions to a Managed Identity requires Azure CLI or PowerShell - it cannot be done through the Azure Portal’s standard role assignment interface.

# Get the Managed Identity's principal ID
PRINCIPAL_ID=$(az vm identity show --name <vm-name> --resource-group <resource-group> --query principalId -o tsv)

# Get Microsoft Graph's service principal ID
GRAPH_SP_ID=$(az ad sp list --display-name "Microsoft Graph" --query [0].id -o tsv)

# Assign Directory.Read.All permission (App Role ID: 7ab1d382-f21e-4acd-a863-ba3e13f7da61)
az rest --method POST \
  --uri "https://graph.microsoft.com/v1.0/servicePrincipals/$PRINCIPAL_ID/appRoleAssignments" \
  --headers "Content-Type=application/json" \
  --body "{\"principalId\": \"$PRINCIPAL_ID\", \"resourceId\": \"$GRAPH_SP_ID\", \"appRoleId\": \"7ab1d382-f21e-4acd-a863-ba3e13f7da61\"}"

# Assign Policy.Read.All permission (App Role ID: 246dd0d5-5bd0-4def-940b-0421030a5b68)
az rest --method POST \
  --uri "https://graph.microsoft.com/v1.0/servicePrincipals/$PRINCIPAL_ID/appRoleAssignments" \
  --headers "Content-Type=application/json" \
  --body "{\"principalId\": \"$PRINCIPAL_ID\", \"resourceId\": \"$GRAPH_SP_ID\", \"appRoleId\": \"246dd0d5-5bd0-4def-940b-0421030a5b68\"}"

Step 5: Run Prowler

SSH or connect to the Azure resource and run Prowler:

# Scan all accessible subscriptions
prowler azure --managed-identity-auth

# Scan specific subscription(s)
prowler azure --managed-identity-auth --subscription-ids <subscription-id>

Wait a few minutes after assigning roles for Azure to propagate permissions. Role assignments are not always immediately effective.

Troubleshooting

Error: “No subscriptions were found, please check your permission assignments”

Cause: The Managed Identity does not have the Reader role assigned on any subscription.

Solution:

• Verify the Managed Identity has the Reader role assigned on at least one subscription.
• Wait a few minutes after role assignment for Azure to propagate permissions.
• Verify role assignments:
  az role assignment list --assignee <principal-id> --all
  

Error: “does not have authorization to perform action ‘Microsoft.Resources/subscriptions/read’”

Cause: The Managed Identity lacks the Reader role on the target subscription.

Solution:

• Ensure the Reader role is assigned to the Managed Identity’s principal ID, not the VM resource.
• Verify the role is assigned on the target subscription to scan, not just the VM’s resource group.
• Check role assignments:
  az role assignment list --assignee <principal-id> --scope /subscriptions/<subscription-id>
  

Error: “CredentialUnavailableError: ManagedIdentityCredential authentication unavailable”

Cause: Managed Identity is not enabled on the resource, or Prowler is running outside of Azure.

Solution:

• Verify Managed Identity is enabled on the Azure resource.
• Ensure Prowler is running from within the Azure resource (not a local machine).
• Check Managed Identity status:
  az vm identity show --name <vm-name> --resource-group <resource-group>
  

Error: Access token validation failure for Entra ID checks

Cause: The Managed Identity lacks Microsoft Graph API permissions.

Solution:

• Assign the required Graph API permissions as shown in Step 4.
• These permissions are optional for basic resource scanning but required for Entra ID security checks.

Browser Authentication

Available only for Prowler CLI

Authenticate using the default browser:

prowler azure --browser-auth --tenant-id <tenant-id>

Note: The tenant-id parameter is mandatory for browser authentication.