Split-Tenancy

Overview

SCEPman can be configured to be operated from an Azure tenant different to the Azure/Intune tenant to whose users and/or devices it issues certificates to. This approach is called split-tenancy and is especially helpful for MSPs that would like to consolidate Azure infrastructure costs across their customers while maintaining a dedicated backend and unique CA for each of those customers.

Split-tenancy comes along with a major disadvantage: Managed Identities can no longer be used. This means authentication against the Graph API (Azure AD and Intune) is again handled using an App registration and Client secret, which has to be managed (by the MSP) as it expires.

In the following, we refer to the hosting tenant as home tenant and to the customer tenant as target tenant.

Configuration Steps

To configure SCEPman and Certificate Master for split-tenancy, please follow these steps:

1. Perform a standard deployment of SCEPman/Certificate Master as described in our Getting Started Guide.

2. Create an App registration in the target tenant as described here: Azure App Registration. This App registration will allow SCEPman to access the Azure AD and Intune directories in the target tenant.

The client secret generated as part of this App registration has an expiry and must be renewed before it expires. Please set a reminder for the renewal.

SCEPman

3. Navigate to the SCEPman App service and then to "Settings" --> "Configuration". Locate the following parameters and delete them:

• AppConfig:AuthConfig:ManagedIdentityEnabledForWebsiteHostname

• AppConfig:AuthConfig:ManagedIdentityEnabledOnUnixTime

• AppConfig:AuthConfig:ManagedIdentityPermissionLevel

4. Rename the following settings (do not change their values):

• AppConfig:AuthConfig:ApplicationId --> AppConfig:AuthConfig:HomeApplicationId

• AppConfig:AuthConfig:TenantId --> AppConfig:AuthConfig:HomeTenantId

5. Create the following new application settings:

Name	Value
AppConfig:AuthConfig:ApplicationId	GUID of the App registration that was created before.
AppConfig:AuthConfig:TenantId	Tenant ID of the target tenant.
AppConfig:AuthConfig:ApplicationKey	Value of the Client secret that was created as part of the App registration before.

6. Restart the SCEPman App service.

Certificate Master

7. Navigate to the Certificate Master App service and then to "Settings" --> "Configuration".

8. Now you have two options:

   1. You want users from your home tenant to log in to Certificate Master and issue certificates, which includes guest users in your home tenant, e.g. from your target tenant. If that is the case, rename the following settings (do not change their values):

      • AppConfig:AuthConfig:TenantId --> AppConfig:AuthConfig:HomeTenantId

      • AppConfig:AuthConfig:ApplicationId --> AppConfig:AuthConfig:HomeApplicationId

   2. You want users from your target tenant to log in to Certificate Master and issue certificates, which includes guest users in your target tenant, e.g. from your home tenant. If that is what you wish, do the following:

      • Open a PowerShell or Azure Cloud Shell in your target tenant and run the following commands: Install-Module SCEPman -Scope CurrentUser -Force Register-SCEPmanCertMaster -CertMasterBaseURL <url> \ Use the URL like 'https://certmaster.scepman.contoso.de/' for <url>.

      • The CMDlet will output an Application Id and a Tenant Id (that of the target tenant). Enter these two values as AppConfig:AuthConfig:HomeApplicationId and AppConfig:AuthConfig:HomeTenantId in your Certificate Master settings.

      • Now create the following new application settings, possibly overriding the existing ones, with the same values as in SCEPman:

Name	Value
AppConfig:AuthConfig:ApplicationId	GUID of the App registration that was created before.
AppConfig:AuthConfig:TenantId	Tenant ID of the target tenant.
AppConfig:AuthConfig:ApplicationKey	Value of the Client secret that was created as part of the App registration before. You can create a separate new Client secret for Certificate Master if you want.

9. Restart the SCEPman Certificate Master App service.

As an overview, here are the accounts used by Certificate Master and what they are used for:

Account	What is it used for?	Condition
Managed Identity	Authorize CSRs submitted to SCEPman Access to the Storage Account	No alternatives
App Registration with App ID from ApplicationId	Certificate Master accesses Microsoft Graph in this context to see which certificates have been enrolled via Intune	If ApplicationKey is not present, the Managed Identity is used instead.
App Registration with App ID from HomeApplicationId	Users authenticate to this application. It should be in the tenant where users accessing Certificate Master reside (but guest users from other tenants can also be authorized)	If HomeApplicationId is not present, ApplicationId is used instead.