Azure AD SPN and UPN? - azure

I want to understand the difference between the SPN & UPN in Azure AD Context. My understanding is there are three way to establish identity in Azure AD
Users Key in their username and Password to establish Identity
An application using ClientId and Secret Key to establish Identity
An application using ClientId and Certificate to establish Identity
Is User/Password is called UPN & rest two are called SPN? Also is there any other way to establish identity?

In Azure AD, UPN is the User Principal Name. It is always in the format which looks like an email address. Essentially it has three parts. User account name, the separator (i.e. # symbol) and UPN suffix or domain name. Its primary purpose is to use during the authentication and represents user identity.
SPN is the Service Principal Name. The service principal object defines the policy and permissions for an application, providing the basis for a security principal to represent the application when accessing resources at run-time. App identity (service principal) is preferable to running the app under your own credentials (user identity) because:
You can assign permissions to the app identity that are different than your own permissions. Typically, these permissions are restricted to exactly what the app needs to do.
You do not have to change the app's credentials if your responsibilities change.
You can use a certificate to automate authentication when executing an unattended script.
You could create service principal with password or certificate as you shown.
Please click here for more about application and service principal objects in Azure Active Directory, and click here for how to use portal to create an Azure Active Directory application and service principal that can access resources. You could choose other ways (e.g. PowerShell/CLI) on the left navigation panel.

Related

How to securely give external application access to key vault in Azure

I have a vendor application, possibly a SAAS application that want to access my key Vault in my Azure tenant, which is behind a firewall. Can anyone the suggest the best way to give the vendor access to my key vault? please drop a comment if you have done this before.
There are 2 ways, from which you can give the External vendor application access to your Azure key vault.
You can create a new service principal/app registration in your Azure AD tenant which will model the vendor application and provide that service principal access to key vault secrets and certificates, Via adding that service principal to the access policy with RBAC role. And then giving your vendor the Application client ID, Application secret, Tenant ID to use this app in their SAAS vendor app code for authentication to Key vault in your tenant. If the SAAS Vendor application already resides in your tenant, This method will work too.
I created a key vault resource on Azure :-
I created one single Tenant App to use for this tenant and then added that app to the access policy of Azure key vault.
Select your key vault from Azure Portal> Left pane> Access Policies> Add> Select the secret, key and certificate permissions as required > In Principal select your Single Tenant App> Next> Create
Singletenantapp is added to access policies with below permissions on Key vault:-
Now, You can provide this singletenantkeyvault application’s > tenant Id, application client ID, secret to the SAAS vendor application code as this Singletenantkeyvault application will model your real world SAAS vendor application.
Example-
{
"DNSNameKeyVault": "https://siliconkeyvault123.vault.azure.net/",
"AADAppRegistrationAppId": "7dad56d0-29d7-4d14-8dbe-4b9787895942",
"AADAppRegistrationAppSecret": "<app-secret>",
"SomeSecret": "DEV_VALUE"
}
Similar settings should be added to your SAAS vendor’s application’s appsettings.json folder depending on the framework that the SAAS vendor’s app runs on.
Note- Access policies can only be added to the Users and Applications in your directory only, you cannot add access policies to the external application that resides in other tenant/directory. You can either create a new application in your tenant or enable Multi-tenant application.
You can create a multi-tenant app shared between your External SAAS vendor’s tenant and your tenant, And assign the Key vault access policy to that Multi-tenant App. In this way you can use the existing SAAS vendor app in their tenant with your tenant to only give least privileged access to control Key vault.
I created a multi-tenant asp.net core app in my Default Directory tenant: -
MultiTenantAuth App is created successfully in our Azure AD Default Directory tenant
You can also create a multi-tenant app within Azure AD portal like below:-
Now, either you can authenticate with your SAS vendor application with your tenant and access key vault via running the code from VS studio or you can call this endpoint and replace the SAS vendor’s tenant ID with yours to get the SAAS vendor application from their tenant to your tenant and then provide the required access:-
In this example- Your MultiTenantDemo or MultiTenantAuth app is your SAAS vendor’s tenant Application which will be added in your or other tenant by either running the code or by calling the below endpoint.
In this example- I created MultiTenantDemo, MultiTenantAuth applications in my Default Directory and now I am adding them in my other directory SiliconSid.
https://login.microsoftonline.com/tenantid/adminconsent?client_id=clientid&state=12345&redirect_uri=http://localhost/myapp/permissions
I logged in with my another tenant’s admin user and accepted the consent for the app from my default directory to the new directory
After I called this endpoint, the Application is added in my another directory SILICONSID:-
Now, I’ll add this application in the Access policy of my key vault :-
Is inviting the user from your SAAS vendor’s tenant to your tenant and giving the user access to your key vault access policy if your saas vendor real world application uses username and password as authentication and not Service principal.
You can invite your SAAS vendor’s user like below:-
Invite the user and only provide the user access to your key vault:-
You can invite the SAAS vendor user via Email
An invitation link will be sent to the user’s email once the user accepts the invitation, He is redirected to your Azure Portal and is added in your Azure AD.
The SAAS vendor user can log in to Azure Portal and select your directory> and access the Key vault given you added that user to your access policy like below:-
You can again apply the policy of least privileged here and provide user only the access to the key vault and nothing else. You also need to provide the invited user access to your Subscription’s Key vault resource group with key vault role to only read key vault. This can be used if your SAAS vendor real world application uses Username and password as authentication in their Code and not service principal application.
The best way here is to either create a new application in your tenant or to create a multi-tenant application. Point 3) is not recommended and is not a best security practice.
Reference:
Azure Key Vault considerations for multitenancy - Azure Architecture Center | Microsoft Learn

What Azure Service Principals really are?

From the page about Azure CLI Sign-in:
Service principals are accounts not tied to any particular user, which can have permissions on them assigned through pre-defined roles. Authenticating with a service principal is the best way to write secure scripts or programs, allowing you to apply both permissions restrictions and locally stored static credential information
It seems that a service principal is kind of a service account, a sort of identity which isn't tied to any specific person.
On the other hand, from here it seems that a service principal is an instantiation of the Application object in the domain of App registrations. This has something to do with registering an application so it can be authorized using OAuth 2.0 etc. etc.
So I can't understand the relation between these two concepts. Can someone help?
Service principal is sort of a service account.
It is the thing that permissions are assigned to.
For example, if you consent to an application reading your user profile on your behalf, that adds an OAuth 2 permission grant to the service principal.
Application permissions add an app role assignment to the service principal when granted.
When you make an app registration, a service principal is also created in that same Azure AD tenant.
Even though you add required permissions and consent to them through the app registration forms, the permissions are actually assigned to the service principal.
The app registration is only really a template.
Where this gets interesting is if you have a multi-tenant app (other Azure AD tenants' users can use your app).
In this case a service principal representing your app is also created in other Azure AD tenants when a user consents to the permissions your app requires.
Essentially you get an automatically generated service account in each tenant using your app.
This allows admins to decide which permissions to grant your app, which users can access the app etc.

How to use aad authentication or managed identity to access resources with torus system in azure?

We previously used keyvault and connectionstring to access resources in azure. However it will generate many parameters needed. We want to simplify the process.
We wanted to use aad authentication.
Firstly, we tried certificate-based aad authentication https://learn.microsoft.com/en-us/azure/cosmos-db/sql/certificate-based-authentication first, it works. But the thing is, in keyvault the certificates are set auto-rotation, but in aad app, we can only manually upload new certificate each time (I know there are methods like VM extension or extra software can do auto renewal, but it's complicated. We just want change configs in azure portal and change service code to access.) In this situation, when certificates becomes more and more, it's not suitable to manually renew each cert in each aad app. I notice in some places it says setting tls/ssl settings which makes auto-renewal, but currently in azure portal, it just can manually upload certificates. Only in function app can do tls/ssl settings.
Secondly, then we notice another one as managed identity. It simply says azureServiceTokenProvider.GetAccessTokenAsync("https://management.azure.com/"); to get token. But the thing is, current login tenantid is microsoft.onmicrosoft.com, but the resources and the subscriptions are all in prdtrs01.onmicrosoft.com through torus account.
Even I try with string accessToken = azureServiceTokenProvider.GetAccessTokenAsync("https://management.azure.com/", prdtrs01tenantid) still does not work, saying AADSTS50020: User account '{EmailHidden}' from identity provider '...' does not exist in tenant 'PRDTRS01' and cannot access the application '...'. It seems just cannot get token from prdtrs01 tenantid.
Also, I tried to replace the aad app used in first method with the function app used in second method to do certificate-based authentication. However the function app does not have a clientid, just principalId and user managed identity's clientid. Both ids fail with ClientAssertionCertificate credential = new ClientAssertionCertificate(clientId, cert); in certificate-based authentication. It finally says "Client assertion contains an invalid signature. [Reason - The key was not found., Thumbprint of key used by client".
In all, I described several ways we tried, but all failed. Can anyone help?
Thanks
AADSTS50020: User account '{EmailHidden}' from identity provider
'...' does not exist in tenant 'PRDTRS01' and cannot access the
application
As per this first error , it means that the account you are using to access the application is not a part of the tenant that the application is hosted on.
Make the application as a Multi-Tenant Application :
You can convert the application to accept users from multiple tenants. In this way you can give access to users who are not in your tenant without having to add them to the tenant where the application is in.
Maybe account type is set to Accounts in this organizational directory only.
You may have to change it to Accounts in any organizational directory.
Go to Azure portal -> Azure Active Directory -> Manage -> App Registrations --> your app name -> Supported Account Types
(or)
Add the user to the tenant as guest :
You may need to add the user to the tenant that the application is hosted in. You can follow this document to add the user with your domain as a Guest User to the tenant. And grant access to the application for the said user.
However, if your authentication call is for specific tenant i.e., https://login.microsoftonline.com/yourtenantname or_id, users from other organizations won't be able to access the application and are required to be added as guests in the tenant specified in the request.
In your case, try to authenticate request like https://login.microsoftonline.com/organizations or https://login.microsoftonline.com/common

What's the purpose of Azure Active Directory Application credentials although service princial also has credentials

Azure Active Directory has applications and service principals.
https://learn.microsoft.com/en-us/azure/active-directory/develop/app-objects-and-service-principals
Both objects seem to have credentials.
New-AzureADApplicationPasswordCredential
New-AzureADServicePrincipalPasswordCredential
If both a service principal and an application object have credential(for example password), which one is used for authentication? If service principal's credential is used, what's the purpose of application object's credential? Is it for fallback when a service princial doesn't have credential?
I read this question, but I cannot understand the difference between application's password and service principal's one.
Authentication difference between using AAD app key and Service Principal Password
Both of the two passwords can be used to authenticate, but the password of the service principal just can be used to authenticate in the tenant which it located in, the password of the application can be used to authenticate in all the tenants where its service principal instances located.
The service principal is just a instance of the application in a specific tenant, when a tenant consent an application, azure will install it as an Enterprise Application(i.e. serivice principal) in the tenant. There can be several service principals in different tenants, but the application is the only.

Authentication difference between using AAD app key and Service Principal Password

To run applications in Azure, I need to create an Application in Azure AD and a corresponding Service Principal. Then my application authenticates against this App/Principal pair. To authenticate, I can create an application key in the App registration, or I can create a password in the Service Principal (among other options). What's the difference from a practial standpoint?
For example, this code runs exactly the same (from the outside) whether the $key is the App's key or the Service Principal's password:
$key = ConvertTo-SecureString $authKeyOrPassword -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential($appID, $key)
Add-AzureRmAccount -Credential $cred -TenantId $tenantID -ServicePrincipal
When should I authenticate against the App, and when should I use the Service Principal?
First, let me explain why it has both Applications and service principals in Azure AD. Here is the explanation from Mordent Authentication with Azure AD for Web App by Vittorio Bertocci.
Azure AD defines a new entity, the Application, which is meant to
describe an application as an abstract entity: a template, if you
will. As a developer, you work with Applications. At deployment time a
given Application object can be used as a blueprint to create a
ServicePrincipal representing a concrete instance of an application in
a directory. It’s that ServicePrincipal that is used to define what
the app can actually do in that specific target directory, who can use
it, what resources it has access to, and so on.
Bear with me just a
little longer, the abstract part is almost over. The main way through
which Azure AD creates a ServicePrincipal from an Application is
consent. Here’s a simplified description of the flow: Say that you
create an Application object in directory A, supplying all the
protocol coordinates we’ve discussed so far in earlier chapters. Say
that a user from tenant B navigates to the app’s pages and triggers
an authentication flow. Azure AD authenticates the user from B against
its home directory, B. In so doing, it sees that there is no
ServicePrincipal for the app in B; hence, it prompts the user about
whether he or she wants to consent for that app to have access to the
directory B (you’ll see later in what capacity). If the user grants
consent, Azure AD uses the Application object in A as a blueprint for
creating a ServicePrincipal in B. Along with that, B records that the current user consented to the use of this application (expect lots of details on this later on). Once that’s done, the user receives a token for accessing the app.
If you want to know the difference between Azure AD App key and service principle Password, you'd better know the relationship of Application and service principal. I will copy&paste here some extracts from this page of the documentation
When you register an Azure AD application in the Azure portal, two objects are created in your Azure AD tenant: an application object, and a service principal object.
Consider the application object as the global representation of your application for use across all tenants, and the service principal as the local representation for use in a specific tenant. The application object serves as the template from which common and default properties are derived for use in creating corresponding service principal objects.
An application object therefore has a 1:1 relationship with the software application, and a 1:many relationships with its corresponding service principal object(s).A service principal must be created in each tenant where the application is used, enabling it to establish an identity for sign-in and/or access to resources being secured by the tenant.
Example diagram
Summary
Now, we can know the difference between Azure AD App key and service principle password. They belong to different objects. The password to be associated with the service principal. This is just for the application tenant to login azure. However, you can provide the App key value with the application ID to log in as the application with all tenants.
To see more details about Application and service principal objects in Azure Active Directory , you can refer to this document.

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