Nick's .NET Travels

Continually looking for the yellow brick road so I can catch me a wizard....

Authentication Redirection Loop with Angular Application and Azure Active Directory

Recently we ran in to some difficulty with an Angular application that was being retrofitted into a different environment. During the initial development the Angular application had been pushed to Azure for testing. However, the final resting place for the application was on a on-premises sever. Whilst the switch was relatively painless, with the only major change being to a persistent file storage instead of blob storage, we also had to shift from our development Azure AD tenant (the Angular application, and the associated services, uses Azure AD to authenticate and authorize users), to the client’s Azure AD tenant. This shift required creating two new application registrations within the client’s Azure AD tenant.

Unfortunately after creating the new registrations, and updating the Angular application (and the corresponding services), any attempt to log in with valid credentials resulted in a continual loop between the Angular application and the Azure AD login prompt. In this case we were only using Azure AD to authenticate users and other than controlling access to the application services there weren’t any other permissions that users would have to agree to.

In the past I’ve posted about how administrators have to grant permission to users within their tenant to access an application (see https://nicksnettravels.builttoroam.com/post/2017/01/24/Admin-Consent-for-Permissions-in-Azure-Active-Directory.aspx). Usually there is an Azure AD login error when users attempt to sign in. In this case, for some reason we either missed the error message or it was being obscured by the automatic redirection between the Angular application and the Azure AD login prompt.

We did end up finding the solution, thanks to the Azure AD team at Microsoft, who quickly identified the error in our Fiddler trace. The critical request/response was:

Request

GET https://login.microsoftonline.com/<tenantid>/oauth2/authorize?response_type=token&client_id=<clientid>&resource=<resourceid>&redirect_uri=<uri>&prompt=none&login_hint=admin

Response

HTTP/1.1 302 Found
Location: <uri>
<html><head><title>Object moved</title></head><body>
<h2>Object moved to <a href="<uri>/#error=interaction_required&amp;error_description=AADSTS65001%3a+The+user+or+administrator+has+not+consented+to+use+the+application+with+ID+%27.+Send+an+interactive+authorization+request+for+this+user+and+resource

The important part is that the error indicates that either the user or administrator has not consented to use of the application, and that there should be an interactive authorization request. This is a little cryptic but going back to my previous post we can simply add “prompt=admin_consent” to the login request – assuming an administrator logs in, they can then grant access to the application to all users in the tenant.

There is actually a much easier way for single tenant applications, which this is. Instead of waiting for an administrator to log in, permission can be granted via the Azure portal:

- Select the Directory where the application is registered (drop down in top right cornert of the Azure portal where the signed in user is listed)

- Select Azure Active Directory from the sidebar menu

- Select App Registrations

- Select the application registration you want to grant access to

- From All settings, click on the Required Permissions link

- Click “Grant Permissions”

image

This will give all users access to the application. If you have multiple registrations (eg one for the web site and one for the corresponding services), don’t forget to grant permission to both registrations.

Again, big thanks to the team at Microsoft for pointing us to the solution

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