User-Consent screen not showing when using Postman and .Net 6 Web Api

Zesa Rex 0
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So I am writing a .NET 6 Core Web Api using Azure AD as authentication for the API.

Now when using Graph API as example, you need to setup Graph API scopes in the App Registration. Lets use a delegated "user.read" permission for this example.

I use Postman to receive the access token for the application by authenticating as an user against Azure AD for the API. I would expect to receive a consent-screen so I can consent to the usage of "user.read". This does not happen though.. I get logged in and receive a valid access token. In the Backend though, it will throw an error because the user / admin did not consent to the application.

How do I get around this? Why don't I get asked to consent the permissions set up in the app registration? Neither in Postman, nor in a Swagger oAuth Flow..

My current workaround for this is to use a React application and sign in over the frontend application. Using the frontend application, I get asked to consent to the permissions. After consenting, I can use postman without getting the "user didn't consent" - error.

Any ideas? What did I miss?

azure-ad-graph-api oauth-2.0 azure-active-directory asp.net-core azure
1 Answers

Let's focus on the user-consent page first. When we created an azure ad app then add api permission for it, then use this azure ad app to make your .net 6 app/react app integrate azure ad to use azure authentication, and we go to the microsoft sign in page and successfully sign in, we will see a dialog which indicating that this app require you to consent a list of permissions. The permissions are correspond to the api permissions you set for the aad app. After consent once, then it won't ask you to consent again when sign in next time.

enter image description here

This consent only happened when users are signed in. Let's go back to the flows used to generate access token in Azure AD. Since you used delegate permission, then you may used the recommend Auth code flow(Another flow called ROPC flow can also generate delegate access token but not recommended). When we used auth code flow, we need to sign in first, the login url should look like this:

https://login.microsoftonline.com/tenant.onmicrosoft.com/oauth2/v2.0/authorize?client_id=azure_ad_app_id
&response_type=code
&redirect_uri=http://localhost/myapp/
&response_mode=query
&scope=user.read
&state=12345

We need to use it to get the auth code, then we can use the code to generate access token, per my test, I created a new azure ad app and when I directly hit this url in the browser and sign in, it still required me to give the consent. So I'm afraid the reason why you didn't see the dialog when test in post man is that you've consent it when test in react app, or you don't use auth code flow.

Tiny Wang0
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