README.md

blazor-identity-api

Sign in users using AspNetCore.Identity (.NET 8 RC2) in a Blazor Server app using cookie authentication and call a protected API using API Key authentication.

Run both of the projects, login using Username: ashish@example.com and Password: Password123!. Navigate to Weather page and you can see the weather data being fetched from a secured API:

Helpful links

1. Choosing an Identity Solution: Identity vs OIDC (Read it!)
2. Blazor OIDC with Aspire Example
3. ASP.NET Core Identity system is designed to authenticate a single web application

How I created the projects

BlazorServerClient project

1. Installed ef tool dotnet tool update --global dotnet-ef --prerelease

2. I used Rider to create the project:

   Hit Create

3. I ran the migrations dotnet ef database update

4. Added some missing middleware not included in the template

   

5. Launched the app, created a new user and signed right in.

ProtectedWebAPI project

1. I used Rider to create the project

   

2. Added API Key authentication to it. Take a look at the code to see how I implemented it. I referenced mostly this and this.

Issues in the BlazorServerClient project

1. The Logout doesn't work:

   Click Logout on the bottom left.

   

   You'll get this error and the user will be never logged out.

2. Lot of errors show up. Could be a bug in Rider. (The app runs fine though).

   

Call ProtectedWebAPI from BlazorServerClient

In the client project, I setup the ProtectedWebAPI Url and ApiKey in appsettings.json and used that info in Program.cs to call the API.

appsettings.json:

Program.cs

WeatherForecastService.cs:

Add Microsoft Authentication to your app. Reference.

Create an app in Microsoft Developer Portal (Azure)

Store your config

Store the secret in user-secrets. Store ClientId in appsettings.json.

Add Nuget package

Setup Program.cs

Take OAuth authentication for a test drive

1. Click "Microsoft"

   

2. Give consent

   

3. These are the claims, MSFT sends to the app

   

How the claims showed up in the UI

The services are setup at the last line of MicrosoftAccountExtensions where there's a call to .AddOAuth. Here you can see the MicrosoftAccountHandler.

To see how the above claims were fetched, you can see it in the MicrosoftAccountOptions class added from the package. Here you can see that it had asked for the scope of user.read and Claims were mapped this way:

How Microsoft Authentication is setup under the covers

Command + Click on .AddMicrosoftAccount method:

Check what AuthenticationScheme was used:

By going to MicrosoftAccountDefaults:

You can see AuthenticationScheme used was "Microsoft" and also see the 3 most important endpoints in OAuth: AuthorizationEndpoint, TokenEndpoint and UserInformationEndpoint.

Add GitHub authentication to your app. Reference.

Register an app in Github

Grab clientid and clientsecret.

Go to GitHub's OAuth docs to find 3 important endpoints as part of OAuth: Authorize, Token and User endpoints.Reference.

1. Authorize

   

   After the user is logged in, GitHub sends us the one time code (that can be used to exchange for a token) to the redirect url that we set during registration.

   https://localhost:7074/signin-github

2. Token

   

3. User Information endpoint to get user info

   

Store your config

Setup Program.cs

Just look at the code.

AuthN and AuthZ Basics Reference.

Big picture

app.UseRouting(): URL is matched to the endpoint.

app.UseEndpoints(): Actual endpoints are registered.

Cookie

This is what cookie contains

You can retrieve those Items from AuthenticateResult.AuthenticationProperties.Items:

External Authentication

It is handled by RemoteAuthenticationHandler.

Propietary provider support:

Google, Facebook, Twitter, Microsoft Account etc

Standard Protocol support:

OpenID connect, WS-Federation, SAML etc.

Taking a look at Authentication middleware

Every time you navigate to ANY page in the app, the Authentication middleware runs (It's middleware duh!).

It's the bit that's inside app.UseAuthentication:

Handlers:

See how IAuthenticationHandler looks like:

See how IAuthenticationRequestHandler looks like (this is relevant in var handler = await handlers.GetHandlerAsync(context, scheme.Name) as IAuthenticationRequestHandler; line shown below):

I have setup Microsoft and Github (OAuth) authentication, so I've got 2 handlers now:

Those 2 handlers come from the service registration section:

The middleware determines if it should handle auth request on those handlers (using IAuthenticationRequestHandler.HandleRequestAsync).

For eg: For my case (Microsoft, GitHub handlers), it's determined by HandleRequestAsync() in RemoteAuthenticationHandler.cs:

Since, I'm going to "/counter" page now, the HandleRequestAsync method short circuits.

DefaultAuthentication:

Default AuthenticationScheme is whatever I setup in .AddAuthentication:

Using the default authentication scheme, it tries to authenticate the current request. If it succeeds, you get .User in the HttpContext.

To view the handler for your default auth scheme, navigate from here:

To here:

To here:

To here:

To finally here:

Here you can see that this service has Schemes, Handlers etc. to authenticate a request.

Now let's get back to see how this line in AuthenticationMiddleware.cs executes:

It just calls .AuthenticateAsync on the AuthenticationService:

Let's see this in action:

See the SchemeName and Handler:

Now we get into AuthenticateService's AuthenticateAsync method:

Then into AuthenticationHandler's AuthenticateAsync method:

Then into AuthenticationHandler's HandleAuthenticateOnceAsync method:

Then into AuthenticationHandler's HandleAuthenticateAsync method:

It's an abstract method that is implemented in a class that derives it, CookieAuthenticationHandler in this case, so we end up here:

Then we finally get this result:

Taking a look at GitHub Authentication in detail

The schemes the app has:

ExternalLoginPicker.razor shows the external logins:

Click "OAuth" button.

This will call the POST endpoint:

/Account/PerformExternalLogin in Identity/Extensions/IdentityComponentsEndpointRouteBuilderExtensions.cs

This is where I want GitHub to redirect me after completing authentication:

Use properties to preserve data between Challenge phase and Callback phase

Challenge (scheme)

Now we're in OAuthHandler.cs

Redirect to external provider

https://localhost:7074/Account/PerformExternalLogin redirects us to GitHub's authorization endpoint:

So the app goes to that location:

At this ppint the user authenicates with GitHub (NOT this app) and the user authorizes this app to fetch user info from GitHub by accepting the consent screen.

Callback

User gets redirected with the one time code to the callback url:

AuthN middleware asks handlers who wants to process request

OAuthHandler says "I will" because ShouldHandleRequestAsync() returns true as seen in RemoteAuthenticationHandler.cs:

Handler does the protocol post-processing

When line 87 shown above runs, we end up in OAuthHandler.cs:

The query has code and state.

The state has redirect url and login provider we set earlier:

The code is exchanged for the token here:

Dummy identity is created:

Towards the end of this method, a ticket is created:

By calling this callback:

Now we're back in RemoteAuthenticationHandler.cs.

Inside HandleRequestAsync(), we set which scheme produced this identity:

Call sign-in handler (Set "External" cookie)

In RemoteAuthenticationHandler.cs

The Principal looks like this:

And the properties:

Now we're in CookieAuthenticationHandler.cs's HandleSignInAsync method:

A new ticket is created:

The method completes:

This method also completes:

Now we're back in RemoteAuthenticationHandler.cs's HandleRequestAsync() method and about to get redirected to our original ReturnUri:

Now we're redirected with the "External" cookie

Run app-level post processing

Now we're in /Account/ExternalLogin (In ExternalLogin.razor)

We try to authenticate using "External" cookie to get external user info:

The method looks like this:

Now we have userinfo:

ProviderKey is the Id in Github.

Now we go into OnLoginCallbackAsync():

Here:

Now we get into SignInManager.cs:

Looks like there's this neat method to get user by loginProvider (for eg: github) and providerKey (for eg: 30603497).

Note 1:

Whenever AuthenticateAsync() method in AuthenticationService.cs runs AND AuthenticateResult.Succeeded is true, ClaimsTransformation is run.

Here:

Note 2:

The action in the query is this:

Also notice the user is not authenticated at this point because we haven't successfully authenticated with the default authentication scheme (Identity.Application).

If for some reason, we're not able to get externalLoginInfo, an error message is passed through the cookie in the redirect to be shown in the UI.

Like here:

The message comes from this component in the Login.razor page:

Signout "External" cookie and Signin "Application" (primary) cookie

We're still inside SignInManager.cs.

Here we Signout external cookie:

And Signin primary cookie:

By calling this method:

Looks like it adds provider name (github) as an additional claim.

Then call this method to sign in on primary cookie:

Now we're back in ExternalLogin.razor by logging in the user successfully.

Redirect to final url

We get to homepage now.

Like this:

Now we hit AuthenticationMiddleware and try to authenticate the user. The Identity.External cookie is removed and Identity.Application cookie is present at this point.

Success!