OAuth Authorization Service in ASP.NET Core

In Web API 2, you used to be able to create an endpoint to issue a token by setting up an OAuth Authorization Server via middleware like below:

//Set up our auth server options.
var OAuthServerOptions = new OAuthAuthorizationServerOptions()
            {
                AllowInsecureHttp = true,
                TokenEndpointPath = new PathString("/token"),
                AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
                Provider = new SimpleAuthorizationServerProvider()
            };
 
 // Sets up the token issue endpoint using the options above
 app.UseOAuthAuthorizationServer(OAuthServerOptions);

Perhaps I'm missing it, but I'm trying to figure out how to do this in ASP.NET Core. I've looked through the source (https://github.com/aspnet/Security) but I don't really see anything analogous. Is there a new way to accomplish this? Do I need to just create a controller and do it myself?

I see how OAuth Authentication can be set up via Middleware, but this regards the authorization portion where I issue claims from my API.

EDIT (01/28/2021): AspNet.Security.OpenIdConnect.Server has been merged into OpenIddict as part of the 3.0 update. To get started with OpenIddict, visit documentation.openiddict.com.

---

Don't waste your time looking for an OAuthAuthorizationServerMiddleware alternative in ASP.NET Core, the ASP.NET team simply decided not to port it: https://github.com/aspnet/Security/issues/83

I suggest having a look to AspNet.Security.OpenIdConnect.Server, an advanced fork of the OAuth2 authorization server middleware that comes with Katana 3: there's an OWIN/Katana 3 version, and an ASP.NET Core version that supports both the full .NET framework and .NET Core.

https://github.com/aspnet-contrib/AspNet.Security.OpenIdConnect.Server

ASP.NET Core 1.x:

app.UseOpenIdConnectServer(options =>
{
    options.AllowInsecureHttp = true;
    options.TokenEndpointPath = new PathString("/token");
    options.AccessTokenLifetime = TimeSpan.FromDays(1);
    options.TokenEndpointPath = "/token";
    options.Provider = new SimpleAuthorizationServerProvider();
});

ASP.NET Core 2.x:

services.AddAuthentication().AddOpenIdConnectServer(options =>
{
    options.AllowInsecureHttp = true;
    options.TokenEndpointPath = new PathString("/token");
    options.AccessTokenLifetime = TimeSpan.FromDays(1);
    options.TokenEndpointPath = "/token";
    options.Provider = new SimpleAuthorizationServerProvider();
});

To learn more about this project, I'd recommend reading http://kevinchalet.com/2016/07/13/creating-your-own-openid-connect-server-with-asos-introduction/.

Good luck!

For anyone still looking for the original OAuth Authorization Server in ASP.NET 5, I have ported the code and the original sample here: https://github.com/XacronDevelopment/oauth-aspnet

The port includes backwards compatibility to allow ASP.NET 4.x resource servers to read the access tokens created by the authorization server.

The nuget packages are here: https://www.nuget.org/packages/OAuth.AspNet.AuthServer https://www.nuget.org/packages/OAuth.AspNet.Tokens https://www.nuget.org/packages/OAuth.Owin.Tokens