为什么此CORS政策无法使用ASP.NET Core

Question

I've been trying to set up Discord Oauth2 token authentication on an ASP.NET Core 2.2 / Angular 7 project and it has been quite a bumpy ride.

I'm using this

I really can't seem to find any examples that give more than a fraction of the explanation required to set this all up. The error I'm currently battling with is the following:

Access to XMLHttpRequest at 'https://discordapp.com/oauth2/authorize?client_id=<removed>&scope=identify&response_type=code&redirect_uri=http%3A%2F%2Flocalhost%3A5000%2Fsignin-discord&state=<removed>'
(redirected from 'http://localhost:5000/api/v1/Authentication/SignIn') from origin 'http://localhost:5000' has been blocked by CORS policy: 
Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource

For context, here is some of my code:

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy("AllowAll",
            builder => builder.WithOrigins("http://localhost:5000").AllowAnyHeader());
    });
    ...
    services.AddAuthentication(options =>
        {
            options.DefaultScheme = DiscordAuthenticationDefaults.AuthenticationScheme;
            options.DefaultChallengeScheme = DiscordAuthenticationDefaults.AuthenticationScheme;
            options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            options.DefaultSignOutScheme = CookieAuthenticationDefaults.AuthenticationScheme;
        }).AddCookie(options =>
        {
            options.LoginPath = "/login";
            options.LogoutPath = "/signout";
            options.ExpireTimeSpan = TimeSpan.FromMinutes(10);
            options.SlidingExpiration = true;
        })
        .AddDiscord(options =>
        {
            options.ClientId = "<removed>";
            options.ClientSecret = "<removed>";
            options.Scope.Add("identify");
        });
    ...
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    ...
    app.UseCors("AllowAll");
    ...
}

// in AuthenticationController.cs
public class AuthenticationController : Controller
{
    [HttpPost("[action]")]
    public IActionResult SignIn()
    {
        return Challenge(new AuthenticationProperties {RedirectUri = "http://localhost:5000"});
    }
    ...
}

What i've been trying

I tried following this

I tried all of these combinations of services.addCors() and app.UseCors() to no avail

services.AddCors();
app.UseCors(builder =>
   builder.WithOrigins("http://localhost:5000").AllowAnyHeader());

services.AddCors();
app.UseCors(builder =>
   builder.AllowAnyOrigin().AllowAnyMethod().AllowAnyHeader());

and everything inbetween. The error does not change no matter what I do with cors. Also, yes I have the Microsoft.AspNetCore.Cors nu-get package installed. Yes, app.UseCors() is called before app.useMvc

Any other ideas?

Answer 1

I experienced a similar issue today but figured it out later. Make sure you are using the same versions of net core. I happened to be using both 2.1 and 2.2 packages.