GetExternalLoginInfoAsync在ASP.NET Core 2.0中返回null

Question

I want to connect to GitHub using OAuth in aspnet core 2.0. I have the following setup.

Startup.cs:

services.AddDbContext<DbContext>(options =>
            options.UseNpgsql(Configuration.GetConnectionString("DefaultConnection"))
        );

        services.AddIdentity<User, Role>()
        .AddEntityFrameworkStores<DbContext>()
        .AddDefaultTokenProviders();

        services.AddMvc(options => options.OutputFormatters.Add(new HtmlOutputFormatter()));
        services.AddAntiforgery(x => x.HeaderName = "X-XSRF-TOKEN");

        services.AddAuthentication(options =>
        {
            options.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
        })
        .AddCookie()
        .AddGitHub(options =>
        {
            options.ClientId = "xxxxxxxxxx";
            options.ClientSecret = "xxxxxxxxxxxxxxx";
            options.CallbackPath = new PathString("/auth/callback/GitHub");
        })

Controller:

[HttpGet("{provider}")]
    public IActionResult Index(string provider)
    {
        return Challenge(new AuthenticationProperties() { RedirectUri = Url.Action("CallBack", "Auth") }, provider);
    }

[HttpGet("callback")]
    public async Task<IActionResult> CallBack()
    {
        var info = await _signInManager.GetExternalLoginInfoAsync(); // <== this is always NULL
        return Redirect("~/");
    }

The auth flow gets completed correctly and without errors. However, the line

var info = await _signInManager.GetExternalLoginInfoAsync();

always yields null.

There are some leads scattered around the web, like this one , bit none seem to scratch my itch.

Thoughts? Am I missing a setting somewhere? Probably...

Thanks!

Answer 1

when using with identityserver4, in the following part of code IdentityConstants.ExternalScheme was not matching and hence "auth" was null .

However, changing it to idsrv.external keeps it going.

 public async Task<ExternalLoginInfo> GetExternalLoginInfoAsync(string expectedXsrf = null)
    {
        var auth = await HttpContext.AuthenticateAsync(IdentityConstants.ExternalScheme);
        var items = auth?.Properties?.Items;
        if (auth?.Principal == null || items == null || !items.ContainsKey("LoginProviderKey"))