How can I configure an OpenID Connect for Steam in ASP.NET Core 2?

Question

I am attempting to authenticate and login users through the Steam API using ASP.Net Core 2.

I'm having limited success. I think I need the following parameters:

    providerURL: 'http://steamcommunity.com/openid',
    stateless: true,
    // How the OpenID provider should return the client to us
    returnURL: 'http://localhost:4000/auth/openid/return',
    realm: 'http://localhost:4000/',

I am attempting to add the authentication via the AddOpenIDConnect mechanism.

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddIdentity<ApplicationUser, IdentityRole>()
            .AddEntityFrameworkStores<ApplicationDbContext>()
            .AddDefaultTokenProviders();

        services.AddAuthentication().AddOpenIdConnect(steamOptions =>
        {
            steamOptions.ClientId = "<APIKEY>";
            steamOptions.ClaimsIssuer = "https://steamcommunity.com/openid";
        }

This doesn't work. Clearly, there has to be a better way to call this.

One noticeable thing I've encountered: a GET request with Postman returns an XML file:

<?xml version="1.0" encoding="UTF-8"?>
<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
<XRD>
    <Service priority="0">
        <Type>http://specs.openid.net/auth/2.0/server</Type>
        <URI>https://steamcommunity.com/openid/login</URI>
    </Service>
</XRD>
</xrds:XRDS>

Is there any way we can force services.AddAuthentication() to parse XML?

Answer 1

I solved this with the AspNet.Security.OpenID.Steam library that Kévin Chalet just recently built. You'll need to use the 2.0.0-rc2-final for ASP.Net Core 2.

All you need to do is add services.AddAuthentication().AddSteam() into ConfigureServices, like so (it's not the only service in there):

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication().AddSteam();
}

Note that you'll need the other default services generated by the Asp.Net Core 2 Web MVC template and Identity installed.