Add project files.

Discord.OAuth2/Discord.OAuth2.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="../../Discord.OAuth2.targets" />
+  <PropertyGroup>
+    <Description>ASP.Net Core middleware that enables an application to support Discord's OAuth 2.0 authentication workflow.</Description>
+    <RootNamespace>Discord.OAuth2</RootNamespace>
+    <AssemblyName>Discord.OAuth2</AssemblyName>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.OAuth" Version="2.2.0" />
+  </ItemGroup>
+</Project>

Discord.OAuth2/DiscordDefaults.cs

@@ -0,0 +1,12 @@
+namespace Discord.OAuth2
+{
+    public static class DiscordDefaults
+    {
+        public const string AuthenticationScheme = "Discord";
+        public const string DisplayName = "Discord";
+        
+        public static readonly string AuthorizationEndpoint = "https://discordapp.com/api/oauth2/authorize";
+        public static readonly string TokenEndpoint = "https://discordapp.com/api/oauth2/token";
+        public static readonly string UserInformationEndpoint = "https://discordapp.com/api/users/@me";
+    }
+}

Discord.OAuth2/DiscordExtensions.cs

@@ -0,0 +1,22 @@
+
+using System;
+using Microsoft.AspNetCore.Authentication;
+using Discord.OAuth2;
+
+namespace Microsoft.Extensions.DependencyInjection
+{
+    public static class DiscordAuthenticationOptionsExtensions
+    {
+        public static AuthenticationBuilder AddDiscord(this AuthenticationBuilder builder)
+            => builder.AddDiscord(DiscordDefaults.AuthenticationScheme, _ => { });
+
+        public static AuthenticationBuilder AddDiscord(this AuthenticationBuilder builder, Action<DiscordOptions> configureOptions)
+            => builder.AddDiscord(DiscordDefaults.AuthenticationScheme, configureOptions);
+
+        public static AuthenticationBuilder AddDiscord(this AuthenticationBuilder builder, string authenticationScheme, Action<DiscordOptions> configureOptions)
+            => builder.AddDiscord(authenticationScheme, DiscordDefaults.DisplayName, configureOptions);
+
+        public static AuthenticationBuilder AddDiscord(this AuthenticationBuilder builder, string authenticationScheme, string displayName, Action<DiscordOptions> configureOptions)
+            => builder.AddOAuth<DiscordOptions, DiscordHandler>(authenticationScheme, displayName, configureOptions);
+    }
+}

Discord.OAuth2/DiscordHandler.cs

@@ -0,0 +1,40 @@
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.OAuth;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Newtonsoft.Json.Linq;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Security.Claims;
+using System.Text.Encodings.Web;
+using System.Threading.Tasks;
+
+namespace Discord.OAuth2
+{
+    internal class DiscordHandler : OAuthHandler<DiscordOptions>
+    {
+        public DiscordHandler(IOptionsMonitor<DiscordOptions> options, ILoggerFactory logger, UrlEncoder encoder, ISystemClock clock)
+            : base(options, logger, encoder, clock)
+        {
+        }
+
+        protected override async Task<AuthenticationTicket> CreateTicketAsync(ClaimsIdentity identity, AuthenticationProperties properties, OAuthTokenResponse tokens)
+        {
+            var request = new HttpRequestMessage(HttpMethod.Get, Options.UserInformationEndpoint);
+            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", tokens.AccessToken);
+            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
+
+            var response = await Backchannel.SendAsync(request, Context.RequestAborted);
+            if (!response.IsSuccessStatusCode)
+                throw new HttpRequestException($"Failed to retrieve Discord user information ({response.StatusCode}).");
+
+            var payload = JObject.Parse(await response.Content.ReadAsStringAsync());
+
+            var context = new OAuthCreatingTicketContext(new ClaimsPrincipal(identity), properties, Context, Scheme, Options, Backchannel, tokens, payload);
+            context.RunClaimActions();
+
+            await Events.CreatingTicket(context);
+            return new AuthenticationTicket(context.Principal, context.Properties, Scheme.Name);
+        }
+    }
+}

Discord.OAuth2/DiscordOptions.cs

@@ -0,0 +1,33 @@
+using Microsoft.AspNetCore.Authentication;
+using Microsoft.AspNetCore.Authentication.OAuth;
+using Microsoft.AspNetCore.Http;
+using System.Security.Claims;
+
+namespace Discord.OAuth2
+{
+    /// <summary> Configuration options for <see cref="DiscordHandler"/>. </summary>
+    public class DiscordOptions : OAuthOptions
+    {
+        /// <summary> Initializes a new <see cref="DiscordOptions"/>. </summary>
+        public DiscordOptions()
+        {
+            CallbackPath = new PathString("/signin-discord");
+            AuthorizationEndpoint = DiscordDefaults.AuthorizationEndpoint;
+            TokenEndpoint = DiscordDefaults.TokenEndpoint;
+            UserInformationEndpoint = DiscordDefaults.UserInformationEndpoint;
+            Scope.Add("identify");
+
+            ClaimActions.MapJsonKey(ClaimTypes.NameIdentifier, "id", ClaimValueTypes.UInteger64);
+            ClaimActions.MapJsonKey(ClaimTypes.Name, "username", ClaimValueTypes.String);
+            ClaimActions.MapJsonKey(ClaimTypes.Email, "email", ClaimValueTypes.Email);
+            ClaimActions.MapJsonKey("urn:discord:discriminator", "discriminator", ClaimValueTypes.UInteger32);
+            ClaimActions.MapJsonKey("urn:discord:avatar", "avatar", ClaimValueTypes.String);
+            ClaimActions.MapJsonKey("urn:discord:verified", "verified", ClaimValueTypes.Boolean);
+        }
+        
+        /// <summary> Gets or sets the Discord-assigned appId. </summary>
+        public string AppId { get => ClientId; set => ClientId = value; }        
+        /// <summary> Gets or sets the Discord-assigned app secret. </summary>
+        public string AppSecret { get => ClientSecret; set => ClientSecret = value; }
+    }
+}