add a bunch of stuff copied from Foxchat.NET

Foxnouns.Backend/Middleware/AuthenticationMiddleware.cs

@@ -0,0 +1,66 @@
+using System.Security.Cryptography;
+using Foxnouns.Backend.Database;
+using Foxnouns.Backend.Database.Models;
+using Foxnouns.Backend.Utils;
+using Microsoft.EntityFrameworkCore;
+using NodaTime;
+
+namespace Foxnouns.Backend.Middleware;
+
+public class AuthenticationMiddleware(DatabaseContext db, IClock clock) : IMiddleware
+{
+    public async Task InvokeAsync(HttpContext ctx, RequestDelegate next)
+    {
+        var endpoint = ctx.GetEndpoint();
+        var metadata = endpoint?.Metadata.GetMetadata<AuthenticateAttribute>();
+
+        if (metadata == null)
+        {
+            await next(ctx);
+            return;
+        }
+
+        var header = ctx.Request.Headers.Authorization.ToString();
+        if (!OauthUtils.TryFromBase64String(header, out var rawToken))
+        {
+            await next(ctx);
+            return;
+        }
+
+        var hash = SHA512.HashData(rawToken);
+        var oauthToken = await db.Tokens
+            .Include(t => t.Application)
+            .Include(t => t.User)
+            .FirstOrDefaultAsync(t => t.Hash == hash && t.ExpiresAt > clock.GetCurrentInstant() && !t.ManuallyExpired);
+        if (oauthToken == null)
+        {
+            await next(ctx);
+            return;
+        }
+
+        ctx.SetToken(oauthToken);
+
+        await next(ctx);
+    }
+}
+
+public static class HttpContextExtensions
+{
+    private const string Key = "token";
+
+    public static void SetToken(this HttpContext ctx, Token token) => ctx.Items.Add(Key, token);
+    public static User? GetUser(this HttpContext ctx) => ctx.GetToken()?.User;
+
+    public static User GetUserOrThrow(this HttpContext ctx) =>
+        ctx.GetUser() ?? throw new ApiError.AuthenticationError("No user in HttpContext");
+
+    public static Token? GetToken(this HttpContext ctx)
+    {
+        if (ctx.Items.TryGetValue(Key, out var token))
+            return token as Token;
+        return null;
+    }
+}
+
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
+public class AuthenticateAttribute : Attribute;