feat: allow /FramePlayer to be embedded in external iframes via CORS + CSP frame-ancestors

DeepDrftPublic/Program.cs

@@ -24,6 +24,11 @@ Startup.ConfigureDomainServices(builder);
 
 // Add services to the container.
 builder.Services.AddControllers();
+builder.Services.AddCors(options =>
+{
+    options.AddPolicy("FramePlayerEmbedPolicy", policy =>
+        policy.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod());
+});
 builder.Services.AddRazorComponents()
     .AddInteractiveServerComponents()
     .AddInteractiveWebAssemblyComponents();
@@ -72,6 +77,26 @@ else
     }
 }
 
+app.UseCors("FramePlayerEmbedPolicy");
+
+// For requests to /FramePlayer, remove any X-Frame-Options header and set a permissive
+// frame-ancestors CSP so the page can be embedded in iframes on any external domain.
+// OnStarting fires just before headers are flushed, ensuring this overrides headers set
+// by other middleware (e.g. HSTS, reverse proxy).
+app.Use(async (context, next) =>
+{
+    if (context.Request.Path.StartsWithSegments("/FramePlayer", StringComparison.OrdinalIgnoreCase))
+    {
+        context.Response.OnStarting(() =>
+        {
+            context.Response.Headers.Remove("X-Frame-Options");
+            context.Response.Headers["Content-Security-Policy"] = "frame-ancestors *";
+            return Task.CompletedTask;
+        });
+    }
+    await next();
+});
+
 // Antiforgery is required by Blazor form handling. Authentication / authorization
 // middleware is intentionally absent — this host is fully anonymous.
 app.UseAntiforgery();