vtuber-awards/Backend/Security/SecurityHeadersMiddleware.cs

namespace Backend.Security;

public sealed class SecurityHeadersMiddleware(RequestDelegate next)
{
    public async Task InvokeAsync(HttpContext context)
    {
        context.Response.OnStarting(() =>
        {
            var headers = context.Response.Headers;
            headers["X-Content-Type-Options"] = "nosniff";
            headers["X-Frame-Options"] = "DENY";
            headers["Referrer-Policy"] = "strict-origin-when-cross-origin";
            headers["Permissions-Policy"] = "camera=(), microphone=(), geolocation=()";
            headers["Cross-Origin-Opener-Policy"] = "same-origin";

            if (!headers.ContainsKey("Content-Security-Policy"))
            {
                headers["Content-Security-Policy"] =
                    "default-src 'self'; " +
                    "img-src 'self' data: https:; " +
                    "font-src 'self' https://fonts.gstatic.com data:; " +
                    "style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; " +
                    "script-src 'self'; " +
                    "connect-src 'self' https:; " +
                    "frame-ancestors 'none'; " +
                    "base-uri 'self'; " +
                    "form-action 'self';";
            }

            return Task.CompletedTask;
        });

        await next(context);
    }
}