Radicade/Server/CDN/SigsCDN.cs

using System.Text;
using Microsoft.AspNetCore.Mvc;

namespace RadicadeServer.CDN
{
	[Route("cdn/sigs")]
	public class SigsCDN : Controller
	{

		private static readonly byte[] PlaceholderSignature = Encoding.ASCII.GetBytes(
			"RecRoom.exe:AAAAAAAAAAAAAAAAAAAAAA==:AAAAAAAAAAAAAAAAAAAAAA==\n" +
			"RecRoom_Data/globalgamemanagers:AAAAAAAAAAAAAAAAAAAAAA==:AAAAAAAAAAAAAAAAAAAAAA==\n" +
			"GameAssembly.dll:AAAAAAAAAAAAAAAAAAAAAA==:AAAAAAAAAAAAAAAAAAAAAA==\n");

		[HttpGet("{signatureId}")]
		public IActionResult GetSignature(string signatureId)
		{
			if (string.IsNullOrWhiteSpace(signatureId)) return BadRequest();

			var rangeHeader = ControllerContext.HttpContext?.Request.Headers.Range.ToString();
			if (string.IsNullOrWhiteSpace(rangeHeader) || !rangeHeader.StartsWith("bytes=", StringComparison.OrdinalIgnoreCase))
				return File(PlaceholderSignature, "text/plain");

			var (start, end) = ParseByteRange(rangeHeader, PlaceholderSignature.Length);
			var count = end - start + 1;
			var body = new byte[count];
			Array.Copy(PlaceholderSignature, start, body, 0, count);

			Response.Headers.AcceptRanges = "bytes";
			Response.Headers.ContentRange = $"bytes {start}-{end}/{PlaceholderSignature.Length}";
			Response.StatusCode = StatusCodes.Status206PartialContent;
			return File(body, "text/plain", enableRangeProcessing: false);
		}

		private static (int Start, int End) ParseByteRange(string rangeHeader, int length)
		{
			var spec = rangeHeader["bytes=".Length..].Trim();
			if (spec.Contains(',')) return (0, length - 1);

			var parts = spec.Split('-', 2);
			if (parts.Length != 2) return (0, length - 1);

			if (parts[0].Length == 0)
			{
				if (!int.TryParse(parts[1], out var suffixLength) || suffixLength <= 0)
					return (0, length - 1);

				var start = Math.Max(0, length - suffixLength);
				return (start, length - 1);
			}

			if (!int.TryParse(parts[0], out var parsedStart))
				return (0, length - 1);

			var startOffset = parsedStart >= length ? 0 : Math.Max(0, parsedStart);
			var endOffset = length - 1;
			if (parts[1].Length > 0 && int.TryParse(parts[1], out var parsedEnd))
				endOffset = Math.Clamp(parsedEnd, startOffset, length - 1);

			return (startOffset, endOffset);
		}
	}
}