Radicade Public Code

Server/CDN/CdnStorageNames.cs

@@ -0,0 +1,47 @@
+using RadicadeServer.Utils;
+
+namespace RadicadeServer.CDN
+{
+	/// <summary>
+	/// What may be read out of the CDN storage directory and handed to a client, and which file
+	/// a requested name actually is.
+	///
+	/// Two rules live here because every route that serves a stored blob needs both, and a route
+	/// that re-implements them gets one of them wrong:
+	///
+	/// - A request is a single bare file name in that one directory. A name carrying a separator
+	///   or <c>..</c> would let a URL read outside it, and a name ending in the admin upload's
+	///   <c>.uploading</c> suffix is a half-imported bundle: it must answer as if it does not
+	///   exist rather than serve a truncated file, which the client would then fail to load with
+	///   no way to tell why.
+	/// - A bundle is asked for under two spellings. The subroom's <c>UnityAssetId</c> is stored
+	///   both bare and with the <c>.assetbundle</c> suffix an import appends, so a name resolves
+	///   to the exact file first and to <c>&lt;name&gt;.assetbundle</c> second.
+	/// </summary>
+	internal static class CdnStorageNames
+	{
+		internal static bool IsServable(string? name) =>
+			!string.IsNullOrEmpty(name)
+			&& name != "."
+			&& !AdminUtils.IsUploadPart(name)
+			&& !name.Contains('/')
+			&& !name.Contains('\\')
+			&& !name.Contains("..")
+			&& name.IndexOf('\0') < 0;
+
+		/// <summary>
+		/// The stored file a requested name is, or null when nothing by either spelling exists.
+		/// A name this server must never serve answers null too, so a route that only checks the
+		/// result is still safe.
+		/// </summary>
+		internal static string? Resolve(string? name)
+		{
+			if (!IsServable(name)) return null;
+
+			if (System.IO.File.Exists(Path.Join(DBConfig.CDNStorage, name))) return name;
+
+			var withExtension = name + ".assetbundle";
+			return System.IO.File.Exists(Path.Join(DBConfig.CDNStorage, withExtension)) ? withExtension : null;
+		}
+	}
+}