add UseAnyURLPrefix setting

src/Configuration/AssetServerConfig.cs

@@ -4,6 +4,7 @@ public class AssetServerConfig {
     public string ListenIP { get; set; } = string.Empty;
     public int Port { get; set; } = 5001;
     public string URLPrefix { get; set; } = string.Empty;
+    public bool UseAnyURLPrefix { get; set; } = true;
     public AssetServerMode Mode { get; set; }
     public string ProviderURL { get; set; } = string.Empty;
     public string AutoEncryptRegexp { get; set; } = string.Empty;

src/Middleware/AssetMiddleware.cs

@@ -34,12 +34,27 @@ public class AssetMiddleware
     {
         string path = context.Request.Path;
 
-        if (path is null || !string.IsNullOrEmpty(config.Value.URLPrefix) && !path.StartsWith("/" + config.Value.URLPrefix) || config.Value.Mode == AssetServerMode.None) {
+        if (path is null || config.Value.Mode == AssetServerMode.None) {
             context.Response.StatusCode = 400;
             return;
         }
 
-        string assetPath = path.Remove(0, config.Value.URLPrefix.Length + 1);
+        string assetPath;
+        if (config.Value.UseAnyURLPrefix) {
+            int firstSlash = path.IndexOf('/', 1);
+            if (firstSlash < 0) {
+                context.Response.StatusCode = 400;
+                return;
+            }
+            assetPath = path.Remove(0, firstSlash + 1);
+        } else {
+            if (!string.IsNullOrEmpty(config.Value.URLPrefix) && !path.StartsWith("/" + config.Value.URLPrefix)) {
+                context.Response.StatusCode = 400;
+                return;
+            }
+            assetPath = path.Remove(0, config.Value.URLPrefix.Length + 1);
+        }
+
         string localPath = GetLocalPath("assets/" + assetPath);
 
         if (localPath == string.Empty && config.Value.Mode == AssetServerMode.Partial && config.Value.UseCache)

src/appsettings.json

@@ -17,9 +17,15 @@
     "// Port": "Listening port number for the asset server. Should be different than for the server API",
     "Port": 5001,
 
-    "// URLPrefix": "Extra prefix in the URL; omitted while retrieving the path from the requested URL. For example, if set to '.com', then a request to http://localhost/.com/abc will return the 'abc' file from the assets folder",
+    "// URLPrefix (1)": "Extra prefix in the URL; omitted while retrieving the path from the requested URL. See also: UseAnyURLPrefix setting.",
+    "// URLPrefix (2)": "For example, if set to '.com', then a request to 'http://localhost/.com/abc' will return the 'abc' file from the assets folder.",
     "URLPrefix": ".com",
 
+    "// UseAnyURLPrefix (1)": "Extended version of URLPrefix (if set to true, then URLPrefix setting will be ignored).",
+    "// UseAnyURLPrefix (2)": "When true requires that requested URL contained extra prefix (one directory at path start), that will be omitted while retrieving the path from the requested URL.",
+    "// UseAnyURLPrefix (3)": "If set to true, then (for example) a request to 'http://localhost/any.com/abc' will return the 'abc' file from the assets folder ('any.com' will be omitted).",
+    "UseAnyURLPrefix": true,
+
     "// Mode": "Two modes: full - everything is local, partial - downloads assets from ProviderURL if not found locally",
     "Mode": "partial",