Make path handling more robust since path is user defined

src/WireMock.Net/Handlers/LocalFileSystemHandler.cs

@@ -80,7 +80,7 @@ public void WriteMappingFile(string path, string text)
         public byte[] ReadResponseBodyAsFile(string path)
         {
             Check.NotNullOrEmpty(path, nameof(path));
-
+            path = CleanPath(path);
             // If the file exists at the given path relative to the MappingsFolder, then return that.
             // Else the path will just be as-is.
             return File.ReadAllBytes(File.Exists(Path.Combine(GetMappingFolder(), path)) ? Path.Combine(GetMappingFolder(), path) : path);
@@ -90,7 +90,7 @@ public byte[] ReadResponseBodyAsFile(string path)
         public string ReadResponseBodyAsString(string path)
         {
             Check.NotNullOrEmpty(path, nameof(path));
-
+            path = CleanPath(path);
             // In case the path is a filename, the path will be adjusted to the MappingFolder.
             // Else the path will just be as-is.
             return File.ReadAllText(File.Exists(Path.Combine(GetMappingFolder(), path)) ? Path.Combine(GetMappingFolder(), path) : path);
@@ -138,5 +138,20 @@ private string AdjustPath(string filename)
         {
             return Path.Combine(GetMappingFolder(), filename);
         }
+
+        /// <summary>
+        /// Robust handling of the user defined path.
+        /// Gets the path string ready for Path.Combine method.
+        /// </summary>
+        /// <param name="path">Path to clean</param>
+        /// <returns></returns>
+        private string CleanPath(string path)
+        {
+            path = path.Replace("/", @"\");
+            // remove leading \ character which would break Path.Combine
+            path = path.StartsWith(@"\") ? path.Substring(1, path.Length - 1) : path;
+
+            return path;
+        }
     }
 }