Fix directory traversal in extension_resources.cc. Adds test case, which is complicated by several…

chrome/common/extensions/extension_resource.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/extensions/extension_resource.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
 
@@ skipping 49 matching lines @@
   // path before resolving the symlink must still be within it.
   if (symlink_policy == FOLLOW_SYMLINKS_ANYWHERE) {
     std::vector<FilePath::StringType> components;
     relative_path.GetComponents(&components);
     int depth = 0;
 
     for (std::vector<FilePath::StringType>::const_iterator
          i = components.begin(); i != components.end(); i++) {
       if (*i == FilePath::kParentDirectory) {
         depth--;
-      } else {
+      } else if (*i != FilePath::kCurrentDirectory) {
         depth++;
       }
       if (depth < 0) {
         return FilePath();
       }
     }
   }
 
   // We must resolve the absolute path of the combined path when
   // the relative path contains references to a parent folder (i.e., '..').
@@ skipping 31 matching lines @@
   // Make sure we have a cached value to test against...
   if (full_resource_path_.empty())
     GetFilePath();
   if (NormalizeSeperators(path.value()) ==
     NormalizeSeperators(full_resource_path_.value())) {
     return true;
   } else {
     return false;
   }
 }