Adding tarfile member sanitization to extractall()

common/lib/xmodule/xmodule/tests/test_export.py

@@ -246,7 +246,26 @@ def _expand_archive(self, name):
         target = path(self.temp_dir) / uuid.uuid4().hex
         os.mkdir(target)
         with tarfile.open(self.data_dir / name) as tar_file:
-            tar_file.extractall(path=target)
+            def is_within_directory(directory, target):
+
+                abs_directory = os.path.abspath(directory)
+                abs_target = os.path.abspath(target)
+
+                prefix = os.path.commonprefix([abs_directory, abs_target])
+
+                return prefix == abs_directory
+
+            def safe_extract(tar, path=".", members=None, *, numeric_owner=False):
+
+                for member in tar.getmembers():
+                    member_path = os.path.join(path, member.name)
+                    if not is_within_directory(path, member_path):
+                        raise Exception("Attempted Path Traversal in Tar File")
+
+                tar.extractall(path, members, numeric_owner=numeric_owner) 
+
+
+            safe_extract(tar_file, path=target)
 
         return target