Adding tarfile member sanitization to extractall() (#878)

bin/lib/cdn.py

@@ -90,7 +90,26 @@ def __unpack_tar(self):
         # unpack tar contents
         logger.debug('unpacking "%s" into "%s"', self.tar_file_path, self.tmpdir)
         with tarfile.open(self.tar_file_path) as tar:
-            tar.extractall(self.tmpdir)
+            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, self.tmpdir)
 
         return list(get_directory_contents(self.tmpdir))