Use constant_time_compare from oslo.utils

oslo.utitls provided method constant_time_compare since 3.5.0,
so don't need maintain it by Nova any more.

Change-Id: I4f4b8fa6eff78f6d2e2139c419b558d737d249b7

nova/api/metadata/handler.py

@@ -21,6 +21,7 @@ import os
 
 from oslo_config import cfg
 from oslo_log import log as logging
+from oslo_utils import secretutils as secutils
 import six
 import webob.dec
 import webob.exc
@@ -33,7 +34,6 @@ from nova.i18n import _
 from nova.i18n import _LE
 from nova.i18n import _LW
 from nova.network.neutronv2 import api as neutronapi
-from nova import utils
 from nova import wsgi
 
 CONF = cfg.CONF
@@ -290,7 +290,7 @@ class MetadataRequestHandler(wsgi.Application):
             CONF.neutron.metadata_proxy_shared_secret,
             requestor_id, hashlib.sha256).hexdigest()
 
-        if not utils.constant_time_compare(expected_signature, signature):
+        if not secutils.constant_time_compare(expected_signature, signature):
             if requestor_id:
                 LOG.warning(_LW('X-Instance-ID-Signature: %(signature)s does '
                                 'not match the expected value: '

nova/tests/unit/test_metadata.py

@@ -842,7 +842,7 @@ class MetadataHandlerTestCase(test.TestCase):
                                 headers=None)
         self.assertEqual(response.status_int, 500)
 
-    @mock.patch('nova.utils.constant_time_compare')
+    @mock.patch('oslo_utils.secretutils.constant_time_compare')
     def test_by_instance_id_uses_constant_time_compare(self, mock_compare):
         mock_compare.side_effect = test.TestingException
 

nova/tests/unit/test_utils.py

@@ -1165,13 +1165,6 @@ class GetImageMetadataFromVolumeTestCase(test.NoDBTestCase):
         self.assertNotEqual({}, properties)
 
 
-class ConstantTimeCompareTestCase(test.NoDBTestCase):
-    def test_constant_time_compare(self):
-        self.assertTrue(utils.constant_time_compare("abcd1234", "abcd1234"))
-        self.assertFalse(utils.constant_time_compare("abcd1234", "a"))
-        self.assertFalse(utils.constant_time_compare("abcd1234", "ABCD234"))
-
-
 class ResourceFilterTestCase(test.NoDBTestCase):
     def _assert_filtering(self, res_list, filts, expected_tags):
         actual_tags = utils.filter_and_format_resource_metadata('instance',

nova/utils.py

@@ -23,7 +23,6 @@ import datetime
 import errno
 import functools
 import hashlib
-import hmac
 import inspect
 import logging as std_logging
 import os
@@ -1321,23 +1320,6 @@ def get_hash_str(base_str):
         base_str = base_str.encode('utf-8')
     return hashlib.md5(base_str).hexdigest()
 
-if hasattr(hmac, 'compare_digest'):
-    constant_time_compare = hmac.compare_digest
-else:
-    def constant_time_compare(first, second):
-        """Returns True if both string inputs are equal, otherwise False.
-
-        This function should take a constant amount of time regardless of
-        how many characters in the strings match.
-
-        """
-        if len(first) != len(second):
-            return False
-        result = 0
-        for x, y in zip(first, second):
-            result |= ord(x) ^ ord(y)
-        return result == 0
-
 
 def filter_and_format_resource_metadata(resource_type, resource_list,
         search_filts, metadata_type=None):