Merge "Create secretutils and include 'constant_time_compare' function"

doc/source/api/secretutils.rst

@@ -0,0 +1,6 @@
+=============
+ secretutils
+=============
+
+.. automodule:: oslo_utils.secretutils
+   :members:

doc/source/index.rst

@@ -28,6 +28,7 @@ API Documentation
    api/importutils
    api/netutils
    api/reflection
+   api/secretutils
    api/strutils
    api/timeutils
    api/units

oslo_utils/secretutils.py

@@ -0,0 +1,35 @@
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import hmac
+
+
+try:
+    constant_time_compare = hmac.compare_digest
+except AttributeError:
+    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. This function uses an
+        approach designed to prevent timing analysis by avoiding
+        content-based short circuiting behaviour, making it appropriate
+        for cryptography.
+        """
+        if len(first) != len(second):
+            return False
+        result = 0
+        for x, y in zip(first, second):
+            result |= ord(x) ^ ord(y)
+        return result == 0

oslo_utils/tests/test_secretutils.py

@@ -0,0 +1,52 @@
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from oslotest import base as test_base
+import testscenarios
+
+from oslo_utils import secretutils
+
+
+class SecretUtilsTest(testscenarios.TestWithScenarios,
+                      test_base.BaseTestCase):
+
+    scenarios = [
+        ('binary', {'converter': lambda text: text.encode('utf-8')}),
+        ('unicode', {'converter': lambda text: text}),
+    ]
+
+    def test_constant_time_compare(self):
+        # make sure it works as a compare, the "constant time" aspect
+        # isn't appropriate to test in unittests
+        ctc = secretutils.constant_time_compare
+        self.assertTrue(ctc(self.converter(u'abcd'),
+                            self.converter(u'abcd')))
+        self.assertTrue(ctc(self.converter(u''),
+                            self.converter(u'')))
+        self.assertFalse(ctc(self.converter(u'abcd'),
+                             self.converter(u'efgh')))
+        self.assertFalse(ctc(self.converter(u'abc'),
+                             self.converter(u'abcd')))
+        self.assertFalse(ctc(self.converter(u'abc'),
+                             self.converter(u'abc\x00')))
+        self.assertFalse(ctc(self.converter(u''),
+                             self.converter(u'abc')))
+        self.assertTrue(ctc(self.converter(u'abcd1234'),
+                            self.converter(u'abcd1234')))
+        self.assertFalse(ctc(self.converter(u'abcd1234'),
+                             self.converter(u'ABCD234')))
+        self.assertFalse(ctc(self.converter(u'abcd1234'),
+                             self.converter(u'a')))
+        self.assertFalse(ctc(self.converter(u'abcd1234'),
+                             self.converter(u'1234abcd')))