101 lines
3.5 KiB
Diff
101 lines
3.5 KiB
Diff
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From 3dd2cb0452b63d5de04606d79bbbf41a4e50a42a Mon Sep 17 00:00:00 2001
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From: Grant Murphy <gmurphy@redhat.com>
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Date: Tue, 8 Jul 2014 03:35:40 +0000
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Subject: [PATCH 1/1] Avoid possible timing attack in metadata api
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Introduce a constant time comparison function to
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nova utils for comparing authentication tokens.
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Original code taken from:
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https://github.com/openstack/python-keystoneclient/blob/master/keystoneclient/middleware/memcache_crypt.py#L86
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Change-Id: I7374f2edc6f03c7da59cf73ae91a87147e53d0de
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Closes-bug: #1325128
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---
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nova/api/metadata/handler.py | 3 ++-
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nova/tests/test_utils.py | 7 +++++++
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nova/utils.py | 27 +++++++++++++++++++++++++++
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3 files changed, 36 insertions(+), 1 deletion(-)
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diff --git a/nova/api/metadata/handler.py b/nova/api/metadata/handler.py
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index a14db67..be866ef 100644
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--- a/nova/api/metadata/handler.py
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+++ b/nova/api/metadata/handler.py
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@@ -30,6 +30,7 @@ from nova import exception
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from nova.openstack.common.gettextutils import _
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from nova.openstack.common import log as logging
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from nova.openstack.common import memorycache
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+from nova import utils
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from nova import wsgi
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CACHE_EXPIRATION = 15 # in seconds
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@@ -169,7 +170,7 @@ class MetadataRequestHandler(wsgi.Application):
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instance_id,
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hashlib.sha256).hexdigest()
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- if expected_signature != signature:
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+ if not utils.constant_time_compare(expected_signature, signature):
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if instance_id:
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LOG.warn(_('X-Instance-ID-Signature: %(signature)s does not '
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'match the expected value: %(expected_signature)s '
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diff --git a/nova/tests/test_utils.py b/nova/tests/test_utils.py
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index 59d08fd..c2969a6 100644
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--- a/nova/tests/test_utils.py
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+++ b/nova/tests/test_utils.py
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@@ -979,3 +979,10 @@ class VersionTestCase(test.NoDBTestCase):
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def test_convert_version_to_tuple(self):
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self.assertEqual(utils.convert_version_to_tuple('6.7.0'), (6, 7, 0))
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+
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+
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+class ConstantTimeCompareTestCase(test.NoDBTestCase):
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+ def test_constant_time_compare(self):
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+ self.assertTrue(utils.constant_time_compare("abcd1234", "abcd1234"))
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+ self.assertFalse(utils.constant_time_compare("abcd1234", "a"))
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+ self.assertFalse(utils.constant_time_compare("abcd1234", "ABCD234"))
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diff --git a/nova/utils.py b/nova/utils.py
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index 0c3ee94..7dfa0cc 100644
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--- a/nova/utils.py
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+++ b/nova/utils.py
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@@ -21,6 +21,7 @@ import contextlib
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import datetime
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import functools
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import hashlib
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+import hmac
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import inspect
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import multiprocessing
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import os
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@@ -1170,3 +1171,29 @@ def cpu_count():
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return multiprocessing.cpu_count()
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except NotImplementedError:
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return 1
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+
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+
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+# NOTE(gm) Constant time comparison taken from keystone. This is a
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+# candidate for inclusion in oslo.
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+#
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+# Original code: master/keystoneclient/middleware/memcache_crypt.py#L86
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+if sys.version_info >= (3, 3):
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+ constant_time_compare = hmac.compare_digest
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+else:
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+ def constant_time_compare(first, second):
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+ """Returns True if both string inputs are equal, otherwise False.
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+
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+ This function should take a constant amount of time regardless of
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+ how many characters in the strings match.
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+
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+ """
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+ if len(first) != len(second):
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+ return False
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+ result = 0
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+ if six.PY3 and isinstance(first, bytes) and isinstance(second, bytes):
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+ for x, y in zip(first, second):
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+ result |= x ^ y
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+ else:
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+ for x, y in zip(first, second):
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+ result |= ord(x) ^ ord(y)
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+ return result == 0
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--
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1.9.3
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