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From b2c61375b3255486adb2900922a894dc7dad3c6d Mon Sep 17 00:00:00 2001
From: Samuel Merritt <sam@swiftstack.com>
Date: Thu, 16 Jan 2014 13:44:23 +0100
Subject: Use constant time comparison in tempURL
Use constant time comparison when evaluating tempURL to avoid timing
attacks (CVE-2014-0006). This is the havana backport of the master
patch.
Fixes bug 1265665
Change-Id: I11e4ad83cc4077e52adf54a0bd0f9749294b2a48
diff --git a/swift/common/middleware/tempurl.py b/swift/common/middleware/tempurl.py
index ffc1431..ae2f4a1 100644
--- a/swift/common/middleware/tempurl.py
+++ b/swift/common/middleware/tempurl.py
@@ -98,7 +98,7 @@ from urlparse import parse_qs
from swift.proxy.controllers.base import get_account_info
from swift.common.swob import HeaderKeyDict
-from swift.common.utils import split_path
+from swift.common.utils import split_path, streq_const_time
#: Default headers to remove from incoming requests. Simply a whitespace
@@ -267,17 +267,20 @@ class TempURL(object):
if not keys:
return self._invalid(env, start_response)
if env['REQUEST_METHOD'] == 'HEAD':
- hmac_vals = self._get_hmacs(env, temp_url_expires, keys,
- request_method='GET')
- if temp_url_sig not in hmac_vals:
- hmac_vals = self._get_hmacs(env, temp_url_expires, keys,
- request_method='PUT')
- if temp_url_sig not in hmac_vals:
- return self._invalid(env, start_response)
+ hmac_vals = (self._get_hmacs(env, temp_url_expires, keys,
+ request_method='GET') +
+ self._get_hmacs(env, temp_url_expires, keys,
+ request_method='PUT'))
else:
hmac_vals = self._get_hmacs(env, temp_url_expires, keys)
- if temp_url_sig not in hmac_vals:
- return self._invalid(env, start_response)
+
+ # While it's true that any() will short-circuit, this doesn't affect
+ # the timing-attack resistance since the only way this will
+ # short-circuit is when a valid signature is passed in.
+ is_valid_hmac = any(streq_const_time(temp_url_sig, h)
+ for h in hmac_vals)
+ if not is_valid_hmac:
+ return self._invalid(env, start_response)
self._clean_incoming_headers(env)
env['swift.authorize'] = lambda req: None
env['swift.authorize_override'] = True
--
cgit v0.10.1
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