From 754633988931e4095530f6b13389c254096eb485 Mon Sep 17 00:00:00 2001
From: Samuel Merritt <sam@swiftstack.com>
Date: Thu, 16 Jan 2014 13:40:53 +0100
Subject: [PATCH] Use constant time comparison in tempURL
Use constant time comparison when evaluating tempURL to avoid timing
attacks (CVE-2014-0006).
Fixes bug 1265665
Change-Id: I11e4ad83cc4077e52adf54a0bd0f9749294b2a48
---
swift/common/middleware/tempurl.py | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/swift/common/middleware/tempurl.py b/swift/common/middleware/tempurl.py
index c9b9d9437d..57486941b5 100644
--- a/swift/common/middleware/tempurl.py
+++ b/swift/common/middleware/tempurl.py
@@ -106,7 +106,7 @@ from urlparse import parse_qs
from swift.proxy.controllers.base import get_account_info
from swift.common.swob import HeaderKeyDict, HTTPUnauthorized
from swift.common.utils import split_path, get_valid_utf8_str, \
- register_swift_info, get_hmac
+ register_swift_info, get_hmac, streq_const_time
#: Default headers to remove from incoming requests. Simply a whitespace
@@ -284,7 +284,13 @@ class TempURL(object):
request_method='PUT'))
else:
hmac_vals = self._get_hmacs(env, temp_url_expires, keys)
- if temp_url_sig not in hmac_vals:
+
+ # 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, hmac)
+ for hmac 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