From 754633988931e4095530f6b13389c254096eb485 Mon Sep 17 00:00:00 2001 From: Samuel Merritt 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