From b2c61375b3255486adb2900922a894dc7dad3c6d Mon Sep 17 00:00:00 2001 From: Samuel Merritt Date: Thu, 16 Jan 2014 13:44:23 +0100 Subject: [PATCH] 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 --- swift/common/middleware/tempurl.py | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/swift/common/middleware/tempurl.py b/swift/common/middleware/tempurl.py index ffc14313b3..ae2f4a117c 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