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authorAndrey Andreev <narf@devilix.net>2014-02-06 04:34:19 +0100
committerAndrey Andreev <narf@devilix.net>2014-02-06 04:34:19 +0100
commit3aa781a65267d72000009df0fa2feee5cb3bdd8d (patch)
tree45aae14cc3ad37240bedee7e2db71d1b06ae363f
parentf6779f5e2510811a1d4fe39864923226a475f298 (diff)
Make CI_Session's HMAC comparison time-attack-safe
-rw-r--r--system/libraries/Session/drivers/Session_cookie.php10
1 files changed, 9 insertions, 1 deletions
diff --git a/system/libraries/Session/drivers/Session_cookie.php b/system/libraries/Session/drivers/Session_cookie.php
index 971dfeabe..c8dfad6c9 100644
--- a/system/libraries/Session/drivers/Session_cookie.php
+++ b/system/libraries/Session/drivers/Session_cookie.php
@@ -395,7 +395,15 @@ class CI_Session_cookie extends CI_Session_driver {
$hmac = substr($session, $len);
$session = substr($session, 0, $len);
- if ($hmac !== hash_hmac('sha1', $session, $this->encryption_key))
+ // Time-attack-safe comparison
+ $hmac_check = hash_hmac('sha1', $session, $this->encryption_key);
+ $diff = 0;
+ for ($i = 0; $i < 40; $i++)
+ {
+ $diff |= ord($hmac[$i]) ^ ord($hmac_check[$i]);
+ }
+
+ if ($diff !== 0)
{
log_message('error', 'The session cookie data did not match what was expected.');
$this->sess_destroy();