From 3f21cbba86e4a8ed209ade3e345f6a92a5e579d8 Mon Sep 17 00:00:00 2001
From: foo <foo@mafoo.org.uk>
Date: Wed, 8 May 2013 20:42:22 +0100
Subject: [PATCH] verify() on time allows one window either side

---
 lib/totp.php | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/totp.php b/lib/totp.php
index 10a1f42..26a8814 100644
--- a/lib/totp.php
+++ b/lib/totp.php
@@ -77,7 +77,13 @@ public function now() {
     public function verify($otp, $timestamp = null) {
       if($timestamp === null)
         $timestamp = time();
-      return ($otp == $this->at($timestamp));
+
+      $window = 30;
+      foreach (array(0, $window, -$window) as $t) 
+	if($otp == $this->at($timestamp + $t))
+	  return true;
+      
+      return false;
     }
 
     /**