From: Anders Kaseorg <andersk@mit.edu>
Date: Fri, 13 Mar 2015 04:03:26 +0000 (-0400)
Subject: Remove quadratic-complexity keylogger from Konami easter egg
X-Git-Tag: 0.1.44~1
X-Git-Url: http://xvm.mit.edu/gitweb/invirt/packages/invirt-web.git/commitdiff_plain/2c11b1e0044eb9f74912f6cbd1b4c6bd3d50d294

Remove quadratic-complexity keylogger from Konami easter egg

Replace it with the obvious 10-state Knuth–Morris–Pratt FSM.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
---

diff --git a/code/static/nc.js b/code/static/nc.js
index 4ea168f..b82ed8b 100644
--- a/code/static/nc.js
+++ b/code/static/nc.js
@@ -1,9 +1,12 @@
-var kkeys = [], konami = "38,38,40,40,37,39,37,39,66,65";
+var konami = [38, 38, 40, 40, 37, 39, 37, 39, 66, 65],
+    konami_jump = [-1, 0, 1, 0, 0, 0, 0, 0, 0, 0],
+    konami_state = 0;
 document.onkeydown = function (e) {
-    kkeys.push(e.keyCode);
-    var idx = kkeys.toString().indexOf( konami );
-    if (idx >= 0 && idx != kkeys.toString().length - konami.length) {
-        kkeys = [];
-	window.location.assign("http://nyan.cat/");
+    while (konami_state != -1 && e.keyCode != konami[konami_state]) {
+        konami_state = konami_jump[konami_state];
+    }
+    if (++konami_state == konami.length) {
+        window.location.assign("http://nyan.cat/");
+        konami_state = 0;
     }
 };