--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/website/issues/extensions/timestamp.py	Fri Feb 06 13:16:31 2009 +0000
@@ -0,0 +1,28 @@
+import time, struct, base64
+from roundup.cgi.actions import RegisterAction
+from roundup.cgi.exceptions import *
+
+def timestamp():
+    return base64.encodestring(struct.pack("i", time.time())).strip()
+
+def unpack_timestamp(s):
+    return struct.unpack("i",base64.decodestring(s))[0]
+
+class Timestamped:
+    def check(self):
+        try:
+            created = unpack_timestamp(self.form['opaque'].value)
+        except KeyError:
+            raise FormError, "somebody tampered with the form"
+        if time.time() - created < 4:
+            raise FormError, "responding to the form too quickly"
+        return True
+
+class TimestampedRegister(Timestamped, RegisterAction):
+    def permission(self):
+        self.check()
+        RegisterAction.permission(self)
+
+def init(instance):
+    instance.registerUtil('timestamp', timestamp)
+    instance.registerAction('register', TimestampedRegister)