Add maximum lifetime of 30m on password recovery tokens

Fixes https://jira.coreos.com/browse/QS-80

data/model/user.py

@@ -508,19 +508,26 @@ def create_reset_password_email_code(email):
 
 
 def validate_reset_code(code):
+  # Find the reset code.
   try:
     code = EmailConfirmation.get(EmailConfirmation.code == code,
                                  EmailConfirmation.pw_reset == True)
   except EmailConfirmation.DoesNotExist:
     return None
 
+  # Make sure the code is not expired.
+  max_lifetime_duration = convert_to_timedelta(config.app_config['USER_RECOVERY_TOKEN_LIFETIME'])
+  if code.created + max_lifetime_duration < datetime.now():
+    code.delete_instance()
+    return None
+
+  # Verify the user and return the code.
   user = code.user
   if not user.verified:
     user.verified = True
     user.save()
 
   code.delete_instance()
-
   return user