IP Options are evil – drop them , drop them on Cisco Asa/IOS Microsoft ISA Juniper or Checkpoint

As you probably noticed IP header has variable length placeholder for the IP Options field. It has been there since the beginning , once a good idea for debug now turned into trouble. RFC 791 states that hosts/routers supporting IP protocol must implement Ip Options filed . It is up to the vendor to decide what to do with this optional field, but it must understand it. Still, wouldn’t be a problem if not modern architecture of the routing equipment that was designed to do most efficiently Routing , i.e. pass from interface to interface gigabytes of traffic. Therefore routing functions are highly optimized and most of the time are implemented in hardware . All other types of traffic unfortunately are not, and in most of the cases processing , lets call it Control traffic, is being left to poor router CPU and done in software. That brought the troubles into the IP world – relatively small amounts of control traffic (including Ip Options packets) may bring down otherwise
powerful router in just minutes.
To prevent this attack vendors implemented protection measures to drop entirely or selectively IP packets that has Ip Options filed set. Below is quick cheat sheet how to do it in some gear :

Checkpoint firewall NG/NGX – packets with Ip Options are dropped by default except for the “Router Alert” option (0×94) for the IGMPv2 and PIM protocols [or so CP claim, will have to verify later] and not even logged. To start logging dropped packets go to Policy -> Global Properties -> Log and Alerts -> check Ip dropped packets : Log

There is a value related to it that is on by default : Global Properties -> SmartDashboard customization -> Advanced Configuration -> Configure -> Firewall 1 -> Stateful inspection -> enable_ip_options (check/uncheck) but unchecking it removes from firewall VM chain module that inspects these Options at all and all Ip Options packets are dropped . So all packets bearing Ip Options are happily dropped even before security rules , here:

Also Checkpoint say you can decide which Ip Options will be allowed later BUT only when installing the firewall: “The set of permitted options must be configured during installation … the enable_ip_options setting in SmartDashboard is then used to enable or disable this functionality. Contact Check Point support for instructions on configuring the set of allowed IP options.”

firewall {
    family inet {
        filter NOICMP {
            term 1 {
                from {
                    address {
                        192.168.2.100/32;
                    }
                }
                then {
                    reject;
                }
            }
            term 2 {
                from {
                    ip-options route-record;
                }
                then {
                    reject;
                }
            }
            term 3 {
                from {
                    address {
                        192.168.2.0/24;
                    }
                }
                then accept;
            }
        }
    }
}

Apply to the interface:

interfaces {
    em0 {
        unit 0 {
            enable;
            family inet {
                filter {
                    input NOICMP;
                }
                address 192.168.2.133/24;
            }
        }
    }

Other possible arguments to ip-options clause:

Possible completions:

<range>              Range of values
  [                    Open a set of values
  any                  Any IP option
  loose-source-route   Loose source route
  route-record         Route record
  router-alert         Router alert
  security             Security
  stream-id            Stream ID
  strict-source-route  Strict source route
  timestamp            Timestamp