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As another potential intermediate triage to this, we have added another
spoofing rule to the spoof chains and call the spoof chain in the
ingress rules. Effectively, if the DST IP address isn't the address we
assigned to the VM, then drop it.

In this scenario, the malicious VM can can still poison the ARP cache
and effectively DoS the victim, but it shouldn't be able to see any of
the victim's traffic as the packets headed to the malicious VM will get
dropped at the hypervisor.

I've attached a patch to the iptables_firewall.py from stable/havana
which implements this. If folks don't disagree with this approach I'll
submit the patch to be reviewed as well as look into getting it into
icehouse (or maybe Juno, depending on if it's considered a new feature
or bug fix).

** Patch added: "iptables_firewall.py.patch"
   https://bugs.launchpad.net/neutron/+bug/1274034/+attachment/4045291/+files/iptables_firewall.py.patch

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https://bugs.launchpad.net/bugs/1274034

Title:
  Neutron firewall anti-spoofing does not prevent ARP poisoning

Status in OpenStack Neutron (virtual network service):
  Triaged
Status in OpenStack Security Advisories:
  Invalid

Bug description:
  The neutron firewall driver 'iptabes_firawall' does not prevent ARP cache poisoning.
  When anti-spoofing rules are handled by Nova, a list of rules was added through the libvirt network filter feature:
  - no-mac-spoofing
  - no-ip-spoofing
  - no-arp-spoofing
  - nova-no-nd-reflection
  - allow-dhcp-server

  Actually, the neutron firewall driver 'iptabes_firawall' handles only
  MAC and IP anti-spoofing rules.

  This is a security vulnerability, especially on shared networks.

  Reproduce an ARP cache poisoning and man in the middle:
  - Create a private network/subnet 10.0.0.0/24
  - Start 2 VM attached to that private network (VM1: IP 10.0.0.3, VM2: 10.0.0.4)
  - Log on VM1 and install ettercap [1]
  - Launch command: 'ettercap -T -w dump -M ARP /10.0.0.4/ // output:'
  - Log on too on VM2 (with VNC/spice console) and ping google.fr => ping is ok
  - Go back on VM1, and see the VM2's ping to google.fr going to the VM1 instead to be send directly to the network gateway and forwarded by the VM1 to the gw. The ICMP capture looks something like that [2]
  - Go back to VM2 and check the ARP table => the MAC address associated to the GW is the MAC address of VM1

  [1] http://ettercap.github.io/ettercap/
  [2] http://paste.openstack.org/show/62112/

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