Security Group doesn't work if the specific allowed-address-pairs value is set

It's a customer-found issue. The issue is reproducible on MOS 10.0 as well.

Summary:

Security Group doesn't work if the specific allowed-address-pairs value is set to the port associated with it.

High level description:

OpenStack user is allowed to specify arbitrary mac_address/ip_address pairs that are allowed to pass through a port. For some practical reasons, OpenStack users can specify huge subnets, and CIRDs provided there are not sanitized. If the CIRD provided with 'allowed-address-pairs' for any single port associated with Security Group overlaps with a subnet used by the VM, the VM is always accessible by any port and any protocol, despite the fact that its security group denies all ingress traffic.

Step-by-step reproduction process:

1) Create a VM in OpenStack
2) Check that there are no rules allowing icmp (for instance) in the security group associated with the VM
3) perform:
neutron port-update [any-port-associated-with-the-secgroup] --allowed-address-pairs type=dict list=true ip_address=[a-very-huge-cidr]

if your VM uses a private IPv4 address from networks 192.168.x or 172.16.x, then 128.0.0.0/1 will work as "a-very-huge-cidr", if it uses 10.x network then 0.0.0.0/1 should.

4) ping all the VMs in this secgroup successfully (from router namespace, or from any host which is allowed to access floating IPs if floating IP is also assigned to the VM), as well as access it by any port and protocol which the VM is listening.

Version:

All OpenStack releases up to Mitaka.

Perceived severity:

It's not a blocker as workaround are pretty obvious, but it's a huge security bug: all the network security provided by Security Groups might be ruined easily, just by updating a single port in neutron.

If we restrict the value of allowed-address-pairs in neutron to a single address (/32 or /128), might it break anything?

Upstream bug: https://bugs.launchpad.net/neutron/+bug/1622654