[Bug 1837252] Re: [OSSA-2019-004] Ageing time of 0 disables linuxbridge MAC learning (CVE-2019-15753)

[Sam Morrison]

** Also affects: cloud-archive
   Importance: Undecided
       Status: New

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Title:
  [OSSA-2019-004] Ageing time of 0 disables linuxbridge MAC learning
  (CVE-2019-15753)

Status in Ubuntu Cloud Archive:
  New
Status in neutron:
  Invalid
Status in OpenStack Compute (nova):
  Invalid
Status in os-vif:
  Fix Released
Status in os-vif stein series:
  Fix Committed
Status in os-vif trunk series:
  Fix Released
Status in OpenStack Security Advisory:
  Fix Released

Bug description:
  Release: OpenStack Stein
  Driver: LinuxBridge

  Using Stein w/ the LinuxBridge mech driver/agent, we have found that
  traffic is being flooded across bridges. Using tcpdump inside an
  instance, you can see unicast traffic for other instances.

  We have confirmed the macs table shows the aging timer set to 0 for
  permanent entries, and the bridge is NOT learning new MACs:

  root at lab-compute01:~# brctl showmacs brqd0084ac0-f7
  port no	mac addr		is local?	ageing timer
    5	24:be:05:a3:1f:e1	yes		   0.00
    5	24:be:05:a3:1f:e1	yes		   0.00
    1	fe:16:3e:02:62:18	yes		   0.00
    1	fe:16:3e:02:62:18	yes		   0.00
    7	fe:16:3e:07:65:47	yes		   0.00
    7	fe:16:3e:07:65:47	yes		   0.00
    4	fe:16:3e:1d:d6:33	yes		   0.00
    4	fe:16:3e:1d:d6:33	yes		   0.00
    9	fe:16:3e:2b:2f:f0	yes		   0.00
    9	fe:16:3e:2b:2f:f0	yes		   0.00
    8	fe:16:3e:3c:42:64	yes		   0.00
    8	fe:16:3e:3c:42:64	yes		   0.00
   10	fe:16:3e:5c:a6:6c	yes		   0.00
   10	fe:16:3e:5c:a6:6c	yes		   0.00
    2	fe:16:3e:86:9c:dd	yes		   0.00
    2	fe:16:3e:86:9c:dd	yes		   0.00
    6	fe:16:3e:91:9b:45	yes		   0.00
    6	fe:16:3e:91:9b:45	yes		   0.00
   11	fe:16:3e:b3:30:00	yes		   0.00
   11	fe:16:3e:b3:30:00	yes		   0.00
    3	fe:16:3e:dc:c3:3e	yes		   0.00
    3	fe:16:3e:dc:c3:3e	yes		   0.00

  root at lab-compute01:~# bridge fdb show | grep brqd0084ac0-f7
  01:00:5e:00:00:01 dev brqd0084ac0-f7 self permanent
  fe:16:3e:02:62:18 dev tap74af38f9-2e master brqd0084ac0-f7 permanent
  fe:16:3e:02:62:18 dev tap74af38f9-2e vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:86:9c:dd dev tapb00b3c18-b3 master brqd0084ac0-f7 permanent
  fe:16:3e:86:9c:dd dev tapb00b3c18-b3 vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:dc:c3:3e dev tap7284d235-2b master brqd0084ac0-f7 permanent
  fe:16:3e:dc:c3:3e dev tap7284d235-2b vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:1d:d6:33 dev tapbeb9441a-99 vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:1d:d6:33 dev tapbeb9441a-99 master brqd0084ac0-f7 permanent
  24:be:05:a3:1f:e1 dev eno1.102 vlan 1 master brqd0084ac0-f7 permanent
  24:be:05:a3:1f:e1 dev eno1.102 master brqd0084ac0-f7 permanent
  fe:16:3e:91:9b:45 dev tapc8ad2cec-90 master brqd0084ac0-f7 permanent
  fe:16:3e:91:9b:45 dev tapc8ad2cec-90 vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:07:65:47 dev tap86e2c412-24 master brqd0084ac0-f7 permanent
  fe:16:3e:07:65:47 dev tap86e2c412-24 vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:3c:42:64 dev tap37bcb70e-9e master brqd0084ac0-f7 permanent
  fe:16:3e:3c:42:64 dev tap37bcb70e-9e vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:2b:2f:f0 dev tap40f6be7c-2d vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:2b:2f:f0 dev tap40f6be7c-2d master brqd0084ac0-f7 permanent
  fe:16:3e:b3:30:00 dev tap6548bacb-c0 vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:b3:30:00 dev tap6548bacb-c0 master brqd0084ac0-f7 permanent
  fe:16:3e:5c:a6:6c dev tap61107236-1e vlan 1 master brqd0084ac0-f7 permanent
  fe:16:3e:5c:a6:6c dev tap61107236-1e master brqd0084ac0-f7 permanent

  The ageing time for the bridge is set to 0:

  root at lab-compute01:~# brctl showstp brqd0084ac0-f7
  brqd0084ac0-f7
   bridge id		8000.24be05a31fe1
   designated root	8000.24be05a31fe1
   root port		   0			path cost		   0
   max age		  20.00			bridge max age		  20.00
   hello time		   2.00			bridge hello time	   2.00
   forward delay		   0.00			bridge forward delay	   0.00
   ageing time		   0.00
   hello timer		   0.00			tcn timer		   0.00
   topology change timer	   0.00			gc timer		   0.00
   flags

  The default ageing time of 300 is being overridden by the value set
  here:

  Stein: https://github.com/openstack/os-
  vif/blob/stable/stein/os_vif/internal/command/ip/linux/impl_pyroute2.py#L89

  Master: https://github.com/openstack/os-
  vif/blob/master/os_vif/internal/ip/linux/impl_pyroute2.py#L89

  I am not sure of the behavior in OVS environments using the iptables
  firewall, but I have confirmed the 'qbr' bridges also have a ageing
  time of 0 (formerly 300).

  Please let me know if you have any questions.

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