V4V firewall (viptables) rules

Owned by Ross Philipson
Last updated: Jan 22, 2019 by Jason Andryuk
2 min read

Copyright 2016 by Assured Information Security, Inc. Created by Jean-Edouard Lejosne <lejosnej@ainfosec.com>. This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.


Location

V4V firewall rules for the different VM types (and their stubdoms) are defined in VM templates:

https://github.com/OpenXT/manager/tree/master/templates/default

Rule management

The toostack sets the default rule to REJECT.

Since there is no notion of connection state in the Xen V4V code, for each VMA → VMB:port, we have to define 2 ACCEPT rules:

  • VMA:* → VMB:port
  • VMB:port → VMA:*

Note: "*" can now be replaced with a pre-defined port (usually port + 10000) to make things safer.

When using a wildcard, if a malicious process in VMB manages to use "port" as its "from" port, then it can access all the VMA V4V services...

Rules

DOM0

  • can talk to UIVM and NDVM from port 12222 to port 2222
    used for: sshv4v
  • can talk to NDVM from port 15555 to port 5555
    used for: dbus (probably network-master talking to network-slave)

UIVM

NDVM

  • can talk to DOM0 on port 4878
    used for: icbinn
  • can talk to DOM0 on port 5555
    used for: dbus (network-slave talking to network-master?)

SYNCVM

  • can talk to DOM0 on port 4878
    used for: icbinn and vhd-util env var LIBVHD_ICBINN_VHD_SERVER
  • can talk to DOM0 on port 4879
    used for: vhd-util env var LIBVHD_ICBINN_KEY_SERVER
  • can talk to DOM0 on port 5556
    used for: dbus (sync-client-daemon issuing dbus commands to xenmgr)

Regular guests

Can't talk to anything

Stubdomains

  • can talk to DOM0 on port 4001
    used for: dmbus service 1

  • can talk to DOM0 on port 4002
    used for: dmbus service 2

  • can talk to DOM0 on port 5000
    used for: atapi_pt_helper

  • can talk to DOM0 on port 5001
    used for: audio_helper

  • can talk to DOM0 on port 5100
    used for: qmp_helper - proxy QEMU Machine Protocol (QMP) commands