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usegalaxy.eu local IP filter playbook

Ansible playbook for setting up the local IP filter on a host. For portability reasons, it uses firewalld(1) on Redhat-based systems; as of this writing this playbook is not implemented for Debian-based systems.

The firewall configuration created by this playbook distinguishes three zones:

  • A trusted zone: networks assigned to this zone are not subject to IP filtering, all traffic to/from these networks is accepted.

  • An internal zone: ingress traffic from networks assigned to this zone is accepted only for services that are explicitly whitelisted for it; egress traffic is unrestricted.

  • The public zone: applies to ingress traffic from any network that is not explicitly assigned to either the trusted or the internal zone. Only services whitelisted for the zone are allowed; egress traffic is unrestricted.

Configurable playbook variables

  • firewall_restart_daemon (default false): If true, restart firewalld as the last task in the playbook to activate the firewall configuration; otherwise a manual reload is required to actually activate the configuration.

  • firewall_ip_prefix_trusted (default is site-specific): A list of networks (in CIDR notation) that are assigned to the trusted zone.

  • firewall_ip_prefix_internal (default is site-specific): A list of networks (in CIDR notation) that are assigned to the internal zone.

  • firewall_internal_services (default [http, https, ssh]): The list of services whitelisted for the internal zone.

  • firewall_public_services (default: [http, https]): The list of services whitelisted for the public zone.

CAVEAT EMPTOR

An incoming IP packet will be matched by exactly one zone, based on the networks assigned to each zone, first match wins, with internal being matched before trusted and public (being bound to destination network interfaces rather than source networks) receiving whatever is not matched by any other zone.

THUS IT IS IMPORTANT THAT THE SUBNETS ASSIGNED TO THE ZONES BE ALL DISJUNCT!

It might appear logical to e.g. bind an organization's whole internal IP address space (say, 10.0.0.0/8) to the internal zone and the network where the service actually lives (e.g. 10.2.3.0/24) to trusted, but this is not how firewalld works! The source address 10.2.3.4 will be matched in internal, not in trusted (see above for why).

Likewise, if you intend the services whitelisted in internal to be a superset of those whitelisted in public, which is what you'll probably want, you have to list them all explicitly, the list for internal does not "inherit" from that of public. (See the variable documentation above for an example.)