Copyright © 2009, 2013 Thomas M. Eastep
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover, and with no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
2023/02/18
Table of Contents
There is sometimes a need to be able to define a zone whose members are unknown at compile-time. For example, you may wish to require authentication of internal users before allowing them access to the internet. When a user is authenticated, the user's IP address is added to the zone of users permitted web access.
Shorewall provides basic support for defining such zones. This support is based on ipset. Most current distributions have ipset, but you may need to install the xtables-addons package.
Prior to Shorewall 4.5.9, when multiple records for a zone appear in
/etc/shorewall/hosts, Shorewall would create a
separate ipset for each interface. This meant that an add or delete
command was required for each of the interface, when the address involved
was reachable via multiple interfaces.
Beginning with Shoreawll 4.5.9, it is possible to have a single ipset shared among all interfaces. This also simplifies management of dynamic zone contents for dynamic zones associated with only a single interface.
The earlier implementation described below is still available in these later releases.
A dynamic zone is defined by specifying the dynamic_shared option in the zones file and using the dynamic keyword in the hosts list.
/etc/shorewall/zones:
#NAME TYPE OPTIONS
net ipv4
rsyncok:loc ipv4 dynamic_shared/etc/shorewall/interfaces:
#ZONE INTERFACE BROADCAST OPTIONS loc eth0 - … loc eth1 - …
/etc/shorewall/hosts:
#ZONE HOSTS OPTIONS rsyncok eth0:dynamic rsyncok eth1:dynamic
When the dynamic_shared option is specified, a single ipset is created; the ipset has the same name as the zone.
In the above example, rsyncok is a sub-zone of the single zone loc. Making a dynamic zone a sub-zone of multiple other zones is also supported.
Adding a host to a dynamic zone is accomplished by adding the host's IP address to the appropriate ipset. Shorewall provldes a command for doing that:
shorewall add
zone address...
Example:
shorewall add rsyncok 70.90.191.124
Deleting a host from a dynamic zone is accomplished by removing the host's IP address from the appropriate ipset. Shorewall provldes a command for doing that:
shorewall delete
zoneaddress...
Example:
shorewall delete rsyncok 70.19.191.124
The command can only be used when the ipset involved is of type iphash. For other ipset types, the ipset command must be used directly.
When SAVE_IPSETS=Yes in shorewall.conf, the contents of a dynamic
zone survive shorewall stop/shorewall start and
shorewall restart. During shorewall
stop, the contents of the ipsets are saved in the file
${VARDIR}/ipsets.save (usually
/var/lib/shorewall/ipsets.save). During
shorewall start, the contents of that file are restored
to the sets. During both shorewall start and
shorewall restart, any new ipsets required as a result
of a configuration change are added.