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shorewall-nesting

NAME

Nesting - Shorewall Nested Zones

SYNOPSIS

child-zone[: parent-zone[, parent-zone]...]

DESCRIPTION

In shorewall-zones(5), a zone may be declared to be a sub-zone of one or more other zones using the above syntax.

Where zones are nested, the CONTINUE policy in shorewall-policy(5) allows hosts that are within multiple zones to be managed under the rules of all of these zones.

EXAMPLE

/etc/shorewall/zones:

         #ZONE    TYPE        OPTION
         fw       firewall
         net      ipv4
         sam:net  ipv4
         loc      ipv4
 

/etc/shorewall/interfaces:

         #ZONE     INTERFACE     BROADCAST     OPTIONS
         -         eth0          detect        dhcp,norfc1918
         loc       eth1          detect
 

/etc/shorewall/hosts:

         #ZONE     HOST(S)                     OPTIONS
         net       eth0:0.0.0.0/0
         sam       eth0:206.191.149.197
 

/etc/shorewall/policy:

         #SOURCE      DEST        POLICY       LOG LEVEL
         loc          net         ACCEPT
         sam          all         CONTINUE
         net          all         DROP         info
         all          all         REJECT       info
 

The second entry above says that when Sam is the client, connection requests should first be processed under rules where the source zone is sam and if there is no match then the connection request should be treated under rules where the source zone is net. It is important that this policy be listed BEFORE the next policy (net to all). You can have this policy generated for you automatically by using the IMPLICIT_CONTINUE option in shorewall.conf(5).

Partial /etc/shorewall/rules:

         #ACTION   SOURCE    DEST            PROTO    DEST PORT(S)
         ...
         DNAT      sam       loc:192.168.1.3 tcp      ssh
         DNAT      net       loc:192.168.1.5 tcp      www
         ...
 

Given these two rules, Sam can connect to the firewall's internet interface with ssh and the connection request will be forwarded to 192.168.1.3. Like all hosts in the net zone, Sam can connect to the firewall's internet interface on TCP port 80 and the connection request will be forwarded to 192.168.1.5. The order of the rules is not significant. Sometimes it is necessary to suppress port forwarding for a sub-zone. For example, suppose that all hosts can SSH to the firewall and be forwarded to 192.168.1.5 EXCEPT Sam. When Sam connects to the firewall's external IP, he should be connected to the firewall itself. Because of the way that Netfilter is constructed, this requires two rules as follows:

         #ACTION   SOURCE    DEST            PROTO    DEST PORT(S)
         ...
         ACCEPT+   sam       $FW             tcp      ssh
         DNAT      net       loc:192.168.1.3 tcp      ssh
         ...
 

The first rule allows Sam SSH access to the firewall. The second rule says that any clients from the net zone with the exception of those in the "sam" zone should have their connection port forwarded to 192.168.1.3. If you need to exclude more than one zone, simply use multiple ACCEPT+ rules. This technique also may be used when the ACTION is REDIRECT.

FILES

/etc/shorewall/zones

/etc/shorewall/interfaces

/etc/shorewall/hosts

/etc/shorewall/policy

/etc/shorewall/rules

SEE ALSO

shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall-interfaces(5), shorewall-ipsec(5), shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5), shorewall-netmap(5), shorewall-params(5), shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5), shorewall-route_rules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)