Ubuntu Manpage: firehol.conf - FireHOL configuration

NAME

       firehol.conf - FireHOL configuration

DESCRIPTION

/etc/firehol/firehol.conf is the default configuration file for firehol(1). It defines the stateful
firewall that will be produced.

A configuration file starts with an optional version indicator which looks like this:

version 6

See firehol-version(1) for full details.

A configuration file contains one or more interface definitions, which look like this:

interface eth0 lan
client all accept # This host can access any remote service
server ssh accept # Remote hosts can access SSH on local server
# ...

The above definition has name “lan” and specifies a network interface (eth0). A definition may contain
zero or more subcommands. See firehol-interface(5) for full details.

By default FireHOL will try to create both IPv4 and IPv6 rules for each interface. To make this explicit
or restrict which rules are created write both interface, ipv4 interface or ipv6 interface.

Note that IPv6 will be disabled silently if your system is not configured to use it. You can test this
by looking for the file /proc/net/if_inet6. The IPv6 HOWTO (http://www.tldp.org/HOWTO/Linux+IPv6-HOW‐
TO/systemcheck-kernel.html) has more information.

A configuration file contains zero or more router definitions, which look like this:

DMZ_IF=eth0
WAN_IF=eth1
router wan2dmz inface ${WAN_IF} outface ${DMZ_IF}
route http accept # Hosts on WAN may access HTTP on hosts in DMZ
server ssh accept # Hosts on WAN may access SSH on hosts in DMZ
client pop3 accept # Hosts in DMZ may access POP3 on hosts on WAN
# ...

The above definition has name “wan2dmz” and specifies incoming and outgoing network interfaces (eth1 and
eth0) using variables. A definition may contain zero or more subcommands. Note that a router is not re‐
quired to specify network interfaces to operate on. See firehol-router(5) for full details.

By default FireHOL will try to create both IPv4 and IPv6 rules for each router. To make this explicit or
restrict which rules are created write both router, ipv4 router or ipv6 router.

It is simple to add extra service definitions which can then be used in the same way as those provided as
standard. See ADDING SERVICES.

The configuration file is parsed as a bash(1) script, allowing you to set up and use variables, flow con‐
trol and external commands.

Special control variables may be set up and used outside of any definition, see firehol-defaults.conf(5)
as can the functions in CONFIGURATION HELPER COMMANDS and HELPER COMMANDS.

VARIABLES AVAILABLE

       The  following  variables  are  made  available  in the FireHOL configuration file and can be accessed as
       ${VARIABLE}.

       UNROUTABLE_IPS
              This variable includes the IPs from both PRIVATE_IPS and RESERVED_IPS.  It is useful  to  restrict
              traffic on interfaces and routers accepting Internet traffic, for example:

                     interface eth0 internet src not "${UNROUTABLE_IPS}"

       PRIVATE_IPS
              This   variable   includes  all  the  IP  addresses  defined  as  Private  or  Test  by  RFC  3330
              (https://tools.ietf.org/html/rfc3330).

              You can override the default values by creating a file called /etc/firehol/PRIVATE_IPS.

       RESERVED_IPS
              This variable includes all the IP addresses defined by IANA (http://www.iana.org/) as reserved.

              You can override the default values by creating a file called /etc/firehol/RESERVED_IPS.

              Now that IPv4 address space has all been allocated there is very little  reason  that  this  value
              will need to change in future.

       MULTICAST_IPS
              This   variable   includes   all   the   IP   addresses   defined   as   Multicast   by  RFC  3330
              (https://tools.ietf.org/html/rfc3330).

              You can override the default values by creating a file called /etc/firehol/MULTICAST_IPS.

ADDING SERVICES

To define new services you add the appropriate lines before using them later in the configuration file.

The following are required:

server_myservice_ports=“proto/sports”

client_myservice_ports=“cports”

proto is anything iptables(8) accepts e.g. “tcp”, “udp”, “icmp”, including numeric protocol values.

sports is the ports the server is listening at. It is a space-separated list of port numbers, names and
ranges (from:to). The keyword any will match any server port.

cports is the ports the client may use to initiate a connection. It is a space-separated list of port
numbers, names and ranges (from:to). The keyword any will match any client port. The keyword default
will match default client ports. For the local machine (e.g. a client within an interface) it resolves
to sysctl(8) variable net.ipv4.ip_local_port_range (or /proc/sys/net/ipv4/ip_local_port_range). For a
remote machine (e.g. a client within an interface or anything in a router) it resolves to the variable
DEFAULT_CLIENT_PORTS (see firehol-defaults.conf(5)).

The following are optional:

require_myservice_modules=“modules”

require_myservice_nat_modules=“nat-modules”

The named kernel modules will be loaded when the definition is used. The NAT modules will only be loaded
if FIREHOL_NAT is non-zero (see firehol-defaults.conf(5)).

For example, for a service named daftnet that listens at two ports, port 1234 TCP and 1234 UDP where the
expected client ports are the default random ports a system may choose, plus the same port numbers the
server listens at, with further dynamic ports requiring kernel modules to be loaded:

# Setup service
server_daftnet_ports="tcp/1234 udp/1234"
client_daftnet_ports="default 1234"
require_daftnet_modules="ip_conntrack_daftnet"
require_daftnet_nat_modules="ip_nat_daftnet

interface eth0 lan0
server daftnet accept

interface eth1 lan1
client daftnet reject

router lan2lan inface eth0 outface eth1
route daftnet accept

Where multiple ports are provides (as per the example), FireHOL simply determines all of the combinations
of client and server ports and generates multiple iptables(8) statements to match them.

To create more complex rules, or stateless rules, you will need to create a bash function prefixed rules_
e.g. rules_myservice. The best reference is the many such functions in the main firehol(1) script.

When adding a service which uses modules, or via a custom function, you may also wish to include the fol‐
lowing:

ALL_SHOULD_ALSO_RUN=“${ALL_SHOULD_ALSO_RUN} myservice”

which will ensure your service is set-up correctly as part of the all service.

Note

To allow definitions to be shared you can instead create files and install them in the /etc/fire‐
hol/services directory with a .conf extension.

The first line must read:

#FHVER: 1:213

1 is the service definition API version. It will be changed if the API is ever modified. The 213
originally referred to a FireHOL 1.x minor version but is no longer checked.

FireHOL will refuse to run if the API version does not match the expected one.

DEFINITIONS

       • firehol-interface(5) - interface definition

       • firehol-router(5) - router definition

SUBCOMMANDS

       • firehol-policy(5) - policy command

       • firehol-protection(5) - protection command

       • firehol-server(5) - server, route commands

       • firehol-client(5) - client command

       • firehol-group(5) - group command

HELPER COMMANDS

       These helpers can be used in interface and router definitions as well as before them:

       • firehol-iptables(5) - iptables helper

       • firehol-masquerade(5) - masquerade helper

       This helper can be used in router definitions as well as before any router or interface:

       • firehol-tcpmss(5) - tcpmss helper

CONFIGURATION HELPER COMMANDS

       These  helpers should only be used outside of interface and router definitions (i.e. before the first in‐
       terface is defined).

       • firehol-version(5) - version config helper

       • firehol-action(5) - action config helper

       • firehol-blacklist(5) - blacklist config helper

       • firehol-classify(5) - classify config helper

       • firehol-connmark(5) - connmark config helper

       • firehol-dscp(5) - dscp config helper

       • firehol-mac(5) - mac config helper

       • firehol-mark(5) - mark config helper

       • firehol-nat(5) - nat, snat, dnat, redirect helpers

       • firehol-proxy(5) - transparent proxy/squid helpers

       • firehol-tos(5) - tos config helper

       • firehol-tosfix(5) - tosfix config helper

AUTHORS

       FireHOL Team.

FireHOL Reference                               Built 30 Mar 2024                                firehol.conf(5)