Ubuntu Manpage: firehol - an easy to use but powerful iptables stateful firewall

NAME

       firehol - an easy to use but powerful iptables stateful firewall

SYNOPSIS

       firehol

       sudo -E firehol panic [ IP ]

       firehol command [ – conf-arg...  ]

       firehol CONFIGFILE [start|debug|try] [– conf-arg...  ]

DESCRIPTION

Running firehol invokes iptables(8) to manipulate your firewall.

Run without any arguments, firehol will present some help on usage.

When given CONFIGFILE, firehol will use the named file instead of
/etc/firehol/firehol.conf as its configuration. If no command is given, firehol assumes
try.

It is possible to pass arguments for use by the configuration file separating any conf-arg
values from the rest of the arguments with --. The arguments are accessible in the
configuration using standard bash(1) syntax e.g. $1, $2, etc.

PANIC
To block all communication, invoke firehol with the panic command.

FireHOL removes all rules from the running firewall and then DROPs all traffic on all
iptables(8) tables (mangle, nat, filter) and pre-defined chains (PREROUTING, INPUT,
FORWARD, OUTPUT, POSTROUTING).

DROPing is not done by changing the default policy to DROP, but by adding one rule per
table/chain to drop all traffic. This allows systems which do not reset all the chains to
ACCEPT when starting to function correctly.

When activating panic mode, FireHOL checks for the existence of the SSH_CLIENT shell
environment variable, which is set by ssh(1). If it finds this, then panic mode will
allow the established SSH connection specified in this variable to operate.

Note

In order for FireHOL to see the environment variable you must ensure that it is
preserved. For sudo(8) use the -E and for su(1) omit the - (minus sign).

If SSH_CLIENT is not set, the IP after the panic argument allows you to give an IP address
for which all established connections between the IP address and the host in panic will be
allowed to continue.

COMMANDS

start; restart
Activates the firewall using /etc/firehol/firehol.conf.

Use of the term restart is allowed for compatibility with common init
implementations.

try Activates the firewall, waiting for the user to type the word commit. If this word
is not typed within 30 seconds, the previous firewall is restored.

stop Stops a running iptables(8) firewall by clearing all of the tables and chains and
setting the default policies to ACCEPT. This will allow all traffic to pass
unchecked.

condrestart
Restarts the FireHOL firewall only if it is already active. This is the generally
expected behaviour (but opposite to FireHOL prior to 2.0.0-pre4).

status Shows the running firewall, using /sbin/iptables -nxvL | less.

save Start the firewall and then save it using iptables-save(8) to the location given by
FIREHOL_AUTOSAVE. See firehol-defaults.conf(5) for more information.

The required kernel modules are saved to an executable shell script
/var/spool/firehol/last_save_modules.sh, which can be called during boot if a
firewall is to be restored.

Note

External changes may cause a firewall restored after a reboot to not work as
intended where starting the firewall with FireHOL will work.

This is because as part of starting a firewall, FireHOL checks some
changeable values. For instance the current kernel configuration is checked
(for client port ranges), and RPC servers are queried (to allow correct
functioning of the NFS service).

debug Parses the configuration file but instead of activating it, FireHOL shows the
generated iptables(8) statements.

explain
Enters an interactive mode where FireHOL accepts normal configuration commands and
presents the generated iptables(8) commands for each of them, together with some
reasoning for its purpose.

Additionally, FireHOL automatically generates a configuration script based on the
successful commands given.

Some extra commands are available in explain mode.

help Present some help

show Present the generated configuration

quit Exit interactive mode and quit

helpme; wizard
Tries to guess the FireHOL configuration needed for the current machine.

FireHOL will not stop or alter the running firewall. The configuration file is
given in the standard output of firehol, thus firehol helpme > /tmp/firehol.conf
will produce the output in /tmp/firehol.conf.

The generated FireHOL configuration must be edited before use on your systems. You
are required to take a number of decisions; the comments in the generated file will
instruct you in the choices you must make.

FILES

       /etc/firehol/firehol.conf

AUTHORS

       FireHOL Team; Original man page by Marc Brockschmidt.