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UFW FRAMEWORK(8)		 October 2011		      UFW FRAMEWORK(8)

NAME
       ufw-framework - using the ufw framework

DESCRIPTION
       ufw provides both a command line interface and a framework for managing
       a netfilter firewall. While the ufw command provides  an	 easy  to  use
       interface  for  managing	 a  firewall,  the  ufw framework provides the
       administrator methods to customize default behavior and add  rules  not
       supported  by  the  command  line  tool. In this way, ufw can take full
       advantage of Linux netfilter's power and flexibility.

OVERVIEW
       The framework provides boot time initialization, rules files for adding
       custom  rules, a method for loading netfilter modules, configuration of
       kernel parameters and configuration of IPv6. The framework consists  of
       the following files:

       /lib/ufw/ufw-init
	      initialization script

       /etc/ufw/before.init
	      initialization  customization  script run before ufw is initial‐
	      ized

       /etc/ufw/after.init
	      initialization customization script run after ufw is initialized

       /etc/ufw/before[6].rules
	      rules file containing rules evaluated before UI added rules

       /lib/ufw/user[6].rules
	      rules file containing UI added rules (managed with the ufw  com‐
	      mand)

       /etc/ufw/after[6].rules
	      rules file containing rules evaluated after UI added rules

       /etc/default/ufw
	      high level configuration

       /etc/ufw/sysctl.conf
	      kernel network tunables

       /etc/ufw/ufw.conf
	      additional high level configuration

BOOT INITIALIZATION
       ufw  is	started on boot with /lib/ufw/ufw-init. This script is a stan‐
       dard SysV style initscript used by the ufw command and  should  not  be
       modified.  The /etc/before.init and /etc/after.init scripts may be used
       to perform any additional firewall configuration that is not  yet  sup‐
       ported  in  ufw	itself	and if they exist and are executable, ufw-init
       will execute these scripts. ufw-init supports the following arguments:

       start: loads the firewall

       stop:  unloads the firewall

       restart:
	      reloads the firewall

       force-reload:
	      same as restart

       status:
	      basic status of the firewall

       force-stop:
	      same as stop, except does not check if the firewall  is  already
	      loaded

       flush-all:
	      flushes the built-in chains, deletes all non-built-in chains and
	      resets the policy to ACCEPT

       ufw-init will call before.init and after.init with start, stop,	status
       and  flush-all,	but typically, if used, these scripts need only imple‐
       ment start and stop.

       ufw uses many user-defined chains in addition to the built-in  iptables
       chains. If MANAGE_BUILTINS in /etc/default/ufw is set to 'yes', on stop
       and reload the built-in chains are flushed. If it is set	 to  'no',  on
       stop  and  reload the ufw secondary chains are removed and the ufw pri‐
       mary chains are flushed. In  addition  to  flushing  the	 ufw  specific
       chains,	it  keeps the primary chains in the same order with respect to
       any other user-defined chains that may have been added. This allows for
       ufw to interoperate with other software that may manage their own fire‐
       wall rules.

       To ensure your firewall is loading on boot,  you	 must  integrate  this
       script into the boot process. Consult your distribution's documentation
       for the proper way to modify your boot process if ufw  is  not  already
       integrated.

RULES FILES
       ufw  is	in part a front-end for iptables-restore, with its rules saved
       in /etc/ufw/before.rules, /etc/ufw/after.rules and /lib/ufw/user.rules.
       Administrators  can  customize  before.rules and after.rules as desired
       using the standard iptables-restore syntax.   Rules  are	 evaluated  as
       follows:	 before.rules  first,  user.rules  next, and after.rules last.
       IPv6 rules are evaluated in the same way, with the  rules  files	 named
       before6.rules,  user6.rules and after6.rules. Please note that ufw sta‐
       tus only shows rules added with ufw and not  the	 rules	found  in  the
       /etc/ufw rules files.

       Important:  ufw only uses the *filter table by default. You may add any
       other tables such as *nat, *raw and *mangle as desired. For each	 table
       a corresponding COMMIT statement is required.

       After  modifying	 any of these files, you must reload ufw for the rules
       to take effect.	See the EXAMPLES section  for  common  uses  of	 these
       rules files.

MODULES
       Netfilter has many different connection tracking modules. These modules
       are aware of the underlying protocol and	 allow	the  administrator  to
       simplify	 his  or her rule sets. You can adjust which netfilter modules
       to load by adjusting IPT_MODULES in /etc/default/ufw. Some popular mod‐
       ules to load are:

	 nf_conntrack_ftp
	 nf_nat_ftp
	 nf_conntrack_irc
	 nf_nat_irc
	 nf_conntrack_netbios_ns
	 nf_conntrack_pptp
	 nf_conntrack_tftp
	 nf_nat_tftp

KERNEL PARAMETERS
       ufw  will  read	in  /etc/ufw/sysctl.conf on boot when enabled.	Please
       note  that  /etc/ufw/sysctl.conf	 overrides  values   in	  the	system
       systcl.conf  (usually  /etc/sysctl.conf). Administrators can change the
       file used by modifying /etc/default/ufw.

IPV6
       IPv6 is enabled by default. When disabled, all incoming,	 outgoing  and
       forwarded  packets  are	dropped,  with the exception of traffic on the
       loopback interface.  To adjust this behavior,  set  IPV6	 to  'yes'  in
       /etc/default/ufw. See the ufw manual page for details.

EXAMPLES
       As  mentioned,  ufw  loads its rules files into the kernel by using the
       iptables-restore and ip6tables-restore commands. Users wanting  to  add
       rules  to  the  ufw rules files manually must be familiar with these as
       well as the iptables and ip6tables  commands.  Below  are  some	common
       examples	 of  using the ufw rules files.	 All examples assume IPv4 only
       and that DEFAULT_FORWARD_POLICY in /etc/default/ufw is set to DROP.

   IP Masquerading
       To allow IP masquerading for computers from the 10.0.0.0/8  network  on
       eth1 to share the single IP address on eth0:

       Edit /etc/ufw/sysctl.conf to have:
	       net.ipv4.ip_forward=1

       Add to the end of /etc/ufw/before.rules, after the *filter section:
	       *nat
	       :POSTROUTING ACCEPT [0:0]
	       -A POSTROUTING -s 10.0.0.0/8 -o eth0 -j MASQUERADE
	       COMMIT

       If  your	 firewall is using IPv6 tunnels or 6to4 and is also doing NAT,
       then you should not usually masquerade protocol	'41'  (ipv6)  packets.
       For  example,  instead  of  the	above,	/etc/ufw/before.rules  can  be
       adjusted to have:
	       *nat
	       :POSTROUTING ACCEPT [0:0]
	       -A POSTROUTING -s 10.0.0.0/8 --protocol ! 41 -o	eth0  -j  MAS‐
	      QUERADE
	       COMMIT

       Add the ufw route to allow the traffic:
	       ufw route allow in on eth1 out on eth0 from 10.0.0.0/8

   Port Redirections
       To forward tcp port 80 on eth0 to go to the webserver at 10.0.0.2:

       Edit /etc/ufw/sysctl.conf to have:
	       net.ipv4.ip_forward=1

       Add to the end of /etc/ufw/before.rules, after the *filter section:
	       *nat
	       :PREROUTING ACCEPT [0:0]
	       -A PREROUTING -p tcp -i eth0 --dport 80 -j DNAT \
		 --to-destination 10.0.0.2:80
	       COMMIT

       Add the ufw route rule to allow the traffic:
	       ufw route allow in on eth0 to 10.0.0.2 port 80 proto tcp

   Egress filtering
       To block RFC1918 addresses going out of eth0:

       Add the ufw route rules to reject the traffic:
	       ufw route reject out on eth0 to 10.0.0.0/8
	       ufw route reject out on eth0 to 172.16.0.0/12
	       ufw route reject out on eth0 to 192.168.0.0/16

   Full example
       This  example  combines	the  other  examples and demonstrates a simple
       routing firewall. Warning: this setup is only an example to demonstrate
       the  functionality  of the ufw framework in a concise and simple manner
       and should not be used in production without  understanding  what  each
       part  does  and	does not do. Your firewall will undoubtedly want to be
       less open.

       This router/firewall has two interfaces:	 eth0  (Internet  facing)  and
       eth1  (internal LAN). Internal clients have addresses on the 10.0.0.0/8
       network and should be able to connect to anywhere on the Internet. Con‐
       nections	 to port 80 from the Internet should be forwarded to 10.0.0.2.
       Access to ssh port 22 from the administrative workstation  (10.0.0.100)
       to  this	 machine should be allowed. Also make sure no internal traffic
       goes to the Internet.

       Edit /etc/ufw/sysctl.conf to have:
		net.ipv4.ip_forward=1

       Add to the end of /etc/ufw/before.rules, after the *filter section:
	       *nat
	       :PREROUTING ACCEPT [0:0]
	       :POSTROUTING ACCEPT [0:0]
	       -A PREROUTING -p tcp -i eth0 --dport 80 -j DNAT \
		 --to-destination 10.0.0.2:80
	       -A POSTROUTING -s 10.0.0.0/8 -o eth0 -j MASQUERADE
	       COMMIT

       Add the necessary ufw rules:
	       ufw route reject out on eth0 to 10.0.0.0/8
	       ufw route reject out on eth0 to 172.16.0.0/12
	       ufw route reject out on eth0 to 192.168.0.0/16
	       ufw route allow in on eth1 out on eth0 from 10.0.0.0/8
	       ufw route allow in on eth0 to 10.0.0.2 port 80 proto tcp
	       ufw allow in on eth1 from 10.0.0.100 to any port 22 proto tcp

SEE ALSO
       ufw(8),	    iptables(8),      ip6tables(8),	  iptables-restore(8),
       ip6tables-restore(8), sysctl(8), sysctl.conf(5)

AUTHOR
       ufw is Copyright 2008-2014, Canonical Ltd.

       ufw  and	 this  manual  page was originally written by Jamie Strandboge
       <jamie@canonical.com>

October 2011						      UFW FRAMEWORK(8)
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