File: //snap/ufw/current/docs/ufw
UFW:(8) May 2023 UFW:(8)
NAME
ufw - program for managing a netfilter firewall
DESCRIPTION
This program is for managing a Linux firewall and aims to provide an
easy to use interface for the user.
USAGE
ufw [--dry-run] enable|disable|reload
ufw [--dry-run] default allow|deny|reject [incoming|outgoing|routed]
ufw [--dry-run] logging on|off|LEVEL
ufw [--dry-run] reset
ufw [--dry-run] status [verbose|numbered]
ufw [--dry-run] show REPORT
ufw [--dry-run] [delete] [insert NUM] [prepend] allow|deny|reject|limit
[in|out] [log|log-all] [ PORT[/PROTOCOL] | APPNAME ] [comment COMMENT]
ufw [--dry-run] [rule] [delete] [insert NUM] [prepend]
allow|deny|reject|limit [in|out [on INTERFACE]] [log|log-all] [proto
PROTOCOL] [from ADDRESS [port PORT | app APPNAME ]] [to ADDRESS [port
PORT | app APPNAME ]] [comment COMMENT]
ufw [--dry-run] route [delete] [insert NUM] [prepend]
allow|deny|reject|limit [in|out on INTERFACE] [log|log-all] [proto PRO-
TOCOL] [from ADDRESS [port PORT | app APPNAME]] [to ADDRESS [port PORT
| app APPNAME]] [comment COMMENT]
ufw [--dry-run] [--force] delete NUM
ufw [--dry-run] app list|info|default|update
OPTIONS
--version
show program's version number and exit
-h, --help
show help message and exit
--dry-run
don't modify anything, just show the changes
enable reloads firewall and enables firewall on boot.
disable
unloads firewall and disables firewall on boot
reload reloads firewall
default allow|deny|reject DIRECTION
change the default policy for traffic going DIRECTION, where
DIRECTION is one of incoming, outgoing or routed. Note that
existing rules will have to be migrated manually when changing
the default policy. See RULE SYNTAX for more on deny and reject.
logging on|off|LEVEL
toggle logging. Logged packets use the LOG_KERN syslog facility.
Systems configured for rsyslog support may also log to
/var/log/ufw.log. Specifying a LEVEL turns logging on for the
specified LEVEL. The default log level is 'low'. See LOGGING
for details.
reset Disables and resets firewall to installation defaults. Can also
give the --force option to perform the reset without confirma-
tion.
status show status of firewall and ufw managed rules. Use status ver-
bose for extra information. In the status output, 'Anywhere' is
synonymous with 'any', 0.0.0.0/0 (IPv4) and ::/0 (IPv6). Note
that when using status, there is a subtle difference when
reporting interfaces. For example, if the following rules are
added:
ufw allow in on eth0 from 192.168.0.0/16
ufw allow out on eth1 to 10.0.0.0/8
ufw route allow in on eth0 out on eth1 to 10.0.0.0/8 from
192.168.0.0/16
ufw limit 2222/tcp comment 'SSH port'
ufw status will output:
To Action From
-- ------ ----
Anywhere on eth0 ALLOW 192.168.0.0/16
10.0.0.0/8 ALLOW OUT Anywhere on eth1
10.0.0.0/8 on eth1 ALLOW FWD 192.168.0.0/16 on eth0
Anywhere LIMIT Anywhere
# SSH port
For the input and output rules, the interface is reported rela-
tive to the firewall system as an endpoint, whereas with route
rules, the interface is reported relative to the direction pack-
ets flow through the firewall.
show REPORT
display information about the running firewall. See REPORTS
allow ARGS
add allow rule. See RULE SYNTAX
deny ARGS
add deny rule. See RULE SYNTAX
reject ARGS
add reject rule. See RULE SYNTAX
limit ARGS
add limit rule. See RULE SYNTAX
delete RULE|NUM
deletes the corresponding RULE
insert NUM RULE
insert the corresponding RULE as rule number NUM
prepend RULE
prepend the corresponding RULE to the top of the ruleset
RULE SYNTAX
Users can specify rules using either a simple syntax or a full syntax.
The simple syntax only specifies the port and optionally the protocol
to be allowed or denied on the host.
Both syntaxes support specifying a comment for the rule. For existing
rules, specifying a different comment updates the comment and specify-
ing '' removes the comment (note, 'insert' and 'prepend' cannot be used
to update the comment).
Example rules using the simple syntax:
ufw allow 53
This rule will allow tcp and udp port 53 to any address on this host.
To specify a protocol, append '/protocol' to the port. For example:
ufw allow 25/tcp
This will allow tcp port 25 to any address on this host. ufw will also
check /etc/services for the port and protocol if specifying a service
by name. Eg:
ufw allow smtp
ufw supports both ingress and egress filtering and users may optionally
specify a direction of either in or out for either incoming or outgoing
traffic. If no direction is supplied, the rule applies to incoming
traffic. Eg:
ufw allow in http
ufw reject out smtp
ufw reject telnet comment 'telnet is unencrypted'
Users can also use a fuller syntax, specifying the source and destina-
tion addresses and ports. This syntax is loosely based on OpenBSD's PF
syntax. For example:
ufw deny proto tcp to any port 80
This will deny all traffic to tcp port 80 on this host. Another exam-
ple:
ufw deny proto tcp from 10.0.0.0/8 to 192.168.0.1 port 25
This will deny all traffic from the RFC1918 Class A network to tcp port
25 with the address 192.168.0.1.
ufw deny proto tcp from 2001:db8::/32 to any port 25
This will deny all traffic from the IPv6 2001:db8::/32 to tcp port 25
on this host. IPv6 must be enabled in #CONFIG_PREFIX#/default/ufw for
IPv6 firewalling to work.
ufw deny in on eth0 to 224.0.0.1 proto igmp
This will deny all igmp traffic to 224.0.0.1 on the eth0 interface.
ufw allow in on eth0 to 192.168.0.1 proto gre
This will allow all gre traffic to 192.168.0.1 on the eth0 interface.
ufw allow proto tcp from any to any port 80,443,8080:8090 comment
'web app'
The above will allow all traffic to tcp ports 80, 443 and 8080-8090
inclusive and adds a comment for the rule. When specifying multiple
ports, the ports list must be numeric, cannot contain spaces and must
be modified as a whole. Eg, in the above example you cannot later try
to delete just the '443' port. You cannot specify more than 15 ports
(ranges count as 2 ports, so the port count in the above example is 4).
ufw supports several different protocols. The following are valid in
any rule and enabled when the protocol is not specified:
tcp
udp
The following have certain restrictions and are not enabled when the
protocol is not specified:
ah valid without port number
esp valid without port number
gre valid without port number
vrrp valid without port number
ipv6 valid for IPv4 addresses and without port number
igmp valid for IPv4 addresses and without port number
Rules for traffic not destined for the host itself but instead for
traffic that should be routed/forwarded through the firewall should
specify the route keyword before the rule (routing rules differ signif-
icantly from PF syntax and instead take into account netfilter FORWARD
chain conventions). For example:
ufw route allow in on eth1 out on eth2
This will allow all traffic routed to eth2 and coming in on eth1 to
traverse the firewall.
ufw route allow in on eth0 out on eth1 to 12.34.45.67 port 80 proto
tcp
This rule allows any packets coming in on eth0 to traverse the firewall
out on eth1 to tcp port 80 on 12.34.45.67.
In addition to routing rules and policy, you must also setup IP for-
warding. This may be done by setting the following in #CONFIG_PRE-
FIX#/ufw/sysctl.conf:
net/ipv4/ip_forward=1
net/ipv6/conf/default/forwarding=1
net/ipv6/conf/all/forwarding=1
then restarting the firewall:
ufw disable
ufw enable
Be aware that setting kernel tunables is operating system specific and
ufw sysctl settings may be overridden. See the sysctl manual page for
details.
ufw supports connection rate limiting, which is useful for protecting
against brute-force login attacks. When a limit rule is used, ufw will
normally allow the connection but will deny connections if an IP
address attempts to initiate 6 or more connections within 30 seconds.
See http://www.debian-administration.org/articles/187 for details. Typ-
ical usage is:
ufw limit ssh/tcp
Sometimes it is desirable to let the sender know when traffic is being
denied, rather than simply ignoring it. In these cases, use reject
instead of deny. For example:
ufw reject auth
By default, ufw will apply rules to all available interfaces. To limit
this, specify DIRECTION on INTERFACE, where DIRECTION is one of in or
out (interface aliases are not supported). For example, to allow all
new incoming http connections on eth0, use:
ufw allow in on eth0 to any port 80 proto tcp
To delete a rule, simply prefix the original rule with delete with or
without the rule comment. For example, if the original rule was:
ufw deny 80/tcp
Use this to delete it:
ufw delete deny 80/tcp
You may also specify the rule by NUM, as seen in the status numbered
output. For example, if you want to delete rule number '3', use:
ufw delete 3
If you have IPv6 enabled and are deleting a generic rule that applies
to both IPv4 and IPv6 (eg 'ufw allow 22/tcp'), deleting by rule number
will delete only the specified rule. To delete both with one command,
prefix the original rule with delete.
To insert a rule, specify the new rule as normal, but prefix the rule
with the rule number to insert. For example, if you have four rules,
and you want to insert a new rule as rule number three, use:
ufw insert 3 deny to any port 22 from 10.0.0.135 proto tcp
Similarly, to add a rule before all other rules matching the rule's IP
type, use the prepend rule:
ufw prepend deny from 1.2.3.4
This is particularly useful for dynamic firewalls as found in an IPS.
Importantly, if the specified rule is an IPv4 rule, it will be
prepended before all other IPv4 rules. If it is an IPv6 rule, it will
be prepended before any IPv6 rules.
To see a list of numbered rules, use:
ufw status numbered
ufw supports per rule logging. By default, no logging is performed when
a packet matches a rule. Specifying log will log all new connections
matching the rule, and log-all will log all packets matching the rule.
For example, to allow and log all new ssh connections, use:
ufw allow log 22/tcp
See LOGGING for more information on logging.
EXAMPLES
Deny all access to port 53:
ufw deny 53
Allow all access to tcp port 80:
ufw allow 80/tcp
Allow all access from RFC1918 networks to this host:
ufw allow from 10.0.0.0/8
ufw allow from 172.16.0.0/12
ufw allow from 192.168.0.0/16
Deny access to udp port 514 from host 1.2.3.4:
ufw deny proto udp from 1.2.3.4 to any port 514
Allow access to udp 1.2.3.4 port 5469 from 1.2.3.5 port 5469:
ufw allow proto udp from 1.2.3.5 port 5469 to 1.2.3.4 port 5469
REMOTE MANAGEMENT
When running ufw enable or starting ufw via its initscript, ufw will
flush its chains. This is required so ufw can maintain a consistent
state, but it may drop existing connections (eg ssh). ufw does support
adding rules before enabling the firewall, so administrators can do:
ufw allow proto tcp from any to any port 22
before running 'ufw enable'. The rules will still be flushed, but the
ssh port will be open after enabling the firewall. Please note that
once ufw is 'enabled', ufw will not flush the chains when adding or
removing rules (but will when modifying a rule or changing the default
policy). By default, ufw will prompt when enabling the firewall while
running under ssh. This can be disabled by using 'ufw --force enable'.
APPLICATION INTEGRATION
ufw supports application integration by reading profiles located in
#CONFIG_PREFIX#/ufw/applications.d. To list the names of application
profiles known to ufw, use:
ufw app list
Users can specify an application name when adding a rule (quoting any
profile names with spaces). For example, when using the simple syntax,
users can use:
ufw allow <name>
Or for the extended syntax:
ufw allow from 192.168.0.0/16 to any app <name>
You should not specify the protocol with either syntax, and with the
extended syntax, use app in place of the port clause.
Details on the firewall profile for a given application can be seen
with:
ufw app info <name>
where '<name>' is one of the applications seen with the app list com-
mand. Users may also specify all to see the profiles for all known
applications.
Syntax for the application profiles is a simple .INI format:
[<name>]
title=<title>
description=<description>
ports=<ports>
The 'ports' field may specify a '|'-separated list of ports/protocols
where the protocol is optional. A comma-separated list or a range
(specified with 'start:end') may also be used to specify multiple
ports, in which case the protocol is required. For example:
[SomeService]
title=Some title
description=Some description
ports=12/udp|34|56,78:90/tcp
In the above example, 'SomeService' may be used in app rules and it
specifies UDP port 12, TCP and UDP on port 34 and TCP ports 56 and
78-90 inclusive.
After creating or editing an application profile, users can run:
ufw app update <name>
This command will automatically update the firewall with updated pro-
file information. If specify 'all' for name, then all the profiles will
be updated. To update a profile and add a new rule to the firewall
automatically, users can run:
ufw app update --add-new <name>
The behavior of the update --add-new command can be configured using:
ufw app default <policy>
The default application policy is skip, which means that the update
--add-new command will do nothing. Users may also specify a policy of
allow or deny so the update --add-new command may automatically update
the firewall. WARNING: it may be a security to risk to use a default
allow policy for application profiles. Carefully consider the security
ramifications before using a default allow policy.
LOGGING
ufw supports multiple logging levels. ufw defaults to a loglevel of
'low' when a loglevel is not specified. Users may specify a loglevel
with:
ufw logging LEVEL
LEVEL may be 'off', 'low', 'medium', 'high' and 'full'. Log levels are
defined as:
off disables ufw managed logging
low logs all blocked packets not matching the defined policy (with
rate limiting), as well as packets matching logged rules
medium log level low, plus all allowed packets not matching the defined
policy, all INVALID packets, and all new connections. All log-
ging is done with rate limiting.
high log level medium (without rate limiting), plus all packets with
rate limiting
full log level high without rate limiting
Loglevels above medium generate a lot of logging output, and may
quickly fill up your disk. Loglevel medium may generate a lot of log-
ging output on a busy system.
Specifying 'on' simply enables logging at log level 'low' if logging is
currently not enabled.
REPORTS
The following reports are supported. Each is based on the live system
and with the exception of the listening report, is in raw iptables for-
mat:
raw
builtins
before-rules
user-rules
after-rules
logging-rules
listening
added
The raw report shows the complete firewall, while the others show a
subset of what is in the raw report.
The listening report will display the ports on the live system in the
listening state for tcp and the open state for udp, along with the
address of the interface and the executable listening on the port. An
'*' is used in place of the address of the interface when the exe-
cutable is bound to all interfaces on that port. Following this infor-
mation is a list of rules which may affect connections on this port.
The rules are listed in the order they are evaluated by the kernel, and
the first match wins. Please note that the default policy is not listed
and tcp6 and udp6 are shown only if IPV6 is enabled.
The added report displays the list of rules as they were added on the
command-line. This report does not show the status of the running fire-
wall (use 'ufw status' instead). Because rules are normalized by ufw,
rules may look different than the originally added rule. Also, ufw does
not record command ordering, so an equivalent ordering is used which
lists IPv6-only rules after other rules.
NOTES
On installation, ufw is disabled with a default incoming policy of
deny, a default forward policy of deny, and a default outgoing policy
of allow, with stateful tracking for NEW connections for incoming and
forwarded connections. In addition to the above, a default ruleset is
put in place that does the following:
- DROP packets with RH0 headers
- DROP INVALID packets
- ACCEPT certain icmp packets (INPUT and FORWARD): destination-unreach-
able, source-quench, time-exceeded, parameter-problem, and echo-request
for IPv4. destination-unreachable, packet-too-big, time-exceeded,
parameter-problem, and echo-request for IPv6.
- ACCEPT icmpv6 packets for stateless autoconfiguration (INPUT)
- ACCEPT ping replies from IPv6 link-local (ffe8::/10) addresses
(INPUT)
- ACCEPT DHCP client traffic (INPUT)
- DROP non-local traffic (INPUT)
- ACCEPT mDNS (zeroconf/bonjour/avahi 224.0.0.251 for IPv4 and ff02::fb
for IPv6) for service discovery (INPUT)
- ACCEPT UPnP (239.255.255.250 for IPv4 and ff02::f for IPv6) for ser-
vice discovery (INPUT)
Rule ordering is important and the first match wins. Therefore when
adding rules, add the more specific rules first with more general rules
later.
ufw is not intended to provide complete firewall functionality via its
command interface, but instead provides an easy way to add or remove
simple rules.
The status command shows basic information about the state of the fire-
wall, as well as rules managed via the ufw command. It does not show
rules from the rules files in #CONFIG_PREFIX#/ufw. To see the complete
state of the firewall, users can ufw show raw. This displays the fil-
ter, nat, mangle and raw tables using:
iptables -n -L -v -x -t <table>
ip6tables -n -L -v -x -t <table>
See the iptables and ip6tables documentation for more details.
If the default policy is set to REJECT, ufw may interfere with rules
added outside of the ufw framework. See README for details.
IPV6 is allowed by default. To change this behavior to only accept IPv6
traffic on the loopback interface, set IPV6 to 'no' in #CONFIG_PRE-
FIX#/default/ufw and reload ufw. When IPv6 is enabled, you may specify
rules in the same way as for IPv4 rules, and they will be displayed
with ufw status. Rules that match both IPv4 and IPv6 addresses apply to
both IP versions. For example, when IPv6 is enabled, the following rule
will allow access to port 22 for both IPv4 and IPv6 traffic:
ufw allow 22
IPv6 over IPv4 tunnels and 6to4 are supported by using the 'ipv6' pro-
tocol ('41'). This protocol can only be used with the full syntax. For
example:
ufw allow to 10.0.0.1 proto ipv6
ufw allow to 10.0.0.1 from 10.4.0.0/16 proto ipv6
IPSec is supported by using the 'esp' ('50') and 'ah' ('51') protocols.
These protocols can only be used with the full syntax. For example:
ufw allow to 10.0.0.1 proto esp
ufw allow to 10.0.0.1 from 10.4.0.0/16 proto esp
ufw allow to 10.0.0.1 proto ah
ufw allow to 10.0.0.1 from 10.4.0.0/16 proto ah
keepalived is supported by using the 'vrrp' ('112') protocol. This pro-
tocol can only be used with the full syntax. For example:
ufw allow to 224.0.0.0/24 from 10.0.0.1 proto vrrp
In addition to the command-line interface, ufw also provides a frame-
work which allows administrators to modify default behavior as well as
take full advantage of netfilter. See the ufw-framework manual page for
more information.
SEE ALSO
ufw-framework(8), iptables(8), ip6tables(8), iptables-restore(8),
ip6tables-restore(8), sysctl(8), sysctl.conf(5)
AUTHOR
ufw is Copyright 2008-2023, Canonical Ltd.
May 2023 UFW:(8)