Uncomplicated Firewall
From the project home page:
- Ufw stands for Uncomplicated Firewall, and is a program for managing a netfilter firewall. It provides a command line interface and aims to be uncomplicated and easy to use.
nft accepting iptables syntax, for example within /etc/ufw/before.rules.Installation
Start and enable ufw.service to make it available at boot. Note that this will not work if iptables.service is also enabled (and same for its ipv6 counterpart).
Basic configuration
A very simplistic configuration which will deny all by default, allow any protocol from inside a 192.168.0.1-192.168.0.255 LAN, and allow incoming Deluge and rate limited SSH traffic from anywhere:
# ufw default deny # ufw allow from 192.168.0.0/24 # ufw allow Deluge # ufw limit ssh
The next line is only needed once the first time you install the package:
# ufw enable
ufw.service has been enabled.Finally, query the rules being applied via the status command:
# ufw status
Status: active To Action From -- ------ ---- Anywhere ALLOW 192.168.0.0/24 Deluge ALLOW Anywhere SSH LIMIT Anywhere
Extra information, including the default policies, can be seen with
# ufw status verbose
but this is still limited to user-specified rules. In order to see all rules setup
# ufw show raw
may be used, as well as further reports listed in the manpage. Since these reports also summarize traffic, they may be somewhat difficult to read. Another way to check for accepted traffic:
# iptables -S | grep ACCEPT
While this works just fine for reporting, keep in mind not to enable the iptables service as long as you use ufw for managing it.
/etc/sysctl.d/*, it may be necessary to update /etc/ufw/sysctl.conf accordingly since this configuration overrides the default settings.Forward policy
Users needing to run a VPN such as OpenVPN or WireGuard can adjust the DEFAULT_FORWARD_POLICY variable in /etc/default/ufw from a value of "DROP" to "ACCEPT" to forward all packets regardless of the settings of the user interface. To forward for a specific interface like wg0, user can add the following line in the *filter block
/etc/ufw/before.rules
# End required lines -A ufw-before-forward -i wg0 -j ACCEPT -A ufw-before-forward -o wg0 -j ACCEPT
You may also need to uncomment
/etc/ufw/sysctl.conf
net/ipv4/ip_forward=1 net/ipv6/conf/default/forwarding=1 net/ipv6/conf/all/forwarding=1
Adding other applications
The PKG comes with some defaults based on the default ports of many common daemons and programs. Inspect the options by looking in the /etc/ufw/applications.d directory or by listing them in the program itself:
# ufw app list
If users are running any of the applications on a non-standard port, it is recommended to simply make /etc/ufw/applications.d/custom containing the needed data using the defaults as a guide.
Example, deluge with custom tcp ports that range from 20202-20205:
[Deluge-my] title=Deluge description=Deluge BitTorrent client ports=20202:20205/tcp
Should you require to define both tcp and udp ports for the same application, simply separate them with a pipe as shown: this app opens tcp ports 10000-10002 and udp port 10003:
ports=10000:10002/tcp|10003/udp
One can also use a comma to define ports if a range is not desired. This example opens tcp ports 10000-10002 (inclusive) and udp ports 10003 and 10009
ports=10000:10002/tcp|10003,10009/udp
Deleting applications
Drawing on the Deluge/Deluge-my example above, the following will remove the standard Deluge rules and replace them with the Deluge-my rules from the above example:
# ufw delete allow Deluge # ufw allow Deluge-my
Query the result via the status command:
# ufw status
Status: active To Action From -- ------ ---- Anywhere ALLOW 192.168.0.0/24 SSH ALLOW Anywhere Deluge-my ALLOW Anywhere
Black listing IP addresses
It might be desirable to add ip addresses to a blacklist which is easily achieved simply by editing /etc/ufw/before.rules and inserting an iptables DROP line at the bottom of the file right above the "COMMIT" word.
/etc/ufw/before.rules
... ## blacklist section # block just 199.115.117.99 -A ufw-before-input -s 199.115.117.99 -j DROP # block 184.105.*.* -A ufw-before-input -s 184.105.0.0/16 -j DROP # don't delete the 'COMMIT' line or these rules won't be processed COMMIT
Rate limiting with ufw
ufw has the ability to deny connections from an IP address that has attempted to initiate 6 or more connections in the last 30 seconds. Users should consider using this option for services such as SSH.
Using the above basic configuration, to enable rate limiting we would simply replace the allow parameter with the limit parameter. The new rule will then replace the previous.
# ufw limit SSH
Rule updated
# ufw status
Status: active To Action From -- ------ ---- Anywhere ALLOW 192.168.0.0/24 SSH LIMIT Anywhere Deluge-my ALLOW Anywhere
User rules
All user rules are stored in etc/ufw/user.rules and etc/ufw/user6.rules for IPv4 and IPv6 respectively.
Tips and tricks
Disable remote ping
Change ACCEPT to DROP in the following lines:
/etc/ufw/before.rules
# ok icmp codes ... -A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT
If you use IPv6, related rules are in /etc/ufw/before6.rules.
Disable UFW logging
Disabling logging may be useful to stop UFW filling up the kernel (dmesg) and message logs:
# ufw logging off
GUI frontends
Gufw
gufw is a GTK front-end for Ufw that aims to make managing a Linux firewall as accessible and easy as possible. It features pre-sets for common ports and p2p applications. It requires python, ufw, and GTK support.