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Charles Varvayanis
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Raspberry Pi Firewall Setup


Step-by-step instructions for setting up a Firewall using iptables with UFW (Uncomplicated FireWall).

 These procedures apply to Raspberry Pi 5, 4 or 3 with Raspberry Pi OS (64-Bit), (32-Bit) or (Legacy, 32-Bit).


General Notes


1. General:  The procedures below are optimized for setting up a firewall on a Raspberry Pi 5, 4 or 3 with Raspberry Pi OS (64-Bit), (32-Bit) or (Legacy, 32-Bit) connected via Ethernet.  Raspberry Pi OS includes iptables, an IP packet filter, however it is disabled by default.  UFW (Uncomplicated FireWall) is a firewall user interface for use with iptables.  UFW together with iptables provide basic firewall features, but lack more sophisticated firewall features and protections.

2. Internet access during setup:  Many of the steps below assume and require the target Raspberry Pi is connected to a network with access to the Internet and a DHCP server is on the network configured for DHCP clients to access the Internet.  This is the standard and/or default configuration for most networks, so in most cases nothing additional will need to be done.



Notice about updates, upgrades and installations failing due to repository or network congestion or outages


Occasionally updates, upgrades and installations fail due to repository or network congestion or outages.  Sometimes there is an appropriate message saying as such, sometimes a missing file is reported, and sometimes there is just a failure message without an explanation.  When this occurs, simply run the command again.  If that does not solve the issues immediately, try again later.



Install and configure a firewall - UFW



Install UFW


Download latest package lists

sudo apt-get update -y

Download and install updated listed packages

sudo apt-get upgrade -y

Download and install UFW

sudo apt install ufw

Once installed, UFW is disabled by default.  The default configuration blocks all incoming traffic (denied), and allows all outgoing traffic (allowed).  Therefore incoming SSH, FTP HTTP, HTTPS and VNC traffic would be denied, however TeamViewer would continue functioning.  It is important to allow necessary management traffic such as SSH and/or VNC prior to enabling the firewall.  Not doing so will require management via TeamViewer or a directly attached Display, Keyboard and Mouse.


Note:  The Subnetwork Mask is expressed in Slash Notation along with an IP Address in certain areas of the next sections.


Network Subnetwork Mask and Slash Notation Relationships:


Class  Mask                      Slash  Nodes
A255.000.000.000/816777214
B255.255.000.000/1665534
B255.255.128.000/1732766
B255.255.192.000/1816382
B255.255.224.000/198190
B255.255.240.000/204094
B255.255.248.000/212046
B255.255.252.000/221022
B255.255.254.000/23510
C255.255.255.000/24254
C255.255.255.128/25126
C255.255.255.192/2662
C255.255.255.224/2730
C255.255.255.240/2814
C255.255.255.248/296
C255.255.255.252/302
C255.255.255.254/310
C255.255.255.255/320


Configure UFW

Set the firewall rules as appropriate for the installation.  Multiple rules can be applied to each service type.  Source Addresses and Source Subnets can be either internal or external of the network the Raspberry Pi is connected to.  If any of the services below have not been installed, do not set a rule for that service.


DHCP


Allow:  sudo ufw allow bootps - Example:  sudo ufw allow bootps


FTP


Allow from anywhere:  sudo ufw allow 21/TCP - Example:  sudo ufw allow 21/TCP

Allow from a specific Subnet:  sudo ufw allow from <SourceSubnetAddress>/<SourceSubnetMask> proto TCP to <YourRaspberryPiIPAddress> port 21 - Example:  ufw allow from 50.209.187.25/29 proto TCP to 192.168.0.25 port 21

Allow from a specific IP Address:  sudo ufw allow from <SourceSubnetAddress> proto TCP to <YourRaspberryPiIPAddress> port 21 - Example:  ufw allow from 50.209.187.26 proto TCP to 192.168.0.25 port 21


SSH


Allow from anywhere:  sudo ufw allow 22/TCP - Example:  sudo ufw allow 22/TCP

Allow from a specific Subnet:  sudo ufw allow from <SourceSubnetAddress>/<SourceSubnetMask> proto TCP to <YourRaspberryPiIPAddress> port 22 - Example:  ufw allow from 50.209.187.25/29 proto TCP to 192.168.0.25 port 22

Allow from a specific IP Address:  sudo ufw allow from <SourceSubnetAddress> proto TCP to <YourRaspberryPiIPAddress> port 22 - Example:  ufw allow from 50.209.187.26 proto TCP to 192.168.0.25 port 22


HTTP


Allow from anywhere:  sudo ufw allow 80/TCP - Example:  sudo ufw allow 80/TCP

Allow from a specific Subnet:  sudo ufw allow from <SourceSubnetAddress>/<SourceSubnetMask> proto TCP to <YourRaspberryPiIPAddress> port 80 - Example:  ufw allow from 50.209.187.25/29 proto TCP to 192.168.0.25 port 80

Allow from a specific IP Address:  sudo ufw allow from <SourceSubnetAddress> proto TCP to <YourRaspberryPiIPAddress> port 80 - Example:  ufw allow from 50.209.187.26 proto TCP to 192.168.0.25 port 80


HTTPS


Allow from anywhere:  sudo ufw allow 433/TCP - Example:  sudo ufw allow 433/TCP

Allow from a specific Subnet:  sudo ufw allow from <SourceSubnetAddress>/<SourceSubnetMask> proto TCP to <YourRaspberryPiIPAddress> port 433 - Example:  ufw allow from 50.209.187.25/29 proto TCP to 192.168.0.25 port 433

Allow from a specific IP Address:  sudo ufw allow from <SourceSubnetAddress> proto TCP to <YourRaspberryPiIPAddress> port 433 - Example:  ufw allow from 50.209.187.26 proto TCP to 192.168.0.25 port 433


VNC Server


Allow from anywhere:  sudo ufw allow 5900/TCP - Example:  sudo ufw allow 5900/TCP

Allow from a specific Subnet:  sudo ufw allow from <SourceSubnetAddress>/<SourceSubnetMask> proto TCP to <YourRaspberryPiIPAddress> port 5900 - Example:  ufw allow from 50.209.187.25/29 proto TCP to 192.168.0.25 port 5900

Allow from a specific IP Address:  sudo ufw allow from <SourceSubnetAddress> proto TCP to <YourRaspberryPiIPAddress> port 5900 - Example:  ufw allow from 50.209.187.26 proto TCP to 192.168.0.25 port 5900



Enable the firewall

sudo ufw enable
Note: This also enables iptables


If it is ever desirable to disable the firewall for testing or other reasons

sudo ufw disable
Note: This also disables iptables


To list current rules

sudo ufw status
  - or -
sudo ufw status verbose


To remove a rule


Identify the rule ID number to be removed

sudo ufw status numbered

Remove the rule by ID number

sudo ufw delete <ID> - Example:  sudo ufw delete 2



Remove packages that were automatically installed and are no longer required

Occasionally excess update, upgrade and installation packages install automatically, but are no longer required and can be removed automatically.

Automatically detect and remove packages no longer required

sudo apt autoremove -y



Charles Varvayanis
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e-mail:  charles@varvayanis.com
Phone:  (209) 586-3782
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