Security Best Practices for your ETH staking validator node

Completing this guide will provide a solid baseline to protect and secure your staking node.
​🤖
 Pre-requisites
Ubuntu Server or Ubuntu Desktop installed on a local computer. Bonus points for increasing decentralization of Ethereum and not relying on cloud providers.
a SSH client or terminal window access
In case you need a SSH client for your operating system, refer to:
How to Connect to an SSH Server from Windows, macOS, or Linux
How-To Geek
​🧙♂
 Mandatory: Create a non-root user with sudo privileges
If you're using Ubuntu Desktop then you're likely currently on your staking node. Simply open a terminal window from anywhere by typing Ctrl+Alt+T.
Otherwise, begin by connecting to Ubuntu Server with your SSH client.
ssh [email protected]
Create a new user called ethereum
sudo useradd -m -s /bin/bash ethereum
Set the password for ethereum user
sudo passwd ethereum
Add ethereum to the sudo group
sudo usermod -aG sudo ethereum
​🔐
 Mandatory: Disable SSH password Authentication and Use SSH Keys only
If you're using Ubuntu Desktop locally, you can skip this section.
The basic rules of hardening SSH are:
No password for SSH access (use private key)
Don't allow root to SSH (the appropriate users should SSH in, then su or sudo)
Use sudo for users so commands are logged
Log unauthorized login attempts (and consider software to block/ban users who try to access your server too many times, like fail2ban)
Lock down SSH to only the ip range your require (if you feel like it)
Create a new SSH key pair on your local machine. Run this on your local machine. You will be asked to type a file name in which to save the key. This will be your keyname.
ssh-keygen -t ed25519
Your SSH key pair is stored in your home directory. For example, if your keyname was mySSHkey, then your private SSH key is mySSHkey and your public SSH key is mySSHkey.pub
IMPORTANT: Make multiple backup copies of your private SSH key file to external storage, such as a USB backup key, for recovery purposes.
​
Verify the contents of your private SSH key file before moving on. 
cat <keyname>
​
It should look similar to this example.
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
QyNTUxOQAAACBAblzWLb7/0o62FZf9YjLPCV4qFhbqiSH3TBvZXBiYNgAAAJCWunkulrp5
LgAAAAtzc2gtZWQyNTUxOQAAACBAblzWLb7/0o62FZf9YjLPCV4qFhbqiSH3TBvZXBiYNg
AAAEAxT+yCmifGWgbFnkauf0HyOAJANhYY5EElEX8fI+M4B0BuXNYtvv/SjrYVl/1iMs8J
XioWFuqJIfdMG9lcGJg2AAAACWV0aDJAZXRoMgECAwQ=
-----END OPENSSH PRIVATE KEY-----
Transfer the public key to your remote node. Replace <keyname.pub> appropriately.
ssh-copy-id -i $HOME/<keyname.pub> [email protected]
Login with your new ethereum user
ssh [email protected]
Disable root login and password based login. Edit the /etc/ssh/sshd_config file
sudo nano /etc/ssh/sshd_config
Locate ChallengeResponseAuthentication and update to no
ChallengeResponseAuthentication no
Locate PasswordAuthentication update to no
PasswordAuthentication no
Locate PermitRootLogin and update to prohibit-password
PermitRootLogin prohibit-password
Locate PermitEmptyPasswords and update to no
PermitEmptyPasswords no
Optional: Locate Port and customize it your random port.
Port <your random port number>
A valid random port # ranges from 1024 thru 49141.
Check that the port is not already used by other services. Replace <port> with your random port #.
sudo ss -ntlp | grep :<port>
Empty response means the port is good.
A response with red numbers means the port is already used. Choose another port.
Validate the syntax of your new SSH configuration.
sudo sshd -t
If no errors with the syntax validation, restart the SSH process
sudo systemctl restart sshd
Verify the login still works
Standard SSH Port 22
Custom SSH Port
ssh [email protected]
ssh [email protected] -p <custom random port number>
Optional: Make logging in easier by updating your local ssh config.
To simplify the ssh command needed to log in to your server, consider updating your local $HOME/.ssh/config file:
Host ethereum-server
  User ethereum
  HostName <staking.node.ip.address>
  Port <custom random port number>
This will allow you to log in with ssh ethereum-server rather than needing to pass through all ssh parameters explicitly.
​🤖
 Mandatory: Update your system
It's critically important to keep your system up-to-date with the latest patches to prevent intruders from accessing your system.
sudo apt-get update -y && sudo apt dist-upgrade -y
sudo apt-get autoremove
sudo apt-get autoclean
Enable automatic updates so you don't have to manually install them.
sudo apt-get install unattended-upgrades
sudo dpkg-reconfigure -plow unattended-upgrades
Reboot your system to enable the upgrades.
sudo reboot
​🧱
 Mandatory: Configure your Firewall
The standard UFW firewall can be used to control network access to your node.
With any new installation, ufw is disabled by default. Enable it with the following settings.
If you used a custom random SSH port, replace "22" with your actual port #.
Lighthouse
Prysm
Teku
Nimbus
Lodestar
# By default, deny all incoming and outgoing traffic
sudo ufw default deny incoming
sudo ufw default allow outgoing
# Allow ssh access
sudo ufw allow 22/tcp
# Allow consensus client port
sudo ufw allow 9000
# Allow execution client port
sudo ufw allow 30303
# Enable firewall
sudo ufw enable
# By default, deny all incoming and outgoing traffic
sudo ufw default deny incoming
sudo ufw default allow outgoing
# Allow ssh access
sudo ufw allow 22/tcp
# # Allow consensus client port
sudo ufw allow 13000/tcp
sudo ufw allow 12000/udp
# Allow execution client port
sudo ufw allow 30303
# Enable firewall
sudo ufw enable
# By default, deny all incoming and outgoing traffic
sudo ufw default deny incoming
sudo ufw default allow outgoing
# Allow ssh access
sudo ufw allow 22/tcp
# Allow consensus client port
sudo ufw allow 9000
# Allow execution client port
sudo ufw allow 30303
# Enable firewall
sudo ufw enable
# By default, deny all incoming and outgoing traffic
sudo ufw default deny incoming
sudo ufw default allow outgoing
# Allow ssh access
sudo ufw allow 22/tcp
# Allow consensus client port
sudo ufw allow 9000
# Allow execution client port
sudo ufw allow 30303
# Enable firewall
sudo ufw enable
# By default, deny all incoming and outgoing traffic
sudo ufw default deny incoming
sudo ufw default allow outgoing
# Allow ssh access
sudo ufw allow 22/tcp
# Allow consensus client port
sudo ufw allow 9000
# Allow execution client port
sudo ufw allow 30303
# Enable firewall
sudo ufw enable
Confirm the settings are in effect. 
sudo ufw status numbered
Example of properly configured ufw status for Lighthouse.
     To                         Action      From
     --                         ------      ----
[ 1] 22/tcp                     ALLOW IN    Anywhere
[ 2] 9000                       ALLOW IN    Anywhere
[ 3] 30303                      ALLOW IN    Anywhere
[ 4] 22/tcp (v6)                ALLOW IN    Anywhere (v6)
[ 5] 9000 (v6)                  ALLOW IN    Anywhere (v6)
[ 6] 30303 (v6)                 ALLOW IN    Anywhere (v6)
Port Forwarding Tip: You'll need to forward and open ports to your validator. 
​
Verify port forwarding is working with
​https://www.yougetsignal.com/tools/open-ports/ 
or https://canyouseeme.org​
As an example, for Lighthouse, you would verify ports 9000 and 30303 are reachable.
​
For advice on configuring port forwarding with routers, refer to this general port forwarding guide.​
Note for Grafana Users: Do not expose Grafana (port 3000) to the public internet as this invites a new attack surface! A secure solution would be to access Grafana through a ssh tunnel.
Example of how to create a ssh tunnel:
ssh -N -v [email protected] -L 3000:localhost:3000
[ Optional ] Whitelisting, which means permitting connections from a specific IP, can be setup via the following command.
sudo ufw allow from <your local daily laptop/pc>
# Example
# sudo ufw allow from 192.168.50.22
​⛓
 Mandatory: Install Fail2ban
Fail2ban is an intrusion-prevention system that monitors log files and searches for particular patterns that correspond to a failed login attempt. If a certain number of failed logins are detected from a specific IP address (within a specified amount of time), fail2ban blocks access from that IP address.
sudo apt-get install fail2ban -y
Edit a config file that monitors SSH logins.
sudo nano /etc/fail2ban/jail.local
Add the following lines to the bottom of the file.
​🔥
 Whitelisting IP address tip: The ignoreip parameter accepts IP addresses, IP ranges or DNS hosts that you can specify to be allowed to connect. This is where you want to specify your local machine, local IP range or local domain, separated by spaces.
# Example
ignoreip = 192.168.1.0/24 127.0.0.1/8
[sshd]
enabled = true
port = <22 or your random port number>
filter = sshd
logpath = /var/log/auth.log
maxretry = 3
# whitelisted IP addresses
ignoreip = <list of whitelisted IP address, your local daily laptop/pc>
Save/close file.
Restart fail2ban for settings to take effect.
sudo systemctl restart fail2ban
​🐻
 Optional: Disable root account
System admins should not frequently log in as root in order to maintain server security. Instead, you can use sudo execute that require low-level privileges.
# To disable the root account, simply use the -l option.
sudo passwd -l root
# If for some valid reason you need to re-enable the account, simply use the -u option.
sudo passwd -u root
​🛠
 Optional: Setup Two Factor Authentication for SSH
SSH, the secure shell, is often used to access remote Linux systems. Because we often use it to connect with computers containing important data, it’s recommended to add another security layer. Here comes the two factor authentication (2FA).
sudo apt install libpam-google-authenticator -y
To make SSH use the Google Authenticator PAM module, edit the /etc/pam.d/sshd file:
sudo nano /etc/pam.d/sshd
Add the following line:
auth required pam_google_authenticator.so
Now you need to restart the sshd daemon using:
sudo systemctl restart sshd.service
Modify /etc/ssh/sshd_config
sudo nano /etc/ssh/sshd_config
Locate ChallengeResponseAuthentication and update to yes
ChallengeResponseAuthentication yes
Locate UsePAM and update to yes
UsePAM yes
Save the file and exit.
Run the google-authenticator command.
google-authenticator
It will ask you a series of questions, here is a recommended configuration:
Make tokens “time-base”": yes
Update the .google_authenticator file: yes
Disallow multiple uses: yes
Increase the original generation time limit: no
Enable rate-limiting: yes
You may have noticed the giant QR code that appeared during the process, underneath are your emergency scratch codes to be used if you don’t have access to your phone: write them down on paper and keep them in a safe place.
Now, open Google Authenticator on your phone and add your secret key to make two factor authentication work.
Note: If you are enabling 2FA on a remote machine that you access over SSH you need to follow steps 2 and 3 of this tutorial to make 2FA work.
​🧩
 Optional: Secure Shared Memory
One of the first things you should do is secure the shared memory used on the system. If you're unaware, shared memory can be used in an attack against a running service. Because of this, secure that portion of system memory.
To learn more about secure shared memory, read this techrepublic.com article.
One exceptional case
There may be a reason for you needing to have that memory space mounted in read/write mode (such as a specific server application like DappNode that requires such access to the shared memory or standard applications like Google Chrome). In this case, use the following line for the fstab file with instructions below.
none /run/shm tmpfs rw,noexec,nosuid,nodev 0 0
The above line will mount the shared memory with read/write access but without permission to execute programs, change the UID of running programs, or to create block or character devices in the namespace. This a net security improvement over default settings.
Use with caution
With some trial and error, you may discover some applications(like DappNode) do not work with shared memory in read-only mode. For the highest security and if compatible with your applications, it is a worthwhile endeavor to implement this secure shared memory setting.
Source: techrepublic.com​
Edit /etc/fstab
sudo nano /etc/fstab
Insert the following line to the bottom of the file and save/close. This sets shared memory into read-only mode.
tmpfs    /run/shm    tmpfs    ro,noexec,nosuid    0 0
Reboot the node in order for changes to take effect.
sudo reboot
​👩🚀
 Optional: Use system user accounts - Principle of Least Privilege [Advanced Users]
Recommended for Advanced Users Only
Principle of Least Privilege: Each eth2 process is assigned a system user account and runs under the least amount of privileges required in order to function. This best practice protects against a scenario where a vulnerability or exploit discovered in a specific process might enable access other system processes.
# creates system user account for eth1 service
sudo adduser --system --no-create-home eth1
​
# creates system user account for validator service
sudo adduser --system --no-create-home validator
​
# creates system user account for beacon-chain service
sudo adduser --system --no-create-home beacon-chain
​
# creates system user account for slasher
sudo adduser --system --no-create-home slasher
​🔥
 Caveats For Advanced Users
If you decide to use system user accounts, remember to replace the systemd unit files with the corresponding users.
# Example of beacon-chain.service unit file
User            = beacon-chain
Furthermore, ensure the correct file ownership is assigned to your system user account where applicable.
# Example of prysm validator's password file
sudo chown validator:validator -R $HOME/.eth2validators/validators-password.txt
​✨
 Additional validator node best practices
Networking
Assign static internal IPs to both your validator node and daily laptop/PC. This is useful in conjunction with ufw and Fail2ban's whitelisting feature. Typically, this can be configured in your router's settings. Consult your router's manual for instructions.
Power Outage
In case of power outage, you want your validator machine to restart as soon as power is available. In the BIOS settings, change the Restore on AC / Power Loss or After Power Loss setting to always on. Better yet, install an Uninterruptable Power Supply (UPS).
Clear the bash history
When pressing the up-arrow key, you can see prior commands which may contain sensitive data. To clear this, run the following:
shred -u ~/.bash_history && touch ~/.bash_history
​🚀
 References
How to Harden your Ubuntu 18.04 Server
Medium
Ubuntu system hardening guide for desktops and servers
Linux Audit
How To Harden OpenSSH on Ubuntu 18.04 | DigitalOcean
DigitalOcean
Configure SSH to use two-factor authentication | Ubuntu
Ubuntu
How to Install and Configure Fail2ban on Ubuntu 20.04
linuxize
​https://gist.github.com/lokhman/cc716d2e2d373dd696b2d9264c0287a3#file-ubuntu-hardening-md​
How to Harden Ubuntu Server 18.04 in 5 Easy Steps
Lifewire
The 50 Best Linux Hardening Security Tips: A Comprehensive Checklist
UbuntuPIT

Prerequisites

Signing up to be a validator at the Launchpad

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Pre-requisites

Mandatory: Create a non-root user with sudo privileges

Mandatory: Disable SSH password Authentication and Use SSH Keys only

Mandatory: Update your system

Mandatory: Configure your Firewall

Mandatory: Install Fail2ban

Optional: Disable root account

Optional: Setup Two Factor Authentication for SSH

Optional: Secure Shared Memory

Optional: Use system user accounts - Principle of Least Privilege [Advanced Users]

Additional validator node best practices

References

​🤖 Pre-requisites

​🧙♂ Mandatory: Create a non-root user with sudo privileges

​🔐 Mandatory: Disable SSH password Authentication and Use SSH Keys only

​🤖 Mandatory: Update your system

​🧱 Mandatory: Configure your Firewall

​⛓ Mandatory: Install Fail2ban

​🐻 Optional: Disable root account

​🛠 Optional: Setup Two Factor Authentication for SSH

​🧩 Optional: Secure Shared Memory

​👩🚀 Optional: Use system user accounts - Principle of Least Privilege [Advanced Users]

​✨ Additional validator node best practices

​🚀 References