Server Hardening

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Server Hardening
This is the minimum list of hardening and other steps that need to be performed to secure the Linux server containing the DIVOC platform. The assumption is that the installation happens on a bare metal setup. While the concepts remain the same, the methodology might differ for commercial cloud setups. 
Check for open ports
Identifying open connections to the internet is a critical mission.
netstat -antp
Once you have identified the open ports, you can stop/purge the applications which keep unnecessary ports open. 
The only acceptable open ports are 22 and 443. Access to the other ports outside the Kubernetes network should be prohibited. 
All ingress should be routed through 443 port only as needed.
Secure SSH 
SSH is secure, but we need to harden this service as well. If we can disable SSH, then the problem solved. However, if we want to use it, we have to change the default configuration of SSH. Password-based authentication should be disabled and only key-based authentication should be allowed. The steps for creating sudo users with public and private keys are as follows:
Create a non root sudo user
adduser <user>
Add the user to sudo users group
usermod -aG sudo <user>
Login to the machine as the user
su - <user>
Create SSH directory with appropriate permissions
mkdir -p $HOME/.ssh
chmod 0700 $HOME/.ssh
Generate a key pair for the protocol, and run:
ssh-keygen -t ed25519 -C "My key for DIVOC server"
Share the public key created with users you expect to connect to the server
$HOME/.ssh/id_ed25519.pub
You can modify your SSH configuration to be more secure by performing the following changes to the configuration file:
nano /etc/ssh/sshd_config
Make sure that root cannot login remotely through SSH
PermitRootLogin no
Allow some specific users
AllowUsers [username]
Enable public key-based authentication and disable password-based authentication
PubkeyAuthentication yes
PasswordAuthentication no
There are some additional options that must exist in the “sshd_config” file: MaxAuthTries 5
Finally, set the permissions on the sshd_config file so that only root users can change its contents:
chown root:root /etc/ssh/sshd_config
chmod 600 /etc/ssh/sshd_config
​
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Infrastructure Recovery
DIVOC's Certification and Verification Component
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Check for open ports
Secure SSH