Linux SSH

Lock SSH

cat <<EOF >> /etc/ssh/sshd_config
MaxAuthTries 3
PermitRootLogin no
PasswordAuthentication no
PermitEmptyPasswords no
UsePAM yes
PubkeyAuthentication yes
EOF

OR

sed -i -e 's/#PasswordAuthentication yes/PasswordAuthentication no/i' /etc/ssh/sshd_config

Create key

ssh-keygen -b 4096

Cat your Key

cat ~/.ssh/id_rsa.pub

Add Key to SSH

cat id_rsa.pub >> /home/$USER/.ssh/authorized_keys

Known Hosts

Remove Entry from the Known-Hosts File.

ssh-keygen -R hostname

Using the SSH Config File

If you are regularly connecting to multiple remote systems over SSH, you can configure your remote servers with the .ssh/config file.

Example:*

Host dev
    HostName dev.your-domain
    User xcad
	Port 7654
    IdentityFile ~/.ssh/targaryen.key

Host *
    User root
    Compression yes

Connect to a host (like dev , eg.) with ssh dev.

Logging SSH Users

If you want to log all users comming true SSHand send Slack notification.

#!/bin/bash
echo "Success user login on jump-staging" > /tmp/logging.txt
last -3 -i | awk '{print $1,$3,$4,$5,$6,$7,$8,$9,$10}' >> /tmp/logging.txt
message=$(cat /tmp/logging.txt | head -n 4)
curl -X POST -H 'Content-type:application/json' --data '{"text":"'"\`\`\`$message\`\`\`"'"}' https://hooks.slack.com/services/T8M1RD/B01TLtF1IrGhMA9d
sudo rm /tmp/logging.txt
# This is set in /etc/profile.d/login_staging.sh