Automatically add connected ssh client to /etc/hosts

Warning: this is intended for WAN hosts who don't usually have concurrent ssh connections

Step one Ensure that an entry for ssh-client.local exists in /etc/hosts:

echo "0.0.0.0 ssh-client.local" >>/etc/hosts

Step two Append the following into /etc/profile

if [  "$SSH_CLIENT" ]; then
	sed -i s/$(grep ssh-client.local /etc/hosts | awk '{print $1}')/"${SSH_CONNECTION%% *}"/ /etc/hosts
	cat /dev/null>/tmp/lastsshclient
	echo SSH.ClientIP=\"${SSH_CLIENT%% *}\" >>/tmp/lastsshclient
	echo SSH.ClientAS=\"$(host -t TXT `tr . ' ' <<< "${SSH_CONNECTION%% *}" | awk '{print $4"."$3"."$2"."$1}'`.origin.asn.cymru.com | tr \" '\n' | tail -n+2)\" >>/tmp/lastsshclient
fi

Step three Log in via SSH and try it! (note values have been changed for privacy)

root@localhost:/# grep ssh-client /etc/hosts
192.0.2.145	ssh-client.local

root@localhost:/# cat /tmp/sshclient
SSH.ClientIP="192.0.2.145"
SSH.ClientAS="0000 | 192.0.2.0/24 | US | arin | 1900-01-01"

rohan-molloy/add-ssh-client-to-etc-hosts.md