SSH - Client and Server

A little script to enable passwordless login

Needless to say, that using this script you should exactly know what you are doing.

!! The author takes NO response for all kinds of damage and security issues that could happen using this script !!

Download

• Ssh_export_pub_key_for_passwordless_login.sh.zip

Source Code

#!/bin/bash
#
cat <<EOF
---------------------------------------------------------------------
This scripts exports THIS computers public ssh key to
a clients's ~/.ssh/authorized_keys2 file.

This will enable passworless login from THIS pc to the client.

You need to specify at least the IP/alias of the other pc!
You optionally can specify another username than the actual one.

Usage: ssh_export ip_of_remote_client  [alternate_username]
---------------------------------------------------------------------

EOF

client="$1"
NAME="$2"
THIS_HOSTNAME="$HOSTNAME"

[ "$NAME" ] || NAME="${USER}"
[ "$client" ]  || echo "ERROR: You have to specify at least a client IP or alias."
[ "$client" ]  || exit 1

cd ~/.ssh

echo -n "* Check connection to client ... "
if ping -c 1 $client > /dev/null
then
	echo OK.
else 
	echo Please check the connection.
	echo   - Aborting here.
	exit 1
fi

echo "* Create ssh dir on client, if it not already exists ... "
ssh ${NAME}@$client "mkdir -p ~/.ssh; chmod 700 ~/.ssh"

echo "* Check if a local pub key exist and/or create one ... "
PUB_KEY="id_dsa.pub"
if test -e $PUB_KEY
then
	echo "   - A file named $PUB_KEY exists."
else
	echo "   - Creating a new one."
	ssh-keygen -t dsa 
fi

echo "* Check, if an older key was exported already in former time to the client."
if
        ssh ${client} "if (cat ~/.ssh/authorized_keys2 | grep ${NAME}@${THIS_HOSTNAME});\
                then echo  - WARNING: An older key was exported before to $client. \
			\n  - Please fix manually.; exit 1; \
                fi";
then
        echo "  - Authorized keys file is clean."
else 
	echo "  - Aborting here."
	exit 1
fi

echo "* Copy the public key of THIS pc to the client ... "
scp id_dsa.pub ${NAME}@$client:~/.ssh/id_dsa.pub_${HOSTNAME}

echo "* We make an entry into the authorized_keys file on the client ... "
ssh ${NAME}@$client "cat ~/.ssh/id_dsa.pub_${HOSTNAME} >> ~/.ssh/authorized_keys2; \
   rm ~/.ssh/id_dsa.pub_${HOSTNAME};"

echo "* Secure the local public key ... "
chmod 600 id_dsa.pub

echo ;
echo "* LET'S TEST IT:"
echo "  Now we test with running the following terminal command."
echo "  You should NOT be prompted by a password."
echo ;

if
        ssh ${NAME}@$client "echo   - This is a message on $client."
then 
        echo "  - Congratulation: If you was NOT promptd for a password,"
	echo "     you can login passwordless to your client $client."
else
	echo "  - WARNING: There was an error with the passwordless login to $client."
        exit 1
fi

echo ;
echo ;
echo "** Program ended."
echo ;
echo If you like to remove the automatic login, you have to 
echo remove the public key in the file /home/${NAME}/.ssh/authorized_keys2
echo on your clients - $client - computer.