Script that installs an RSA key on the local machine and a remote machine

Run this interactive bash script, if you want to set up an RSA key on your local machine and then have the script automatically install the key on a remote machine. The script is tested to work on Linux, Unix, AIX with bash.

Here is an example of how the script will run (code is below):

[local_username@localhost /]$ sh generate_ssh_key.sh
Where do you want to place the RSA key?
Enter the remote host (example: example.com or an IP address):
140.130.70.80

Enter user name on the remote host (140.130.70.80):
remote_username

Testing access to remote host (140.130.70.80) with user name (remote_username)
remote_username@140.130.70.80's password:
Connection to 140.130.70.80 closed.

Server returned (remotehostname) as hostname, is this the correct remote host?
1) Yes
2) No
#? 1

Created RSA key name:
local_username_to_remote_username_on_remotehostname_rsa_id

Do you want to allow local_username on localhost_server.com to beable to login to 140.130.70.80 under the ID remote_username without a password?
1) Yes
2) No
#? 1
Generating key...
Setting home directory privileges
Creating RSA key
Don't enter a password below just hit enter:
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in local_username_to_remote_username_on_remotehostname_rsa_id.
Your public key has been saved in local_username_to_remote_username_on_remotehostname_rsa_id.
The key fingerprint is:
da:b6:45:51:98:f6:c7:8e:2b:f4:4b:db:ea:a0:65:f5 local_username@localhost_server.com
The key's randomart image is:
+--[ RSA 2048]----+
| o. |
| +. |
| . *.fff |
| |
+-----------------+
Enter password to 140.130.70.80:

Setting up .ssh folder on remote server
Enter password:
remote_username@140.130.70.80's password:
Connection to 140.130.70.80 closed.

Writing public key to remote authorized_keys file
Enter password:
remote_username@140.130.70.80's password:

Installation of RSA key complete!

Here is the code for the script generate_ssh_key.sh

#!/bin/bash

#######################

# installs an RSA key on the local machine and a remote machine

# Allows you to connect to a remote machine without a password

#######################

base_path=$(pwd);

local_hostname=$(hostname);

local_user=$(whoami);

home_dir=$(dirname ~);

echo "Where do you want to place the RSA key?";

echo "Enter the remote host (example: example.com or an IP address):";

read host;

echo '';

echo "Enter user name on the remote host ($host):";

read username;

echo '';

echo "Testing access to remote host ($host) with user name ($username)";

cmd='hostname';

remote_hostname=$(ssh -t $username@$host "$cmd");

#clean out cariage returns and newlines

remote_hostname=$(echo $remote_hostname | sed 's/\r$//');

remote_hostname=$(echo $remote_hostname | sed 's/\n$//');

remote_hostname=$(echo $remote_hostname | tr -cd '[[:alnum:]]._-');

echo "";

echo "Server returned ($remote_hostname) as hostname, is this the correct remote host?";

select yn in "Yes" "No"; do

case $yn in

Yes ) break;;

No ) exit 1;;

esac

done

#create RSA name based on the remote host name and the remote username

rsa_name="";

rsa_name+=$local_user;

rsa_name+="_to_";

rsa_name+=$username;

rsa_name+="_on_";

rsa_name+=$remote_hostname;

rsa_name+="_rsa_id";

echo "";

echo "Created RSA key name:";

echo "$rsa_name";

echo "";

echo "Do you want to allow $local_user on $local_hostname to beable to login to $host under the ID $username without a password?";

select yn in "Yes" "No"; do

case $yn in

Yes ) echo "Generating key..."; break;;

No ) exit;;

esac

done

#check if user exists on system

if [ -d "$home_dir/$local_user/" ]; then

# Control will enter here if directory exists.

cd ~;

#make sure .ssh directory exists and has user only permissions

echo "Setting home directory privileges";

if [ -d "$home_dir/$local_user/.ssh" ]; then

chmod 700 .ssh;

else

mkdir .ssh;

chmod 700 .ssh;

cd .ssh;

echo "Creating RSA key";

echo "Don't enter a password below just hit enter:";

#generate key

ssh-keygen -t rsa -f $rsa_name;

echo "Enter password to $host:";

#Install key on remote host

set rsa_contents = `cat ~/.ssh/$rsa_name.pub`;

echo '';

echo "Setting up .ssh folder on remote server";

echo "Enter password:";

remote_script=$(echo "

home_dir=$(dirname ~);

cd ~;

if [ -d \".ssh\" ]; then

chmod 700 .ssh;

else

mkdir .ssh;

chmod 700 .ssh;

cd .ssh;

touch authorized_keys;

chmod 600 authorized_keys;

exit;");

ssh -t $username@$host "$remote_script";

echo '';

echo "Writing public key to remote authorized_keys file";

echo "Enter password:";

ssh $username@$host "echo '`cat ~/.ssh/$rsa_name.pub`' >> ~/.ssh/authorized_keys";

echo '';

rm ~/.ssh/$rsa_name.pub;

echo "Installation of RSA key complete!";

echo '';

echo "Use the following to login:";

echo "ssh -i ~/.ssh/$rsa_name $username@$host";

cd $base_path;

exit;

else

echo "Sorry, no home directory found.";