Shell Scripting

Demonstration of how to onboard 11 new Linux users into a server. This process will be automated using the "onboard.sh" script located on the main branch of this repository.

Instructions on how to launch and connect to your EC2 instance using an SSH client:

https://github.com/Antonio447-cloud/MEAN-stack-angular

Happy learning!

Onboarding 11 Linux Users into a Server

We will use shell scripts to automate the process of onboarding 11 linux users into a server. We will be doing that by creating a shell script that reads a ".csv file" or "comma-separated values file" that contains the first name of the users to be onboarded.

So, before launching our EC2 instance we change directories to the same directory where we have our private key (.pem file) and we create a file called "onboard.sh". In my case the .pem file is located in my Documents directory:

cd Documents

vim onboard.sh

We input/paste the following code into it:

Now, we copy our "onboard.sh" file to our EC2 instance:

scp -i <private-key> -r onboard.sh ubuntu@<ipv4>:~/

Then we connect to our EC2 instance:

ssh -i "<private-key>" ubuntu@<ipv4>

We generate our SSH key pair:

ssh-keygen

We press "enter" to save the key pair to our home directory and press "enter" again for no passphrase. Then we change directories and list our files:

cd ~/.ssh

ls

Then we check our public and private keys by running :

cat id_rsa.pub

cat id_rsa

We copy both keys into our notepad. Then we change directories and create a new directory called '"Shell":

cd ..

mkidr Shell

Then we move the onboard.sh file to the Shell folder:

$ mv onboard.sh /home/ubuntu/Shell/

We change directories to the "Shell" folder:

cd Shell

We create an "id_rsa", a "id_rsa.pub" and a "name.csv" file.

touch id_rsa id_rsa.pub names.csv

We open the id_rsa.pub file:

vim id_rsa.pub

We paste the public key that we copied into our notepad a minute ago into the id_rsa.pub file:

NOTE: Do not forget to delete the public key from your notepad.

Then we paste the private key that we copied into our notepad a minute ago into the id_rsa. file:

vim id_rsa

NOTE: Do not forget to delete the private key from your notepad.

We go into our names.csv file:

vim names.csv

We insert randon names in it:

Then we go into our "onboard.sh" file:

vim onboard.sh

We change the path that is on the onboard.sh file from from "/root/onboard/id_rsa.pub" to "/home/ubuntu/Shell/id_rsa.pub". To do that we press "/" then we type: "/root/onboard/id_rsa.pub" to take us into that line and we replace it with: /home/ubuntu/Shell/id_rsa.pub:

Changed:

We save and create the developers group:

sudo groupadd developers

Then we make the onboard.sh file executable:

sudo chmod +x onboard.sh

We switch to root user inside the Shell folder:

sudo su

As root user, we run the script:

./onboard.sh

Then we verify that the Linux users were created:

ls -l /home/

We check that the developers group was created too:

getent group developers

We verify that the developers' id "1001" matches with the Linux users' ID:

cat /etc/passwd

To view this with a more legible layout (usually used for data analysis) we run:

cat /etc/passwd | awk -F':' '{print $1}' | xargs -n1 groups

We can test a few of the users randomly. So, let's create a new terminal tab where we are not connected to our EC2 instance. Then we change directories to where we have our EC2 instance's private key:

cd Documents

Then we create a new file called "shell-scripting.pem" and we paste our "id_rsa" private key into it:

vim shell-scripting.pem

Now we test the shell script by connecting as "Antonio" one of the Linux users that we have just created using our shell script. But before we do that, we need to protect our private key. So we run:

sudo chmod 600 shell-scripting.pem

Now we connect as "Antonio":

ssh -i shell-scripting.pem Antonio@<ipv4>

We have just onboarded 11 new Linux users into a server while automating the process using a shell script!

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Legal Disclaimer

The use of code contained in this repository, either in part or in its totality, for engaging targets without prior mutual consent is illegal. It is the end-user's responsibility to obey all applicable local, state and federal laws.

The use of this code is only endorsed by the developers in those circumstances directly related to educational environments or authorized penetration testing engagements whose declared purpose is that of finding and mitigating vulnerabilities in systems, limiting their exposure to compromises and exploits employed by malicious agents as defined in their respective threat models.