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Hello, everyone, and welcome to this lesson.

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So in the previous lesson, we saw that how we can reset the root password or any other users password

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directly from the grub menu.

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Now you may be thinking that if someone has a physical access to your computer or your device, they

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could possibly reset your password and get into your computer.

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And you must be thinking there should be an additional layer of security that he or she or maybe any

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attacker or a third party person should not be able to access the grub menu and modify those entries.

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So for that, we have a solution.

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We can basically put a password or lock our grub itself.

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So in this lesson, you're going to see how you can keep an additional layer of security by making a

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password for the grub, which is basically protecting it.

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So it will be a two factor authentication for you.

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That is, whenever you need to start your computer, you need to give the authentication that is the

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correct username and password for the grub.

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And then the final login screen, which is the user login that is root and the password.

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So let's see this.

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How to set up a grub based authentication mechanism.

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So first I'm going to open up my terminal, as you can see over here.

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And in the terminal, first, let's verify which is the user currently logged in.

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So I am route.

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These are the steps to set up the password.

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The first step is to generate an encrypted hash value.

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So for that, the command is grub mic password in the format, which is PB CD F two.

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Now if you're not aware about what what is PB F two, then it is basically a hashing algorithm.

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So it applies a pseudo random function, such as a hash based message authentication code, which is

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a smack to the input password or passphrase that we are going to provide.

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That is, let's say my password is going to be root with a salt value which is random and repeats the

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process many times to produce a derived key which is basically secure.

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Now it utilizes that specific key for further subsequent operations or other actions wherein it needs

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to provide the authentication.

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So let's see this how it actually works.

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So I need to type this command and hit enter.

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Now this is asking for the password or passphrase that you need to provide.

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As you can see over here, I have provided my password as root and it has generated successfully a hash

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of my password as can be seen under the screen.

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Alright.

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So we have successfully generated the hash for my password using the cryptographic algorithm which is

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PB CD F two.

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Quickly, let's open up a new terminal window.

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And now in the new terminal window, what we are going to do is we are going to modify a file which

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is 40 custom.

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What is the reason to modify this file?

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You will come to know in just a few seconds.

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So let's first go into the directory of Grab, which is under the EDC home directory.

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Once we are over here, we will quickly create a backup file of this 40 underscore custom file.

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In case anything goes wrong, we can rollback all our changes.

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Now, once you are into this file, you need to modify this so you can use nano or vim I'm using currently

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nano.

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This is basically the configuration file which is required to give instructions that we need to set

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up a username password into our grub.

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We have already generated a hash and we will now use that hash as password while we log in into the

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machine at the grub screen.

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So you can specify the name of the user over here.

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So I'm specifying the root user because I want to authenticate as the root user.

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So set super users as root and the password.

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So password underscore pb cd f to the username once more that is root and the hash here.

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This is basically the hash that we have generated in the previous step, which is this you need to keep

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in mind that you need to copy the hash from your password is after that string complete and grub dot

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starts.

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You need to copy that which is highlighted currently on the left terminal.

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So I'll just copy this quickly and you need to paste it over here.

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I already have an older hash which I will remove and I will replace it with the newer hash that we have

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generated recently.

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So we have successfully deleted the old hash and replaced it with a new hash value.

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Looks perfect.

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Now we are going to save this file, this hash and the new hash is exactly the same.

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So we need to save that file.

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So we'll quickly just say control SX and we'll come out of the file.

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The next step is to make config.

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So we are going to give this command which is grep make config hyphen.

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Oh, the configuration file of grub by doing this command grub will automatically verify that whatever

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changes that we have done in the configuration file are correct or no.

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It will also try to load the new changes that we have created in the 40 underscore custom file.

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You can see it verified everything was correct.

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So now we are going to do a restart onto the computer.

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So we have used the command that is in it six.

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You can see the computer is going to boot in 4 seconds as can be seen over here and it will present

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us a grub menu.

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Now, previously it used to just load the grub menu and start the Kali Linux machine where it would

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ask the username and password.

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But now here you can see it is asking a username and password at the group screen itself.

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Now we need to give the correct username and password to the grub screen to verify that yes, we have

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the access to modify changes into this machine or the grub entry as well.

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Once we verify this correctly, this computer will now start and will present a new login screen for

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us, which is basically the user login to which we want to log in.

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So I have provided the correct username and password for the grub menu, which was root and root and

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hit enter.

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Now you can see the famous Curly team logo has successfully loaded and here I need to log in so I will

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use my username password which is root and a BCD and hit enter.

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You can successfully verify.

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I have successfully logged in into my computer.

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So this is it for this lesson.

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I hope you guys understood how you can configure a password for your computer.

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Thank you.