1,234
edits
Changes
→Resetting the root password
* Get an overview of the course, faculty, and expectations.
* Set up host virtual machine to use in the course.
* Understand how boot records and offline disk file access affect the security of a system.* Understand and modify passwd and shadow files
= Introduction =
* The course is made primarily of labs. It will contain traditional instruction but only enough to get you started. Use the rest of the time to practice what you're supposed to be learning and ask questions when you get stuck or when something doesn't make sense.
* We'll typically have one weak week for each lab. The lab is due in class, and needs to be checked by the professor before class is over. That means you should plan to have everything done by the middle of the class.
* Make the best out of your labbook. Not only is it a record of your progress (and your marks for the labs) but it's a large set of notes you'll be able to use at all the assessments.
* Everything in the labbook must be hand-written (by you) and every page must have your name on it. If I catch you using someone else's notes during an assessment - that will be treated as plagiarism.
== Overview ==
You'll use the Vmware VMware on our lab machines as a hypervisor for your host. Typically you have one hypervisor running a bunch of VMs, but for securitty reasons in our lab environment we'll need to use nested virtualisation.
That means the VMware hypervisor will run on the real hardware (the lab machine) and we'll set up a second hypervisor in one VMware VM, which will host several other VMs.
* The network should be connected on boot, as a dhcp client for now.
* Set the root password to something different from your regular user password.
* Create a regular user with the same username as your matrix (MySeneca) username. Set the password to anything you like, as long as it's different from the root password.
Once the installation is complete your andrewVMhost virtual machine should boot into CentOS when it's powered on, you should be able to log in with your username, and browse the internet using Firefox.
== Create a "secret" files ==
Create a simple text file in your user's home directory called secrets.txt and put some text in that file.
* At this point you'll have unrestricted access to all the files inside the root and home logical volumes you created when you installed CentOS.
* Find the secrets.txt and secrets-root.txt files and read their contents. Modify those files to include the line "Please secure your system!"
* Shut down your VM(properly), disconnect the DVD drive, and boot back into c7host. Check your secret files. Notice that you can't get to them until you log in with a password.
Practice the above by looking for other files that might be of interest. Configuration files, databases, .htaccess files, etc.
== Resetting the root password ==
A variation of the file access above is a specific example of changing a file which contains the root password.
* Boot from SystemRescueCd again and mount your c7host root filesystem.
* Have a look at the etc/passwd file. That has a list of all the users on c7host.
* Have a look at the etc/shadow file. This file has the salted and hashed passwords for all the users that have a password.
* You should understand the structure of both files, epecially:
** username
** UID
** GID
** home directory
** shell
** hashed password
* Replace the hashed password field for the root user with nothing. After editing the line for <code>root</code> should look like this:<code>root:::::::</code>
* Reboot into CentOS and try to log in.
=== The same using CentOS ISO ===
You can accomplish the same thing you did above by using the CentOS ISO instead of SystemRescueCd. It will be easier because you won't need to reset the SELinux context on the shadow file.
* Set up your VM to boot from the CentOS installation ISO.
* At the boot prompt choose Troubleshooting/Rescue a CentOS system.
* When it boots up, choose option 1.
* Notice that the VM's root filesystem has been mounted for you automatically.
* Remove your regular user's password from the shadow file.
* Disconnect the DVD drive, reboot, and log in.
After you're done with this section - reset both your root's and regular user's passwords to something reasonable.
= Lab completion =
* Make sure you understand what you've done in this lab, so that you're ready to answer questions about it.
* Have notes in your labbook from this lab.
* Show your work to the professor and have them sign your labbook.
