Investigation
If we can execute "wget" as root, we may be able to escalate privileges.
Modify /etc/shadow
Get "/etc/shadow" and generate a new hash passwd, then set it to the shadow file, next upload it.
That changes the root password.
1. Get the Content of /etc/shadow
To see the content of /etc/shadow, we can use netcat listener.
So First, start a listener in local machine.
In target machine, display the contents of the "/etc/shadow" to the local machine using the following command.
We should see the content in our local machine via netcat listener.
Copy the content.
2. Create a New Shadow File
We create a new shadow file in local. The shadow file will be stored into the target /etc/shadow later.
In vim editor (or nano, vi, etc.), paste the content of /etc/shadow which we've copied in the previous section.
3. Create a New Root User Password and Add to Shadow File
Generate a new hash password for a new root user in local machine.
Copy the generated password and paste it at the password of the root user into the "shadow.txt".
As a result, the contents of the "shadow.txt" should look like this:
4. Transfer the Content of the Shadow File
To put the shadow.txt into the target machine, start web server for hosting this file.
Download this file into the /etc/shadow in remote machine. To do that, we need to run it as root.
Finally, you can switch to the root user with the password we've created.