Linux privilege escalation with 'sudo'

Learn how to exploit 'sudo' for privilege escalation on Linux.

Linux privilege escalation with 'sudo'

The sudo command allows users to run commands with root privileges, without being root.

In some cases, non-root users are given the ability to run certain commands with administrative privileges. For example, a website user might be configured on a server to run all commands necessary for hosting and managing a website. Some of these commands might have been given permission to run using sudo.

To find out which sudo commands the current user has access to, run the following:

sudo -l

If we are lucky, we might get output similar to the following:

User website may run the following commands on website-hosting-server:
    (ALL) NOPASSWD: /usr/bin/ruby

In this example, ruby has been configured to run using sudo for the website user. Now that we have this information, we can find a way to exploit it. GTFOBins is a great resource for finding such exploits.

Searching GTFOBins for ruby, and filtering by sudo, gives us the following command:

ruby -e 'exec "/bin/sh"'

Running this command as our example website user will start a new bash shell with root privileges! 🎉

Of course, sudo -l could return a plethora of different commands which run using sudo, so you will need research each individual command to find a working sudo exploit.

Closing thoughts

It's not guaranteed that all systems will have the same configuration described in this post, but it's worth checking sudo -l and GTFOBins, as it might enable privilege escalation.

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