UIUCTF 2023 - Corny Kernel
Corny Kernel
Corny Kernel is an easy challenge for the UIUCTF 2023 challenge. It’s a misc challenge great for Linux beginners to learn some commands.
In the challenge, we are given a file and a socat command to connect. And likely have to do something with drivers or a kernel.
In the pwnymodule.c we see 2 flags, and an init function and exit function. In these functions, there also an alert and an info messages. That’s where our flag will be.
During review the code, I had to lookup and learn kernel messages. These pr_alert and pr_info functions will become important later.
Socatting into the challenge does a lot, by cd-ing us into root and setting up a root like environment.
We are given a gziped pwnymodule.ko.gz . Decompressing that, we are then left with a .ko file. This is a kernel object file. And we can use kernel management commands like insmod to insert the module, lsmod to list active modules and rmmod to remove modules.
Insmod gives a clear flag part as an alert. The other info message flag is hidden at the moment.
Until we run dmsg or kmsg. At the bottom is the alert and info message of the flag.
This was an easy challenge. Anyone who has used linux for sometime have probably loaded their own drivers or custom drivers before. I have not outside of apt install programs. Fun thing to learn some kernal management commands.