Challenge #1 - X

Description

Welcome to the 10th Annual Flare-On Challenge!

Statistically, you probably won’t finish every challenge. Every journey toward excellence starts somewhere though, and yours starts here. Maybe it ends here too.

This package contains many files and, I can’t believe i’m saying this, click the one with the “.exe” file extension to launch the program. Maybe focus your “reverse engineering” efforts on that one too.

Solution

Since the pin only 2 digits, i bruteforce it manually.

Another solution is by decompiling the program using dnspy. At the time of competition i used old version of dnspy which didn't produce the actual code. But after competition i notice that there is a new version of dnspy that maintained by another user. Download the latest version from the repository and then decompile the X.dll.

old version of dnspy

new version of dnspy

By executing the program we know that the flag will be shown if we input valid 2 digits and click the "lock" button. Based on the function structure name, the function lockButton_Click will be the called function when we click the "lock" button. So by looking at decompiler result we can get the flag directly in plaintext.

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