Sunday 15 October 2017

Flare-On Challenge 2017 Writeup

Flare-on is an annual CTF style challenge organized by Fire-eye with a focus on reverse engineering. The contest falls into its fourth year this season. Taking part in these challenges gives us a nice opportunity to learn something new and this year was no exception. Overall, there were 12 challenges to complete. Official solution to the challenges has already been published at the FireEye blog. Hence instead of a detailed write-up, I will just cover the important parts.

#1 - Login.html

The first problem was as simple as it gets. There is an HTML file with a form. We need to provide a flag and check for its correctness.

Figure 1: Check thy flag
The code simply performs a ROT-13 of the input and compares it with another string. To get back the flag, re-apply ROT-13.

Figure 2: ROT-13 again