Challenge: “Santa is grateful for his little helpers who contribute to the Xmas spirit, so do not forget to check them out!”
This one had me running in circles, I solved it on day 4. I was only able to start with the challenge in the evening, so then the hint was already posted, and that was later extended to this: “Some elves told us about OSINT. Have you ever heard about OSINT? They gave Santa a hint regarding an image with Xmas tree that’s spreading on social media sites! 3/3(FB, Twitter)” OSINT refers to “Open Source INTelligence”, that basically means, gathering information from public sources like google, Twitter, Facebook… I was expecting to find an image of a Christmas tree with clearly visible flag and so spent hours sifting through public images on FB and TW with words like #tree, #xmas, #elves… Oh boy the things I’ve seen…. On day 4 I realized that “little hepers” does not refer to elves, or perhaps reindeer, but to the good people setting up the CFT, BSidesLjubljana, SSRD and Viris. Since a picture of the ASCII tree was popping up more and more, I downloaded it, tried to Exif it only to stumble on the solution by chance. The flag was a barely visible text on the background.
Here are the links:
- SSRD: https://twitter.com/ssrd_io/status/1200729814929494016
- TeamViris: https://twitter.com/TeamViris/status/1200771859010207746
- BSidesLjubljana: https://www.facebook.com/photo.php?fbid=10222068176920321&set=gm.843539629396912&type=3&theater&ifg=1
Flag: xmas{ChestnutsRoasting_On4nOpenF1r3}
What did I learn: Think about what the author of the CTF can influence. That is usually NOT the whole Twitter or Google Image search… It usually closer to “home”.
