b01lers CTF (3–4 Oct, 2020)
This was one of five CTFs going on this weekend. I chose this one because it was beginner friendly and honestly, I needed something easy after working on my python all week, lol.
Let’s see what we have!
This one starts off by providing you a .wav file to examine. I opened it up in Audacity and saw this:
Change to spectogram view like so:
Then you will see the flag:
We receive a photo of questionable quality showing an angry looking man:
For this one I’m thinking exiftool since it will sometimes list the location data of the photo.
We are given a photo of a galaxy with a blue box seemingly hiding some data.
I have a tool I like to use called Steg Online that made quick work of this one. I chose the “LSB Half” option and was able to reveal the flag:
OSINT! My favorite! We are on the hunt for a troll. I checked the hashtag #shrive on Twitter and the first result I got was this:
Looks like they joined in October 2020, so good start.
A lot of the posts are seemingly useless:
But at the very end you will get to a picture of a cake:
Clicking on it will bring you to an imgur account:
If you click on the user’s profile you will see they only have two pictures posted…and one is a troll…
Expand the comments for the flag!
We get a zip file for download and need to look through it to find the flag. When you open it up, you see that there are 400 files.
You could spend the rest of the day searching manually, or just use grep!
We are given a YouTube video to watch, I guess to get in the mood, and then a connection to this web page:
After inspecting the source, I see this:
Let’s try it:
Woah, what do we have here? Looks like a maze to work through. You can’t see it in this photo, but the borders are constantly shifting:
Looking at the source code, I see there is a function called RemoveWall. Also, there is a comment that mentions removing the easterly wall.
I also visited that web page mentioned at the top and found this:
So this could just be about designing the actual maze to avoid errors and have nothing to do with the flag. OR I might need to manipulate the walls in some way.
Ultimately though, I could not figure out how grab that little yellow o! This one remains unsolved by me…for now.
For this challenge we connect to a web page:
I inspected the source code and saw this:
Perhaps I need to look around and find all 5 pieces like a scavenger hunt?
We find the second piece here:
Third piece at the bottom here:
Fourth piece here:
And the fifth here!
We head over to the page listed and see this:
When we add /flag, we are taken to a page that says we need to be admin.
I left at this point to go to one of my son’s football games, came back later, refreshed, and it went right through, so not sure what that was about? Maybe it broke temporarily and I just got lucky?
I also did a bit of dirsearch before they said in the Discord that it was not necessary for any of the web challenges. I got this:
At /console we see the following:
It was probably part of this challenge if it was indeed broken. There was some interesting stuff here:
EDIT: This one was confirmed broken. So I did not solve it the appropriate way. A lot of the web challenges seemed to be going up and down through-out the whole CTF.
This one was driving me crazy until I Googled “Mr. Levenshtein” and came across this:
“… the Levenshtein distance is a string metric for measuring the difference between two sequences. Informally, the Levenshtein distance between two words is the minimum number of single-character edits (insertions, deletions or substitutions) required to change one word into the other. It is named after the Soviet mathematician Vladimir Levenshtein, who considered this distance in 1965.”
I was then able to find this online tool HERE, which helped me to calculate the Levenshtien distances in our puzzle. I came up with these numbers:
1 14 15 18 7 1 14 9 26 5 4 13 9 14 4
I then used another online tool to correlate them all to letters of the alphabet and got:
The second day of the CTF I ended up going hiking with my family a few hours from home, so I did not even touch my computer. I still felt I learned a few useful things the first day though, especially with the crypto method at the end that I had never even heard of.
It also showed me I need to work a bit more on my web and programming skills, so I will focus on that in the upcoming weeks. The Purdue team also have a few tutorials posted on YouTube which I may check out.
Happy Hacking ❤