When Stripe ran our CTF 3.0, I wrote most of level 3, which was a full-text search challenge inspired in part by my own livegrep. I wrote a naïve implementation, which just looped over the files, read them into memory, and used java.lang.String.contains to check if each file contained the “needle”, and we released that implementation as the baseline implementation that contestants needed to improve on. I also wrote a solution that used a simple trigram index, which was the solution you h...
