To start with, UTCTF 2019 had pretty high scores for every challenge ie. The points were ranged from 100 to 2000.
And They were all fun to solve, But I personally liked Regular Zips as I learn a lot about Regular Expressions and ofcourse python’s awesomeness. XD
Being a 600 pts challenge, it was somewhat a medium level challenge.
Thanks to my friend @HimanshuKr who helped me with this challenge.
So I started with the given regular expression in the problem.txt which was provided to us. Also it was the same regex which was in the challenge description.
We were also given a zip which was obviously encrypted and we had to decrypt by brute-forcing it against some words that satisfy the regex.
I quickly used my google foo skills to search for a Regex library which can be used with python to generate those words.
Oh there’s a perfect library for our work => exrex
Install it using :
pip install exrex
And I shooted Sublime to make a wordlist and brute-force at the same time using python :
And we got our password…
But Be careful with spaces and tabs !!
Password found: 7 y RUHKKx2 R47gB N
But that’s not enough, we have a long journey ahead. lols..
So after extracting it we get another zipfile as archive.zip and a hint.txt file which contains another regex sadly.
So we can just write a script to extract all of the archives until we are left with none of them. I used zipfile library in python to workaround with zip files in python and added some colors to make the automation process more fun.
I created a new directory and placed this script along with RegularZips.zip and Problem.txt.
And To our Surprise …
There was a flag.txt in archive998.
The Flag was :
Wasn’t it Sw33t.
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Keep Waiting for my next writeup.
Till then Keep Escalating the Priveleges and Happy Hacking !!