4 April 2019

Encryptctf Journeytothecentreofthefile1

by eshaan7

Challenge: Journey to the centre of the file 1(for 75 points, static) [Forensics]

Challenge description:

"Nearly everything is really interesting if you go into it deeply enough …" - Richard Feynman
Author: maskofmydisguise
file : (ziptunne1.gz)[]

Let’s capture tis fl4g:

We are given a ziptunne1.gz file which as the name says is gzipped again and again.

I don’t know if someone tried this manually, but seriously like um don’t do that? We are hackers, let the computer do the manual labour for us! So we write a shell script. ez pz I use range 1-100 cz we don’t know how many stages of archiving is there. So just a guess.


mkdir tmp
cp ziptunnel1.gz tmp/ # creating tmp directory and solving there coz we use `ls` to get filenames
cd tmp/
for i in {1..100}
	if [ $((i%2)) -eq 0 ]
   		gzip -d *
		unzip *
		rm *.zip > /dev/null 2>&1

As the script loops over every stage, it finally hits a stop when we get a flag.txt which contains the flag! ez pz

FLAG: encryptCTF{w422up_b14tch3s}

Thankyou for reading, happy hackin’! ~ eshaan7