Company Leaks Writeup (dCTF 2021)

17 May 2021

D4rkDemian

Type: Misc

Difficulty: Medium

Prompt: Someone hacked and leaked some very important data from an evil company. Find their dirty secrets and expose them!

Solution

We got a zipped file named Leaked.zip from the challenge.So we unzipped it and got a README.md and another zip named super_secret.zip

Now comes the interesting part since we only had a zip so we can try to hashcrack it using john, but it all went in vain…

On solving we got to know that the super_secret.zip also contains a README.md file which is similar to that we have currently!!

So we remembered a perfect github tool named pkcrack which can crack the zip if we have a copy of atleast one file which resides inside the locked zip.

You can read about the tool from here

We ran following bash script to download and install pkcrack in our terminal.

#!/bin/bash -ex

wget https://www.unix-ag.uni-kl.de/~conrad/krypto/pkcrack/pkcrack-1.2.2.tar.gz
tar xzf pkcrack-1.2.2.tar.gz
cd pkcrack-1.2.2/src
make

mkdir -p ../../bin
cp extract findkey makekey pkcrack zipdecrypt ../../bin
cd ../../

Firstly add the in hand README.md file into a zip file as i added it to secret.zip and then ran this command

./pkcrack  -C super_secret.zip -c "README.md" -P secret.zip -p "README.md" 

After running it we got three keys which we can now use to decrypt the super_secret.zip using zipdecrypt

And after unzipping our secret.txt we got our flag just as simple..

dctf{wew_lad_y0u_aCtually_d1d_it}