Guide Point Security CTF — Get Hexy (OCT 2021)

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Guide Point Security CTF — Get Hexy (OCT 2021)GetHexy – GuidePoint Security CTF OCT 2021

In the Misc Category of Guide Point CTF which was held on 12 October to 18 October 2021, there was a challenge called “Get Hexy”. let’s solve this challenge.

First, try to run file command on this

it’s just simply zip archive. I use unzip to extract file inside of hexy.zip:

we are given a corrupted zip file. let’s use exiftool if we get any metadata on this file

oh! at the end of output, we get File format error.

try to use zipdetails to display the internal structure of zip files:

try to use hexeditor on this file:

if you’ll notice at the very very top of the file, the hexadecimal side on left and kind of the ASCII side on right, it’s just starting the file with “70 4b 03 04”. A regular PKZIP archive file should be starts with “50 4b 03 04”. we must to modify 70 to PKZIP archive file header magic bytes (50).

save this file. unzip file and it’ll go ahead and

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