description:
What a small world!
Approach#
!! I wasn’t able to solve this challenge during the CTF !!
For this challenge we were given the .jpg image
Opening the image in GIMP throughs the following error
Corrupt JPEG data: 41231 extraneous bytes before marker 0xd9
The only interesting info I found in the exiftool info was
X Resolution : 72
Y Resolution : 72
Resolution Unit : inches
Displayed Units X : inches
Displayed Units Y : inches
Image Width : 10
Image Height : 10and binwalk didn’t reveal anything obvious to me either
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
0 0x0 JPEG image data, EXIF standard
12 0xC TIFF image data, big-endian, offset of first image directory: 8
483 0x1E3 Copyright string: "Copyright (c) 1998 Hewlett-Packard Company"Solution#
After the ctf I saw on the WaniCTF discord that the given image was only being displayed partly and the rest was hidden
This still didn’t give me an obvious solution so I went looking for the writeups. The most helpful one was definintely this one
In this writeup the author links to this amazing reference for hiding info by manipulating an image’s height
following the instructions in the article, I converted my image to hex in cyberchef, found the ff c0 marker identifier and messed around with height and width until I could see the full image :)
Flag#
FLAG: FLAG{b1g_en0ugh}