HACKvent 2019: Day 1

Challenge

HV19.01 censored

I got this little image, but it looks like the best part got censored on the way. Even the tiny preview icon looks clearer than this! Maybe they missed something that would let you restore the original content?

Solution

The hint indicates that we should have a clearer smaller image available to us.
At first we attempt to shrink the image, resharpen and enlarge but there is too much degradation for that to work. We also open the image in GIMP and mess with levels/contrast with no luck.

Finally, we use binwalk on the image to find hidden binaries and find:

$ python .\binwalk .\f182d5f0-1d10-4f0f-a0c1-7cba0981b6da.jpg

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             JPEG image data, EXIF standard
12            0xC             TIFF image data, little-endian offset of first image directory: 8
332           0x14C           JPEG image data, JFIF standard 1.01

We extract the second JPEG image in this file which gives us a smaller preview thumbnail but with a crisp QR code!

This image is good enough to scan and gives us our flag!

Flag:

HV19{just-4-PREview!}