Misc02-Art
Description
Category:
MISCELLANEOUS
The best thing about a picture is that it never changes, even when the people in it do, or when it is zoomed in Download file here:
https://drive.google.com/file/d/1J7It1RTd6lSLi-nVqnbAQJn_fuA_PnPj/view?usp=sharing
Solution
Download the file from GG Drive and extracte it, we got one file named
misc02-Art.txt
Open
misc02-Art.txt, there are lines of numbers
This chall is related to Art, so i guess these three numbers are RGB values.
Basic Knowledge
We can convert from image to txt file and vice verse with
convert (a tool included in ImageMagick toolsets)
Mã:
#IMG to Txt
convert misc01.jpg misc01.txt
#Txt to IMG
convert misc01.txt misc01.jpg
Basically, the TXT file, generated from an image, needs two inputs:
- Width * Height (Example: 1080*720 pixels)
- RGB Values (each pixel)
Pillow is a nice tool for converting these raw materials to Image. I found this code byGoogling
Python:
#Constructing the required byte data is trivial with the bytes constructor
img_bytes = bytes([R1, G1, B1, R2, G2, B2,..., Rn, Gn, Bn])
#And then we can create an Image like so:
im = Image.frombytes("RGB", (width, height), img_bytes)
So, we need
a list of bytes (RGB values) and
width*height to retrieve the original image.
Step 1: Finding the original image
First, the file
misc02-Art.txt got 238183 lines
So we need to find all possible cases of A and B (width*height) that:
A * B = 238183
Write a Python Script for this step, the code explains itself
Python:
from colorsys import hsv_to_rgb
from PIL import Image
#Read all RGB values from file misc02-Art.txt
lines=[]
with open('misc02-Art.txt','r') as f:
lines=f.readlines()
list_bytes=[] #[R1, G1, B1, R2, G2, B2,..., Rn, Gn, Bn] integer
#Process for a list of RGB value bytes
for line in lines:
#line :'240-255-222'
line=line.split('-') #line =['240','255','222']
list_bytes.append(int(line[0]))
list_bytes.append(int(line[1]))
list_bytes.append(int(line[2]))
img_bytes = bytes(list_bytes)
#Find the right image resolution and generate Image to folder /images/
# 238183
for i in range(1,119092):
if 238183 % i == 0:
print('found ' +str(i) + ' and ' + str(238183/i))
# Convert list to bytes
img = Image.frombytes('RGB', (i, int(238183/i)), img_bytes)
img.show()
img.save('images/'+str(i)+'.png')
Run the step 1 script. Maybe 367*649 is the right resolution
It automatically open the result images, the right one is:
That’s a Pastebin link which one character is hidden
pastebin.com/H6nid{x}QB
Finding the right Pastebin link
Access a non-exist patesbin got result
Simply write another script to bruteforce it.
Python:
import requests )
ret=''
for i in '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ':
url = '<https://pastebin.com/H6niD'+i+'QB>' # url of paste
print(url)
r = requests.get(url,verify=False)
content = r.text
#Ignore if 'no longer' exists in content
if 'longer' not in content:
print(content)
Run the step 2 script and got Flag
KẾT QUẢ:
Flag: WhiteHat{Ph4n_thu0ng_cu4_b4n_l@_1_Ch1ec_n0n_k1_D13u}
