Description: What is the data of the image.
First, some recon to see what we're working with.
The challenge file with a .png extension isn't a PNG file at all, but rather a text file. I used the cat command to read what values are actually inside the PNG file.
These numbers look very familiar especially, after finishing the rock&roll challenge. These are the magic numbers for a PNG file, but their order is odd. Every 4 bytes are flipped. Using a python script to reverse the bytes:
def invert_hex_bytes(input_file, output_file):
with open(input_file, 'r') as f:
hex_data = f.read().strip()
hex_data = hex_data.replace(" ", "").replace("\n", "")
if len(hex_data) % 8 != 0:
print("Error: Hex data length is not a multiple of 4 bytes (8 hex characters).")
return
inverted_hex = ""
for i in range(0, len(hex_data), 8):
chunk = hex_data[i:i+8]
inverted_chunk = chunk[6:8] + chunk[4:6] + chunk[2:4] + chunk[0:2]
inverted_hex += inverted_chunk
with open(output_file, 'w') as f:
for i in range(0, len(inverted_hex), 8):
f.write(inverted_hex[i:i+8] + "\n")
print(f"Inverted hex dump written to {output_file}.")
input_file = 'hex_dump.txt'
output_file = 'inverted_hex_dump.txt'
invert_hex_bytes(input_file, output_file)
We get the corrected output of the text file as a hex dump. Now we turn the hex dump back into a PNG by using hexed.it
And we get the flag.
