Peculiar Internet Noteworthy Gizmo 2
Description
The once-elusive netadmin's messages now resonate clearly through the wider network, their intentions revealed for all of us to see.
Note: nmap is allowed INSIDE the instance.
Hint
Solution
The solution is similar to the one for level 1. Here the chall net is way bigger (/20), so maybe some other encoding is used. The hint should point to the standard way to map the IPv4 space: Hilbert curves.
The nmap command is like before: nmap -sn -n 10.20.0.0/20.
From the fact that in a /20 there are 4096 addresses, a 64x64 grid is needed. The order of the required Hilbert curve is 6, since 64 is equal to 2^6.
Plotting the data using a 6th order 2-dimension Hilbert curve reveals a QRcode.
Scanning the QRcode reveals the flag: snakeCTF{next_time_map_all_internet_with_hilbert_curves}
Solver
data = """
Nmap scan report for 10.20.0.1
Nmap scan report for 10.20.0.2
Nmap scan report for 10.20.0.160
[...]
Nmap scan report for 10.20.15.117
"""
data = [d[len("Nmap scan report for 10.20.") :] for d in data.split("\n")[1:-1]]
data = [d.split(".") for d in data]
data = [(int(a) << 8) + int(b) for [a, b] in data]
print(data)
from hilbertcurve.hilbertcurve import HilbertCurve
hilbert_curve = HilbertCurve(6, 2)
points = hilbert_curve.points_from_distances(data)
print(points)
from PIL import Image
img = Image.new("1", (64, 64), 1)
for p in points:
img.putpixel(p, 0)
img.save("map2.png")