Solution for challenge Strange Traffic at the Space Heroes 2022 CTF

strange_traffic.py

import pyshark, binascii

capture = pyshark.FileCapture("strangetraffic.pcap")

# Map the entire keyboard
map = {
    "1": "`",
    "2": "1",
    "3": "2",
    "4": "3",
    "5": "4",
    "6": "5",
    "7": "6",
    "8": "7",
    "9": "8",
    "10": "9",
    "11": "0",
    "12": "-",
    "13": "=",
    "14": "<-",
    "15": "tab",
    "16": "q",
    "17": "w",
    "18": "e",
    "19": "r",
    "20": "t",
    "21": "y",
    "22": "u",
    "23": "i",
    "24": "o",
    "25": "p",
    "26": "[",
    "27": "]",
    "28": "enter",
    "29": "caps",
    "30": "a",
    "31": "s",
    "32": "d",
    "33": "f",
    "34": "g",
    "35": "h",
    "36": "j",
    "37": "k",
    "38": "l",
    "39": ";",
    "40": "'",
    "41": "#",
    "42": "shift",
    "43": "\\",
    "44": "z",
    "45": "x",
    "46": "c",
    "47": "v",
    "48": "b",
    "49": "n",
    "50": "m",
    "51": ",",
    "52": ".",
    "53": "/",
    "54": "ctrl",
    "55": "win",
    "56": "alt",
    "57": "space",
    "58": "alt",
    "59": "win",
    "60": "menu",
    "61": "ctrl",
}

flag = []

for packet in capture:
    payload = packet.layers[2]._all_fields["udp.payload"][75:].split(":") # Ignore the fist 75 characters from the payload
    for i in range(0, len(payload)):
        payload[i] = str(binascii.unhexlify(payload[i]), "ascii") # Coinvert to ASCII representation
    flag.append("".join(payload))

res = ""

for f in flag:
    res += map[str(f)]
print(res.replace("shift[", "{").replace("shift]", "}").replace("enter", "").replace("space", "_")) # Description said we can swap spaces with underscores