SCTF 2021 Writeup¶

from base64 import *
import os
import string

def read(path):
    return open(path, "r").read()

res = []
l = "letf/"
r = "Right/"

def readdir(path):
    if os.path.isfile(path + "data"):
        res.append(path + "data")
    if os.path.isdir(path + l):
        readdir(path + l)
    if os.path.isdir(path + r):
        readdir(path + r)

def get_tree():
    readdir("./src/")
    s = ""
    for i in res:
        s += read(i)
    print(b64decode(s).decode())

# Chinese traditional culture is broad and profound! 
# So I Want Give You My Flag But You Need Decode It.Enjoy The Flag!!:
# 师  兑 复 损  巽 震 晋 姤 大过 讼 噬嗑 震 恒 节 豫 

b64table = string.ascii_uppercase + string.ascii_lowercase + string.digits + '+/'
table = {
    '坤': '000000', '剥': '000001', '比': '000010', '观': '000011', 
    '豫': '000100', '晋': '000101', '萃': '000110', '否': '000111', 
    '谦': '001000', '艮': '001001', '蹇': '001010', '渐': '001011', 
    '小过': '001100', '旅': '001101', '咸': '001110', '遁': '001111', 
    '师': '010000', '蒙': '010001', '坎': '010010', '涣': '010011', 
    '解': '010100', '未济': '010101', '困': '010110', '讼': '010111', 
    '升': '011000', '蛊': '011001', '井': '011010', '巽': '011011', 
    '恒': '011100', '鼎': '011101', '大过': '011110', '姤': '011111', 
    '复': '100000', '颐': '100001', '屯': '100010', '益': '100011', 
    '震': '100100', '噬嗑': '100101', '随': '100110', '无妄': '100111', 
    '明夷': '101000', '贲': '101001', '既济': '101010', '家人': '101011', 
    '丰': '101100', '离': '101101', '革': '101110', '同人': '101111', 
    '临': '110000', '损': '110001', '节': '110010', '中孚': '110011', 
    '归妹': '110100', '睽': '110101', '兑': '110110', '履': '110111', 
    '泰': '111000', '大畜': '111001', '需': '111010', '小畜': '111011', 
    '大壮': '111100', '大有': '111101', '夬': '111110', '乾': '111111'
}
index = '师 兑 复 损 巽 震 晋 姤 大过 讼 噬嗑 震 恒 节 豫'.split(' ')
s = ''.join([b64table[int(table[i], base=2)] for i in index])

print(b64decode(s + '='))
# b'Ch1nA_yyds!'

from PIL import Image 

img = Image.open("TpMSkq.png")
res = Image.new("RGBA", (101, 134))
width, height = img.size 
print(width, height)

print(img.getpixel((800, 1000)))

for i in range(width):
    for j in range(height):
        if i % 9 == 1 and j % 9 == 1:
            pix = img.getpixel((i, j))
            res.putpixel((i // 9, j // 9), pix)

res.save("in_pix.png")

from PIL import Image 
import re

img = Image.new("RGBA", (101, 134))
pattern = re.compile(r'\[38;2;(\d+?);(\d+?);(\d+?)m.')

with open("fumo_a.txt", "r") as f:
    for i in range(50):
        line = f.readline().strip()
        res = pattern.findall(line)
        for j in range(133):
            img.putpixel((i+50, j), tuple(int(res[j][k]) for k in range(3)))

with open("fumo_9.txt", "r") as f:
    for i in range(50):
        line = f.readline().strip()
        res = pattern.findall(line)
        for j in range(133):
            img.putpixel((i, j), tuple(int(res[j][k]) for k in range(3)))

img.save("cli.png")

import wave
import numpy as np
import matplotlib.pyplot as plt

wav = wave.open("c.wav", "r")
nframes = wav.getnframes()
framerate = wav.getframerate()
data = wav.readframes(nframes)
wav.close()
wave_data = np.fromstring(data, dtype=np.short)
wave_data.shape = -1, 2
wave_data = wave_data.T
time = np.arange(0, nframes) * (1.0 / framerate)

res = wave_data[0] + wave_data[1]

plt.figure()
# plt.plot(time, res)
plt.plot(time[87*framerate:128*framerate], res[87*framerate:128*framerate])
plt.show()

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