> 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/csrf/csrf-referer-validation-depends-on-header-presence.md).
# 仅在 Referer 存在时才验证的 CSRF
仅在 Referer 存在时才验证的 CSRF 笔记，适用于 PortSwigger Web Security Academy 实验室，包括利用流程、载荷测试、Burp Suite 验证和修复上下文。
### Referer 验证依赖于请求头存在时的 CSRF
此实验中的修改电子邮件功能存在 CSRF 漏洞。服务器尝试通过检查该请求头来阻止跨域请求 **Referer**，但存在一种不安全的回退处理：如果 Referer 请求头缺失，就会接受该请求。
* 推荐账户： `wiener:peter` （使用此账户从受害者的角度重现该场景）。
服务器检查 **Referer** 字段来确定请求来自哪里，并拒绝 Referer 不是本站点的请求。
* 通过从攻击服务器发送一个 POST 表单，响应返回： **“无效的 referer 请求头”** ——当该请求头存在且不正确时，检查会生效。
```html
```
`“无效的 referer 请求头”`
然而，如果请求到达时 **无需** referer 请求头缺失，服务器就会接受该请求（危险的回退行为）。
#### 操作方法（原理）
1. 在攻击服务器上托管一个页面，该页面向以下地址提交一个 POST 表单： `/my-account/change-email` 并使用攻击者的电子邮件。
2. 强制利用页面 **移除** 浏览器的 Referer 请求头，使验证失败并被拦截（因为服务器接受 Referer 缺失的情况）。
3. 让浏览器不要发送 Referer 的一种简单方法是在页面中添加一个 `` 标签，然后再提交表单。
```html
```
---
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