> 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/path-traversal/path-traversal-with-start-of-path-validation.md).
# 带起始路径验证的路径遍历
### 文件路径遍历，路径开头验证
应用程序通过查询参数传输完整文件路径，并且只检查该路径 **开头** 与预期文件夹匹配。此验证不足：在允许的前缀后追加内容，便可访问任意文件。
#### **分析**
filename 参数直接包含绝对路径，例如：
```bash
/var/www/images
```
如果尝试经典的目录穿越：
```bash
../../../../../etc/passwd
```
应用程序会阻止它。
但如果我们提供 **预期路径**，后跟 `../` 用于跳出的序列，验证就无法检测到越界：
由于路径以 `/var/www/images/`开头，检查通过，但最终解析实际上指向 `/etc/passwd`.
```bash
/var/www/images/../../../../../etc/passwd
```
---
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