> 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-bypass-with-null-byte-and-extension-validation.md).
# 使用空字节和扩展名验证绕过路径遍历
使用空字节和扩展名验证绕过路径遍历，PortSwigger Web Security Academy 实验笔记，包括利用流程、载荷测试、Burp Suite 验证以及修复
### 文件路径遍历，使用空字节绕过文件扩展名验证
本实验展示了在显示商品图片时存在的路径遍历漏洞。/ 该应用会检查所提供的文件名是否以预期的扩展名结尾。
目标是读取……的内容 **/etc/passwd** 文件。
#### **分析**
如果直接提供路径
```bash
../../../../etc/passwd
```
应用程序返回错误，因为它要求文件具有以下扩展名 **.jpg**.
在旧版本的 PHP 中（早于 **5.3.4**），可以使用零 **字节（%00）** 来绕过此验证：/ PHP 引擎在空字节处停止读取文件名，而应用程序仍然会看到一个有效的扩展名。
#### **有效载荷**
在扩展名前添加一个空字节：
```bash
%00.jpg
```
浏览器仍然会解析 ".jpg"，但 PHP 会在 " /etc/passwd" 处停止，从而允许你读取敏感文件。
```bash
../../../../etc/passwd%00.jpg
```
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://hacking-notes.jord4n.pro/zh/web/path-traversal/path-traversal-bypass-with-null-byte-and-extension-validation.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
.png?alt=media)
.png?alt=media)