# Drupal RCE
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{% endhint %}
## With PHP Filter Module
{% hint style="warning" %}
In older versions of Drupal **(before version 8)**, it was possible to log in as an admin and **enable the `PHP filter` module**, which "Allows embedded PHP code/snippets to be evaluated." But from version 8 this module is not installed by default.
{% endhint %}
1. Go to **/modules/php** and if a 403 error is returned then the **PHP filter plugin is installed and you can continue**
1. If not, go to `Modules` and check on the box of `PHP Filter` and then on `Save configuration`
2. Then, to exploit it, click on `Add content` , then Select `Basic Page` or `Article` and write the **PHP backdoor**, then select `PHP` code in Text format and finally select `Preview`
3. To trigger it, just access the newly created node:
```bash
curl http://drupal.local/node/3
```
## Install PHP Filter Module
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In current versions it's no longer possible to install plugins by only having access to the web after the default installation.
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From version **8 onwards, the** [**PHP Filter**](https://www.drupal.org/project/php/releases/8.x-1.1) **module is not installed by default**. To leverage this functionality, we would have to **install the module ourselves**.
1. Download the most recent version of the module from the Drupal website.
1. `wget https://ftp.drupal.org/files/projects/php-8.x-1.1.tar.gz`
2. Once downloaded go to **`Administration`** > **`Reports`** > **`Available updates`**.
3. Click on **`Browse`**, select the file from the directory we downloaded it to, and then click **`Install`**.
4. Once the module is installed, we can click on **`Content`** and **create a new basic page**, similar to how we did in the Drupal 7 example. Again, be sure to **select `PHP code` from the `Text format` dropdown**.
## Backdoored Module
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In current versions it's no longer possible to install plugins by only having access to the web after the default installation.
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It was possible to **download** a **module**, add a **backdoor** to it and **install** it. For example, downloading [**Trurnstile**](https://www.drupal.org/project/turnstile) module in compressed format, creating a new PHP backdoor file inside of it, allowing the accessing of the PHP file with a `.htaccess` file:
```html
RewriteEngine On
RewriteBase /
```
And then going to **`http://drupal.local/admin/modules/install`** to install the backdoored module and access **`/modules/turnstile/back.php`** to execute it.
## Backdooring Drupal with Configuration synchronization
**Post shared by** [**Coiffeur0x90**](https://twitter.com/Coiffeur0x90)
### Part 1 (activation of _Media_ and _Media Library_)
In the _Extend_ menu (/admin/modules), you can activate what appear to be plugins already installed. By default, plugins _Media_ and _Media Library_ don’t appear to be activated, so let’s activate them.
Before activation:
After activation:
### Part 2 (leveraging feature _Configuration synchronization_)
We’ll leverage the _Configuration synchronization_ feature to dump (export) and upload (import) Drupal configuration entries:
* /admin/config/development/configuration/single/export
* /admin/config/development/configuration/single/import
**Patch system.file.yml**
Let’s start by patching the first entry `allow_insecure_uploads` from:
File: system.file.yml
```
...
allow_insecure_uploads: false
...
```
To:
File: system.file.yml
```
...
allow_insecure_uploads: true
...
```
**Patch field.field.media.document.field\_media\_document.yml**
Then, patch the second entry `file_extensions` from:
File: field.field.media.document.field\_media\_document.yml
```
...
file_directory: '[date:custom:Y]-[date:custom:m]'
file_extensions: 'txt rtf doc docx ppt pptx xls xlsx pdf odf odg odp ods odt fodt fods fodp fodg key numbers pages'
...
```
To:
File: field.field.media.document.field\_media\_document.yml
```
...
file_directory: '[date:custom:Y]-[date:custom:m]'
file_extensions: 'htaccess txt rtf doc docx ppt pptx xls xlsx pdf odf odg odp ods odt fodt fods fodp fodg key numbers pages'
...
```
> I don’t use it in this blogpost but it is noted that it is possible to define the entry `file_directory` in an arbitrary way and that it is vulnerable to a path traversal attack (so we can go back up within the Drupal filesystem tree).
### Part 3 (leveraging feature _Add Document_)
The last step is the simplest, and is broken down into two sub-steps. The first is to upload a file in .htaccess format to leverage the Apache directives and allow .txt files to be interpreted by the PHP engine. The second is to upload a .txt file containing our payload.
File: .htaccess
```
SetHandler application/x-httpd-php
# Vroum! Vroum!
# We reactivate PHP engines for all versions in order to be targetless.
php_flag engine on
php_flag engine on
php_flag engine on
```
Why is this trick cool?
Because once the Webshell (that we’ll call LICENSE.txt ) is dropped onto the Web server, we can transmit our commands via `$_COOKIE` and in the Web server logs, this will show up as a legitimate GET request to a text file.
Why name our Webshell LICENSE.txt?
Simply because if we take the following file, for example [core/LICENSE.txt](https://github.com/drupal/drupal/blob/11.x/core/LICENSE.txt) (which is already present in the Drupal core), we have a file of 339 lines and 17.6 KB in size, which is perfect for adding a small snippet of PHP code in the middle (since the file is big enough).
File: Patched LICENSE.txt
```txt
...
this License, you may choose any version ever published by the Free Software
Foundation.
10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
...
```
#### **Part 3.1 (upload file .htaccess)**
First, we leverage the _Add Document_ (/media/add/document) feature to upload our file containing the Apache directives (.htaccess).
**Part 3.2 (upload file LICENSE.txt)**
Then, we leverage the _Add Document_ (/media/add/document) feature again to upload a Webshell hidden within a license file.
### Part 4 (interaction with the Webshell)
The last part consists of interacting with the Webshell.
As shown in the following screenshot, if the cookie expected by our Webshell is not defined, we get the subsequent result when consulting the file via a Web browser.
When the attacker sets the cookie, he can interact with the Webshell and execute any commands he wants.
And as you can see in the logs, it looks like only a txt file has been requested.
Thank you for taking the time to read this article, I hope it will help you get some shells.
{% hint style="success" %}
Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\
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Support HackTricks
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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