hacktricks/macos-hardening/macos-security-and-privilege-escalation/mac-os-architecture/macos-kernel-extensions.md

# macOS Kernel Extensions

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## Basic Information

Kernel extensions (Kexts) are **packages** with a **`.kext`** extension that are **loaded directly into the macOS kernel space**, providing additional functionality to the main operating system.

### Requirements

Obviously, this is so powerful that it is **complicated to load a kernel extension**. These are the **requirements** that a kernel extension must meet to be loaded:

* When **entering recovery mode**, kernel **extensions must be allowed** to be loaded:

<figure><img src="../../../.gitbook/assets/image (2) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1) (1).png" alt=""><figcaption></figcaption></figure>

* The kernel extension must be **signed with a kernel code signing certificate**, which can only be **granted by Apple**. Who will review in detail the company and the reasons why it is needed.
* The kernel extension must also be **notarized**, Apple will be able to check it for malware.
* Then, the **root** user is the one who can **load the kernel extension** and the files inside the package must **belong to root**.
* During the upload process, the package must be prepared in a **protected non-root location**: `/Library/StagedExtensions` (requires the `com.apple.rootless.storage.KernelExtensionManagement` grant).
* Finally, when attempting to load it, the user will [**receive a confirmation request**](https://developer.apple.com/library/archive/technotes/tn2459/\_index.html) and, if accepted, the computer must be **restarted** to load it.

### Loading process

In Catalina it was like this: It is interesting to note that the **verification** process occurs in **userland**. However, only applications with the **`com.apple.private.security.kext-management`** grant can **request the kernel to load an extension**: `kextcache`, `kextload`, `kextutil`, `kextd`, `syspolicyd`

1. **`kextutil`** cli **starts** the **verification** process for loading an extension
   * It will talk to **`kextd`** by sending using a **Mach service**.
2. **`kextd`** will check several things, such as the **signature**
   * It will talk to **`syspolicyd`** to **check** if the extension can be **loaded**.
3. **`syspolicyd`** will **prompt** the **user** if the extension has not been previously loaded.
   * **`syspolicyd`** will report the result to **`kextd`**
4. **`kextd`** will finally be able to **tell the kernel to load** the extension

If **`kextd`** is not available, **`kextutil`** can perform the same checks.

## Referencias

* [https://www.makeuseof.com/how-to-enable-third-party-kernel-extensions-apple-silicon-mac/](https://www.makeuseof.com/how-to-enable-third-party-kernel-extensions-apple-silicon-mac/)
* [https://www.youtube.com/watch?v=hGKOskSiaQo](https://www.youtube.com/watch?v=hGKOskSiaQo)

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<summary><strong>Learn AWS hacking from zero to hero with</strong> <a href="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>

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* Descubre [**The PEASS Family**](https://opensea.io/collection/the-peass-family), nuestra colección exclusiva de [**NFTs**](https://opensea.io/collection/the-peass-family)
* Obtén el [**swag oficial de PEASS y HackTricks**](https://peass.creator-spring.com)
* **Únete al** [**💬**](https://emojipedia.org/speech-balloon/) **grupo de Discord** o al [**grupo de telegram**](https://t.me/peass) o **sígueme** en **Twitter** 🐦[**@carlospolopm**](https://twitter.com/hacktricks\_live).
* **Comparte tus trucos de hacking enviando PR a** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **y** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).

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