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A macOS **installer package** (also known as a `.pkg` file) is a file format used by macOS to **distribute software**. These files are like a **box that contains everything a piece of software** needs to install and run correctly.
The package file itself is an archive that holds a **hierarchy of files and directories that will be installed on the target** computer. It can also include **scripts** to perform tasks before and after the installation, like setting up configuration files or cleaning up old versions of the software.
DMG files, or Apple Disk Images, are a file format used by Apple's macOS for disk images. A DMG file is essentially a **mountable disk image** (it contains its own filesystem) that contains raw block data typically compressed and sometimes encrypted. When you open a DMG file, macOS **mounts it as if it were a physical disk**, allowing you to access its contents.
The hierarchy of a DMG file can be different based on the content. However, for application DMGs, it usually follows this structure:
* Top Level: This is the root of the disk image. It often contains the application and possibly a link to the Applications folder.
* Application (.app): This is the actual application. In macOS, an application is typically a package that contains many individual files and folders that make up the application.
* Applications Link: This is a shortcut to the Applications folder in macOS. The purpose of this is to make it easy for you to install the application. You can drag the .app file to this shortcut to install the app.
If a pre or post installation script is for example executing from **`/var/tmp/Installerutil`**, and attacker could control that script so he escalate privileges whenever it's executed. Or another similar example:
This is a [public function](https://developer.apple.com/documentation/security/1540038-authorizationexecutewithprivileg) that several installers and updaters will call to **execute something as root**. This function accepts the **path** of the **file** to **execute** as parameter, however, if an attacker could **modify** this file, he will be able to **abuse** its execution with root to **escalate privileges**.
```bash
# Breakpoint in the function to check wich file is loaded
(lldb) b AuthorizationExecuteWithPrivileges
# You could also check FS events to find this missconfig
```
For more info check this talk: [https://www.youtube.com/watch?v=lTOItyjTTkw](https://www.youtube.com/watch?v=lTOItyjTTkw)
If an installer writes to `/tmp/fixedname/bla/bla`, it's possible to **create a mount** over `/tmp/fixedname` with noowners so you could **modify any file during the installation** to abuse the installation process.
An example of this is **CVE-2021-26089** which managed to **overwrite a periodic script** to get execution as root. For more information take a look to the talk: [**OBTS v4.0: "Mount(ain) of Bugs" - Csaba Fitzl**](https://www.youtube.com/watch?v=jSYPazD4VcE)
It's possible to just generate a **`.pkg`** file with **pre and post-install scripts** without any payload.
### JS in Distribution xml
It's possible to add **`<script>`** tags in the **distribution xml** file of the package and that code will get executed and it can **execute commands** using **`system.run`**:
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
