Applications the user can access run as the **mobile** user while critical system processes run as **root**.
However, the sandbox allows better control over actions that processes and applications can perform.
For example, even if two processes run as the same user \(mobile\), they are **not allowed to access or modify each other's data**.
Each application is installed under **`private/var/mobile/Applications/{random ID}`**
Once installed, applications have limited read access to some system areas and functions \(SMS, phone call...\). If an application wants to access a **protected area,** a **pop-up requesting permission** appears.
## Jailbreaking
Apple strictly requires that the code running on the iPhone must be **signed by a certificate issued by Apple**. **Jailbreaking** is the process of actively **circumventing such restrictions** and other security controls put in places by the OS. Therefore, once the device is jailbroken, the **integrity check** which is responsible for checking apps being installed is patched so it is **bypassed**.
{% hint style="info" %}
Unlike Android, **you cannot switch to "Developer Mode"** in iOS to run unsigned/untrusted code on the device.
{% endhint %}
The most important side effect of Jailbreaking is that it **removes any sandboxing put in place by the OS**. Therefore, any **app on the device can read any file** on the filesystem, including other apps files, cookies and keychain.
A jailbroken device allows users to **install unapproved apps** and leverage **more APIs**, which otherwise aren't accessible.
There are 2 types of jailbreaks:
* **Tethered**: Temporary jailbreak that requires the device to be connected to a computer every-time the device needs a restart. The jailbreak is reversed otherwise.
* **Untethered**: Rebooting the device does not reset the jailbreak.
**For regular users it's not recommended to jailbreak the mobile.
Note also that updating the OS removes the effect of jailbreaking.**
## **Simulator**
All the tools required to build and support an iOS app are **only officially supported on Mac OS**.
Apple's de facto tool for creating/debugging/instrumenting iOS applications is **Xcode**. It can be used to download other components such as **simulators** and different **SDK****versions** required to build and **test** your app.
It's highly recommended to **download** Xcode from the **official app store**. Other versions may be carrying malware.
The simulator files can be found in `/Users/<username>/Library/Developer/CoreSimulator/Devices`
To open the simulator, run Xcode, then press in the _Xcode tab_ -->_Open Developer tools_ -->_Simulator_
In the following image clicking in "iPod touch \[...\]" you can select other device to test in:
A **provisioning identity** is a collection of public and private keys that are associated an Apple developer account. In order to **sign apps** you need to pay **99$/year** to register in the **Apple Developer Program** to get your provisioning identity. Without this you won't be able to run applications from the source code in a physical device. Another option to do this is to use a **jailbroken device**.
Starting in Xcode 7.2 Apple has provided an option to create a **free iOS development provisioning profile** that allows to write and test your application on a real iPhone. Go to _Xcode_ -->_Preferences_ -->_Accounts_ -->_+_ \(Add new Appli ID you your credentials\) -->_Click on the Apple ID created_ -->_Manage Certificates_ -->_+_ \(Apple Development\) -->_Done_
Then, in order to run your application in your iPhone you need first to **indicate the iPhone to trust the computer.** Then, you can try to **run the application in the mobile from Xcode,** but and error will appear. So go to _Settings_ -->_General_ -->_Profiles and Device Management_ --> Select the untrusted profile and click "**Trust**".
Note that **applications signed by the same signing certificate can share resources on a secure manner, like keychain items**.
## Obfuscation
Unlike an Android Application, the binary of an iOS app **can only be disassembled** and not decompiled.
When an application is submitted to the app store, Apple first verifies the app conduct and before releasing it to the app-store, **Apple encrypts the binary**. So the binary download from the app store is encrypted complicating ting the reverse-engineering tasks.
However, note that there are other **third party software that can be used to obfuscate** the resulting binaries.
Starting in iOS version 8.4, Apple has **restricted the third-party managers to access to the application sandbox**, so tools like iFunbox and iExplorer no longer display/retrieve files from apps installed on the device if the device isn't jailbroken.
