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 %}

Root in Android Comparison

iOS jailbreaking is often compared to Android rooting, but the process is actually quite different. To explain the difference, we'll first review the concepts of "rooting" and "flashing" on Android.

Rooting: This typically involves installing the su binary on the system or replacing the whole system with a rooted custom ROM. Exploits aren't required to obtain root access as long as the bootloader is accessible.
Flashing custom ROMs: This allows you to replace the OS that's running on the device after you unlock the bootloader. The bootloader may require an exploit to unlock it.

On iOS devices, flashing a custom ROM is impossible because the iOS bootloader only allows Apple-signed images to be booted and flashed. This is why even official iOS images can't be installed if they aren't signed by Apple, and it makes iOS downgrades only possible for as long as the previous iOS version is still signed.

The purpose of jailbreaking is to disable iOS protections Apple's code signing mechanisms in particular so that arbitrary unsigned code can run on the device e.g. custom code or downloaded from alternative app stores such as Cydia or Sileo. The word "jailbreak" is a colloquial reference to all-in-one tools that automate the disabling process.

Jailbreaking Considerations

Jailbreaking an iOS device is becoming more and more complicated because Apple keeps hardening the system and patching the exploited vulnerabilities. Jailbreaking has become a very time-sensitive procedure because Apple stops signing these vulnerable versions relatively soon after releasing a fix unless the jailbreak benefits from hardware-based vulnerabilities, such as the [limera1n exploit](https://www.theiphonewiki.com/wiki/Limera1n) affecting the BootROM of the iPhone 4 and iPad 1. This means that you can't downgrade to a specific iOS version once Apple stops signing the firmware.

If you have a jailbroken device that you use for security testing, keep it as is unless you're 100% sure that you can re-jailbreak it after upgrading to the latest iOS version.

iOS upgrades are based on a challenge-response process generating the so-called SHSH blobs as a result. The device will allow the OS installation only if the response to the challenge is signed by Apple. This is what researchers call a "signing window", and it is the reason you can't simply store the OTA firmware package you downloaded and load it onto the device whenever you want to. During minor iOS upgrades, two versions may both be signed by Apple the latest one, and the previous iOS version. This is the only situation in which you can downgrade the iOS device. You can check the current signing window and download OTA firmware from the IPSW Downloads website.

{% hint style="danger" %} Updating the OS removes the effect of jailbreaking. {% endhint %}

Jailbreak Types

Tethered jailbreaks don't persist through reboots, so re-applying jailbreaks requires the device to be connected tethered to a computer during every reboot. The device may not reboot at all if the computer is not connected.
Semi-tethered jailbreaks can't be re-applied unless the device is connected to a computer during reboot. The device can also boot into non-jailbroken mode on its own.
Semi-untethered jailbreaks allow the device to boot on its own, but the kernel patches or user-land modifications for disabling code signing aren't applied automatically. The user must re-jailbreak the device by starting an app or visiting a website not requiring a connection to a computer, hence the term untethered.
Untethered jailbreaks are the most popular choice for end users because they need to be applied only once, after which the device will be permanently jailbroken.

Jailbreaking Tool

Different iOS versions require different jailbreaking techniques. Determine whether a public jailbreak is available for your version of iOS. Beware of fake tools and spyware, which are often hiding behind domain names that are similar to the name of the jailbreaking group/author.

The iOS jailbreak scene evolves so rapidly that providing up-to-date instructions is difficult. However, we can point you to some sources that are currently reliable.

Note that any modification you make to your device is at your own risk. While jailbreaking is typically safe, things can go wrong and you may end up bricking your device. No other party except yourself can be held accountable for any damage.

Benefits

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.

{% hint style="warning" %} It's not recommended to jailbreak the mobile for regular users {% endhint %}

After Jailbreaking

{% page-ref page="basic-ios-testing-operations.md" %}

Jailbreak Detection

Several applications will try to detect if the mobile is jailbroken and in that case the application won't run

After jailbreaking an iOS files and folders are usually installed, these can be searched to determine if the device is jailbroken.
In a jailbroken device applications get read/write access to new files outside the sandbox
Some API calls will behave differently
The presence of the OpenSSH service
Calling /bin/sh will return 1 instead of 0

More information about how to detect jailbreaking here.

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