MASTG-TECH-0056: Installing Apps

When you install an application without using Apple's App Store, this is called sideloading. There are various ways of sideloading which are described below. On the iOS device, the actual installation process is then handled by the installd daemon, which will unpack and install the application. To integrate app services or be installed on an iOS device, all applications must be signed with a certificate issued by Apple. This means that the application can be installed only after successful code signature verification. On a jailbroken phone, however, you can circumvent this security feature with AppSync, a package available in the Cydia store. It contains numerous useful applications that leverage jailbreak-provided root privileges to execute advanced functionality. AppSync is a tweak that patches installd, allowing the installation of fake-signed IPA packages.

Different methods exist for installing an IPA package onto an iOS device, which are described in detail below.

Please note that iTunes is no longer available in macOS Catalina. If you are using an older version of macOS, iTunes is still available but since iTunes 12.7 it is not possible to install apps.

Sideloadly

Sideloadly is a GUI tool that can automate all required steps for you. It requires valid Apple developer credentials, as it will obtain a valid signature from Apple servers.

Do not use your personal Apple account

To sign an IPA file, you will need a valid iOS developer account, either free or paid. Both types come with certain restrictions, as explained on the Sideloadly website. We recommend creating a dedicated developer account for signing test applications, and not using your personal Apple account.

libimobiledevice

On Linux and also macOS, you can alternatively use libimobiledevice, a cross-platform software protocol library and a set of tools for native communication with iOS devices. This allows you to install apps over a USB connection by executing ideviceinstaller. The connection is implemented with the USB multiplexing daemon usbmuxd, which provides a TCP tunnel over USB.

The package for libimobiledevice will be available in your Linux package manager. On macOS you can install libimobiledevice via brew:

brew install libimobiledevice
brew install ideviceinstaller

If you have any issues, try installing the libraries from source, as the precompiled version may be outdated.

After the installation you have several new command line tools available, such as ideviceinfo, ideviceinstaller or idevicedebug. Let's install and debug the iGoat-Swift app with the following commands:

# The following command will show detailed information about the iOS device connected via USB.
$ ideviceinfo
# The following command will install the IPA to your iOS device.
$ ideviceinstaller -i iGoat-Swift_v1.0-frida-codesigned.ipa
...
Install: Complete
# The following command will start the app in debug mode, by providing the bundle name. The bundle name can be found in the previous command after "Installing".
$ idevicedebug -d run OWASP.iGoat-Swift

ipainstaller

The IPA can also be directly installed on the iOS device via the command line with ipainstaller. After copying the file over to the device, for example via scp, you can execute ipainstaller with the IPA's filename:

ipainstaller App_name.ipa

ios-deploy

On macOS you can also use the ios-deploy tool to install iOS apps from the command line. You'll need to unzip your IPA since ios-deploy uses the app bundles to install apps.

unzip Name.ipa
ios-deploy --bundle 'Payload/Name.app' -W -d -v

After the app is installed on the iOS device, you can simply start it by adding the -m flag which will directly start debugging without installing the app again.

ios-deploy --bundle 'Payload/Name.app' -W -d -v -m

Xcode

It is also possible to use the Xcode IDE to install iOS apps by doing the following steps:

1. Start Xcode
2. Select Window/Devices and Simulators
3. Select the connected iOS device and click on the + sign in Installed Apps.

Allow Application Installation on a Non-iPad Device

Sometimes an application can require to be used on an iPad device. If you only have iPhone or iPod touch devices then you can force the application to accept to be installed and used on these kinds of devices. You can do this by changing the value of the property UIDeviceFamily to the value 1 in the Info.plist file.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>

  <key>UIDeviceFamily</key>
  <array>
    <integer>1</integer>
  </array>

</dict>
</plist>  

It is important to note that changing this value will break the original signature of the IPA file so you need to re-sign the IPA, after the update, in order to install it on a device on which the signature validation has not been disabled.

This bypass might not work if the application requires capabilities that are specific to modern iPads while your iPhone or iPod is a bit older.

Possible values for the property UIDeviceFamily can be found in the Apple Developer documentation.

One fundamental step when analyzing apps is information gathering. This can be done by inspecting the app package on your host computer or remotely by accessing the app data on the device. You'll find more advance techniques in the subsequent chapters but, for now, we will focus on the basics: getting a list of all installed apps, exploring the app package and accessing the app data directories on the device itself. This should give you a bit of context about what the app is all about without even having to reverse engineer it or perform more advanced analysis. We will be answering questions such as:

• Which files are included in the package?
• Which Frameworks does the app use?
• Which capabilities does the app require?
• Which permissions does the app request to the user and for what reason?
• Does the app allow any unsecured connections?
• Does the app create any new files when being installed?