Disassembling and patching iOS applications at assembly level

There are many mobile operating systems for different smartphones. iOS is one of them available exclusively on Apple devices. It offers various features such as GPS tracking, Siri, multi touch gestures, biometric authentication etc. The functionality of an iOS device can be expanded by installing third party applications, available from App store. Apple follows a mandatory code signing process to ensure that applications are developed by trusted enterprises/developers and no malware exists on App Store. However, past attacks on iOS devices such as ikee, Wirelurker have revealed that Apple's code signing process is not sufficient to ensure the security of its devices. Considering past attacks on iOS devices and with view of analyzing the behavior of iOS applications, this paper aims to describe how an analyst can perform reverse engineering of iOS applications by disassembling, decompiling and debugging application's code using Disassembler to discover the vulnerable areas.