Overview

An .ipa file is an iPhone

IPhone

The iPhone is a line of Internet and multimedia-enabled smartphones marketed by Apple Inc. The first iPhone was unveiled by Steve Jobs, then CEO of Apple, on January 9, 2007, and released on June 29, 2007...

 application archive file which stores an iPhone app. It is usually encrypted with Apple's FairPlay

FairPlay

FairPlay is a digital rights management technology created by Apple Inc., based on technology created by the company Veridisc. FairPlay is built into the QuickTime multimedia software and used by the iPhone, iPod, iPad, Apple TV, iTunes, and iTunes Store and the App Store. Formerly, all songs in...

 DRM

Digital rights management

Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...

 technology. Each .ipa file is compressed with a binary for the ARM architecture

ARM architecture

ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...

 and can only be installed on an iPhone, iPod Touch

IPod Touch

The iPod Touch is a portable media player, personal digital assistant, handheld game console, and Wi-Fi mobile device designed and marketed by Apple Inc. The iPod Touch adds the multi-touch graphical user interface to the iPod line...

, or iPad

IPad

The iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and...

. Files with the .ipa extension can be uncompressed by changing the extension to .zip

ZIP (file format)

Zip is a file format used for data compression and archiving. A zip file contains one or more files that have been compressed, to reduce file size, or stored as is...

 and unzipping.

.ipa files cannot be installed on the iPhone Simulator because they do not contain a binary for the x86 architecture. To run applications on the simulator, original project files which can be opened using the Xcode

Xcode

Xcode is a suite of tools, developed by Apple, for developing software for Mac OS X and iOS. Xcode 4.2, the latest major version, is available on the Mac App Store for free for Mac OS X 10.7 , and on the Apple Developer Connection website for free to registered developers Xcode is a suite of tools,...

 SDK are required.

Vulnerabilities

An unsigned .ipa can be created by copying the file with the extension .app

APP (file format)

APP is an abbreviation for application. The filename extension .app means application in Symbian OS, SkyOS, GNUstep and Mac OS X.On the latter two systems, a .app file is actually a folder containing binaries and supporting files....

 from the Products folder of the application in Xcode to a folder called Payload and compressing the latter using the command

zip -9 -y -r myAppName.ipa Payload/

It is then possible to install unsigned .ipa files on jailbroken devices using third party software like Appsync.

Structure of the IPA

An IPA has a built-in structure for iTunes

ITunes

iTunes is a media player computer program, used for playing, downloading, and organizing digital music and video files on desktop computers. It can also manage contents on iPod, iPhone, iPod Touch and iPad....

 and AppStore to recognize,
The example below shows the structure of an IPA:

/Payload/

/Payload/Application.app

/iTunesArtwork

/iTunesMetadata.plist


As shown above, the Payload folder is what contains all the app data. The iTunes Artwork file is either a 512x512 pixel PNG image, containing the app's icon for showing in iTunes

ITunes

iTunes is a media player computer program, used for playing, downloading, and organizing digital music and video files on desktop computers. It can also manage contents on iPod, iPhone, iPod Touch and iPad....

 and the App Store app on the iPad

IPad

The iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and...

. The iTunesMetadata.plist contains various bits of information, ranging from the developer's name and ID (e.g., Google), the bundle identifier, copyright information, genre, the name of the app, release date, purchase date, etc.