What is the format of ipa?

ipa is the Apple application file format. The ipa file is essentially a zip compressed package, containing 3 components: 1. The app directory under the payload directory, which is the main program of the software; 2. iTunesArtwork, which is essentially a png image without a suffix, used to display in iTunes Icon; 3. iTunesMetadata.plist, used to record buyer information, selling price and other data.

#The operating environment of this tutorial: IOS15 system, iphone12 mobile phone.

IPA is the abbreviation of Apple application file iPhoneApplication and is the Apple application file format.

ipa file is essentially a zip compressed package (not a rar or 7z package), containing 3 components: the .app directory under the payload directory, which is the main program of the software; iTunesArtwork, which is essentially a PNG images without suffix are used to display icons in iTunes; iTunesMetadata.plist records buyer information, selling price and other data.

Since the zip package cannot record information such as permissions and owners, Apple stipulates the installation method of ipa, that is, all ipa will be unpacked and installed in the /var/mobile/Applications directory, and all files and directories will The owner and user group are both set to mobile (ID is 501), the permissions of the main program (executable file) are set to 0755 (everyone can execute it, but only the owner can modify it), and the executable file is defined in the plist. All directory permissions are set to 0755, and all other files are set to 0644 (only the owner can modify, others can only read, and no one is allowed to execute).

ipa is not placed directly in the Applications directory after unpacking, but in a directory composed of a string of random codes. Its function is to only allow this software to run in a specific sandbox (Sandbox) , and cannot interfere with other software. Therefore, under the random code directory, in addition to the three components of the ipa itself, there are three directories: Library, which is generally used to store data such as setting files; Documents, which stores data and is mostly used to save archives; tmp, which is a temporary folder. .

Since this software can only run in this specific directory (of course, some programs will call the system's address book, camera and other components, but they are still restricted), thus ensuring the security of the entire system sex and stability.

Since the regulations on permissions under the Unix system are very strict, "exceeding authority" behavior is absolutely not allowed. For example, mobile users do not have the permission to delete files owned by root because root has higher permissions than mobile. Therefore, when some people modify the files after ipa installation, such as Chineseizing or modifying the archive, they find that the clean software cannot be deleted or cannot be saved. This is because all root files cannot be deleted during deletion, and the program itself cannot archive all root files. File writing operation.

Three ios signatures

The ipa file needs to be installed, so a process of signing and then distributing is required. The specific ways to install the ipa file are: The following types: There are currently three iOS signatures on the market to choose from, iOS enterprise signature, super signature and Apple TF signature. However, please note that after iOS signature, the application needs to be distributed before it can be downloaded.

1. Apple Enterprise Signature

This is the first choice for most customers. Its biggest advantage is its cost-effectiveness and features, that is, it does not limit the number of update downloads. However, Apple Enterprise Signature will have the phenomenon of losing signatures. When choosing to cooperate, it is more reliable to choose a formal platform. The formal platform will divide the versions to ensure that the price of classified signatures is proportional to the stability. The higher the price of the version, the application of certificate signature The less, the higher the stability.

2. ios Super Signature

Because the personal developer account used by Super Signature can only connect to 100 udids, the cost is higher and is charged according to the download volume. It is difficult for most App operators to accept it. If you have your own personal developer account, building a super signature system is a good way.

3. Apple TF signature

As an Apple internal testing method officially recognized by Apple, it is directly distributed to users for installation through the Apple internal testing store testflight. Apple’s official link, you don’t have to worry about being blocked when distributing it, it’s safe and risk-free, and its stability is the better among the three signature methods. However, there is an operation that requires downloading testflight. It does not require a direct and trusted download like a corporate signature. Its operation process is more like downloading an app from the app store.

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