Authenticate once and share data between multiple application

Open file SharedOne > Onboarding > OnboardingManager.swift and locate method configuredStoreManagerStep()

Replace the following line:

let step = StoreManagerStep()

with this:

let keychainGroupName: String = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
let uuid:UUID = UUID(uuidString: "ec429dd6-3fd1-4556-b600-bac39ee9f6e7")!

let storeManager = KeychainStoreManager(keychainAccessGroup: keychainGroupName)

let step = StoreManagerStep(persistentStoreManager: storeManager)
step.runRestoreIfStoreExists = true
step.storeID = uuid

With this code, the following is happening:

1. The keychainGroupName variable contains the value specified in the project’s App Groups entitlement. Along with the uuid, these are used to support the shared key store between applications.
2. The KeychainStoreManager is then initialized with the specified keychainGroupName and stored in constant storeManager.
3. The StoreManagerStep is then initialized with the storeManager as the persistent store manager.
4. When using a shared store, you don’t want an error thrown when a store is created which is already been created by a different app. To bypass this behavior of the step, flag runRestoreIfStoreExists should be set to true.
5. In order to share the same store ID, the step’s storeID is set to a hard-coded uuid value.

Open the Xcode project for the first app SharedOne, and open AppDelegate.swift file.

Add the following method:

func storeData() {
    let storeName      = "MyStore"
    let cipherPassword = "1qaz@WSX"
    let cipherSalt     = "mySalt"
    let keychainGroup  = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
    let key            = "myKey"

    let data = "String saved from SharedOne".data(using: .utf8)

    do {
        let cipher = try Cipher (password: cipherPassword, salt: cipherSalt)
        let keychainStorage = try KeychainStorage.openStore (name: storeName, cipher: cipher, accessGroup: keychainGroup)
        try keychainStorage.put (data: data!, for: key)
    } catch let error {
        self.logger.error("Store opening failed!", error: error)
    }

}

This method opens a store with the provided name and cipher for the predefined keychainGroupName, and stores a Data object data (which holds a simple string encoded using UTF-8) with key myKey.

Next, locate method application(_:didFinishLaunchingWithOptions:) and just above the bottom return statement, add:

storeData()

Switch to the Xcode project for the second app SharedTwo, and open AppDelegate.swift file.

Add the following method:

func retrieveData() {
    let storeName      = "MyStore"
    let cipherPassword = "1qaz@WSX"
    let cipherSalt     = "mySalt"
    let keychainGroup  = "group.com.sap.tutorials.demoapp.sharedkeychaingroup"
    let key            = "myKey"

    do {
        let cipher = try Cipher (password: cipherPassword, salt: cipherSalt)
        let keychainStorage = try KeychainStorage.openStore (name: storeName, cipher: cipher, accessGroup: keychainGroup)

        let data = try keychainStorage.data(for: key)
        let dataString = String(data: data!, encoding: .utf8)

        logger.info("Data retrieved : \(String(describing: dataString))")
    } catch let error {
        logger.error("Store opening failed!", error: error)
    }

}

Similar to the code used in the first app SharedOne, this method opens a store with the provided name and cipher for the predefined keychainGroupName. But in this case, it now loads a Data object data for key myKey (which is then decoded using UTF-8 into constant dataString).

The decoded content is then printed to the console using the logger.

Next, locate method application(_:didFinishLaunchingWithOptions:) and at the top of that method, add:

logger.logLevel = .info

This ensures the info logging of method retrieveData() will be printed to the console.

Finally, just above the bottom return statement, add:

retrieveData()