Authentication and Authorization in Swift: LocalAuthentication, Firebase Auth, Keychain

Authentication and Authorization in Swift (iOS/macOS): Overview of Tools and Libraries

In modern iOS/macOS development, security and access control are critically important aspects. Swift provides both built-in frameworks for local authentication and integration with cloud services. In this article, we will cover the main tools and libraries for implementing login, registration, and user permission verification.

1. LocalAuthentication — Face ID / Touch ID / Apple Watch

The LocalAuthentication framework allows you to authenticate a user via biometrics or device passcode. It works on iOS and macOS.

Main Features:

• Checking biometric availability (Face ID, Touch ID)
• Authentication with context (LAContext)
• Using the device passcode as a fallback option

Code Example:

import LocalAuthentication

func authenticateUser(completion: @escaping (Bool, Error?) -> Void) {    let context = LAContext()    var error: NSError?

    // Check if biometrics are available    guard context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error) else {        completion(false, error)        return    }

    // Start authentication    context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics,                           localizedReason: "Confirm your identity to access data") { success, authError in        DispatchQueue.main.async {            completion(success, authError)        }    }}

2. Firebase Authentication — Cloud Authentication

Firebase Auth is a powerful library that supports login via email/password, Google, Apple, GitHub, and other providers. It is ideal for server-based applications.

Installation via Swift Package Manager:

// In Package.swift add:// .package(url: "https://github.com/firebase/firebase-ios-sdk.git", from: "10.0.0")// target: "YourAppTarget", dependencies: ["FirebaseAuth"]

Registering a New User:

import FirebaseAuth

func signUp(email: String, password: String) {    Auth.auth().createUser(withEmail: email, password: password) { authResult, error in        if let error = error {            print("Registration error: \\(error.localizedDescription)")            return        }        print("User registered: \\(authResult?.user.uid ?? "")")    }}

Signing In an Existing User:

func signIn(email: String, password: String) {    Auth.auth().signIn(withEmail: email, password: password) { authResult, error in        if let error = error {            print("Login error: \\(error.localizedDescription)")            return        }        print("Login successful: \\(authResult?.user.email ?? "")")    }}

3. Keychain Services — Secure Token Storage

To store JWT tokens, passwords, or keys, use Keychain. This is a native iOS/macOS mechanism.

Example of Saving and Reading:

import Security

func saveToKeychain(key: String, data: Data) -> Bool {    let query: [String: Any] = [        kSecClass as String: kSecClassGenericPassword,        kSecAttrAccount as String: key,        kSecValueData as String: data    ]    SecItemDelete(query as CFDictionary)    let status = SecItemAdd(query as CFDictionary, nil)    return status == errSecSuccess}

func readFromKeychain(key: String) -> Data? {    let query: [String: Any] = [        kSecClass as String: kSecClassGenericPassword,        kSecAttrAccount as String: key,        kSecReturnData as String: true,        kSecMatchLimit as String: kSecMatchLimitOne    ]    var result: AnyObject?    let status = SecItemCopyMatching(query as CFDictionary, &