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AppAuth for iOS and macOS Build Status Carthage compatible

AppAuth for iOS and macOS is a client SDK for communicating with OAuth 2.0 and OpenID Connect providers. It strives to directly map the requests and responses of those specifications, while following the idiomatic style of the implementation language. In addition to mapping the raw protocol flows, convenience methods are available to assist with common tasks like performing an action with fresh tokens.

It follows the best practices set out in RFC 8252 - OAuth 2.0 for Native Apps including using SFAuthenticationSession and SFSafariViewController on iOS for the auth request. UIWebView and WKWebView are explicitly not supported due to the security and usability reasons explained in Section 8.12 of RFC 8252.

It also supports the PKCE extension to OAuth, which was created to secure authorization codes in public clients when custom URI scheme redirects are used. The library is friendly to other extensions (standard or otherwise), with the ability to handle additional params in all protocol requests and responses.

Specification

iOS

Supported Versions

AppAuth supports iOS 7 and above.

iOS 9+ uses the in-app browser tab pattern (via SFSafariViewController), and falls back to the system browser (mobile Safari) on earlier versions.

Authorization Server Requirements

Both Custom URI Schemes (all supported versions of iOS) and Universal Links (iOS 9+) can be used with the library.

In general, AppAuth can work with any authorization server that supports native apps, as documented in RFC 8252, either through custom URI scheme redirects, or universal links. Authorization servers that assume all clients are web-based, or require clients to maintain confidentiality of the client secrets may not work well.

macOS

Supported Versions

AppAuth supports macOS (OS X) 10.9 and above.

Authorization Server Requirements

AppAuth for macOS supports both custom schemes; a loopback HTTP redirects via a small embedded server.

In general, AppAuth can work with any authorization server that supports native apps, as documented in RFC 8252; either through custom URI schemes, or loopback HTTP redirects. Authorization servers that assume all clients are web-based, or require clients to maintain confidentiality of the client secrets may not work well.

Try

Want to try out AppAuth? Just run:

pod try AppAuth

Follow the instructions in Examples/README.md to configure with your own OAuth client (you need to update three configuration points with your client info to try the demo).

Setup

AppAuth supports three options for dependency management.

CocoaPods

With CocoaPods, add the following line to your Podfile:

pod 'AppAuth'

Then, run pod install.

Carthage

With Carthage, add the following line to your Cartfile:

github "openid/AppAuth-iOS" "master"

Then, run carthage bootstrap.

Static Library

You can also use AppAuth as a static library. This requires linking the library and your project, and including the headers. Here is a suggested configuration:

  1. Create an Xcode Workspace.
  2. Add AppAuth.xcodeproj to your Workspace.
  3. Include libAppAuth as a linked library for your target (in the "General -> Linked Framework and Libraries" section of your target).
  4. Add AppAuth-iOS/Source to your search paths of your target ("Build Settings -> "Header Search Paths").

Auth Flow

AppAuth supports both manual interaction with the authorization server where you need to perform your own token exchanges, as well as convenience methods that perform some of this logic for you. This example uses the convenience method, which returns either an OIDAuthState object, or an error.

OIDAuthState is a class that keeps track of the authorization and token requests and responses, and provides a convenience method to call an API with fresh tokens. This is the only object that you need to serialize to retain the authorization state of the session.

Configuration

You can configure AppAuth by specifying the endpoints directly:

Objective-C

NSURL *authorizationEndpoint =
    [NSURL URLWithString:@"https://accounts.google.com/o/oauth2/v2/auth"];
NSURL *tokenEndpoint =
    [NSURL URLWithString:@"https://www.googleapis.com/oauth2/v4/token"];

OIDServiceConfiguration *configuration =
    [[OIDServiceConfiguration alloc]
        initWithAuthorizationEndpoint:authorizationEndpoint
                        tokenEndpoint:tokenEndpoint];

// perform the auth request...

Swift

let authorizationEndpoint = URL(string: "https://accounts.google.com/o/oauth2/v2/auth")!
let tokenEndpoint = URL(string: "https://www.googleapis.com/oauth2/v4/token")!
let configuration = OIDServiceConfiguration(authorizationEndpoint: authorizationEndpoint,
                                            tokenEndpoint: tokenEndpoint)

// perform the auth request...

Or through discovery:

Objective-C

NSURL *issuer = [NSURL URLWithString:@"https://accounts.google.com"];

[OIDAuthorizationService discoverServiceConfigurationForIssuer:issuer
    completion:^(OIDServiceConfiguration *_Nullable configuration,
                 NSError *_Nullable error) {

  if (!configuration) {
    NSLog(@"Error retrieving discovery document: %@",
          [error localizedDescription]);
    return;
  }

  // perform the auth request...
}];

Swift

let issuer = URL(string: "https://accounts.google.com")!

// discovers endpoints
OIDAuthorizationService.discoverConfiguration(forIssuer: issuer) { configuration, error in
  guard let config = configuration else {
    print("Error retrieving discovery document: \(error?.localizedDescription ?? "Unknown error")")
    return
  }

  // perform the auth request...
}

Authorizing – iOS

First, you need to have a property in your UIApplicationDelegate implementation to hold the session, in order to continue the authorization flow from the redirect. In this example, the implementation of this delegate is a class named AppDelegate, if your app's application delegate has a different name, please update the class name in samples below accordingly.

Objective-C

@interface AppDelegate : UIResponder <UIApplicationDelegate>
// property of the app's AppDelegate
@property(nonatomic, strong, nullable) id<OIDExternalUserAgentSession> currentAuthorizationFlow;
@end

Swift

class AppDelegate: UIResponder, UIApplicationDelegate {
  // property of the app's AppDelegate
  var currentAuthorizationFlow: OIDExternalUserAgentSession?
}

And your main class, a property to store the auth state:

Objective-C

// property of the containing class
@property(nonatomic, strong, nullable) OIDAuthState *authState;

Swift

// property of the containing class
private var authState: OIDAuthState?

Then, initiate the authorization request. By using the authStateByPresentingAuthorizationRequest convenience method, the token exchange will be performed automatically, and everything will be protected with PKCE (if the server supports it). AppAuth also lets you perform these requests manually. See the authNoCodeExchange method in the included Example app for a demonstration:

Objective-C

// builds authentication request
OIDAuthorizationRequest *request =
    [[OIDAuthorizationRequest alloc] initWithConfiguration:configuration
                                                  clientId:kClientID
                                                    scopes:@[OIDScopeOpenID,
                                                             OIDScopeProfile]
                                               redirectURL:kRedirectURI
                                              responseType:OIDResponseTypeCode
                                      additionalParameters:nil];

// performs authentication request
AppDelegate *appDelegate =
    (AppDelegate *)[UIApplication sharedApplication].delegate;
appDelegate.currentAuthorizationFlow =
    [OIDAuthState authStateByPresentingAuthorizationRequest:request
        presentingViewController:self
                        callback:^(OIDAuthState *_Nullable authState,
                                   NSError *_Nullable error) {
  if (authState) {
    NSLog(@"Got authorization tokens. Access token: %@",
          authState.lastTokenResponse.accessToken);
    [self setAuthState:authState];
  } else {
    NSLog(@"Authorization error: %@", [error localizedDescription]);
    [self setAuthState:nil];
  }
}];

Swift

// builds authentication request
let request = OIDAuthorizationRequest(configuration: configuration,
                                      clientId: clientID,
                                      clientSecret: clientSecret,
                                      scopes: [OIDScopeOpenID, OIDScopeProfile],
                                      redirectURL: redirectURI,
                                      responseType: OIDResponseTypeCode,
                                      additionalParameters: nil)

// performs authentication request
print("Initiating authorization request with scope: \(request.scope ?? "nil")")

let appDelegate = UIApplication.shared.delegate as! AppDelegate

appDelegate.currentAuthorizationFlow =
    OIDAuthState.authState(byPresenting: request, presenting: self) { authState, error in
  if let authState = authState {
    self.setAuthState(authState)
    print("Got authorization tokens. Access token: " +
          "\(authState.lastTokenResponse?.accessToken ?? "nil")")
  } else {
    print("Authorization error: \(error?.localizedDescription ?? "Unknown error")")
    self.setAuthState(nil)
  }
}

Handling the Redirect

The authorization response URL is returned to the app via the iOS openURL app delegate method, so you need to pipe this through to the current authorization session (created in the previous session):

Objective-C

- (BOOL)application:(UIApplication *)app
            openURL:(NSURL *)url
            options:(NSDictionary<NSString *, id> *)options {
  // Sends the URL to the current authorization flow (if any) which will
  // process it if it relates to an authorization response.
  if ([_currentAuthorizationFlow resumeExternalUserAgentFlowWithURL:url]) {
    _currentAuthorizationFlow = nil;
    return YES;
  }

  // Your additional URL handling (if any) goes here.

  return NO;
}

Swift

func application(_ app: UIApplication,
                 open url: URL,
                 options: [UIApplicationOpenURLOptionsKey : Any] = [:]) -> Bool {
  // Sends the URL to the current authorization flow (if any) which will
  // process it if it relates to an authorization response.
  if let authorizationFlow = self.currentAuthorizationFlow,
                             authorizationFlow.resumeExternalUserAgentFlow(with: url) {
    self.currentAuthorizationFlow = nil
    return true
  }

  // Your additional URL handling (if any)

  return false
}

Authorizing – MacOS

On macOS, the most popular way to get the authorization response redirect is to start a local HTTP server on the loopback interface (limited to incoming requests from the user's machine only). When the authorization is complete, the user is redirected to that local server, and the authorization response can be processed by the app. AppAuth takes care of managing the local HTTP server lifecycle for you.

💡 Alternative: Custom URI Schemes

Custom URI schemes are also supported on macOS, but some browsers display an interstitial, which reduces the usability. For an example on using custom URI schemes with macOS, See Example-Mac.

To receive the authorization response using a local HTTP server, first you need to have an instance variable in your main class to retain the HTTP redirect handler:

Objective-C

OIDRedirectHTTPHandler *_redirectHTTPHandler;

Then, as the port used by the local HTTP server varies, you need to start it before building the authorization request, in order to get the exact redirect URI to use:

Objective-C

static NSString *const kSuccessURLString =
    @"http://openid.github.io/AppAuth-iOS/redirect/";
NSURL *successURL = [NSURL URLWithString:kSuccessURLString];

// Starts a loopback HTTP redirect listener to receive the code.  This needs to be started first,
// as the exact redirect URI (including port) must be passed in the authorization request.
_redirectHTTPHandler = [[OIDRedirectHTTPHandler alloc] initWithSuccessURL:successURL];
NSURL *redirectURI = [_redirectHTTPHandler startHTTPListener:nil];

Then, initiate the authorization request. By using the authStateByPresentingAuthorizationRequest convenience method, the token exchange will be performed automatically, and everything will be protected with PKCE (if the server supports it). By assigning the return value to the OIDRedirectHTTPHandler's currentAuthorizationFlow, the authorization will continue automatically once the user makes their choice:

// builds authentication request
OIDAuthorizationRequest *request =
    [[OIDAuthorizationRequest alloc] initWithConfiguration:configuration
                                                  clientId:kClientID
                                              clientSecret:kClientSecret
                                                    scopes:@[ OIDScopeOpenID ]
                                               redirectURL:redirectURI
                                              responseType:OIDResponseTypeCode
                                      additionalParameters:nil];
// performs authentication request
__weak __typeof(self) weakSelf = self;
_redirectHTTPHandler.currentAuthorizationFlow =
    [OIDAuthState authStateByPresentingAuthorizationRequest:request
                        callback:^(OIDAuthState *_Nullable authState,
                                   NSError *_Nullable error) {
  // Brings this app to the foreground.
  [[NSRunningApplication currentApplication]
      activateWithOptions:(NSApplicationActivateAllWindows |
                           NSApplicationActivateIgnoringOtherApps)];

  // Processes the authorization response.
  if (authState) {
    NSLog(@"Got authorization tokens. Access token: %@",
          authState.lastTokenResponse.accessToken);
  } else {
    NSLog(@"Authorization error: %@", error.localizedDescription);
  }
  [weakSelf setAuthState:authState];
}];

Making API Calls

AppAuth gives you the raw token information, if you need it. However, we recommend that users of the OIDAuthState convenience wrapper use the provided performActionWithFreshTokens: method to perform their API calls to avoid needing to worry about token freshness:

Objective-C

[_authState performActionWithFreshTokens:^(NSString *_Nonnull accessToken,
                                           NSString *_Nonnull idToken,
                                           NSError *_Nullable error) {
  if (error) {
    NSLog(@"Error fetching fresh tokens: %@", [error localizedDescription]);
    return;
  }

  // perform your API request using the tokens
}];

Swift

let userinfoEndpoint = URL(string:"https://openidconnect.googleapis.com/v1/userinfo")!
self.authState?.performAction() { (accessToken, idToken, error) in

  if error != nil  {
    print("Error fetching fresh tokens: \(error?.localizedDescription ?? "Unknown error")")
    return
  }
  guard let accessToken = accessToken else {
    return
  }

  // Add Bearer token to request
  var urlRequest = URLRequest(url: userinfoEndpoint)
  urlRequest.allHTTPHeaderFields = ["Authorization": "Bearer \(accessToken)"]

  // Perform request...
}

Custom User-Agents

Each OAuth flow involves presenting an external user-agent to the user, that allows them to interact with the OAuth authorization server. Typical examples of a user-agent are the user's browser, or an in-app browser tab incarnation like ASWebAuthenticationSession on iOS.

AppAuth ships with several implementations of an external user-agent out of the box, including defaults for iOS and macOS suitable for most cases. The default user-agents typically share persistent cookies with the system default browser, to improve the chance that the user doesn't need to sign-in all over again.

It is possible to change the user-agent that AppAuth uses, and even write your own - all without needing to fork the library.

All implementations of the external user-agent, be they included or created by you need to conform to the OIDExternalUserAgent protocol.

Instances of the OIDExternalUserAgentare passed into OIDAuthState.authStateByPresentingAuthorizationRequest:externalUserAgent:callback and/or OIDAuthorizationService.presentAuthorizationRequest:externalUserAgent:callback: rather than using the platform-specific convenience methods (which use the default user-agents for their respective platforms), like OIDAuthState.authStateByPresentingAuthorizationRequest:presentingViewController:callback:.

Popular use-cases for writing your own user-agent implementation include needing to style the user-agent in ways not supported by AppAuth, and implementing a fully custom flow with your own business logic. You can take one of the existing implementations as a starting point to copy, rename, and customize to your needs.

Custom Browser User-Agent

AppAuth for iOS includes a few extra user-agent implementations which you can try, or use as a reference for your own implementation. One of them, OIDExternalUserAgentIOSCustomBrowser enables you to use a different browser for authentication, like Chrome for iOS or Firefox for iOS.

Here's how to configure AppAuth to use a custom browser using the OIDExternalUserAgentIOSCustomBrowser user agent:

First, add the following array to your Info.plist (in XCode, right click -> Open As -> Source Code)

	<key>LSApplicationQueriesSchemes</key>
	<array>
		<string>googlechromes</string>
		<string>opera-https</string>
		<string>firefox</string>
	</array>

This is required so that AppAuth can test for the browser and open the app store if it's not installed (the default behavior of this user-agent). You only need to include the URL scheme of the actual browser you intend to use.

Objective-C

// performs authentication request
AppDelegate *appDelegate =
    (AppDelegate *)[UIApplication sharedApplication].delegate;
id<OIDExternalUserAgent> userAgent =
    [OIDExternalUserAgentIOSCustomBrowser CustomBrowserChrome];
appDelegate.currentAuthorizationFlow =
    [OIDAuthState authStateByPresentingAuthorizationRequest:request
        externalUserAgent:self
                 callback:^(OIDAuthState *_Nullable authState,
                                   NSError *_Nullable error) {
  if (authState) {
    NSLog(@"Got authorization tokens. Access token: %@",
          authState.lastTokenResponse.accessToken);
    [self setAuthState:authState];
  } else {
    NSLog(@"Authorization error: %@", [error localizedDescription]);
    [self setAuthState:nil];
  }
}];

That's it! With those two changes (which you can try on the included sample), AppAuth will use Chrome iOS for the authorization request (and open Chrome in the App Store if it's not installed).

⚠️Note: the OIDExternalUserAgentIOSCustomBrowser user-agent is not intended for consumer apps. It is designed for advanced enterprise use-cases where the app developers have greater control over the operating environment and have special requirements that require a custom browser like Chrome.

You don't need to stop with the included external user agents either! Since the OIDExternalUserAgent protocol is part of AppAuth's public API, you can implement your own versions of it. In the above example, userAgent = [OIDExternalUserAgentIOSCustomBrowser CustomBrowserChrome] would be replaced with an instantiation of your user-agent implementation.

API Documentation

Browse the API documentation.

Included Samples

Sample apps that explore core AppAuth features are available for iOS and macOS; follow the instructions in Examples/README.md to get started.